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334 Cards in this Set
- Front
- Back
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Central Nervous System (CNS)
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The brain and spinal cord, which contain control centers responsible for processing and integrating sensory information, planning and coordinating responses to stimuli, and providing short-term control over the activities of other systems
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Peripheral Nervous System (PNS)
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Neural tissue outside the CNS whose function is to link the CNS with sense organs and other systems
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Autonomic Nervous System (ANS)
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Components of the CNS and PNS that are concerned with the control of visceral functions.
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Nucleus
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A CNS center with discrete anatomical boundaries
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Center
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A group of neuron cell bodies in the CNS that share a common function
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Tract
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A bundle of axons with the CNS that share a common origin, destination, and function
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Column
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A group of tracts found within a specific region of the spinal cord
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Pathways
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Centers and tracts that connect the brain with other organs and systems in the body
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Ganglia
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An anatomically distinct collection of sensory or motor neuron cell bodies within the PNS
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Nerve
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A bundle of axons in the PNS
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Gray Matter
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Neural tissue dominated by neuron cell bodies
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White Matter
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Neural tissue dominated by myelinated axons
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Neural Cortex
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A layer of gray matter at the surface of the brain
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Neuron
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The basic functional unit of the nervous system; highly specialized cell; a nerve cell
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Sensory Neuron
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A neuron whose axon carries sensory information from the PNS towards the CNS
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Motor Neuron
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A neuron whose axon carries motor commands from the CNS toward effectors in the PNS
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Soma
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A cell body of a neuron
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Dendrites
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Neuronal processes that are specialized to respond to specific stimuli in the extracellular environment
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Axon
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A long, slender cytoplasmic process of a neuron; axons are capable of conducting nerve impulses (action potentials)
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Myelin
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A membranous wrapping, produced by glial cells, that coats axons and increases the speed of action potential propagation; axons coated with myelin are said to be myelinated
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Neurolgia or Glial Cells
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Supporting cells that interact with neurons and regulate the extracellular environment, provide defense against pathogens, and perform repairs within neural tissue
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Receptor
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A specialized cell or dendrite, or organ that responds to specific stimuli in the extracellular environment and whose stimulation alters the level of activity in a sensory neuron
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Effector
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A muscle, gland, or other specialized cell or organ that responds to neural stimulation by altering its activity and producing a specific effect
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Reflex
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A rapid, stereotyped response to a specific stimulus
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Somatic
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Pertaining to the control of skeletal muscle activity (somatic motor) or sensory information from skeleton muscles, tendons, and joints (somatic sensory)
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Visceral
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Pertaining to the control of functions, such a digestion, circulation, etc. (visceral motor) or sensory information from visceral organs (visceral sensory)
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Voluntary
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Under direct conscious control
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Involuntary
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Not under direct conscious control
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Subconscious
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PErtaining to centers in the brain that operate outside a person's conscious awareness
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Action potentials
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Sudden, transient changes in the membrane potential that are propagated along the surface of an axon or sarcolemma.
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What two systems adjust and control other systems of the body?
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1. Nervous system
2. Endocrine system |
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What is the difference between the nervous system and endocrine system responses?
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Nervous system: relatively swift (few milliseconds) but brief responses (disappear after neural activity ceases) to stimuli by temporarily modifying the activities of other organ systems
Endocrine System: responses typically slower to develop than neural responses but often last much longer - even as long as hours, days or years (e.g. growth and development) |
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All of the neural tissue in the body is part of what system?
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The nervous system
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What are the tow anatomical divisions of the nervous system?
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1. Central nervous system (CNS)
2. Peripheral nervous system (PNS) |
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What does the central nervous system consist of?
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Brain and spinal cord
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What is the function of the CNS?
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1. Integrate and process sensory input
2. Coordinate motor output 3. Seat of higher function such as intelligence, memory, learning and emotion |
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Early in development, the CNS begins as a mass of neural tissue organized into a hollow tube (True/False)
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True
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What is the narrow cavity within the spinal cord called?
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Central canal
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What are the cavities within the brain called?
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ventricles
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What fills the central canal and ventricles and surrounds the CNS?
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Cerebrospinal fluid (CSF)
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What does the peripheral nervous system (PNS) consist of?
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All the neural tissue outside the CNS.
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What is the function of the PNS?
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1. Provide sensory information to CNS
2. Carry motor commands from CNS to peripheral tissues and systems. |
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What are the two divisions of the PNS? What are their functions?
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1. Afferent division: bring sensory information to CNS
2. Efferent division: carries motor commands to muscles and glands |
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The afferent division begins at?
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Receptors
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A receptor may come in what forms?
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1. Dendrite (a sensory process of the neuron)
2. A specialized cell or cluster of cells 3. A complex sense organ (e.g. eye) |
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What is the function of receptors?
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Monitor specific characteristics of the environment
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Where does the efferent division begin and end?
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Begin: CNS
End: Effector |
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What is an effector?
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A muscle cell, gland cell, or another cell specialized to perform specific functions.
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What are the two components of efferent and afferent divisions of the PNS?
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1. Somatic
2. Visceral |
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What tissues/organs do the somatic sensory receptors monitor?
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1. Skeletal muscles
2. Joints 3. Skin |
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What tissues/organs do the visceral sensory receptors monitor?
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1. Smooth muscle
2. Cardiac muscle 3. Glands 4. Respiratory and digestive organs among others |
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What are the two divisions of the Efferent division of the PNS?
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1. Somatic nervous system (SNS)
2. Autonomic nervous system (ANS) |
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What tissues/organs do the following efferent divisions control?
1. Somatic nervous system (SNS) 2. Autonomic nervous system (ANS) |
1. Skeletal muscle contractions
2. Smooth muscle, cardiac muscle, and glandular activity |
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The somatic nervous system activities are alway voluntary (True/False)
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False. They may be voluntary or involuntary.
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What is the difference between voluntary and involuntary contractions?
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Voluntary: under conscious control e.g. picking up glass of water
Involuntary: directed outside our awareness e.g. withdrawing hand from hot stove |
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The activities of the autonomic nervous system are usually outside of our awareness or control (True/False)
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True
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What is another name for the autonomic nervous system?
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Visceral motor system
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What provides physical protection and support to the organs of the CNS and PNS?
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Connective tissue
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What performs the varied and essential functions of the nervous system?
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Individual neurons
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What symptoms generally accompany a wide variety of neurological disorders?
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1. Headache
2. Muscle weakness 3. Paresthesias |
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What are the two types of headaches and what are their characteristics?
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1. Tension-type headache: Moderate pain, poorly localized, due to muscle tension like tight neck muscles
2. Migraine headache: Throbbing, unilateral severe pain, light sensitivity, nausea, vomiting; of neurological or cardiovascular origins. |
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What are other causes of headaches besides muscle tension and migraines?
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1. CNS disorder, such as viral or bacterial infections or brain tumors
2. Trauma, such as a blow to the head 3. Cardiovascular disorders, such as a stroke 4. Metabolic disturbances, such as low blood sugar |
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What neurological disorders could cause muscle weakness?
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1. Demyelinating disorders
2. Neuromuscular synapse dysfunction 3. Peripheral nerve damage |
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What are paresthesias?
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Loss of feeling, numbness, or tingling sensations
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Damage to what tissues can cause paresthesias?
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1. Sensory nerve (cranial or spinal)
2. Sensory pathways in the central nervous system (CNS) |
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Paresthesias are permanent (True/False)
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False. May be temporary (pressure palsy) or permanent (spinal cord damage)
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What are the two cell types of the neural tissue? What are their functions?
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1. Neurons: transfer and process information in the nervous system
2. Neuroglia (supporting cells): isolate the neurons, provide a supporting framework for the neural tissue, help maintain the intercellular environment, and act as phagocytes |
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What are the main components of a neuron?
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1. Cell body (soma)
2. Dendrites 3. Axon |
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What is the region around the nucleus in the neuron cell body called?
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Perikaryon
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What are the fine processes on each branch of dendrite called? What is their significance?
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Dendritic spines.
1. Neurons receive information from other neurons at the dendritic spines 2. They may represent 80-90% of the neuron's total surface area |
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What is the junction the axon ends at called? What is their significance?
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Synaptic terminals. The neuron communicates with another cell at synaptic terminals.
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What is the significance of the soma in neurons?
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Contains the organelles responsible for:
1. Energy production 2. Biosynthesis of organic molecules, such as enzymes |
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1. How many neuroglia are present in the human body?
2. How many neurons are present in the brain? |
1. 100 billion (roughly five times the number of neurons)
2. 20 billion |
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What is another name for neuroglia?
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Glial cells
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Glial cells are larger than neurons (True/False)
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False.
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Both neurons and neuroglia can divide (True/False)
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False. Only neuroglia retain the ability to divide.
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Glial cells make up what volume of the nervous system?
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Roughly half.
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What is the primary reason for organization differences between the CNS and PNS?
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Differences in the glial cell populations.
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The greatest variety of glial cells is found within the:
a. CNS b. PNS |
a. CNS
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What are the types of glial cells in the CNS and PNS?
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CNS:
1. Astrocytes 2. Oligodendrocytes 3. Microglia 4. Ependymal cells PNS 1. Satellite Cells 2. Schwann Cells |
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What are the the largest and most numerous glial cells?
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Astrocytes
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What are the functions of the astrocytes?
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1. Controlling the interstitial environment
2. Maintaining the blood-brain barrier 3. Creating a three-dimensional structural framework for the CNS 4. Performing repairs in damaged neural tissue 5. Guiding neuron development (embryonic) |
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Astrocytes have a large number of cytoplasmic processes (True/False)
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True
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What is the function of the large number of cytoplasmic processes in astrocytes?
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Increase the surface area of the cell, which facilitates the exchange of ions and other molecules with the extracellular fluid within the CNS
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Why is the exchange of ions and other molecules between the astrocytes and extracellular fluids significant?
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Enables astrocytes to control the chemical content of the interstitial environment of the CNS.
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How do astrocytes isolate neurons from changes in the chemical composition of the interstitial space within the CNS?
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The cytoplasmic processes of the astrocytes contact neuronal surfaces, often enclosing the entire neuron.
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Why must neural tissue be physically and biochemically isolated from the general circulation?
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Because hormones or other chemicals normally present in the blood could have disruptive effects on neuron function.
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What is responsible for the blood-brain barrier that isolates the CNS from the general circulation?
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The restricted permeability characteristics of the endothelial cells lining CNS capillaries that control the chemical exchange between blood and interstitial fluid,
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How do astrocytes contribute to the blood-brain barrier?
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Many of the cytoplasmic processes of astrocytes, termed astrocyte "feet," contact the surface and cover most of the surface of the capillaries within the central nervous system. Chemicals secreted by astrocytes are essential for the maintenance of the blood-brain barrier.
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What cytoplasmic blanket created by astrocytes around capillaries with the CNS is interrupted where?
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Where other glial cells contact the capillary walls.
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What component of the astrocytes form a structural framework that support the neurons of the brain and spinal cord?
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Astrocytes are packed with microfilaments that extend across the breadth of the cell
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What cells
1. make structural repairs that stabilize CNS tissue after damage 2. produce scar tissue at an injury site in the CNS to prevent further injury? |
Astrocytes
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What are chemicals secreted by astrocytes during embryonic development that direct the growth and interconnection of developing neurons called?
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Neurotropic factors
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How are oligodendrocytes different from astrocytes?
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Oligodendrocytes have:
1. smaller cell bodies 2. fewer and shorter cytoplasmic processes. |
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What glial cell in the CNS is responsible for the myelin sheath around axons?
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Oligodendrocytes
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What do cytoplasmic processes of oligodendrocytes usually contact?
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1. Axons
2. Cell bodies of neurons |
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What are the two functions of oligodendrocytes?
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1. Tie clusters of axons together
2. Wrap axons in myelin |
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Myelin has insulating properties (True/False)
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True
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Myelin is single layered sheath around the axon (True/False)
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False. It is a multilayered sheath.
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What constitutes the myelin sheath of axons in the CNS
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A flattened pad of plasmalemma at the tip of a oligodendrocyte cytoplasmic process that creates a multilayered membrane sheath around the axon.
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What is kind of organic compound is myelin made of?
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Phospholipids (primarily)
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The axon with a myelin sheath around it is said to be?
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Myelinated
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What is the significance of myelin?
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Improves the speed at which an action potential, or nerve impulse, is conducted along an axon.
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All axons in the CNS are myelinated (True/False)
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False
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One oligodendrocyte forms the myelin sheath along the entire length of a myelinated axon (True/False)
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False. Many oligodendrocytes cooperate in the formation of the myelin sheath along the entire length of a myelinated axon.
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What are the areas on the axon wrapped in myelin sheath called?
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Internodes
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What are the small gaps between the myelin sheaths on the axon called?
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Myelin sheath gaps or nodes of Ranvier
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What is responsible for the white glossy appearance of myelinated axons?
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Lipid content of myelin
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What constitute the white matter of the CNS?
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Regions dominated by myelinated axons
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What constitutes the gray matter of the CNS?
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Regions dominated by neuron cell bodies, dendrites, and unmyelinated axons
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What are the smallest of the glial cells?
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Microglia
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The cytoplasmic process of microglia have many fine branches (True/False)
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True
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What stem cells are microglia derived from during embryonic development?
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Mesodermal stem cells
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The mesodermal stem cell also produce what other types of cells?
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1. Tissue macrophages
22. Monocytes of the blood |
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What is the function of the microglia?
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They are phagocytic cells of the CNS, engulfing debris, waste products and pathogens.
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When does the number of microglia increase in the CNS?
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In times of infection or injury
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What percentage of CNS glial cells are microglia when there is no infection or damage in the CNS?
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5%. This percentage increases dramatically in times of infection or injury.
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What is the cellular layer that lines the ventricles of brain and the central canal of the spinal cord called?
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Ependyma
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What is the function of the cerebrospinal fluid?
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1. Provides protective cushion to brain and spinal cord
2. Transports dissolved gases, nutrients, wastes and other materials. |
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What shape are the ependymal cells?
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Cuboidal to columnar
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What do the slender processes (branch extensively) of the ependymal cells contact?
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Glial cells in surrounding neural tissue
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Ependymal cells may act a receptors that monitor the composition of the CFS (True/False)
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True.
Note: Experimental evidence suggests this. |
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The free surfaces of the ependymal cells may be covered with?
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Cilia
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What is the difference between the cilia on ependymal cells in development and early childhood and an adult
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Development and early childhood: free surfaces of most ependymal cells are covered with cilia
Adult: cilia only persists on ependymal cells that line the ventricles of the brain, but the ependyma elsewhere only has scattered microvilli |
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What may be a function of ciliated ependymal cells?
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Circulation of CSF
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What is the function of specialized ependymal cells that line some parts of the ventricles of the brain (choroid plexus)?
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Secretion of cerebrospinal fluid
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What are the clusters of neuron cell bodies in the PNS called?
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Ganglia
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What forms nerves?
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Axons bundle together and wrapped in connective tissue.
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What insulates the neuron cell bodies and axons in the PNS from their surroundings?
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Processes of glial cells
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What glial cells surround neuron cell bodies in peripheral ganglia?
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Satellite cells
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What is the function of satellite cells?
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1. Regulate the exchange of nutrients and waste products between the neuron cell body and the extracellular fluid
2. Isolate neuron from stimuli other than those provided at synapses |
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What glial cells cover peripheral axons?
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Schwann cells
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Only myelinated peripheral axons are covered by Schwann cells (True/False)
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False. Both myelinated and unmyelinated peripheral axons are covered by Schwann cells.
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What is another name for Schwann cells
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Neurlemmocytes
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What is the plasmalemma of an axon called?
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Axolemma
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What is the superficial cytoplasmic covering of peripheral axons provided by Schwann cells called?
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Neurolemma
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Both Schwann cells and oligodendrocytes myelinate only portions of one axon (True/False)
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False. Schwann cells only myelinate a portion of one axon whereas oligodendrocytes can myelinate a portion of several axons.
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What length of an axon does a Schwann cell myelinate?
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1 mm
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Myelinated axons of both PNS and CNS have myelin sheath gaps and internodes (True/False)
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True
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The function of myelin in CNS and PNS axons differ (True/False)
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False. The presence of myelin in both division increase the rate of nerve impulse conduction.
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Are unmyelinated peripheral axons enclosed by processes of Schwann cells?
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Yes. But the relationship is simple and no myelin forms.
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1. Processes of a single Schwann cell surround only one unmyelinated axon (True/False)
1. Processes of a single Schwann cell surround only one myelinated axon (True/False) |
1. False. It may surround several different unmyelinated axons.
2. True. |
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What are the two anatomical subdivisions of the nervous system?
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1. Central nervous system (CNS)
2. Peripheral nervous system (PNS) |
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What two terms are used to refer to the supporting cells in the neural tissue?
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Glial cells or neuroglia
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Specifically, what glial cells help maintain the blood-brain barrier?
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Astrocytes
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What is the name of the membranous coating formed around axons by oligodendrocytes?
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Myelin
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Identify the cells in the peripheral nervous system that form a covering around axons.
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Schwann cells
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The cell body of a neuron has a small nucleus with a indistinct nucleolus (True/False)
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False. IT has a larger nucleus with a prominent nucleolus.
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What is the cytoskeleton of the perikaryon composed of?
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1. Neurofilaments
2. Neurotubules |
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What are bundle of neurofilaments in the perikaryon called?
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Neurofibrils
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Neurofibrils extend into dendrites and the axon (True/False)
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True
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What is significance of perikaryon?
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Contains organelles that provide energy and perform biosynthesis activities.
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What are some organelles of the perikaryon?
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1. Mitochondria
2. Ribosomes (free and fixed) 3. Rough endoplasmic reticulum (RER) |
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What is the function of:
1. Mitochondria 2. RER and Ribosomes |
1. Mitochondria: generate ATP to meet the high energy demands of an active neuron
2. Ribosomes and RER: synthesize peptides and proteins |
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What are groups of ribosomes (ribosomal clusters) in the neuron called?
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Chromatophilic substance or Nissl bodies
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What component of the neuron cell body accounts for the gray color of the gray matter of the brain and spinal cord?
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Chromatophilic substance (Nissl bodies)
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Most neurons lack a centrosome (True/False)
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True
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In cells other than neurons, what is the function of centrosomes?
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The centrioles of the centrosome form the spindle fibers that move chromosome during cell division.
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When do neurons lose their centrioles?
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During differentiation
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What is the significance of the absence of centrioles in neurons?
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It makes neurons incapable of cell division and if they are lost to injury or disease they can not be replaced.
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What can change the permeability of the neurolemma of the dendrites and cell body?
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Chemical, mechanical or electrical stimuli.
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One of the primary functions of glial cells is to limit the number and types of stimuli affecting individual neurons (True/False)
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True
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Where do glial cell processes not cover the neuron?
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1. At synaptic terminals
2. Where dendrites function as sensory receptors. |
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Dendrites function as sensory receptors monitor conditions in the intracellular environment (True/False)
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False. They monitor conditions in the extracellular environment.
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What happens to transmembrane potential when the neuron is exposed to an appropriate stimuli?
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It changes
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What is generated at the axons when when the neuron is exposed to an appropriate stimuli?
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Action potential
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What is transmembrane potential?
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Property resulting from unequal distribution of ions across the neurolemma.
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What is an axon?
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A long cytoplasmic process of a neuron that is capable of propagating an action potential.
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In a multipolar neuron what connects the initial segment of the axon to the soma?
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Axon hillock
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Axon hillocks are found in all neurons (True/False)
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False. Only in multipolar neurons.
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What is cytoplasm of the axon called?
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Axoplasm
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What are the contents of the axoplasm?
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1. Neurofibrils
2. Neurtubules 3. Small vesicles 4. Lysosomes 5. Mitochondria 6. Enzymes |
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An axon may branch along its length (True/False)
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True
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What are side branches of an axon called?
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Collaterals
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What are the series of fine terminal extensions of the main branch and collateral of an axon called?
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Terminal arborizations
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What is another name for terminal arborizations?
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Telodendria
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What is the junction of a neuron with another neuron or effector called?
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Synaptic terminal
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The terminal arborizations end in a?
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Synaptic terminal
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What is the movement of organelles, nutrients, synthesized molecules, and waste products between the cell body and the synaptic terminals called?
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Axoplasmic transport
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Axoplasmic transport is a complex process consume energy and relies on movement along the neurofibrils of the axon and it branches (True/False)
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True
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What is the specialized site where the neuron communicates with another cell called?
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Synapse
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The structure of the synapse is the same regardless of the type of postsynaptic cell (True/False)
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False. It varies with the type of postsynaptic cell.
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What is the synaptic terminal called in a synapse between two neurons?
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Terminal bouton or synaptic knob
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The synaptic terminals of a neuromuscular synapse (neuromuscular junction) are also called terminal boutons (True/False)
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Fale
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What is a neuromuscular synapse?
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Where a neuron contacts a skeletal muscle fiber.
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A neuromuscular synaptic terminal is more complex that a terminal bouton (True/False)
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True
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What are chemicals released during synaptic communication called?
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Neurotransmitters
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What triggers release of neurotransmitter?
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Arrival of a nerve impulse
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What is the structural classification of neurons?
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1. Anaxonic neurons
2. Bipolar neurons 3. Pseudounipolar neurons 4. Multipolar neurons |
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What is the structural classification of neurons based on?
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Number of processes that project from the cell body
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What is the distinguishing anatomical feature of anaxonic neurons?
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There are no anatomical clues to distinguish dendrites from axons.
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Anaxonic neurons are small (True/False)
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True
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Anaxonic neurons are found in the PNS (True/False)
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False. They are only found in the CNS and special sense organs.
Note: Their function is poorly understood |
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What is the distinguishing anatomical feature of bipolar neurons?
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They have a number of fine dendrites that fuse to form a single dendrite. The cell body lies between this dendrite and a single axon.
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There are numerous bipolar neurons in the nervous system (True/False)
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False. They are rare.
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What is the function of bipolar neurons?
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They play an important role in relaying sensory information concerning sight, smell, and hearing.
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Which of the following neurons have myelinated or unmyelinated axons?
1. Bipolar 2. Pseudounipolar 3. Multipolar |
1. Bipolar: unmyelinated
2. Pseudounipolar: may be myelinated 3. Multipolar: myelinated |
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What is the distinguishing anatomical feature of pseudounipolar neurons?
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They have continuous dendritic and axonal processes, and the cell body lies off to one side.
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Where does the initial segment of axons lie in pseudounipolar neurons?
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At the base of the dendritic branches (See Fig 13.10 and pg. 357)
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What is the distinguishing anatomical feature of pseudounipolar neurons?
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They have several dendrites and a single axon that may have one or more branches.
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What are the most common type of neurons in the CNS?
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Multipolar neurons
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All the motor neurons that control skeletal muscles are multipolar neurons (True/False)
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True
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What are the only type of neuron that can have axonal branches (collaterals)?
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Multipolar neurons
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What are the functional classifications of neurons?
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1. Sensory neurons
2. Motor neurons 3. Interneurons |
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Sensory neurons are mostly what type of structural neuron?
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Pseudounipolar neurons
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Where do the cell bodies of the sensory neurons lie?
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In ganglia ( peripheral sensory ganglia outside the CNS)
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Sensory neurons form what division of the peripheral nervous system?
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Afferent division
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What is the function of sensory neurons?
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To deliver information to the CNS
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What are axons of the sensory neurons called?
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Afferent fibers
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What do axons of sensory neurons (afferent fibers) extend between?
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A sensory receptor and the spinal cord or brain
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Sensory neurons collect information concerning only the external environment (True/False)
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False. They collect information about both the internal and external environment.
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What is the approximate number of sensory neurons in the human body?
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10 million
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What are the two types of sensory neurons and what are their functions?
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Somatic sensory neurons: transmit information about the outside world and our position within it.
Visceral sensory neurons: transmit information about internal conditions and the status of other organ systems. |
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Receptors are special cells monitored by sensory neurons. Sensory neurons themselves can not be receptors (True/False)
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False. Receptor may be either the processes of specialized sensory neurons or cells monitored by sensory neurons.
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What are the broad categorizations of receptors? What are their functions
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1. Exteroceptors: provide information about external environment
2. Proprioceptors: monitor the position and movement of skeletal muscles and joints 3. Interoceptors: monitor the digestive, respiratory, cardiovascular, urinary and reproductive systems. |
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Which kind of receptor provide the following sensations?
1. Touch, temperature, pressure and the more complex special senses of sight, smell, and hearing 2. Deep pressure and pain as well as taste (special sense) |
1. Exteroceptors
2. Interoceptors |
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1. Data from exteroceptors and proprioceptors is carried by what kind of functional neurons?
2. Data from interoceptors is carried by what kind of functional neurons? |
1. Somatic sensory neurons
2. Visceral sensory neurons |
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What kind of structural neurons make up the motor neurons?
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Multipolar neurons
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What is the function of a motor neuron?
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Modifies the activity of a peripheral tissue, organ or organ system.
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Axons traveling away from the CNS are called?
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Efferent fibers
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What are the two efferent divisions of the PNS? What do they innervate?
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1. Somatic nervous system (SNS): include all of the somatic motor neurons that innervate skeletal muscles
2. Autonomic nervous system (ANS): include all visceral motor neurons that innervate peripheral effectors other than skeletal muscles |
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Where do the cell bodies of the somatic motor neurons lie and where do their axons extend to?
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The cell bodies lie inside the CNS and their axons extend to the neuromuscular synapses tat control skeletal muscles.
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Most of the activities of the SNS are consciously controlled (True/False)
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True
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How are the visceral motor neurons organized?
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There are two groups. One group has cell bodies inside the CNS and other had cell bodies in peripheral ganglia. The neurons inside the CNS control the neurons in the peripheral ganglia, and these neurons in turn control the peripheral effectors.
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What are the axons of the following visceral motor neurons called?
1. Axons extending from the CNS to a ganglion 2. Axons extending from ganglion cells to the peripheral effectors. |
1. Preganglionic fibers
2. Postganglionic fibers |
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What clearly distinguishes the autonomic (visceral motor) system from the somatic motor system?
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Arrangement of neurons: single neuron from CNS to effector (SNS) vs. two neurons from CNS to effector (ANS)
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We do not have conscious control over the activities of the ANS (True/False)
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True
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Where are interneurons located?
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Between sensory and motor neurons and entirely within the brain and spinal cord.
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What are most numerous functionally classified neurons?
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Interneurons.
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What is the function of interneurons?
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1. Analysis of sensory input
2. Coordination of motor output |
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The number of neurons involved in the response to a stimuli increases in proportion to what?
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The complexity of the response to a given stimuli
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What are the classification of interneurons?
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1. Excitatory
2. Inhibitory Note: on the basis of their effects on the postsynaptic membranes of other neurons. |
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What type of glial cell would you expect to find in large numbers in brain tissue from a person suffering from a CNS infection?
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Microglial cells
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Examination of a tissue ample show pseudounipolar neurons. Are these most likely to be sensory neurons or motor neurons?
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Sensory neurons
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What are some causes of demyelination disorder?
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1. Heavy-metal poisoning
2. Bacterial toxins 3. Degenerative disorders |
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What is the common symptom of demyelination disorders?
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Destruction of myelinated axons in the CNS and the PNS.
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Name a demyelination disorder cause by bacterial toxins?
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Diphtheria. Starts out as bacterial infection of respiratory tract. Bacteria produce toxins that damage Schwann cells and destroys the myelin sheaths in the PNS.
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Name a degenerative disorder that causes demyelination?
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Multiple sclerosis (MS)
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Axons in what regions are affected by multiple sclerosis (MS)?
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1. Optic Nerve
2. Brain 3. Spinal cord |
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Diphtheria toxins destroy myelin in the CNS (True/False)
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False. Only in the PNS.
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A neuron has a very limited ability to recover from injury (True/False)
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True
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What are causes of neuron injury?
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1. Restricted oxygen or nutrient supply
2. Mechanical pressure |
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What happens to a neuron if oxygen or nutrient supply remains restricted of mechanical pressure continues?
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Neuron will be permanently damage or killed
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In the PNS, what cells participate in the repair of damaged nerves?
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Schwann cells
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What is the process of deterioration of axon distal to the injury site and phagocytization of debris my macrophages called?
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Wallerian degeneration
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What is the role of Schwann cells in damaged nerve repair?
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1. The Schwann cells in the area divide and form a solid cellular cord that follows the path of the original axon.
2. They release growth factors to promote axonal regrowth. |
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What is the difference between axonal regrowth when the axon is cut vs. when it is crushed or torn?
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Cut: new axons begin to emerge from the proximal end of the cut within a few hours
Crushed or torn: the proximal end of the damaged axon will die and regress for one centimeter or more, and the sprouting of new axonal segments may be delayed for one or more weeks. |
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As the damaged neuron continues to recover, its axons grow into the injury site and the Schwann cells wrap around it (True/False)
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True
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What happens if a damaged neuron stops growing or wanders off in some new direction?
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Normal function is not restored
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Axons of damaged neuron alway grow alongside the cord of Schwann cells (True/False)
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False. They may or they may wander off in a new direction.
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When us a growing axon of a damaged neuron mostly likely to arrive at its appropriate destination?
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If the damaged proximal and distal stumps remain in contact after the injury.
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When an entire peripheral nerve is damaged, only a relatively small number of axons will reestablish normal synaptic contact. What is the result of this?
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Nerve function is permanently impaired
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Nerve regeneration within the CNS is limited (True/False)
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True
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What makes nerve generation within the CNS more complicated?
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1. Many more axons are likely to be involved
2. Astrocytes produce scar tissue that can prevent axon regrowth across the damaged area 3. Astrocytes release chemicals that block the regrowth of axons |
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What is excitability of plasmalemma?
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The ability of a plasmalemma to conduct electrical impulses.
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Membranes of what kind of muscles are excitable?
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1. Plasmalemma of skeletal muscle fibers, cardiac muscle cells, some gland cell
2. Axolemma of most neurons |
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What structural types of neurons always have excitable axolemmas?
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1. Multipolar
2. Pseudounipolar |
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An action potential is an electric impulse (True/False)
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True
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What is threshold
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The level of stimulation of plasmalemma needed to generate an action potential.
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What happens when threshold level is reached?
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The membrane permeability to sodium and potassium ions changes.
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What constitutes an action potential?
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The ion movement due to permeability change of membrane in response to a stimulus that produces a sudden change in transmembrane potential.
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The plasmalemma permeability change due to a stimulus are permanent (True/False)
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They are temporary.
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How does the change in ion concentration due to plasmalemma permeability change help conduct action potential along the membrane surface?
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Change in ion distribution almost immediately triggers changes in permeability of adjacent portions of the plasmalemma. In this way, the action potential is conducted along the membrane surface.
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1. Where do action potential begin in a skeletal muscle fiber?
2. Are they confined a specific area of the sarcolemma? |
1. Action potential begin as the neuromuscular synapse.
2. They sweep across the entire surface of the sarcolemma. |
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What are nerve impulses?
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Action potential traveling along axons
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What does the rate of nerve impulse conduction depend on?
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The properties of the axon:
1. The presence or absence of myelin sheath 2. The diameter of the axon |
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Myelin axons conduct impulses __________ times faster than an unmyelinated axon
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Five to seven times
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How does nerve impulse conduction vary with axon diameter?
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The larger the diameter, the more rapidly the impulse will be conducted.
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1. What speeds can nerve impulses read in 4 to 20 micrometer diameter myelinated axons?
2. What speeds can nerve impulses read in 2 micrometer diameter unmyelinated axons? |
1. 140 m/s (300 mph)
2. 1 m/s (2 mph) |
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What effect would cutting the axon have on transmitting the action potential?
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Would prevent transmission of the nerve impulse along the length of the axon.
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Two axons are tested for conduction velocities. One conducts action potential at 50 m/s, the other at 1 m/s. Which axon is myelinated?
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Axon conducting at 50 m/s
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Define excitability.
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Ability of cell membrane to conduct electrical impulses.
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What term is used to identify changes in transmembrane potential?
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Action potential
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What are the three structurally classified synapses between neurons?
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1. Axodendritic: synaptic terminal + dendrite
2. Axosomatic: synaptic terminal + neuron cell body 3. Axoaxonic: synaptic terminal + axon |
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What is a neuroeffector junction?
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A synapse between a neuron and another cell type
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At a synaptic terminal, a nerve impulse triggers events at a synapse that transfers the information either to another neuron or to an effector cell (True/False)
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True
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How are synapses classified based on what substance are used for synaptic communication?
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1. Vesicular synapses: passage of neurotransmitter between cells
2. Nonvesicular synapses: ion flow between cells |
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What is another name for vesicular synapses?
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Chemical synapses
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Which are more abundant: vesicular or nonvesicular synapses?
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Vesicular synapses
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All synapses between neurons are vesicular (True/False)
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False. Most are, but not all.
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All synapses between neurons and peripheral effectors are vesicular (True/False)
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True
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Where is the neurotransmitter released and where does it bind in a synapse between two neurons?
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Released: presynaptic membrane of a terminal bouton
Binds: receptor proteins on postsynaptic membranes |
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What happens when neurotransmitter bind to receptor proteins on a neuron?
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Triggers a transient change in the transmembrane potential of the receptive cell.
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In synapses between neurons communication occurs in one direction only since only the presynaptic neurons release neurotransmitters (True/False)
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True
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What neurotransmitter is released at a somatic neuromuscular synapse?
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Acetylcholine (ACh)
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There is only one type of neurotransmitter (True/False)
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False. More than 50 different ones have been identified but ACh is the best known.
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ACh is only released at somatic neuromuscular synapses (True/False)
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False. It is also released at many vesicular synapses in the CNS and PNS.
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What is the sequence of events leading to generation of action potential in a postsynaptic neuron?
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1. Arrival of action potential at terminal bouton triggering release of neurotransmitters
2. Neurotransmitter diffuses across the synaptic cleft and binds to receptor proteins on postsynaptic membrane. 3. Receptor binding leads to change in permeability of postsynaptic membrane. 4. If the effect is excitatory and meets threshold then an action potential is generated on the axon (on the sarcolemma if the postsynaptic cell is a skeletal muscle) |
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What are neurotransmitter stored in in neurons and what is their release mechanism?
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they are stored in secretory vesicles and released through exocytosis at the presynaptic membrane.
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What is the gap between a synaptic bouton and a postsynaptic neuron called?
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Synaptic cleft
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What determines if the result of neurotransmitter binding to receptor proteins is excitatory or inhibitory?
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Depends on the identity and abundance of receptor proteins on the postsynaptic membrane.
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1. Excitatory effects promote the _____ of action potential
2. Inhibitory effects _____ the ability to generate an action potential |
1. Generation
2. Reduce |
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Why are effects of one action potential on the postsynaptic membrane short-lived?
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Because the the neurotransmitter molecules are either enzymatically broken down to reabsorbed.
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What needs to happen to prolong or enhance effects at postsynaptic membranes?
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Additional action potentials must arrive at the synaptic terminal, and additional molecules of ACh must be released into the synaptic cleft.
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A single neuron only has a few synapses on its cell body (True/False)
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False. There may be thousands of synapses on the cell body of a single neuron.
Note: Many of these will be active at any given moment, releasing a variety of different neurotransmitter. Some have excitatory effects and others inhibitory effects. |
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How do the many active synapses at a neuron cell body affect the activity of the receptive neuron?
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The activity of the receptive neuron depends on the sum of all of the excitatory and inhibitory stimuli influencing the axon hillock at any given moment.
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What is another name for nonvesicular synapses?
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Electrical synapses
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What makes nonvesicular synapses structurally different from vesicular synapses?
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In nonvesicular synapses the presynaptic and postsynaptic membranes are tightly bound together and have communicating junctions.
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What is the significance of communicating junctions in non-vesicular synapses?
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Permit the passage of ions between the cells. This allows the two cells to function as if they have a common membrane and allow nerve impulses to cross from one neuron to the next without delay.
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1. Vesicular synapses only conduct nerve impulses in one direction (True/False)
2. Nonvesicular synapses only conduct nerve impulses in one direction (True/False) |
1. True
2. False. In either direction. |
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What is a neuronal pool?
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A group of interconnected neurons with specific functions.
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Are neuronal pools define on function or on anatomical ground?
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Function. Therefore a pool may be diffuse, involving neurons in several different regions of the brain or localized, with all the neurons restricted to one specific location in the brain or spinal cord.
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How many neuronal pools are estimated to be in CNS?
a. Few hundred to few thousand b. Few thousands to few hundred thousand |
a. A few hundred to a few thousand
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A pool may contain both excitatory and inhibitory neurons (True/False)
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True
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Each neuronal pool has a limited number of input sources and output destinations (True/False)
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True
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What is the basic "wiring pattern" found in a neural pool called?
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Neural circuit
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What are the functions of a Neural circuit?
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1. Divergence
2. Convergence 3. Serial processing 4. Parallel processing 5. Reverberation |
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What is the function of the divergence pattern of a neural circuit?
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A mechanism for spreading stimulation to multiple neurons or neuronal pools in the CNS
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What is the function of the convergence pattern of a neural circuit?
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A mechanism providing input to a single neuron from multiple sources. (Several neurons synapse onto the same postsynaptic neuron)
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What is a serial processing circuit in a neural pool?
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In which neurons or pools work in a sequential manner.
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What is a parallel processing circuit in a neural pool?
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In which individual neurons or neuronal pools process information simultaneously.
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What is the function of the reverberation pattern of a neural circuit?
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A feedback mechanism that may be excitatory or inhibitory.
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What is an example divergence in neurons?
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Sensory neurons. Considerable divergence occurs when sensory neurons bring information into the CNS, for the information is distributed to neuronal pools throughout the spinal cord and brain
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What is an example of convergence in neurons?
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Motor neurons. Allows for variable control of motor neurons by providing a mechanism for their voluntary and involuntary control e.g. control of lungs outside of our awareness by respiratory centers in brain and voluntary control of lungs as when we take a deep breath and hold it. Two different neuronal pools are involved but they both synapse on the same motor neurons.
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Give an example of serial processing neural circuit.
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Serial processing occurs as sensory information is relayed from one processing center to another in the brain.
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What kind of neural circuit is responsible for many different responses occurring simultaneously to the same information/stimulus?
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Parallel processing neural circuit.
Note: An example would be withdrawing foot, feeling pain and shouting "ouch" all at the same time after stepping on a sharp object. |
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How is positive feedback provided to presynaptic neurons in reverberation?
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Collateral axons extend back to the source of the impulse and further stimulate the presynaptic neurons.
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How long does a reverberating circuit stay activated?
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Till synaptic fatigue occurs or inhibitory stimuli break the cycle.
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Reverberation can occur within the same neural pool or may involve a series of interconnected pools (True/False)
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True
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Reverberation between neuronal pools may be involved in the maintenance of what kind of functions?
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1. Maintenance of consciousness
2. Muscular coordination 3. Normal breathing patterns |
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The functions of the nervous system depend on what?
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Interactions between neurons in neuronal pools.
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Axons and cell bodies in the CNS and PNS are randomly scattered (True/False)
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False. They form masses or bundles with distinct anatomical boundaries.
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How are cell bodies and axons organized in the PNS?
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Cell bodies: In ganglia (for both sensory and visceral motor neurons)
Axons: bundled together in nerves (both spinal and cranial) |
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How are cell bodies and axons organized in the CNS?
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Cell bodies: In centers, nuclei and the neural cortex
Axons: In tracts and columns Centers and tracts linked together form pathways. |
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The cell bodies of somatic motor neurons are found in ganglia (True/False)
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False. The cell bodies of the somatic motor neurons are located in the CNS.
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1. Spinal nerves are connected to the _______
2. Cranial nerves are connected to the _______ |
1. Spinal cord
2. Brain |
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What does the term higher centers refers to?
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The most complex integration centers, nuclei, and cortical areas of the brain.
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What is an ascending pathway?
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A sensory pathway the distributes information from peripheral receptors to processing centers in the brain.
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What is an descending pathway?
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A motor pathway that begins at CNS centers concerned with motor control and end at the effectors they control.
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Identify two types of synapses?
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1. Vesicular
2. Nonvesicular |
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In general, how do excitatory and inhibitory synapses differ?
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Excitatory: promote the generation of nerve impulses in the postsynaptic cells
Inhibitory: oppose the generation of nerve impulses in the postsynaptic cell |
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Distinguish between a neuronal pool whose function is divergence and neuronal pool whose function is convergence.
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Divergence: spread of information from one neuron to several neurons or from one pool to multiple pools.
Convergence: several neurons synapse on the same postsynaptic neuron, or several neuronal pools synapse on one neuronal pool |
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Describe the following anatomical structures that occur within the central nervous system: center, tract and pathway.
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Center: collection of neuron cell bodies with a common function
Tracts: bundles of axons in the CNS that share common origins, destinations and functions Pathways: centers and tracts that link the brain with the rest of the body |
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What are the two divisions of the autonomic nervous system?
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1. Sympathetic division
2. Parasympathetic division |
