Nas 150 Chapter 7 Nervous System

Front 1

Sensory (Input) Function

Back 1

Uses millions of sensory receptors to monitor changes (stimuli) inside and outside the body; gathered information is called sensory function

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Integrative Function

Back 2

Processess and interprets sensory input and makes decisions about what should be done at each moment

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Motor (output) Function

Back 3

The process of reaction to stimuli- the body responds by activating muscles that can produce motion or glands that can produce hormomones

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Central Nervous System (CNS)

Back 4

Brain and Spinal cord. Acts as the command and integration center of nervous system; interprets incoming sensory information and issues instructions based on past experience and present conditions

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Peripheral Nervous System (PNS)

Back 5

Cranial and Spinal nerves that lie outside the brain and spinal cord. Communication lines

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Cranial Nerves

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Carry impulses to and from the brain

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Spinal Nerves

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Carry impulses to and from the fpinsal cord

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Sensory (Afferent) Division

Back 8

Consists of nerve fibers that convey impulses to the central nervous system from sensory receptors located in various partss of the body like in skin, skeletal muscle, visceral organs.

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Somatic Sensory (Afferent) Fibers

Back 9

Consists of nerve fibers that convey impulses from the skin, skeletal muscle and joints to the central nervous system

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Viceral Sensory (Afferent) Fibers

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Consists of nerve fibers that convey impulses from visceral organs to the central nervous system

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Motor (Efferent) Divison

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Consists of nerve fibers that convey impulses from the central nervous system to effected organs which are called effectors like muscles and glands

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Somatic (Voluntary) Nervous system

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Carries impulses from the central nervous system to effectors (skeletal muscle); allows for conscious control of skeletal muscle

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Autonomic (Involuntary) Nervous system

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Carries impulses from the central nervous system to smooth and cardiac muscle and glands; has 2 subdivisions. Parasympathetic and sympathetic nervous system

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Supporting (Neuroglial of Glial) Cells

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Cells that are lumped together to protecct, support, and insulate the delicate neurons and perform special functions

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Neurons (Nerve Cells)

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Transmit impulses from one part of the body to another; each has a cell body and nerve fibers (dendrites and axons)

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Cell body

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Contains the nucleus and is the metabolic center of the bell

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Fibers

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Threadlike structures of two types, dendrites and axons

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Dendrite

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Fibers that conduct electrical impulses toard the cell body (receptive region)

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Axon

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Fiber that conducts nerve impulses away frorm the cell body (output region)

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Axon Hillock

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Elevation where the axon arises from the cell body

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Schwann Cells

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Specialized support cells that wrap tightly around the axon to form a myelin sheath

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Myelin Sheath

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Tight coil of wrapped membranes that are formed by many Schwann cells and enclose the axon; composed of a whitish fatty material that protects and insulates fibers and increases speed of transmission of nerve impulses

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Neurilemma

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Axon which consists of the Schwann cell cytoplasm and the exposed membrane

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Nodes of Ranvier

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Indentations (gaps) at regular intervals along the length of a myelinated axon

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Collateral Branch

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Branches along the length of the axon

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Axonal Terminals

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Profuse branches of the axon at their terminal end; contain synaptic vesicles that release neurotransmitters into the extracellular space

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Multipolar Neuron

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Has many processess (fibers) extending to the cell body (dendrites) and a single process (axon) extending from the cell body; most common structural type

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Bipolar Neuron

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Has two processes- a dendrite and an axon; are rare in adults (only in some special sense organs- eye and ear

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Unipolar Neuron

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Has a single process extending from the cell body that is very short and divides almost immediately into a peripheral branch (dendrite) and a central branch (axon) like sensory neurons of the perpheral nervous system are this type

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Sensory (Afferent) Neuron

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Conveys impulses from sensory receptors (in visceral organs, muscle, or skin) to the central nervous system

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Association Neuron (Interneuron)

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Conveys impulses within the brain and spinal cord

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Motor (Efferent) Neuron

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Conveys impulses away from the brain and spinal cord to effectors in the body periphery (can be muscle or glands)

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Nuclei

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Clusters of cell bodies in the central nervous system; constitute part of the gray matter of the brain and spinal cord because they lack a myelin sheath

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Ganglia

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Clusters of cell bodies found in a few sites outside the central nerbous system in the peripheral nervous system; constitute part of the grey matter of the peripheral nervous system bc they lack a myelin sheath

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Tracts

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Collections (bundles) of nerve fibers running through the central nervous system; constitute the white matter of the brain and spinal cord bc they possess a whitish colored myelin sheath (called myelinated fibers)

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Nerves

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Collections of nerve fibers running through the peripheral nervous system; constitute the white matter fo the peripheral nervous system bc they posses a whitish colored myelin sheath (called myelinated fibers)

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Naked Nerve Endings

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Pain and temperature receptors

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Meissner's Corpuscle

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Touch receptor

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Pacinian Corpuscle

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Deep pressure receptor

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Golgi Tendon Organ

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Proprioceptor that detects the degree of the stretch of tension in skeletal muscles, their tendons and joints

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Muscle Spindle

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Propriceptor that detects the degree of stretch or tension in skeletal muscles, their tendons and joints

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Sodium Pump

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Maintains a high concentration of sodium ions outside the cell since sodium ions are actively transported out of the cell against their concentration gradient ( from a region of lower concentration of sodium ions to a region of higher concentration of sodium ions- termed solute pumping); cellular ATP provides energy

Front 43

Potassium Pump

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Maintains a high concentration of potassium ions inside the cell since potassium ions are actively transported into the cell against their concentration gradient (from a region of lower concentration of potassium ions to a region of higher concentration of potassium ions-termed solute pumping); cellular ATP provides the engergy

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Sodium Gates (Channels)

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When sodium gates open, simple diffusion occurs and sodium moves from an area of its greater concentration (outsie the cell) to an area of its lessor concetration (inside a cell)

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Potassium Gates (Channels)

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When potassium gates open, simple diffusion occurs and potassium moves from an area of its greater concentration (inside the cell) to an area of its lesser concentration (outside the cell)

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Resting State (membrane polarization)

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Neurons has not received a stimulus yet; outside of the cell is positiviely charged since solute pumping (active transport) is occuring which causes sodium ions (which are positivecations) to outnumber the negatively charged ions outside the cells (anions); inside of the cell is negatively charged since even though potassium is the major intracellular cation (as a result of solute pumping or active transport), there are more negativetely charged ions inside the cell that collectively outnumber the positively charged potassium ions

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Depolarization and Generation of an Action Potential

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Stiumlus changes the permeasbility of a "patch" of the membrane; Sodium gates open adn sodium ions rapidly enter the cell by simple diffusion; polarity of the membrane then changes (outside the membrane becomes negatively charged bc of losing so many cations and inside of the cell becomes positively charged bc of gaining so manyy cations); if stimulus is strong enoug, an action potential is gengerated

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Propagation of an Action Potential

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Depolarization of first membrane patch causes sodium ion permeability changes in the adjacent membrane and the above- described events in depolarization are repeated; action potential is propagated along the legnth of membrane

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Repolarization (Return of the Resting State)

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Membrane permeability changes again causing potassium gates to open and potatssium ions rapidly leave the cell by simple diffusion; polarity of the membrane changes again (outside the membrane becomse positively charged bc of gaining so many cations and inside of the cell becomes negatively charged bc of losing so many cations); repolarization restores the membrane to its resting potential (positive outside and negative inside); ionic conditions of resting state are restored by activity of the sodium-potassium pump

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What are some factors that can impari conductionof impulses?

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Alcohol, sedatives and anesthetics. They block nerve impulses by reducing membrane permeability to sodium ions

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Synaptic Transmission

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Nerve fibers do not structurally connect with one another. There is always a gap between one neuron (called a presynaptic neuron) and the next neuron in the chain(called a postsynaptic neuron)

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Mitochondrion

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Rodlike cytoplasmic organelles responsible for ATP generation for cellular activities

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Synaptic Knob

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Swollen portion of the axon terminal that contains synaptic vesicles

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Synaptic Vesicles

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Store chemical called acetylcholine, a neurotransmitter that carries that impulse across the synapse

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Synaptic Cleft

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Store chemical called actylcholine, a neurotransmitter that carries the impulse across the synapse

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Presynaptic Neuron

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Neuron that transmits the impulse across the synapse

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4 events that lead to Transmission of an impusle across the synapse

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-The impulse arrives at the syaptic knob of the presynaptic neuron
-The synaptic vesicle fuses with the presynaptic neuron membrane and the chemical neurotransmitter is released via exocytosis
-The neurotransmitter is released into the synaptic cleft and binds to receptor sites on the postsynaptic neuron. If enough neurotransmitter is released, the whole series of the events described above for conduction for a nerve impulse will occur in the postsynaptic neuron
-The electrical changes prompted by neurotransmitter binding are very brief because the neurotransmitter is quickly removed from the synapse either by re-uptake into the axonal terminal or by enzymatic breakdown

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Reflexes

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Automatic reactions to stimuli that are rapid and predictable and happen along neural pathways called reflex archs

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Automatic Reflexx

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Stimulates and regulates the activity of smooth muscles, the heart and glands

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Somatic Reflex

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Stimulates and regulates the activity of skeletal muscles

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Receptor (Sensory)

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Detects a change in the environment (stimulus) and reacts to it

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Sensory (Afferent)Neuron

Back 62

Impusle is conducted from the dendrites, to the cell body, to the axon of a unipolar neuron with a long dendrite (peripheral branch) that runs from receptors in skin to just outside the spinal cord where cell bodies are located in ganglia, then to the short axon (central branch) in gray matter in the posterior or dorsal horn of the spinal cord

Front 63

Synapse

Back 63

GAp in gray matter in the posterior or dorsal horn of spinal cord where synaptic transmission occurs

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Association Neuron (Interneuron)

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Impulse is conducted from the dendrites, to the cell body, to the axon of a multipolar neuron, all of which are located in the gray matter of the spinal cord; ( a two neuron reflex arc lacks this neuron)

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Synapse

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Gap in gray matter of spinal cord where synaptic transmission occurs

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Motor (Efferent) Neuron

Back 66

Impulse is condected from dentrites, the cell body, to the axon of a multipolar neuron; dendrites (short fibers)and cell body are located in the gray matter of the spinal cord; single long axon exits the anterior part of the spinal cord and runs back to the effector (a muscle or gland)

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Snyapse

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Gap between neuron and muscle or gland

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Effector

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A muscle or gland that responds to the original stimulus

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Fissures

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Deep grooves that seperate the lobes of the brain

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Longitudinal Fissure

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Groove that seperates the right and left cerebral hemispheres

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Sulci

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Shallow grooves that seperates the cerebral hemispheres into gyri

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Central Sulcus

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Groove that sperates the frontal and parietal lobes of the cerebrum

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Lateral Sulcus

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Groove that seperates the temperal lobe from the frontal and parietal lobes

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Parieto-Occipital Sulcus

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Groove that seperates the occipital and parietal lobes

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Gyri

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Elevated ridges (convolutions) of tissue on the surface of the cerebrum

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Precentral Gyrus

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Posterior part of the frontal lobe that houses the primary motor area

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Poscentral Gyrus

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Anterior part of the parietal lobe that houses primary sensory area

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Lobes

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Named after the bones of the cranium that lie over them

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Frontal Lobe

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Anterior to the central fissure; houses the primary motor area of the brain that consciously allows us to move skeletal muscles, higher intellectual functions and language comprehension

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Parietal Lobe

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Posterior to the frontal lobe and superior to the temporal and occipital lobes; houses the somatic sensory area and reading centers

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Temporal Lobe

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Lateral lobes of the cerebrum; houses the auditory area of the brain

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Occipital Lobe

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Posterior lobe of the cerebrum that houses the visual area

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Corpus Callosum

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Superior to the brain stem; a large fiber tract that allows the two cerebral hemispheres to communicate

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Basal Nuclei

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Buried deep within the white matter of the cerebral hemispheres; regulate voluntary motor activities by modifying instructions sent to the skeletal muscles by the primary motor cortex

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Diencephalon

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Superior to the brain stem; enclosed by the cerebral hemispherses; major structures of the diecephalon are the thalamus, hypothalamus, and epithalamus

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Thalamus

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Encloses the shallow third ventricle of the brain; relay station for sensory impulses passing upward to the sensory cortex

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Hypothalamus

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Constitutes the floor of the diecephalon; regulates body temperature, water balance and metabolism; center for many drives and emotions

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Epithalamus

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Forms the roof of the third ventricle; important parts are the pineal body (in endocrine system) and the choroid plexus of the third ventricle

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Pineal Body

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Part of epithalamus; produces melatonin

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Choroid Plexus

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Part of the epithalamus in the brain ventricles; know of capillaries within each ventricle forms the cerebrospinal fluid

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Pituitary Gland

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Hangs from the anterior floor of the hypothalamus by a slender stalk; produces hormones

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Midbrain

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Most superior part of brain stem; consits of the cerebral aqueduct, cerebral peduncles, and the corpora quadrigemina

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Pons

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Inferior to midbrain; has vital centers involved in breathing

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Medulla Oblongata

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Most inferior part of the brain stem; regulates vital visceral activity such as controlling heart rate, blood pressure, swallowing and vomitting

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Cerebellum

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Large cauliflower like structure that projects dorsally from under the occipital lobe of the cerebrum; provides precise timing for skeletal muscle activity and controls balance and equilibrium

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Cranium

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Outermost layer of protection

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Meninges

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Three connective tissue coverings that protect the brain- the dura mater, arachnoid mater and pia mater

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Dura Mater

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Tough leathery outermost coverings

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Arachnoid Mater

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Weblike middle meningeal layer; threadlike extensions span the subarachnoid space (which contains cerebrospinal fluid) and connect the the pia mater

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Pia Mater

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Delicate innermost membrane that clings tightly to the brain and spinal cord

Front 101

Cervical Enlargement

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Swollen portion of the cord in the neck region

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Cervical Spinal Nerves

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Nerves that exit the spinal cord in the neck region

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Thoracic Spinal Nerves

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Nerves that exit the spinal cord in the thoracic area

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Lumbar enlargement

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Swollen portion of the cord in the lumbar region

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Lumbar Spinal Nerves

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Nerves that exit the spinal cord in the lumbar region

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End of Spinal Cord

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L1-L2 is the end of the spinal cord

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Cauda Equina

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Collection of spinal nerves at the inferior end of the spinal canal; so called bc it looks like a horse's tail (literal translation of "cauda equina')

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Gray Matter

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Core of the spinal cord that looks like a butterfly or the letter H in cross section; composed of two parts- the dorsal posterior horn and the ventral anterior horn; contains unmyelinated fibers

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Dorsal Horns

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Two posterior projections of the butterfly or H shaped gray matter of the spinal cord; contains association neurors

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Ventral Horns

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Two anterior projections of the butterfly or H shaped gray matter of the spinal cord; contains dendrites and cell bodies and motor neurons

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Central Canal

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Located in the center of the gray matter of the spinal cord; contains cerebrospinal fluid

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Dorsal Root

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Branch of spinal nerve that enters the dorsal part of the spinal cord; contains part of the axons of sensory neurons

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Dorsal Root Ganglion

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Swollen region of the dorsal root of the spinal nerve; contains cell bodies of the sensory neurons, whose fibers enter the cord

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Ventral Root

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Branch of spinal nerve that exits the ventral part of the spinal cord; contains axons of motor neurons

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White Matter

Back 115

Composed of myelinated fiber tracts running between higher brain centers and the spinal cord

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Posterior, Lateral and Anterior Columns

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Three regions of white matter of the spinal cord; each column contains a number of fiber tracts made up axons with the same destination and function

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Epineurium

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Outermost connective tissue covering of a nerve

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Perineurium

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Connective tissue wrapping that surrounds the fascicles (bundles of nerve fibers) inside a nerve

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Endoneurium

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Connective tissue that surrounds each of the nerve fibers in a fascicle

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Location of the Centers
Sympathetic Nervous System

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Centers are in the gray matter of the spinal cord from T1-L2 (therefore also called the thoracolumbar nervous system)

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Location of Centers
Parasympathetic Nervous System

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Centers are located in the brain (in nuclei of several of the cranial nerves) and in the sacral region of the spinal cord (S2to S4)

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Location of Ganglia
Sympathetic Nervous System

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Ganglia are located in a "sympathetic chain or trunk" located just outside the spinal cord on each side; accordingly, preganglionic neurons have short axons and postganglionic neurons have long axons

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Location of Ganglia
Parasympathetic Nervous System

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Ganglia are located in "terminal ganglia" located a short distance from organs served; accordingly, preganglionic neurons ahve long axons and postganglionic neurons have short axons

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Neurotransmitters
Sympathetic Nervous System

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Preganglionic axons are cholinergic fibers (produce actylchlorine) and postganglionic axons are adrengergic fibers (produce norepinephrine)

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Neurotransmitters
Parasympathetic Nervous System

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Both preganglionic and postganglionic axons are cholinergic fibers (produce actylcholine)

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Effects

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-Generally speaking, the sympathetic and parasympathetic branches of the autonomic nervous system are antagonistic-on any one organ these two branches have oppposite effects

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Effects
Sympathetic Nervous System

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Often referred to as the "fight or flight' nervous system; active when in an emergency or threatening situation

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Effects
Parasympathetic Nervous System

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Most active wehn the body is at rest and not threatened in any way; called the "resting and digesting" system (promotes normal digesetion and elmination and conserves body energy)