Nervous System 1

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The nervous system is composed predominately of

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nervous tissue but also includes some blood vessels and connective tissue.

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Two cell types of nervous tissue

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are neurons and neuroglial cells.

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Neurons

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are specialized to react to physical and chemical changes in their surroundings.

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Dendrites

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are small cellular processes that receive input.

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Axons

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are long cellular processes that carry information away from neurons.

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Nerve impulses

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are bioelectric signals produced by neurons

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nerves.

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Bundles of axons

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synapse

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Small space between a neuron and the cell(s) with which it communicates is called a synapse.

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Neurotransmitters

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are biological messengers produced by neurons

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The central nervous system

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contains the brain and spinal cord

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The peripheral nervous system

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contains cranial and spinal nerves.

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Three general functions of the nervous system

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are sensory, integrative, and motor

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. Sensory receptors (location

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are located at the ends of peripheral neurons and provide the sensory function of the nervous system.

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Receptors (functions)

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gather information.
Receptors convert their information into nerve impulses, which are then transmitted over peripheral nerves to the central nervous system.

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Describe how the nervous system detects change associated with the body and reacts to that change to maintain homeostasis. (p. 354)

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Through a vast communicating network of cells and the biochemicals that they send and receive, the nervous system can detect changes in the body, make decisions based on the basis of the information received, and stimulate muscles or glands to respond. These responses counteract the effects of the changes, thus helping to maintain homeostasis.

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Examples of effectors

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are muscles and glands

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The two divisions of the motor division

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are somatic and autonomic.

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The somatic nervous system

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The somatic nervous system is involved in conscious activities.

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The autonomic nervous system

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is involved in unconscious activities.

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. The three parts all neurons

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cell body, axon, and dendrites

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A neuron’s cell body contains

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granular cytoplasm, mitochondria, lysosomes, a Golgi apparatus, and many microtubules. It also contains a large nucleus, chromatophilic substance, and cytoplasmic inclusions.

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Neurofibrils

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are fine threads that extend into axons.

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Chromatophilic substance

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is membranous sacs that contain rough endoplasmic reticulum

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why are Dendrites are usually highly branched

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Dendrites are usually highly branched to provide receptive surfaces to which processes from other neurons communicate.

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how many axon do a nueron have

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A neuron may have many dendrites but will have only one axon.

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The cytoplasm of an axon includes

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. mitochondria, microtubules, and neruofibrils.

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A synaptic knob

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A synaptic knob is a specialized ending of an axon.

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A synaptic cleft

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is the space between a synaptic knob and the receptive surface of another cell.

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Axonal transport

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is the process an axon uses to convey biochemicals that are produced in the neuron cell body.

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.Axonal transpor

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. Axonal transport is the process an axon uses to convey biochemicals that are produced in the neuron cell body.

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Schwann cells

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Schwann cells produce myelin.

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Myelin

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is a lipid-rich substance.Schwann cells produce myelin.

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A myelin sheath

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is a coating produced by Schwann cells that is wrapped around an axon.

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A neurilemma

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is a portion of a Schwann cell outside of the myelin sheath.

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A node of Ranvier

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is a narrow gap between myelin sheaths

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Myelinated axon

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Myelinated axons have myelin sheaths.White matter is composed of myelinated axons

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Unmyelinated axons

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Unmyelinated axons have no myelin sheaths.

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. Gray matter

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is composed of unmyelinated axons, dendrites, and cell bodies of neurons.

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The three major classifications of neurons

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based on structural differences are bipolar, multipolar, and unipolar

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Bipolar neurons & where are they found

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Bipolar neurons have two processes; one process is a dendrite and the other an axon.Bipolar neurons are found within the eyes, ears, and nose

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Unipolar neuronsn& location

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Unipolar neurons have one process which functions as an axon.. Unipolar neurons are located in ganglia

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Multipolar neurons & location

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Multipolar neurons have multiple dendrites and one axon.
8. Multipolar neurons are located in the brain and spinal cord.

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The three classes of neurons based on functional difference

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The three classes of neurons based on functional differences are sensory, motor, and interneurons.

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Sensory neurons

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carry nerve impulses from peripheral body parts into the brain or spinal cord
.Sensory neurons have specialized sensory receptors at the distal ends of their dendrites.
Most sensory neurons are unipolar but some are bipolar

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Interneurons

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. Interneurons are located in the brain and spinal cord.
Interneurons are multipolar and form links between other neurons.

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Motor neurons

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Motor neurons carry nerve impulses from the brain and spinal cord to effectors.
16. Motor neurons that control skeletal muscle are under voluntary control.
17. Motor neurons that control glands, smooth muscle and cardiac muscle are under involuntary control.

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In the embryo, neuroglial cells

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guide neurons to their positions and may stimulate them to grow.
2. Neuroglial cells also produce growth factors that nourish neurons.

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two types of neuroglia cells

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Schwann cells and Satellite cells are the two types of neuroglia cells found in the peripheral nervous system.

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Schwann cells

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Schwann cells produce the myelin found on peripheral myelinated neurons.

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Satellite cells

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Satellite cells support clusters of neuron cell bodies called ganglia, found in the PNS.

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. The four neuroglial cells of the central nervous

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system are astrocytes, oligodendrocytes, microglial cells, and ependymal cells.

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Astrocytes name five functions

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Astrocytes are star shaped and are commonly found between neurons and blood vessels.
8. Astrocytes provide support and hold structures together.
9. Astrocytes aid metabolism of glucose.
10. Astrocytes respond to injury of brain tissue and form a special type of scar tissue.
11. Astrocytes play a role in the blood-brain barrier, which restricts movement of substances between the blood and CNS.

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Oligodendrocytes 3 things

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. Oligodendrocytes occur in rows along myelinated axons and
form myelin in the brain and spinal cord.
13. Unlike Schwann cells, oligodendrocytes do not form neurilemma.

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Microglia

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Microglia function to support neurons, and phagocytize bacterial cells and cellular debris.

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Ependyma 4 things

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Ependyma form the inner lining of the central canal of the spinal cord and ventricles of the brain.
16. Gap junctions join ependymal cells together.
17. Ependymal cells form a porous layer through which substances diffuse freely between the interstitial fluid of the brain tissues and the fluid within the ventricles.
18. Covering the choroids plexus, ependymal cells also regulate the composition of the cerebrospinal fluid.

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Regeneration of Nerve Axons 3 things

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Injury to a neuron cell body usually kills the neuron but damaged peripheral axons usually regenerate.
2. If a peripheral axon is separated from its cell body, the distal portion of the axon deteriorates, but the proximal end of the axon develops sprouts shortly after injury.
3. Growth of a regenerating axon is slow but eventually the new axon may reestablish the former connection.

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Axons within the central nervous system do not regenerate because

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Axons within the central nervous system do not regenerate because there is no tube of sheath cells to guide it.

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Synapses

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Synapses are the places where impulses are passed from one neuron to another or to other cells.

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A presynaptic neuron

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A presynaptic neuron is the neuron that brings the impulse to the synapse.

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A postsynaptic neuron

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A postsynaptic neuron is the neuron that is stimulated by the presynaptic neuron.

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The synaptic knobs of axons contain sacs called

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synaptic vesicles.

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Synaptic vesicles contain

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Synaptic vesicles contain neurotransmitters.

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When a nerve impulse reaches a synaptic knob

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calcium diffuses inward from the extracellular fluid.

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The calcium inside the synaptic knob initiates

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a series of events that causes the synaptic vesicles to fuse with the cell membrane, releasing the neurotransmitter by exocytosis.

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Synaptic Transmission 3 things happen

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1. Released neurotransmitters diffuse across the synaptic cleft and react with specific molecules that form structures called receptors in or on the postsynaptic neuron membrane.
2. Some neurotransmitters cause ion channels to open; some cause ion channels to close.

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Synaptic potentials 2 things

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Synaptic potentials are local potentials created by changes in chemically gated ion channels.Synaptic potentials can depolarize or hyperpolarize the receiving cell membrane.

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An excitatory postsynaptic potential

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is a type of membrane change in which the receiving cell membrane is depolarized.

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. An inhibitory postsynaptic potential

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3 is a type of membrane change in which the receiving cell membrane is hyperpolarized.

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what determines whether an action potential results.

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The integrated sum of EPSPs and IPSPs

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how many diff types of neurotransmitters

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The nervous system produces at least thirty different kinds of neurotransmitters.

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Acetylcholine

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stimulates skeletal muscle contractions.

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Examples of monoamines 4 types

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Examples of monoamines are epinephrine, norepinephrine, dopamine, and serotonin.

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Examples of unmodified amino acids that act as neurotransmitters

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. are glycine, glutamic acid, aspartic acid, and GABA.

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Examples of peptides

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are enkephalins and substance P

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Peptide neurotransmitters are synthesized where

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synthesized in the rough endoplasmic reticulum of the neuron cell bodies and transported in vesicles down the axon to the nerve terminal.

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The more calcium that enters the synaptic knob

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, the more neurotransmitters that are released.

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After a vesicle releases its neurotransmitter

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After a vesicle releases its neurotransmitter, it becomes part of the cell membrane.

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The enzyme acetlycholinesterase

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functions to break down acetylcholine

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The process of reuptake

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The process of reuptake is when neurotransmitters are transported back into the synaptic knobs of the presynaptic neurons.

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Monoamine oxidase

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. Monoamine oxidase functions to inactivate epinephrine and norepinephrine after reuptake.

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Neuropeptides

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Neuropeptides are substances that alter a neuron’s response to a neurotransmitter or block the release of a neurotransmitter.

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Three examples of neuropeptides are

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Three examples of neuropeptides are enkephalins, beta endorphin, and substance P.

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Enkephalins

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Enkephalins function to relieve pain sensations.

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Endorphins

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Endorphins function to relieve pain

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The function of substance P

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The function of substance P is to transmit pain impulses into the spinal cord and on to the brain.

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the major intracellular positive ion

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Potassium ions are the major intracellular positive ion

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the major extracellular cation.

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sodium ions are the major extracellular cation.

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The distribution of potassium and sodium is largely created by

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The distribution of potassium and sodium is largely created by the sodium-potassium pump.

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The passage of potassium and sodium ions through the cell membrane depends on

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the presence of channels.

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At rest (its charge) the cell

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At rest, a cell membrane gets a slight surplus of positive charges outside, and inside reflects a slight negative surplus of impermeable negatively charged ions

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The cell uses what to actively transport sodium and potassium ions in opposite directions.

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The cell uses ATP

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Volts

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Volts are the electrical differences between two points

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A volt is called a potential difference because

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it represents stored electrical energy that can be used to do work

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The membrane potential is

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the potential difference across the cell membrane and is measured in millivolts.

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Resting potential is

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the membrane potential of a resting neuron and has a value of –70 millivolts.

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Neurons are described as excitable because

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they can respond to the changes in their surroundings

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Stimuli on neurons u

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usually affect the membrane potential in the region of the membranes exposed to the stimulus.

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The stimulus affects the membrane potential of a neuron by

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. opening a gated ion channel.

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. A membrane is hyperpolarized if

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the membrane potential becomes more negative than the resting potential.

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. A membrane is depolarized if

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the membrane becomes less negative than the resting potential.

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Local potential changes are graded meaning

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Local potential changes are graded meaning that the degree of change in the membrane potential is directly proportional to the intensity of the stimulation.

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when threshold is reached

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sodium channels open.

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Trigger zone

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. The trigger zone of an axon is the first part or initial segment of an axon.
2. The trigger zone contains many voltage-gated sodium channels.

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As sodium ions rush into the cell,

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the membrane potential changes and temporarily becomes positive on the inside.

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When sodium channels close and potassium channels open

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, potassium diffuses out across the membrane and the inside of the membrane becomes negatively charged again.

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Repolarized means

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the membrane is polar again or returned to its original resting state.

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A nerve impulse

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is the propagation of action potentials along an axon.

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all-or-nothing response

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. A nerve impulse is an all-or-nothing response, meaning if a neuron responds at all to a nerve impulse, it responds completely

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A greater intensity of stimulation on the neuron

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produces more impulses per second, but not a stronger impulse.

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The refractory period

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is the period in which a threshold stimulus will not trigger another impulse on an axon.

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An absolute refractory period is the period

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when an axon’s membrane cannot be stimulated and is the first part of the refractory period.

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A relative refractory period

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. is the period in which a stronger stimulus can trigger an impulse

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The refractory period limits

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how many action potentials may be generated in a neuron in a given time.

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what serves as an insulator.

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Myelin

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Saltatory conduction

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is the type of nerve impulse conduction that occurs only at nodes

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what exhibit salutatory conduction.

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Myelinated axons

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what affects the speed of a nerve impulse.

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The diameter of an axon

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. Myelinated axons send nerve impulses ------ than unmyelinated axons.

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faster

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Neuronal pools

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Neuronal pools are groups of neurons that make synaptic connections with each other and work together to perform a common function.

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Facilitation

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Facilitation is a condition created in which a neuron is brought closer to threshold.

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. Convergence 2 things

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Axons originating from different parts of the nervous system leading to the same neuron exhibit convergence.
2. Convergence allows the nervous system to collect, process, and respond to information.

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Divergence 3 things

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1. Axons may branch at several points.
2. Impulses leaving a neuron of a neuronal pool may exhibit divergence by reaching several other neurons.
3. Diverging axons can amplify an impulse.

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jennifer u are stupi

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yes the answer is right