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Anatomy > Lecture 9: CNS Tissue > Flashcards

Lecture 9: CNS Tissue Flashcards

1
Q

Cranial nerves

A

Extend from the brain

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2
Q

Spinal nerves

A

Extend from the spinal cord

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3
Q

Afferent

A

Sensory - to the CNS

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4
Q

Efferent

A

Motor - away from the CNS

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5
Q

Somatic body region

A

External to the ventral body cavity (i.e., outer tube and appendicular bones and muscles including skin, skeletal musculature, axial bodies)

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6
Q

Visceral body region

A

Viscera within the ventral body cavity (i.e., inner tube as well as smooth muscle and glands throughout the body including digestive tube, lungs, heart, spleen, bladder etc)

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7
Q

Integration

A

Processes and interprets sensory input and makes decisions on what should be done

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8
Q

Neurons

A

Excitatory cells

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9
Q

Neuroglial cells

A

Non-conducting cells that wrap around, nourish, insulate, and protect delicate neurons

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10
Q

Neuron structure

A

Cell body, processes (dendrites and axons)

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11
Q

Nerve impulses

A

Action potentials

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12
Q

Dendrite

A

Receives messages; transmit toward cell body

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13
Q

Axon

A

Transmits messages; transmit impulses away from the cell body; uniform diameter; axon hillock

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14
Q

Cell body

A

5-140 um; single nucleus; chromatophilic bodies (Nissl bodies); neurofibrils

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15
Q

Chromatophilic bodies (Nissl bodies)

A

Clusters of rER and free ribosomes

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16
Q

Neurofibrils

A

Bundles of intermediate filaments that prevent cell from being pulled apart

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17
Q

Axon structural support

A

Neurofilaments, actin microfilaments, and microtubules; aids in axonal transport

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18
Q

Axon length

A

Long or short; can be 3-4 feet long

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19
Q

Axon diameter

A

Large diameter = resistance to passage of electrical current decreases = faster impulses

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20
Q

Axon branching

A

Branch less frequently than dendrites; about 90 degree angles; terminal branches with axon terminals (aka end bulbs or boutons)

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21
Q

Nerve impulse

A

Generated from axon hillock; releases neurotransmitters into synaptic cleft

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22
Q

Synapses

A

Site at which neurons communicate

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23
Q

Presynaptic neuron

A

Conducts signal toward a synapse

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24
Q

Postsynaptic neuron

A

Transmits signals away from a synapse

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25
Q

Synaptic vesicles

A

Membrane-bound sacs containing neurotransmitter chemicals

26
Q

Multipolar neuron (structure)

A

> 2 processes; multiple dendrites; one axon; >99% of neurons; most interneurons within CNS

27
Q

Bipolar neuron (structure)

A

Two processes; one dendrite; one axon; rare; special sensory organs (inner ear, olfactory epithelium of nose, retina)

28
Q

Unipolar (pseudounipolar) (structure)

A

One short single process; sensory ganglia found mainly in PNS; one branch (axon) extends to CNS (central process); one branch (dendritic) extends peripherally to receptors (peripheral process); start as bipolar

29
Q

Sensory neurons

A

Afferent; virtually all unipolar

30
Q

Motor neurons

A

Efferent; most multipolar; within CNS

31
Q

Interneurons (association neurons)

A

Confined to CNS; most multipolar; between motor and sensory neurons; 99.98% of neurons

32
Q

Characteristics of neurons

A

Extreme longevity; no mitotic division; high metabolic rate

33
Q

Neuroglial (glial) cells

A

Support cells; insulate neurons; smaller than neurons; outnumber neurons 10:1; make up half of the mass of the brain; can divide in mitotic division

34
Q

Astrocytes

A

Most common CNS type; radiating processes which cling to neurons and/or capillaries; extract blood sugar for energy; sense neuron release of neurotransmitters; signal increased blood flow; take up and release ions; help synapses form in developing neural tissue; produce molecules necessary for neural development; propagate calcium signals that may be involved in memory; unmyelinated

35
Q

Oligodendrocyte

A

Form myelin sheaths around CNS; have fewer branches; wrap around thicker axons; produce myelin sheaths, may have multiple processes that coil around and myelinate several different axons; Nodes of Ranvier

36
Q

Microglial

A

Defensive types; smallest and least abundant; many pointed projections; phagocytes-macrophages of CNS; engulf dead neuron; originate from monocyte blood cells, not nervous tissue

37
Q

Ependymal

A

Line cerebral fluid filled cavities; bathes cells of CNS; bear cilia to circulate CSF

38
Q

Satellite cells

A

Surround neuron cell bodies within ganglia

39
Q

Schwann cells

A

Form myelin sheaths and surround axons; concentric layers; Neurilemma (sheath of Schwann)-outermost nucleated cytoplasmic layer of Schwann cells external to myelin sheath layers; develop during fetal period and in first year of post-natal life

40
Q

Multiple sclerosis

A

Immune system attacks myelin around axons in CNS; more women than men affected; more devastating and quick in men

41
Q

Myelin sheaths

A

Produced by oligodendrocytes in CNS and Schwann cells in PNS; surround thicker axons; composed of lipoprotein myelin; concentric layers; prevents leakage of electrical current; increase speed of impulse conduction

42
Q

Unmyelinated axons in the PNS

A

Thin axons; conduct impulses more slowly; surround thin axons but do not wrap in concentric rings and do NOT form myelin sheath; single Schwann cell can surround multiple unmyelinated axons; found in portions of autonomic nervous system and in some sensory fibers

43
Q

Nerve fascicles

A

Groups of axons bound into bundles by connective tissue wrapping called perineurium

44
Q

Endoneurium

A

Layer of delicate connective tissue covering Schwann cells surrounding the axons

45
Q

Epineurium

A

Touch fibrous sheath which surrounds nerve

46
Q

Gray matter in spinal CNS

A

Surrounds hollow central cavities; butterfly-shaped; where neuron cell bodies cluster; dorsal half: interneurons; ventral half: motor neurons; primarily composed of neuronal cell bodies, dendrites, short unmyelinated axons of interneurons, and neuroglia

47
Q

White matter in CNS

A

Myelinated (white); tracts: bundles of axons passing between specific regions of CNS; axons either ascend from spinal cord to brain or descend from brain to spinal cord; connect various gray matter areas

48
Q

Cortex

A

In cerebrum and cerebellum; additional thin layer of gray matter external to white matter

49
Q

Gray matter interneurons

A

Process and receive sensory information; direct information to specific CNS regions; initiate appropriate motor responses

50
Q

White matter interneurons

A

Transport information (sensory and motor) from one area of the CNS to another

51
Q

Reflex arcs

A

Simple chains of neurons; explain simplest reflex behaviors; responsible for rapid involuntary automatic motor responses to stimuli; can be somatic (skeletal muscle) or visceral (smooth muscle, cardiac muscle, or glands)

52
Q

Essential components of reflex arc

A

Receptor, sensory neuron (afferent impulses to CNS), integration center (gray matter), motor neuron (efferent impulses to effector), effector

53
Q

Monosynaptic reflexes

A

Simplest of all reflexes; one sensory neuron and a motor neuron; no interneuron; stretch reflexes include the “knee-jerk” reflex and reflexes which help maintain equilibrium and upright posture; fastest of all body reflexes

54
Q

Polysynaptic reflexes

A

More common; one or more interneuron; in most simple polysynaptic reflex arcs such as withdrawal reflex in response to pricked finger: single interneuron between sensory and motor neurons (thus have two synapses and three neurons)

55
Q

Diverging circuit

A

One presynaptic neuron synapses with multiple other neurons (diverges); stretch of muscle stimulates numerous sensory neurons; some motor neurons directly innervate stretch muscle and stimulate contraction; others are interneurons that act to inhibit the activity of the antagonistic muscle group; still others are interneurons that project sensory information to the brain

56
Q

Converging circuit

A

Many neurons synapse on a single postsynaptic neuron (convergence) and a single motor neuron may receive both excitatory and inhibitory messages

57
Q

Reverberating circuit

A

One neuron in the circuit receives feedback from another neuron in the same circuit; a branch off the axon of neuron circles back and synapses with a previous neuron in the circuit; involved in control of rhythmic activities (e.g., breathing)

58
Q

Serial processing

A

Input processing; serial processing: neurons pass a signal to a specific destination in sequence (in series) along a single pathway from one neuron to the next (e.g., reflex arc or long chain of interneurons)

59
Q

Parallel processing

A

Withdrawal reflex: painful stimulus triggers nerve impulses in a sensory neuron, which initiates withdrawal reflex; Parallel processing: simultaneously, nerve impulses travel in an axon branch that extends into the spinal white matter and extends up to the brain as an ascending pathway

60
Q

Example of parallel processing

A

Integration in gray matter: multiple interneurons process nerve impulses to localize the stimulus, identify its source, and plan a response; Voluntary motor response: a voluntary (non-reflexive) motor response is initiated in cerebral gray matter and is transmitted down a descending fiber in white matter to stimulate somatic motor neurons

61
Q

Input processing: parallel processing

A

Single sensory stimulus results in multiple perceptions; single neuron sent along two or more parallel pathways allowing a single sensory stimulus to result in multiple perceptions; allows brain to rapidly evaluate stimuli and enables information to be processed and integrated along multiple pathways

Anatomy (4 decks)

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