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BIOSCI 107 > L4 - Nerve > Flashcards

L4 - Nerve Flashcards

1
Q

Nervous system subdivisions

A
  • CNS: brain, spinal cord (and optic nerve)

- PNS: all nervous tissue outside CNS

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2
Q

Nervous system function

A
  • Maintain homeostasis (works closely along with endocrine system)
  • Initiate voluntary movements
  • Responsible for perception, behaviour and memory
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3
Q

Nervous tissue functions

A
  • Sensory: detection of internal and external stimuli and transfer to CNS
  • Integrative: analysis and storing of information
  • Motor (effector): stimulation of effectors (muscle and glands) through PNS - Control muscle activity, Regulate glandular secretions
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4
Q

Nervous tissue composition

A

Two types of cells:

1) neurons
2) neuroglia

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5
Q

Neuron features

A
  • Can be very large - longest cells in the body (up to 1 m - spinal cord to toe)
  • Conscious and unconscious control
  • Sensitive to stimuli - convert stimuli to electrical signals (action potentials)
  • Do NOT divide (once damaged, they’re damaged)
  • High metabolic rate (die rapidly without oxygen)
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6
Q

Neuron structural components

A

Dendrites, axon, cell body (soma/perikaryon), cytoskeleton

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7
Q

Dendrite appearance

A

Short, tapering, highly branched

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8
Q

Dendrite function

A

Receiving/input part of the neuron - convey nerve impulses into cell body

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9
Q

Axon appearance

A

Long, single, thin, cylindrical

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10
Q

Axon function

A

Output portion of the neuron - carries nerve impulses away from neuron/cell body

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11
Q

Axon composition

A

Axoplasm, axolemma

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12
Q

Cell body/soma/perikaryon

A

Contains nucleus and organelles

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13
Q

Cytoskeleton composition

A

Neurofibrils, Microtubules (, Lipofuscin)

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14
Q

Neurofibrils

A

bundles of intermediate filaments that provide cell shape and support

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15
Q

Microtubules

A

assist moving materials between cell body and axon

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16
Q

Lipofuscin

A

pigment occurring as yellowish brown granule clumps in aging neurons
- Product of neuronal lysosomes that accumulate as neuron ages but doesn’t seem to harm neuron

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17
Q

Structural classification of neurons

A

Multipolar, bipolar, unipolar, anaxonic

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18
Q

Multipolar. Features

A

Some of longest (spinal cord to toes muscles)

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19
Q

Multipolar. Structure

A
  • multiple dendrites
  • single axon
  • cell body among (centre of) dendrites
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20
Q

Multipolar. Location

A
  • Most common neurons in CNS (brain, spinal cord)

- All motor neurons which control skeletal muscles

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21
Q

Bipolar. Features

A

Rare and small (30 µm)

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22
Q

Bipolar. Structure

A
  • single dendrite (can branch at tip but not at the cell body)
  • single axon
  • cell body between axon and dendrite
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23
Q

Bipolar. Location

A

Special sense organs (sight - retina of eye, smell - olfactory area of brain, hearing - inner ear)
- Relay information from receptor to neurons

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24
Q

Unipolar. features

A
  • Very long (1 m) like motor nerves from CNS to toe tip (periphery back to CNS)
  • Begin as bipolar neurons in embryo and then dendrites and axon fuse together during development
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25
Q

Unipolar. Structure

A
  • Dendrites and axon are continuous (whole thing from where dendrites converge is the axon)
  • cell body is off to one side
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26
Q

Unipolar. Location

A

Most sensory nerves (touch, pressure, pain, thermal)

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27
Q

Types of sensory receptors

A

Corpuscle of touch, type 1 cutaneous mechano-receptor, lamellated receptor, nociceptor

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28
Q

Corpuscle of touch

A
  • touch receptor

- Mass of dendrites enclosed by capsule of connective tissue

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29
Q

Type 1 cutaneous mechano-receptor

A
  • touch receptor

- Free nerve endings (bare dendrites) that make contact with tactile epithelial cells of the stratum basale of skin

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30
Q

Lamellated receptor

A
  • pressure receptor

- Multilayered connective tissue capsule encloses dendrite

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31
Q

Nociceptor

A
  • pain receptor

- Free nerve endings (bare dendrites)

32
Q

Other sensory receptors

A

Thermo receptors, itch receptors, tickle receptors are also unipolar neurons with free nerve endings that serve as sensory receptors (resemble nociceptors)

33
Q

Anaxonic. Features

A

Rare and function is poorly understood

34
Q

Anaxonic. Structure

A

Anatomy cannot distinguish dendrites from axons

35
Q

Anaxonic. Location

A

Brain and special sense organs

36
Q

Functional classification of neurons

A

Sensory/afferent, motor/efferent, interneurons

37
Q

Sensory/afferent function

A

Info TO the CNS
- stimulus activates sensory receptor = sensory neurons forms action potential in its axon = impulse conveys into CNS via cranial/spinal nerves

38
Q

Sensory/afferent structure

A
  • Contain sensory receptors at dendrites or located just after sensory receptors
  • most are unipolar
39
Q

Motor/efferent function

A

Info FROM CNS to organs (muscles and glands)

40
Q

Motor/efferent structure

A

Multipolar

41
Q

Interneurons function

A

Within CNS BETWEEN sensory and motor neurons

- incoming sensory information from sensory neurons = elicit motor response by activating appropriate motor neurons

42
Q

Interneurons structure

A

Most are multipolar

43
Q

Neuroglia location

A

Both in CNS and PNS

44
Q

Neuroglia features

A
  • Make up ~50% the volume of CNS (structural glue)
  • Smaller than neurons but more numerous (5 - 50x)
  • Do not propagate action potentials, but can communicate chemically
  • Can divide within mature nervous system
45
Q

Neuroglia function

A
  • Physical structure of nervous tissue (support and protect)
  • Repair framework of nervous tissue (nourish)
  • Undertake phagocytosis (vacuum cleaner for brain)
  • Nutrient supply to neurons
  • Regulate interstitial fluid in neural tissue
46
Q

CNS neuroglia types

A

Atrocytes, oligodendrocytes, microglia, ependymal cells

47
Q

Astrocytes structure

A
  • Star-shaped, largest, most numerous neuroglia

- Syncytium network: complicated family of cells linked together in coordinated way

48
Q

Astrocyte function

A
  • Support (have microfilaments that give strength)
  • Repair (scar)
  • Communicate (chemically) with neurons via gliotransmitters (neurotransmitters) - e.g glutamate
  • Maintain environment around neuron (surrounding tissue) - e.g regulating ions
  • Maintain blood-brain barrier - protects brain + other areas of CNS from being exposed to toxins/poisons carried in blood by wrapping around vessels and influencing/controlling their permeability
  • Learning/memory by influencing formation of neural synapses
  • In embryo, secrete chemicals that appear to regulate growth, migration, interconnection among neurons in the brain
49
Q

Types of astrocytes

A

Protoplasmic, fibrous

50
Q

Protoplasmic astrocytes

A

short branching processes found in grey matter

51
Q

Fibrous astrocytes

A

long unbranched processes located in white matter

52
Q

Oligodendrocytes

A

Resemble astrocytes but smaller and contain fewer processes

53
Q

Oligodendrocyte function

A

Form myelin sheath (multilayered protein lipid cover) around CNS axons
- Can myelinate more than one neuron cell’s axon

54
Q

Myelin sheath function

A

Insulates/protects neuron and accelerates action potential

55
Q

Microglia

A

Phagocytes (resident macrophages) - protection
- If there is an infection, breakdown/damage of cells, microglia migrate to consume cellular debris, microbes (bacteria), damaged nervous tissue

56
Q

Ependymal cells structure

A

Single layer of predominantly cuboidal cells with cilia (flow) and microvilli (absorb and turn over CSF for sampling to monitor/adjust CSF composition)

57
Q

Ependymal cells function

A
  • Produce, possibly monitor and assist circulation of CSF (Cerebrospinal fluid)
  • Line CSF-filled ventricles of brain and central canal of spinal cord
  • CSF mechanical buffer
  • Moves (cilia) nutrients and waste
58
Q

Ependymal cells location

A

Ventricles of brain, central canal of spinal cord, other locations where CSF found

59
Q

PNS neuroglia

A

Schwann cells, satellite cells

60
Q

Schwann cells

A

PNS version of CNS oligodendrocyte

61
Q

Schwan cell types

A

Myelinating, non-myelinating

62
Q

Myelinating schwann cells ratio

A

One schwann cell per axon

63
Q

Myelinating schwann cell function

A

Form insulating myelin sheath around axons

64
Q

Myelinated PNS neuron structure

A

Myelinated internodes (axon and schwann cell nucleus side by side), nodes of Ranvier, neurolemma

65
Q

Neurolemma

A
  • very outer membrane of myelinating schwann cells
  • only in axons of PNS
  • aids regeneration
66
Q

Non-myelinating schwann cells ratio

A

Multiple axons per cell

67
Q

Non-myelinating schwann cell function

A

Support and surround axons

68
Q

Non-myelinating PNS neuron structure

A

Unmyelinated internodes (axons surround schwann cell nucleus), nodes (fewer than myelinated), absense of neurolemma

69
Q

Myelin features

A

Amount increases from birth to maturity and its presence greatly increases the speed of nerve impulse conduction
- during infancy, myelination is still in progress so response to stimuli is neither as rapid nor coordinated as those of older child or adult

70
Q

Satellite cell location

A

Surround neuron cell bodies

71
Q

Satellite cell function

A

Support and regulate fluid exchange between neuronal cell bodies and interstitial fluid

72
Q

Synapse

A

site of communication between two neurons or between a neuron and an effector cell

73
Q

Synaptic end bulbs

A

tips of some axon terminals that swell in bulb-shaped structures

74
Q

Synaptic vesicles

A

tiny membrane-enclosed sacs contained by synaptic end bulbs and varicosities

75
Q

Neurotransmitter

A

chemical stored and released from synaptic vesicle that excites or inhibits another neuron, muscle fibre or gland cell

BIOSCI 107 (15 decks)

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