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A & P 2 > Lecture 1: Nervous system 1 cells of NS > Flashcards

Lecture 1: Nervous system 1 cells of NS Flashcards

1
Q

What is the information the nervous system receives from the outside world

A

stimulus or sensory information

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2
Q

How is input carried from the outside world into the nervous sytem

A

by afferent or sensory paths

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3
Q

what is the main integration center of nervous system

A

the brain

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4
Q

How is nervous response / output carried through system

A

efferent or motor paths (output of the system)

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5
Q

What is the organization in order of the nervous system function

A
  1. NS receives info from outside world
  2. Info carried by afferent / sensory paths
  3. info carried to integration center
  4. nervous response / output carried by efferent / motor paths
  5. results in motor action
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6
Q

What are 2 main components of NS

A
  1. Central nervous system (CNS)

2. Peripheral Nervous System (PNS)

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7
Q

what is the CNS comprised of

A

brain and spinal cord

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8
Q

what is PNS comprised of

A

cranial nerves (12) and spinal nerves

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9
Q

What are 2 subdivisions of the PNS

A
  1. Somatic nervous system

2. Autonomic nervous system

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10
Q

what is the somatic nervous system

A

voluntary

-muscle movement

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11
Q

what is the autonomic nervous system

A

involuntary

  • sympathetic (adrenergic)
  • parasympathetic (cholinergic)
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12
Q

What are 2 major categories of cells of nervous system

A
  1. Neurons

2. Glial cells

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13
Q

What are the 2 other names for Glial cells

A
  • Gliocytes

- Neuroglia

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14
Q

how many distinct types of Glial cells are found throughout the NS

A

6

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15
Q

What are the 4 types of Glial cells that are part of the CNS

A
  1. Astrocytes
  2. Microglia
  3. Ependymal cells
  4. Oligodendrocytes
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16
Q

What are the 2 types of Glial cells that are part of the PNS

A
  1. Satellite cells

2. Schwann cells

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17
Q

What is 3 main functions of Glial cells

A
  • surround
  • protect
  • assist neurons with their functions
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18
Q

What is the structure of Astrocytes (CNS)

A
  • star shaped cell (name “astro”)

- most abundant cell in the brain

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19
Q

What is the function of Astrocytes (CNS)

A
  • creates bridge btw capillaries and neurons
  • maintains extracellular fluid surrounding CNS neurons with bulbous feet
  • Part of the blood brain barrier
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20
Q

What does the blood brain barrier do

A

protects neurons from potential toxins in blood

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21
Q

What is structure of Microglia (CNS)

A

-small cell with many spiny extensions

the extensions are in direct contact with neurons

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22
Q

What is function of Microglia (CNS)

A
  • detects damaged and infected neurons

- migrates to the damaged and infected cells and becomes a macrophagocyte

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23
Q

What is the structure of Ependymal cells (CNS)

A
  • squamous or columnar shape cells

- generally ciliated

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24
Q

What is the function of Ependymal cells (CNS)

A
  • lines central cavities of brain & spinal cord where CSF circulates
  • has tight junctions and ion pumps to assess CSF composition
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25
Q

What do cilia do throughout ventricles and spinal column

A

They are orchestrated waves beating to help circulate CSF

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26
Q

What is the structure of Oligodendrocytes (CNS)

A
  • forms the Myelin Sheath of the neurons of the CNS by wrapping around many axons at a time
  • Myelin (CT) is formed by oligodendrocytes wrapping their foot-like extensions around axons
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27
Q

What is the function of Oligodendrocytes (CNS)

A

-increases speed of action potentials (electrical signaling)

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28
Q

What is the structure of Satellite cells (PNS)

A

-flat shaped cell that surrounds the cell body of the neurons

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29
Q

What is the function of Satellite cells (PNS)

A
  • assist with PNS neuron metabolism

- regulates the extracellular liquid

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30
Q

What is structure of Schwann cells (PNS)

A
  • round and flattened

- forms the Myelin sheath of the PNS neurons by individually wrapping around an axon

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31
Q

What is the function of Schwann cells (PNS)

A

-plays a role in the regeneration of peripheral neurofibers

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32
Q

What type of cells are mature neurons

A

amitotic cells

-they do not divide (regenerate)

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33
Q

What happens when mature neurons are damaged

A
  • minor damage leads to shrinking of neurons

- severe damage = neuron dies

34
Q

When can regeneration occur in the PNS

A
  • If an axon is crushed or sectioned regeneration is possible
  • when cell body is harmed cell is lost
35
Q

When can regeneration occur in the CNS

A

NEVER

-damage is irreversible in the brain and spinal cord

36
Q

How many layers are in peripheral nerves layered bundle

A

3

37
Q

What are the layers of peripheral nerves

A
  1. Epineurium
  2. Perineurium
  3. Endoneurium
38
Q

What is the Epineurium

A

The outer-most layer surrounding a bundle of nerve fibers

39
Q

What is the Perineurium

A

the middle layer surrounding a bundle of nerve fibers

40
Q

What is the Endoneurium

A
  • surrounding a single nerve fiber

- lying on top of the myelin sheath

41
Q

Central nerves form tracts that connect

A

different areas of the CNS

-they are not bundled

42
Q

What is the name of the key locations where PNS gather

A

PLEXUS

43
Q

What are the 2 major categories of Plexus

A
  1. Spinal plexuses

2. Autonomic Plexuses

44
Q

What is step 1 of peripheral nerve regeneration

A
  • rapid swelling from because of cell leakage

- in a few hrs, axon/ myelin sheath disintegrates distal to site of injury

45
Q

What is step 2 of peripheral nerve regeneration

A
  • Schwann cells & macrophages phagocytize the myelin sheath & the axon (degraded in 1 week)
  • The neurilemma (cytoplasm + nucleus) remain intact within the endoneurium
46
Q

What is step 3 of peripheral nerve regeneration

A

Schwann cells:

  • divide and grow due to substances secreted by macrophages
  • migrate to the site & release growth and other factors that encourage axonal growth
  • form cellular cords (regeneration tube) that guide the new regenerating axon
47
Q

What is step 4 of peripheral nerve regeneration

A
  • the axon regenerates and a new myelin sheath forms

- Schwann cells protect, support & remyelinate the axon

48
Q

What are the 4 functional structures of neurons

A
  1. Reception / input
    - Dendrites
  2. Integration
    - Soma/ cell body
  3. Conduction / output
    - Axons
  4. Secretion
    - Axonal terminals
49
Q

What are the Dendrites (receiver)

A
  • Extension
  • Sometimes very numerous
  • receive many inputs potentials through synapse with other neurons & transmit them to the cell body
50
Q

What is structure and function of cell body (integrator)

A
  • responsible for the neuron’s metabolism
  • contains all the organelles except centrioles
  • amitotic (do not replace if destroyed)
  • live >100 yrs with O2 and glucose
51
Q

What are the endoplasmic reticulum and ribosomes considered

A
  • Chromatophilic substance or Nissl bodies

- Certain types of stains ( Nissl)

52
Q

What is structure of Axon

A
  • few or many long extensions
  • myelinated or unmyelinated
  • long axon are called nerve fiber
  • has axon hillock
  • has complex cellular skeleton
53
Q

What is the Axon Hillock

A
  • Portion of axon beside cell body

- Trigger zone of the action potential

54
Q

Why does axon have no RoughER or Golgi apparatus

A

cellular skeleton permits transport of organelles & molecules produced in the cell body from end to another of the neuron

55
Q

Cellular skeleton of the axon is involved with

A

transporters that use ATP to move substances along itself

56
Q

What is retrograde axonal transport

A
  • where certain organelles & components are transported back to the cell to get broken down
  • follows the peripheral nerves up the brainstem & into the brain
57
Q

What are axon collaterals

A
  • axons that branch out at right angles
  • collaterals usually ramified in millions of telodendria that have bulbous distal ends (axonal terminals or synaptic knobs)
  • endings have vesicles filled with neurotransmitters to be released in the chemical synapse
58
Q

Where are myelin sheath

A
  • on myelinated axons

- lipoproteins

59
Q

How are myelin sheath formed

A

by wrapping around the axon:

  • Oligodendrocytes (CNS)
  • Schwann cells (PNS)
60
Q

What is the speed of transmission of a nerve impulse

A
  • 100m/s (myelinated) vs 1 m/s (unmyelinated)

- touch vs pain

61
Q

Why is Myelin sheath an exceptional insulator

A

50 - 100 layers of membranes rich in myelin form the sheath of myelin

62
Q

What is the 1st external layer of myelin sheath called

A
  • Neurilemma and it is also sheath of Schwann cells
63
Q

What are the growth and other factors involved in peripheral nerve regeneration

A

NGF- nerve growth factor
BDNF - Brain derived neurotrophic factor
IGF - Insulin-like growth factor

64
Q

What are Nodes of Ranvier

A

Specialized gaps in myelinated neurons where axon is bare (~1um)

  • region rich in voltage gated sodium channels
  • help propel action potential down axon barrel
65
Q

how does an action potential spread along a myelinated axon

A

by Saltatory Conduction

  • depolarization jumps from 1 node to the next
  • propagation is concentrated and faster compared to unmyelinated axons
66
Q

What happens to voltage of action potential in bare plasma membrane

A

it decays as it leaks into the membrane (same as on Dendrites)

67
Q

What happens to voltage of an action potential in unmyelinated axon

A

There are voltage gated sodium potassium channels that have to recreate the action potential at each point along the axon. voltage does not decay but conduction is slow

68
Q

What is White Matter

A

Myelinated axons of the CNS

69
Q

What is Gray Matter

A

Groups of cell bodies of the CNS

-aka Nuclei

70
Q

What are the 2 main group classifications of neurons

A
  1. Structural

2. Functional

71
Q

What are the 3 structural classifications of Neurons

A
  1. Multipolar neurons
  2. Bipolar Neurons
  3. Unipolar neurons
72
Q

Describe multipolar neurons

A
  • 3 or more extensions
  • lots of dendrites, 1 axon
  • most common in the CNS
73
Q

Describe Bipolar neurons

A
  • 2 extensions: 1 dendrite, 1 axon
  • rare
  • sensory neurons (smell, vision)
74
Q

Describe Unipolar neurons

A 
1 extension 
-peripheral cell body
-only distal extremities are dendrites
Central process
Cell body found in the sensory ganglia & PNS
75
Q

What are the 3 functional classifications of neurons

A
  1. Afferents neurons (sensory/input)
  2. Efferent Neurons (motor/output)
  3. Association neurons (interneurons)
76
Q

What is function of Afferents neurons

A

Sensory / input

  • transmit the nerve impulse towards CNS (brain or spinal cord)
  • transmits impulses towards a brain nucleus
77
Q

What is function of Efferent neurons

A

Motor / Output

  • moves the nerve impulse away from the CNS (brain or spinal cord)
  • transmits impulses away from a given brain nucleus
78
Q

What is function of Association neurons

A

Interneurons

  • in PNS link btw sensory (afferent) & motor (efferent) neurons
  • in CNS they link btw neurons (mostly inhibitory)
79
Q

What is structure of Association neurons

A
  • Multipolar (most neurons are this type)

- in the brain these neurons are mostly inhibitory (reduced the amount of signal being received)

80
Q

What is the reflex arc

A

an involuntary, unplanned sequence or action that is nearly instantaneous in response to stimulus
ex. touch something burning hot and your hand automatically pulls away from the pain

81
Q

What forms the basis of the reflex arc

A

the 3 functional classes of neurons

  • receptors (ex. on skin) send info down the afferent neurons
  • association neurons in spinal cord send an automatic reaction bypassing the action of sending it to brain to process
  • efferent neurons send action to effectors (ex. muscles)

A & P 2 (13 decks)

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