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BIO 203 > Lecture 15 > Flashcards

Lecture 15 Flashcards

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1
Q

What are the 3 overall functions of the nervous system?

A
  • Stimulate muscle and glands
  • Produce quick effects by electrochemical mechanisms
  • Contributes to to homeostatic feedback loops
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2
Q

What are the 2 parts of the CENTRAL nervous system (CNS)?

A
  • Brain
  • Spinal cord
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3
Q

What does the brain do for the CNS?

A

It is the central processing center

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4
Q

What does the spinal cord do for the CNS?

A

It is the gateway between the brain and trunks/limbs

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5
Q

What are the 2 parts of the PERIPHERAL nervous system (PNS)?

A
  • Nerves
  • Ganglia
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6
Q

What are nerves?

A

Cordlike structures that conduct information

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7
Q

What are nerves composed of?

A

Axons and neurons

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8
Q

What are ganglia?

A

Knot-like swelling in a nerve (contain neuron cell bodies)

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9
Q

What do ganglia serve as in the PNS?

A

It serves as relay centers, where neurons synapse and transmit information to each other

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10
Q

What does the CNS do?

A

Receives and processes information, initiates action

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11
Q

What does the PNS do?

A

Transmits signals between the CNS and the rest of the body

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12
Q

What do sensory neurons do?

A

Relay information about stimuli such as temp, pressure, light, pain, and certain chemicals back to the brain

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13
Q

What does the somatic sensory division do?

A

Sensory nerves from the skin, skeletal muscles, bones, and joints

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14
Q

What does the visceral sensory division do?

A

Detects changes in the viscera (the organs in the thoracic and abdominal cavities)

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15
Q

What does the somatic motor division do?

A
  • Voluntary muscle contractions
  • Involuntary somatic reflexes
    Motor nerves that innervate skeletal muscles
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16
Q

What does the visceral motor division do?

A

AKA autonomic NS (it is largely autonomous)
- Controls cardiac muscle
- Controls smooth muscle
- Glands

sympathetic and parasympathetic

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17
Q

What are the 3 functional properties found in all neurons?

A
  • Excitability (irritability)
  • Conductivity
  • Secretion
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18
Q

What is excitability in a neuron?

A

Respond to environmental changes (stimuli)

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19
Q

What is conductivity in a neuron?

A

Produce electrical signals that travel along nerve fibers (axons) to reach other cells at distant locations

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20
Q

What is secretion in a neuron?

A

Nerve fiber endings (axon terminals) release chemical neurotransmitters that influence other cells

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21
Q

What are the 2 differential structures in the PNS?

A
  • ganglia
  • nerves
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22
Q

What are ganglia in the PNS?

A

Collections of neuron cell bodies in the PNS

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23
Q

What are nerves in the PNS?

A

Bundles of axons in the PNS

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24
Q

What are the 5 differential structures in the CNS?

A
  • neural cortex
  • nuclei
  • tracts
  • columns
  • centers
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25
Q

What are nuclei in the CNS?

A

Collections of neuron cell bodies in the interior of the CNS?

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26
Q

What are tracts in the CNS?

A

Bundles of CNS axons that share a common origin, destination, and function

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27
Q

What are columns in the CNS?

A

Several tracts that form an anatomically distinct mass

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28
Q

What are the centers in the CNS?

A

The integrate of all the information
Lower centers (incl spinal cord): carry out essential body functions
Higher centers:control more sophisticated information processing

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29
Q

What are the 3 functional categories of neurons?

A
  1. PNS Sensory (afferent which is input) neurons conduct signals from receptors for the CNS
  2. inbetween Interneurons are confined to the CNS (integrative function)
  3. PNS Motor (efferent which is output) neurons conduct signals from the CNS to effectors such as muscles and glands
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30
Q

What are dendrites on a neuron?

A

Chemically regulated ion gates respond to stimulation by NTs
Receive signals from other neurons

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31
Q

What happens when a neuron has more dendrites?

A

The neuron can receive more information

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32
Q

What is the soma (neurosoma, cell body, perikaryon) on a neuron?

A

The neuron’s control center (metabolic and regulatory functions)
Produces NTs

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33
Q

What is the trigger zone on a neuron?

A

Axon hillock + initial segment
Plays important role in initiating nerve signal

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34
Q

What is an axon (nerve fiber)on a neuron?

A

Only the axon has voltage voltage regulated ion gates - “the conducting region”
Originate from the axon hillock

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35
Q

What shape are axons?

A

Cylindrical and relatively unbranched (few branches near the soma, called axon collateral)

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36
Q

What is terminal arborization?

A

Axons branching extensively at their distal end

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37
Q

What is the terminal button?

A

Each branch ends in a bulbous axon terminal which is the terminal button

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38
Q

What are neurofibrils?

A

Actin filaments

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39
Q

What are chromatophilic substances (nissl bodies)?

A

Stained masses if rough (granular) ER & ribosome separated by the bundles of neurofibrils (involved in protein synthesis)

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40
Q

What are lipofuscin granules?

A

Products of lysosomal activity

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41
Q

What is “aging pigment”

A

They accumulate with age and push the nucleus to one side of the cell instead of in the middle of the cell

42
Q

What are the 4 structural classes of a neuron?

A

*According to number of processes extending from the soma

Multipolar
Bipolar
Unipolar
Anaxonic

43
Q

What are multipolar neurons?

A

Most neurons of the brain and spinal cord

44
Q

What are bipolar neurons?

A

Sensory neurons that are located in some special sense organs

45
Q

What are unipolar neurons?

A

Most are primary or first-order sensory neurons (touch and pain)

46
Q

What are anaxonic neurons?

A

No axon
They communicate locally (no AP)

47
Q

What are microtubules?

A

They are the track for organelle transport in neurons

48
Q

What is retrograde transport?

A

Inward transport
Up the axon toward the soma

49
Q

What is anterograde transport?

A

Outward transport
Down the axon away from the soma

50
Q

What direction does axonal transport happen?

A

In each direction

51
Q

What has fast anterograde transport?

A

Organelles
Enzymes
Synaptic vesicles
Small molecules

52
Q

What has slow anterograde transport?

A

Enzymes
Cytoskeleton components
Supplies new axoplasm

53
Q

What has fast retrograde transport?

A

Recycled materials
Pathogens (& toxins)

54
Q

How many neurons are in the nervous system?

A

About 1 trillion

55
Q

Neuroglia (glial cells) outnumber neurons by at least ___

A

10 to 1 (non-neuronal cells)

56
Q

What are the 4 general functions of neuroglia cells?

A

Bind neurons together (the word glia means glue)

In fetus, guide migrating neurons to their destination

Cover mature neurons (except at synapses) - gives precision to conduction pathways

Provide physical and metabolic support to neurons

57
Q

What are the 2 neuroglia cells in the PNS?

A

Schwann cells

Satellite cells

58
Q

What is the function of Schwann cells?

A

Myelin are certain axons in the PNS

Assist in regeneration of damaged fibers

59
Q

What is the function of satellite cells?

A

Surround and support cell bodies

Provide electrical insulation

Regulate the chemical environment

60
Q

What are the 4 cell types in the CNS?

A

Olygodendrocytes

Ependymal cells

Astrocytes

Microglial cells

61
Q

What do olygodendrocytes do?

A

Their processes form myelin sheaths around CNS nerve fibers

62
Q

What do ependymal cells do?

A

Line cavities

Produce cerebrospinal fluid (CSF)

Cilia help circulate CSF

63
Q

What do astrocytes do?

A

the most abundant

Convert glucose to lactate; supply this to neurons

Produce growth factors

Regulate the extracellular environment (chemical composition)

Form the blood-brain barrier

64
Q

What do microglial cells do?

A

Defensive cells (phagocytic)

They remove damaged neurons and infections

Specialized populations of macrophages

65
Q

What is the insulation of the myelin sheath around the axon?

A

20% protein and 80% lipid

66
Q

What is the myelin sheath formed by?

A

Formed by plasma mb of glial cells
- Schwann cell in the PNS
- Oligodendrocytes in CNS

67
Q

What does the myelin sheath increase?

A

Increases action potential conduction velocity

68
Q

In the CNS, where does each oligdendrocyte reach out to?

A

Reaches out to myelinate several nerve fibers

69
Q

In the PNS, what is spiraled repeatedly around a single nerve fiber?

A

Schwann cells

Each segment of axon wrapped by a different Schwann cell

70
Q

What is the neurilemma?

A

The outermost nucleated cytoplasmic layer of Schwann cells

71
Q

How can regeneration of damaged PNS nerve fiber (axon) occur?

A

If the soma is intact and at least some of the neurilemma remains

72
Q

In an unmyelinated peripheral axon, what does a Schwann do?

A

A Schwann cell folds its plasma membrane around several fibers

Only fold once around each fiber

73
Q

What is needed for an action potential to occur?

A

An initial grade of depolarization

74
Q

What is action potential?

A

A sudden, fast transitory, and propitiating change of the resting membrane potential

75
Q

What happens at resting membrane potential?

A

Ligand gated sodium channels open in response to ACh, allowing for Na+ influx inside the cell and depolarization cell to threshold

76
Q

What is depolarization?

A

The increase in the positivity of the membrane potential

77
Q

What happens during depolarization?

A

When the cell reaches threshold, voltage-gated Na+ channels open, causing an action potential

78
Q

What happens at repolarization?

A

At this high membrane potential, Na+ channels close, and voltage0-gated K+ channels open, repolarizing the cell

79
Q

What is hyperpolarization?

A

Refers to the increase in negativity of membrane potential

80
Q

K+ leak channels are always ___

A

Always open
As K+ leaks out, inside of membrane becomes more negative

81
Q

What is local potential produced by?

A

Produced by ligand-gated Na+ channels on the dendrites and soma

82
Q

What is action potential produced?

A

Produced by voltage-gated ion channels on the trigger zone and axon
(Occurs only where there is a increase in density of these channels)

83
Q

Local potential may be ___ or ____

A

Excitatory (depolarizing, to more + voltages)
Inhibitory (hyperpolarizing, to more - voltages)

84
Q

Action potential always begins with what?

A

Depolarization

85
Q

Local potential is graded. What is graded?

A

Proportional to stimulus strength
Stronger stimuli open more Na+ channels

86
Q

Action potential is all-or-none law. What is that?

A

If a stimulus depolarizes the neruon to threshold, the neruon fires at its maximum voltage (not graded); if not reached: not action potential

87
Q

Local potential is reversible. What is reversible?

A

Returns to RMP if stimulation ceases before threshold is reached

88
Q

Action potential is irreversible. What is irreversible?

A

Goes to completion once it begins (it can’t be stopped once it begins)

89
Q

Local potential is local. What does this mean?

A

Has effects for only a short distance from point of origin
Incoming Na+ diffuses for short distances along the inside of the plasma membrane

90
Q

Action potential is self propagating. What does this mean?

A

It has effects at a great distance from point of origin

91
Q

Local potential is decremental. What does this mean?

A

Signal grows weaker with distance

92
Q

Action potential is nondecremental. What does this mean?

A

Signal maintains same strength regardless of distance

93
Q

How is a nerve signal conducted down an axon?

A

When the local current arrives at the axon hillock, it depolarizes that membrane at that point

If reaches the threshold voltage: the neuron now ‘fires’ (produces an action potential)

94
Q

What are the 2 factors that affect the conduction velocity of nerve signals? (How fast a nerve signal traversals down an axon)

A

Diameter

Presence of absence of myelin

95
Q

How does diameter affect nerve signal speed?

A

Large axons have more surface area and conduct signals
(The conduction velocity is proportional to fiber diameter)

96
Q

We have a lot of ions flooding into the axon, so ____

A

So the more space they have to travel, the more likely they will be able to keep going in the right direction

97
Q

How does the presence or a sense of myelin affect nerve signal speed?

A

Myelin increases signal conduction (and myelin thickness)

98
Q

What kind of conduction do nonmyelinated axons have?

A

Continuous

Uninterrupted wave of electrical excitation all along the fiber

99
Q

What other conduction can myelinated axons have?

A

Saltatory conduction

100
Q

What does saltatory conduction create?

A

Since APs occur only at the nodes, saltatory conduction creates a false impression that the nerve signal jumps from node to node

BIO 203 (6 decks)

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