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Advanced Anatomy & Physiology > Chapter 11: Fundamentals Of The Nervous System And Nervous Tissue > Flashcards

Chapter 11: Fundamentals Of The Nervous System And Nervous Tissue Flashcards

1
Q

What are the 3 overlapping functions of the nervous system?

A

1) Sensory input
2) Integration
3) Motor output

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2
Q

Sensory input

A

Information gathered by sensory receptors about internal and external changes

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3
Q

Integration

A

Processing and interpretation of sensory input

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4
Q

Motor output

A

Activation of effector organs (muscles and glands) produces a response

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5
Q

What 2 parts is the nervous stern spit into?

A

1) Central NS

2) Peripheral NS

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6
Q

Central NS

A

Contains brain and spinal cord of dorsal body cavity

  • Integration and control center
    • interprets sensory input and dictates motor output
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7
Q

Peripheral NS

A

Contains nerves that extend from brain and spinal cord

  • Spinal nerves
  • Cranial nerves
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8
Q

What are the 2 functional divisions of the peripheral NS?

A

1) Sensory (afferent) division

2) Motor (efferent) division

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9
Q

Sensory (afferent) division

A

Convey impulses to CNS

  • Somatic sensory fibers
  • Visceral sensory fibers
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10
Q

Somatic sensory fibers

A

Convey impulses from skin, skeletal muscles, and joints to CNS

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11
Q

Visceral sensory fibers

A

Convey impulses from visceral organs to CNS

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12
Q

Motor (efferent) division

A

Transmits impulses from CNS to effector organs

Two divisions:

1) Somatic NS
2) Autonomous NS

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13
Q

Somatic NS

A

Function: conduct impulses from CNS to skeletal muscle

• Voluntary

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14
Q

Autonomous NS

A

Function: regulates smooth muscle, cardiac muscle and glands

• Involuntary

2 Functional Subdivisions:

1) Sympathetic
2) Parasympathetic

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15
Q

Sympathetic

A

Fight or flight

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16
Q

Parasympathetic

A

Resting; homeostasis; daily activities

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17
Q

What are the 2 cell types in the nervous tissue?

A

1) Neuroglia (glial cells)

2) Neurons (nerve cells)

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18
Q

Neuroglia (glial cells)

A

Small cells that surround and wrap delicate neurons

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19
Q

Neurons (nerve cells)

A

Excitable cells that transmit electrical signals

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20
Q

What are the 4 main neuroglia that support CNS neurons?

A
  1. Astrocytes
  2. Microglial cells
  3. Ependymal cells
  4. Oligodendrocytes
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21
Q

Astrocytes

A
  • “star-like”
  • Location: cling to neurons, synaptic endings and capillaries
  • Function: exchanges between capillaries and neurons
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22
Q

Microglial cells

A
  • Small, ovoid cells w/ thorny processes

* Function: touch and monitor neurons; migrate toward injured neurons

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23
Q

Ependymal cells

A
  • Location: line the central cavities

* Function: forms semi-permeable barrier between cerebrospinal fluid in cavities and tissue fluid bathing

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24
Q

Oligodendrocytes

A

Function: wrap around CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers

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25
Q

Myelin

A

A mixture of proteins and phospholipids forming a whitish insulating sheath around many nerve fibers, increasing the speed of the impulses

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26
Q

What are the 2 major neuroglia cells found in the PNS?

A

1) Satellite cells

2) Schwann cells

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27
Q

Satellite cells

A
  • Location: surround neuron cell bodies in PNS

* Function: similar to astrocytes of CNS

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28
Q

Schwann cells

A

• Location: surround all peripheral nerve fibers and form myelin sheaths in thicker fibers

• Function: similar to oligodendrocytes
(Vital to regeneration of damaged peripheral nerve fibers)

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29
Q

Nuclei

A

Clusters of neuron cell bodies in CNS

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30
Q

Ganglia

A

Clusters of neuron cell bodies in PNS

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31
Q

Tracts

A

Bundles of neuron processes in CNS

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32
Q

Nerves

A

Bundles of neuron processes in PNS

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33
Q

What are the 2 types of processes?

A

1) Dendrites

2) Axon

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34
Q

Dendrites

A

Convey incoming messages toward cell body

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35
Q

Axon hillock

A

A cone-shaped area that the axon of each neuron starts

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36
Q

Nerve fibers

A

Long axons

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37
Q

Axon terminals

A

Distal endings

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38
Q

Describe myelin in the PNS

A

Myelin sheath gaps

- gaps between adjacent Schwann cells

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39
Q

Describe myelin in the CNS

A
  • White matter

* Gray matter

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40
Q

White matter

A

Regions of brain and spinal cord with dense collections of myelinated fibers (usually fiber tracts)

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41
Q

Gray matter

A

Mostly neuron cell bodies and myelinated fibers

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42
Q

What are the 3 types of neurons by number of processes?

A
  1. Multipolar
  2. Bipolar
  3. Unipolar
43
Q

Multipolar

A

3 or more processes (1 axon, others dendrites)

- most common in CNS

44
Q

Bipolar

A 
2 processes (1 axon, 1 dendrite)
- Rare
45
Q

Unipolar

A

1 T-like process (2 axons)

  • Peripheral (distal) process
  • Proximal (central) process
46
Q

Peripheral (distal) process

A

Associated with sensory receptor

47
Q

Proximal (central) process

A

Enters CNS

48
Q

What are the 3 types of neurons grouped by direction in which nerve impulses travel relative to CNS?

A
  1. Sensory
  2. Motor
  3. Interneurons
49
Q

Sensory

A

Unipolar

  • Location: ganglia in PNS
  • Function: transmit impulses from sensory receptors toward CNS
50
Q

Motor

A

Multipolar

  • Location: CNS (except some autonomic neurons)
  • Function: carry impulses from CNS to effectors
51
Q

Interneurons

A
  • Location: between motor and sensory neurons

* Function: shuttle signals through CNS pathways

52
Q

What happens when opposite charges are separated?

A

The system has potential energy

53
Q

Voltage

A

A measure of potential energy

54
Q

Current

A

Flow of electrical charge (ions) between 2 points

55
Q

Resistance

A

Hindrance to charge flow

56
Q

What are the 2 main types of ion channels?

A

1) Leakage channels

2) Gated channels

57
Q

Leakage (non gated) channels

A

Always open

58
Q

Gated channels

A

Part of the protein changes shape to open/ close the channel

59
Q

What are the 3 main gated channels?

A

1) Chemically gated
2) Voltage gated
3) Mechanically gated

60
Q

Chemically gated (ligand-gated) channels

A

Open only with binding of a specific chemical

- Ex: neurotransmitter

61
Q

Voltage gated channel

A

Open and close in response to changes in membrane potential

62
Q

Mechanically gated channels

A

Open and close in response to physical deformation of receptors, as in sensory receptors

63
Q

Electrochemical gradient

A

Electrical and chemical gradients combined

• ion flow creates an electrical current, and voltage changes across membrane

64
Q

What is the resting membrane potential of a resting neuron?

A

Approx. -70mv

65
Q

What is the charge of the cytoplasmic side of the membrane?

A

Negative

66
Q

Is the membrane polarized?

A

Yes

67
Q

What are the differences in ionic composition?

A

• ECF has higher Na+ concentration
- balanced by Cl- (chloride ions)

• ICF has higher K+ concentration
- balanced by negative charged proteins

68
Q

What ion plays the most important role in membrane potential?

A

Potassium (K+)

69
Q

What are the differences in plasma membrane permeability?

A

• Slightly permeable to Na+ (leakage channels)
- diffuses down gradient

• More permeable to K+ (more leakage channels)
- diffuses up gradient

More K+ diffuses out than Na+ in
- inside if cell is more negative

Establishes resting membrane potential

Sodium- potassium pump stabilizes resting membrane potential
• 3 Na+ out, 2 K+ in

70
Q

What signals are produced by the changes of the resting membrane potential?

A
  • Graded potentials

- Action potentials

71
Q

Graded potentials

A

Incoming signals operating over short distances

72
Q

Action potential

A

Long- distance signals of axons

73
Q

What 2 terms describe membrane potentials relative to resting membrane potential?

A
  • Depolarization

- Hyperpolarization

74
Q

Depolarization

A

Decrease in membrane potential (towards 0 and above)

  • Inside of membrane: less negative than RMP
  • producing impulses increases
75
Q

Hyperpolarization

A

Increase in membrane potential (away from zero)

  • inside of membrane: more negative than RMP
  • producing impulse decreases
76
Q

Describe Graded Potential

A

• Short-lived, localized changes in membrane potential

  • Triggered by binding of neurotransmitters at the dendrites in a synapse

Decay over distance

77
Q

Describe Action Potential

A

• Way neurons send signals: long- distance communication

Location: muscle cells and axons of neurons
Inside cell: briefly positive

Do not decay over distance

  • involves opening of specific voltage-gated channels
78
Q

What are the 4 steps of Action Potential?

A
  1. Resting state: All gated Na+ and K+ channels are closed
  2. Depolarization: Na+ channels open
  3. Repolarization: Na+ channels are inactivating and K+ channels open
  4. Hyperpolarization: Some K+ channels remain open, and Na+ channels reset
79
Q
  1. Resting state: All gated Na+ and K+ channels are closed
A

Only leakage channels for Na+ and K+ are open
- Maintains RMP

  • Each Na+ channel has 2 voltage- sensitive gates
  • Each K+ channel has 1 voltage-sensitive gate
80
Q

What are the 2 voltage-sensitive gates of Na+?

A
  • Activation gates

- Inactivation gates

81
Q

Activation gates

A

Closed at rest; open with depolarization, allowing Na+ to enter cell

82
Q

Inactivation gates

A

Open at rest; block channel it is open to prevent more Na+ from entering cell

83
Q

Describe the voltage-sensitive gate of K+

A
  • Closed at rest

* Opens slowly with depolarization

84
Q
  1. Depolarization: Na+ channels open
A
  • Depolarizing local currents (graded potential) open voltage-gated Na+ channels, and Na+ rushes into cell
  • Na+ activation and inactivation gates open

• Na+ influx causes more depolarization, which opens more Na+ channels
- ICF becomes less negative

85
Q
  1. Repolarization: Na+ channels are inactivating and K+ channels open
A

• Na+ channel inactivation gates close
- AP spike stops rising

• Voltage-gated K+ channels open
- K+ exits cell down its electrochemical gradient

Repolarization

86
Q

Repolarization

A

Membrane returns to RMP

87
Q
  1. Hyperpolarization: Some K+ channels remain open, and Na+ channels reset
A

• Some K+ channels remain open, allowing excessive K+ efflux
- inside membrane is more negative –> slight dip below resting voltage (hyper polarization)

• Na+ channels begin to reset

88
Q

All-or-None

A

An AP either happens or not at all (threshold voltage approx. -50mV)

89
Q

Propagation of an Action Potential

A

Allows AP to be transmitted from origin down entire axon length toward terminals

  • Depolarization in one area of a cell leads to one of the next part

Once triggered, AP is self-propagating at different speeds depending on myelin sheaths

90
Q

Saltatory Conduction

A

Occurs only in myelinated axons and is about 30 times faster

91
Q

Where are Voltage-gated Na+ channels located?

A

At myelin sheath gaps

92
Q

Where are APs generated?

A

Myelin sheaths gaps

93
Q

Synapses

A

Junctions that mediate information transfer

94
Q

Presynaptic neuron

A

Neuron conducting impulses toward synapse (sends information)

95
Q

Postsynaptic neuron

A

Neuron transmitting electrical signal away from synapse (receives information)

96
Q

What are the 2 main types of synapses?

A

1) Chemical

2) Electrical

97
Q

Chemical Synapses

A

• Common

Release and reception of chemical neurotransmitters

  • Electrical impulse changed to chemical across synapse, then back into electrical
98
Q

What are the 2 of a chemical synapse?

A

1) Axon terminal of Presynaptic neuron

2) Receptor region on Postsynaptic neuron neurons membrane

99
Q

Axon terminal of Presynaptic neuron

A

Contains synaptic vesicles filled with neurotransmitters

100
Q

Receptor region on Postsynaptic neurons membrane

A

Receives neurotransmitter

101
Q

Synaptic cleft

A

Fluid that fills the 2 separated parts of the neuron and neuron membrane

102
Q

What are the 6 steps of information transfer across the chemical synapse?

A
  1. AP arrives at axon terminal of presynaptic neuron
  2. Voltage-gated Ca2+ channels open, and Ca2+ axon terminal
  3. Ca2+ entry causes synaptic vesicles to release neurotransmitter
  4. Neurotransmitter diffuses across the synaptic cleft and bins to specific receptors on the postsynaptic membrane
  5. Binding of neurotransmitter opens ion channels, creating graded potentials (which will trigger an action potential of it is strong enough)
  6. Neurotransmitter effects are terminated
103
Q

How are neurotransmitters terminated?

A
  1. Reuptake by astrocytes or axon terminal
  2. Degradation by enzymes
  3. Diffusion away from synaptic cleft

Advanced Anatomy & Physiology (11 decks)

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