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

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

Flashcards in Chapter 11: Fundamentals Of The Nervous System And Nervous Tissue Deck (103):
1

What are the 3 overlapping functions of the nervous system?

1) Sensory input
2) Integration
3) Motor output

2

Sensory input

Information gathered by sensory receptors about internal and external changes

3

Integration

Processing and interpretation of sensory input

4

Motor output

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

5

What 2 parts is the nervous stern spit into?

1) Central NS
2) Peripheral NS

6

Central NS

Contains brain and spinal cord of dorsal body cavity

- Integration and control center
• interprets sensory input and dictates motor output

7

Peripheral NS

Contains nerves that extend from brain and spinal cord
- Spinal nerves
- Cranial nerves

8

What are the 2 functional divisions of the peripheral NS?

1) Sensory (afferent) division
2) Motor (efferent) division

9

Sensory (afferent) division

Convey impulses to CNS

• Somatic sensory fibers
• Visceral sensory fibers

10

Somatic sensory fibers

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

11

Visceral sensory fibers

Convey impulses from visceral organs to CNS

12

Motor (efferent) division

Transmits impulses from CNS to effector organs

Two divisions:
1) Somatic NS
2) Autonomous NS

13

Somatic NS

Function: conduct impulses from CNS to skeletal muscle

• Voluntary

14

Autonomous NS

Function: regulates smooth muscle, cardiac muscle and glands

• Involuntary

2 Functional Subdivisions:
1) Sympathetic
2) Parasympathetic

15

Sympathetic

Fight or flight

16

Parasympathetic

Resting; homeostasis; daily activities

17

What are the 2 cell types in the nervous tissue?

1) Neuroglia (glial cells)
2) Neurons (nerve cells)

18

Neuroglia (glial cells)

Small cells that surround and wrap delicate neurons

19

Neurons (nerve cells)

Excitable cells that transmit electrical signals

20

What are the 4 main neuroglia that support CNS neurons?

1. Astrocytes
2. Microglial cells
3. Ependymal cells
4. Oligodendrocytes

21

Astrocytes

• "star-like"
• Location: cling to neurons, synaptic endings and capillaries
• Function: exchanges between capillaries and neurons

22

Microglial cells

• Small, ovoid cells w/ thorny processes
• Function: touch and monitor neurons; migrate toward injured neurons

23

Ependymal cells

• Location: line the central cavities
• Function: forms semi-permeable barrier between cerebrospinal fluid in cavities and tissue fluid bathing

24

Oligodendrocytes

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

25

Myelin

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

26

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

1) Satellite cells
2) Schwann cells

27

Satellite cells

• Location: surround neuron cell bodies in PNS

• Function: similar to astrocytes of CNS

28

Schwann cells

• 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)

29

Nuclei

Clusters of neuron cell bodies in CNS

30

Ganglia

Clusters of neuron cell bodies in PNS

31

Tracts

Bundles of neuron processes in CNS

32

Nerves

Bundles of neuron processes in PNS

33

What are the 2 types of processes?

1) Dendrites
2) Axon

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Dendrites

Convey incoming messages toward cell body

35

Axon hillock

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

36

Nerve fibers

Long axons

37

Axon terminals

Distal endings

38

Describe myelin in the PNS

Myelin sheath gaps
- gaps between adjacent Schwann cells

39

Describe myelin in the CNS

• White matter
• Gray matter

40

White matter

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

41

Gray matter

Mostly neuron cell bodies and myelinated fibers

42

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

1. Multipolar
2. Bipolar
3. Unipolar

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Multipolar

3 or more processes (1 axon, others dendrites)
- most common in CNS

44

Bipolar

2 processes (1 axon, 1 dendrite)
- Rare

45

Unipolar

1 T-like process (2 axons)
- Peripheral (distal) process
- Proximal (central) process

46

Peripheral (distal) process

Associated with sensory receptor

47

Proximal (central) process

Enters CNS

48

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

1. Sensory
2. Motor
3. Interneurons

49

Sensory

Unipolar

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

50

Motor

Multipolar

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

51

Interneurons

• Location: between motor and sensory neurons
• Function: shuttle signals through CNS pathways

52

What happens when opposite charges are separated?

The system has potential energy

53

Voltage

A measure of potential energy

54

Current

Flow of electrical charge (ions) between 2 points

55

Resistance

Hindrance to charge flow

56

What are the 2 main types of ion channels?

1) Leakage channels
2) Gated channels

57

Leakage (non gated) channels

Always open

58

Gated channels

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

59

What are the 3 main gated channels?

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

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Chemically gated (ligand-gated) channels

Open only with binding of a specific chemical
- Ex: neurotransmitter

61

Voltage gated channel

Open and close in response to changes in membrane potential

62

Mechanically gated channels

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

63

Electrochemical gradient

Electrical and chemical gradients combined
• ion flow creates an electrical current, and voltage changes across membrane

64

What is the resting membrane potential of a resting neuron?

Approx. -70mv

65

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

Negative

66

Is the membrane polarized?

Yes

67

What are the differences in ionic composition?

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

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

68

What ion plays the most important role in membrane potential?

Potassium (K+)

69

What are the differences in plasma membrane permeability?

• 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

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

- Graded potentials
- Action potentials

71

Graded potentials

Incoming signals operating over short distances

72

Action potential

Long- distance signals of axons

73

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

- Depolarization
- Hyperpolarization

74

Depolarization

Decrease in membrane potential (towards 0 and above)

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

75

Hyperpolarization

Increase in membrane potential (away from zero)

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

76

Describe Graded Potential

• Short-lived, localized changes in membrane potential

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

Decay over distance

77

Describe Action Potential

• 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

What are the 4 steps of Action Potential?

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

1. Resting state: All gated Na+ and K+ channels are closed

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

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

- Activation gates
- Inactivation gates

81

Activation gates

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

82

Inactivation gates

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

83

Describe the voltage-sensitive gate of K+

• Closed at rest
• Opens slowly with depolarization

84

2. Depolarization: Na+ channels open

• 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

3. Repolarization: Na+ channels are inactivating and K+ channels open

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

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

Repolarization

86

Repolarization

Membrane returns to RMP

87

4. Hyperpolarization: Some K+ channels remain open, and Na+ channels reset

• 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

All-or-None

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

89

Propagation of an Action Potential

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

Saltatory Conduction

Occurs only in myelinated axons and is about 30 times faster

91

Where are Voltage-gated Na+ channels located?

At myelin sheath gaps

92

Where are APs generated?

Myelin sheaths gaps

93

Synapses

Junctions that mediate information transfer

94

Presynaptic neuron

Neuron conducting impulses toward synapse (sends information)

95

Postsynaptic neuron

Neuron transmitting electrical signal away from synapse (receives information)

96

What are the 2 main types of synapses?

1) Chemical
2) Electrical

97

Chemical Synapses

• Common

Release and reception of chemical neurotransmitters

- Electrical impulse changed to chemical across synapse, then back into electrical

98

What are the 2 of a chemical synapse?

1) Axon terminal of Presynaptic neuron
2) Receptor region on Postsynaptic neuron neurons membrane

99

Axon terminal of Presynaptic neuron

Contains synaptic vesicles filled with neurotransmitters

100

Receptor region on Postsynaptic neurons membrane

Receives neurotransmitter

101

Synaptic cleft

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

102

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

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

How are neurotransmitters terminated?

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