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
2
Q
Sensory input
A
Information gathered by sensory receptors about internal and external changes
3
Q
Integration
A
Processing and interpretation of sensory input
4
Q
Motor output
A
Activation of effector organs (muscles and glands) produces a response
5
Q
What 2 parts is the nervous stern spit into?
A
1) Central NS
2) Peripheral NS
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
7
Q
Peripheral NS
A
Contains nerves that extend from brain and spinal cord
- Spinal nerves
- Cranial nerves
8
Q
What are the 2 functional divisions of the peripheral NS?
A
1) Sensory (afferent) division
2) Motor (efferent) division
9
Q
Sensory (afferent) division
A
Convey impulses to CNS
- Somatic sensory fibers
- Visceral sensory fibers
10
Q
Somatic sensory fibers
A
Convey impulses from skin, skeletal muscles, and joints to CNS
11
Q
Visceral sensory fibers
A
Convey impulses from visceral organs to CNS
12
Q
Motor (efferent) division
A
Transmits impulses from CNS to effector organs
Two divisions:
1) Somatic NS
2) Autonomous NS
13
Q
Somatic NS
A
Function: conduct impulses from CNS to skeletal muscle
• Voluntary
14
Q
Autonomous NS
A
Function: regulates smooth muscle, cardiac muscle and glands
• Involuntary
2 Functional Subdivisions:
1) Sympathetic
2) Parasympathetic
15
Q
Sympathetic
A
Fight or flight
16
Q
Parasympathetic
A
Resting; homeostasis; daily activities
17
Q
What are the 2 cell types in the nervous tissue?
A
1) Neuroglia (glial cells)
2) Neurons (nerve cells)
18
Q
Neuroglia (glial cells)
A
Small cells that surround and wrap delicate neurons
19
Q
Neurons (nerve cells)
A
Excitable cells that transmit electrical signals
20
Q
What are the 4 main neuroglia that support CNS neurons?
A
- Astrocytes
- Microglial cells
- Ependymal cells
- Oligodendrocytes
21
Q
Astrocytes
A
- “star-like”
- Location: cling to neurons, synaptic endings and capillaries
- Function: exchanges between capillaries and neurons
22
Q
Microglial cells
A
- Small, ovoid cells w/ thorny processes
* Function: touch and monitor neurons; migrate toward injured neurons
23
Q
Ependymal cells
A
- Location: line the central cavities
* Function: forms semi-permeable barrier between cerebrospinal fluid in cavities and tissue fluid bathing
24
Q
Oligodendrocytes
A
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
34
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
43
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
60
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
