Ch 11: Nervous System Flashcards
(178 cards)
1
Q
List the types of neuroglia and cite their functions.
A
- Astrocytes (CNS)
- Microglial cells (CNS)
- Ependymal cells (CNS)
- Oligodendrocytes (CNS)
- Satellite cells (PNS)
- Schwann cells (PNS)
2
Q
How are neurotransmitters classified?
A
- Chemical structure
2. Function
3
Q
What is the overall purpose of the nervous system?
A
- Master controlling and communicating system of body
2. Cells communicate via electrical and chemical signals
4
Q
List the basic functions of the nervous system
A
- Sensory input
- Integration
- Motor output
5
Q
What is the purpose of sensory input for the nervous system?
A
Information gathered by sensory receptors about internal or external changes
6
Q
What is the purpose of integration for the nervous system?
A
Processing and interpretation of sensory imput
7
Q
What is the purpose of motor output for the nervous system?
A
Activation of effector organs producing a response
8
Q
What are structure and function of the CNS?
A
- Brain and spinal cord
2. Integration and control center
9
Q
What are structure of the PNS?
A
Consists mainly of nerves that extend from brain and spinal cord (spinal and cranial nerves)
10
Q
What are the functional divisions of the PNS?
A
Sensory (afferent)
Motor (efferent)
11
Q
What is the sensory division of the PNS comprised of?
A
Somatic and Visceral
12
Q
What is the difference between somatic and visceral?
A
Somatic: Convey impulses from skin, skeletal muscles, and joints to CNS
Visceral: Convey impulses from visceral organs to CNS
13
Q
What is the motor division of the PNS?
A
Transmits impulses from CNS to effector organs
14
Q
What is the 2 divisions of the motor division?
A
- Somatic NS
2. Autonomic NS
15
Q
Describe the Somatic NS
A
- Conducts impulses from CNS to skeletal muscle
- Voluntary NS
- Somatic motor nerve fibers
16
Q
Describe the Autonomic NS
A
- Visceral motor nerve fibers
- Regulates smooth muscle, cardiac muscle, and glands
- Involuntary NS
17
Q
What are the 2 subdivisions of ANS?
A
- Sympathetic
2. Parasympathetic
18
Q
What’s the difference between sympathetic and parasympathetic ns?
A
Sym: Mobilizes body systems during activity
Para: Conserves energy and promotes house-keeping functions during rest
19
Q
What are the 2 principal cell types of the nervous system?
A
- Neuroglia
2. Neurons
20
Q
What the difference between neuroglia and neurons?
A
Neuroglia: small cells that surround and wrap delicate neuron
Neurons: excitable cells that transmit electrical signals
21
Q
What are astrocytes?
A
Most abundant versatile, highly branched glial cells that cling to neurons, synaptic endings, and capillaries
22
Q
What are the functions of astrocytes?
A
- Support and brace neurons.
- Play role in exchanges between capillaries and neurons.
- Guide migration of young neurons.
- Control chemical environment around neurons.
- Respond to nerve impulses and neurotransmitters.
- Influence neuronal functioning.
23
Q
What are microglial cells?
A
- Small, ovoid cells with thorny processes that touch and monitor neurons
- Migrate toward injured neurons
- Can transform to phagocytize microorganisms and neuronal debris
24
Q
What are ependymal cells?
A
- Line the central cavities of the brain and spinal column.
- Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells.
25
What are oligodendrocytes?
1. Branched cells.
| 2. Processes wrap CNS nerve fibers, forming insulating myelin sheaths thicker nerve fibers.
26
What are satellite cells?
1. Surround neuron cell bodies in PNS.
| 2. Function similar to astrocytes of CNS.
27
What are Schwann cells (neurolemmocytes)?
1. urround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers.
2. Vital to regeneration of damaged peripheral nerve fibers.
28
What is the structural units of nervous systems?
Neurons
29
What are the characteristics of neurons?
1. Extreme longevity
2. Amitotic
3. High metabolic rate
4. All have cell bodies
30
What is the soma (cell body) of the neuron?
Biosynthetic center of neuron
31
What’s the difference between the nuclei and ganglia?
Nuclei: clusters of neural cell bodies in CNS
Ganglia: lie along nerves in PNS
32
What is the difference between neuron processes in CNS and PNS?
1. CNS: tracts
| 2. PNS: Nerves
33
What are the 2 processes?
1. Dendrites
| 2. Axon
34
What are the properties of dendrites?
1. Short, tapering, diffusely branched processes
2. Receptive (input) region
3. Convey incoming messages as graded potential
35
What is the axon hillock?
Cone-shaped area of cell body
36
What are the long axons?
Nerve fibers
37
What does it mean when branches are occasional?
Axon collaterals
38
What are the distal ends of an axon?
Axon terminals or terminal boutons
39
What are the functional characteristics of an axon?
1. Conducting region of neuron.
2. Generates nerve impulses.
3. Transmits impulses along axolemma (neuron cell membrane) to axon terminal.
4. Communicates with many different neurons at the same time.
5. Lacks RER and Golgi apparatus
40
How does the axon compensate for not having a RER and Golgi?
1. Cell body renews proteins and membranes.
2. Efficient transport mechanisms.
3. Quickly decay if cut or damaged.
41
What is an axon terminal?
The secretory region where neurotransmitters are released into extracellular space exciting or inhibiting neurons with axons
42
How are molecules and organelles moved along axons?
1. Motor proteins
| 2. Cytoskeletal elements
43
Is the transport in the axon unidirectional?
Movement in both directions
44
What is the difference between anterograde and retrograde?
Anterograde moves away from the cell body, retrograde moves toward the cell body
45
What is a myelin sheath?
Segmented sheath around most long or large-diameter axons
46
What myelin sheaths composed of?
Myelin that are whitish, protein-lipoid substances
47
What are the functions of myelin?
1. Protects and electrically insulates axon
| 2. Increases speed of nerve impulse transmission
48
How do nonmyelinated fibers differ from myelinated?
Conducts impulses more slowly
49
How does myelination occur in the PNS?
1. Schwann cell envelops an axon
2. Schwann cell then rotates around the axon, wrapping its plasma membrane loosely around it in successive layers
3. The Schwann cell cytoplasm is forced from between the membranes and tightly wraps around axon
50
What are Myelin sheath gaps located?
Between adjacent Schwann cells
51
How do plasma membranes of mylinated cells differ from standard plasma membranes?
1. Less protein
2. No channels or carriers
3. Good electrical insulators
52
Describe the structure of nonmyelinated fibers
1. Thin fibers nor wrapped in mylin
2. Surrounded by schwann cells but no coiling
3. One cell may surround 15 different fibers
53
How are myelin sheaths in the CNS formed?
Formed by multiple, flat processes of oligodendrocytes
54
What is the difference between white and gray matter?
White: Regions of brain and spinal cord with dense collections of myelinated fibers – usually fiber tracts.
Gray: Mostly neuron cell bodies and nonmyelinated fibers.
55
What are the structural characteristics of neurons?
- Multipolar
- Bipolar
- Unipolar
56
What are the characteristics of multipolar neurons?
1. 3 or more processes
2. 1 axon and other dendrites
3. Most common and major in CNS
57
What are the characteristics of bipolar neurons?
1. 2 processes
2. 1 axon and 1 dendrite
3. Rare, found in retina and olfactory mucosa
58
What are the characteristics of unipolar neurons?
1. 1 short process
2. Distal (peripheral) process associated with sensory receptors
3. Proximal (central) process that enters the CNS
59
What are the 3 types of neuron classifications?
1. Sensory (afferent)
2. Motor (efferent)
3. Interneurons
60
What the characteristics of sensory neurons?
1. Transmit impulses from sensory receptors toward CNS.
2. Almost all are unipolar.
3. Cell bodies in ganglia in PNS.
61
What the characteristics of motor neurons?
1. Carry impulses from CNS to effectors.
2. Multipolar.
3. Most cell bodies in CNS (except some autonomic neurons)
62
What the characteristics of interneurons?
1. Lie between motor and sensory neurons.
2. Shuttle signals through CNS pathways; most are entirely within CNS.
3. 99% of body's neurons.
63
How are nerve fibers classified?
1. Diameter
2. Degree of myelination
3. Speed of conduction
64
What are the characteristics of a Group A fiber?
1. Large diameter, myelinated somatic sensory and motor fibers of skin, skeletal muscles, joints.
2. Transmit at 150 m/s.
65
What are the characteristics of a Group B fiber?
1. Intermediate diameter, lightly myelinated fibers.
| 2. Transmit at 15 m/s.
66
What are the characteristics of a Group C fiber?
1. Smallest diameter, unmyelinated ANS fibers.
| 2. Transmit at 1 m/s.
67
What are the characteristics for membrane potential?
1. Highly excitable
2. Response is generated by action potential
3. Impulse do not vary in magnitude
68
What are the 2 types of ion channels?
Leakage and gated channels
69
What are the 2 types of ion channels?
1. Leakage are always open
| 2. Gated: part of the protein changes to either open or close
70
What are the 3 types of gated channels?
1. Chemically-gated (ligand) channels
2. Voltage-gated channels
3. Mechanically gated channels
71
What is a chemically-gated channel?
Opens with binding of a specific neurotransmitter
72
What is a voltage-gated channel?
Open and close in response to changes in membrane potential
73
What are mechanically gated channels?
Open and close in response to physical deformation of receptors such as sensory receptors
74
What occurs when gated channels are open?
1. Ions diffuse across membrane along the electrochemical gradient
2. Ion flow creates an electrical current and voltage changes across membrane
75
In what directions do ions move in a concentration gradient?
Higher concentration to lower
76
In what directions do ions move in an electrical gradient?
Toward opposite electrical charge
77
What are the properties of RMP?
1. -70mV
| 2. Membrane is polarized
78
How is RMP generated?
1. Differences in ionic makeup of ICF and ECF
| 2. Differential permeability of plasma membrane
79
Describe the ionic composition differences of the plasma membrane?
1. ECF has a higher concentration of Na+
2. ICF has a higher concentration of K+
3. K+ is important for membrane potential
80
Describe the permeability of the plasma membrane?
1. Impermeable to large anionic proteins
2. Slightly permeable to Na+ (leakage channels)
3. 25 times more permeable to K+ than Na+ (leakage channels)
4. Permeable to Cl-
81
Describe the maintenance of RMP
1. More K+ diffuses out than Na+ diffuses in causing the cell to be more negative
2. Na-K pumps stabilize RMP by maintaining the concentration gradients
3Na+ (out) to 2K+ (in)
82
How does membrane potential change?
1. Concentration of ions
| 2. Change in ionic permeability of ions
83
What is the difference between grated and action potential?
Graded: incoming signals operate over short distances
Action: Long distance signals of axons
84
What does it mean to be depolarized?
Decrease in membrane potential where cell becomes less negative than RMP
85
What is the purpose for depolarization?
Increase the probability of producing a nerve impulse
86
What does it mean to be hyperpolarized?
Membrane potential becomes more negative than RMP
87
What is the purpose for hyperpolarization?
Reduces probability of producing a nerve impulse
88
What is graded potential?
Short-lived, localized changes in membrane potential
89
How is graded potential different from action potential?
1. Magnitude varies with stimulus strength
2. Stronger stimulus → more voltage changes and farther current flow
3. Triggered by stimulus that opens gated-ion channels
4. Signals over short distances
5. Either hyper or depolarization occurs
90
What is action potential?
Long-distance neural communications
91
How is action potential different from graded potential?
1. Do not decay or distance
| 2. Occurs in muscle and axons
92
What is are the 2 voltage-sensitive Na+ gates?
1. Activation
| 2. Inactivation
93
What is the difference between activation and inactivation Na+ gates?
Activation: closed at rest and open at depolarization
Inactivation: Opens at rest, block channels to prevent Na+ from entering the cell
94
Describe K+ channel voltage sensitive gate
1. Closed at rest
| 2. Opens slowly with depolarization
95
What are the steps of action potential generation?
1. Resting state
2. Depolarization
3. Repolarization
4. Hyperpolarization
96
What occurs during the resting state?
1. All gated Na+ and K+ channels are closed
| 2. Only leakage channels for K+ and Na+ are open in order to maintain RMP
97
What occurs during depolarization?
1. Opening of Na+ voltage gated channels
2. Influx of Na+ cause depolarization where more Na+ channels open, ICF becomes less negative
3. Threshold (-55 to -50mV) causes more Na+ channels to open where membrane potential reaches +30mV
98
Is depolarization a positive or negative feedback cycle?
Positive
99
What occurs during repolarization?
1. Na+ channels close
2. AP spike stops rising
3. K+ channels opens, exiting the cell until negativity is restored
100
What occurs during hyperpolarization?
1. K+ channels remain open causing excessive K+ efflux causing membrane to be more negative than RMP
2. Na+ channels begin to reset
101
What is the purpose for Na-K pumps in membrane?
1. Repolarization resets electrical conditions
| 2. After repolarization, Na-K pumps restore ionic conditions
102
What must occur for an axon to fire?
Depolarization must reach threshold
103
Do all depolarization events produce AP?
No
104
What occurs at threshold?
1. Membrane has been depolarized by 15-20mV
2. Na+ permeability increases
3. Na+ influx exceeds K+ efflux
4. Positive feedback cycle begins
105
What is the all-or-none phenomenon?
AP either happens completely or it does not happen at all
106
What is the purpose for propagation?
Allowing AP to serve as a signaling device
107
What is the purpose for local currents by Na+ influx?
1. Local currents cause depolarization of adjacent membrane areas in direction away from AP origin (toward axon's terminals).
2. Local currents trigger an AP there.
3. This causes the AP to propagate AWAY from the AP origin.
108
What occurs once self-propagation is initiated?
1. In nonmyelinated axons, each successive segment of membrane depolarizes, then repolarizes.
2. Propagation in myelinated axons differs.
109
How are action potentials similar?
They are all independent of stimulus intensity
110
How does the CNS tell the difference between a weak stimulus and a strong one?
CNS determines stimulus intensity by the frequency of impulses
111
What is the CNS indication for a strong stimulus?
Strong stimuli cause action potential to occur more frequently
112
What is the absolute refractory period?
When voltage-gated Na+ channels open, neuron can’t respond to another stimulus
113
What is the purpose for neuron’s inability to respond to another stimulus when fired?
1. To ensure each AP is all-or-none
| 2. Enforces one-way transmission of nerve impulses
114
What is the relative refractory period?
1. Follows absolute refractory period to when Na+ channels are resting, K+ channels opens, and depolarization occurs
2. Threshold for AP generation is elevated to where only exceptionally strong stimulus can cause AP
115
What determines the rate of AP propagation?
1. Axon diameter: larger diameter fiber have less resistance to local current flow and faster impulse conduction
2. Degree of myelination: continuous conduction in nonmyelinated axons is slower than saltatory conduction in myelinated axons
116
What are the properties of saltatory conduction?
1. 30x faster
2. Voltage-gated Na+ channels are in the myelin sheath gaps
3. APs generate only in the gaps
4. Electrical signals jump from gap to gap
117
What occurs during multiple sclerosis (ms)?
1. Immune system attacks myelin, turning it to hard lesions called scleroses
2. Impulse conduction slows and eventually ceases
3. Demyelinated axons increase Na+ channels
4. Causes cycles of relapse and remission
118
How do you prevent MS?
High blood levels of Vitamin D
119
What are the symptoms of MS?
1. Visual disturbances
2. Weakness
3. Loss of muscular control
4. Speech disturbances
5. Urinary incontinuence
120
What are some treatments for MS?
Drugs that modify immune system activity
121
Define synapse.
Junctions that mediate information transfer from one neuron to neuron or effector cell
122
What are the synapse classifications?
1. Axodendritic
2. Axosomatic
3. Axoaxonal
4. Dendrodendritic
5. Somatodendritic
123
What is the difference between axodendritic and axosomatic?
Axodendritic: Between axon terminal and dendrites
Axosomatic: Between axon terminals and soma
124
What is the difference between presynaptic and postsynaptic neuron?
Pre: Conducts impulse toward synapse, sending information
Post: Transmits electrical signal away from synapse receiving information
125
How would graded potential vary in strength?
1. Amount of neurotransmitter released
| 2. Time neurotransmitter stays in area
126
How are neurons connected to the cytoplasm of adjacent neurons?
Electrically coupled by gap junctions
127
Where are electrically coupled neurons most abundant?
Embryonic nervous tissue
128
What is the purpose for electrically couple neurons?
1. Rapid communication
2. Synchronized activity
3. Uni or bidirectional
129
What is a chemical synapse?
Specialized for release and reception of neurotransmitters
130
What are the components of a chemical synapse?
1. Axon terminal containing synaptic vesicles of neurotransmitters
2. Neurotransmitter receptor region
131
What separates the axon terminal from the neurotransmitter receptor region?
Synaptic cleft
132
What is the purpose for the synaptic cleft?
Prevents nerve impulses from directly passing from one neuron to the next
133
What provides the transmission across the synaptic cleft?
1. Chemical event (as opposed to an electrical one).
2. Depends on release, diffusion, and receptor binding of neurotransmitters.
3. Ensures unidirectional communication between neurons.
134
How is information transferred across the chemical synapses?
1. AP arrives at axon terminal of presynaptic neuron
2. Voltage-gated Ca2+ channels open and Ca2+ enters axon terminal
3. Ca2+ entry causes synaptic vesicles to release neurotransmitter by exocytosis
4. Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane
5. Binding of neurotransmitter opens ion channels, resulting in graded potentials
6. Neurotransmitter effects are terminated by:
1. Reuptake by astrocytes or axon terminal
2. Degradation by enzymes
3. Diffusion away from synaptic cleft
135
What is the amount of time needed for neurotransmitter to be released, diffuse across synapse, and bind to receptors?
0.3-5.0ms
136
What is the synaptic delay?
Rate-limiting step of neural transmission
137
What are the 2 types of postsynaptic potentials?
1. EPSP (excitatory)
| 2. IPSP (inhibitory)
138
What is the importance of EPSP?
Neurotransmitter binding opens chemically gated channels causing an Na+ influx greater than K+ efflux
139
How can EPSP help trigger AP?
Can spread to axon hillock, trigger opening of voltage-gated channels, and cause AP to be generated.
140
Is a single EPSP enough to trigger AP?
No, EPSP summation brings EPSP predominance to thershold
141
What is the importance of IPSP?
Reduces postsynaptic neuron's ability to produce an action potential.
Makes membrane more permeable to K+ or Cl–.
142
How would neurotransmitters hyperpolarize the cell?
1. Inner surface of membrane become more negative
| 2. AP less likely to be generated
143
What is the difference between temporal and spatial summation?
Temporal: One or more presynaptic neurons transmit impulses in rapid-fire order.
Spatial summation: Postsynaptic neuron stimulated simultaneously by large number of terminals at same time.
144
What are neurotransmitters?
What are neurotransmitters?
145
How are neurotransmitters classified?
Chemical structure
| Function
146
What is the chemical structure of ACh?
1. Released at NMJs,by some ANS neurons, by some CNS neurons.
2. Synthesized from acetic acid and choline by enzyme choline acetyltransferase.
3. Degraded by acetylcholinesterase (AChE).
147
What is the purpose of Biogenic amines?
1. Catecholamines (dopamine, norepinephrine, epinephrine)
2. Indolamines (serotonin and histamine)
3. Emotional behaviors and biological clock.
4. Some ANS motor neurons (especially NE).
5. Imbalances associated with mental illness.
148
What are the amino acid neurotransmitters?
1. Glutamate
2. Aspartate
3. Glycine
4. GABA
149
What are the different types of neuropeptides?
1. Substance P: mediator of pain signals
2. Endorphins: act as natural opiates and reduces pain
3. Gut-brain peptides: somatostatin and cholecystokinin
150
What is the purpose of purines?
Act in both CNS and PNS. Produce fast or slow responses. Induce Ca2+ influx in astrocytes.
151
What are example of purines as neurotransmitters?
1. ATP
| 2. Adenosine: potent inhibitor of brain
152
What is the purpose of gasotransmitters?
1. Lipid soluble, synthesized on demand.
2. NO involved in learning and formation of new memories; brain damage in stroke patients, smooth muscle relaxation in intestine.
3. H2S acts directly on ion channels to alter function.
153
What are examples of gasotransmitters?
Nitric oxide, CO, H2S
154
What are the characteristics of Endocannabinoids?
1. Act at same receptors as THC (active ingredient in marijuana).
2. Lipid soluble.
3. Synthesized on demand.
4. Involved in learning and memory, neuronal development, controlling appetite, and suppressing nausea.
155
How are the functions of neurotransmitters classified?
1. Effects: excitatory (depolarizing) vs inhibitory (hyperpolarizing)
2. Actions: Direct vs indirect
156
What is purpose for direct action?
1. Neurotransmitter binds to and opens ion channels.
| 2. Promotes rapid responses by altering membrane potential.
157
What are examples of direct neurotransmitters?
ACh and amino acids
158
What is the purpose for indirect action?
1. Neurotransmitter acts through intracellular second messengers, usually G protein pathways.
2. Broader, longer-lasting effects similar to hormones.
159
What are examples of indirect neurotransmitters?
1. Biogenic amines
2. Neuropeptides
3. Dissolved gases
160
What type neurotransmitters are inhibitory?
GABA and glycine
161
What type neurotransmitters are excitatory?
Glutamate
162
What type of neurotransmitter have two types of effects?
1. ACh excitatory at NMJs
| 2. ACh inhibitory in cardiac muscle
163
What are the 2 types of neurotransmitter receptors?
1. Channel-linked that mediate fast synaptic transmission
| 2. G protein-linked that oversee slow synaptic responses
164
What are the characteristics of channel-linked receptors?
1. Ionotropic
2. Ligand-gated ion channels.
3. Action is immediate and brief.
4. Excitatory receptors are channels for small cations.
5. Inhibitory receptors allow Cl– influx that causes hyperpolarization.
165
What are the characteristics of G protein-linked receptors?
1. Responses are indirect, complex, slow, and often prolonged.
2. Transmembrane protein complexes.
3. Cause widespread metabolic changes.
166
What is the mechanism of G-protein action?
1. Neurotransmitter binds to G protein–linked receptor.
2. G protein is activated.
3. Activated G protein controls production of second messengers
167
What do second messengers do?
1. Open or close ion channels.
2. Activate kinase enzymes.
3. Phosphorylate channel proteins.
4. Activate genes and induce protein synthesis.
168
What is the basic concept of neural integration?
1. Neurons function in groups
| 2. Groups contribute to broader neural functions
169
What are neuronal pools?
Functional groups of neurons
170
What is the purpose for neuronal pools?
1. Integrate incoming information received from receptors or other pools
2. Forward processed information to other destinations
171
What is a simple neuronal pool?
Single presynaptic fiber branches and synapses with several neurons in pool.
172
What is the difference between discharge and facilitated zones in simple presynaptic neuronal pools?
1. Discharge zone: neurons most closely associated with incoming fiber.
2. Facilitated zone: neurons farther away from incoming fiber.
173
What is a circuit?
Patterns of synaptic connections in neuronal pools
174
What are the four types of circuits?
1. Diverging
2. Converging
3. Reverberating
4. Parallel after-discharge
175
What is serial processing?
1. Input travels along one pathway to a specific destination.
2. System works in all-or-none manner to produce specific, anticipated response.
176
What is an example of serial processing?
Spinal reflexes
177
What is parallel processing?
1. Input travels along several pathways
2. Different parts deal simultaneously with information
3. Important for higher level mental functioning
178
What is an example of parallel processing?
Sensed smell may remind one of an odor and any associated experiences.
