Set 4 (Part I) Flashcards
1
Q
What are the components of the nervous system?
A
- Brain
- Spinal cord
- Peripheral nerves
2
Q
What is the overall function of the nervous system?
A
- Provides a fast-acting, rapid response to a particular stimulus
- Controls homeostasis along with the endocrine system
3
Q
What are the structures of the central nervous system? What is the function?
A
- Structural and functional center of the entire nervous system
- Brain and spinal cord
- Integrates sensory information, evaluates it, and initiates an outgoing response
4
Q
What are the structures of the peripheral nervous system?
A
- Nerves that lie in the “outer regions” of the nervous system
- Cranial nerves
- Spinal nerves
5
Q
What is the function of the somatic motor division?
A
Carries information to the somatic effectors (skeletal muscles)
6
Q
What is the function of the somatic sensory division?
A
Carries feedback information to somatic integration centers in the CNS from the PNS
7
Q
Differentiate automatic and somatic neurons.
A
- Automatic: without voluntary control
- Somatic: actions that we consciously make (skeletal muscle)
8
Q
Differentiate the afferent and efferent division of the automatic nervous system.
A
- Afferent (incoming): messages from the visceral receptors
- Efferent (outgoing): carries information to the visceral effectors (smooth and cardiac muscles and glands)
9
Q
The ANS efferent pathways are further categorized as what?
A
1) Sympathetic division
2) Parasympathetic division
10
Q
What is the function of the sympathetic division?
A
- Prepares the body to deal with immediate threats to the internal environment
- Produces “fight-or-flight” response
11
Q
What is the function of the parasympathetic division?
A
- Coordinates the body’s normal resting activities
- Sometimes called the “rest-and-repair” division
12
Q
Which tissues undergo vasoconstriction in times of stress?
A
- GI tract, reproductive system, urinary system
- Reduces blood flow
13
Q
Which tissues undergo vasodilatation in times of stress?
A
- Skeletal muscles, cardiovascular system (heart), respiratory system (bronchiodilation)
- Increase blood flow
14
Q
What are the sympathetic and parasympathetic effects that arise in tear glands?
A
- Sympathetic: dilation of pupil, focusing for near vision
- Parasympathetic: constriction of pupil, focusing for distance vision
15
Q
What are the sympathetic effects of the skin, cardiovascular system, and respiratory system?
A
- Skin: increases sweat, erection of hair
- Cardiovascular: vasoconstriction, vasodilation, increases heart rate
- Respiratory system: increases diameter, increases rate
16
Q
What are the sympathetic effects on the adrenal glands?
A
Secretion of epinephrine and norepinephrine by the adrenal medullae
17
Q
What are the sympathetic and parasympathetic effects that arise in the digestive system?
A
- Sympathetic: decreases activity, glycogen breakdown, glucose synthesis
- Parasympathetic: increases activity, glycogen synthesis
18
Q
What are the sympathetic and parasympathetic effects that arise in the urinary system?
A
- Sympathetic: decreases urine production, constricts sphincter, relaxes urinary bladder
- Parasympathetic: increases urine production, tenses urinary bladder
19
Q
What are the sympathetic and parasympathetic effects that arise in the reproductive system?
A
- Sympathetic: ejaculation in males
- Parasympathetic: erection of penis (males) or clitoris (females)
20
Q
What is the overall effect of the sympathetic branch of the ANS on the heart?
A
- Controls the heart in emergency situations
- Overall stimulatory effect
- When there is a need for greater blood flow
21
Q
How does the sympathetic nervous system stimulate the heart?
A
- Epinephrine is released from adrenal medulla
- Triggers the acceleration of the inactivation of K+ channels, trapping them inside the cell
- The cells remain slightly more positive, which makes it easier for them to depolarize and contract
22
Q
Which portion of the heart does norepinephrine stimulate during sympathetic control?
A
SA node
23
Q
The distension of the stomach caused by the presence of food triggers parasympathetic reflexes. What are they?
A
- Increase secretion of gastric juice
- In response to the presence of AA, gastrin is secreted by the mucosa, which increases secretion of gastric juice
24
Q
What are neurons?
A
- Excitable cells that conduct impulses (functional cells)
- Required for all nervous system activity
25
What are glial cells?
- Do not conduct information
| - Support the functions of the neurons
26
Differentiate axons and dendrites.
- Axons: carry outgoing information
| - Dendrites: receive incoming signals
27
What are the carotid arteries monitoring?
Measures the blood pressure to the brain to make sure that the brain always has enough oxygen (baroreceptor)
28
What is the cytoskeleton of neurons composed of?
- Microtubules and microfilaments
| - Neurofibrils (bundles of neurofilaments = intermediate filaments)
29
What does the cytoskeleton of neurons allow for?
Rapid transport of small organelles
30
How are neurotransmitters released?
The release of neurotransmitters is done by way of vesicles
31
What is the function of motor molecules on the cytoskeleton?
Move proteins on cytoskeleton highly for release at the synaptic knobs
32
What are the four major types of glial cells?
- Oligodendrocytes
- Microglia
- Astrocytes
- Ependymal cells
33
What type of glial cell is star-shaped, and the largest/most numerous type?
Astrocytes
34
What is the structure of astrocytes?
- Star-shaped
- Large
- Cell extensions connect to both neurons and capillaries
35
What are the two major functions of astrocytes?
- Transfer nutrients from the blood to the neurons
| - Help constitute the blood brain barrier
36
How do astrocytes help constitute the blood brain barrier?
- Form tight sheaths around brain capillaries
| - Along with tight junctions between capillary endothelial cells, they constitute the blood-brain barrier
37
What is the function of the blood-brain barrier?
- Specialized system of capillary endothelial cells
- Protects the brain from harmful substances in the bloodstream
- Allows for supplying the brain with the required nutrients for proper function
38
How does the blood-brain barrier protect the brain?
The BBB strictly limits transport into the brain through both physical (tight junctions) and metabolic (enzymes) barriers
39
What two specializations allows the limited transport of the BBB?
1. The BBB capillaries are held together by tight junctions
| 2. The feet of the astrocytes form tight sheaths around brain capillaries
40
What are tight junctions?
- Occur in cells that are joined by "collars" of tightly fused material
- Molecules cannot permeate the cracks of tight junctions
41
How many barriers does the BBB have? What structure does that resemble?
- Double barrier: astrocyte feet and the endothelial cells
| - Glomerulus of the kidneys has a similar structure, but they are more permeable
42
The specificity of the substances entering the blood-brain barrier is mediated by what?
Receptor-specific mechanisms
43
Which molecules can penetrate the BBB?
- Lipid-soluble molecules (ethanol, caffeine)
| - Via the lipid membranes of the cell
44
Which molecules cannot penetrate the BBB?
- Water-soluble molecules
| - Unable to cross without the use of specialized carrier-mediated transport
45
What is a liposome? What are they used for?
- Spherical vesicle with a membrane composed of a phospholipid bilayer
- Used to deliver drugs or genetic material into a cell
46
How can drugs be indiscriminately delivered past the lipid bilayer?
If they are enclosed in a liposome, the lipid bilayer can fuse with other bilayers (e.g. the cell membrane)
47
What are microglia?
- Macrophages of the brain
| - Small, usually stationary cells
48
Which glial cell is usually stationary?
Microglia
49
When would microglia enlarge?
In inflamed brain tissue, they enlarge, move and carry-on phagocytosis to remove microorganisms and cellular debris
50
Which glial cells resemble epithelial cells?
Ependymal cells
51
What are the functions of ependymal cells?
- Form thin sheets that line fluid-filled cavities (cerebral-spinal fluid) in the CNS
- Some produce fluid
- Others aid in the circulation of fluid
52
Why do we have cerebral-spinal fluid? Where is it found?
- Found in the cerebrum and the spinal cord
- Formed in the ventricles (spaces inside the brain that contains CSF)
- Fluid provides nutrient and waste exchange
- Gets exchange several times per day and empties into our venous supply
53
What is the function of oligodendrocytes?
- Hold nerve fibers together
| - Produce the myelin sheath in CNS
54
What is found in the grey matter?
- Nerve cell bodies
| - Unmyelinated neurons
55
What is found in the white matter?
Myelinated neurons
56
Which two glial cells are sources of neural stem cells?
- Astrocytes
| - Ependymal cells
57
Which glial cell is defective in multiple sclerosis?
Oligodendrocytes
58
What are the characteristics of multiple sclerosis?
- Characterized by myelin loss and destruction
- Plaque-like lesions form
- Failure in nerve conduction
- Communication interrupted
- Treatment: inflammation reduction
59
Which two cells are only found in the peripheral nervous system?
- Schwann cells
| - Satellite cells
60
What is the functional equivalent of oligodendrocytes in the PNS?
Schwann cells
61
What is the function of Schwann cells?
Support nerve fibers and in some cases form myelin sheaths
62
What are the nodes of Ranvier?
Section of unmyelinated axon membrane between two Schwann cells
63
What are satellite cells?
- Another type of Schwann cell that covers and supports neuron cell bodies in the PNS
- Does NOT form myelin sheaths
64
What forms grey fibers in the PNS?
Schwann cells supporting nerve fibers that do not form myelin sheaths
65
What forms the white fibers in the PNS?
Schwann cells wrapping around nerve fibers that ultimately forms layers of plasma membrane made up of myelin
66
What is the significance of myelin sheaths?
- Allows for rapid communication
- When a neuron is myelinated, it does not need to depolarize until the nodes of Ranvier, which allows for rapid conduction
67
What is the input zone of the neuron?
Receiving information at dendrites and the cell body
68
What is the summation zone of the neuron?
- Axon hillock
- Serves as the site where the nerve impulses combine
- May trigger an action potential to be conducted along the axon
69
What is the conduction zone of a neuron?
- Axon
| - Has many voltage-gated Na+ and K+ channels
70
What is the output zone of a neuron?
- Synaptic knobs of the axon
- Contains many Ca2+ channels
- Nerve impulse trigger the release of neurotransmitters
71
What are interneurons?
- Lie only within the central nervous system (CNS)
| - Conduct impulses from sensory to motor neurons
72
What is a reflex arc?
- A signal transduction route to and from the CNS
| - The electrical signal begins in receptors and ends in receptors
73
What is a three-neuron arc?
1. Sensory receptor sends message to CNS (afferent)
2. Reaches interneuron
3. Interneurons elicit outgoing (efferent) response from motor neuron
74
Differentiate nerves and tracts.
- Both are nerve fibers that are bundled into fascicles
- Nerves: within the PNS
- Tracts: within the CNS
75
Why can damage to nervous tissue be permanent?
- Since mature neurons are incapable of cell division
- Neurons in PNS have little capacity to repair themselves
- Neurons in CNS have no capacity to repair themselves
76
In what scenarios can nerve fibers be repaired?
- If the damage is not extensive
- The cell body and neurilemma are intact
- If scarring has not occured
77
What is the neurilemma?
Schwann cell cytoplasm surrounding the nerve fiber
78
How was a laboratory capable of demonstrating long-term neuronal survival after implantation to facilitate sciatic nerve regeneration?
- Grew artificially stretched nerve tissue
- Chemically coaxed them to sprout axons, then stretched them
- Used these tissues to bridge the gap between severed nerve tissues
79
Describe a nerve impulse.
Wave of electrical fluctuation that travels along the plasma membrane
80
When is a neuron at a resting membrane potential?
When it is not conducting electrical signals
81
What promotes resting membrane potential? What is it typically?
- Slight ionic imbalance across the plasma membrane
| - -70mV
82
What is the slight excess of positive ions on a membrane's outer surface produced by?
- Ion transport mechanisms
| - Membrane's permeability characteristics
83
Is the interior or the exterior of the cell negative with respect to the outside? Why?
- Interior
- Slight excess of positively charged ions on the outside
- Slight deficiency of positively charged ions on the inside
84
Which ions are on the inside of the neuron cell membrane? Which are on the outside?
- Inside: K+, protein anions
| - Outside: Na+, Cl-
85
What is the net movement of K+ in a neuron?
There is none; the membrane potential is equal
86
What can resting membrane potential be determined by?
- K+ concentration gradient
| - Cell's permeability to K+, Na+, Cl-
87
What is the membrane of a neuron most permable to? What is the consequence?
More permeable to K+
88
What does the sodium/potassium pump do?
- Pumps 3 Na+ out
| - Pumps 2 K+ in
89
Differentiate depolarization and hyperpolarization.
- Deplarization: more positive
| - Hyperpolarization: more negative
90
What happens to the membrane potential during action potential?
1. Depolarization
2. Repolarization
3. Hyperpolarization
91
Which neurons are mechanically-gated?
- Sensory neurons
| - Physical trigger
92
Which neurons are chemically-gated?
- Most neurons
| - Respond to ligands
93
What are voltage-gated neurons?
- Changes in cell membrane potential
| - Threshold voltage varies from one channel type to anoterh
94
What are channelopathies?
Diseases caused by disturbed function of ion channel subunits or the proteins that regulate them
95
What is the permeability of the cell membrane determined in part by?
The specific membrane transport channels
96
What is trapped intracellularly in a neuron? Why?
- Anionic proteins
| - There are no channels for their exit
97
Which ion is trapped extracellulary outside of a neuron? Why?
- Chloride ions
| - They are repelled by the protein anions inside the cell
98
What is the consequence of closing Na+ ion channels?
- Prevents Na+ from moving in
| - Prevents depolarization
99
What are the only ions that can move efficiently across a cell membrane?
- Positive ions
| - Sodium and potassium
100
In a resting neuron, many of the __ channels are open, but the __ are closed.
K+, Na+
101
What is an action potential?
- Change in resting membrane potential
| - Nerve impulse (electrical signal from one neuron to another cell)
102
Describe simply the mechanism that produces an action potential.
1. An adequate stimulus triggers stimulus-gated Na+ channels to open
2. Na+ diffuses rapidly into the cell
3. Depolarization
103
What do local potentials cause?
Slight shift away from the resting membrane in a specific region of the plasma membrane
104
When does excitation occur?
When Na+ channels are opened, allowing Na+ to travel into the neuron, and depolarization occurs
105
When does inhibition occur? What is it called?
- When a stimulus triggers the opening of additional K+ channels
- K+ diffuses out of the cell
- Results in hyperpolarization (more negative)
106
Where is the threshold potential determined? What is it?
- At the summation zone
| - The minimum magnitude of a voltage fluctuation that will trigger the opening of a voltage-gated channel
107
What stimuli can allow gated Na+ channels to open?
- Chemical message
| - Electrical message from adjacent neuron via gap junction
108
What is the typical threshold potential?
-59mV
109
What does this mean: the action potential is an all-or-none response?
If local depolarization fails to reach -59mV, the voltage-gated Na+ channels do NOT open
110
Why is the same magnitude of action potential always reached?
Because voltage-gated Na+ channels stay open for only about 1 millisecond before they automatically close
111
What mechanisms are involved in generating the resting membrane potential?
- Selective membrane permeability
- Promoting a slight ionic imbalance across the neuron's plasma membrane
- Sodium and potassium pumps
112
```
Clusters of neuron cell bodies located outside the CNS are called
A) centers
B) ganglia
C) nuclei
D) nerves
```
B) ganglia
113
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Which functional division of the nervous system includes the SNS and ANS?
A) sensory
B) motor
C) central
D) peripheral
```
B) motor
114
Which effectors are innervated by visceral motor neurons?
A) cardiac muscle, smooth muscle, and glands
B) somatic effectors other than skeletal muscle
C) skeletal muscle, skin, and joints
D) interneurons of the CNS
A) cardiac muscle, smooth muscle, and glands
