🌱 MCAT Biology Review - 4 Flashcards
(151 cards)
1
Q
What is the correct answer for the resting membrane potential question?
A
C. I and III only.
2
Q
Which statement is true regarding the action potential?
A
D. Once an action potential is triggered, an impulse of a given magnitude and speed is produced.
3
Q
What distinguishes nerves from tracts?
A
C. Nerves may carry more than one type of information; tracts can only carry one type.
4
Q
Sensory neurons are ______ and enter the spinal cord on the dorsal side.
A
afferent.
5
Q
What happens when a sensory neuron receives a stimulus that brings it to threshold?
A
It becomes depolarized, transduces the stimulus to an action potential, and releases neurotransmitters.
6
Q
When the potential across the axon membrane is more negative than the normal resting potential, the neuron is in a state of ______.
A
hyperpolarization.
7
Q
Which statement about the somatic division of the peripheral nervous system is INCORRECT?
A
D. Its pathways always involve more than two neurons.
8
Q
What is a function of the parasympathetic nervous system?
A
D. Decreasing heart rate and blood pressure.
9
Q
Which neurotransmitter is used in the ganglia of both the sympathetic and parasympathetic nervous systems?
A
A. Acetylcholine.
10
Q
In which neural structure are ribosomes primarily located?
A
B. Soma.
11
Q
What is a likely symptom of an autoimmune disease attacking voltage-gated calcium channels in excitatory neurons?
A
B. Flaccid paralysis (inability to contract the muscles).
12
Q
A neuron only fires an action potential if multiple presynaptic cells release neurotransmitters onto its dendrites. This is an example of ______.
A
summation.
13
Q
If Schwann cells die, which portion of the nervous system is NOT likely to be affected?
A
A. Central nervous system.
14
Q
What is a likely consequence of accidentally clipping a dorsal root ganglion during surgery?
A
C. I and II only (Loss of reflexes and loss of sensation at that level).
15
Q
What are the five main categories of glial cells?
A
Astrocytes, oligodendrocytes, microglia, ependymal cells, Schwann cells.
16
Q
What is the function of myelin in neurons?
A
It prevents signal loss and increases the speed of conduction.
17
Q
What are nodes of Ranvier?
A
Exposed areas of axon membrane between segments of myelin sheath.
18
Q
What happens to information transfer when myelin is absent?
A
It slows down.
19
Q
What is the synaptic cleft?
A
The small space between neurons where neurotransmitters are released.
20
Q
How are nerves in the peripheral nervous system classified?
A
As sensory, motor, or mixed.
21
Q
What is the difference between nerves and tracts?
A
Nerves can carry multiple types of information; tracts carry only one type.
22
Q
What does the term ‘demyelination’ refer to?
A
Destruction of myelin leading to slowed conduction of impulses.
23
Q
What is the role of the axon hillock in a neuron?
A
It integrates incoming signals and initiates action potentials.
24
Q
What are spiny neurons hypothesized to suffer from in Huntington’s disease?
A
Transcriptional dysregulation within the cAMP and CREB signaling cascades
This dysregulation leads to neuron degeneration.
25
What potential treatment is suggested for spiny neurons in Huntington's disease?
Targeting phosphodiesterases (PDE) that inactivate cAMP and CREB cascades
## Footnote
This approach aims to increase the activity of these signaling pathways.
26
What is TP-10 in the context of the study?
A highly specific phosphodiesterase inhibitor
## Footnote
Researchers tested its effects on neurological deficits in a mouse model.
27
What were the monitored behaviors in the TP-10 intervention group?
Loss of reflexes, loss of body weight, increased instances of clasping behavior
## Footnote
These behaviors are indicators of neurological health.
28
How is the righting reflex assessed in the R6/2 mouse model?
By laying the mice on their side and monitoring their ability to get back to the upright position
29
What does clasping behavior indicate in the context of neurodegeneration?
It is correlated with neurodegeneration
## Footnote
Increased clasping behavior suggests worsening neurological health.
30
What was the independent variable (IV) in the experiment using TP-10?
TP-10 treatment
31
What was the dependent variable (DV) in the study?
Neurological deficits reduced
32
What does Figure 1A show regarding the righting reflex?
R6/2 TP-10 retains their righting reflex longer than R6/2 Vehicle
## Footnote
Indicates potential alleviation of neurodegeneration symptoms.
33
What does Figure 1B reveal about body weight in the mice?
Both treatment and vehicle conditions show weight loss in R6/2 mice
## Footnote
TP-10 does not help with weight maintenance.
34
What does Figure 1C demonstrate about clasping behavior?
R6/2 TP-10-treated mice show later onset of clasping compared to R6/2 Vehicle
35
What is the function of astrocytes?
Nourish neurons and form the blood-brain barrier
36
What do ependymal cells do?
Line the ventricles of the brain and produce cerebrospinal fluid
37
What is the role of microglia?
Phagocytic cells that ingest and break down waste products and pathogens
38
What type of glial cells produce myelin in the CNS and PNS?
Oligodendrocytes (CNS) and Schwann cells (PNS)
39
What is the resting membrane potential of neurons?
-70 mV
40
Which ions are primarily involved in generating the resting membrane potential?
Potassium (K+) and Sodium (Na+)
41
What is the equilibrium potential of potassium?
-90 mV
42
What ion's concentration is higher outside the neuron at rest?
Sodium (Na+)
43
What is the equilibrium potential of sodium?
Around +60 mV
44
What does the Na+/K+ ATPase do?
Pumps sodium out of the cell and potassium into the cell
45
What is the primary function of the axon hillock?
Integrates excitatory and inhibitory signals to determine if an action potential is fired
46
What are the two types of summation?
Temporal and spatial summation
47
What is temporal summation?
Integration of multiple signals during a short period
48
What is spatial summation?
Additive effects based on the number and location of incoming signals
49
What is the additive effect of multiple signals known as?
Summation
## Footnote
There are two types of summation: temporal and spatial.
50
What are the two types of summation?
* Temporal summation
* Spatial summation
51
In temporal summation, how are multiple signals integrated?
During a relatively short period of time
52
What causes profound hyperpolarization of the axon hillock?
A large number of inhibitory signals firing directly on the soma
53
What is the resting potential of a neuron?
-70 mV
54
What ion channels open when the cell is brought to threshold?
Voltage-gated sodium channels
55
What is the effect of sodium ions entering the cell?
Depolarization of the cell
56
What happens when membrane potential approaches +35 mV?
Sodium channels are inactivated
57
What causes the efflux of potassium from the neuron?
Opening of voltage-gated potassium channels
58
What is hyperpolarization?
Restoration of a negative membrane potential that overshoots resting potential
59
What are the two types of refractory periods?
* Absolute refractory period
* Relative refractory period
60
What occurs during the absolute refractory period?
No amount of stimulation can cause another action potential
61
What must occur during the relative refractory period for an action potential to happen?
Greater than normal stimulation
62
What ion is primarily involved in restoring the resting potential after an action potential?
Na+/K+ ATPase
63
What is impulse propagation?
The movement of an action potential down the axon
64
What is saltatory conduction?
The signal 'hops' from node to node along myelinated axons
65
How does myelin affect action potential propagation?
Increases speed by preventing dissipation of the electric signal
66
What type of transmission occurs within a neuron?
Electrical transmission
67
What type of transmission occurs between neurons?
Chemical transmission
68
What triggers the release of neurotransmitters at the synapse?
Increase in intracellular calcium
69
What are the three main mechanisms to stop neurotransmitter action?
* Enzymatic breakdown
* Reuptake by presynaptic neuron
* Diffusion out of the synaptic cleft
70
What enzyme breaks down acetylcholine?
Acetylcholinesterase (AChE)
71
What happens to serotonin after it is released into the synaptic cleft?
It can be reuptaken by the presynaptic neuron
72
What is the role of autoreceptors in neurotransmitter regulation?
Signal the presynaptic cell to stop releasing neurotransmitter
73
What is the approximate voltage of the resting membrane potential?
-70 mV
74
What is the difference between afferent and efferent neurons?
* Afferent neurons: Carry signals to the central nervous system
* Efferent neurons: Carry signals away from the central nervous system
75
What are the two divisions of the autonomic nervous system?
* Sympathetic nervous system
* Parasympathetic nervous system
76
What are the three kinds of nerve cells in the nervous system?
Sensory neurons, motor neurons, interneurons
77
What do sensory neurons transmit?
Sensory information from sensory receptors to the spinal cord and brain
78
What do motor neurons transmit?
Motor information from the brain and spinal cord to muscles and glands
79
Where are interneurons predominantly located?
In the brain and spinal cord
80
What is a mnemonic to remember the function of afferent and efferent neurons?
Afferent neurons ascend in the spinal cord toward the brain; efferent neurons exit the spinal cord
81
What are the two primary components of the nervous system?
Central nervous system (CNS) and peripheral nervous system (PNS)
82
What does the central nervous system consist of?
The brain and spinal cord
83
What is the structure of white matter in the brain?
Composed of axons encased in myelin sheaths
84
What does grey matter in the brain consist of?
Unmyelinated cell bodies and dendrites
85
What are the four regions of the spinal cord?
Cervical, thoracic, lumbar, and sacral
86
How is sensory information transmitted in the spinal cord?
Sensory neurons bring information in from the periphery and enter on the dorsal side
87
What is the role of the dorsal root ganglia?
Contains the cell bodies of sensory neurons
88
What does the peripheral nervous system include?
Nerve tissue and fibers outside the brain and spinal cord, including spinal and cranial nerves
89
What is the function of the somatic nervous system?
Controls voluntary movements and transmits sensory information
90
What does the autonomic nervous system regulate?
Heartbeat, respiration, digestion, and glandular secretions
91
What is the primary neurotransmitter of the parasympathetic nervous system?
Acetylcholine
92
What does the sympathetic nervous system activate?
The body's fight-or-flight response
93
What are the functions of the parasympathetic nervous system?
*Constricts pupils
*Stimulates flow of saliva
*Constricts bronchi
*Slows heartbeat
*Stimulates peristalsis and secretion
*Contracts bladder
94
What are the functions of the sympathetic nervous system?
*Increases heart rate
*Redistributes blood to muscles
*Increases blood glucose concentration
*Relaxes the bronchi
*Decreases digestion
*Dilates the eyes
*Releases epinephrine
95
What are the two types of reflex arcs?
Monosynaptic and polysynaptic
96
What occurs in a monosynaptic reflex arc?
A single synapse between the sensory neuron and the motor neuron
97
What is an example of a monosynaptic reflex?
Knee-jerk reflex
98
What occurs in a polysynaptic reflex arc?
At least one interneuron between the sensory and motor neurons
99
What is the pathway of neural impulses in a monosynaptic reflex?
Sensory neuron → spinal cord → motor neuron
100
What is the pathway of neural impulses in a polysynaptic reflex?
Sensory neuron → interneuron(s) → motor neuron
101
What role do interneurons play in reflex arcs?
Relay signals between sensory and motor neurons
102
What is the primary function of the nervous system?
To coordinate and regulate signals for the body
103
What is the key concept associated with the first neuron in the autonomic nervous system?
Preganglionic neuron
104
What is the second neuron in the autonomic nervous system called?
Postganglionic neuron
105
What does the vagus nerve primarily innervate?
Thoracic and abdominal cavity
106
What happens when the sympathetic nervous system is activated?
Increases heart rate and inhibits digestion
107
Fill in the blank: The nervous system is responsible for ________ interactions in the body.
appropriate
108
True or False: The sympathetic and parasympathetic nervous systems usually act in opposition to each other.
True
109
What are neurons responsible for?
Conduction of impulses
## Footnote
Neurons are highly specialized cells that conduct electrical and chemical signals.
110
How do neurons communicate?
Using electrical and chemical communication
## Footnote
Electrical communication occurs via ion exchange, while chemical communication involves neurotransmitter release.
111
What are dendrites?
Appendages that receive signals from other cells
112
What is the function of the axon hillock?
Where action potentials are initiated
113
What is the role of the synaptic bouton?
End of the axon from which neurotransmitters are released
114
What are nodes of Ranvier?
Exposed areas of myelinated axons that allow saltatory conduction
115
What is myelin?
An insulating substance that prevents signal loss
116
What cells produce myelin in the CNS and PNS?
Oligodendrocytes in CNS and Schwann cells in PNS
117
What is the resting membrane potential of neurons?
Approximately -70 mV
118
What is the function of the Na+/K+ ATPase?
Pumps three sodium ions out for every two potassium ions in
119
What is temporal summation?
Integration of multiple signals near each other in time
120
What is spatial summation?
Integration of multiple signals near each other in space
121
What happens when the threshold voltage is reached?
Voltage-gated sodium channels open
122
What occurs at the peak of the action potential?
Sodium channels are inactivated and potassium channels open
123
What is hyperpolarization?
When the neuron becomes more negative than resting potential
124
What are the three ways neurotransmitter action can be stopped?
* Enzymatic breakdown
* Reuptake
* Diffusion
125
What are the three types of neurons in the nervous system?
* Motor (efferent) neurons
* Interneurons
* Sensory (afferent) neurons
126
What does the central nervous system consist of?
Brain and spinal cord
127
What is the difference between white matter and grey matter?
* White matter: myelinated axons
* Grey matter: unmyelinated cell bodies and dendrites
128
What are the two divisions of the autonomic nervous system?
* Parasympathetic (rest-and-digest)
* Sympathetic (fight-or-flight)
129
What is a monosynaptic reflex arc?
Sensory neuron fires directly onto a motor neuron
130
What is a polysynaptic reflex arc?
Sensory neuron fires onto a motor neuron and interneurons
131
Fill in the blank: The ________ is responsible for maintaining resting membrane potential.
Na+/K+ ATPase
132
True or False: The action potential is an all-or-nothing response.
True
133
What does the parasympathetic nervous system govern?
The 'rest-and-digest' response
134
List three functions of the parasympathetic nervous system
* Slows heart rate
* Decreases blood pressure
* Promotes blood flow to the GI tract
135
What response does the sympathetic nervous system govern?
The fight-or-flight response
136
Name two effects of the sympathetic nervous system on the body.
* Increased heart rate
* Increased blood pressure
137
What neurotransmitter is released by the preganglionic neuron in both the sympathetic and parasympathetic nervous systems?
Acetylcholine
138
What neurotransmitter does the postganglionic neuron in the sympathetic nervous system usually release?
Norepinephrine
139
What neurotransmitter does the postganglionic neuron in the parasympathetic nervous system release?
Acetylcholine
140
What are three specialized structures contained in neurons?
* Dendrites
* Axons
* Axon hillock
141
What must neurons carry out as cells?
Cellular functions including protein synthesis
142
What does the cell body or soma of a neuron contain?
* Nucleus
* Endoplasmic reticulum
* Ribosomes
143
What triggers the fusion of synaptic vesicles with the neuron's membrane at the nerve terminal?
Influx of calcium
144
What occurs during exocytosis of neurotransmitters?
Neurotransmitters are released into the synapse
145
What might result from a disease that blocks the influx of calcium in neurons?
Flaccid paralysis
146
What is the term for the pattern of excitation that requires multiple instances of excitatory transmission?
Summation
147
What are the two types of summation?
* Temporal
* Spatial
148
What do Schwann cells do?
Myelinate cells in the peripheral nervous system
149
What does the dorsal root ganglion contain?
Cell bodies of sensory neurons only
150
What happens if a dorsal root ganglion is disrupted?
Loss of sensation at that level
151
What do reflexes rely on that are part of the dorsal root ganglion?
Sensory afferents
