Chapter 7 (Part 1) - The Nervous System
Which of the following describes the role of astrocytes in the formation and function of the blood-brain barrier? -Induce tight junctions between capillary endothelial cells -Produce carrier proteins and ion channels -Produce enzymes to destroy toxic substances -All of the choices are correct.
All of the choices are correct.
What structures are involved in electrical synapses?
Gap junctions
What is the function of acetylcholinesterase?
It catalyzes hydrolysis of ACh to remove it from the synaptic cleft.
Acetylcholine has which effect on the postsynaptic neuron?
Ligand-gated sodium ion channels open and sodium diffuses inward.
If acetylcholine is not removed from the receptor, can a new action potential stimulate the muscle cell? YES or NO
NO
When a neurotransmitter binds to a nicotinic receptor, the ion channel opens and ________.
Na+ diffuses into and K+ diffuses out of the cell simultaneously
A neuron that has just propagated an action potential is quickly stimulated again, but no response occurs. This neuron must have been in the __________when the second stimulus arrived.
absolute refractory period
The neurotransmitter at the neuromuscular junction is ___________.
acetylcholine
Which type of neuroglia supports the metabolic needs of the blood-brain barrier?
Astrocytes
At the neuromuscular junction, acetylcholine __________.
diffuses across the synaptic cleft and binds to acetylcholine receptors on the postsynaptic muscle fiber
When K⁺ diffuses out of the cell, the cell becomes ____________ depolarized.
less
When Na⁺ diffuses into the cell, the cell becomes ____________ depolarized.
more
Na+ diffusing into the cell causes more Na+ gates to open, which is a ____________ feedback loop.
positive
Repolarization occurs because __________.
potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close.
Normally, sodium and potassium leakage channels differ because ___________________.
sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell
When threshold is reached in a neuron, depolarization occurs with the same amplitude of potential change. This is known as ________.
the All-or-None principle
A resting membrane potential of -70 mV indicates that the ________________.
charges lining the inside of the plasma membrane are negative compared to the charges lining the outside
What is the effect of the neurotransmitter at the neuromuscular junction?
It causes ligand gated sodium channels in the muscle fiber to increase their permeability to sodium, which depolarizes the postsynaptic membrane.
What is the purpose of acetylcholinesterase on the postsynaptic membrane ________.
It is an enzyme that breaks acetylcholine down into acetic acid and choline
Check all that apply as characteristics of myelinated axons.
-Myelinated axons utilize fewer voltage-gated channels than unmyelinated axons of the same length and diameter; -Myelinated axons are more energy efficient than unmyelinated axons; -Myelinated axons would be unaffected by diseases that attack the CNS.
Check all that apply. If astrocytes were damaged or lost, how would this impact CNS function? -An individual may experience difficulty initiating movement, or slowness in movement. -The composition of cerebral spinal fluid would be very similar to blood plasma. -Production of CSF would be diminished. -Action potentials could not be generated in the CNS. -Toxic substances could easily build up in the brain.
-The composition of cerebral spinal fluid would be very similar to blood plasma. -Toxic substances could easily build up in the brain.
Check all that apply as characteristics of oligodendrocytes. -They are a type of neuroglia found in the PNS -They would be affected by a demyelinating disease of the PNS. -They can surround multiple axons in the CNS at the same time. -They myelinate the cell bodies of neurons in the CNS. -They contribute to the "white matter" of the brain.
-They can surround multiple axons in the CNS at the same time. -They contribute to the "white matter" of the brain.
Number the events of neurotransmitter release from the synaptic terminal in the correct order. -Voltage-gated Ca2+ channels open -Action potential reaches axon terminal -Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm -Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane -Exocytosis of neurotransmitter into synaptic cleft
1. Action potential reaches axon terminal 2. Voltage-gated Ca2+ channels open 3. Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm 4. Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane 5. Exocytosis of neurotransmitter into synaptic cleft.
Which of the following is/are a location of nicotinic ACh receptors? Autonomic ganglia Specific regions of the brain Skeletal muscle All of the choices are correct
All of the choices are correct.
Acetylcholine diffuses across the synaptic cleft and ________.
Binds to ACh receptors that open ligand-gated sodium channels
What structure(s) are present exclusively within the myelin sheath of the PNS?
Both neurilemma and sheath of Schwann are correct.
The arrival of the action potential at the presynaptic terminal causes ________.
Calcium to enter the presynaptic terminal through voltage-gated calcium channels
Acetylcholine is actively transported from the presynaptic membrane to the postsynaptic membrane. TRUE or FALSE
FALSE
Action potentials travel faster on thin, myelinated axons than on thick, myelinated axons. TRUE or FALSE
FALSE
Receptors that bind the neurotransmitter on the postsynaptic cell membrane are voltage-gated. TRUE or FALSE
FALSE
The sodium-potassium pump uses bulk transport to move the sodium and potassium ions. TRUE or FALSE
FALSE
Check all that apply. If you could modify an axon so that it transmits impulses faster than before, which of the following modifications should you make? Decrease the diameter of the axon Increase the diameter of the axon Increase the myelination of the axon Decrease the temperature in the body Increase the temperature in the body. Increase the amount of voltage gated channels within the Schwann cells
Increase the diameter of the axon Increase the myelination of the axon Increase the temperature in the body.
The increase in calcium ion concentration causes ________.
Release of acetylcholine from the synaptic vesicles into the synaptic cleft
Which of the following occurs when an action potential arrives at the presynaptic terminal?
Synaptic vessels migrate to the plasma membrane and release acetylcholine.
After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential. TRUE or FALSE
TRUE
If the postsynaptic membrane potential reaches threshold level, an action potential will be produced. TRUE or FALSE
TRUE
Nicotinic receptors are also ion channels. TRUE or FALSE
TRUE
Once threshold is reached on the postsynaptic membrane, an action potential is generated and propagated over the postsynaptic cell membrane. TRUE or FALSE
TRUE
The area between the presynaptic nerve cell and the postsynaptic muscle cell is termed the synaptic cleft. TRUE or FALSE
TRUE
An action potential arriving at the presynaptic terminal causes __________.
calcium ions to diffuse into the cell
The voltage-gated Na⁺ channels ____________ when the cell reaches +30 mV.
close
Depolarization occurs because __________.
more sodium ions diffuse into the cell than potassium ions diffuse out of it
K⁺ diffusing out of the cell has a ____________ feedback effect on the initial depolarization.
negative
The voltage-gated Na⁺ channels ____________ when the cell membrane reaches threshold level as a result of a stimulus.
open
Hyperpolarization, or after potential occurs because __________.
the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level
An action potential arriving at the presynaptic terminal causes __________.
voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell
