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36 Cards in this Set

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What is the function of the axon hillock/initial segment?
The axon hillock is the site of electrical signal generation.
What happens if an axon becomes severed? Differentiate between CNS & PNS.
Nerve function is impaired and muscle becomes innervated and undergoes atrophy. Inside the CNS, the nerve will grow, but it will be insufficient. In the PNS, the soma will develop and axon cone resulting in axon regrowth.
Differentiate between Oligodendricytes and Schwann cells.
Both cells forms myelin sheaths around the axon increasing nerve conduction. Oligodendricytes are found in the CNS, whereas Schwann cells are found in the PNS.
What are six functions of an astrocyte?
1) provide structural support
2) form the blood-brain barrier
3) guide developing axons in the embryo
4) provide glucose
5) Remove waste products
6) Regulate K+ ion levels and neurotransmitters around the synapse
What is the function of a microglial cell?
Microglia scavenge debris around neurons
What three factors allow a resting membrane potential (RMP)?
1) Na+/K+ ATPase is electrogenic
2) The presence of non penetrating negative charges inside the cell create the RMP
3)Membrane permeability to K+ is greater than Na+
What is the equilibrium potential?
Equilibrium potential is the electrical charge and concentration gradient of an ion.
What is the RMP of a neuron?
The resting membrane potential of a neuron is -70mV.
What is more permeable to the membrane Na+ or K+?
K+ is more permeable to the membrane
RMP can be altered in only excitable membranes. T/F
True
What are the three steps of an action potential? State the voltage at each step.
1)RMP = -70mV
2)Depolarization = -60mV
3)peak occurs at +40mV
4)Repolarization to -70mV
5)Hyperpolarization below -70mV
How long does it take for one action potential to occur?
approximately 4 msecs
What are the two types of synapses?
Chemical and Electrical
A synapse between a neuron and a muscle is called a ______________.
Neuromuscular junction
List all the ion channels involved in a action potential.
Voltage-Gated Calcium Channels. Na+ Receptor Channel. Na+ voltage gated cell. K+ voltage gated cell.
List all the ion channels involved in a action potential.
Voltage-Gated Calcium Channels. Na+ Receptor Channel. Na+ voltage gated cell. K+ voltage gated cell.
What happens if there isn't enough neurotransmitters available?
If there isn't enough neurotransmitters ejected into the synapse, an insufficient amount of sodium channels will become active, and the Resting membrane potential will not exceed the threshold of -60mV.
What happens if there isn't enough neurotransmitters available?
If there isn't enough neurotransmitters ejected into the synapse, an insufficient amount of sodium channels will become active, and the Resting membrane potential will not exceed the threshold of -60mV.
How are neurotransmitters released?
An action potential stimulates the opening of voltage gated calcium channels. An influx of calcium stimulates release of neurotransmitters.
The resting membrane potential inside the cell is positive. T/F
False, resting membrane potential is negative inside the cell.
How are neurotransmitters released?
An action potential stimulates the opening of voltage gated calcium channels. An influx of calcium stimulates release of neurotransmitters.
When do voltage gated Na+ open?
Voltage gated Na+ channels open when the membrane potential reaches -60mV as a result of Na+ depolarizing the membrane.
The resting membrane potential inside the cell is positive. T/F
False, resting membrane potential is negative inside the cell.
When do K+ channels open? Why?
K+ channels open when the membrane potential reaches +40mV. K+ repolarizes the membrane.
When do voltage gated Na+ open?
Voltage gated Na+ channels open when the membrane potential reaches -60mV as a result of Na+ depolarizing the membrane.
What causes hyperpolarization of the membrane?
Slow closing of voltage-gated K+ channels cause hyperpolarization of the membrane below -70mV.
What is the velocity of a myelinated axon versus a non myelinated axon.
Myelinated 175 m/sec

Non-myelinated 0.5 m/sec
When do K+ channels open? Why?
K+ channels open when the membrane potential reaches +40mV. K+ repolarizes the membrane.
What is saltatory conduction?
Saltatory conduction is when the action potential jumps from node to node on the axon
What causes hyperpolarization of the membrane?
Slow closing of voltage-gated K+ channels cause hyperpolarization of the membrane below -70mV.
What is multiple sclerosis?
Multiple Sclerosis is an autoimmune disease in which antibodies attack and degrade the myelin sheaths surrounding the axon.
What is the velocity of a myelinated axon versus a non myelinated axon.
Myelinated 175 m/sec

Non-myelinated 0.5 m/sec
What is saltatory conduction?
Saltatory conduction is when the action potential jumps from node to node on the axon
What is multiple sclerosis?
Multiple Sclerosis is an autoimmune disease in which antibodies attack and degrade the myelin sheaths surrounding the axon.
In a sarcomere, what are the components of a triad?
A triad is composed of a T-tubule and 2 lateral sacs (or lateral cisterna)
The autoimmune disease, Multiple Sclerosis, degrades the myelin sheath. There are voltage gated ion channels beneath the degraded myelin. T/F
False. There are no voltage gated ion channels below the myelin sheaths. Once myelin is degraded, the only available voltage gated ion channels are found on the nodes of ranvier. This is why nerve conduction is impaired by multiple sclerosis.