The efferent division of the peripheral nervous system innervates which four cells?
Where are neurotransmitters that are ready for release stored?
The site of intercellular communication between a neuron and another cell is the...
The myelin sheath that covers many CNS axons is formed by...
The myelin sheath of axons in the peripheral nervous system is formed by...
Neuron's Resting Potential
- Chemical and electrical forces both favor sodium ions entering the cell. - Potassium ions are repulsed by positive charges outside the cell. - Potassium ions are attracted to the negative charges inside the cell. - Chemical forces tend to drive potassium ions out of cell.
Ion channels that are constantly permeable and are found everywhere on the axolemma.
A stimulus that opens gated sodium channels in the axon membrane.
Sodium and Depolarize
If the permeability of a resting axon to sodium ion increases, inward movement of ___________ increases and membrane will _____________.
Neuron Resting Potential
- Membrane permeability for potassium ions greater than sodium ions - Diffusion of potassium ions out of cell - Interior of plasma membrane has excess of negative charges. - Diffusion of sodium ions into cell
- Membrane slowly loses capacity to generate action potentials. - Intracellular concentration of Na increases - Neuron will slowly depolarize - Inside of membrane will have a resting potential that is more positive than normal. These cause a failed function of the...
If potassium permeability of resting neuron increases above resting permeability, what effect will this have on the transmembrane potential? Inside becomes more....
Ion Movement Across Plasma Membrane
- ATP dependent ion pumps (Na/K pump) - Passive or leak channels - Voltage-gated channels (action potential) - Chemically-gated channels (neuromuscular transmission)
Chemically-Regulated Potassium Channel
If neurotransmitter acetylcholine (ACh) causes inhibition of postsynaptic neuron- what type of membrane channel did ACh bind?
A stimulus that changes a postsynaptic neuron's membrane from resting potential to -85 mV is an....
If the axolemma were to become more permeable to potassium ions at rest, then what would be required to cause an action potential?
Action Potential Generation
1. Graded depolarization brings an area of excitable membrane to threshold. 2. Sodium channel activation occurs. 3. Sodium ions enter cell and depolarizes. 4. Sodium channels are inactivated. 5. Voltage-gated K channels open & K moves out of cell, initiating repolarization. 6. Na channels regain normal properties. 7. Temporary hyperpolarization occurs.
- During depolarization phase, membrane potential becomes positive. - After-hyperpolarization phase, membrane potential reaches K equilibrium potential. - During repolarization phase, Na channels close and K channels open. - Repolarization occurs as K ions leave axon
How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate by closing their inactivation gates? It would...
Repolarization of a Neuron
During this time potassium ions move out of the cell.
If a chemical prevented the opening of voltage-regulated Na+ channels, it would affect the function of a neuron because the neuron would only be capable of producing...
Action Potential Threshold
It is more positive than the resting potential.
Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons? The axon would be unable to generate....
Greatest rate of impulse conduction is a myelinated fiber of...
Among myelinated neurons the rapid impulse conduction from "node" to "node" is called...
A neuron that receives neurotransmitter from another neuron.
The ion that triggers the vesicular transport exocytosis of acetylcholine into the synaptic cleft is...
Acetylcholine and Nicotinic
Cholinergic synapses release the neurotransmitter _______ which bind to _______.
Transmission at a Cholinergic Synapse
1. Action potential depolarizes synaptic terminal at presynaptic membrane. 2. Calcium ions enter synaptic terminal. 3. ACh releases from storage vesicles by exocytosis. 4. ACh binds to postsynaptic membrane receptors. 5. Chemically-gated Na channels on postsynaptic membrane activate. 6. Calcium ions are removed from cytoplasm of synaptic terminal. 7. Acetylcholinesterase hydrolyzes ACh 8. Synaptic terminal reabsorbs choline.
If chemically-gated sodium channels in postsynaptic membrane were completely blocked, then the _________ ________ would fail.
Neurotransmitter and Postsynaptic
The Quantity of Neurotransmitters Released, Nature of Neurotransmitter, Frequency of Neurotransmitter Release, and Characteristics of Receptors, depend on the _________ effect on __________ membrane.
Stimulation of Cholinergic Receptors
Sodium ions enter the postsynaptic neuron by the...
If the axon terminal of a motor neuron suddenly became permeable to calcium ions, then the motor end plate will develop...
Adrenergic synapses release this neurotransmitters...
Drug Effect on Synaptic Function
- Interferes with neurotransmitter synthesis - Interferes with neurotransmitter reuptake - Blocks neurotransmitter binding to receptors - Prevents neurotransmitter inactivation.
After acetylcholinesterase acts, the synaptic terminal...
What happens to a postsynaptic neuron when chemically-regulated sodium channels are open and sodium is diffusing into the cell?
Presynaptic Facilitation by Serotonin
Calcium channels in presynaptic membrane remaining opened longer causes...
When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?
Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated....
The period after an initial stimulus when a neuron is not sensitive to another stimulus is the...
An excitatory neurotransmitter secreted by somatic motor neurons innervating skeletal muscle is...
The substance released at axonal endings to propagate a nervous impulse is called a ....
An inhibitory postsynaptic potential (IPSP) is associated with....
In classic neurobiology, the part of the neuron which normally receives stimuli is called a ....
Negatively and Sodium
In what way does the interior surface of a cell membrane of a resting (non conduction) neuron differ from the external environment? The interior is _______charged and contains less ________.
- AKA postsynaptic potentials - Can form on receptor endings - Short-lived - Brief events occurring locally on discreet portions of membrane.
True or False: The all-or-none phenomenon as applied to nerve conduction states that the whole nerve must be stimulated for conduction to take place.
True or False: During depolarization, the inside of the neuron's membrane becomes less negative.
True or False: Strong stimuli causes the amplitude of action potentials generated to increase.
True or False: Action potentials can be generated by virtually all cells of the body because all cells possess cell membranes.
True or False: A graded potential that is the result of a neurotransmitter released into the synapse between two neurons is called a postsynaptic potential.
True or False: Large-diamete nerve fibers conduct impulses much faster than small-diameter fibers.
True or False: In myelinated axons the voltage-gated sodium channels are concentrated at the nodes of Ranvier.
True or False: A stimulus traveling toward a synapse appears to open calcium channels at the presynaptic end, which in turn promote fusion of synaptic vesicles to the axonal membrane.
True or False: Temporal summation occurs when the postsynaptic neuron is being stimulated by a large number of terminals from the same or different neurons at the same time.
True or False: Voltage is always measured between two points (Ex. inside the cell membrane vs. outside the cell membrane) and may be called the potential between these two points.