Answer:
Explanation:
A higher concentration of neurotransmitter above a certain threshold does not change the height of the action potential because the action potential is an all-or-nothing event. It's a rapid and brief electrical signal that travels down a neuron's axon, leading to the release of neurotransmitters at the synapse.
To understand why a higher neurotransmitter concentration doesn't affect the height of the action potential, let's delve into the molecular events that occur during an action potential:
Resting State: Neurons have a resting membrane potential, which is a difference in electrical charge between the inside and outside of the cell. This potential is maintained by ion channels in the cell membrane, primarily sodium (Na+) and potassium (K+) channels. At rest, there are more positively charged ions outside the cell than inside.
Depolarization: When a neuron receives a strong enough excitatory stimulus, it causes a brief change in the ion permeability of the cell membrane. Voltage-gated sodium channels open in response to this stimulus, allowing sodium ions to rush into the cell. This influx of positive ions depolarizes the membrane, meaning the inside of the cell becomes more positively charged compared to the outside.
Threshold: If the depolarization reaches a certain threshold, typically around -55 to -50 mV, it triggers an action potential. At this point, voltage-gated sodium channels open more widely, leading to a rapid influx of sodium ions. This is the "all-or-nothing" phenomenon – once the threshold is reached, the action potential is initiated, regardless of the strength of the initial stimulus.
Rapid Depolarization: The influx of sodium ions causes the membrane potential to become highly positive. This phase is known as rapid depolarization or the rising phase of the action potential.
Repolarization: After reaching its peak positive potential, voltage-gated potassium channels open. Potassium ions flow out of the cell, repolarizing the membrane and restoring the negative charge inside the cell.
Hyperpolarization: In some cases, the outflow of potassium ions overshoots the resting membrane potential, causing a brief hyperpolarization. This hyperpolarization is then corrected as potassium channels close and the sodium-potassium pump restores the resting ion concentrations.
Now, in terms of neurotransmitter concentration affecting the action potential height: once the action potential is triggered (step 3), the neuron goes through a cascade of events that are largely determined by the opening and closing of ion channels. The neurotransmitter concentration in the synapse influences whether the postsynaptic neuron will generate an action potential at all by contributing to the overall membrane depolarization, but it doesn't directly affect the height of the action potential once it's initiated. The action potential is a self-regenerating process, meaning that once it starts, it will proceed along the axon without losing strength, as long as the ion concentrations are maintained.
A higher concentration of neurotransmitter above the threshold does not change the height of the action potential. During an action potential, the movement of ions across the neuron's cell membrane is responsible for the changes in charge and the generation of the action potential.
During an action potential, the movement of ions across the neuron's cell membrane is crucial. At rest, the neuron maintains a negative charge inside compared to the outside, known as the resting potential. This is maintained by the selective permeability of the cell membrane and the presence of ion channels.
When a stimulus is received, the neuron undergoes depolarization. This occurs when the cell membrane becomes more permeable to sodium ions. Sodium channels open, allowing sodium ions to rush into the neuron. This influx of positive charge causes a rapid change in the neuron's charge, resulting in the generation of an action potential.
Once the action potential is generated, it propagates along the neuron. This is achieved through the opening and closing of ion channels along the neuron's membrane. As the action potential moves, sodium channels close and potassium channels open, allowing potassium ions to move out of the neuron. This repolarizes the cell membrane, restoring the negative charge inside the neuron.
The concentration of neurotransmitter above the threshold does not change the height of the action potential because the action potential is an all-or-nothing event. Once the threshold is reached, the action potential is generated with a consistent height. The concentration of neurotransmitter affects the likelihood of reaching the threshold, but once it is reached, the height of the action potential remains the same.
Learn more about neurotransmitters and action potentials here:
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Phototropism is reaction of a plant to a light stimulus. Growth of the plant or its part grow towards the light stimulus is called positive phototropism. Growth of the plant or its part away from the light stimulus is called negative phototropism. Since, the plant grows away from the sunlight (away from the light stimulus), it is negatively phototropic.
Gravitropism is reaction of a plant to gravity. Growth of the plant or its part in the same direction as gravity is called positive gravitropism. Growth of the plant or its part grow in the opposite direction of gravity is called negative gravitropism. The root is positively gravitropic (grows deeply straight down into the ground, in the same direction as gravity).
A) salt will move out of the model cell by active transport
B) salt will move into the model cell by facilitated diffusion
C) water will move into the model cell by osmosis
D) water will move out of the model cell by osmosis
Answer:
d
Explanation:
that true because the water have 1 percent of salt it in the water so the fish and the oher anmail can live in the sea
Answer:
Its C) water will move into the model cell by osmosis
Explanation:
b.A cell's genotype is determined by its DNA and its phenotype is determined by its proteins.
c.A cell's genotype is determined by its DNA and its proteins.
d.A cell's genotype and phenotype are determined by its proteins.
Answer:
A. C3!
Explanation: