0
When muscle cells are stimulated, they contract and exert a force in one direction. Stimulation of muscle cells is caused by nerve impulses carried from the central nervous system to the muscles. When the nerve impulse reaches the end of the neuron, it causes a transfer of the action potential in muscles, which leads to a contraction.
There are three types of muscle cells in the body, which are cardiac, smooth and skeletal. Cardiac muscle is only found within the heart and has its own intrinsic method for contracting, although nerves can stimulate it to speed up or slow down as necessary. Smooth muscle is found in layers surrounding the organs, and it is stimulated by the autonomic, or involuntary, nervous system. Skeletal muscle is made up of fibers and causes movement. The action potential in muscles of the skeleton is carried by the somatic, or voluntary, nervous system.
Muscle cells will not contract on their own, but must be stimulated first by a nerve impulse. The axons of neurons meet muscle cells at the neuromuscular junction. To ensure that muscle contraction is simultaneous and fast, there are many neuromuscular junctions found across a muscle. All of these neurons send impulses at the same time to initiate an action potential in muscles. Having many neuromuscular junctions for each muscle allows the body to control the force of the contraction by varying the number of units that send the impulse to the muscle.
When the action potential reaches the terminal end of the axon at a neuromuscular junction, vesicles fuse with the cell membrane to allow the release of a neurotransmitter - acetylcholine. The neurotransmitter spreads across the gap between the neuron and the muscle cell, until it reaches the sarcolemma, which is the membrane surrounding a muscle cell. Acetylcholine causes the permeability of the sarcolemma to change, so that sodium ions can enter and leave the membrane. This change in ions depolarizes the membrane and causes an action potential in muscles to be fired.
When a muscle is at rest, tropomyosin blocks the myosin binding sites found on the actin filaments. During a contraction, myosin attaches to actin and performs a type of rowing action along the actin filaments. This causes the muscle to contract. For this to occur, myosin must be able to bind to actin, so the tropomyosin must be moved.
The depolarization caused by the nerve impulse spreads across the sarcolemma and the T system - a system of tubes connected to the sarcoplasmic reticulum. Both the T system and the sarcoplasmic reticulum contain calcium ions, which are released when there is an action potential in muscles. The calcium ions diffuse throughout the muscle cell and attach to a protein called troponin, which is attached to the tropomyosin filaments found on the actin fibers. The troponin changes shape when calcium ions attach to it, which moves the tropomyosin filaments and frees the myosin binding sites along actin fibers. Myosin can now come in contact with actin and cause a muscle contraction.
Wiki User
∙ 10y ago
Wiki User
∙ 13y agoAn action potential stimulates muscle into contraction by propagating down a motor neuron. It will traverse down to the terminal end of the axon. In the terminal bouton there is a rapid influx of calcium ions which push vesicles containing neurotransmitters (ACh) outside. These little vesicles will travel across a small space (called synaptic cleft) and bind to nicotinic recepters on the motor end plate. This will cause an motor end plate potential that will continue the action potential into the T-tubules to spread the action potential throughout your muscle. The action potential activates DHPR which is a voltage gated Ca++ channel, however, it is blocked by RyR. When this happens it produces a conformational change in RyR to open and allow Ca++ out from the sarcoplasmic reticulum. Additional RyR channels that are not coupled with DHPR will also open to allow even more Ca++ out. This calcium released initiates contraction of myofibrils and are quickly pumped back into the SR.
Wiki User
∙ 10y agoDifference between ions intracellular& extracellular
Add your answer:
Earn +20 pts
When an action potential is initiated on a nerve cell membrane it radiates and is propagated in all directions from the point of initial stimulation?
Correct. The action potential is initiated at a specific point on the cell membrane called the axon hillock, and it then travels down the axon in one direction. Once initiated, it spreads along the entire length of the axon and can be transmitted to other neurons or muscle cells.
What determines if an action potential is initiated in the postsynaptic neuron?
Every time neurotransmitter is released from the presynaptic neuron it generates an excitatory post synaptic potential(EPSP) in the postsynaptic neuron. When the EPSP is greater than the threshold for excitation an action potential is generated.
Where do action potentials occur?
The spike initiation zone, also called axon hillock, is the point where the cell body of the neuron meets the axon and is the point where most action potentials are initiated.
What is the amount of stimulation required to intiate a nerve impulse called?
Neuron has to be stimulated to the point of it's threshold in order for an action potential to be initiated and transmitted
Period of reploarization of the neuron during which it cannot respond to a second stimulus?
The absolute refractory period. This period occurs after the action potential has been initiated and is a result of inactivation of the sodium channels. These sodium channels would normally open up to allow sodium influx into the cell during an action potential. The absolute refractory period occurs during an ongoing action potential and is the period in which a subsequent action potential absolutely cannot be generated.This should not be confused with the relative refractory period which occurs immediately following the absolute refractory period (during membrane hyperpolarization). During this period a subsequent action potential is possible, but more difficult to attain.
2 Define refractory period and differentiate between absolute and relative refractory periods?
refractory period is the interval between action potential , the absolute refractory period is the period in which second action potential can not be initiated but in relative refractory period the second action potential can be initiated by the more strong stimulus.
During which period can a second action potential be initiated by a larger than normal stimulus?
This the relative refractory period.
What is the absolute refractory period?
Absolute Refractory Period:It is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.ORAfter repolarization there is a period during which a second action potential cannot be initiated, no matter how large a stimulus current is applied to the neuron. This is called the absolute refractory period, and it is followed by a relative refractory period, during which another action potential can be generated
When an action potential is initiated on a nerve cell membrane it radiates and is propagated in all directions from the point of initial stimulation?
Correct. The action potential is initiated at a specific point on the cell membrane called the axon hillock, and it then travels down the axon in one direction. Once initiated, it spreads along the entire length of the axon and can be transmitted to other neurons or muscle cells.
What determines if an action potential is initiated in the postsynaptic neuron?
Every time neurotransmitter is released from the presynaptic neuron it generates an excitatory post synaptic potential(EPSP) in the postsynaptic neuron. When the EPSP is greater than the threshold for excitation an action potential is generated.
Each normal heartbeat in initiated by the?
Each heartbeat begins with an action potential generated at the sinoatrial node or simple call the SAnode.
Where do action potentials occur?
The spike initiation zone, also called axon hillock, is the point where the cell body of the neuron meets the axon and is the point where most action potentials are initiated.
What is the amount of stimulation required to intiate a nerve impulse called?
Neuron has to be stimulated to the point of it's threshold in order for an action potential to be initiated and transmitted
The Ganga Action Plan initiated?
1986
The lectin pathway for complement action is initiated by?
mannose on the parasite
What was the effect of curare on eliciting an action potential?
It creates an action potential
An electrical impulse moving down an axon is called?
This is called action potential. Action potential is the change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals.
