The minimal stimulus needed to cause a depolarization of the muscle plasma membrane?
At threshold stimulus sodium ions move into or out of the cell to bring about membrane depolarization?
The nerve impulse causes the release of acetylcholine from the motor end plate. This causes the depolarization of the membrane of the adjacent muscle cell. Depolarization triggers the release of calcium ions from the sarcoplasmic reticulum inside the muscle cell. In the presence of ATP, the high calcium level causes the myosin heads to bend, dragging actin filaments towards the middle of the unit of contraction.
Pacemaker potentials are automatic potentials generated and are exclusively seen in the heart. They arise from the natural "leakiness" of the membrane that pacemaker cells have, resulting in passive movement of both Na+ and Ca2+ across the membrane, rising the membrane potential to about -40mV. This results in a spontaneous depolarization of the muscle that has a rise in the curve that is nowhere near as steep as the action potential of other cells. Upon…
The threshold stimulus is the stimulus required to create an action potential. So any stimulus under this level will not cause muscle contraction, while a stimulus above this level will cause the muscle to contract. The higher the stimulus the more muscle fibers are recruited, and thus the higher the response.
All messaging along the neurons are driven at first by a stimulus. This can be chemical or electrical. This begins a change in the neuronal cell membrane called depolarization. One small section is depolarized and that causes the next small section to become depolarized. The first section is repolarized in nanoseconds so that the stimulation can be repeated. This "flipping of the charge" travels rapidly to the effector. This could be a muscle. This entire…
When a neuron is activated by a stimulus, it's plasma membrane instantly becomes permeable to Na+ so these ions quickly diffuse into the neuron as Na+ channels close, the inward flow of Na+ for a brief instant causes the inside of the plasma membrane to become positively charged and the outside to become negatively charged at the point of stimulation, this switch in polarity is called depolarization which is considered the nerve impulse... depolarization is…
Hyper polarization of the skeletal muscle cells is the opposite of depolarization. It results from increase in the flow of potassium out of the cells with simultaneous flow of chloride into the cells giving the membrane a net negative charge. It is an essential mechanism for the contractile function of the muscles in our body.
How does increasing the stimulus frequency affect the force developed by the isolated whole skeletal muscle?
Increasing the stimulus to an isolated muscle increases the strength of a contraction. A muscle begins to contract when the stimulus is given; however, if the muscle does not finish contracting before the next stimulus hits, then the force of the contraction will increase to finish the contraction. This is known as wave summation.
Electrical excitation of a muscle fiber. Skeletal muscle fibers (cells) can be stimulated either by amotor neuron in the body or by a voltage stimulator in the lab. Stimulation given by either method results in a depolarization of the sarcolemma. If the depolarization reaches threshold, an action potential (electrical signal) is initiated.