Fast solutions for complex problems

What is the minimum stimulus that causes contraction?

*Threshold Stimulus: The minimum stimulation required to cause a muscle contraction.

What is the stimulus for contraction?

1. A Muscle Contraction Is Triggered When an Action Potential Travels Along the Nerves to the Muscles. Muscle contraction begins when the nervous system generates a signal. The signal, an impulse called an action potential, travels through a type of nerve cell called a motor neuron.

What is the minimum stimulus which can evoke a response?

Threshold: The minimum stimulus which can evoke a response. Recruitment: A stronger response than threshold because additional motor units join in to generate an increase in tension.

What directly triggers contractions?

The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin. As soon as the actin-binding sites are uncovered, the high-energy myosin head bridges the gap, forming a cross-bridge.

What is an all or nothing response?

The all-or-none law is a principle that states that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. Essentially, there will either be a full response or there will be no response at all for an individual neuron or muscle fiber.

Why didn’t a finger twitch occur at a lower stimulus current?

Why didn’t a finger twitch occur at a lower stimulus current? Above a certain stimulus current, the amplitude of the finger twitch no longer increases.

What are the 3 stages of muscle contraction?

The contraction generated by a single action potential is called a muscle twitch. A single muscle twitch has three components. The latent period, or lag phase, the contraction phase, and the relaxation phase.

What happens if the stimulus for muscle contraction is stopped?

Relaxation: Relaxation occurs when stimulation of the nerve stops. Calcium is then pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. Actin and myosin return to their unbound state causing the muscle to relax.

In which condition are stimuli are so frequently that the muscle Cannot relax?

This phenomenon is called wave summation. Eventually the frequency of action potentials would be so high that there would be no time for the muscle to relax between the successive stimuli and it would remain totally contracted, a condition called tetanus.

Why does varying stimulus affect twitch force?

Question: Why does varying the stimulus strength affect the twitch force? Answer: With stronger stimuli, more nerve fibers are stimulated and therefore more motor units are recruited.

What are the four phases of muscle contraction?

Depolarisation and calcium ion release. Actin and myosin cross-bridge formation. Sliding mechanism of actin and myosin filaments. Sarcomere shortening (muscle contraction)

Why is calcium needed for muscle contraction?

Calcium’s positive molecule is important to the transmission of nerve impulses to the muscle fiber via its neurotransmitter triggering release at the junction between the nerves (2,6). Inside the muscle, calcium facilitates the interaction between actin and myosin during contractions (2,6).

How does the sensory nervous system affect muscle contraction?

Sensory nervous system information : For example, a sensory neuron (nerves that detect stimuli like pain or how heavy something is) provides feedback to the brain indicating that a muscle is injured while you are trying to lift a heavy weight and consequently the impulse to that muscle telling it to contract is stopped.

Where does the end process of muscle contraction occur?

This process occurs simultaneously in all sarcomeres, the end process of which is the shortening of all sarcomeres. Troponin is a complex of three proteins that are integral to muscle contraction. Troponin is attached to the protein tropomyosin within the actin filaments, as seen in the image below.

How are actin and myosin involved in muscle contraction?

Muscle contraction: Calcium floods into the muscle cell binding with troponin allowing actin and myosin to bind. The actin and myosin cross bridges bind and contract using ATP as energy (ATP is an energy compound that all cells use to fuel their activity – this is discussed in greater detail in the energy system folder here at ptdirect).

How does the sliding filament theory of muscle contraction work?

In summary the sliding filament theory of muscle contraction can be broken down into four distinct stages, these are; 1. Muscle activation: The motor nerve stimulates an action potential (impulse) to pass down a neuron to the neuromuscular junction. This stimulates the sarcoplasmic reticulum to release calcium into the muscle cell.