Isometric Contraction

Question 1

Name and describe the 3 characteristics of an isometric muscle twitch.

Answer 1

Latent Period–initiation of stimulus and beginning of force generated by muscle. Ca++ is released from the sarcoplasmic reticulum into the sarcoplasm.
Contraction Phase–Time between the end of the latent period and peak muscle tension development. Ca++ is binding to troponin and crossbridge cycling rate increases.
Relaxation Phase–Peak tension to end of contraction. Ca++ is pumped back into the sarcoplasmic reticulum and crossbridge cycling rate decreases.

Question 2

Define Threshold Stimulus.

Answer 2

It is the minimal amount of electrical stimulus needed to fire muscle fibers to create a small twitch with a low amount of tension.

Question 3

What is Maximal Stimulus?

Answer 3

The weakest stimulus at which all muscle motor unites are being stimulated. An increase in stimulus strength will not stimulate greater tension.

Question 4

define Recruitment. and how it works

Answer 4

As stimulus strength is increased, more muscle motor units are called on to generate greater strength. Motor unit recruitment is determined by an action potential on motor neurons from smallest to largest.

Question 5

Define Contractile component.

Answer 5

Sarcomeres in series.

Question 6

Define Series elastic component,

Answer 6

All connective tissues related to muscle tissue.

Question 7

How do Contractile and Series Elastic Components work together in a isometric contraction.

Answer 7

As the sarcomeres shorten, they stretch the series elastic component which passively generates force as it lengthens. Resulting in a no change in muscle length.

Question 8

Active Tension

Answer 8

Tension produced by shortening of the sarcomeres.

Question 9

Passive Tension.

Answer 9

Elastic force that results from stretching the series elastic component.

Question 10

Define Summation.

Answer 10

Occurs When multiple stimuli are added to a muscle before a previous action potential has been completed. In the initial twitch, some energy is lost in series elastic component stretching. If that is still stretched when the next stimulus arrives, greater force can be generated by the muscle because force is transferred to muscle more efficient.

Question 11

Define Tetanus

Answer 11

Contraction produced by a high stimulus frequency characterized by individually distinguishable twitches of indistinguishable twitches of increasing peak tension to reach a plateau.

Question 12

If the stimulus frequency is increased to a very high rate, muscle tension will increase rapidly, in a smooth patten, until a plateau is reached. What is it?

Answer 12

Fused tetanus.

Question 13

Define Fatigue

Answer 13

A decline in the muscle’s ability to maintain a constant force of contraction during long-term, repetitive stimulation.

Question 14

What is Muscle shortening under load?

Answer 14

Concentric contraction

Question 15

What is lengthening under load?

Answer 15

Eccentric Contraction.

Question 16

What are the three phases of the Isotonic twitch?

Answer 16

Latent period–the period where the muscle is developing tension without changing length
Plateau Phase–period where muscle is changing length at constant tension. (Tension = Load)
Relaxation Phase–Period when tension declines to zero following plateau phase.

Question 17

How do the three phases of Isotonic Twitch change over time as the load increases?

Answer 17

1. The Latenet period increases with increasing load.
2. The time of changing muscle length (plateau) decreases with in increasing load.
3. Shortening velocity decreases with increasing load.