Skeletal muscle contraction 2

Question 1

load

Answer 1

the force exerted onto a muscle by an object

Question 2

muscle tension

Answer 2

the force exerted onto an object by a muscle

Question 3

isotonic contraction

Answer 3

tension > load
muscle shortens

sarcomeres shorten more but because elastic element s are already stretched, the entire muscle must shorten.

Question 4

isometric contraction

Answer 4

tension = load
muscle length remains constant
creates force without load movement

muscle has not shortened, sarcomeres shorten generating force but elastic elements stretch allowing the muscle length to remain the same.

Question 5

eccentric contraction

Answer 5

tension < load

muscle lengthens

Question 6

spatial summation

Answer 6

increase in the activity of axons providing input to lower motor neurons

size principle of motor recruitment:
increase in tension due to recruitment of motor units in fixed order. smallest motor units first (smaller soma) and then the larger motor units generating greater tension.

Question 7

temporal summation

Answer 7

increase in AP activity coming from rapid stimuli from same neuron in rapid succession prior to full relaxation of the previous contraction.

elastic elements partially stretched and when next stimulus comes in rapid succession then elastic elements stretched further generating greater tension.

Question 8

tetanic summation

Answer 8

form of temporal summation where succession of APs is so rapid that it results in a fusing of force peaks and a smooth and sustained muscular force is generated.

Question 9

Type I Fibres

Answer 9

Slow oxidative fibres that are tonically active for long periods of time.
composed of small red muscle fibres, red colour due to presence of myoglobin.
they generate a small force, contract slowly, fatigue resistant.
use oxidative aerobic glycolysis to generate energy.
slow myosin ATPase activity.
they have very rich blood supply, many mitochondria, aerobic enzymes.

Question 10

Type IIa fibres

Answer 10

fast oxidative glycolytic fibres (FOG) fibres.
fast fatigue resistant. contain enzymes for both glycolytic and oxidative metabolism. generate twice the force of slow oxidative fibres.

Question 11

Type IIb fibres or Type X

Answer 11

fast twitch glycolytic fibres. largest force. pale as they do not contain much myoglobin and generate energy anaerobically via glycolysis. use fast type metabolising myosin ATPase. fewer mitochondria. fast to fatigue.