Muscle Contractions

Question 1

Motor Neuron Pool

Question 2

Muscle Fibers

Answer 2

Slow twitch (Type I)
Fast twitch (Type II)
- Fast twitch intermediate

Question 3

Slow twitch

Answer 3

Type I
Does not fatigue easily (resistant)
Red (myoglobin)
Metabolism: Oxidative
Mitochondria: High
Glycogen: Low

Question 4

Fast twitch intermediate

Answer 4

Type II a
Resistant to fatigue
Has less myoglobin compared to slow twitch
Metabolism: Oxidative
Mitochondria: Higher than Slow twitch
Glycogen: High

Question 5

Fast twitch

Answer 5

Type II b
Fatigable
White(low myoglobin)
Metabolism: Glycolytic
Mitochondria: Few
Glycogen: Higher than intermediate

Question 6

Muscle Contraction

Answer 6

Step 1:motor neuron sends signal to motor end plate (check)
Step 2: Release of acetylcholine
Step 3: ACh binding at the motor end plate
Step 4: Appearance of an action potential in the sarcolemma
Step5:Return to initial state

Question 7

Release of acetylcholine

Answer 7

Step 2 in muscle contraction
Vesicles in the synaptic terminal fuse with the neuronal membrane and dump their contents into the synaptic cleft

Question 8

ACh binding at the motor end plate

Answer 8

Step 3 in muscle contraction
The binding of the ACh to the receptors increases the membrane permeability to sodium ions.
Sodium ions then rush into the cell.

Question 9

Appearance of an action potential in sarcolemma

Answer 9

Step 4 in muscle contraction
An action potential spreads across the surface of the sarcolemma. While this occurs, AChE breaks down the ACh

Question 10

Return to initial state

Answer 10

Step 5 in muscle contraction
If another action potential arrives at the NMJ, the cycle begins again at step 1

Question 11

Steps in initiating skeletal muscle contraction

Question 12

Steps in skeletal muscle relaxation

Question 13

Sliding filament mechanism

Answer 13

1: ATP binds to myosin head, causing the dissociation of the actin-myosin complex
2: ATP is hydrolyzed, causing myosin heads to return to their resting conformation
3: A cross-bridge forms and the myosin heads binds to a new position on actin
4: P is released. Myosin heads change conformation, resulting in the power stroke. The filaments slide past each other
5: ADP is released

Question 14

Termination of contraction

Answer 14

1:Na-Ca exchanger and Ca2+ pump in the plasma membrane both extrude Ca 2+ from the cell

2: Ca2+ pump sequesters Ca2+ within the sarcoplasmic reticulum

3: Ca2+ is bound the sarcoplasmic reticulum by calreticulin and calsequestrin

Question 15

Twitch

Answer 15

twitch duration varies depending on the muscle
One contraction= twitch

Question 16

Tetanus

Answer 16

Action potential is sustained and the muscle is contracting again and again.
Multiple twitches

Question 17

Unfused Tetany

Answer 17

Individual muscle twitch contractions can be recognized

Question 18

Fused Tetany

Answer 18

Individual muscles twitch contractions can not be seen

Question 19

Summation

Answer 19

Recruitment or spatial summation

Temporal summation
- unfused tetany

Question 20

Isometric Contraction

Answer 20

Constant length during contraction
- muscles dealing with posture

Question 21

Isotonic Contraction

Answer 21

Length changes during contraction

Question 22

Smooth Muscle Contraction

Answer 22

CB

Question 23

Action Potential and slow waves in Smooth Muscles

Question 24

Cross bridge cycling in smooth Muscles