Muscle Contraction

Question 1

Type I fibers are also called…

Answer 1

Slow twitch

Question 2

Type IIa fibers are also called…

Answer 2

Fast twitch intermediate

Question 3

Type IIb fibers are also called…

Answer 3

Fast twitch

Question 4

Describe the characteristics of type I fibers

Answer 4

Fatigue resistant, contain myoglobin (red), oxidative metabolism, high mitochondria count, low glycogen

Question 5

Describe the characteristics of type IIa fibers(Intermediate)

Answer 5

Fatigue resistant, lesser amt of myoglobin (red and white), oxidative metabolism, higher mitochondria, high glycogen

Question 6

Describe the characteristics of type IIb fibers

Answer 6

Easily fatigued, low myoglobin(white), Glycolytic metabolism, fewer mitochondria, high glycogen

Question 7

Describe the steps in skeletal muscle contraction (7 steps hint)

Answer 7

1) ACh neurotransmitters are released from presynaptic cleft and diffuses across the synaptic cleft; they attach to ACh receptors on the sarcolemma

2) AP is generated along sarcolemma and down the T-tubules

3) Ca2+ release from terminal cisternae of SR is triggered by AP

4) Ca2+ ions bind to troponin(TnC) causing it to move from its actin active site blocking position and exposing the binding sites

5) Contraction; the myosin cross bridges attach to actin and detach which pulls the actin filaments towards sarcomere center. ATP is releasing energy which powers this process

6) Ca2+ is removed by active transport into the SR after end of AP

7) Tropomyosin moves back to its original actin active site blocking position. Contraction ends.

Question 8

Describe the 3 steps of termination of skeletal muscle contraction

Answer 8

1) Ca2+ pump and Na-Ca exchanger on plasma membrane pump Ca2+ out of cell

2) Ca2+ pump isolated some Ca2+ in the SR

3) Ca2+ is bound in SR by calreticulin and calsequestrin

Question 9

What three phases make up a muscle twitch?

Answer 9

Latent period, contraction, and relaxation

Question 10

A muscle twitch is…

Answer 10

A contraction generated by a single AP

Question 11

Describe the latent pd

Answer 11

A 1-2msec delay from when the AP reaches the muscle until tension is observed

Question 12

The random firing of motor units is responsible for

Answer 12

Muscle tone

Question 13

What is “unfused tetany”?

Answer 13

When the stimuli frequency increases causing successive muscle contractions to blend almost appearing as a single, large contraction

Question 14

What is “complete/fused tetany”?

Answer 14

When the frequency of stimuli continues to increase causing the muscle contractions to fuse together and create one contraction

Question 15

Recruitment/spatial summation is…

Answer 15

When multiple neurons are weakly stimulated simultaneously and impulses are converted into a single, larger neuron

Question 16

Temporal summation is…

Answer 16

When a single neuron is rapidly stimulated

Question 17

Isometric contractions are when…

Answer 17

The muscle contracts but there is no change in muscle length nor any motion. When the muscle is contracted the tension is high

Question 18

Isotonic contractions are when…

Answer 18

The muscle contracts and changes length, resulting in motion.

Question 19

Describe the 7 steps of slow wave generation in smooth muscle

Answer 19

1) voltage gated Ca2+ channels open

2) AP spike occurs

3) Ca2+ influx causing increase in Ca2+ ICF conc.

4) Ca2+ dependent K+ channels open

5) slow hyperpolarization

6) voltage-gated Ca2+ channels close; Ca2+ ICF conc decreases

7) Ca2+ dependent K+ channels close

Question 20

Name the 3 types of smooth muscle APs

Answer 20

1) Spike
2) Plateau
3) Slow waves

Question 21

Describe the steps of cross bridge cycling

Answer 21

1) Ca2+ enters ECF through SR and membrane proteins

2) Ca2+ binds to and activates calmodulin

3) Activated calmodulin activates kinase

4) Contraction is stimulated by activated(PHOSPHORYLATED) myosin molecule

Question 22

How are muscle spindles arranged and what do they detect?

Answer 22

Parallel to contracting skeletal muscle; detects muscle length

Question 23

How are golgi tendon organs arranged and what do they detect?

Answer 23

Arranged in series with contracting muscle fibers, detects muscle tension

Question 24

Intrafusal muscle fibers are another name for…

Answer 24

Muscle spindles