BMS 108 Ch. 12 Skeletal Muscle Part 2

Question 0

How are the categories divided?

Answer 0

Divided on the basis of contraction speed and resistance to fatigue.

Question 1

What are the two general types of muscle fibers?

Answer 1

slow-twitch and fast-twitch

Question 2

What are some characteristics of slow twitch fibers? What type? Example of a predominantly slow-twitch muscle?

Answer 2

Slow twitch rate; red in color, low glycogen content; high resistance to fatigue, lots of capillaries & myoglobin, aerobic respiration and high oxidative capacity

Type I

Soleus

Question 3

What are some characteristics of fast-twitch fibers? What type? Example of a predominantly fast-twitch muscle?

Answer 3

Fast twitch rate; white (Type IIx) or light red (Type IIa) in color, high glycogen content; lower resistance to fatigue, few capillaries & myoglobin, anaerobic respiration and high (IIa) and low (IIx) oxidative capacity

Type IIa and IIx

Gastrocnemius (IIa) and extraoccular (IIx)

Question 4

Can exercise alter muscle fiber types?

Answer 4

Yes, it can alter Type IIa and IIx but not Type I

Question 5

What is myoglobin?

Answer 5

An oxygen storage molecule in a muscle fiber.

Question 6

Does ATPase have the same rate of breaking ATP in all three muscle types?

Answer 6

no

Question 7

What causes muscle fatigue?

Answer 7

1. Depletion of muscle glycogen
2. Accumulation of extracellular K+ (like Potassium Chloride in Frog Heart experiment)
3. Reduced ability of SR to release CA++

Question 8

Different kinds of exercise strain cause different types of __________.

Answer 8

fatigue

Question 9

What causes central fatigue?

Answer 9

Changes in the CNS (motor neurons) rather that fatigue in muscles themselves.

Question 10

How are cardiac muscle cells different from skeletal muscle cells?

Answer 10

Brached fibers, striated, one or two nuclei, gap junctions

Question 11

Where do we have smooth muscle?

Answer 11

intestines, stomach, uterus, bronchioles, esophagus

Question 12

How is smooth muscle different than skeletal muscle?

Answer 12

No sarcomeres, gap junctions, actin filaments are anchored to dense bodies similar to z-discs, contractions based on graded depolarizations (rarely full APs)

Question 13

Describe the steps of smooth muscle contraction.

Answer 13

1. Activation - ANS (initiate or modulate), pacemakers, myogenic (responds to stretch), hormones
2. Depolarization (with or without APs) - opens graded VG Ca++ channels in sarcolemma
3. ECF is main Ca++ source&raquo_space; Ca++ entry
4. Ca++ binds with calmodulin and sets off a series of biochemical reactions
5. Phosphoralization of myosin heads as the trigger that allows contraction
6. ATP at ATPase on myosin heads
7. Ca++ ATPase to pump Ca++ back into ECF to end contraction

Question 14

Smooth muscle is divided into single unit and multiunits. Which is more common?

Answer 14

single unit

Question 15

What are some unique characteristics of single unit smooth muscle?

Answer 15

Gap junctions and pacemaker cells

Question 16

Multiunit smooth muscle requires nerve stimulation by the _____.

Answer 16

ANS

Question 17

In multiunit smooth muscle is innervated using synapses called _________.

Answer 17

varicosities