Muscle

Question 1

What are the major differences b/w the 3 types of muscle with regard to:

1. Striation
2. Position of nuclei

Answer 1

1. Skeletal and cardiac m. are BOTH striated, but cardiac fibers BRANCH
2. Nuclei are centrally located in fibers of cardiac and smooth m., but on the periphery of skeletal m.

Question 2

How to distinguish cardiac and smooth m.?

Answer 2

Cardiac has branched FIBERS, smooth has individual CELLS

Question 3

What are the 3 major connective tissue elements?

Answer 3

Endomysium: contains individual m. fibers

Perimysium: contains fascicles

Epimysium: contains bundles of fascicles

Question 4

What is the pink-red color of skeletal m. due to?

Answer 4

Blood and myoglobin content

Question 5

The action of skeletal m. is voluntary except for ___.

Answer 5

The diaphragm.

Question 6

What are the 2 main types of skeletal m.?

Answer 6

Fast Glycolytic (FG) and Slow Oxidative (SO)

Question 7

How are the 3 zones in a sarcomere affected during contraction?

Answer 7

I-band width dec. in contraction

A-band width remains constant during contraction

H-band width dec. in contraction

Question 8

What are the 3 subunits of Troponin?

What proteins are located in the I-band?

Answer 8

TnI (Inhibitory), TnT (Tropomyosin), TnC (Calcium);

Tropomyosin and troponin (the 3 subunits)

Question 9

What are the 4 major proteins involved in muscle contraction and what are they?

Answer 9

1. Myosin:composes thick filament containing light and heavy chains (light chain is head region)
2. Actin:major component of thin filaments (G and F actin forms, 2 F strands entwine to make a thin filament)
3. Tropomyosin:Lies in groove formed by entwined actin strands
4. Tropomysin:3 subunits (TnT, TnC, TnI)

Question 10

What is the hierarchy of muscle?

Answer 10

Filaments (eg myosin and F-actin filaments)>Fibrils (eg myofibril)>fibers (muscle fiber)>fascicles>Muscle mass

Question 11

What is the sarcolemma?

What is a T-tuble and how can you distiguish it in cardiac and skeletal m.?

Answer 11

It is the outer covering of a single muscle fiber. It invaginates to form a T-tubule. If the T-tubule is located:

At the A-I band junction its skeletal m.,

At the Z-line its cardiac m.

Question 12

What is the sarcoplasmic reticulum and how can you distiguish it in cardiac and skeletal m.?

Answer 12

It is the internal membrane system (underneath sarcolemma) and it junctions w/ the T-tuble to form:

A triad in Skeletal m.

A dyad in cardiac m.

Question 13

Name 3 distinguishing features of cardiac m.

Answer 13

1. Central nuclei
2. Branchin fibers
3. Intercalated discs

Question 14

What are the 3 junctions in the intercalated disc of cardiac tissue and their function?

Answer 14

1. Fascia adherens: anchoring sites for actin
2. Macula adherens (AKA desomosome): stop separation during contraction by joining cells via interm. filaments
3. Gap junctions: allow action potentials to spread b/w cells producing depolarization of the muscle.

Question 15

What color is smooth muscle and why?

Answer 15

It is pale b/c of minimal vascularization and low myoglobin content

Question 16

What kind of junctions are in smooth m.?

What structures are lacking in smooth m. that are present in cardiac and skeletal m.?

Answer 16

Gap junctions.

No striations, No sarcomeres, No T-tubules

Question 17

Skeletal m. is innervated by what type of neuron?

How many fibers to one neuron?

Answer 17

Motor neuron; A motor neuron innervates UP TO 100 fibers

Question 18

Which type of m. is an all or none contraction?

Answer 18

Skeletal m. (cardiac is also regulated by troponin but not all or none contraction)

Question 19

What are the 3 main differences that differentiate cardiac from skeletal muscle contraction?

Answer 19

1. Not necessarily all or none contraction
2. Intercalated discs cause depolarization from cell to cell NOT direct nerve stimulation (like skeletal)
3. Calcium induced-calcium release (not necessary in skeletal m.)

Question 20

Where are purkinje fibers located and what do they do?

Answer 20

They ar located in the inner VENTRICULAR walls of heart, BENEATH ENDOCARDIUM.

They’re specialized myocardial fibers that conduct an electrical impulse enabling the heart to contract in a coordinated fashion.

Question 21

Name 3 differentiating characteristics of SMOOTH m. contraction

Answer 21

1. Contraction regulated by autonomic innervation (like cardiac m. but not direct innervation by motor neurons like skeletal m.)
2. Slow contraction (like GI peristalsis)
3. Actin-myosin interaction mediated thru CALMODULIN, NOT TROPONIN regulation

Question 22

What happens to the nucleus during smooth m. contraction?

Answer 22

it is deformed

Question 23

The heart develops from what type of embryonic tissue?

Answer 23

Splanchnic mesoderm