Basics

Question 1

On which myofilament is troponin located?

Answer 1

Thin filament (actin)

Question 2

What is the function of the sarcoplasmic reticulum (SR)?

Answer 2

Intracellular organelle that stores calcium

Question 3

Jane was holding a tray of dirty glasses when John added an extra 5 pounds of plates. To prevent dropping the tray, Jane’s muscles increased their force of contraction through an increase in the _______.
A) length of the muscle.
B) number of motor units activated and the frequency of their activation.
C) peak intracellular calcium concentration in the muscle.
D) strength of each cross bridge interaction with myosin.

Answer 3

B) number of motor units activated and the frequency of their activation.

Question 4

Diseases affecting striated muscle cells are uncommon but are devastating and often lethal. Why?

Answer 4

Normal muscle function is required for maintenance of posture, locomotion, respiration, swallowing, and heart beat (cardiac is striated muscle).

Question 5

What filament inserts into the Z line of the sarcomere?

Answer 5

Thin filament (actin

Question 6

What filament inserts into the M line?

Answer 6

Thick filaments (myosin)

Question 7

What is the I band?

Answer 7

Thin filament (actin)

Question 8

What is the A band?

Answer 8

Thick filament (myosin)

Question 9

Which band changes in length with contraction?

Answer 9

I band shortens with contraction

Question 10

Do the sarcomeres change in length with contraction?

Answer 10

Yes. Sarcomeres shorten with contraction due to sliding of the thin and thick filaments past each other.

Question 11

If a patient is given a drug that inhibits myosin light chain kinase, the effect will be:
A. decreased diameter of the small arteries.
B. decreased airway resistance in the lung.
C. decreased heart beat.
D. decreased tone of postural muscles.

Answer 11

B. decreased airway resistance in the lung.

Question 12

A bundle of muscle contracts rhythmically and in unison even when the nerve supply is cut. The cells have poorly developed T tubules. What type of muscle is this?
A. single unit smooth muscle
B. fast twitch skeletal muscle
C. multiunit smooth muscle

Answer 12

A. single unit smooth muscle

Question 13

During an asthma attack, constriction of the bronchiolar smooth muscle restricts airflow into and out of the lung. Epinephrine is administered to restore air flow. It acts at which of the following sites?
A. alpha 1 adrenergic receptor
B. beta 2 adrenergic receptors
C. beta 1 adrenergic receptors
D. nicotinic receptors

Answer 13

B. beta 2 adrenergic receptors

Question 14

Contraction of smooth muscle relies on \_\_\_\_\_\_\_ for modulating actin-myosin interaction (cross bridge formation).
A. Na+ dependent actin phosphorylation
B. Ca++ dependent actin phosphorylation
C. Na+ dependent myosin phosphorylation
D. Ca++ dependent myosin phosphorylation

Answer 14

D. Ca++ dependent myosin phosphorylation

Question 15

Action potentials can be generated in smooth muscle cells by activating which of the following?
A. voltage gated Ca++ channels
B. voltage gated Na+ channels
C. ligand gated Ca++ channels
D. mechano gated Ca++ channels
E. A and B
F. A, C and D

Answer 15

F. A, C and D

Question 16

During phase 3 of the contractile cardiac myocyte action potential, \_\_\_\_\_\_ are open. This\_\_\_\_\_the cell.
A. Ca++ channels; repolarizes
B. K+ channels; repolarizes
C. Na+ channels; depolarizes
D. K+ channels; depolarizes
E. Ca++channels; depolarizes

Answer 16

B. K+ channels; repolarizes

Question 17

To initiate relaxation in the cardiac myocyte, Ca++ is removed from the cytoplasm by which of the following?
A. SR CaATPase
B. plasma membrane CaATPase
C. plasma membrane Na-Ca exchanger
D. SR Na-Ca exchanger
E. A and B
F. A, B and C
G. A, B, C and D

Answer 17

F. A, B and C