$$T = T_{max} \times \exp\left(-\frac{(L - L_{opt})^2$}{2\$$sigma^2$$}\right)$$

Question 1

Which of the following best explains why a slightly stretched cardiac sarcomere increases Ca$$^{2+}$$ sensitivity and tension generation?

Accepted Answer

The decreased diameter reduces the distance Ca$$^{2+}$$ must diffuse, increasing cross-bridge cycling probability.

Question 2

Which equation best represents the relationship between tension and sarcomere length in skeletal muscle?

Accepted Answer

$$T = T_{max} 	imes \exp\left(-\frac{(L - L_{opt})^2$}{2\$$sigma^2$$}ight)$$

Question 3

A patient has a heart rate of 72 BPM at rest. Which branch of the autonomic nervous system is most dominant?

Accepted Answer

Parasympathetic nervous system

Question 4

Which of the following is a direct effect of acetylcholine (ACh) on pacemaker cells in the SA node?

Accepted Answer

Closing HCN channels and opening K$$^+$$ channels

Question 5

Which of the following best describes the effect of sympathetic stimulation on pacemaker activity?

Accepted Answer

Cells reach threshold more rapidly due to increased Na$$^+$$ and Ca$$^{2+}$$ conductance.

Question 6

Which formula best represents the effect of cAMP on protein kinase activation in cardiac muscle?

Accepted Answer

$$PKA = k 	imes [cAMP]$$

Question 7

Which of the following is NOT a characteristic of smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle contains troponin and T-tubules.

Question 8

Which of the following smooth muscle types is most likely found in the iris and ciliary body of the eye?

Accepted Answer

Multiunit smooth muscle

Question 9

Which mechanism is responsible for Ca$$^{2+}-$$induced Ca$$^{2+}$$ release in smooth muscle?

Accepted Answer

Activation of ryanodine receptors (RyR) by incoming Ca$$^{2+}$$

Question 10

Which of the following best describes the electrical activity in unitary smooth muscle?

Accepted Answer

Action potentials propagate via gap junctions, allowing coordinated contraction.

Question 11

A phasic smooth muscle that cycles between contraction and relaxation is most likely found in which organ?

Accepted Answer

Intestine

Question 12

Which of the following is a property of multiunit smooth muscle?

Accepted Answer

Is electrically isolated, allowing finer motor control

Question 13

Which equation best describes the graded response of smooth muscle membrane potential to increasing stimulus strength?

Accepted Answer

$$\Delta V_m = k 	imes S$$

Question 14

Which of the following is true regarding the effect of parasympathetic stimulation on the SA node?

Accepted Answer

It decreases conduction velocity at the AV node.

Question 15

Which of the following is a real-world example of tonic smooth muscle?

Accepted Answer

Sphincter that relaxes to allow material to pass

Question 16

Which of the following is NOT a mechanism for increasing cytosolic Ca$$^{2+} in $$smooth muscle?

Accepted Answer

Ca$$^{2+}$$ entry through Na$$^+$$ channels

Question 17

Which of the following best describes the effect of a negative shift in maximum diastolic potential in pacemaker cells?

Accepted Answer

Cells require more time to reach threshold, decreasing heart rate.

Question 18

Which of the following is a characteristic of smooth muscle cells seen in histological sections?

Accepted Answer

Spindle-shaped, uninucleate cells

Question 19

Which of the following best describes the effect of beta-1 adrenergic receptor activation in cardiac muscle?

Accepted Answer

Increases cAMP production, enhancing Ca$$^{2+}$$ influx and contractility

Question 20

Which of the following is a real-world example of multiunit smooth muscle?

Accepted Answer

Iris and ciliary body of the eye

Modulation of Contraction and Conduction in Cardiac and Smooth Muscle

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