Bio 251 Exam 3 – Questions With Solutions (Rated A+)
In smooth muscle, calcium triggers contraction by first binding to what
cytoplasmic protein?
A) troponin
B) myosin kinase
C) calmodulin
E) DHP receptors Right Ans - calmodulin
Cross bridge cycling in smooth muscle requires _____________.
A) the interaction between calcium and troponin to expose the myosin
binding site on the actin molecule
B) that the calcium-calmodulin complex activates myosin kinase, which
phosphorylates myosin thereby allowing it to bind with actin.
C) that the tropomyosin must be moved out of the way by troponin before
myosin can bind to actin
D) the activation of troponin, which stimulates myosin kinase to
phosphorylate myosin, allowing myosin Right Ans - that the calcium-
calmodulin complex activates myosin kinase, which phosphorylates myosin
thereby allowing it to bind with actin
In smooth muscle, calcium for contraction comes primarily from the___________.
A) extracellular fluid surrounding muscle cells
B) saroplasmic reticulum (SR)
C) T tubules
D) mitochondria
E) none of the above Right Ans - extracellular fluid surrounding muscle
cells
What is the function of the sodium-calcium exchanger in smooth muscle?
A) depolarize the cell
B) trigger the release of calcium from the sarcoplasmic reticulum
, C) remove calcium from the smooth muscle cells by transporting it to the
extracellular fluid thereby relaxing the muscle
D) to attach calcium to sodium inside smooth musele cells to initiate
contraction of the cells
E) interact with troponin to initiate cross-bridge cycling Right Ans -
remove calcium from the smooth muscle cells by transporting it to the
extracellular fluid thereby relaxing the muscle
Which of the following is NOT a part of the excitation-contraction coupling in
cardiac muscle?
A) An action potential travels along the plasma membrane of the cardiac
muscle cells
B) Calcium channels in the plasma membrane open, allowing calcium ions to
enter the cell
C) Calcium opens calcium channels in the sercoplasmic reticulum (SR) via a
calcium induced calcium release mechanism
D) Calcium channels in the sarcoplasmic reticulum upen, allowing calcium
ions to enter the cytuplasm
E) Calcium Right Ans - Calcium binds to calmodulin in the cytoplasm of
cardiac muscle cells to initiate contraction
What two major regions of the heart contain large numbers of pacemaker
cells?
A) sinoutrial node (SA) and atrioventricular (AV) node
B) sinoatrial node and Purkinje fibers
C) sinoatrial node and hundle of His
D) bundle of His and atrioventricular node
E) bundle of His and Purkinie fibers Right Ans - sinoutrial node (SA) and
atrioventricular (AV) node
What is the primary pacemaker of the heart?
A) bundle of His
B) Purkinje fibers
C) SA node
In smooth muscle, calcium triggers contraction by first binding to what
cytoplasmic protein?
A) troponin
B) myosin kinase
C) calmodulin
E) DHP receptors Right Ans - calmodulin
Cross bridge cycling in smooth muscle requires _____________.
A) the interaction between calcium and troponin to expose the myosin
binding site on the actin molecule
B) that the calcium-calmodulin complex activates myosin kinase, which
phosphorylates myosin thereby allowing it to bind with actin.
C) that the tropomyosin must be moved out of the way by troponin before
myosin can bind to actin
D) the activation of troponin, which stimulates myosin kinase to
phosphorylate myosin, allowing myosin Right Ans - that the calcium-
calmodulin complex activates myosin kinase, which phosphorylates myosin
thereby allowing it to bind with actin
In smooth muscle, calcium for contraction comes primarily from the___________.
A) extracellular fluid surrounding muscle cells
B) saroplasmic reticulum (SR)
C) T tubules
D) mitochondria
E) none of the above Right Ans - extracellular fluid surrounding muscle
cells
What is the function of the sodium-calcium exchanger in smooth muscle?
A) depolarize the cell
B) trigger the release of calcium from the sarcoplasmic reticulum
, C) remove calcium from the smooth muscle cells by transporting it to the
extracellular fluid thereby relaxing the muscle
D) to attach calcium to sodium inside smooth musele cells to initiate
contraction of the cells
E) interact with troponin to initiate cross-bridge cycling Right Ans -
remove calcium from the smooth muscle cells by transporting it to the
extracellular fluid thereby relaxing the muscle
Which of the following is NOT a part of the excitation-contraction coupling in
cardiac muscle?
A) An action potential travels along the plasma membrane of the cardiac
muscle cells
B) Calcium channels in the plasma membrane open, allowing calcium ions to
enter the cell
C) Calcium opens calcium channels in the sercoplasmic reticulum (SR) via a
calcium induced calcium release mechanism
D) Calcium channels in the sarcoplasmic reticulum upen, allowing calcium
ions to enter the cytuplasm
E) Calcium Right Ans - Calcium binds to calmodulin in the cytoplasm of
cardiac muscle cells to initiate contraction
What two major regions of the heart contain large numbers of pacemaker
cells?
A) sinoutrial node (SA) and atrioventricular (AV) node
B) sinoatrial node and Purkinje fibers
C) sinoatrial node and hundle of His
D) bundle of His and atrioventricular node
E) bundle of His and Purkinie fibers Right Ans - sinoutrial node (SA) and
atrioventricular (AV) node
What is the primary pacemaker of the heart?
A) bundle of His
B) Purkinje fibers
C) SA node
