5 6
CARDIOVASCULAR PHYSIOLOGY CONCEPTS
contraction, vascular smooth muscle
contraction is slow and sustained.
*
Cardiac muscle contraction is regulated
by various substances that bind to
receptors coupled to G-proteins.
Vascular smooth muscle contraction/
relaxation is additionally regulated
by NO/cGMP-dependent pathways.
All these pathways largely affect
contraction/relaxation primarily by
regulating intracellular calcium.
The vascular endothelium synthesizes
nitric oxide and prostacyclin, both of
which relax vascular smooth muscle.
Endothelin-1, which is also synthesized
by the endothelium, contracts vascular
smooth muscle.
REVIEW QUESTIONS
For each question, choose the one best answer:
1.
Which of the following is common to
both cardiac myocytes and vascular
smooth muscle cells?
a. Dense bodies
b. Myosin light chain kinase
c. Terminal cistemae
d. T tubules
2.
Thick filaments within cardiac myocytes
contain
a. Actin.
b. Myosin.
c. Tropomyosin.
d. Troponin.
3.
During excitation-contraction coupling
in cardiac myocytes,
a. Calcium binds to myosin causing ATP
hydrolysis.
b. Calcium binds to troponin-I.
c. Myosin heads hind to actin.
d. SERCA pumps calcium out of the
sarcoplasmic reticulum.
4.
Cardiac inotropy is enhanced by
a. Agonists coupled to Gi-protein.
b. Decreased calcium binding to
troponin-C.
c. Decreased release of calcium by
terminal cisternae.
d. Protein kinase A phosphorylation of
L-type calcium channels.
5.
Vascular smooth muscle contraction is
enhanced by
a. Activation of myosin light chain
kinase.
h. Activation of myosin light chain
phosphatase.
c. Calcium binding to troponin-C.
d. Dephosphorylation of myosin light
chains.
6.
Angiotensin II causes contraction of
vascular smooth muscle by
a. Activating Gs-protein.
b. Increasing cAMP
c. Increasing IP3.
d. Inhibiting release of calcium by
sarcoplasmic reticulum.
7.
A patient in circulatory shock is
treated with norepinephrine to raise
arterial pressure by stimulating the
heart through ß-adrenoceptor activa-
tion and constricting blood vessels
through oq-adrenoceptor activation.
The cardiac and vascular effects can be
explained by
a. Increased cardiac cAMP and increased
vascular cGMP.
h. Increased cardiac cAMP and increased
vascular IP3.
c. Increased cardiac and vascular cAMP
d. Increased cardiac IP3 and increased
vascular cAMP.
previous page 69 Cardiovascular Physiology Concepts  2nd Edition read online next page 71 Cardiovascular Physiology Concepts  2nd Edition read online Home Toggle text on/off