REGULATION OF THE CARDIAC CYCLE

Question 1

Sympathetic fibers

Answer 1

autonomic nervous system reach the heart and join the S-A node, A-V node and other areas of the atrial and ventricular myocardium.

secrete norepinephrine in response to nerve impulses → increases heart rate and the force of myocardial contractions.

Question 2

Parasympathetic fibers

Answer 2

the autonomic nervous system reach the S-A node and A-V node.

Fiber endings secrete acetylcholine → decreases S-A and A-V nodal activity. Results in decreased heart rate.

carry impulses continually to the S-A and A-V nodes → “braking” heart action

Increased impulses —> decreases heart rate

Decreased impulses –> releases parasympathetic “brake” and increases heart rate.

arise from neurons in the medulla oblongata.

Question 3

Cardiac center

Answer 3

maintains the balance between the inhibitory effects of the parasympathetic fibers and the excitatory effects of the sympathetic fibers

–	located in the brain stem 
–	medulla oblongate 
–	receives messages from the receptor 
–	responsible for 
o	cardioacceleration
o	cardoinhibition
o	vasomotor control

Question 4

vasomotor control

Answer 4

• vasodilation

* vasoconstriction

Question 5

vasodilation

Answer 5

smooth muscle tissue is opening up (gimme)

Question 6

vasoconstriction

Answer 6

smooth muscle tissue closes & contracts