two systems that regulate heart activity:
autonomic nervous system and intrinsic conduction system/nodal system
intrinsic conduction/nodal system
sets heart rhythm
composed of special nervous tissue
ensures heart muscle depolarization in one direction only (atria to ventricles)
enforces a heart rate of 75 beats per inute
autonomic nervous system
controls voluntary movement
Sinoatrial node
located in the right atrium
serves as the heart’s pacemaker
Atrioventricular node
at the junction of the aria and ventricles
atrioventricular bundle/bundle of his
in the interventricular septum with bundle branches
Purkinje fibers spread within the ventricle wall muscles
Sinoatrial node
starts each heartbeat
impulse spreads through the atria to the AV bundle, bundle branches, and Purkinje fibers
ventricles contract; blood ejected from heart
techycardia
rapid heart rate, over 100 beats per minute
Bradycardia
slow heart rate, less than 60 beats per minutes
Cardiac cycle
refers to one complete heartbeat, when both atria and ventricles contract and relax
Systole
contraction
Diastole
relaxation
average heart rate
75 beats per minute
Length of cardiac cycle
0.8 seconds
____ transfers blood to tissues and back from the heart
blood vessels in the closed vascular system
arteries and arterioles
vessels that carry blood away from the heart
capillary beds
vessels that are involved in exchanges between blood and tissue
venules and veins
vessels that return blood toward the heart
tunica intima
layer of the blood vessels that is friction reducing
endothelium
tunica media
smooth muscle and elastic tissue
controlled by the sympathetic nervous system
tunica externa
forms protective outermost covering
mostly fibrous connective tissue
supports and protects the vessel
arteries
heavier, stronger, and stretching tunica media than veins to withstand pressure changes
smaller lumen
veins
thinner tunica media because they operate under low pressure
have valves to prevent backflow
larger lumen
skeletal muscle contracts and pushes blood in veins toward heart
capillaries
one layer thick, tunica intima
exchanges between blood and tissue
form capillary beds, networks that consist of:
vascular shunt and true capillaries
microcirculation
blood flow through a capillary bed