The Heart

Question 1

heart

Answer 1

four-chambered muscular organ composed of myocardium
striated muscle with high capillary density, numerous mitochondria, and a single nucleus

Question 2

right atrium and ventricle

Answer 2

receive blood returning from throughout body
pumps blood to lungs for aeration through pulmonary circulation

Question 3

left atrium and ventricle

Answer 3

receive oxygenated blood from lungs
pump blood through aorta for distribution throughout systemic circulation

Question 4

coronary circulation

Answer 4

provides oxygen and nutrient supply to the heart
myocardium extracts about 70-80% of the oxygen from the blood in coronary vessels
during exercise the only way to increase myocardial oxygen supply is to increase blood flow

Question 5

myocardial tissue

Answer 5

has a threefold higher oxidative capacity than skeletal muscle and has the greatest mitochondrial concentration of all tissues
similar patterns of myocardial metabolism exist in trained and untrained
an endurance-trained person has greater myocardial reliance on fat catabolism in submaximal exercise

Question 6

SA node

Answer 6

a 3 mm cluster of cells in the right atrium that generates electrical impulses for contraction of the heart

Question 7

gap junctions

Answer 7

electrical linkages which spread signals in a patterned way from cardiac cell to cardiac cell

Question 8

action potentials are responsible for cardiac contraction

Answer 8

caused by time-dependent changes in the permeability of the plasma membrane to K+, Na+, and Ca2+ ions

Question 9

action potential arises spontaneously at the sinoatrial node and electrical signal spreads through the right and left atrium via gap junctions

Answer 9

atrial contraction (ejection of blood) and ventricle relaxation (filling)

Question 10

the signal arises at the AV node, delays 0.1 second, and then conducts through the Bundle of His (AV bundle) and Purkinje system which spreads action potential through right and left ventricle

Answer 10

ventricle contraction (ejection of blood) and atrial relaxation (filling)

Question 11

intercalated discs

Answer 11

complex structural junctions that couple mechanically one cardiac muscle cell to another allowing for a quick continuous rhythmic contraction

Question 12

normal resting heart rate

Answer 12

would be 100 BPM if left to inherent spontaneous depolarization and repolarization of the myocardium

Question 13

autonomic nervous system

Answer 13

component of the peripheral nervous system that regulates involuntary physiologic processes

Question 14

the SNS and PNS motor pathways consist of a two-neuron series

Answer 14

a preganglionic neuron with a cell body in the CNS and a postganglionic neuron with a cell body in the periphery that innervates target tissues

Question 15

postsynaptic sympathetic neurons

Answer 15

produce norepinephrine/epinephrine as their effector transmitter

Question 16

postsynaptic parasympathetic neurons

Answer 16

use acetylcholine as their effector transmitter

Question 17

sympathetic influence

Answer 17

neurons innervate the atria and ventricles
release catecholamines epinephrine and norepinephrine
increase SA node depolarization
tachycardia
increase cardiac contractility
exercise: progressive stimulation with more intense exercise by reflex activity

Question 18

parasympathetic influence

Answer 18

neurons innervate the atria
release acetylcholine
decrease SA node depolarization
no effect on cardiac contractility
exercise: central command inhibits parasympathetic stimulation at onset and during low-to-moderate intensity exercise

Question 19

central command

Answer 19

provides the greatest control over exercise heart rate

Question 20

anticipation of exercise

Answer 20

causes a neural outflow from the central command
decreases parasympathetic inhibitory input with exercise
neural outflow is greater with anaerobic exercise than aerobic

Question 21

mechanoreceptors

Answer 21

specialized neurons that transmit mechanical information from the left ventricle, right atrium, and veins into electrical signals
input modifies parasympathetic and sympathetic outflow to initiate appropriate responses to intensity of exercise

Question 22

baroreceptors

Answer 22

pressure-sensitive neurons located in the aortic arch and carotid arteries
too great of stretch will activate baroreceptors to slow heart rate and dilate peripheral vasculature

Question 23

local factors of extrinsic regulation of the heart

Answer 23

byproducts of energy metabolism