Physiology; Cardiac System

when does the heart of the developing embryo start to function

3 weeks after conception

what is the first organ to develop

the heart

on average, how often does the heart contract

3 billion times

what are the three components of the circulatory system

• heart

• blood vessels

• blood

what are the two branches of the circulatory system

pulmonary and systemic

what is apart of the pulmonary circulation

between the heart and lungs

what is apart of the systemic circulation

between the heart and all body systems

what is the base of the heart

the top of the heart

what is the apex of the heart

the bottom of the heart

what does cardiac pulmonary resuscitation allow

allows blood flow to the tissues by compressing heart

what does atria do

receives blood returning to the heart and transfers it to the lower chamber of the heart

what does the ventricles do

pump blood away from the heart

what do the veins do

bring blood from tissues to atria

what do the arteries do

carry blood away from ventricles to tissues

what is the septum

the muscular partition that separates left to right and prevents blood mixing

what does the venae cava do

return blood to the right atrium

what does the pulmonary artery do

takes de-oxygenated blood from right ventricle to the lung

what does the pulmonary veins do

brings oxygenated blood from lung to the left atrium

what does the aorta do

carriers oxygenated blood from left ventricle to the body

what is apart of the pulmonary pump

is apart of the right ventricle that pumps blood to lungs for oxygenation

what does the pulmonary artery do

de-oxygenated blood to lungs

what does the systemic pump do

left ventricle pumps blood to the body

what does the aorta do

oxygenated blood to systemic tissues

what does the superior/inferior vena cava do

returns de-oxygenated blood back to right atrium

what do pressure operated heart valves ensure

that blood flows in the right direction through the heart

what does the atrioventricular valves do

prevent backflow of blood from the ventricles into the atria during ventricular emptying

what is the name of the right AV valve

tricuspid valve

what is the name of the left AV valve

bicuspid valve

what is the name of the semilunar valves

aortic and pulmonary valves

when atrial pressure is not higher than venous pressure then…

no back flow occurs

what are the three layers of the heart wall

endocardium, myocardium, and epicardium

endocardium layer

inner layer, endothelium tissue that lines the inside of the heart wall

myocardium layer

middle layer, intercalating bundles of cardiac muscle fibers arranged spirally around the circumference of the heart

epicardium layer

external layer of the heart

what is the pericardium

membranous sac that encloses the heart

what is the outer layer of the pericardium

parietal pericardium

what is the inner layer of the pericardium

visceral pericardium which secretes pericardial fluid

what are cardiac muscle fibers connected by

intercalated disc

what junctions does the intercalated discs contain

desmosomes and gap junctions

what does gap junction allow

the spread of action potential from one cardiac cell to another

what does functional syncytium allow

muscle mass to undergo synchronous contraction as a single unit

atria and ventricles form what syncytium

separate

the atria and ventricles contract

separately

what are the two type of cells in the heart

autorhythmic and contractile cells

what do autorhythmic cells doe

initiate and conduct the action potentials responsible for contraction of contractile cells

what can autorhythmic cells generate

AP rhythmically becuase it does not have a resting membrane potential

what does the contractile cells do

99% of the mechanical work of pumping

what two potential happen in the autorhythmic cell

pacemaker potential and action potential

What happens to the Na+ current in the pacemaker potential

it increases

what are funny sodium channels

special channels that allow sodium to enter the cell during the pacemaker potential.

what happens to K+ current in the pacemaker potential

it decreases

what is the normal pacemaker of the heart

sino atrial node= 70-80 bpm

what bpm is atrioventricular node

40-60 bpm

atrial excitation and contraction should be complete before what

before ventricular contraction onset

what is uncoordinated excitation and contraction of cardiac cells called

fibrillation

why should the pair of atria and pair of ventricles be functionally coordinated

so that both members of the pair contract simultaneously

what two pathways is atrial excitation apart of

interatrial and internodal pathway

what does the interatrial pathway do

carries the electrical signal from the right atrium to the left atrium

what does the internodal pathway do

carry the electrical signal from the SA node toward the AV node

what is invovled in the atrio ventricular conduction

the atria contracts, the AV node delays the signal, the ventricles contract

what does the AV nodal delay allow

allows ventricular filling, delay is about 100 msec

what does the bundle of His and Purkenji fibers do during ventricular excitation

rapidly conduct impulse throughout the septum and ventricular myocardium

how much faster does the Pukenji fibers transmit an action potential then the ventricular syncytium of contractile cells

six times faster

what does transmission through Purkenji fibers allow

simultaneous activation of entire ventricular muscle cells

what happens when the SA node is damaged

AV node assumes the pacemaker activity

what happens when complete heart block occurs

Purkenji fibers drive ventricular pacemaker activity at 30 beats per minute, patients goes into coma, and a artificial pacemaker is used

what happens when an area of the heart becomes overly excited and surpass the normal pacemaker activity

initiates premature action potential and result in premature ventricular contraction

during cardiac action potential, how is CA2+ from ECM diffussed

diffussed to cytosol across T Tubule membrane

what are CA2+ sparks

local burst of Ca2+ release from SR, which increases the pool of CA2+ in the cytosol

what does this extra supply of Ca2+ allow

long periods of cardiac contraction

how is Ca2+ removed from the cytosol

by energy dependent mechanisms (Na+, Ca2+) exchanger so that contraction ceases and the heart muscle relaxes

what does the long refractory period prevent in the cardiac muscle

summation of contraction( when a muscle receives another signal before it has fully relaxed) and tetanus (continuous contraction)

why is a long refactory period a valuable protective mechanism

pumping blood requires alternate contraction(emptying) and relaxation(filling)

what is the cardiac cycle diastole

relaxation and filling

what is the cardiac cycle systole

contraction and emptying

what is the first heart sound (lub)

the AV valve closed

what is the second heart sound (dup)

the semilunar valve closing

what produces heart murmurs

turbulent blood flow

what are stenotic valves

stiff valve does not open completely

what are insufficient or incompetent valve

cannot close completely because valve edge do not fit together

what does cardiac output depend on

heart rate and stroke volume

what is the cardiac output equation

CO= HR(beats per minute) times SV

What is heart rate influenced by

autonomic nervous system

how does the parasympathetic effect heart rate

slows the heart down

how does the sympathetic effect heart rate

speeds the heart up

what is the SV influenced by

intrinsic and extrinsic stimulations

what is stroke volume

the amount of blood pumped by the heart in each beat