Cardiovascular( Structure and Function)

what is the hearts conduction system dependent upon?

rhythmic stimulation of cardiac muscle cells

automaticity of the heart

pumping blood continuously, precise electrical events initiated by conduction system, transmission of action potential by conduction fibers, ensures atria contracts prior to ventricles, precise electrical events initiated y conduction system

conduction system

specialized cardiac muscle cells, initiate and conduct electrical signals

Sinoatrial node(SA) location

in posterior wall of right atrium and adjacent to superior vena cava

SA role

depolarizes and fires action potential simultaneously initiating heartbeat

P Wave

result of depolarization wave from SA node to the AV node

QRS complex

result of ventricular depolarization and precedes ventricular contraction, obscures atrial repolarization

T wave

caused by ventricular repolarization

electrocardiogram

a non-invasive diagnostic test that records the electrical activity of the heart over time using electrodes placed on the skin

sequence of excitation

atrial excitation, ventricular excitation, ventricular relaxation

P-R interval

atrial depolarization to beginning of ventricular depolarization, time to transmit action potential through entire conduction system

P-Q segment

associated with atrial plateau at sarcolemma, cardiac muscle cells within atra contracting

S-T segment

ventricular plateau, cardiac muscle cells in ventricle contracting

Q-T

ventricular depolarization to repolarization, interval depends upon heart rate

QRS complex

ventricular depolarization, atrial repolarization (masked)

excitation-contraction coupling

the physiological process converting an electrical stimulus (action potential) into a mechanical response (muscle contraction)

skeletal and cardiac excitation similarities

have a refractory period, depolarize, repolarize, muscle contraction and relaxation, lag time between action potential and contraction

skeletal and cardiac excitation differences

refractory period longer in cardiac cells

cardiac cycle components

systole and diastole

systole

contraction of a heart chamber

diastole

relaxation of the heart chamber

pressure changes in cardiac cycle is responsible for?

unidirectional movement of blood through chambers and opening/closing of heart valves

pressure changes in cardiac cycle

alternating contraction and relaxation of atria and ventricles, pressure increases during contraction, pressure decreases during relaxation

ventricular contraction

causes ventricular pressure to rise, AV valves pushed and kept closed, prevent backflow, semilunar valves pushed open, force blood from ventricle into arterial trunk

ventricular relaxation

causes ventricular pressure to decreases, closure of semilunar valves, AV valves open

cardiac output(CO)

amount of blood pumped by a single ventricle in one minute, measure of effectiveness fo cardiovascular system

equation to calculate CO

CO=heart rate(HR) * stroke volume (SV)

variables that influence cardiac output

heart rate and stroke volume

heart rate volume influence on cardiac output

stimulate SA node to change its firing rate, stimulate AV node to alter amount to delay

stroke volume influence on cardiac output

venous return altering stretch of heart, inotropic agents influencing number of crossbridges, afterload decreasing stroke volume

stroke volume

the difference between the end diastolic volume and end sisytolyc volume

how to calculate stroke volume

SV=EDV-ESV

ejection fraction(EF)

the ratio of SV to EDV, a way to quantify contractility

afterload

the pressure that the ventricles must overcome to force open the aortic and pulmonary valves

what can affect arterial pressure?

anything that increases systemic or pulmonary arterial pressure

how to calculate arterial stretch(compliance)?

compliance= ∆volume/∆pressure

relationship between compliance and stretchiness

positive

why are arteries known as pressure reservoirs?

the elastic recoil, are not as compliant as veins

blood pressure

force per unit area of blood agains vessel wall, driving force that propels blood, change in pressure throughout

blood pressure gradient

pressure highest in arteries and lowest in veins

arterial blood pressure

blood flow pulsatile, systolic pressure, diastolic pressure

blood flow pulsatile

due to ventricles contracting and relaxing

systolic pressure

pressure in arteries during ventricular systole, highest pressure generated in arteries, artery maximally stretched

diastolic pressure

pressure in arteries during ventricular diastole, lowest pressure generated in arteries, artery meximally recoiled

blood pressure readings

given as a ratio of systolic to diastolic, 120/80 mm Hg

pulse pressure

difference between systolic pressure and diastolic pressure

important factors in determining the magnitude of pulse pressure

stroke volume,speed ejection of the stroke volume, arterial compliance

arteriosclerosis

stiffening of arteries

flow and pressure relationship

F=∆P/R

3 things that contribute to resistance

blood viscosity, total blood vessel length, blood vessel diameter

factors that increase blood flow

cardiac output and vasodilation

factors that decrease blood flow

cardiac output and vasoconstriction

why is velocity the slowest in capillaries

due to them having the greater cross-sectional area

the direction of fluid movement in capillaries is dependent on?

difference between the net hydrostatic pressure and the net colloid osmotic pressure

hydrostatic pressure

force exerted by the fluid pressing against a wall, in capillaries its the same as capillary blood pressure

lymphatic system

picks up excess fluid not reabsorbed at venous capillary end, filters fluid and returns it to venous circulation

diffusion of oxygen, hormones, and nutrients

move from higher concentration in blood, move into interstitial fluid and tissue cells

diffusion of CO2 and waste products

diffuse from higher concentration in tissue to blood

diffusion of small solutes

diffuse via endothelial cells or intercellular clefts

diffusion of larger solutes

pass through fenestrations or gaps in sinusoids

respiratory pump

pressure changes in the central cavity due to the pressure changes due to breathing, helps propel blood back to the heart

muscular pump

when muscles contract they squeeze the veins, moves blood towards the heart

what does the muscular pump result in?

blood moving forward and being prevented from backflow by the veins

what system is smooth and arterial smooth muscle under?

sympathetic nervous system