NURS 212 Anatomy and Physiology of the Heart

-high pressure

-carry oxygenated blood away from heart

characteristics about the arterial system (arteries) (2)

-heart

-arteries

-arterioles

-metarterioles

-capillaries

what is included in the arterial system (5)

-low pressure

-adapt to pressure changes

-contains valves

characteristics of the venous system (3)

-capillaries

-venules

-veins

-heart

what is included in the venous system (4)

-oxygen and nutrients are delivered

-cellular waste is removed

what do the capillary beds do (2)

-pericardium

-myocardium

-endocardium

layers of the heart (3)

-parietal pericardium

-pericardial cavity

-visceral pericardium (epicardium)

layers of the pericardium (3)

reduce/prevent friction

what does the fluid do in the pericardial cavity (1)

-superior/inferior vena cava

-right atrium

-tricuspid valve

-right ventricle

-pulmonary valve

-pulmonary artery

-lungs

-pulmonary vein

-left atrium

-mitral valve

-left ventricle

-aortic valve

-aorta

-rest of body

Blood flow through the heart

-automaticity

-excitability

-conductivity

-contractility

parts of the cardiac conduction system (4)

automaticity

ability to spontaneously initiate an impulse

excitability

cell's response to an electrical stimulus

conductivity

ability to transmit an electrical impulse to another cardiac cell

contractility

ability to contract after receiving a stimulus

-sinoatrial (SA) node

-atrioventricular (AV) node

-ventricular cells

heart's pacemakers include (3)

depolarization

facilitates contraction

repolarization

-cell rest (to allow for the initiation of another action potential)

-rest

refractory period

protective of heart cells

absolute refractory period

occurs during/immediately after depolarization

-cell is unresponsive to any stimulus

-no stimulus will get through

what happens during the absolute refractory period (2)

relative refractory period

occurs following the absolute refractory period

-cell is responsive to "greater-than-normal" stimulus

-can sometimes take a stimulus and have a response

what happens during the relative refractory period (2)

diastole

relaxation

-volume of ventricles increase

-blood goes into the ventricles

-AV valves open

what happens to the volume of blood in the ventricles during diastole and the valves

systole

contraction

-volume in ventricles released

-blood goes to the body or lungs

-semilunar valves open

what happens to the volume of blood in the ventricles during systole and valves

accounts for the last 30% of ventricular filling (70% goes into the ventricle)

how much blood does atrial kick account for

heart rate (HR)

number of contractions per minute

stroke volume (SV)

amount of blood ejected with each ventricular contraction

50-100ml/beat

average stroke volume

cardiac output (CO)

blood ejected from the left heart each minute

4-8 L/min (does not remain constant)

average cardiac output (CO)

HR x SV = CO

equation for finding cardiac output

cardiac index

reflects CO requirement related to body size

CO / BSA = cardiac index

equation for finding cardiac index

height x weight

how to find BSA

-preload

-afterload

-contractility

factors that affect stroke volume (3)

preload

-amount of blood in the ventricles at the end of diastole

-amount of stretch of the muscle tissue at the end of filling

-increased volume = increased stretch = increased contraction

-overstretching can result in ineffective contraction

what is sterling's law and how is it related to preload (2)

afterload

resistance the ventricles must overcome to eject its blood volume

-increased afterload = increased myocardial oxygen consumption

-increased afterload = harder for blood to get out of ventricle

-increased afterload = decrease SV and CO

how does afterload affect the blood volume and the body (3)

contractility

the force of the mechanical contraction

can be increased with sympathetic stimulation or calcium release (may overstress the hearr)

why would contractility be increased

ejection fraction

proportion of the end diastolic volume that is pumped out with each beat

SV / end diastolic volume = EF

equation for finding ejection fraction

55-70% (left ventricle)

normal EF range

blood pressure

-reflection of pressures generated during the cardiac cycle

-represents force exerted against the vessel wall by blood flow

systolic BP

peak pressure generated when blood is expelled from left ventricle during contraction

diastolic BP

minimal pressure maintained on the vessel waals during relaxation

-responds to messages sent by various sensory tissues in the body

-regulates involuntary processes (HR, BP, Resp)

what does the autonomic nervous system (ANS) do (2)

-constrict vessels

-increase HR

-increase BP

what does the sympathetic nervous system do (3)

-dilate vessels

-decrease HR

-decrease BP

what does the parasympathetic nervous system do (3)