Patho 3.1 Cardiac Physiology

what comprises the cardiovascular system?

the heart and blood vessels

what is the difference between systemic and pulmonary circulation?

• systemic pumps oxygenated blood out of the left ventricle, carrying waste to kidneys, liver, and skin

• pulmonary pumps deoxygenated blood out of the heart to lungs

arteries do what?

high pressure with thick walls for oxygenated blood to be carried away

veins do what?

lower pressure with thinner walls for deoxygenated blood from blood to heart

capillaries do what?

they are tiny vessels connecting arteries to veins for gas exchange, only one cell thick

pathway of blood through the heart

sup. inf. vena cava —> right atrium —> tricuspid valve —> right ventricle —> pulmonary valve and artery —> lungs for O2 —> pulmonary vein —> left atria —> mitral valve —> left ventricle —> aorta —> arteries —> capillaries —> veins —> sup. inf. vena cava

layers of the heart

pericardium, myocardium, endocardium

what is the pericardium of the heart?

the outer wall, providing protection and support, 50 ml of fluid between parietal and visceral layers

what is the myocardium of the heart?

the middle layer, muscular and thick in ventricles

what is the endocardium of the heart?

lines the inner epithelial layer, including cardiac valves

T/F the cardiovascular system is an open circuit

F, the cardiac flow is a closed circuit to always move bloodd forward

systole in the cardiac cycle

the heart contraction: ventricles push blood out of the heart, so the aortic valve and pulmonic valve are open, BUT the mitral and tricuspid valve are closed

diastole part of the cardiac cycle

when the heart relaxes: ventricles fill, aortic and pulmonic valve are closed, BUT the mitral and tricuspid valve are closed

Cardiac conduction, 3 components

conductivity - can conduct impulses

excitability - respond to impulses

automaticity - generate impulses

what happens in the heart at 90 milivolts?

nothing, the heart is at rest: K+ is leaking, Na+ and Ca+ channels are closed

what happens in the heart at 40 miliviolts?

the heart is repolarizing, so K+ is moving out of the cell

what happens in the heart when the impulse causes depolarization?

a contraction/systole

T/F all healthy heart cardiac cells should generate an impulse

F, healthy heart cardiac cells should not generate an impulse, the Sinoatrial Node (SA) should generate the impulse

Path of impulses in the heart

SA node (right atrium)—> AV node (right atrium)—> bundle of HIS (interventriclar septum) —> purkinje fibers (inside ventricles)

what is another name for the Sinoatrial Node?

pacemaker

what is the normal BPM range for the SA node in the right atrium of the heart?

60-100 BPM, spreads impulse to cardiac cells around it/ excitable

where does the impulse travel to from the SA node?

the Atrioventricular Node, which generates impulse of 40-60 BPM

why does the AV node generate a lower BPM than the SA node?

it is delayed so ventricle can fill up, moves through the atria of the heart to cause a contraction

what is the bundle of HIS?

branch of nerve cells extending from the AV node that stretches into the right and left septum of the heart

where do the bundle of HIS travel to?

the Purkinje fibers/ network of fibers that spread the impulse quickly to cause ventricle contraction

what machine reads the electrical conduction of the heart over a period of time?

Cardiac Telemetry Monitoring

• electrical impulse moves to skin and electrodes can sense them

what does the electrocardiodiagram/EKG do?

it is a snapshot of the heart rhythm

• 6 lead is most common

• 12 lead is a snapshot

what is the P-wave?

orange: contraction of the R and L atria

what is the PR segment?

green: pause at the AV node so ventricles can fill up/ isoelectric

what is the QRS segment?

pink: largest wave, ventricles contract

what is the ST segment?

purple: when the ventricles repolarize and depolarize

what is the T-wave?

blue: ventricles go back to resting/repolarization

what nervous system largely controls the heart rate?

ANS: sympathetic and parasympathetic

what are chemoreceptors?

detect chemical changes in the blood

what are baroreceptors and where are they found?

found in carotid arteries, detecting pressure changes in heart and arteries

what are adrenocgenic receptors and where are they found?

structures on effector cells that respond to catecholamines, essentially let sympathetic and parasympathetic act on heart and vessels

what are the types of adrenogenic receptors

vascular smooth muscle (A1) | vasculature smooth muscle, vasoconstriction

central nervous system (A2), decrease smooth muscle of GI tract with SNS

(B1), increased Heart, contractility

(B2), contractility in lungs, increased HR

blood pressure def

force of blood on walls of blood vessels haw

what are the two numbers for blood pressure?e

systolic pressure is the larger number / 90-100mmHg

diastolic pressure is smaller / 60-80 mmHg

how do you find the pulse pressure?

Systolic - diastolic = difference

how do you find the mean arterial pressure (MAP)

systolic + diastolic + diastolic / 3 = 70-100 mmHg

what does it mean when the minimum MAP is below 65?

you have poor perfusion

cardiac output def

blood from heart in 1 minute | stroke volume x HR

what is stroke volume (SV)?

how much blood is ejected from the heart with each beat

what is the heart rate?

number of times a heart beats per minute

what is ejection fraction/EF

the percent of blood ejected from the left ventricle

• blood ejected/total amount of blood in L.V.

• usually 50-70% of blood is still in there

what is peripheral vascular resistance?

the force opposing blood in peripheral circulation

• constriction, increased

• dilation, decreased = maybe sepsis because not enough blood flow to cells

factors influencing BP

hormones

renin-angiotensin-aldosterone system

viscosity of blood

blood volume

cardiac contractility