A&P 2 Chapter 18: Heart

Flow

constant motion of a fluid

Pressure

physical force required to create flow through tube

Boyle’s Law

P1V1=P2V2

pressure and volume have an inverse relationship

Resistance

force that opposes flow

Pressure gradient

difference between area of high pressure and area of low pressure

Valves

prevent back flow

ensure one-direction flow of blood

two major divisions of circulatory system

pulmonary circulation and systemic circulation

during contraction

decrease chamber volume

increase chamber pressure

during relaxation

increase chamber volume

decrease chamber pressure

Why is the left ventricle thicker than the right ventricle?

The left must generate much higher pressure to pump oxygenated blood to systemic circuit.

How is the heart beat coordinated?

Pulmonary and systemic pumps work in parallel

contract and relax together

Where is the heart located?

thoracic cavity

The heart is protected by:

pericardium

Features of pericardium from outermost to innermost

1. fibrous pericardium

2. parietal layer of serous pericardium

3. pericardial fluid

4. visceral layer of serous pericardium

serous pericardium

double-layered, pericardial fluid filled membrane

its goes parietal, fluid, then visceral

Layers of Heart (outer to inner):

1. epicardium

2. myocardium

3. endocardium

myocardium

thickest layer, contains cardiomyocytes and cardiac skeleton

atria

upper chambers of heart

ventricles

lower chambers of heart

cardiac septum

separates left and right side

systemic pump

left atrium & left ventricle

oxygenated blood

pulmonary pump

right atrium & right ventricle

deoxygenated blood

atrioventricular (AV) valves

between atria and ventricles

tricuspid and bicuspid (mitral)

semilunar (SL) valves

between ventricles and major blood vessels

aortic & pulmonary

chordae tendinae

cords of connective tissue that connect papillary muscles to AV valves to prevent blood back flow during ventricular contraction

blood flow through the heart

1. deoxygenated blood eneters right atrium through inferior and superior vena cavas

2. pumped through tricuspid valve into right ventricle

3. blood leaves heart through pulmonary valve into pulmonary arteries into pulmonary circulation

4. oxygenated blood comes back to heart through pulmonary vein into left atrium

5. blood is pumped through bicuspid/mitral valve into left ventricle

6. oxygenated blood is pumped out of left ventricle, through aorta into systemic circulation

Fetal shunts

foramen ovale & ductus arteriosus

allows blood to skip past the non-functioning liver and lungs of the fetus and directing it to the heart and brain

foramen ovale

small hole

allows blood to bypass right ventricle and move between right and left atrium

ductus arteriosus

connect pulmonary trunk to aorta

cardiac circulation

blood supply to the heart muscle itself

where do coronary arteries originate from

aorta (oxygen rich blood)

Left coronary artery splits into:

left anterior descending artery (LAD)

circumflex artery

cardiac anastomoses

small connections between branches of the coronary arteries

features of cardiomyocytes

one central nucleus

short and wide

striations are less pronounced

intercalated discs

syncytium

intercalated disc

membranes are fused together

syncytium

entire tissue functions together "in sync”

depolarization

membrane potential become less negative and more positive

repolarization

membrane potential returns to original negativity

what is it called when membrane potential becomes more negative than rmp

hyperpolarization

action potential in contractile cardiomyocytes

0 Resting Membrane Potential

1 Depolarization

2 Transient Repolarization

3 Plateau Phase

4 Rapid Repolarization

0 back to RMP

Resting Membrane Potential

created from continuous efflux of K+ through inward rectifier potassium channels

Na/K/ATPase serves to maintain concentration gradients

Depolarization

fast sodium channels activated

influx of positively charged sodium ions

Transient Repolarization

cardiomyocytes go into a refractory period

plateau phase

Calcium is brought into the cell, while potassium is exiting the cell through delayed rectifier potassium channels

the opposites create a plateau (moment of no change)

rapid repolarization

calcium channels close

potassium ions continue to efflux to repolarize back to RMP

Cardiac Excitation Sequence

1. SA Node

2. Internodal Pathways

3. AV Node

4. Bundle of His

5. Right and Left Bundle Branches

6. Purkinje Fibers

ECG Waveforms

P Q R S T

P Wave

depolarization of atria

QRS complex

ventricular depolarization

T wave

ventricular repolarization

Cardiac Cycle

1. Atrial Systole

2. Early Ventricular Systole

3. Late Ventricular Systole

4. Early Ventricular Diastole

5. Atrial Diastole

6. Late Ventricular Diastole

Cardiac Output

amount of blood pumped by a ventricle in a period of time

CO= stroke volume * heart rate

stroke volume

amount of blood pumped out of left ventricle per systolic contraction

intrinsic regulation of cardiac output

ventricles stretch to accomodate increasing amounts of passively-entering blood (preload)

frank-starling law

extrinsic regulation of cardiac output

sympathetic: increase cAMP and speed of contraction

parasympathetic: decreases cAMP and speed of contraction