Exam 1 - The Heart

blood vessels

arteries

vein

capillaries

arteries

carry blood away from the heart

veins

carry blood toward the heart

capillaries

exchange site between blood and the body/cells

pulmonary circulation

moves deoxygenated blood from the right side of heart to the lungs to pickup oxygen and then back to the left side of the heart

systemic circulation

moves oxygenated blood from the left side of the heart to the body cells for exchange of gases/nutrients and then back to the right side of the heart

pericardium

a double-layered sac that surrounds and protects the heart

2 outer coverings

• pericardial sac

• inner visceral layer

pericardial sac

double-layered fibroserous sac

consists of:

• fibrous pericardium

• parietal layer of serous pericardium

fibrous pericardium

outer portion of sac made up of dense irregular CT

in the pericardial sac

pericardial cavity

space between the parietal and visceral layers where serous fluid resides

contains serous fluid

serous fluid

lubricates membranes and allows frictionless movement of the heart

secreted by both parietal and visceral layers

epicardium

myocardium

endocardium

layers of heart wall

epicardium

outermost layer of the heart

composed of simple squamous epithelium

myocardium

middle layer of the heart wall

composed of cardiac muscle tissue

generates the force to pump blood

thickest of the 3 layers

endocardium

internal surface of the heart chambers

composed of simple squamous epithelium with areolar tissue

continuous with inner lining of blood vessels

deoxygenated blood

type of blood the right side of the heart contains

oxygenated blood

type of blood the left side of the heart contains

arteries

attach to the ventricles and transport blood away from the heart

veins

deliver blood to the atria

pulmonary trunk

transports deoxygenated blood from the right ventricle to the lungs

aorta

transports oxygenated blood from the left ventricle to the body

arteries

pulmonary trunk

aorta

veins

superior and inferior vena cava

pulmonary veins

superior and inferior vena cava

bring deoxygenated blood from the body into the right atria

pulmonary veins

bring oxygenated blood from the lungs to the left atria

interventricular septum

thick wall that separates the right and the left ventricles

left, right

walls of the ____ ventricle are 3 times thicker than the _____ ventricle

left

____ ventricle must generate enough pressure ot force the blood through the entire systemic circulation

right atrium components

fossa ovalis

foramen ovale

coronary sinus

fossa ovalis

oval depression where the fetal foramen ovale was located

foramen ovale

shunted blood from the right atrium to the left, passing the nonfunctional fetal lungs

coronary sinus

opening inferior to the fossa ovalis

drains blood from the heart wall

ventricle components

papillary muscles

chordae tendineae

papillary muscles

3 cone-shaped muscular projections that anchor chordae tendineae

chordae tendineae

attached to the right AV (tricuspid) valve

when the papillary muscles contract, they pull on these and prevent prolapse of the valve (prevent inversion of valve)

left atrium

contains the 4 openings for the pulmonary veins

left ventricle

contains 2 papillary muscles anchored to chrodae tendineae

foramen ovale, fossa ovalis, and ductus arteriosus

fetal structures within the heart

foramen ovale

blood entering the right atria is shunted directly into the left atria to bypass the non-functioning fetal lungs

closes after birth (when blood pressure rises in left side of heart) and becomes the fossa ovalis

fossa ovalis

when the foramen ovale closes after birth and becomes this structure

ductus arteriosus

a vessel that connects the pulmonary trunk to the aorta

it shunts blood that has entered the right ventricle directly into the aorta (bypassing the nonfunctional fetal lungs)

it is replaced by the ligamentum arteriosum after birth

ligamentum arteriosum

replaces the ductus arteriosus after birth

heart valves

open to allow blood to flow through and close to prevent backflow

ensures unidirectional flow of blood

atrioventricular (AV) valves

when ventricles are relaxed, these are open and the cusps extend into the the ventricles allowing blood to move from the atrium into the ventricle

when ventricles contract, ventricular pressure rises as blood flows superiorly, this causes these to close

semilunar valves

open when ventricles contract and force of blood pushes them open

close when ventricles relax; pressure in ventricles becomes less then the pressure in the arterial trunk

• close when blood begins to move back toward the ventricles

heart murmur

insufficient functioning of valves

causes swooshing sound

the valves closing

what creates the “lubb-dubb” sounds associated with heartbeat

“lubb”

sound when AV valves close

“dubb”

sound when SL valves close

coronary arteries

supply oxygenated blood to the wall of the heart

coronary veins

transport deoxygenated blood away from the heart wall

right coronary artery

branches into right marginal artery and posterior interventricular artery

right marginal artery

supplies right border of heart

posterior interventricular artery

supplies posterior surface of right and left ventricles

left coronary artery

branches into circumflex artery and anterior interventricular artery

circumflex artery

supplies left atria and ventricle

anterior interventricular artery

supplies anterior surface of both ventricles

coronary sinus

a large vein that lies within the posterior coronary sulcus

all coronary veins drain into this structure

drains deoxygenated blood from the heart wall into the right atrium

myocardial infarction (heart attack)

results from sudden and complete occlusion (blockage) of a coronary artery

the region of the myocardium that is deprived of oxygen may die (necrosis)

intercalated discs

structures on the sarcolemma that link the cells together mechanically and electrically

metabolism of cardiac muscle

has great demand for energy

• extensive blood supply

• numerous mitochondria (25% of cell)

relies almost exclusively on aerobic respiration —> requires constant oxygen supply (blood supply)

• susceptible to failure

autonomic nervous system

heart rate and strength of the contraction are controlled by the ____________________

sinoatrial (SA) node

where the heartbeat is initiated

found in the posterior/superior wall of the right atrium

known as “pacemaker”

atrioventricular (AV) node

found in the floor of the right atrium

atrioventricular bundle (bundle of His)

extends from the AV node through the interventricular septum

divides into left and right bundles

purkinje fibers

extend from left and right bundles (at the apex) through the ventricles

conduction system components

SA node

AV node

Atrioventricular bundle (bundle of His)

purkinje fibers

nodal cells

specialized pacemaker cells in the SA node that initiate a heartbeat

RMP is -60 mV however, it is not stable (neuron’s RMP is -70)

RMP increases to threshold without stimulation —> pacemaker potential (autorhythmicity)

autorhymicity

when the RMP increases within nodal cells to threshold without stimulation —> pacemaker potential

SA nodal cell events

1. reaching threshold

2. depolarization

3. repolarization

reaching threshold in SA nodal cells

Na+ flows into the nodal cells, changing RMP from -60 mV to the threshold value of -40 mV

depolarization of SA nodal cells

upon reaching threshold, Ca2+ flows into cell giving it a near positive RMP (0)

repolarization in SA nodal cells

Ca2+ channels close, K+ channels open allowing K+ out of cell —> returns cell to RMP -60 mV

this triggers the reopening of Na+ channels and process begins again (no outside activation needed)

spread of action potential

1. distributed throughout atria and is relayed to the AV node

2. is delayed at the AV node

3. travels from the AV node through the AV bundle to the purkinje fibers

4. spreads throughout both ventricles

depolarization

as the action potential travels through the conduction system, it triggers Na+ channels in the sarcolemma to open

RMP becomes more positive

plateau

depolarizartion triggers K+ to leave the cell and Ca2+ to enter the cell (from outside cell and from sarcoplasmic reticulum)

no change in electrical charge, so the sarcolemma remains in this depolarized state

includes the cross bridge cycling

cross bridge cycling

1. as Ca2+ enters the sarcoplasm, it binds to troponin

2. tropomyosin is pulled off the myosin binding sites

3. myosin and actin bind together —> slide past one another, shortening the sarcomere

repolarization

Ca2+ channels close, K+ continues to leave the cell

RMP of -90 mV is reestablished

refractory period

when a muscle cell cannot be re-stimulated to contract

the time between depolarization and repolarization

the longer plateau phase of cardiac muscle cells, delays repolarization, so RMP is reestablished more slowly

• sarcomeres can fully relax prior to contracting again —> prevents sustained contraction

ECG waves

1. P wave

2. QRS complex

3. T wave

P wave

reflects the electrical changes of atrial depolarization; starts in SA node

QRS complex

electrical changes with ventricular depolarization (atria are also repolarizing)

T wave

electrical changes with ventricular repolarization

ECG segments

1. PQ/PR segment

2. ST segment

PQ/PR segment

atrial plateau when cardiac muscle cells of the atria are contracting

ST segment

ventricular plateau when cells of the ventricles are contracting

ECG waves

_____ are associated with electrical events (action potential)

ECG flat lines/segments

______ correspond to mechanical events (contraction/relaxation)

heart resting between beats

flat line between cycle corresponds to ___________

cardiac cycle

the changes that occur in the heart from the initiation of one heartbeat to the start of the next

includes systole and diastole

systole

contraction of a heart chamber

diastole

relaxation of a heart chamber

pressure changes within the heart

caused by alternating contracting/relaxing of the atria and ventricles

increases

atrial/ventricular contraction ______ pressure

decreases

atrial/ventricular relaxation ______ pressure

high, low

blood always flows from a region of _____ pressure to ____ pressure

cardiac cycle phases

1. atrial systole (and ventricular filling)

2. early ventricular systole

   • isovolumetric contraction

3. late ventricular systole

   • ventricular ejection

4. early ventricular diastole

   • isovolumetric relaxation

5. late ventricular diastole

   • atrial relaxation and ventricular filling

atrial systole and ventricular filling

atria contract, ventricles relax

ventricular pressure < atrial pressure

ventricular pressure < arterial trunk pressure

AV valves are open, SL valves are closed

early ventricular systole (isovolumetric contraction)

atria relax, ventricles contract

ventricular pressure > atrial pressure

ventricular pressure < arterial trunk pressure

AV valves are closed, SL valves are closed

late ventricular systole (ventricular ejection)

atria relax, ventricles contract

ventricular pressure > atrial pressure

ventricular pressure > arterial trunk pressure

AV valves are closed, SL valves are open