BIOL2150 Exam 2 Study Guide

a fist

the heart is the size of

point of maximal intensity

where the apex of the heart contacts the chest wall is called the

pericardium

the heart is enclosed in a covering called the

outer fibrous pericardium

layer of the pericardium made of dense connective tissue for protection from high blood pressure, anchoring, and prevention of overfilling

parietal layer

layer of the middle serous pericardium that lines the inner layer of the fibrous pericardium

visceral layer

layer of the middle serous pericardium, also referred to as the epicardium, which is a continuum of the parietal layer and covers the internal surface of the heart

pericardial cavity

space between the visceral and parietal layers of the pericardium that contains serous fluid

pericarditis

inflammation of the pericardium, usually caused by a bacterial infection; impedes fluid production and causes friction between membranes which impedes heart activity

epicardium, myocardium, endocardium

three layers of the heart wall:

myocardium

bulk of the heart wall made of contracting cardiac muscle

endocardium

shiny white sheet of endothelial cells that lines heart chambers and covers valves; continuous with endothelial lining of blood vessels

left and right atria

two superior chambers of the heart

left and right ventricles

inferior chambers of the heart

atria

receiving chambers of the heart for blood returning to the heart from the body (via systemic circulation) and the lungs (via pulmonary circulation)

superior and inferior vena cavae and coronary sinus

blood enters the right atrium via the

pulmonary veins

blood enters the left atrium via the

ventricles

discharging chambers of the heart that contain irregular muscular ridges called trabeculae carneae and papillary muscles

pulmonary circulation

the right ventricle pumps blood into:

systemic circulation

the left ventricle pumps blood into:

away from

arteries carry blood ______________ the heart

to

veins carry blood __________ the heart

oxygen, carbon dioxide

in body tissue, ___________ diffuses into the tissues and _________ diffuses from the tissues

left ventricle

most powerful pump in the heart, with thick myocardium and a circular cavity that allows it to generate more pressure

tricuspid, bicuspid, aortic, pulmonary

name the four valves of the heart

atrioventricular valves

two heart valves located between the atria and ventricles that prevent backflow into the atria when ventricles contract

open

when the atria contract, the atrioventricular valves ___________ as pressure in the atria exceeds pressure in the ventricles

close

when ventricular pressure is greater than atrial pressure, atrioventricular valves__________

semilunar valves

two heart valves that guard the exit points of each ventricle and prevent backflow of blood leaving the ventricles

aortic valves

semilunar valves that prevent backflow of blood into the left ventricles

pulmonary valves

these semilunar valves prevent backflow of blood into the right ventricle

cardiac muscle cells

shorter and wider than skeletal muscle cells and contain special junctions called intercalated discs; anchored by desmosomes

allow ions to pass through and transmit depolarizing current across the heart

What do gap junctions in cardiac muscle cells do?

autorhythmic cells

stimulus for cardiac muscle cells to contract comes from _______________, which depolarize spontaneously and rhythmically

pacemaker potential

slow depolarization of autorhythmic cells due to both opening of sodium channels and closing of potassium channels. it is never a flat line

-40mv

what is the threshold for autorhythmic cells that triggers the beginning of an action potential once reached?

autorhythmic depolarization

pacemaker potential reaches threshold, fast calcium channels open and reverse membrane potential, leading to an action potential

a decrease in calcium permeability and an increase in potassium permeability

autorhythmic repolarization occurs when there is:

100x/min

the sinoatrial node of the heart depolarizes approximately _________ when denervated

75x/min

the sinoatrial node of the heart depolarizes approximately ________ at rest

Sinoatrial Node

Generates the fastest rate in the heart and sets the pace for heart rate-AKA the Pacemaker

Atrioventricular Node

This node relays impulses from SA node down to the ventricles at a 0.1 second delay to allow the atria to contract before the ventricles; without input from the SA node, it depolarizes approximately 50x/min

atrioventricular bundle

the only electrical connection between the atria and ventricle; also called Bundle of His. Without input from the AV node it will depolarize approximately 30x/min

bundle branches

fibers that conduct electrical impulses down the interventricular septum

Purkinji fibers

fibers that run up the ventricular walls and initiate ventricular depolarization that leads to cell to cell transmission via gap junctions

fibrillations

rapid, irregular contractions of the heart are called

atrial fibrillation

irregular and rapid heart rate that commonly causes poor blood flow to the body; the atria beat chaotically and irregularly out of sync with the ventricles; symptoms include shortness of breath and weakness; not usually life threatening

ventricular fibrillation

rapid, erratic electrical impulses that cause the ventricles to quiver uselessly instead of pumping blood, causing plummeting blood pressure; blood supply to vital organs is cut off and patient will collapse within seconds; can be fatal if not treated swiftly with CPR and defibrillation to restore normal cardiac rhythym

ectopic focus

condition in which some other area of the heart besides the SA node assumes control of heart rate and may become hyper-excitable; often caused by stimulants like caffeine, nicotine, etc

heart block

damage to AV node that prevents the passage of impulses from the atria to the ventricles; the ventricles will contract too slowly for adequate blood circulation; requires artificial pacemaker

conduction system, autonomic nervous system

basic heart rate is set by the ________________, and modified by the _____________

heart rate and force of contraction

sympathetic cardiac nerves originating in the medulla oblongata increase:

decrease

parasympathetic nerve fibers (namely the vagus nerve)_________________ heart rate

contractile depolarization

membrane potential of contractile cells goes from -90mv to +30mv by opening voltage regulated fast sodium channels, which quickly close

contractile plateau phase

voltage change from the closing of fast sodium channels causes opening of slow calcium channels in the sarcolemma, allowing extracellular calcium into the cell; the cell remains depolarized due to closing of most potassium channels; this provides sustained contraction needed to eject blood from the heart

contractile repolarization

occurs when calcium channels in contractile cells close and potassium channels open. The efflux of potassium brings the membrane potential back to its resting voltage

electrocardiography

method of detecting electrical currents generated in the heart; forms a composite of all electrical activity in the heart

P wave

ekg wave indicating depolarization wave from the SA in the atria

QRS Complex

ekg wave that reflects ventricular depolarization beginning at the apex of the heart; obscures atrial repolarization which is happening simultaneously

T wave

ekg wave indicating ventricular repolarization

P-Q Interval

ekg interval marking the beginning of atrial contraction to the beginning of ventricular excitation

S-T segment

ekg segment during which the entire ventricular myocardium is depolarized

Q-T Interval

ekg interval starts at the beginning of ventricular depolarization through repolarization

a damaged heart

any changes in ekg readings indicate:

junctional rhythm

ekg rhythm reflecting a nonfunctional SA node; P waves are absent and the AV node paces the heart at 40-60 bpm

second degree heart block

ekg reading indicating a partial failure of the AV node to conduct SA node impulses; usually two P waves for each QRS wave because the AV node conducts some SA node impulses but not all

ventricular fibrillation

ekg reading indicated disorganized electrical activity; chaotic, grossly abnormal ekg deflections; seen in acute heart attack and after an electrical shock

systole

contraction of myocardium

diastole

relaxation of myocardium

cardiac cycle

all events associated with one complete heartbeat

stroke volume

indication of force of contraction of the ventricles; amount of blood pumped by each each ventricle per beat

heart rate and stroke volume

cardiac output can be calculated by multiplying:

hypocalcemia

low blood calcium; shortens the duration of action potentials and decreases the efficiency of the heart

hypercalcemia

high blood calcium; prolongs the plateau of action potentials; causes heart irritability and heart fatigue due to increased contractions

hyperkalemia

high blood potassium; causes heart block

hypokalemia

low blood potassium; causes abnormal rhythms and feeble heart beats

heart attack

blood flow to a section of heart muscle becomes blocked; if bloodflow isn’t quickly restored, the muscle becomes damaged from lack of oxygen and begins to die; mostly caused by coronary artery disease

coronary artery disease

long term fatty plaque buildup on the inside walls of coronary arteries; rupture of the plaque can cause a blood clot to form which may cause a heart attack

atherosclerosis

plaque buildup in the arteries

angina

chest pain or discomfort that occurs when not enough blood is flowing to the heart muscle; can feel like painful pressure of squeezing in the chest shoulders, arms, neck, jaw, or back

heart failure

the heart cannot pump sufficient blood to the body with enough force; serious and requires medical attention

arteries, capillaries, veins

name the three major types of blood vessels

capillaries

the only blood vessels that directly serve cells are:

tunica interna

innermost endothelial lining of blood vessels; simple squamous epithelium that is continuous with the endocardial lining of the heart; lines the lumen of all vessels producing a slick surface to minimize friction

tunica media

middle lining of the blood vessels; made of smooth muscle cells and sheets of elastin (only in arteries); regulates circulatory dynamics-vasoconstriction and vasodilation

tunica externa

outermost layer of blood vessels; made of loosely woven collagen for protection, reinforcement, and anchoring; contains nerve fibers, lymphatic vessels

elastic arteries

thick walled arteries near the heart (aorta and its major branches); largest in diameter and contain more elastin than any other vessel to smooth out large pressure fluctuations (expand to accept blood, recoil to propel blood)

muscular arteries

deliver oxygenated blood to the organs; account for most of the named arteries; diameter from size of pinky to pencil lead; contain more smooth muscle and less elastic tissue than elastic arteries

arterioles

also called resistance vessels; smallest of the arteries and made mostly of tunica media (mostly smooth muscle with a few elastic fibers); diameter controls blood flow to capillary bed

capillaries

smallest blood vessels made only of tunica interna; allow exchange of gases, nutrients, and hormones between blood and tissues

cartilage, epithelia, cornea and lens of eye, tendons and ligaments

tissues with poor supply of blood capillaries

continuous capillaries

most common capillaries, abundant in the skin and muscles; endothelial cells joined by tight junctions but contain gaps of unjoined membrane called intercellular clefts; allow limited passage of fluids and molecules; these capillaries are completely sealed in the brain

fenestrated capillaries

capillaries with fenestrated endothelial cells-oval windows (fenestrations) allow greater permeability; found in small intestines, endocrine organs, and kidneys

sinusoidal capillaries

very leaky capillaries with large fenestrations, few tight junctions, and large intercellular clefts; allow large molecules to pass through (including RBCs); blood flow through these capillaries is sluggish, which allows for absorption of nutrients and debris removal

microcirculation

flow of blood through capillary beds

vascular shunt

short vessel in the capillary beds that directly connects arteriole and venule

true capillaries

small capillaries that branch off the metarteriole and return to the thoroughfare channel to drain into the postcapillary venule

precapillary sphincters

cuffs of smooth muscle that regulate blood flow through capillary beds

venules

blood vessels made of endothelium and few pericytes; extremely porous; smallest of these is the postcapillary venule

veins

blood vessels containing three tunics (thinner than in arteries) with little smooth muscle or elastin; also called capacitance vessels or blood reservoirs; contain valves to prevent backflow of blood due to low pressure

varicose veins

swollen and dilated veins that become floppy and deformed due to prolonged standing, obesity, or pregnancy; common in lower limbs