physTest2a

autorhythmic fibers

(cells) cardiac or smooth muscle fibers that are self-excitable (generate impulses without an external stimulus); act as the heart's pacemaker and conduct the pacing impulse throug the conduction system of the heart; self-exciatable neurons in the central nervous system, as in the inspiratory area of the brain stem

cardiac cell resting membrane potential

-90 mV

rapid depolarization, plateau, and repolarization

1) rapid depolarization due to Na+ inflow when voltage-gated fast Na+ channels open 2) Plateau (maintained depolarization) due to Ca2+ inflow when voltage-gated slow Ca2+ channels open and K+ outflow when some K+ channels open 3) Repolarization due to closure of Ca2+ channels and K+ outflow when additional voltage-gated K+ channels open

atrial systole

After the p wave begins, teh atria contract (atrial systole).

Describe autorhythmic cells: the conduction system

An in herent and rhythmical electrical activity is the reason for the heart's lifelong heart beat. The source of this electrical activity is a network of specialized cardiac muscle fibers called autorhythmic fibers b'c they are self-excitable. They repeatedly generate action potentials that trigger heart contractions. Continue to stimulate a heart to beat even after it is removed from the body. ::: conduction system is a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart. The system ensures that cardiac chambers become stimulated to contract in a coordinated manner, which makes the heart an effective pump.

pressure and volume changes

As a chamber of the heart contracts, blood pressure within it increases. Pressures on teh right side are considerably lower. Each ventricle, expels teh same volume of blood per beat.

explan an electrocardiogram

As action potentials propagate throug hthe heart, they generate electrical currents that can be detected at teh surface of the body. ECG is a recording of the electrical signals. It is a composite record of action potentials produced by all the heart muscle fibers during each heartbeat. P wave = atrial depolarization QRS complex = onset of ventricular depolarization T wave= ventricular repolarization

pacemaker

Autorhythmic fibers act as a pacemaker, setting the rhythm of electrical excitation that causes contraction of the heart.

describe action potential initiation by autorhythmic cardiac cells. What are the functions of the autorhythmic fibers

Autorhythmic fibers repeatedly generate action potentials that trigger heart contractions. They have two functions: Act as a pacemaker, setting the rhythm of electrical excitation that causes contraction of the heart. They form the conduction system, a network of specializaed cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart. The conduction system ensures taht cardiac chambers become stimulated to contract in a coordinated manner, which makes the heart an effective pump.

what are the features of the SA node

Cardiac excitation begins in teh SA node, located in the right atrial wall just inferior and lateral to the opening of the superior vena cava. SA node cells do not have a stable resting potential. They repeatedly depolarize to threshold spontaneously, pacemaker potential. When it reaches threshold, it triggers an action potential. Each AP from the SA node propagates throughout both atria via gap junctions in the intercalated discs of atrial muscle fibers.

describe the action potential in a ventricular contractile fiber

FIG 20.11 resting membrane potential is -90 mV. 1) rapid depolarization due to Na+ inflow when voltage-gated fast Na+ channels open 2) plateau (maintained depolarization) due to Ca2+ inflow when voltage-gated slow Ca2_ channels open and K+ outflow when some K+ cannels open

depolarization

Going from very negative to a positive membrane potential (ex -90 to +20) of ventricular contractile fibers. It is due to Na+ inflow when voltage-gated fast Na+ channels open

rapid depolarization

Inflow of Na+ down the electrochemical gradient produces a rapid depolarization. Within a few milliseconds, the fast Na+ channels automatically inactivate and Na+ inflowdecreases

interventricular septum

Internally, the right ventricle is separated form the left ventricle by a partition called the interventricular septum.

what are the features of the purkinje fibers

Large-diameter, rapidly conduct the action potential beginning at the apex of teh heart upward to the remainder of the ventricular myocradium.

beginning with the sinoatrial SA node trace the conduction system through the heartk

OOPS see above :)

repolarization

Recovery of the resting membrane potential during repolarization of a cardiac action potential resembles that in other excitable cells. After delay, additional voltage-gated K+ channels open. Outflow of K+ restores teh negative resting membrane potential (-90) at the same time, the ca channels in the sarcolemma and the SR are closing, which also contributes to repolarization

explain ATP production in cardiac muscle

Relies almost exclusively on aerobic cellular respiration in its numerous mitochondria. The neede oxygen diffuses form blood in teh coronary circulation an dis released from myoglobin inside cardiac muscle fibers. Cardiac muscle fibers use several fuels to power mitochondrail ATP production. ATP comes mainly from oxidation of fatty acids (60%) and glucose (35%), with smaller contributions from alctic acid, amino acids, and ketone bodies. Also some from creatine phosphate. CK is an enzyme that catalyzes transfer of a phosphate group from creatine phosphate to ADP to make ATP.

describe pacemaker potentials and action potentials in the SA node

SA node cells do not have s table resting potential. Rather, they repeatedly depolarize to threshold spontaneously. The spontaneous depolarization is a pacemaker potential. When it reaches threshold, it triggers an action potential. Each action potential from the SA node propagates throughout both atria via gap junction in the intercalated discs of atrial muscle fibers. Following the action potential, the atria contract

list and describe the components of the conduction system

SA node cells repeatedly depolarize to threshold to create a pacemaker potential which triggers an action potential. This causes teh atria to contract 2) by conducting along atrial msucle fibers, action potential reaches the AV node, located in teh interatrial septum. 3) From the AV node, the action potential enteres the AV bundle which is the only site where action potentials can conduct from the atria to the ventricles. 4) The action potential enters both the left and right bundle branches which extend throug hthe interventricular septum toward the apex of the heart 5) Purkinje fibers rapidly conduct the a ction potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward teh semilunar valves.

explain the mechanism of contraction

The electrical activity (action potential) lead to the mechanical response (contraction) after a short delay. As Ca2+ concentration rises inside a contractile fiber, Ca2+ binds to the regulatory protein troponin, which allows the actin and mysoin filaments to begin sliding past one another, and tension starts to develop. substances that alter the movement of Ca2+ through slow Ca2+ channels influence the strength of heart contractions.

mechanism of contraction

The electrical activity (action potential) leads to the mechanical response (contraction) after a short delay. As Ca2+ concentration rises inside a contractile fiber, Ca2+ binds to the regulatory protein troponin, which allows the actin and myosin filaments to begin sliding past. Tension starts to develop. Substances alter the movement of Ca2+ through slow Ca2+ channels influence the strength of heart contractions.

creatine kinase (CK)

The enzyme that catalyzes transfer of a phosphate group from creatine phosphate to ADP to make ATP. Injured or dying cardiac or skeletal muscle fibers release CK into the blood. A sign of a heart attack

what are the contributions of the heart to homeostasis?

The heart pumps blood through blood vessels to all body tissues. It is pumped through the body's blood vessels so that it can reach body cells and exchange materials with them.

atrioventricular bundle (bundle of HIS)

The part of the conduction system of the heart that begins at the atrioventricular (AV) node, passes through the cardiac skeleton separating the atria and the ventricles, then extends a short distance down the interventricular septum before splitting into right and left bundle branches, aka bundle of his

pacemaker potential

The spontaneous depolarization is a pacemaker potential. When the pacemaker potential reaches threshold, it triggers an action potential.

cardiac cycle

a complete heartbeat consisting of systole (contraction) and diastole (relaxation) of both atria plus systole and diastole of both ventricles

the conduction system

a group of autorhythmic cardiac muscle fibers that generates and distributes electrical impulses to stimulate coordinated contraction of the heart chambers; includes the sinoatrial SA node, the atrioventricular AV node, the atrioventricular bundle, the right and left buncdle branches, and the purkinje fibers

AV valves

a heart valve made up of membranous flaps or cusps that allows blood to flow in one direction only, from an atrium into a ventricle:::: lie between atria and ventricles, are the tricuspid valve on the right side of the heart and the bicuspid (mitral) valve on the left

plateau

a period of maintained depolarization. Due in part to opening of voltage-gated slow Ca2+ channels in the sarcolemma. Ca2+ ions move from the interstitial fluid into the cytosol. This inflow causes even more Ca2+ to pour out of the sarcoplasmic reticulum into the cytosol through additional Ca2+ channels in the SR membrane. The increased Ca2+ concentration in cytosol triggers contraction!!!! depolarization is sustained during the plateau phase b'c ca2+ inflow just balances K+ outflow. Lasts for about .25 seconds and membrane potential is ~0 mV. Depolarization in a neuron or skeletal muscle fiber is much briefer, about .001 sec. b'c it lacks a plateau

sinoatrial (SA) node (pacemaker)

a small mass of cardiac muscle fibers (cells) located in the right atrium inferior to the opening of the superior vena cava that spotaneously depolarize and generate a cardiac action potential about 100 times per minute. aka natural pacemaker

SL valves

a valve between the aorta or the pulmonary trunk and a ventricle of the heart

what is auscultation? how do defects of the heard affect teh sounds of the heart?

act of listening to the heart::: Heart murmur is an abnormal sound consisting of a clicking, rushing, or gurgling noise that either is heart before, between, or after the normal heart sounds, or may mask the normal heart sounds.

self-excitable

aka autorhythmic fibers. The source of electrical activity is a network of specialized cardiac muscle fibers that are self-excitable. Repeatedly generate action potentials that trigger heart contractions.

gap junctions

allow muscle action potentials to conduct from one muscle fiber to its neighbors. Gap junctions allow the entire myocardium of the atria or the ventricles to contract as a single, coordinated unit.

gap junctions

allow muscle action potentials to conduct from one muscle fiber to its neighbors; allow the entire myocardium of the atria or the ventricles to contract as a single, coordinated unit.

intercalated discs

an irregular transverse thickening of sarcolemma that contains desmosomes, which old cardiac muscle fibers (cells) together, and gap junctions, which aid in conduction of muscle action potentials form one fiber to the next

Electrocardiogram P wave

atrial depolarization

P wave

atrial depolarization

intrinsic cardiac system

autorhythmic fibers form the conduction system, cardiac fibers that spotaneously depolarize and generate action potentials

what sets the rhythm of conduction system?

autorhythmic fibers: the conduction system:::: The SA node acts as teh natural pacemaker of the heart.

interatrial septum

between the left and right atrium is a thin partition called the interatrial septum. It has the fossa ovalis, the remnant of the foramen ovale, an opening int he interatrial septum of the fetal heart that closes after birth.

what are the features of the right and left bundle branches

bundle branches extend through the interventricular septum toward the apex of the heart

autorhythmic cells

cardiac of smooth muscle fibers that are self-excitable (generate impulses without an external stimulus); act as the heart's pacemaker and conduct the pacing impulse through the conduction system of the ehart; self-excitable neurons in the central nervous sytem, as in teh inspiratory area of the brain stem

ascultation S2 dupp

caused by blood turbulence associated with the closing of the semilunar valves

Explain the correlation of ECG waves and the atrial and ventricular systole

contraction is during the intervals! atria contract during P-Q interval and ventricles in s-t segnment

explain the cardiac cycle

fig 20.14.... a single cardiac cycle includes all the events associated with one heartbeat. THus, a cardiac cycle consists of systole and diastole of the atria plus sytole and diastole of the ventricles

list the parts of the cardiovascular system, their features and functions

heart, blood vessels, and

intercalated discs

hold the cardiac muscle fibers together and enable action potentials to propagate from one muscle fiber to another

systole

in the cardiac cycle, the phase of contraction of the heart muscle, especially of the ventricles

diastole

in the cardiac cycle, the phase of relaxation or dilation of the heart muscle, especially of the ventricles

autorhythmic fibers

inherent and rhythmical electrical activity is the reason for the heart's lifelong beat. The source of the electrical activity is a network of specialized cardiac muscle fibers called autorhythmic fibers b'c they are self-excitable. They repeatedly generate action potentials that trigger heart contractions

ascultation S1 lubb

is associated with closure of the atrioventricular valves

intrinsic cardiac system

k

left atrium

k

left ventricle

k

right ventricle

k

right atrium

l

asculation

listening to the heart; the act of listening to sounds within the body, usually done with a stethescope

what are the features of the AV node

located in the interatrial septum just anterior to the opening of the coronary sinus

the conduction myofibers (purkinje fibers)

muscle fiber (cell) in the ventricular tissue of the heart specialized for condeucting an action potential to the myocardium; part of the conduction system of the heart

how can timing and the strength of the heartbeat be modified

nerve impulses form the autonomic nervous system and blood-borne hormones MODIFY THE TIMING AND STRENGTH of each heartbeat, but don't establish the fundamental rhythm

right and left bundle branches

one of the two branches of the atrioventricular AV bundle made up of specialized muscle fibers (cells) that transmit electrical impulses to the ventricles

what are the features of the atrioventricular bundle = bundle of HIS

only site where action potentials can conduct from teh atria to the ventricles

QRS complex

onset of ventricular depolarization

electrocardiogram QRS complex

onset of ventricular depolarization

ectopic pacemakers

out of the normal....artificial stimulation of the heart to contraction, done by surgery

systole

phase of contraction

diastole

phase of relaxation

pacemaker

sets teh rhythm of electrical excitation that causes contraction of the heart

ventricular diastole

shortly after the T wave begins, the ventricles start to relax (ventricular diastole)

pacemaker potentials

spontaneous depolarization in the SA node. When the pacemaker potential reaches threshold, it triggers an action potential. (-50 mV)

what is the relationship of the action potential and contraction of contractile fibers

the action potential initated by the SA node travels along the conduction system and spreads out to excite the "working" atrial and ventricular muscle fibers, called contractile fibers. An action potential occurs in a contractile fiber as follows.... depolarization, plateau, and repolarization

atrioventricular (AV) node

the part of the conduction system of the heart made up of a compact mass of conducting cells located in the septum between the two atria

refractory period of a cardiac muscle fiber

time interval during which a second contraction can't be triggered.The refractory period of a cardiac muscle fiber lasts longer than the contraction itself. For this reason, tetanus cannot occur in cardiac muscle as it can in skeletal muscle.

explain electrocardiogram: intervals

time span between waves, It represents the conduction time from the beginning of (P-Q) atrial excitation to the beginning of ventricular excitation. It is the time required for the action potential to travel through the atria, av node, and the remaining fibers of the conduction system.

explain electrocardiogram: abnormalities

to detect these problems, continuous ambulatory electrocardiographs are used. This procedure, a person wears a battery-operated monitor that records an ECG continuously for 24 hours. Electrodes BLAH BLAH BLAH! In coronary artery diseas, the T wave may be elevated in hyperkalemia (high blood K+ level) As action potential is forced to detour around scar tissue caused by disorders such as coronary artery disease and rheumatic fever, the P-Q interval lengthens. Q-T interval may be lengthened by myocardial damage, mycocardial ischemia, or conduction abnomalities

T wave

ventricular repolarization

electrocardiogram T wave

ventricular repolarization