Kinesiology 06
Terms
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- atrium
- small thin muscular upper chambers of the heart which beat before the ventricles.
- ventricle
- lower, thick walled, very strong muscular chambers of the heart. responsible for the majority of the blood pumping action of the heart.
- aorta
- The large, thick walled blood vessel that carries oxygenated blood from the top of the heart, to the rest of the body.
- artery
- large thick walled blood vessels that cary oxygenated blood supply from the heart to the tissues of the body.
- vein
- thin walled blood vessels that carry blood back to the heart to be reoxygenated. veins have a system of valves that allow the blood to return to the heart without backflow.
- capilliaries
- smallest vessels of the blood system that connect arteries with veins
- atrioventricular valve
- prevents blood from flowing back into the atria during ventricular contraction. the right atrioventricular valve is a tricuspid valve, the left is a bicuspid.
- papillary muscle
- prevents the heart valves from leaking
- chordae tendinae
- tendons that connect the valve leaflets of the heart to the papillary muscles.
- semilunar valves
- prevent blood from flowing back into the heart after ventricular systole
- ventricular systole
- contraction of the ventricles, forcing blood into the pulmonary artery and the aorta.
- diastole
- period of relaxation when chambers are filling with blood.
- end diastolic volume.
- volume of blood left in ventricles after the diastolic period, just prior to systolic contraction.
- end systolic volume.
- volume of blood left in the ventricles after systolic contraction.
- cardiac output
- total volume of blood pupmed into the aorta every minute.
- stroke volume
- totale volume of blood pumped with each beat.
- total peripheral resistance
- absolute resistance to blood flow from left ventrical to the right atrium.
- ECG
- electrocardiogram - electrical measurements of heart potential during the cardiac cycle.
- pwave
- clear electrical wave of depolarization that spreads across the atria while the heart is still full of blood, just before the end of the diastolic period, and immediately prior to the contraction of the atria.
- atrioventricular node
- at junction of atria and ventricles, a node which is a system of conducting fibres that serves to spread electrical activity very quickly over the ventrical.
- bundle of His
- specialized group of fibres leaving the AV node and travelling down either side of the inter ventricular septum to quickly deliver an electrical impulse to the entire ventricles, so that they may have an immediate and coordinated contraction.
- purkinje system
- the smaller fibres that the bundle of His branch into. distributes the electrical depolarization simultaneously between L&R ventricles, so that all ventricle fibres contract simultaneously.
- pacemaker potential.
- ction potential created by the sinoatrial or SA node is a pacemaker potential because the action potential functions to regulate the hearts rhythm. The SA node spontaneously drifts towards its threshold potential, to set off an action potential in the heart, thus starting the heartbeat sequence and rhythmically regulating the beating of the heart.
- sinoatrial node
- SA node - small specialized area of the heart in the right atrium near the veinous entrance. is responsible for initiating the electrical activity of the cardiac cycle.
- cardiac action potential
- -40mV. from resting potential of -60mV
- refractory period
- in heart muscle depolarization lasts the entire time of the contractile response. long slow period in the heart when another signal cannot be sent from the SA node. modulated by acetylcholine which increases heart membrane K+ permeability, causing it to leak out, and depolarize the membrane. vice-versa norepinephrine.
- tetanus
- cannot occur in heart muscle due to the long refractory period which disallows repeated signals / action potentials. this allows the heart to pump.
- arrythmias
- irregularities of heart rhythm.
- ectopic focus
- when the heart beat originates somewhere other than the SA node.
- beta blockers
- If norepinephrine, a hormone released into the bloodstream during stress, reaches the beta receptors of the heart, this chemical signal can cause cardiac arrythmias such as rapid and/or irregular heart beats. Beta blockers then are a class of drugs which are used to treat these irregularities of heartbeat, or arrythmia. These drugs work by disallowing the effect of the hormone norepinephrine on the beta receptors by not allowing the two to chemically make contact.
- ventricular fibrillation
- multiple uncoordinated electrical waves that cause the ventricle to behave more like a bowl of jelly than a pump. causes death if not corrected, as blood cannot pump.
- systolic pressure
- maximum pressure obtained in the aorta
- diastolic pressure
- lowest pressure obtained in the aorta
- aortic valve
- the semilunar valve which stops blood from flowing back into the heart after ventricular systole
- arteriosclerosis
- stiffening of the arteries as part of aging.
- pulse pressure
- difference between the systolic (highest) and diastolic (lowest) pressure in the cardio vascular cycle.
- mean blood pressure
- approximately the diastolic pressure plus one third of the difference between the diastolic and systolic.
- heart sounds
- 1st sound is the atrioventricular valve closing. second is the closure of the aortic valve. Lub-dub sound.
- murmur
- sound produced by abnormal blood flow caused by an incompletely closed valve.
- hypertension
- high blood pressure - causes increased risk of heart attack and stroke.
- trace blood flow through heart. specify chambers, valves, vessels, and function of each.
- into right atria via superior and inferior vena cava, floods into right ventricle. right atria pumps rest of blood through to right ventricle, right atrioventricular tricuspid valve closes. ventricle contract, forcing the blood out through the pulmonary semilunar valve through the right and left pulmonary arteries which carry the blood to the lungs. semi-lunar valve then closes. blood reenters the left side of the heart from the lungs via the pulmonary veins, into the left atria. blood floods in through the open left atrioventricular bicuspid valve, then the left atria contracts, pumping its blood into the left ventricle. the bicuspid valve then closes, and the ventricle contracts, forcing the blood out through the aortic semi-lunar valve, to be distributed through the body. The aortic semilunar valve then closes, and the cycle repeats. The cycle is begun by a wave of electrical signal spreading from the SA node in the right atria.
- describe how activity in the SA node ensures rhythmic contraction of the heart.
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The sinoatrial node ensures that cardiac rhythmic contraction occurs by slowly and spontaneously changing its membrane potential from its resting potential of around -60mV to the action potential threshold of about -40mV. When this action potential threshold is reached, the action potential initiated begins the cardiac cycle, and the sinoatrial membrane again repolarizes. This process repeats, ensuring repetitive rhythmic contractions of the heart.
This consistent cycle of electrical depolarization and repolarization is the mechanism which allows us to use a defibrillator to initiate a depolarization as a means to re-start the human heart. - describe the mechanism behid the vagus nerve's influence on the heart.
- heart rate decrease. reduces rate at which heart drifts towards action potential, by use of acetylcholine. increases membrane permeability to K+, which diffuses out, causing hyperpolarization, which slows the heart.
- what is the significance of the AV node delay?
- allows atrial systole to complete.
- why is the ventricular conduction system important?
- allows contraction simultaneously, which allows pumping.
- what special features of cardiac tissue allows electrical impulses to be conducted from cell to cell?
- intercalcated discs: desmosomes, and gap junctions.
- as a person ages, diastolic and systolic blood pressures change. explain.
- As a person ages, systolic blood pressure increases and diastolic blood pressure decreases. This is due to a stiffening of arteries (arteriosclerosis) that is a natural part of the aging process. This stiffening of the arteries means that the blood vessels are no longer as flexible to expand to support the output volume of the heart, nor are they as elastic as they once were so that they easily return to resting size once the blood has passed. In order to drive the blood then through the stiffened vessels, the systolic pressure must increase. Because the vessels also don't recoil as easily, they are not as able to 'buffer' the dropping pressure of the blood. Instead, blood pressure quickly drops to zero. With the arteriosclerosis of aging, the gap between systolic and diastolic pressure generally increases.
- Explain why tetanus can occur in skeletal muscle, but cannot occur in cardiac muscle. Why is tetanus a "wanted" behaviour in skeletal muscle, but not in cardiac muscle?
- Tetanus can occur in skeletal muscle but not in cardiac muscle due to fundamental differences in the membranous structure that cause very different effects with regard to membrane potential reactions. An electrical stimuli causing an action potential within a skeletal muscle occurs and is completed very quickly, coming back to below the threshold potential about .005 of a second after the stimulation, giving it a very short refractory period, which means that additional stimuli may initiate additional action potentials within this time period, causing a sustained reaction or flexing of the skeletal muscle. However, with the heart muscle, there is a sustained period of repolarization of the membrane, which substantially lengthens the refractory period, thus preventing additional stimuli, repeated action potentials, and a sustained "flex" of the heart muscle. This difference is extremely important, as while tetanus may be desired in a skeletal muscle because it causes increased strength and longevity of flex, this same mechanism if present in the heart muscle, would cause death. The heart would be unable to function to pump blood throughout the body in a rhythmic fashion if it were subjected to the prolonged "flexing" action potential mechanism present in skeletal muscle.
- compare atrial and ventricular fibrillation. why is one more clinically significant than the other.
- atrial - smaller, less area, not as much pumping - mechanism more passive. Ventricular, very serious. More clinically signifant = causes death.