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cardiac cycle
- the period between the start of one heartbeat and the beginning of the next
- fluids move from an area of higher pressurse to an area of lower pressure
- the pressure within each chamber rises during systole and falls during diastole
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systole or contraction
the chambers contracts pushes blood into an adjacent chamber or into an arterial trunk.
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diastole or relaxation
chambers fills with blood and prepares for the next cardiac cycle
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correct pressure relationships depends on
- the careful timing of contractions
- the hearts elaborate pacemaking and conducting systems normally provide the required spacing between atrial and ventricular systoles
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when cardiac cycle begins all four chambers are
- relaxed
- and the ventricles are partially full with blood
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during atrial systole
- the ventricals are completly filled with blood
- blood cannot flow into the atria because artial pressure exceeds venous pressure
- very little backflow into the veins because blood takes path of least resistance
- then heart enter the atrial distole
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atrial diastole and ventricular systole
- begin at the same time
- ventricles push blood through the systemic and pulmonary circuits and toward the atria
- the heart then enters the ventricular diastole
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ventricular diastole
- filling occurs passively (due to gravity)
- both the atria and ventricles are relaxed
- the next phase is atrial systole which complets the filling of the ventricles
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when the heart rate increases all the phases of the cardiac cycle are
- shortened
- greatest reduction in time spent in diastole
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whats another word for atrioventricular valve
av node
tricuspid valve
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cardiac output (co)
- a measure of how hard the heart is working
- the volume of blood that is ejected from the left ventricle, into aorta each min
- indication of the blood flow through peripheral tissues
- co=sv*hr
- sv- the amount of blood that leaves the heart per contraction
- hr- heart rate (bpm)
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what effects heart rate`
- autonomic innervation
- hormones
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what effects stroke volume
- end diastolic volume
- end systolic volume
- sv= edv-esv
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frank starting law
- the relationshiip between the amount of ventricular stretching and the contractile force means that within physiological limits, increasing the edv results in a corresponding increase in stroke volume
- "more in more out"
- the more the heart is stretched the harder it will contract, forcing more blood out
- cardiac output
- venus return
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venus return
60% of blood sites in veins at rest
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autonomic control
- control center loacted in the medulla oblongta- help monitor and control heart rate
- recieves messages from parasympathic and sympathic system
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proprioreceptors
- looks at body position
- tells the body that its at rest so heart rate is low, but when body move it tells the body to speed heart rate up
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chemoreceptors reflex (o2, co2,ph)
- responds to changes in carbon dioxide,, oxygen , or ph levels in blood and cerbrospinal fluid.
- sensory neuron
- located in the carotied bodies, situated in the neck near the carotied sinus, and in hte aortic bodies, nerar the arch of the aorta
- monitor the composition of arterial blood.
- additional chmoerecptors loacated on the ventrolater surfaces of the medulla oblongata monitor the composition of csf
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baroreceptor reflexes
- specialized recptors that monitor the degree of stretch in the walls of expanable organs.
- pressure recptors making sure the body have enoough blood pressure
- adjust cardiac ooutput and peripheral resistance to maintain normal arterial pressures
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sympatheic nervous system
- run from the medulla to sa node
- norepinehren is the neurotransmitter in the sns
- increase hr
- increase in calcium entry , increasing the force of contraction
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parasympatheic nervous system
- impulse travels via vagues nerve (x)- wondering nerve
- release acetycholine
- causes a hyperpolarization .of pacemaker cells
- therefor slowing hr
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how hormones play a role in chemical regulation
epinephrin, thyroid causes increase in heart rate
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how do ions play a role in chemical regulation
- calcuim increase hear rate
- sodium and patassuim decrease heart rate
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other factors that invole in hr
- age- hr in infants starts hig then slowdown in mid life the increase in older adults
- sex-males have higher hr
- exercise- lowers resting heart rate
- templ- increasing temp increases hr decrease in temp decrease hr
- disease
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