Heart Physiology Flashcards
Heart Coordination
movement of blood is determined by the sequence of muscle contractions
- atria contracts first then the ventricles
Do muscle contractions happen in a certain order?
yes
What happens in the contraction of the cardiac muscle?
it compresses the chamber increasing the pressure and the blood flows from high to low pressure
stimulation of the heart
1.heart at rest
2. atria stimulated
3. atria contract
4. ventricles stimulated
5. ventricles contract
Cardiac muscle action potentials
changes in membrane permeability are responsible for producing action potentials and called pacemaker potential
Depolarization Phase
- Na+ channels open
-Ca2+ channels open
Plateau Phase
-Na+ channels close
- some K+ channels open
Ca2+ remain open
Repolarization Phase
-K+ channels are open
-Ca2+ channels close
what does the plateau phase do?
prolongs action potential by keeping Ca2+ channels open
action potential for cardiac and skeletal muscles
cardiac- 200-500msec
skeletal- 2msec
Conduction system
Contraction of the atria and ventricles is coordinated by specialized cardiac muscle cells in the heart wall that form
can all cells of the conduction system produce spontaneous action potential?
Yes
conduction system include
sinoatrial node ,atrioventricular node , atrioventricular bundle, right and left bundle branches, and purkinje fibers
SA node
- in RA
-where action potential originates
-functions as a pacemaker
-large number Ca2+ channels
AV node
-located in the lower portion of the right atrium
-action potentials from SA node sent to this node
-slow rate of action potential conduction
Atrioventricular bundle
-action potentials from AV node travel by the AV bundle to the ventricles
- AV bundle divides into a left and right bundle branches to left and right ventricles
Purkinje fibers
- at the tips of left and right bundle branches , are purkinje fibers
- purkinje fibers pass to the apex of the heart and then extend to the ventricle walls
- action potentials are rapidly delivered to all the cardiac muscle of all the ventricles
AP path through the Heart
- SA node
- AV node
- AV bundle
- Right and left bundle branches
- Purkinje fibers
what keeps a record of electrical events in heart, and uses electrodes
ECG (EKG)
p wave
depolarization of atria
QRS complex
-depolarization of ventricles
-contains QRS waves
T wave
depolarization of ventricles
what is the summative description of all events that occur during one single heartbeat?
cardiac cycle
Cardiac muscle contractions produce pressure changes within OR outside of the heart chambers?
within
Are the pressure changes responsible for blood movement?
Yes
does blood move from low to high pressure?
No (high to low pressure)
atrial systole
contraction of atria
ventricle systole
contraction of ventricles
atrial diastole
relaxation of atria
ventricular diastole
relaxation of ventricles
true/false: heart sounds are produced due to the opening of the heart valves
False: it is the closure
first heart sound
Lubb
second heart sound
dubb
look at the heart valve locations
stroke volume
- volume of blood pumped per ventricle per contraction
- 70 milliliters/ beat
heart rate
- number of heart beats in 1 min.
-72 beats/min.
cardiac output
-total volume of blood pumped by the heart in 1 min.
-5 liters/min.
CO=SV*HR
cardiac output = stroke volume * heart rate
how is the heart regulated?
autonomic nervous system innervation of the SA node
parasympathetic- CN X
sympathetic- sympathetic chain
heart reflexes
the body senses changes in internal conditions and signals to the heart through the ANS to either increase or decrease heart rate
baroreceptors
- monitor blood pressure in the aorta and carotid arteries
-involves the medulla oblongata
baroreceptors reflex when bp increases
HR and SV decrease
baroreceptors reflex when bp decrease
HR and SV increase
Chemoreceptor refles
-involves chemical regulation of the heart function
-chemicals can affect HR & SV
-medulla oblongata has chemoreceptors for changes on pH and CO2
coronary artery disease
-decreases blood supply to the heart
-coronary arteries are narrowed for some reason
myocardial infarction ( heart attack)
-due to closure of 1+ coronary arteries, thrombus or blockage
-area of cardiac muscle lacking adequate blood supply die, and scars (infarct)
angioplasty
procedure opens blocked blood vessels
stent
structures inserted to keep vessels open
bypass
procedures reroutes blood away from blocked arteries
