WEEK 10 Flashcards
(23 cards)
what is the average blood volume for the cardiovascular system?
5 litres
what are the two main goals of the circulatory system
1) meet metabolic demands
2) maintain optimal pressure
what is the equation of the cardiovascular system
MAP= Q X TPR
describe the role of the human body and the heart with cardiovascular system control
human body= resistance
heart= blood flow
what are the 6 differences that occur in the cardiovascular system during exercise?
1- increase of metabolic demands
2- increase cardiac output
3- increase skin flow
4- decreased blood flow to the non- essential tissues
5- increased blood flow to the brain and coronary arteries
6- increased blood flow to the muscle
describe goal 1 of the cardiovascular system : MEETING METABOLIC DEMANDS
- fick equation:
cardiac output x oxygen difference
vo2 is increased by an increase in either central or peripheral factors
central output x peripheral extraction
define cardiac output
the amount of blood pumped by the heart per minute
q= HR x SV
define stroke volume
the volume of blood ejected by the ventricles per contraction
what are the normal values at rest for an untrained male ( heart rate, stroke volume, cardiac output)
heart rate= 72 beats per minute
stroke volume= 70ml per beat
cardiac output= 5,00ml per min
trained males resting values ( heart rate, stroke volume and cardiac output)
heart rate= 50bpm
stroke volume= 100ml per beat
cardiac output= 5000ml per min
what are the 4 factors affecting cardiac output during exercise
1) preload= muscle pump, posture or blood volume
2) afterload= sympathetic and parasympathetic impulses
3) contractility= depressants, loss of myocardium
4) heart rate= chronotropic drugs, sympathetic impulses
what is the stroke volume equation and what is EDV and ESV
SV= EDV- ESV
- EDV ( end diastolic volume) = the amount of blood that collects in a ventricle during diastole
- ESV (end systolic volume ) = the amount of blood remaining in the ventricle after it has contracted
describe preload ( regulation of stroke volume)
1) preload - degree of heart muscle stretch at the end of the diastolic syndrome
stretching muscle fibres:
- increases number of active cross bridge attachments between the actin and myosin
- increases the force of contraction
factors affecting EDV that determine pre load
- vasoconstriction which is controlled by the sympathetic contraction of veins
- muscle pump= rhythmic skeletal muscle contractions compress veins and drive blood towards the heart
- respiratory pump= during inspiration, thoracic pressure and abdominal pressure draws the blood into the thorax
- body position= gravity, prolonged upright exercise leads to decreased venous return = cardiovascular drift
describe after load ( regulation of stroke volume)
- the pressure that must be overcome for the ventricles to eject blood
- high after- loads results in a decreased stroke volume and therefore increase hypertension
describe contractility ( regulation of stroke volume)
- an increase in contractile strength independent of muscle strength and EDV
- increase of calcium
- result of an increased sympathetic stimulation of the heart
what are the 4 factors
1) positive chronotropic factors:
- factors that increase heart rate
2) negative chronotropic factors:
- factors that decrease heart rate
3) tachycardia
- abnormally fast heart rate
- increased body temp
4) bradycardia
- heart rate slower than 60 beats per min
- low body temp, certain drugs, PNS
describe the sympathetic nervous system for regulation of heart rate (X3)
- sympathetic nerve fibres release norepinephrine
- norepinephrine binds to beta one adrenergic receptors in the heart
- SA node fibres more rapidly increasing the heart
describe the parasympathetic nervous system for regulation of the heart rate (x2)
- reduced heart rate
- mediated acetylcholine
describe vagal tone (x2) for regulation of heart rate
- during rest = the sympathetic and parasympathetic divisions are at work but dominant influence is inhibition
- without vagal nerve influence, heart rate would be 25 beats faster
describe hormones (x2) for regulation of heart rate
- epinephrine= released by the adrenal medulla
- produces the same cardiac effects of norepinephrine
describe thyroxine for regulation of heart rate (x4)
- released from the thyroid gland
- increases the metabolic rate and body heart production
- causes a slower but more sustained increase in heart rate
- enhances the effect epinephrine and norepinephrine
what are the 2 factors that control the degree of contractions of vascular smooth muscle
1) locally controlled vasodilation
def= when the metabolic rate of skeletal muscles cells increase during exercise
2) centrally controlled vasoconstriction:
- the arterioles of muscles, skin and viscera are innervated by sympathetic afferent nerves
