Cardio-vascular system Flashcards
two circuits in heart
dual pump moving blood through separate circuits:
- pulmonary circuit
- systemic circuit
pulmonary circuit
carries deoxygenated blood to lungs
carries oxygenated blood back to heart
systemic circuit
carries oxygenated blood to body
carries deoxygenated blood back to heart
atrial systole
both atria contract to force blood into the ventricles
ventricular systole
- when both ventricles contract to eject blood
- into the pulmonary artery + aorta
- for transportation around the circulatory systems
diastole
relaxation phase - blood enters the atria from the vena cava + pulmonary vein
explain the cardiac systole using atrial systole, ventricular systole and diastole
- atrial systole - atria contract which forces blood into the ventricles
- ventricular systole - ventricles contract which pumps blood out of the heart/ into the aorta + pulmonary artery to the body + lungs
- diastole - relaxation phase where atria + ventricles relax which allows blood to enter heart
is the heart myogenic?
yes
myogenic
the heart has the capacity to generate its own electrical impulse which is transported through the cardiac muscle to stimulate contraction
conduction system - how many stages?
3/4 stages:
stage 1: SA node - DIASTOLE
stage 2: AV node - ATRIAL SYSTOLE
stage 3: bundle of His - VENTRICULAR SYSTOLE
stage 4: Purkinje fibres - VENTRICULAR SYSTOLE
conduction system - stage 1
sino-atrial (SA) nodes sends an impulse across the atria which stimulates them to contract
DIASTOLE
conduction system - stage 2
the impulse arrives at the atrioventricular (AV) node, where its delayed, allowing the ventricles to fully fill with blood
ATRIAL SYSTOLE
conduction system - stage 3/4
the impulse travels down the bundle of HIs located in the septum
VENTRICULAR SYSTOLE
conduction system - stage 4
the impulse travels along the Purkinje fibres and cause the ventricles to contract
VENTRICULAR SYSTOLE
HR
heart rate = no.of times the heart beats in a minute
resting value =
stroke volume
amount of blood ejected from the heart per beat
resting value = 80-120ml = e.g. 80ml
cardiac output
amount of blood ejected from the left ventricle per minute
heart stroke x stroke volume = cardiac output
resting value =
describe the conduction system in 10 steps
- SA node sends an impulse
- impulse spreads across the atria
- atria contracts
- impulse stimulates the AV node
- impulse is delayed
- ventricles fill with blood
- impulse travel along the bundle of His
- impulse travels along the Purkinje fibres
- impulse stimulates the ventricles to contract
- blood is pumped out of the ventricles
Heart rate regulation
- heart is myogenic will continue to beat without tiring
cardiac control/ regulation of heart rate = HR needs to increase/ decrease:
- automatic nervous system (INS) involuntarily regulates HR + determines firing rate of SA node = higher the firing rate, higher the HR
- CCC located in medulla oblongata changes our HR
- 3 control mechanisms:
- neural control
- intrinsic control
- hormonal control
neural factors: regulation of HR
CCC (in medulla oblongata) is informed by:
- HR is regulated by ANS
- baroreceptors = respond to increase in BP in blood vessels
- proprioceptors = respond to muscle activity in tendons, muscle fibres + joints
- chemoreceptors = respond to increase in acidity/ decrease in pH in blood
- increase HR by stimulating SA node via sympathetic nerves
- decrease HR by inhibiting SA node via parasympathetic nerve
- SA node increases firing rate/ HR
hormonal factors: regulation of HR
2 hormones released from adrenal gland:
- direct effect on the force of contraction of heart
- thus increases stroke volume
- thus increases the firing rate of the SA node
- thus increases HR
= will increase cardiac output + oxygenated blood to working muscles
- adrenaline = increases HR by stimulating the adrenergic receptors + SA node
- noradrenaliine = released during stressful situations in order to increase the HR = prepare the body to deal with situation
intrinsic factors: regulation of HR
core temperature of body controls HR:
- too high = HR increases in order to increase blood flow to skin where heat can be lost
3 main blood vessels
- arteries
- veins
- capillaries
arterioles
- subdivisions of arteries (transport oxygenated blood from heart to muscles + organs)
- have large layer of smooth muscle = allows arteries + arterioles to vasoconstrict + vasodilate
- this regulates blood flow + controls pressure
- have a ring of smooth muscle surrounding the entry of a capillary bed called PRE-CAPILLARY SPHINCTERS
pre-capillary sphincters
the ring of smooth muscle, surrounding the entry of a capillary bed, that arterioles have
- dilate + constrict to control the blood through the capillary bed
veins
- blood vessels carrying deoxygenated blood from working muscles + organs back to heart
- have small layer of smooth muscle allowing them to VENOdilate + VENOconstrict to maintain slow flow of blood towards the heart
- one-way pocket valves = prevent backflow of blood
capillaries
bring blood slowly into close contact w/ muscle + organ cells for gaseous exchange
- capillary walls are 1 cell thick
- single layer cells
- thin enough to allow gas, nutrient + waste exchange
- link artery-arteriole-capillaries-venule-veins
venous return
return of blood to the heart through venules + veins back to the right atrium = against gravity
venous return mechanisms
- pocket valves
- muscular pump
- respiratory pump
- smooth muscle
- gravity
pocket valves - venous return mechanisms
one way valves located in veins which prevent backflow of blood
muscular pump - venous return mechanisms
the contraction of skeletal muscles during exercise which compresses the veins forcing blood back towards the heart
respiratory pump - venous return mechanisms
during inspiration + expiration = pressure difference between the thoracic + abdominal cavities is created, which squeezes blood back towards the heart
smooth muscle - venous return mechanisms
layer of smooth muscle in the walls of the veins helps maintain pressure in the vein = squeezes blood back (transporting) to heart
gravity - venous return mechanism
blood from the upper body, above the heart, returns towards the heart with the help of gravity
vascular shunt mechanism
- the redistribution of cardiac output around the body from rest to exercise
- which increases the percentage of blood flow to the skeletal muscles
aka. redistribution of blood flow from one area of the body to another
vasoconstriction
narrowing of the blood vessels to restrict blood flow
vasodilation
widening of blood vessels to increase blood flow
Starling’s Law
increased venous return leads to a increased stroke volume, due to an increased stretch of the ventricle walls + therefore force of contraction
blood pooling
blood sitting in pocket valves due to not performing active recovery
venous return importance
- prevent blood pooling
- help increase stroke volume = increase cardiac output
- essential so that blood can return to the right side of the heart via the vena cava to become reoxygenated and travel to working muscles to meet the greater demand during exercise
Karvonen’s principle
training HR = resting HR + %( HR max - resting HR)
