cardiovascular system Flashcards
Cardiac conduction system
- impulses start at the sinoatrial node
- electrical impulses spread through the heart
- atrial systole; sinoatrial node spread to the walls of the atria
- impulses pass through the atrioventricular node
- impulse goes down to the bundle of his
- this branches out into the purkinje fibres
- ventricular systole
Factors affecting the change in rate of conduction system
- Sympathetic nervous system
- Parasympathetic nervous system
- Medulla oblangata
sympathetic nervous system
fight or flight= increase heart rate
Parasympathetic nervous system
Relax and chill= returns heart rate to its resting rate
nervous system
Central nervous system & peripheral nervous system
complex network of nerves and cells
cardiac control centre
coordinates the CNS & PNS
responsible for regulating the heart
located in the Medulla oblongata
Neural mechanisms
- Baroreceptors
- Chemoreceptors
- Proprioceptors
Chemoreceptors
detect a change in blood acidity caused by an increase/ decrease in CO2
chemo receptors- increase in CO2
Increase in heart rate
Baroreceptors
detect changes in arterial blood pressure
Baroreceptor - blood pressure falls
arterial pressure increases (arteries vasoconstrict)
Proprioceptors
detect an increase in muscle movement
Located in muscles, tendons and joints
Proprioceptor - increase in muscle movement
Increase in heart rate
Chemoreceptors - increase CO2
Baroreceptor - decrease in arterial pressure
Proprioceptor- increase muscle movement
Chemoreceptor - increase heart rate
Baroreceptor – decrease heart rate
Proprioceptor - increase heart rate
Stroke volume
volume of blood pumped out of the heart per contraction
Venous return
volume of blood returning to the heart via the veins
Starlings law
- Increased venous return
- greater diastolic filling
- cardiac muscle stretched
- more force of contraction
- increased ejection fraction
Average resting heart rate
72 BPM
Factors that control heart rate
- Neural controls
- hormonal controls
- intrinsic control
Cardiac output (Q)
volume of blood pumped out by the heart ventricles per minute
Q=SV x HR
Cardiac output (Q)
at rest
70 x 72= 5040ml
Cardiovascular drift
- period of exercise
- heart rate & stroke volume initially increases
- fluid lost as sweat
- resulting in reduced plasma volume
- reduced venous return & stroke volume
- Heart rate increases to compensate
- cardiac output increases due to more energy needed to cool
Vascular system
two types of circulation
- Pulmonary
- systemic
Pulmonary circulation
deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart
Systemic
oxygenated blood to the body from the heart and return of deoxygenated blood from the body to the heart
Blood pressure
the force exerted by the blood against the blood vessel wall
blood flow x resistance
Systolic pressure
pressure in arteries when the ventricles are contracting
Diastolic pressure
pressure in arteries when the ventricles are relaxing
Venous return mechanisms
- skeletal muscle pump
- respiratory pump
- pocket valves
Venous return during exercise
venous return increases
Vascular shunt mechanism
redirecting of blood to the skeletal muscles that require more oxygen during exercise
Vasomotor centre
blood pressure and blow flow is controlled by the vasomotor centre. located in the medulla oblongata of the brain. during exercise chemical changes such as CO2 and lactic acid increases. these are detected by chemoreceptors. these receptors stimulate the vasomotor centre which will redistribute blood flow through vasodilation and vasoconstriction.
A-VO2 difference
difference between oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the heart.
