cardiovascular system Flashcards
atrial diastole
•atria relax and expand drawing blood into the atria.
•pressure in atria opens the AV valves
ventricular diastole
•ventricles relax and expand drawing blood into the ventricles.
•semi-lunar valves closed to prevent blood from leaving the heart.
atrial systole
•atria contract forcing blood into ventricles.
ventricular systole
ventricles contract forcing the AV valves to shut and semi lunar valves to open pumping blood into the pulmonary artery and aorta.
the conduction system
1.atria fills with blood, av valves close, atrial pressure rises above ventricular pressure, blood starts to pass into ventricles.
2.SA nose fires electrical impulse across atria, atria contracts, av valves forced open, blood is pumped into ventricles.
3.impulse is received by the AV node, delayed for a moment to allow atrial systole to complete.
4. AV node sends impulse down the right and left bundle of His to the bottom of the heart and the Purkinge fibres.
5. ventricles contract from the bottom upwards, so valves forced open, blood is pumped out of ventricles into PA and A.
artery
•carry’s blood away from the heart.
•elastic walls to cope with high pressures.
•have rings of muscle to allow for vasoconstriction and dilation.
capillary
•tiny, thin walled blood vessels.
•1 cell thick - for gaseous exchange.
•join ateries and veins.
veins
• carry blood back to the heart.
•veins have thinner walls because pressure is lower.
•veins have valves to stop back flow.
plasma
component of blood that holds the blood cells and whole blood in suspension. 55% of total blood volume
platlets
reacts to extreme am bleeding by clotting.
red blood cells
made in bone marrow, contain haemoglobin which carries oxygen and carbon dioxide.
white blood cells
made in bone marrow, cells of the immune system to fight against the disease.
heart rate and amounts
•the number of times the heart beats per minute.
•average = 70bpm
•endurance= 50bpm
stroke volume and amounts
amount of blood ejected from the left ventricle per beat.
at rest = 70ml
endurance athletes = 100ml
cardiac output and amounts
amount of blood ejected from the left ventricles per minute.
at rest & endurance athletes = 5l/min
vasodilation
the widening of the lumen of a blood vessel to increase the volume of blood delivered to active areas
vasoconstriction
the narrowing or the internal diameter (lumen) of the blood vessel to restrict the volume of blood.
vascular shunting
•increased intensity of exercise is detected by receptors
•the receptors relay the message to the vasomotor control centre. the vcc send a message via the sympathies nervous system to decrease stimulation to the arteriole and pre-capillary sphincters at the muscles.
•Vasodilation happens and blood rushes through. the opposite (increased stimulation & vasoconstriction) at the organs.
why is vascular shunting important
•increases the amount of oxygen delivered to the working muscles, allowing them to work aerobically quicker and for longer.
•allows waste products to be removed from the body more efficiently, reducing lactic acid.
neutral factors affecting HR
•chemo, baro and proprioceptors send information is to the VCC which in turn increases stimulation of the SA node via the sympathetic nervous system.
hormonal factors affecting HR
•adrenaline released prior to exercise stimulates the SNS which increases stimulation of SA node, which in turn increases HR.
•adrenaline also increases force of cardiac contractions, increasing SV and Q.
increase temperatures affect on HR
causes increased speed of nerve transmission, which increases stimulation of SA node, increasing HR
increased venous returns affect on HR
increase volume of blood returning, stretches the wall of the heart which increases stimulation of SA node, increasing HR.
venous return
the return of blood to the heart during the cardiac cycle.
2 problems that delay venous return
•blood pressure in the veins is very low.
•most of the blood distributed lower than the heart and therefore has to fidget against gravity to make its way back to the heart.
pocket valves
valves in veins stop the back flow of blood. this means once the blood reaches a certain point it cannot return, if not could result in blood pooling.
skeletal muscle pump
when the muscles in the lower leg contract, they squeeze the surrounding veins and force the blood back to the heart.
smooth muscle
veins are lined with smooth muscle that can venoconstrict and force the blood back towards the heart.
respiratory pump
the pressure of thoracic cavity is increased and forces blood back to the heart. this happens more the higher our breathing rate is.
gravity
blood from above the heart returns via gravity.
Extrinsic factors regulating HR during exercise
- neutral factors
- hormonal factors
Intrinsic facts affecting HR during exercise
- increase temperature
- increased venous return
Stroke volume at sub-maximal
- at the start of exercise sv increases because venous return increases
- during sub-maximal exercise sv then plateaus as HR plateaus
Stroke volume at maximal
- at maximal intensities HR continues to increase which doesn’t leave enough time for ventricles to fill
- less blood in ventricles, therefore less ejected per beat
-results in a decrease in sv. This is known as vascular drift
Cardiac output at submaximal
- cardiac output increases because hr and sv are both increasing
- Q= HRxSV
Cardiac output at maximum intensity
- cardiac output plateaus
- HR continues to rise, but SV falls due to cardiovascular drift
Cardiac output equation
Stroke volume x heart rate = cardiac output
SV x HR = Q
the cardiac cycle
- the sequence of events that occurs when the heart beats
- there are two stages diastole (relaxes) and systole (contracts)
- circulates blood around pulmonary and systematic circuits of the body
functions of blood
- transport nutrients such as o2 and glucose
- protect and fight disease
- maintain homeostasis
HR at submaximal
- steady increases then plateaus at around 120bpm
- steady recovery
HR at maximal
- increases to maximal HR (220-age)
- recovery is a sharp decrease (EPOC) then steadily decreases
starlings law of the heart
- SV depends on venous return - the volume of blood returning to the heart
- during exercise VR increases, so blood is returning to the heart
- this causes the walls of the heart chambers to stretch:
stretch 1 = atria (more blood enters so they stretch this stimulates the SA nose causing it to increase firing rate)
stretch 2 = ventricles (more blood enters so walls stretch causing a more forceful contraction of ventricular walls)
