cardio vascular system Flashcards
vascular shunt mechanism
redistribution of of cardiac output around the body from rest to exercise which increases the percentage of blood flow to the skeletal muscles
vascular shunt mechanism at rest
- 80% Q to active organs
- 20% Q to active muscles
why is vascular shunt the way it is at rest
organs are active at rest and inactive muscles don’t need increased oxygen
vascular shunt during exercise
80 % Q to active muscles
20 % Q to active organs
why does vascular shunt get distributed at exercise
- active muscles need more oxygen during exercise
- inactive muscles do not need more oxygen
- organs can temporarily cope with less oxygen
how does the vascular shunt mechanism redistribute Q
- using vasomotor control centre
- arterioles of active muscles vasodilate
- pre capillary sphincters of active muscles dilate
- arterioles of organs and inactive muscles vasoconstrict
- PCS of organs and inactive muscles constrict
net effect = more oxygen redistributed to active muscles
arterioles structure
thick middle layer
smooth muscle
arterioles function
vasodilation (widen)
vasoconstriction (narrow)
arterioles affect
increases or decreases distribution of Q to organs or muscles
pre capillary sphincters (PCS) structure
ring of smooth muscle at entry into capillary networks
PCS function
constrict (narrow)
dilate (widen)
PCS affect
increase or decrease distribution of Q to organs or muscles
venous return
venous/deoxygenated blood returning to the heart
what is dependent on venous return
stroke volume (starlings law)
VR mechanisms
skeletal muscle pump
respiratory pump
pocket valves
gravity
smooth muscle
skeletal muscle pump (VR)
squeezes veins situated between muscles aiding vr
respiratory pump
high to low pressure in thoracic cavity to abdominal pump during breathing aiding vr
pocket valves
prevents backfllow of blood aiding vr
gravity
blood above the heart aids vr
smooth muscle
veno -constrict / veno dilate helping vr
how does an increase in vr affect quality of performance
> VR =
SV/Q =
O2 muscle transport =
net effect > exercise intensity or for
anaerobic work < fatigue
how does a decrease in VR affect performance quality
< VR
<SV/Q
<O2 muscle transport
net effect : < exercise intensity or anaerobic < fatigue
what does the VR need to push blood back towards the heart
pressure
what happens if VR has insufficient pressure
blood will sit/ pool within the pocket valve of veins
blood pooling
feeling of ‘heavy legs’
how does blood pooling occur
- the increased cardiac output sent to the muscles pools without sufficient pressure to return it to the heart
during rest - what mechanisms are sufficient enough to maintain VR
- pocket valves
- gravity
- smooth muscle
during or immediately after exercise, what mechanisms does VR need to ensure it’s maintained
- skeletal pump
- respiratory pump
how can we maintain the muscle and respiratory mechanisms after exercise has stopped
active cool down
what maintains the respiratory pump
an elevated respiration rate
what maintains the effect of the muscle pump
continued skeletal muscle contractions
which 2 VR mechanisms are the lost important to help maintain VR
respiratory pump
skeletal muscle pump
- they redistribute cardiac output and prevent blood pooling
where is the autonomic nervous system in the brain
medulla oblongata
neural systems
baroreceptors
proprioreceptors
chemoreceptors
baroreceptors
increase stretch receptors, lungs and increases blood pressure
proprioreceptors
increases motor movement
chemoreceptors
increases ppCO2
decreases O2
decreases pH
intrinsic system
- increases VR
- increases temperature
hormonal system
adrenaline
3 systems of ANS
intrinsic
hormonal
neural
vaso motor control center role 1
- to stimulate arterioles and pre capillary sphincters supplying organs to vasoconstrict
vaso motor control center - role 2
- stop stimulating those supplying muscles, causing them to vaso dilate
- increasing Q to active muscles
- decreasing Q to non essential organs
what are venous return mechanisms for
maximizing blood flow to the heart
- preventing dizziness and maintaining blood pressure
how does smooth muscle aid venous return
- smooth muscle in walls of of veins contract aiding movement of blood
when the respiratory pump aids venous return what happens to breathing
- breathing caused a pressure difference between the thoracic chest cavity and abdominal cavity
how do muscle and respiratory pumps cause changes to venous return during exercise
- more frequent muscular contractions and more deeper breathing causes vr to increase
how do muscular and respiratory pumps cause changed to venous return during recovery
less frequent forceful muscular contractions and deeper breathing so vr decreases
why does a cool down aid venous return
- blood pooling helps blood go continue to move towards the heart
- action of the respiratory pump is maintained above design cleveland’s and gradually decreased as ventilation rate and depth is higher than at rest
- muscle pump action is maintained above resting level and gradually decreases
how does the vascular shunt mechanism distribute blood when exercise begins
vasomotor control
vasodilation
vasoconstriction
constriction
dilation
why does the vascular shunt mechanism redistribute blood during exercise
- muscles of upper body need less oxygen
- less oxygen needed at organs which can cope with a temporary reduction in blood
now does an increase in vr affect the quality of an athletes performance
increased volume of blood entering heart
- walls of atria stretch
- stimulates sa node to increase heart rate
- causes walls of ventricles to stretch
- caused stronger force of contraction
- increasing sv/hr/q
how does the vasomotor control system help redistribution of blood
pass on messages about where blood is needed
