Coordimated Cardiovascular Responses Flashcards
Upon standing up, the cardiovascular system changes due to the effect of gravity, what are the effects
-blood pressure falls first due to postural hypertension there is a lack of blood flow to the brain leading to fainting
- quickly recovers because of homeostatic mechanism
-baroreflex increases Heart rate, force of contraction and total peripheral resistance
Describe atrial and venous pressure when laying down vs standing up
When laying down atrial and venous pressure is more even throughout the body
Atrial pressure is 95 at the head 100 at the heart 95 at the feet
Venous pressure is 10 at the head , 3-5 at the heart and 10 at the feet
When standing up it is not even
Atrial pressure 60,95,180
Venous 0, 0-5, 90
What is Bernoulli law
Blood flow = pressure energy+ potential energy +kinetic energy
Total energies means blood flows from heart to feet
Explain why there is high pressure in the venous system at the feet
- due to hydrostatic pressure
-pressure is higher at the bottom , magnitude of pressure depends on height of fluid column , the density of fluid and gravity
How does orthostasis cause high blood pressure
-fall in central venous pressure
- decreased end diastolic volume
-decreased stroke volume
-descreased cardiac output
-poor perfusion of brain , dizziness and fainting
What makes postural hypertension worse
- alpha adrenegic blockade, any drug that reduces vascular tone , generalised sympathetic blockade
-varicose veins
-lack of skeletal muscle activity
-reduced circulating blood volume
-increased core temperature
What are the reflex responses to orthostasis
- baroreceptor reflex - Located in carotid sinus of neck and aortic arch , detect changes in blood pressure , send signals to the medulla oblongata in the brain
-AVN responds to changes in blood pressure , vasoconstriction helps increase peripheral resistance and maintain blood pressure,increase in heart rate and contractility to enhance cardiac output
Effect of microgravity on cardiovascular system
-initially: blood returns to the heart easily , which increases atrial/ventricle volume and so preload and afterload , sensed by cardiac mechanoreceptors , ADH and RAAS decrease , ANP and GFR increases
Long term :less blood volume , reduced stress on heart , heart reduces in muscle mass, general drop in BP
on return to gravity:severe postural hypertension due to much lower blood volume and smaller heart
Cardiovascular response to exercise
-increased lung oxygen uptake - increased hr and contraction around the body
-control of bp-
Coordinated dilation - selectively target areas where the oxygen is delivered
What happens during exercise induced tachycardia
-fast feedback to brain is being carried out
-increased sympathetic activity to SA and AV nodes
-sympathetic activity increases stroke volume
-increased end diastolic volume
-faster ejection
-decreased end systolic volume
Static exercise v dynamic
Static -one specific muscle group is worked , higher bp , local metabolic hyperaemia
Dynamic - constantly shortening and relaxing different muscle groups involved, lower bp , lower sympathetic tone
Demands of the cvs during exercise and how they are met
-increase lung oxygen Uptake : increased heart rate and stroke volume
-increase oxygen transport around the body :increased extraction of oxygen from blood Bohr shift
-direct oxygen supply to exercising muscle : lower vascular resistance in exercising muscle
Stabilisation of BP:vasoconstriction in non exercising and non required tissue
