PHYS20008 Lecture 18: PHYS20008 Lecture 18
10 May 2018
School
Department
Course
Professor
Lecture 18
- Lying position to standing position is more difficult for humans because we stand
upright, bipedal, a lot of blood pools in legs
- MAP: affected by how much we are pumping into arteries (cardiac output) and how
much we constrict arterioles going to organs (total peripheral resistance)
- Increase total peripheral resistance: more difficult for blood to come out and increase
pressure
- Cardiac output: heart rate (how many beats per minute) x stroke volume (how much
blood volume pumped out per beat, factor of venous return and contractility)
-
- Increase metabolic demand of muscles (skeletal, cardiac) → dilate blood vessels to
organs, move more blood and oxygen through system, delivery of nutrients, building
up waste products (Carbon dioxide ⇒ lungs, water soluble waste products ⇒ kidney,
lipid soluble waste products ⇒ liver), maintenance of body temperature (heat is by
product of metabolism)
- During exercise, activity of sympathetic neurons of the autonomic nervous system
will predominate, and blood vessels will undergo vasoconstriction
- Sympathetic nervous system in general vasocontricts every blood vessel in body
through alpha 1 receptors
- Generalised vasoconstriction throughout entire body → enables us to have specific
vasodilation where our body needs it (tissues require increased blood flow)
- Reduce blood flow to everything → enables us to increase it specifically in areas
where we need to increase blood flow
-
- Feed forward mechanism from brain in anticipation to exercise: respiratory and
cardiovascular parameters begin to change
- Exercise: increasing demand on muscles; generalised vasoconstriction from
sympathetic stimulation of peripheral vessels
- Organs with stable or increased blood flow during moderate exercise: heart (tissues
of heart, coronary arteries through walls of heart), brain (don’t decrease because will
get light-headed, don’t increase because haemorrhage), skeletal muscle (increase to
working skeletal muscles [skeletal muscles not working gets reduced blood flow]),
liver (increased blood flow because of mobilising glycogen energy stores to keep
feeding muscles)
- Kidney takes massive amount of cardiac output (20%, because filter blood)
-
- Organ or tissue can call for more blood for vasodilation: high levels of carbon dioxide,
low levels of oxygen, lactic acid → drop in pH, fatigue metabolites → stimulate vessel
leading into that muscle to dilate, other skeletal muscles not working have arterioles
that stay constricted, reroute blood to where its needed
- Distribution of Carbon Dioxide during exercise
-
Document Summary
Lying position to standing position is more difficult for humans because we stand upright, bipedal, a lot of blood pools in legs. Map: affected by how much we are pumping into arteries (cardiac output) and how much we constrict arterioles going to organs (total peripheral resistance) Increase total peripheral resistance: more difficult for blood to come out and increase pressure. Cardiac output: heart rate (how many beats per minute) x stroke volume (how much blood volume pumped out per beat, factor of venous return and contractility) During exercise, activity of sympathetic neurons of the autonomic nervous system will predominate, and blood vessels will undergo vasoconstriction. Sympathetic nervous system in general vasocontricts every blood vessel in body through alpha 1 receptors. Generalised vasoconstriction throughout entire body enables us to have specific vasodilation where our body needs it (tissues require increased blood flow)
