November 29, 2023 Flashcards
Questions at beginning of lecture:
- Explain to yourself how digitalis works
- Why is training-induced bradycardia such an important adaptation?
Smooth muscle tone:
how much vasoconstriction or vasodilation
how does Smooth muscle tone work
NE binds to alpha1 adrenergic receptors and causes contraction of smooth muscle and narrowing of vessel
Sympathetic drive =
vasoconstriction (increased vascular tone)
Modest vasoconstriction is usually occurring in our bodies at any given time
Metabolites produced by exercising muscle …….
reduces vascular smooth muscle contraction/tone (opens vessels to improve flow)
what are the two metabolites produced by exercising muscle
Adenosine
Potassium
How does Adenosine (metabolite) reduce vascular tone
AMP becomes adenosine when it loses a phosphate (ATP without the phosphate)
This means that adenosine can escape the cell since it is phosphate free
This acts as a metabolite that inhibits the release of NE from sympathetic neurons; no NE means reduction in vascular tone and will widen
How does Potassium (metabolite) reduce vascular tone
inhibits NE release from sympathetic neurons
Central command consists of:
Recruiting motor units so you can exercise
- Sympathetic drive →
- NE release →
- binds to a1 adrenergic receptors on vascular smooth muscle →
- vasoconstriction everywhere
But, in exercising muscle:
- metabolites(ex: K and adenosine) →
- inhibit NE release locally →
- vasodilation →
- increase in blood flow
Vasoconstriction is happening everywhere except where you are exercising
Vasoconstriction and Vasodilation during exercise lead to
a redistribution of blood flow
Mom said: “wait 2 hours after you eat before going swimming!” Why?
competition between redistribution of blood flow
between digestive muscles and skeletal muscles
causes cramps
does brain blood flow increase during exercise?
yes
does skin blood flow increase during exercise
yes
Blood flow increases for heat dissipation or is reduced for heat conservation (depends on environment temp)
Factors that increase blood flow to skeletal muscle as a result of skeletal muscle activity
Metabolic vasodilation
Muscle pump
Increase in sympatho-adrenal system
Deeper Breathing
how does skeletal muscle activity → Metabolic vasodilation → increase BF in skeletal muscle
skeletal muscle activity →
Metabolic Vasodialtion →
↓ total peripheral resistance →
↑ SV →
↑ Q →
↑ BF in skeletal muscle
also because:
easier for heart to eject blood
how does skeletal muscle activity → Muscle pump → increase BF in skeletal muscle
skeletal muscle activity →
Muscle pump →
improved venous return →
↑ SV →
↑ CO →
↑ BF in skeletal muscle
Increase in sympatho-adrenal system → increase BF in skeletal muscle
Increase in sympatho-adrenal system →
↑ cardiac rate and SV →
↑ CO →
↑ BF in skeletal muscle
also:
increases sympathetic vasoconstriction in viscera
redistributes blood flow to places where it’s needed
How does Deeper breathing → increase BF in skeletal muscle
Deeper breathing →
↓ intrathoracic pressure →
Improved VR
↑ SV →
↑ CO →
↑BF in skeletal muscle
MAP =
(HR x SV) x TPR
Metaboreceptors (IV afferents) respond to?
metabolites and help to increase
sympathetic drive to the heart and periphery
Mechanoreceptors (III afferents) respond to
contractile activity leads to increase in
AP frequency which accelerates sympathetic outflow
Mechanoreceptors (III afferents) and Metaboreceptors (IV afferents) are known as
“pressor reflex” and acts opposite to BRR
what is Baroreceptor reflex
have protective mechanisms that prevent over increase in BP
Factors that influence BP Response to Exercise
Amount of active vs. inactive muscle mass
Intensity and duration of contractile effort
The type of contraction; resistance vs. dynamic - determining blood vessel compression and blood distribution
valsalva maneuver and changes in intrathoracic pressure determining venous return to heart
what do the factors that influence BP response to exercise determine:
extent of the pressor reflex
amount of sympathetic drive
degree of vasodilation (reduction of TPR)
Valsalva maneuver
leads to increase in thoracic pressure
