Lecture 11 - Controlling regional blood flows Flashcards
why do we need high constant blood pressure?
To direct blood where we want it to go throughout the body
To meet metabolic demand
Full arteries
pressure & flow
High pressure
Full control of flow
Not full arteries
pressure & flow
Low pressure
Lack of control of flow
2 key reasons why we need high arterial blood pressure
Drive the difference of pressure between one system to another which causes good flow throughout
High pressure in arterial system provides control to move blood where we want it to go
If lose the difference in pressure
lose the flow to extremities (brain)
Systemic circuit
Many systems in parallel
Distribution of cardiac output at rest
Parallel circuit (eg 5000 ml/min) at rest
(blood distribution to organs, brain, kidney, GI tract, Skeletal muscle, skin)
Brain receives (700ml/min)
Most blood to Kidney, GI tract, Skeletal muscle
Low in skin (less than brain)
Distribution of cardiac output at rest. Systemic circuit
Blood flow is distributed into each group
Sum of blood in = sum of blood out
Same number of blood flow in = same number of blood flow out
Cardiac output
Amount of blood the heart is pumping out into the arteries
Blood flow the systemic circuit works with
Cardiac output of systemic circuit .. at REST
most and least blood distribution to organs, brain, kidney, Abdominal viscera, Skeletal muscle, skin, other tissues
More blood to Kidneys, Abdominal viscera, Skeletal muscle
Less is looping back to the heart
750 is going to brain
A bit to the skin and other tissues
Cardiac output of systemic circuit…LIGHT EXERCISE blood flow compared to rest
(increase/decrease brain, kidney, Abdominal viscera, Skeletal muscle, skin, other tissues, heart)
Great Increase in Skeletal muscle (majority)
Increase heart
Increase skin
Decrease in kidney
Decrease in Abdominal Viscera
Decrease other tissues
Same in brain (no change)
Why does more blood go to Skeletal muscle when exercising?
meet metabolic demand
Why when exercising you get more blood flow to skin?
Thermoregulation
Burning a lot of ATP and creating a lot of heat
Internal temperature increases
To remove that heat send more blood to the skin and heat is dissipated to the air around us
Blood flow of systemic circuit…HEAVY EXERCISE blood flow compared to rest
(increase/decrease brain, kidney, Abdominal viscera, Skeletal muscle, skin, other tissues, heart)
Massive increase in Cardiac output
Great increase to skeletal muscle (majority)
Increase to heart
Increase in skin
Decrease in kidneys
Decrease in Abdominal Viscera
Decrease in other tissues
Same in brain (no change)
If the amount of blood has greatly increased does that mean all organs will increase
No demands on organs metabolic demand
As we exercise, to meet a more physiological demand we see
Increase in blood flow to skeletal muscle, heart, skin
Decrease in blood flow to GI tract, Kidneys
Constant flow to brain
Divergent flow of blood depends on
metabolic needs
How is MAP controlled during exercise?
Systemic circulation
Increase CO
Decrease TPR
Constant MAP
What is resistance involved in?
controlling regional blood flows
Rest to exercise
resistance in arteries leading to skeletal muscle
The resistance in arteries leading to skeletal muscle decreases (want more flow to go into SM)
what organs have decreased resistance and increased blood flow?
Skeletal muscle
Heart
Skin
What organs have increased resistance and decreased blood flow?
Kidneys
GI tract
Intestines
Spleen
Arterioles
Resistance vessels
has smooth muscle
Able to expand or contract to determine how much resistance the flow has when into the capillaries.
Luminal radius between veins and arteries
Inside vessel
Different
Circumference between veins and arteries
Same in both
Large luminal radius
Less resistance to flow
Less pressure
Small luminal radius
more resistance to flow
more pressure
Artery
Blood flow to an organ or region is controlled by adjusting
arteriolar (vascular) tone and radius
Vasodilation
Vessel dilated / open Relax smooth muscle Increase diameter, more flow through vessel, Interior space in muscle gets larger Small resistance More flow
Vasoconstriction
Vessel smaller internal radius
Smooth muscle contracts
Big resistance
Less flow
Why does Majority of the blood moves to the skeletal muscle during exercise?
Vasodilation of all arterioles leading into SM
Massively increases flow
Why do kidneys have less blood flow?
Vasoconstriction of the arterioles leading in kidneys and GI tract
Reduces amount of flow to the areas
Increasing resistance
What controls vascular resistance?
Mechanical (response to force) - Local
Neural (central)
Humoral (central)
Mechanical (response to force)
From within vessel (blood pressure)
From outside vessel (swelling)
Local
Increase blood pressure puts force on vessels
Arterioles sense that and can vasodilate
To decrease resistance out of vessel and relieve some of that pressure
Swelling (some capillaries bleeding) puts some pressure on vessels
Arterioles sense that swelling
Vasoconstrict to that area
To decrease amount of flow
Local
Control vascular resistance close to the arterioles
Specific arterioles affected by that mechanical change
Central
Big changes throughout system
Neural
Humoral (blood)
Neural
Brain Control vascular resistance by communicating with arterioles
Vascular sympathetic nerves
Tell to dilate at same time
Rapidly get signal from brain to arteriole to increase the flow by decreasing resistance into particular organs
Humoral (blood)
Movement of hormones throughout system
Adrenaline (fight or flight)
Dangerous situation secrete adrenaline which binds at arterioles
Vasodilate
Arterioles leading into SM and heart
More blood into the specific organs
why do Mechanisms allow arterioles to vasodilate or vasoconstrict leading into specific capillary beds into specific organs?
Always get the correct flow of blood into those organs to meet metabolic demand
