1.2 Cardiovascular and respiratory systems 2 Flashcards
What is an autonomic nervous system (ANS)
the part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes.
involuntarily regulates heart rate and determines firing rate of the SA node
-higher firing rate of the SA node higher heart rate
What is the cardiac control centre
control centre in the medulla oblongata that controls the heart rate
Name the 3 main control mechanisms that determine the action of the cardiac control centre
-neural control
-intrinsic control
-hormonal control
What is neural control
chemoreceptors ->detect ^ in acidity in blood
proprioceptors -> detect movement in tendons & muscle fibres
baroreceptors -> detect increase in pressure in blood vessels
What is intrinsic control
temperature changes affect viscosity (thickness) of blood and speed of nerve impulse transmission
venous return changes affect stretch in ventricle walls, force of ventricular contraction, stroke volume
What is hormonal control
adrenaline and noradrenaline- released from adrenal glands-
increase force of ventricular contraction (therefore SV) - increasing spread of electrical activity through heart
What is the vascular system
network of blood vessels and blood
-ensures oxygen and nutrients are delivered to all respiring cells for energy production
- waste is removed efficiently
Name 3 functions of the blood
- transports oxygen and glucose
- protect and fight disease
- maintain the internal stability of the body
What are the three types of blood vessels
- arteries
- veins
- capillaries
What do arteries and arterioles do
transport oxygenated blood from the heart to muscles and organs
Name the main artery and what it does
aorta
-carries blood at a high pressure directly from left ventricle
-subdivides arterioles slowing blood flow
Name 3 characteristics of arteries
- large layer of smooth muscle
- elastic tissue to cushion and smooth blood
- small lumen
Explain what arterioles are
Small branch of an artery leading into capillaries
What are pre capillary sphincters
- ring of smooth muscle surrounding the entry of capillary bed.
- they dilate and constrict to control blood flow through capillary bed
What process occurs in capillaries
gas exchange
-O2 passes through capillary wall & into tissues
-CO2 passes from tissues -> blood through capillary wall
Explain characteristics of capillaries
- walls have a single layer, thin enough to allow gas, nutrient and waste exchange
What do veins and venules do
they transport deoxygenated blood from the muscles and organs back to the heart.
What is vasodilation
the widening of the arteries, arterioles and pre-capillary sphincters
What is vasoconstriction
narrowing of arteries, arterioles and pre-capillary sphincters
What is the main vein
vena cava
Name the characteristics of veins and venules
- small layer of smooth muscle allowing them to venodilate and venoconstrict to maintain the slow flow of blood towards the heart
-veins have one-way pocket valves which prevent backflow of blood
What is venous return
return of blood to the heart through the venules and veins back to the right atrium, largely against gravity
Why is a greater venous return needed during exercise
greater demand for oxygen -> more oxygenated blood requires greater venous return-> so stroke volume, cardiac output can increase.
What are the five mechanisms that aid venous return
- pocket valves - 1 way valves located in the veins to prevent back flow
- smooth muscle - the layer of smooth muscle in the vein wall veno constricts to create veno motor tone which aids the movement of blood
- gravity - the blood that is above the heart is helped to return by gravity
- muscle pump - during exercise skeletal muscles contract compressing the veins located between them squeezing the blood back to the heart
- respiratory pump - during inspiration and expiration a pressure difference between the thoracic and abdominal cavity created. As exercise increases respiratory rate , the respiratory pump as maximised.
How does smooth muscle aid venous return
-found in vein wall -> venoconstricts
-pushing blood back towards heart
How do pocket valves aid venous return
- valves prevent backflow of blood
How does gravity aid venous return
blood from upper body, above heart, helped to return by gravity
How is muscle pump an aid in venous return
during exercise, skeletal muscle contract compressing veins located between them, squeezing blood back to heart
How does the respiratory pump aid venous return
- during inspiration and expiration, pressure difference between thoracic and abdominal cavity is created, squeezing blood back to heart
What is blood pooling
Accumulation of blood in the veins due to gravitational pull and lack of venuos return. This described as heavy legs after exercise
How does a cooling down help recovery
- low intensity exercise maintains muscle and respiratory pump aiding return of blood to heart
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What is cardiac output at rest
5 l/ min
What is the vascular shunt mechanism
redistribution of cardiac output around body from rest to exercise
increases % of blood flow to skeletal muscles
what is the sympathetic nervous system
part of ANS- responsible for increasing HR during exercise
how does vasoconstriction and vasodilation occur
vasomotor control centre (VCC) stimulates vasonstriction and vasodilation to occur
what is the parasympathetic nervous system
part of ANS- responsible for decreasing HR, specifically during recovery
what do arterioles lead to and what does this do
lead to capillary beds- brings blood in close contact with organ and muscle cells
what is blood flow into capillary beds controlled by
pre-capillary sphincters
what 2 things can pre-capillary sphincters do which controls how much blood flows
-constrict- limits blood flow through capillary bed
-dilate- maximises blood flow into capillary bed
what occurs at rest in terms of cardiac output
-high % cardiac output goes to organs - primarily to digest, filter and excrete (75%)
-low % cardiac output goes to muscles
what occurs to cardiac output during exercise
Demand for oxygen and nutrients steps up and more intense the exercise the higher the demand approx 88% at maximum.
what do the aterioles do when the body is at rest
-aterioles to organs vasodilate- increasing blood flow
-aterioles to musces- vasoconstrict- limiting blood flow
what do the pre-capillary sphincters do when the body is at rest
-pre-capillary sphincters dilate- opening up capillary beds to allow more blood to organ cells
-pre-capillary sphincters constrict- closing capillary beds to muscle cells
what is vasomotor control centre
-control centre in medulla oblongata responsible for cardiac distribution
what controls vascular shunt mechanism
vasomotor control centre
what is vasomotor tone
partial state of smooth muscle constriction in arterial walls
what 2 things does the vasomotor control centre receive information from and what info does it receive
-chemoreceptors- regarding chemical changes (CO2 , lactic acid rising during exercise
-barorecptors- regarding pressure changes on aterial walls
describe the steps in which occurs in the vasomotor control of cardiac output in response to exercise
-chemoreceptors detect increase in lactic acid, CO2
-barorecptors detect increased stretch on vessel walls
-send this info to VCC
-VCC uses SNS to increase or decrease sympathetic stimulation to arterioles and pre-capillary sphincters
-sympathetic stimulation = decreased
-arterioles and pre-capillary sphincters dilate
-blood flow to muscle cells increases
-sympathetic stimulation increased
-aterioles and pre-capillary sphincters constrict
-blood flow decreases to organ cells
describe the steps in which occurs in the vasomotor control of cardiac output in response to exercise
-chemoreceptors detect increase in lactic acid, CO2
-barorecptors detect increased stretch on vessel walls
-send this info to VCC
-VCC uses SNS to increase or decrease sympathetic stimulation to arterioles and pre-capillary sphincters
-sympathetic stimulation = decreased
-arterioles and pre-capillary sphincters dilate
-blood flow to muscle cells increases
-sympathetic stimulation increased
-arterioles and pre-capillary sphincters constrict
-blood flow decreases to organ cells
describe what the VCC does when it receives the sensory info from the baroreceptors and chemoreceptors
-sympathetic stimulation will either be increased/ decreased to alter level of vasoconstriction of arterioles, pre-capillary sphincters
why does sympathetic stimulation increase
-to vasoconstrict arterioles, pre-capillary sphincters, to limit blood flow to areas such as muscles at rest
why does sympathetic stimulation decrease
-to vasodilate arterioles, pre-capillary sphincters, to increase blood flow to area such as muscles during exercise
What is the point of venous return mechanisms
work to maximise/ ^ blood flow back to heart
