Mairead - Neural and Hormonal Control of Vasculature Flashcards
What is the goal of the CVS regulation?
To ensure blood flow changes occur:
- at an appropriate time
- in the right area
- without drastically affecting blood flow to vital organs
What factors are involved in the regulation of CVS function
Local factors
Neural factors
Hormonal factors
Write about how local factors are involved in the regulation of CVS function
(4)
Result in a change in blood flow pattern in
response to a change in metabolism.
Called autoregulation.
Provides an immediate and localised
adjustment in perfusion
If this fails, neural factors work
What is autoregulation
A change in blood flow pattern in response to a change in metabolism
What does autoregulation do
Provides an immediate and localised adjustment in perfusion
When do neural factors work
If local factors fail
Write about how neural factors are involved in the regulation of CVS function
(4)
They result in a change in blood flow between
regions of the body.
Neural factors change blood flow in response to changes in blood pressure and blood
gases.
This is mediated by an ANS change.
ANS output changes Cardiac Output and
Peripheral Resistance
What affect do neural factors have
They change blood flow between regions of the body
Neural factors change blood flow in response to what
Response to changes in blood pressure and blood gases
What is responsible for changing blood pressure and blood gases
This is mediated by an ANS change
ANS affects what values
Cardiac Output and Peripheral Resistance
Write about how hormones are involved in the regulation of CVS function
(6)
Enhance the short term response and
Direct the long term response.
Affect cardiac output and peripheral resistance and in the longer term regulate blood volume and blood composition.
In addition to barororeceptors and chemoreceptors…
Volume change detected as pressure and osmolarity (osmoreceptors) in renal tissue and
hypothalamus.
Gas disturbance (O2) detected in renal tissue
What do hormones do in general
Enhance the short term response of ANS
Direct a long term response
What do hormones affect in the CVS
(4)
Cardiac output
Peripheral resistance
Blood volume
Blood composition
What exactly is stress
Increased physical demand
What will bring on stress
(5)
Exercise
Fever
Haemorrhage and dehydration
Tumour growth
Psychological stress
What is the demand and or change in exercise?
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What is the short term response to exercise?
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What is the long term response to exercise?
bob
What is the demand and or change to tumours
bo
What is the long term response to tumours
bou
What is the blood change/response to haemorrhage/dehydration
bo
What is the short term response (nervous) to haemorrhae/dehydration
buo
What is the long term response to haemorrhage/dehydration
bio
Comment on autoregulation and local factors
(4)
Make minute to minute adjustments in blood flow.
Vasodilation and vasoconstriction of precapillary
sphincters.
Usually operate within the capillary bed.
Vasodilation at a local level is brought about by products
of metabolism
What products of metabolism bring about vasodilation at a local level in capillary beds
(7)
Gases (low O2 and high CO2)
Lactic acid, H+
NO, histamine
K+
Rising temperature
Why do products of metabolism being about vasodilation
These factors relax smooth muscle of arterioles and improve nutrient supply
What brings about vasoconstriction at a local level
(2)
Prostaglandins and thromboxane
Endothelins
Write about prostaglandins and thromboxane in vasoconstriction
These are released by platelets and WBCs to contain inflammation
Write about endothelins in vasoconstriction
These are released from damaged endothelial cells
They have their effect on smooth muscle of arterioles within a tissue or organ
What are the functions of autoregulation
(2)
Protects the capillaries from high pressure
Ensures adequate O2 supply
Define autoregulation
The maintenance of nearly normal levels of blood flow despite marked changes in arterial pressure
What is long term regulation of blood flow?
(3)
A response to sustained high blood pressure
A response to chronically overactive tissue
Why is long term regulation of blood flow needed
To gradually increase blood supply to match the metabolic need
Comment on angiogenesis factor
Increases vascularity
Has been isolated from cancerous tissue
Write a note on regulation of blood flow through skeletal muscle
Decreased blood flow when muscles contract and constrict arterioles
Skeletal muscle have alpha- and Beta- adrenergic receptors
Alpha-adrenergic receptors vasoconstrict at rest
B-adrenergic receptors vasodilate
Write about the neural mechanisms of regulating CVS
Regulated by the ANS CVS regulatory centres of the
hypothalamus and brainstem.
Cardiac regulation by altering the
cardioacceleratory output or the cardioinhibitory
output of medulla oblongata.
Blood Vessel diameter is regulated by the
vasomotor centre in MO. This alters
vasoconstriction or vasodilation.
Heart and Blood vessels have ANS tone. This
means that the ANS is active at rest and can be
regulated.
Respiratory centres in the pons and medulla
oblongata
What are the CVS regulatory centres?
Hypothalamus
Brainstem
How does the hypothalamus and brainstem regulate the CVS
By altering the cardioacceleratory output or the cardioinhibitory output of medulla oblongata
The blood vessel diameter is regulated by what?
The vasomotor centre in medulla oblongata
What does the vasomotor centre in the medulla oblongata do
(2)
Regulates the blood vessel diameter
Thus alters vasoconstriction or vasodilation
Heart and blood vessels have ANS tone, what does this mean
This means that the ANS is active at rest and can be regulated
Where are the respiratory centres in the brain?
In the pons and medulla oblongata
Write a note on reflex control of CVS
(5)
Reflex Control of CVS Function is in response to
changes in blood pressure or changes in blood
gases (or blood pH).
Bainbridge (atrial) Reflex is the response to
raised venous return.
Barroreceptor Reflexes are the response to
blood pressure change.
Chemoreceptor reflex is the response to blood
gas composition.
If the pressure and gases are reduced by a
reduction in blood volume a further long term
response may be required
What is reflex control of CVS function done in response to?
(3)
Changes in blood pressure
Changes in blood gases
Changes in blood pH
What is the Bainbridge (atrial) reflex?
The response to raised venous return
What are the Barroreceptor reflexes
The response to blood pressure change
What is the chemoreceptor reflex
The response to blood gas composition
What may be required if the pressure and gases are reduced by a reduction in blood volume?
A further long term response may be required
What is the response to raised venous return
Bainbridge reflex
What are the response to blood pressure change
Barroreceptor reflexes
What is the response to blood gas composition
Chemoreceptor reflex
Write a note on the Baroreceptor reflex
(3)
Sensory stretch receptors in the walls of the blood vessels perceive change in pressure
Receptors are found in
- the aortic sinus
- the carotid sinus
- the walls of the Right Atrium
- JGA of the Kidney
When these receptors are stimulated the reflex adjust the blood pressure and may also require a blood volume adjustment
Where are baroreceptors found?
(4)
The aortic sinus
The carotid sinus
The walls of the right atrium
JGA of the kidney
What happens when baroreceptors are stimulated?
The reflex adjusts the blood pressure and may also require a blood volume adjustment
How does the nervous system control blood flow in response to elevated blood pressure
(4)
Decrease CO by stimulation of the parasympathetic and inhibition of the sympathetic
division.
Widespread peripheral vasodilation by inhibition
of the sympathetic.
Dilation of the veins
Result is ↓ CO (by ↓hr and/or ↓ SV) and ↓ blood
pressure
How does the nervous system control blood flow in response to when blood pressure falls
(4)
Increase CO by stimulation of the sympathetic and inhibition of the parasympathetic (cardiac)
Peripheral vasoconstriction by stimulation of the sympathetic (vasomotor centre)
Result is in ↑CO (by ↑HR and ↑ SV) and ↑ blood pressure.
May also include venoconstriction to move some of the venous reserve
What do chemoreceptors and osmoreceptors do?
Respond to changes in CO2, O2, Na+ and pH of the blood and CSF
Where are chemoreceptors and osmoreceptors located
(5)
The carotid bodies
Aortic bodies
Medulla oblongata (central chemoreceptors)
JGA of the Kidney
Hypothalamus (central osmoreceptors)
Write a note on the nervous control of blood gases
(5)
If blood O2 decreases and CO2 and H+ increases
the cardiac, vasomotor centres and the respiratory
centres are stimulated.
Homeostasis is restored by increasing CO and
increasing blood pressure.
Increased blood flow to skeletal muscle will result
in decreasing of the total peripheral resistance.
AND
The respiratory centre is also stimulated to
increase CO2 elimination and O2 pickup
What does decreased O2, increased CO2 and H+ stimulate?
Cardiac, vasomotor centres and the respiratory centres
How is blood gas homeostasis restored?
Increasing CO and increasing blood pressure
What happens when there is increased blood flow to skeletal muscle?
This will result in decreasing of the total peripheral resistance
What happens when the respiratory centre is stimulated?
It will increase CO2 elimination and O2 pickup
What is the short term response to lowered blood volume
To maintain the circulation by maintaining cardiac output and blood pressure
Nervous control mainly
What is the long term response to lowered blood volume
Response is to restore blood volume (and pressure) and blood composition (plasma proteins, fluid and formed elements)
Endocrine control mainly
What hormones are involved in the control of CVS function in response to fluid disturbance
(5)
Adrenaline and noradrenaline
Anti-diuretic hormone
Renin-angiotensin-aldosterone system (RAAS)
Erythropoietin
ANP and BNP
What physiological parameters can be changed in response to fluid disturbance
(5)
Vasoconstriction/vasodilation
Heart rate and stroke volume adjustment
Fluid retention/loss
Increased/decreased ingestion of salt and water
Replacement of cells and plasma proteins
How does adrenaline and noradrenaline affect fluid balance
These are released from the adrenal medulla as part of the flight and fight response
They prolong and extend the nervous response
How do adrenaline and noradrenaline act to change fluid balance?
(4)
Increasing cardiac output
Increasing blood pressure
Elevating available energy
Shifting fluids to important areas
Write a note on antidiuretic hormone
Produced in the hypothalamus and released from the posterior pituitary gland in response to nervous stimulation
When is ADH released
(3)
Increased osmolarity of the extracellular fluid (detected by osmoreceptors in the hypothalamus)
Decreased arterial pressure in the hypothalamus
Stimulation by the hormone angiotensin
What detects increased osmolarity of the extracellular fluid
Osmoreceptors in the hypothalamus
How does antidiuretic hormone work
(3)
Increasing water reabsorption in the descending convoluted tubule and collecting duct of the kidney
Vasoconstriction (in response to acute lowering of blood pressure)
Stimulation of thirst
Renin is released from where?
The JGA of the kidney
Renin is released from the JGA of the kidney in response to?
(4)
Decreased blood flow and pressure in the kidney
Reduced GFR
Decreased Na+ in the filtrate
Stimulation of sympathetic ANS
What does Renin do?
Convert inactive angiotensinogen to angiotensin I in the blood
What is ACE
Angiotensin converting enzyme
What does ACE do?
Angiotensin I is converted to Angiotensin II in the lung capillary tissue
What does Angiotensin II do?
(4)
Stimulates the release of aldosterone from adrenal cortex
Stimulates vasoconstriction
Promotes ADH release
Promotes thirst -> ingestion of fluid
What does aldosterone do?
(3)
Increases salt reabsorption in the kidney
Increases the sensitivity of the tongue salt receptors
Stimulates ADH release
Where is EPO produced?
In the JGA of the kidney
When is EPO produced?
In response to low blood partial pressure of oxygen (PO2)
When will low blood oxygen happen?
(3)
Renal blood flow is decreased
In anaemia
In lung problems e.g. at high altitude
EPO works in the bone marrow to do what?
(2)
Stimulate RBC number and increase the rate of maturation of RBC’s
EPO therefore restores blood volume and improves the O2 carrying capacity of the blood
What is the response to stretching of the Atrial Pressure receptors
(4)
Increase venous return stretches the receptors
Results in increase of sympathetic outflow (Bainbridge reflex)
CO increases by increased HR and SV
Reflex release of ANP and BNP hormones also strives to reduce blood volume by inhibition of ingestion of fluid and by increased urinary output
What hormones are responsible for reducing blood volume by inhibition of ingestion of fluid and by increased urinary output?
ANP
BNP
What happens in fluid overload
(2)
Over ingestion
Renal failure
What does ANP stand for?
Atrial Natriuietic peptide
What does BNP stand for?
Brain Natriuretic peptide
When and from where is ANP released
ANP is released from the atria of the heart in response to stretching during systole
(high blood volume and pressure is sensed)
From where is BNP released
From the ventricles
What are the ANP and BNP responses
(5)
Decrease CO and blood pressure
Increased GFR
Natriuresis
Increased water loss at the kidney (by inhibition of ADH)
Depressing the thirst response
What is natriuresis
Increased Na+ loss at the kidney (by inhibition of Aldosterone)
Explain the neural and hormonal reflex responses to haemorrhage
(What is the physiological problem?)
Low ventricular return
Loss of plasma proteins
Low Partial pressure of oxygen (PO2)
Explain the neural and hormonal reflex responses to haemorrhage
(What reflexes are activated?)
Short term response to low blood pressure
Long term response to raised blood Na+, low GFR, low PO2
