Lecture 3 Flashcards
By how much does sympathetic stimulation increase heart rate and contractility? and cardiac output.
Heart rate 2-3 x. Contractility 2 x. Increases CO by 5x.
Inhibiting the sympathetic system will do what to the heart?
Decrease heart rate by 20-40% and moderately decrease contractility.
Parasympathetic stimulation decreases heart rate and contractility by how much?
Can significantly slow or stop heart beat and decrease contractility by 20-30%.
If the parasympathetic system is inhibited, what happens to the heart?
Increase heart rate seven-fold, small increase in contractility.
What is the vasomotor centre?
Centre in the cardiovascular control centre that transmits sympathetic impulses to virtually all arteries, arterioles and veins.
Where is the vasomotor centre located?
Bilaterally in the reticular substance of the medulla and lower third of the pons.
Which vessels do not receive sympathetic innervation?
Capillaries, precapillary sphincters and metarterioles.
What is the aim of sympathetic innervation of blood vessles?
Vasoconstriction to increase resistance and reduce blood flow.
Do veins or arteries have more adrenergic fibres?
Arteries have more
What are varicosities?
They are where neurotransmitter is released from within the smooth muscle walls of vessels.
What receptor does NE act on in the vessels?
Alpha-1.
What signalling cascade does NE on alpha-1 induce?
IP3 pathway leading to increased calcium ions
What are the three neurotransmitters that cause sympathetic vasoconstriction ?
NE, ATP and neuropeptide-Y
What receptor does ATP act on and what happens?
P2X which opens calcium ions
Which type of veins have poor innervation?
Muscle veins
Does sympathetic vasodilation occur in humans?
No
Where specifically within the muscular arteries are the sympathetic vasoconstrictor fibres found?
The adventitia
What are the 4 main endocrine systems that regulate blood pressure?
Adrenaline, ADH, renin-angiotensin-aldosterone, ANP
Where does adrenaline come from?
Adrenal medulla
What receptors does adrenaline act on in the heart?
Beta-1
What receptor does adrenaline act on in the vessels for vasoconstriction?
Alpha-1
What receptor does adrenaline act on in vessels for vasodilation?
Beta-2
What percentages of adrenaline and noradrenaline does the adrenal medulla release?
80% adrenaline, 20% noradrenaline
Which is better at increasing CO, adrenaline from the adrenal medulla or NE from sympathetic system?
Adrenaline from the medulla
Where is ADH produced?
Hypothalamus- supraoptic nuclei and paraventricular nuclei
Where is ADH released from?
Posterior pituitary gland
What is the set point and range for ADH release in osmolar control mechanism?
280-300 mOsm
What is the set point for ADH release in non-osmolar control?
10% blood volume loss.
Does osmolar or non-osmolar control of ADH cause a larger release of ADH?
Non-osmolar control.
What does ADH do?
Causes retention of water and vasoconstriction to increase blood pressure
In a 15% blood volume loss, what does the set point for osmolar control change to?
265 mOsm
In a 15% blood volume increase, what does the setpoint increase to?
290 mOsm
What triggers the RAAS system?
A drop in blood pressure
What organ releases renin?
Kidneys
What does Renin do?
Converts angiotensinogen into angiotensin I
What converts angiotensin I into angiotensin II?
ACE
What organ predominantly releases ACE?
Lungs- high SA of enodtehlial cells
What are the main effects of angiotensin II?
Vasoconstriction, increasing thirst and causes release of aldosterone
