L14 - Control of Circulation Flashcards
What are the two key targets for control
How many layers?
Ateriole resitance and the stored blood in veins as well as the vascular smooth muscle
Multiple layers of control
What are two key differences between and artery and a vein
In the artery there is more elastic tissue and more smooth muscle
What does resting tension mean
What vessels possess it
The balance between the contraction of the smooth muscle and the elastic recoil
All vessels
What is myogenic regulation
When an artery is stretched it evokes a contraction of the smooth muscle causing the artery to return to its original shape
What is meant my metaboite regulation
Several metabolites are able to cause dilation/constriciton of the vessesl
What is this low level of designed to give, what can this be called
Constant level of flow
Also known as autoregulation
What are most vessels tonicallt innervated by
Sympathetic adrenoreceptor input (alpha receptors)
What is the effect of sympathetic stimulation of blood vessels supplying skeletal muscle, heart, lung and kidney
What NT is involved in this
Vasodilation
ACh involved
What is the effect of parasympathetic stimulation of blood vessels supplying erectile tissue / glands
What NT is involved in this
Vasodialtion
Ach involved
What can be said about the innervation density of sympathetic constrictors
Give examples
It varies
E.g. high in cutaneous tissue
low in cerebral tissue
What is the adrenal medullary hormone most involved in the control of circulation
Adrenaline
What is the effect of adrenaline at the skin and other viscera
Vasoconstriction
What is the effect of adrenaline at the skeltal muscle and liver
Vasodilation
Why would adrenaline cause vasodilation at the liver
Because liver stores glycogen ==> increased blood supply to increase glycogenolysis in the liveer to provide the skeltal muscle cells with glucose
What reaction is adrenaline responsible for;
Summarise
Defence reaction
Blood diverted to heart, skeletal muscle and the liver
Give an example of a kinin
Bradykinin
What is the effect of bradykinin
It is a vasodilatory peptide
What is the effect of angiotensin 2 on the blood vessels
Vasoconstriction leading to an increase in blood pressure
How is angiotensin II formed
Formed by enzymes e.g. renin acting on precurrsors when the blood pressure falls
What is the effect of ACE inhibitors
Reduce the ammount of angiotensin II in the blood so reduced blood pressure
What are ACE inhibitors used to treat
Hypertension
What are extrinsic humoural controls of circulation
1) Adrenal medullary hormones
2) Kinins
3) Angiotensin II
What are the local agents which are involved in the extrinsic control
Prostaglandins Serotonin Histamine Endothellium derived relaxing factors Endothellium derived hyperpolarising factors
What is the effect of prostaglandins
Act as vasodilators
What is the effect of serotonin release
When is it released
Platelets release 5-Ht causing vasoconstriction to aid in the formation of clots
What is the effect of histamine
When is it released
Released by mast cells in response to an allergen
Causes vasodilation
What is the effect of endothelium derived relaxing factors
Released after stimulation - by Ach
NO from endothelial cells
Stimulated cGMP in muscles
Causes relaxation
Describe how nitroglycerin can be used clinically
Is converted to NO (increased NO)
Vasodilation
Increased flow
Increased oxygen supply
Describe how slidenafil citrate works - what is its trade name
Inhibits the cGMP breakdown
Causes dilation of the blood vessels
Describe a endothellium derived hyperpolarising factors
Release after stimulations (again by Ach)
Complex pathways
Describe the central control of the control of circulation
Interlinked CNS centres in the brainstem
CNS centres recieve diversive inputs
Emotional responses
Describe how meduallary centres control circulation
Cardioexcitation / inhibition and vasomotor output
What metabolites do medullary centres respond to
pH, CO2 (increase), O2 (decrease)
Describe what else medullary centres may respond to (NOT metabolites)
Raised intercranial pressure, due to swelling, overcome by a fall in blood flow to the brain
What stretch receptors are responsible for the detection of high pressure
Ones in the carotid sinus and the aortic arch
What strech receptors are reponsible for the detection of low pressure
Atria, left ventricle and pulmonary veins
What are the two buffer nerves to the strech receptors
Vagus and the glossopharyngeal
Describe the effect of increased pressure on a stretch receptor
Increased rate of firing
Leads to decrease in vasoconstriction and increase in cardio inhibition
Vasodilation and bradycardia
What are some long term regulatory mechanisms of circulation
Regulation of blood volume by the kidney
What is the valsalva manouveur an example of
How is it performed
Peripheral propriception
Forced expiration against a close glottis
What is another form of proprioception
Chemoreceptors
Normally effect respiration but can also have effects of the heart and vasculature
What is the main higher brain centre involved in the control of circulation - what is it linked to
Hypothalamus linked to the cortex and the limbic system
What does stimulation of the hypothalamic defence area cause
Sympathetic dilation of skeltal muscle
What does stimulation of the hypothalamic thermoregulatory centres causes
If hot –> vasodilation and sweating
If cold –> vasoconstriction and shivering
What does stimulation of the hypomedial preoptic area cause
Sexual responses
What does stimualtion of the anterior cingulate gyrus cause
Bradycardia hypertension and playing dead
