L14 - Control of Circulation Flashcards by Jack Corston

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

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What are two key differences between and artery and a vein

In the artery there is more elastic tissue and more smooth muscle

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What does resting tension mean

What vessels possess it

The balance between the contraction of the smooth muscle and the elastic recoil
All vessels

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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

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What is meant my metaboite regulation

Several metabolites are able to cause dilation/constriciton of the vessesl

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What is this low level of designed to give, what can this be called

Constant level of flow

Also known as autoregulation

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What are most vessels tonicallt innervated by

Sympathetic adrenoreceptor input (alpha receptors)

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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

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What is the effect of parasympathetic stimulation of blood vessels supplying erectile tissue / glands
What NT is involved in this

Vasodialtion

Ach involved

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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

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What is the adrenal medullary hormone most involved in the control of circulation

Adrenaline

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What is the effect of adrenaline at the skin and other viscera

Vasoconstriction

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What is the effect of adrenaline at the skeltal muscle and liver

Vasodilation

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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

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What reaction is adrenaline responsible for;

Summarise

Defence reaction

Blood diverted to heart, skeletal muscle and the liver

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Give an example of a kinin

Bradykinin

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What is the effect of bradykinin

It is a vasodilatory peptide

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What is the effect of angiotensin 2 on the blood vessels

Vasoconstriction leading to an increase in blood pressure

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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