Nervous And Hormonal Control Of Vascular Tone

Question 1

What are the local controls of vascular tone?

Answer 1

Myogenic responses, paracrine and autocrine and physical factors (temp/shear stress)

Question 2

What are the extrinsic controls of vascular tone?

Answer 2

Parasympathetic, sympathetic and sensory vasodilator nerves, sympathetic vasoconstrictor nerves, adrenaline, angiotensin II, vasopressin and atrial natriuretic peptide

Question 3

What does paracrine affect?

Answer 3

Things very close to the source

Question 4

What does autocrine mean?

Answer 4

A cell producing a substance that affects itself

Question 5

How does local control of vascular tone work?

Answer 5

Regulates local blood flow to organs/tissues and is important for regional hyperaemia.
Vasodilators are used

Question 6

What does extrinsic vessel control regulate?

Answer 6

Total peripheral resistance to control blood pressure. The brain selectively alters blood flow to veins according to need

Question 7

What causes extrinsic control in nerves?

Answer 7

Vasoconstrictors like noradrenaline

Vasodilators like acetylcholine and nitric oxide

Question 8

What hormones cause extrinsic control in blood vessels?

Answer 8

Vasoconstrictors like adrenaline and angiotensin I

Vasodilators like anti-natriuretic peptide

Question 9

What is the pathway for the sympathetic vasoconstrictor system from the brain to the sympathetic ganglia?

Answer 9

Signal comes from the medulla oblongata down the main excitatory drive. Splits at the thoracic (T1-L2) spinal cord and either goes down a sympathetic preganglionic fibre or into the adrenal medulla

Question 10

What do varicosities contain?

Answer 10

• angiotensin II that act is on AT1 receptors to increase noradrenaline
• metabolites prevent vasoconstriction to maintain blood flow
• noradrenaline can also negatively feedback itself via alpha 2 receptors to limit its own release

Question 11

What are sympathetic vasoconstrictor nerves controlled by?

Answer 11

The brainstem

The rostral ventrolateral medulla is controlled by other areas like the caudal ventrolateral medulla and hypothalamus

Question 12

What does tonic mean?

Answer 12

One action potential per second

Question 13

What activity sets vascular tone?

Answer 13

Tonic sympathetic activity

Question 14

What are the main roles of sympathetic vasoconstrictor nerves?

Answer 14

• Distance sympathetic pathways innervate different tissue
• precapillary vasoconstriction
• control resistance arterioles
• controls venous blood volume

Question 15

What does pre capillary vasoconstriction lead to?

Answer 15

Downstream capillary pressure drop so increased absorption of interstitial fluid into blood plasma to maintain blood volume

Question 16

How do control resistance arterioles work?

Answer 16

Allowing vasodilation to occur and controlling total peripheral resistance

Maintains arterial blood pressure and blood flow to the brain, myocardium and kidneys

Question 17

How does control of venous blood volume work?

Answer 17

Venoconstriction leads to decreased venous blood volume increasing venous return. This increases stroke volume via starlings law

Question 18

How does vasodilation normally occur?

Answer 18

By an inhibition of the sympathetic vasoconstrictor nerves

Question 19

What type of tissues contain vasodilator nerves?

Answer 19

Tissues that have a specific function controlling a specific vascular bed

Question 20

What part of the nervous system do vasodilator nerves generally belong to?

Answer 20

Parasympathetic

Question 21

What happens when blood vessels are innervated by parasympathetic cholinergic fibres?

Answer 21

Release acetylcholine which then binds to muscarinic receptors on the smooth muscle and/or endothelium

Question 22

What can M3 receptors on the vascular endothelium be coupled to?

Answer 22

The formation of nitric oxide which causes vasodilation

Question 23

What type of receptor vasodilates in response to ACh?

Answer 23

M5 muscarinic

Question 24

What is an example of a sympathetic vasodilator nerve?

Answer 24

Skin (sudomotor fibres)

Question 25

How do the sudomotor fibres work?

Answer 25

Release ACh and vasoactive intestinal peptide, causing vasodilation via NO associated routes

Question 26

What does increased blood flow cause in the skin?

Answer 26

More sweat and allows heat loss

Question 27

What has some control over the sudomotor fibres in the head, face and upper chest and what do they cause?

Answer 27

Emotional centres are involved in blushing

Question 28

What glands release ACh and vasoactive intestinal peptide?

Answer 28

Salivary glands

Question 29

What releases just vasoactive intestinal peptide?

Answer 29

The pancreas and intestinal mucosa

Question 30

What do male genitalia release for vasodilation?

Answer 30

NO

Question 31

How does vasodilation work in male genitalia?

Answer 31

NO causes production of cGMP which leads to vasodilation .

Question 32

How does sildenafil (viagra) work?

Answer 32

Inhibits the breakdown of cGMP by phosphodiesterase 5

Question 33

What are sensory vasodilator fibres (nociceptive C fibres) involved in?

Answer 33

Stimulation of sensory axon reflex by trauma or infection etc

Question 34

What do nociceptive C fibres cause release of?

Answer 34

Substance P or calcitonin gene- related peptide (CGRP)

Question 35

What do nociceptive C fibres act on?

Answer 35

Mast cells to release histamine or the endothelial and vascular smooth muscle

Question 36

What are the three things in the Lewis triple response?

Answer 36

Local redness, wheal and flare

Question 37

How does the Lewis triple response work?

Answer 37

When there is trauma, an action potential will be sent to both the dorsal root ganglion and down the axon collateral. The axon collateral then causes release of substance P and mast cell degranulation

Question 38

What are the hormonal vasoconstrictors?

Answer 38

Adrenaline, angiotensin II and vasopressin

Question 39

What are the hormonal vasodilators?

Answer 39

Atrial natriuretic peptide, insulin, estrogen, relaxin

Question 40

When is adrenaline released?

Answer 40

During exercise and fight or flight response Hypotension and hypoglycaemia

Question 41

What are the main roles of adrenaline?

Answer 41

Glucose mobilisation, stimulation of heart rate and contractility during normal exercise and as a vasodilator of coronary and skeletal muscle arteries

Question 42

What does adrenaline do in most tissues (and with what receptor)?

Answer 42

Vasoconstrict alpha 1

Question 43

What does noradrenaline do in most tissues (and with what receptor)?

Answer 43

Vasoconstrict alpha 1

Question 44

What does adrenaline do in skeletal muscle and coronary circulation(and with what receptor)?

Answer 44

Vasodilation beta 2

Question 45

What does noradrenaline do in skeletal muscle and coronary circulation (and with what receptor)?

Answer 45

Vasoconstrictor alpha 1

Question 46

What are the effects of IV adrenaline on circulation?

Answer 46

Cardiac output goes up TPR goes down Not much effect on blood pressure

Question 47

What is the effect of IV noradrenaline on circulation?

Answer 47

Increase in blood pressure Decrease in heart rate Increase in TPR Cardiac output decrease

Question 48

What does RAAS stand for?

Answer 48

Renin-angiotensin-aldosterone system

Question 49

Give the steps of RAAS

Answer 49

Stimulus causes kidneys to release renin, which combines with angiotensinogen in the liver to produce angiotensin I Angiotensin converting enzyme then converts that to angiotensin II

Question 50

What does NTS stand for?

Answer 50

Nucleus tractus solitarius

Question 51

How is vasopressin released?

Answer 51

Stretch receptors in the left atrium send continuous signals to the NTS. NTS sends out inhibitory signals to the CVLM, which stimulates the pituitary gland to release vasopressin

Question 52

What is the hypothalamus response to vasopressin stimulated by?

Answer 52

An increase in osmolarity

Question 53

Where is vasopressin released from and what does this cause?

Answer 53

Posterior of the pituitary gland which causes increased reabsorption of fluid by kidney and causes vasoconstriction. Both effects maintain blood pressure

Question 54

Where is the NTS?

Answer 54

In the medulla

Question 55

What does ANP stand for?

Answer 55

Atrial natriuretic peptide

Question 56

What is AMP released by?

Answer 56

Specialised atrial myocytes

Question 57

What do stretch receptors act as?

Answer 57

ANP receptors on vascular smooth muscle cells increasing the cGMP pathway