Nervous and Hormonal Control of Blood Vessels

Question 1

What nervous extrinsic controls of blood vessels do we have?

What hormonal extrinsic controls of blood vessels do we have?

Answer 1

Vasoconstrictors like NA / Vasodilators like ACh and NO

Vasoconstrictor A, ANG II, ADH / ANP

Question 2

Explain how the brainstem controls the symp vasoconstrictor system.

Answer 2

The RVLM receives info from the caudo ventrolateral medulla (CVLM), hypothalamus. The RVLM sends info to the thoracic spinal cord intermediolateral (IML). This sends impulses to the symp ganglia then to the adrenal medulla which releases A on alpha 1, beta 2 receptors on BV. The ganglia also send impulses to beta 1 on the heart and to alpha 1, beta 2 receptors on BV directly where NA is released.

Question 3

How does ANG II affect symp activity.

Answer 3

ANG II binds to AT1 receptors and so increases cAMP and thus NA release.

Question 4

Name 6 chemicals that inhibit cAMP and so cause vasodilatation.

Answer 4

K+
Adenosine
PGE1
Histamine
Serotonin
ACh

Question 5

What are the 5 roles of symp vasoconstrictor nerves?

Answer 5

1. Contract resistance arterioles - allows vasodilatation
2. Distinct RVLM neurones-symp pathways innervate different tissues - control blood flow where needed
3. Pre-capillary vasoconstriction - decreases capillary pressure - increase blood volume
4. Control TPR - maintains arterial BP and blood flow
5. Controls venous blood volume - venoconstriction - decrease venous blood volume - increase venous return and so SV.

Question 6

Give 3 areas parasympathetic vasodilator nerves act and what they release.

Answer 6

Salivary glands - ACh/VIP
Pancreas and intestinal mucosa - VIP
Erectile tissue - NO

Question 7

What is the medicinal name for Viagra?

How does it work?

Answer 7

Sildenafil

Enhances the effect of NO by blocking the breakdown of cGMP by phosphodiesterase 5.

Question 8

Where are sympathetic vasodilator nerves found and what do they release?

Answer 8

Skin - sudomotor fibres - ACh/VIP.

Question 9

How do sensory nociceptive C fibres vasodilate?

Answer 9

Stimulation of the sensory axon by trauma/infection - sends info to dorsal ganglion - sends info back same axon then down axon collateral. Substance P release on BV and mast cells. Mast cells release histamine which acts on endothelium and VSM - produces vasodilatation.

Question 10

What is the Lewis triple response?

Answer 10

Local redness
Wheal
Flare

Question 11

Adrenaline is released from the adrenal medulla in what circumstances?

Answer 11

Exercise
FFF
Hypotension (baroreceptor reflex)
Hypoglycaemia

Question 12

Where does Adrenaline vasoconstrict and vasodilate?

Where does noradrenaline vasoconstrict and vasodilate?

Answer 12

Vasoconstriction - most tissue like GIT and skin
Vasodilation - skeletal muscle, coronary circulation
Noradrenaline only vasoconstricts

Question 13

Why are there differences between A and NA?

Answer 13

A has a higher affinity for beta over alpha adrenoreceptors. NA has a higher affinity for alpha over beta adrenoreceptor. Alpha adrenoceptors produce contraction, beta 2 receptors produce relaxation. Skeletal muscle and coronary circulation have more beta 2 than alpha 1 receptors.

Question 14

What is are the various stimuli of the RAAS that tell the kidney there is a problem with the CVS?

Answer 14

Low blood flow
Symp goes up
Low NaCl load (how much is filtered)

Question 15

Describe the RAAS from when renin is secreted.

Answer 15

Renin is released which breaks down angiotensinogen which is secreted from the liver to decapeptide (10 AA) ANG I which is cleaved in the lungs by endothelial bound ACE to ANG II (octapeptide). ANG II acts as a vasoconstrictor on SM which raises TPR and stimulates symp nerves to increase BP. ANG II also acts on adrenal glands to release aldosterone which stimulate epithelial cells in the distal tubule and collecting ducts of the kidneys to increase retention of renal NaCl and water which increases BV.

Question 16

Where is ADH released from?

Answer 16

The posterior pituitary gland which is controlled by neurones in the hypothalamus.

Question 17

What do neurones in the hypothalamus detect?

Answer 17

They are stimulated by an increase in osmolarity (dehydrated) or because you blood volume is reduced. These suggest yout CVS is compromised.

Question 18

What does ADH do?

Answer 18

Causes vasoconstriction at high concentration during haemorrhage or dehydration. More normally it causes anti-diuresis by allowing insertion of aquaporin H2O channels in the collecting duct which causes H2O reabsoption. This maintains blood volume and thus BP which is its main role.

Question 19

How is BP reduced with stretch receptors?

Answer 19

Arterial baroreceptors and left atrial receptors are stimulated by an increase in BP. They fire APs to the NTS which send out inhibitory nerves to the CVLM which stops ADH release.

Question 20

What do atria myocytes release when there is an increase in filling pressure?

Answer 20

Atrial Natriuretic Peptide

Question 21

What does ANP act on?

What does ANP do?

Answer 21

Atrial natriuretic peptide receptor (NP receptor)
Systemic vasodilatation, dilation of the renal afferent arteriole - increase GFR and increase Na+ and H2O excretion, decreases the release and actions of aldosterone, renin, ADH