ANS control on vasculature

Question 1

Describe the post and pre ganglionic nerve fibres in para and sympathetic NS, as well as the Neurotransmitters released

Answer 1

Parasympathetic:
• Long pre-ganglionic fibre.
• Ganglion is closer to the organ to be innervated
• Neurotransmitter: Acetyl Choline in both neurons

Sympathetic:
• Short preganglionic fibre
• Ganglion is far from organ to be innervated
• Neurotransmitter:
- 1st neuron = ACh (on Nicotinic receptor)
- 2nd neuron = Noradrenaline

Question 2

what are the receptors in para and Symp NS

Answer 2

In parasympathetic:
nicotinic for the first nerve fibre and muscarinic for the second

Sympathetic:
Nicotinic for ACh
Alpha and beta adrenergic receptors for noradrenaline (mostly ALPHA)

Question 3

Do all post ganglionic Symp fibres release Noradrenaline?

Answer 3

No. Adrenal medulla has chromatin cells which release adrenaline (hormone)
and Sweat glands are applied with ACh

Question 4

Explain the mechanism to maintain blood pressure?

Answer 4

• Blood exits heart through aortic arch.
• There are nerve receptors (baroreceptors = mechanoreceptors) in the aortic arch and carotid sinus which detect changes in blood pressure.
• If the blood pressure increases (high cardiac output), the arterial walls stretch, and this is detected by the baroreceptors.
• A signal is sent out to the brain via the Vagus nerve from the aorta and via the Glossopharyngeal nerve from the carotid artery, to tell it that blood pressure is too high.

Response: to lower blood pressure
• Brain inhibits the sympathetic activity to lower the vasoconstriction and relax the vessels
• Alternatively, could increase the parasympathetic activity by releasing Acetyl Choline to dilate blood vessels.

Question 5

what are 3 neurotransmitters involved in the Sympathetic NS (I think they just effect vasculature???)

Answer 5

o Noradrenaline – acts mainly on alpha receptors
o ATP – acts on P2X receptor (ion channel) so ATP response is very fast
o Neuropeptide Y (NPY) – acts on Y receptor (quite slow)

Question 6

What is a varicosity?

Answer 6

Varicosity = swelling at the end of nerve fibres which holds neurotransmitters.

Question 7

Where are small molecule NTs and neuropeptide synthesised?

Answer 7

• Small molecule neurotransmitters e.g. ACh (synthesised at varicosity)
• Neuropeptides (synthesised in cell body)

Question 8

What is PVAt and why is perivascular adipose tissue (PVAT) important?

Answer 8

PVAt is a local deposit of adipose tissue surrounding the vasculature.

Fat is connected to blood vessel by the
nerves, so stripping it damages the nerves.

Fat cells around blood vessels have been identified to release many different adipokines – these have a role in vascular modulation.