Parasympathetic Nervous system Flashcards
What is the role of the parasympathetic systam?
Role in keeping body energy use low
- Lowers heart rate, blood presure and respiratory rates
- Gastronomical activity is high
Where do the cell bodies of the preganglionic neurones lie?
Either in the cranial or the sacral area of the CNS
What nerves come from the cranial region?
- Oculomotor (smooth muscles of the eye)
- Facial (facial glands)
- Glossopharyngeal (salivary glands)
- Vagus (Main organs in body)
What nerves come from the sacral region?
Nerves that affect:
- Large intestine
- Bladder
- Reproductive organs
What type of receptors are on the ganglion?
Nicotinic receptors
What type of receptors are on the effector cells?
Muscarinic cells
How is acetylcholine synthesised?
Acetyl CoA + Choline (with use of enzyme Choline Acetyltransferase (CAT)) = Acetylcholine
What makes a nicotinic receptor ionotropic?
It regulates the transport of charged ions
-2 ACh are needed to bind to receptor allowing the movement of charged ions to continue action potential
What makes a muscarinic receptor metabotropic?
G-protein coupled to second messenger alters K+/Ca+
-The protein winds in and out of the membrane 7 times, so when ACh is bound it changes shape and the secondary messenger is activated
What are the different types of muscarinic receptors?
M1: Neural/gut (increases gastric acid secretion)
M2: Cardiac (Lowers heart rate and force)
M3 Glandular (increases secretion)
What are the different types of parasympathetic drugs?
Parasympathomimetic (increase PNS effects) eg. Nicotine
Parasympatholytic (reduces PNS effects) eg. Atropine
Cholinesterase inhibitors (block enzyme that breakdowns ACh so ACh concentration increases PNS effects0
Ganglionic blocking drugs (blocks both PNS and SNS effects) eg. Nicotinic antagonists
How is parasympathetic control of the heart achieved? What receptors are in the heart?
Postganglionic vagal nerves release ACh which decreases heart function depending on binding point:
- SA Node (Decrease HR)
- Atrial muscle (decrease contractility)
- AV Node (decreased rate of conduction)
M2 muscarinic receptors
-Atropine can be used as a muscarinic antagonist to bind to M2 after cardiac arrest to promote cardiac function
How is parasympathetic control of the eye achieved?
Circular and ciliary muscle is stimulated due to ACh binding to M3 receptors.
Circular muscle contracts and reduces pupil diameter (MIOSIS)
Blocking of the receptors by Atropine will block contraction so pupil dilation (MYDRIASIS) will occur
Ciliary muscle contracts and moves in which relaxes suspensory ligaments. This causes the lense to become fatter so vision will be clearer at a shorter distance.
What is VIP? How does it help ACh?
Vasoactive Intestinal Polypeptide (VIP) - 28 amino acid peptide
During high stimulation, ACh and VIP are released which caused:
- Dilatation of the blood by VIP
- VIP to act as a neuromodulator to enhance effect of ACh on acinar cells
