Cholinergic Mechanisms Flashcards
What does the peripheral nervous system split into? Name their functions
Somatic - Skeletal Muscle
Enteric - Control GIT function
Autonomic - Visceral Organs
What are the different response types? What are their purpose?
Parasympathetic - “Rest and Digest”
Sympathetic - “Flight or Fight”
What is the function of the ANS during pregnancy?
Adapt the body to nurture the foetus
Adapt the maternal blood volume and cardiac output to match foetal requirements
What is foetal heart rate regulated by?
The ANS, where parasympathetic (vagal) activity is dominant
What is the purpose of the vagal activity in the foetus?
Slow down heart rate and stabilise at 120-160BPM
What aortic arch receptors are there and what do they do to regulate FHR?
Chemoreceptors - sensitive to low O2, increase vagal activity during hypoxia, reduce HR
Baroreceptors - Sensitive to changes in arterial pressure
- Inc pressure = inc vagal activity = rd HR
- rd pressure = rd sympathetic activity = inc HR
When does foetal ANS regulation begin? What is the significance?
Starts in the third trimester and continues to first year.
Ensures the infant can breathe, eat, homeostasis
Describe Cholinergic?
A neuron or axon that is capable of releasing acetylcholine (ACh) when a nerve impulse passes
What does the cholinergic system include?
- Whole PNS
- Pre ganglionic neurones of SNS
- Post ganglionic neurons of SNS
- Somatic motor neurons
- CNS
At autonomic levels, what do cholinergic neurotransmissions control?
- Smooth muscle activity
- Exocrine and endocrine secretions
- Heart rate and cardiac output
- Metabolic processes
At somatic motor neurons what does ACh do?
Trigger contraction of skeletal muscle fibres.
At the CNS what does cholinergic neurotransmission regulate?
- Plasticity
- Arousal
- Reward
Name the stages of cholingeric neurotransmission
- Re-uptake of choline
- Transport of ACh into vesicles
- Exocytosis of ACh
- Interactions between ACh and receptors
- Termination of ACh effects
WRT the stages of cholinergic neurotransmission, how is choline taken up?
Choline transferase brings choline in
Acetyle-coenzyme A (AcCoA) binds to choline to make ACh
Catalysed by Choline acetyltransferase
WRT the stages of cholinergic neurotransmission, how is ACh transported into vesicles? What other substances are there?
Transporter protein vesicular acetylcholine transporter (VAT)
Other chemicals include ATP and P
WRT the stages of cholinergic neurotransmission, how is exocytosis mediated?
By vesicle-associated membrane protein (VAMP)
WRT the stages of cholinergic neurotransmission, how does ACh interact with the receptors?
Diffusion
WRT the stages of cholinergic neurotransmission, how is the effect of ACh terminated? Why is this done?
Acetylecholinesterase (Membrane bound) breaks ACh into choline and acetate.
This prevents desensitisation of the organ and allows choline to be reused
What methods can be used to target cholinergic neurotransmission? Name 5.
- Inhibition of reuptake
- Blockage of vesicular ACh transport (VAT)
- Inhibition of exocytosis of ACh vesicles
- Receptor agonist/antagonist
- Acetylecholinesterase inhibitors
What is Acetylcholine?
Endogenous muscarinic and nicotinic receptor agonist
Why is ACh not clinically useful?
- Quickly hydrolysed
2. Not selective for receptor sub-types
What types of muscarinic receptors are there? Where they found?
M1 - CNS, GIT glands
M2 - Heart and smooth muscle
M3 - Smooth muscle and secretory glands
M4 - Nerve cells
What are the sub types of nicotinic receptors?
Nm - Neuromuscular junctions
Nn - Autonomic ganglia, adrenal medulla and CNS