Autonomic Nervous System 2 Flashcards
What do Presynaptic Autoreceptors do in the Parasympathetic System?
They mediate Negative Feeback Inhibition.
This limits the amount of ACh produced
What does a Beta 1 and a Gs protein receptor stimulate in the Sympathetic Nervous System?
Causes Stimulation of Adeylycyclcase
Increases the rate and the force of the Heart
What do Presynaptic Autoreceptors do in the Sympathetic System?
Act as a part of the Negative Feedback system
Detects the amount of NA in the synaptic cleft
If too much, limits the amount of Ca2+ entering the pre-ganglionic cell
Therefore limits the amount of NA being exocytosed into the synaptic celft
What effect does cocaine have on the Autonomic Nervous System?
Cocaine blocks the U1 uptake system.
This causes NA to accumulate in the synaptic cleft
What are Nicotinic Acetylcholine Receptors made of?
Consists of five glycoprotein subunits
- There are many variations
What are the proteins that are used to assemble a Nicotinic Receptor?
Alpha 1 to Alpha 10 Beta 1 to Beta 4 Gamma Sigma Epsilon
In a ganglionic Nicotinic Receptor were are the binding sites?
They are found between the Beta and Alpha subunits
- There are two binding sites for the ligand.
What are the ions that enter and leave the Nicotinic Receptors?
Na+
K+
Ca 2+
What ion/ions move into the cell?
Sodium
Calcium
What ion/ions move out of the cell?
Potassium
Describe Cholinergic Transmission.
- Choline taken up via the transporter
- Choline and Acetate Co A synthesised to Acetyl Choline (ACh)
- ACh is stored in vesicles
- Depolarisation by action potential causes opening of voltage activated Calcium channels.
- Calcium induces the ACh to exocytose
- ACh binds to Nicotinic and Muscarinic Receptors activating them
- ACh broken down by acetylcholinesterase
- Choline taken back up
What is ACh synthesised from?
Acetyl-Co A
Choline
What is the ion that causes ACh vesicles exocytosis into the synaptic cleft in Cholinergic Transmission?
Calcium
What is the enzyme that breaks ACh down, after activating the receptors on the post-synaptic cell?
acetylcholinesterase (AChE) – terminates transmission
Describe cholinergic transmission at the ganglia
- ACh exocytoses from pre-ganglionic terminals
- ACh binds to the receptors causing the
nicotinic ACh receptors to open - Na+ then flows into the Post-ganglionic
dendritic body - This creates a small graded depolarisation (it
is also called an excitatory post synaptic
potential) - amplitude of this response is
variable - depends on amount of ACh - E.P.S if big enough allow voltage activated
ion channels to open - This creates a small current that flows to Voltage activated Na+ channels
- The Na+ channels open allowing more sodium to enter
- This produces an Action Potential
What drug can act in the same manner as ACh?
Nicotine
In ganglia transmission what drug can selective block the receptors?
Hexamethonium
How does hexamethonium block the receptor?
Open channel block
What type of anatagonism is an open channel block?
Non-competitive antagonism