Lecture 3.2: Cholinergic and Adrenergic Transmission Flashcards
What are the 2 Types of Cholinergic Receptors?
Muscarinic or Nicotinic
How many types of muscarinic receptor?
- 5 types of muscarinic receptor (M1-M5)
- M1,3,5 are GPCRs (Gq) mediated by inositol lipid
signalling - M2,4 act through Gi to open K+ channels
resulting in hyperpolarisation
M1 Receptors: Where are they found? Role?
- Essentially neural receptors, CNS, PNS parietal
cells - Mediate excitatory events by reducing K+
conductance resulting in hyperpolarisation
M2 Receptors: Where are they found? Role?
- Cardiac Cells
- Work by increasing K+ conductance
M3 Receptors: Where are they found? Role?
- Glandular and Smooth Muscle
- Mainly excitatory e.g. increasing secretions and
contraction of visceral smooth muscle - NB may also relax some vascular smooth muscle
via the production of nitric oxide
M4/M5 Receptors: Where are they found? Role?
- Located mainly in CNS
- Lack of clarity on role
What are the 3 Types of Nicotinic Receptors?
- Muscular (skeletal neuromuscular junction)
- Ganglionic (SANS and PANS)
- CNS (many are presynaptic and facilitate the release of
other transmitters)
SANS: Where do cell bodies of preganglionic neurones originate?
Originate in the intermediolateral cell column of the thoracic and lumbar spinal cord (T1- L2/3)
PANS: Where do cell bodies of preganglionic neurones originate?
Located in the brainstem and sacral segments of the spinal cord
PANS: Where do cell bodies of preganglionic neurones originate?
Where is the Enteric Nervous System (ENS) Located? (2)
- Submucosal Plexus (Meissners Plexus)
- Myenteric Plexus (Auerbachs Plexus)
What does the ANS do?
- Regulates physiological functions
- Where parasympathetic and sympathetic divisions
both innervate a tissue they often have opposite
effects
Where does the SANS outflow?
Thoraco-lumbar outflow
How do axons of the SANS leave the spinal cord?
Axons leave the spinal cord via the ventral root and initially enter the spinal nerve
What happens to SANS axons after they leave the spinal nerve? (3)
- Leave the nerve (via the white rami communicantes)
- Before synapsing with post-ganglionic neurons in
the paravertebral ganglia - Before renetring the spinal nerve (via grey rami
communicantes)
The sympathetic ganglia (…1… ganglia) form two …2… trunks of interconnected ganglia either side of the vertebral column
1) paravertebral
2) parallel
Preganglionic fibres to abdominal structures form the
…1… nerves which synapse in either the coeliac,
superior and inferior …2… ganglia
1) splanchnic
2) mesenteric
Innervation of the adrenal medulla: Preganglionic fibres in the splanchnic nerves synapse directly with …1… cells
1) chromaffin
Where does the PANS outflow?
Cranio-sacral outflow
Ganglia of PANS located close to or sometimes embedded in the…..?
organ they innervate
What is Acetylcholine (ACh) is Synthesised from?
- Choline and Acetyl-CoA
- Reaction is catalysed by choline acetyltransferase
Types of Cholinergic Receptors (2)
Nicotinic
Muscarinic
How many types of muscarinic receptors are there?
- 5 types of muscarinic receptor
- M1-M5
What muscarinic receptors are GPCRs (Gq
) mediated by inositol lipid signalling?
M1,3,5
M2,4 act through …1… to open K+ channels resulting in hyperpolarisation
1) Gi
What are M1 receptors?
- Essentially neural receptors
- CNS, PNS parietal cells
- Mediate excitatory events by reducing K+
conductance resulting in hyperpolarisation
What are M2 receptors?
- Cardiac
- Work by increasing K+ conductance
What are M3 receptors?
- Glandular and Smooth Muscle
- Mainly excitatory e.g. increasing secretions and
contraction of visceral smooth muscle - NB may also relax some vascular smooth muscle via
the production of nitric oxide
What are M4/5 receptors?
- Located mainly in CNS
- Lack of clarity on role
What are the 3 Main Types of Nicotinic Receptors?
- Muscular (skeletal neuromuscular junction)
- Ganglionic (SANS and PANS)
- CNS (many are presynaptic and facilitate the release
of other transmitters)
What is noradrenaline synthesised from?
Synthesised via dihydroxyphenylalanine (DOPA) and dopamine from tyrosine
What is noradrenaline inactivated by?
The enzymes MAO and COMT
What are the Classes of Adrenoceptors? (2)
α or β
What are the Classes of Adarenoreceptors based on?
Based on the rank order of potencies of
various catecholamines
Order of potencies of catecholamines in α-adrenoreceptors?
Noradrenaline>Adrenaline>Isoprenaline
Order of potencies of catecholamines in β-adrenoreceptors?
Isoprenaline>Adrenaline>Noradrenaline
How are α-adrenoreceptors catagorised?
- 2 subdivisions of α – α1 and α2
- Each of which has 3 subdivisions (1A, 1B, 1D and 2A,
2B and 2C)
How are β-adrenoreceptors catagorised?
3 subdivisions of β – β1, β2 and β3
