Autonomic Physiology %% MW (+ Flashcards
What is the difference between autonomic and somatic nervous system?
These differ anatomically in terms of how the afferent neuron gets to the target.
Somatic vs autonomic pic
What happens at the junction?
- Ionotropic receptors form an ion channel pore.
- In contrast,metabotropic receptors are indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms, often G proteins.
- Hence, G protein-coupled receptors are inherently metabotropic.
Name the 3 divisions of the autonomic (involuntary) nervous system?
- Sympathetic division (fight or flight)
- Parasympathetic division( Rest and digest)
- Enteric nervous system (gastrointestinal tract)
Overall picture (comparision) of sympathetic vs parasympathetic?
Blue is sympathetic. Red para.
Note: both have unmyelinated post, and small myelination in pre
Sympathetic
- Short pre, Long post ganglionic fibres
- Thoraco-lumbar
- Pre releases Ach ⇒ Nicotinic
- Post releases NA ⇒ a or b
Parasympathetic
- Long pre, short post ganglionic fibres
- Cranio-sacral
- Pre releases Ach ⇒ Nicotinic
- Post releases Ach ⇒ Muscarinic
Convergence and divergence lead to “mass activation”, which division of the autonomic nervous system does it occur?
- Sympathetic
- In parasympathetic, you get independent effects
The eye
Sympathetic system:
- b2 receptors= ciliary muscle relaxes & eye focuses far away
- a<strong>1</strong> receptors= radial muscle contracts & makes pupil larger
Parasympathetic system:
- Muscarinic receptors=ciliary muscle contracts & eye focuses close up
- Muscarinic receptors = spincter contracts and makes pupil smaller
The eye muscles
- Cilliary, relaxed ⇒ far, contracted ⇒ near
- Sphincter, relaxed ⇒ larger pupil, contracted ⇒ small pupil
- Radial, relaxed ⇒pupil smaller, contracted ⇒ pupil larger
The heart
Sympathetic system
- B1 receptors=pacemaker cells , increases heart rate
- B<strong>1</strong> receptors= myocytes (muscle cells) Increases strength of contraction
Parasympathetic system
- Muscarinic receptors= pacemaker, decreases heart rate
The lungs
Sympathetic system:
- B<strong>2</strong> receptors: smooth muscle relax & dilates airways
Parasympathetic system:
- Muscarinic receptors: smooth muscle contract & constricts airways
Therapeutic
–B2 agonist (eg salbutamol) dilates airways, but does not affect the heart
–B1 antagonist (eg atenolol) decreases heart rate, but does not affect airways
Blood vessels
Sympathetic system :
- a1 receptors= contract & blood flow decreases
- b2 receptors= relax & blood flow increases
Parasympathetic system:
- No effect
The gut
Sympathetic system:
- a/b receptors on gut smooth muscles, decreases gut motility
- a receptors in pancreas= Inhibits secretion of enzymes
Parasympathetic system:
- Muscarinic receptors in pancreas= Increases gut motility
- Muscarinic receptors in pancreas =Increases secretion
Salivary glands
Sympathetic system
- b receptors =stimulates thick secretion rich in enzymes.
Parasympathetic system
- Muscarinic receptors= stimulates profuse watery secretion
The bladder
Sympathetic system
- b2 receptor = relaxes smooth muscle and reduces pressure
- a1 receptors = contracts smooth muscle and stops urination
Parasympathetic system
- Muscarinic receptors= contracts smooth muscle and increases pressure
- Muscarinic receptors= relaxes smooth muscle and causes urination
Reproductive tract
Sympathetic system
- Activates a1 receptors on smooth muscle of urethra , Contracts smooth muscle and causes ejaculation
Parasympathetic system
- Activates muscarinic receptors on smooth muscle of corpus cavernosum, Relaxes smooth muscle & causes erection
Neurotransmitter pics
