Lecture 12 : Functioning of the Autonomic Nervous System Flashcards
(12 cards)
Main autonomic sensory components
Difference between Somatic and Autonomic Motor Neurones
Somatic motor neurons:
- Control skeletal muscles (voluntary movement).
- Have a single, heavily myelinated axon directly to the muscle.
- Always excitatory.
Autonomic motor neurons:
- Control smooth muscle, cardiac muscle, and glands (involuntary).
- Use a two-neuron chain (preganglionic and postganglionic neurons).
- Can be excitatory or inhibitory.
Some differences between autonomic and somatic system
Neurotransmitters for Somatic, Autonomic and Enteric nervous system
Sweat glands important exception, innervated from neurones at embryonic development. You’d expect noradrenaline, but there’s ACh post ganglion instead.
Quick adrenaline thing
Acts on non-innervated receptors (makes sense), like smooth muscle or blood vessels.
Secreted by adrenal medulla.
Sympathetic Nervous System SNS vs Parasympathetic Nervous System PNS
Dual innervation / antagonstic effects
Pupils however display this effect via different muscles.
SNS -> Contraction of radial muscle -> Pupil dilates
PNS -> Contracrtion of circular muscle -> Pupil Constricts
There is single innervation too
Sweat glands (SNS only)
Most blood vessels, (smooth muscle is SNS only)
Sometimes there are dual innervation systems that are NOT antagonistic…
Exocrine glands, eg. Salivary
Weird thing about blood vessel diameter regulation
SNS can cause vasoconstriction and vasodilation in different parts of the body that require whichever one. Eg. when running, vasodilation in skeletal muscle and cardiac muscle, and vasoconstriction in gut.
In male sex organs
PNS = Erection
SNS = Ejaculation
Point, erection (PNS)
Shoot, ejaculation, (SNS)
Some examples of interactions of autonomic and somatic systems
