Lecture 5 : The Autonomic Nervous System Flashcards
Tuesday 14th January 2025
Is the autonomic nervous system the involuntary system?
Yes, under unconscious control
What are the functions of the autonomic nervous system?
- Contraction/ relaxation of smooth muscle (heart)
- Exocrine and endocrine secretion
- Control of the heartbeat
- Steps in intermediary metabolism
Does the autonomic nervous system have an additional synapse to the somatic nervous system?
Yes
What are the 2 types of neurone found in the autonomic nervous system?
Preganglionic neuron (CNS → Autonomic Ganglion)
Postganglionic neuron (Ganglion → Effector organ)
Where does the additional synapse occur?
Occurs in an autonomic ganglion, where the preganglionic neuron synapses with the postganglionic neuron.
Is the autonomic ganglion a cluster of neuronal cell bodies?
Yes
What do neruones in an autonominc ganglion have?
Dendrites. However, those in a sensory ganglion are unipolar and so only have an axon
Is conduction in the autonomic nervous system a simple relay?
No, integration occurs
Do autonomic ganglion contain many postganglionic cell bodies?
Yes
Is the adrenal medulla a special case with the sympathetic nervous system, as there’s no post ganglionic neurone?
- Yes. Instead, the preganglionic neuron synapses directly on chromaffin cells in the adrenal medulla.
- Chromaffin cells function like postganglionic neurons but release hormones (mainly epinephrine) into the blood, not to a specific organ
- This allows for a fats and widespread ‘fight or flight’ response
What are the 2 branches of the autonomic nervous system?
Sympathetic and parasympathetic
What is the preganglionic transmitter in the sympathetic branch?
acetylcholine
What is the postganglionic transmitter in the sympathetic branch?
noradrenaline
What is a varicosity?
A varicosity is a swelling or bulge along the axon of a postganglionic neuron.
Unlike a traditional synapse, varicosities are spread out along the axon and release neurotransmitters over a wider area.
This allows for diffuse communication with smooth muscle, cardiac muscle, or glands — the typical autonomic targets.
Why is the use of varicosities by the autonomic nervous system important?
This setup is great for modulating large areas, like blood vessels or the gut wall, where precise point-to-point control isn’t necessary.
It also helps explain how autonomic control is slower and more widespread than somatic motor control (which uses neuromuscular junctions).
Where in the spinal cord is the pre ganglionic neurone of the synpathetic nervous system found?
In the lateral horn
Where in the spinal cord is the pre ganglionic neurone of the parasynpathetic nervous system found?
Brainstem
What is the function of the sympathetic nervous system?
Activates the body during stress (e.g., increases heart rate, dilates pupils, inhibits digestion).
What is the preganglionic transmitter in the parasympathetic nervous system?
acetylcholine
What is the postganglionic transmitter in the parasympathetic nervous system?
acetylcholine
What are the differences and similarities between receptors in the sympathetic and parasympathetic nervous system?
- Preganglionic neurones both release acetylcholine
-The first synapse (at the autonomic ganglion) uses nicotinic acetylcholine (ACh) receptors in both systems.
- They both have different post-ganglionic neurotransmitters. Sympathetic system: Releases noradrenaline (norepinephrine) at the target organ, which binds to α (alpha) and β (beta) adrenoceptors in the target organs (e.g., heart, lungs, muscles). Whilst Parasympathetic system: Releases acetylcholine (ACh) at the target organ, which binds to muscarinic ACh receptors.
What are some examples of channel-linked receptors (ionotropic)?
Nitotinic Ach receptor
What is an example of a G-protein coupled receptor? (metabotropic)
Muscarininc Ach receptor
