Autonomic NS Flashcards
What does autonomous mean?
Self-governing –> subconscious control
e.g. HR, pupil diameter, blood vessel contractility, hormonal secretions
Why is the autonomic NS important?
It maintains homeostasis
What part of the NS is the autonomic NS?
It’s is part of the peripheral NS
In the AFFERENT division - carries instruction to CNS
What does the somatic nervous system do?
Conscious control of skeletal muscles
What does the autonomic nervous system do?
Unconscious control of cardiac, smooth muscle & glands
What are the two divisions of the ANS?
Parasympathetic & sympathetic
What are the roles of the parasympathetic and the sympathetic NS?
This division is anatomical
Based on the CNS location of cell body of preganglionic nerve
What are the two divisions of the peripheral NS?
- Somatic
- Autonomic
Insert somatic and autonomic comparison image here
…
What is the structure of the autonomic NS?
It is a two neurone chain
- The preganglionic (first) neurone - extends to the ganglion
- The postganglionic (second) neurone extends from the ganglion to effector organ
What are ganglia?
Cell bodies of many peripheral autonomic neurones occur in clusters & form swelling on nerve trunks
What is at the end of the postganglionic neurone?
Many varicosities from which NTs are released
What are preganglionic neurones?
Axons that form synapses with ganglion cells
(Preganglionic autonomic fibres)
What are postganglionic neurones?
Axons innervating effector cells
(Postganglionic autonomic fibres)
What are the preganglionic nerves in the ANS?
Acetylcholine (ACh)
What are the postganglionic nerves in the ANS?
Acetylcholine (ACh)
Noradrenaline (NA)
What are the pre- and postganglionic nerves in the ANS?
Non-adrenergic non-cholinergic neurotransmission (NANC)
What does the ANS do overall?
Conveys all outputs from the CNS to the rest of the body except motor innervation of skeletal muscle
What does the ANS do in homeostasis?
It regulates most non-voluntary processes in homeostasis
What are some of the non-voluntary processes in homeostasis that the ANS regulates?
- Heartbeat
- Contraction of smooth muscle of various organs & blood vessels
- Exocrine (& some endocrine) secretions
- Energy metabolism (e.g. liver & skeletal muscle)
How do the sympathetic and parasympathetic interact?
They function separately
Have opposing effects in some states (e.g. HR, GI tract) –> but not in some others (e.g. salivary gland secretion)
Give some examples of what the sympathetic NS does
- Pupils dilated
- Hair erected
- Inc blood sugar
- Inc HR
- Inc blood flow through muscle
- Blood diverted from GI tract
When does sympathetic activity increase?
During stress
When does Parasympathetic activity mostly happen?
It predominates during satiation & repose: “rest & digest”
What is the ANS influenced by?
Sensory info via control centres in the brain
Where does cranial sacral outflow happen?
The parasympathetic NS
How does cranial sacral outflow work?
- Preganglionic axons emerge from cranial & sacral regions of CNS
- Preganglionic axons form synapses in ganglia near to/adjacent to/within effector tissues
What are sacral nerves?
Form pelvic plexuses containing scattered ganglia & also some ganglia within tissue - these are pelvic & abdominal viscera
What do parasympathetic ganglia look like?
Preganglionic fibres are short and post are long
What are the 3 ways that the preganglionic sympathetic axons enter sympathetic chains?
- Paraverbal sympathetic chains
- Prevertebral ganglia
- Adrenal medulla
