L17: Autonomic Nervous System Flashcards
1
Q
divisions of the autonomic nervous system (3)
A
PNS, SNS, ENS
2
Q
preganglionic vs ganglionic neurons
A
Preganglionic neurons: cell body in CNS
Ganglionic neurons: in periphery, cell bodies in peripheral ganglia, send out axons to target organs
3
Q
anatomy of SNS
A
- thoracic-lumbar region of spinal cord
- sympathetic ganglia are close to the spinal cord (sympathetic chain), short projection of preganglionic axon (for most but not all)
4
Q
activation of SNS
A
- Adrenal medulla directly innervated by preganglionic fibres → stimulation of chromaffin cells to secrete adrenaline into bloodstream
- Increased activity typically prepares the body for action
5
Q
action of SNS
A
- Increased activity typically prepares the body for action
- Eg. Increased blood pressure, increased heart rate, decreased GI activity, increased blood flow to lungs & muscles etc
6
Q
neurotransmitters of SNS
A
- ACh at preganglionic synapse, NE at postganglionic synapse
7
Q
anatomy of PNS
A
- cell bodies in brainstem and sacral region of spinal cord
- preganlionlic very long projections
- ganglions on or close to target organs
- short postganglionic neurons
- many axons carried in vagus nerve
8
Q
action of PNS
A
Activation balances & opposes actions of
sympathetic system (eg decreases heart rate,
increases activity of digestive tract, salivation)
9
Q
neurotransmitters and receptors of PNS
A
- ACh at both synapses
- preganglionic neurons release ACh onto nicotinic ACh receptors (nAChR) in peripheral ganglia and adrenal medulla
- Parasympathetic postganglionic neurons release ACh onto Muscarinic acetylcholine receptors (mAChR)
10
Q
nAChR - receptor type, activation and function
A
- ionotropic receptor
- chemically gated, opens when two ACh molecules bind
- permeable to both K+ and Na+
- opening → depolarisation bc Na+ come in
11
Q
mAChR - receptor type, activation and function
A
- G-protein coupled
- binding of ACh → receptor activation → activates intracellular signalling pathways
- activate pathways that produce different effects depending on cell type
12
Q
adrenergic receptors
A
- adrenaline and NE released from adrenal medulla
- bind to a or B receptors (both GPCRs)
- beta receptors
→ activation of AC → increased cAMP, activates PKA
- beta receptors
13
Q
ANS reflexes
A
- long reflexes → go via spinal cord/CNS
- stimulus activates sensory afferent neurons
- then to interneurons - can activate or inhibit
- then produces autonomic output (e.g. vasodilation)
14
Q
divisions of ENS
A
- Submucosal plexus – has sensory & motor neurons, innervates mucosal epithelium & muscle
- Myenteric plexus – includes sensory chemoreceptors & mechanoreceptors, and motor neurons, and drives GI smooth muscle
15
Q
actions of ENS
A
- generates GI activity patterns to propel and mix food
- regulates segretions of GI hormones
