Introduction to the ANS Flashcards
What are the autonomic target organs?
AUTONOMIC NS:
- Exocrine glands
- Smooth/muscle
- Cardiac muscle
- Metabolism
- Host defence
What are the two branches of the autonomic nervous system?
- Sympathetic (fight or flight)
- Parasympathetic (rest and digest)
Pupil when you enter a dark room
Sym Oculomotor nerve Q
Stomahc when youy smell food
Para Vagus
Heart when losing excessive fluid through sweating
Sym Lower HR = vagal (para)
High HR = Sym - Lose fluid = low blood presssure = low baroreceptor firing rate
What are the principal targets and functions of the autonomic NS?
Where on the diagram would noradrenaline be released from?
D and F
PARASYMPATHETIC:
- Cranial or sacral
- Long preganglionic fibre (usually projects down into the tissue itself)
- Short postganglionic fibre
- Both ACh
SYMPATHETIC:
- Thoracic or lumbar
- Short preganglionic fibre
- Long postganglionic
- Mostly pre=ACh, post=NA
- Exception 1: pre = ACh innervate adrenal medulla, post = A (80%) + NA(20%)
- Exception 2: pre and post = ACh (ACh drives secretion even though it is controlled by sympmathetic response)
TRUE OR FALSE:
PNS = coordinated response (very divergent)
FALSE
PNS = discrete/localised (little divergence 1:1 pre vs post)
SNS = coordinated response (very divergent, up to 1:20 pre vs post)
Enteric nervous system
Under PNS and SNS control but also local
Enteric = response without the brain Slide 22 [pic]
Somatic nervous system
ACh used to control skeletal muscle Slide 23 [pic]
Acetylcholine receptors
Muscarinic or nicotinic Slide 25 [pic]
Nicotinic receptors
Ion channel linked receptor Important for speed of affect At all autonomic ganglia Stimulated by nicotine/acetylocholine Slide 26 [pic]
Muscarinic
At all effector organs innervated by post ganglionic parasypathetic fibres Stimuated by muscarine/acetylocholine Type 2 - G-protein coupled Slide 27 [pic]
True or false: Nicotinic at effector organs
FALSE Nicotinic present throughout ANS at the postganglionic fibre NOTE: if a drug targets nicotinic receptors, the whole ANS will be affected
Which of the following effects would be observed after blockade of nicotinic acetylcholine receptors in an individual at rest? 1. Bronchoconstriction 2. Increased sweat production 3. Constipation 4. Increased urinary frequency 5. Short-sightedness
3 - constipation EXPLANATIONS: 1 - bronchodilation 2 - decreased sweat production (block = lose effect) 3 - para = stimulates muscle contraction. Therefore, blocking parasympathetic NS = constipation 4 - para = stimulates urine production. Therefore blocking para = decreased urinary freq 5 - para = allow near vision. Therefore block para = vision projects outwards
What effect would blockade of nicotinic acetylcholine receptors have on heart rate at rest and during exercise?
At rest = increase HR (suppress PNS) Exercise = less increase HR (less SNS innervation)
Sub-types of muscarinic cholinoceptors
M1 - neural (forebrain = learning and memory) M2 - cardiac (brain = inhibitory autoreceptors) M3 - exocrine and smooth muscle (hypothalamus = food intake) M4 - periphery = prejunctional nerve endings (inhibitory) M5 - striatal dopamine release NOTE: Year 2 , only need to know M123
Adrenoceptors
At all effector organs innervated by post ganglionic sympathetic fibres Stimulated by NA/A Type 2 - G-protein coupled Slide 34/35 [pic]
Important to consider for all drugs
- What is the drug target? (E.g. adrenoreceptors/muscarinic/nicotinic receptors) 2. Where is the drug target? 3. What is the end result of interaction? NOTE: with pharmacology, we usually think of ‘exogenous’ drugs, but can apply to ‘endogenous’ agents as well
Biosynthesis and metabolism of acetylcholine, noradrenaline and adrenaline
- Precursor enzymatically converted to neutrotransmitter 2. Packaged into vesicle 3. Ca2+ influx 4. Exocytosis 5. Neurotransmitter released into synapse 6. Receptor on postsynaptic membrane 7. Activated 8. Degraded
Biosynthesis and release and metabolism of ACh
Slide 42 [pic] If ACh happens to bounce and come into contadct with acetylocholine-esterase, it will degrade If ACh binds to receptor = response Eventually all ACh will be degraded
Biosynthesis, release and metabolism of noradrenaline
Slide 43 [pic] Need 3 different enzymes to liberate NA NA not metabolised in synapse - removed by transport proteins in both presynapse and postsynapse NA responses are quick
Blockade of which of the following targets would cause the most significant rise in synaptic noradrenaline concentrations? 1. Tyrosine hydroxylase 2. DOPA decarboxylase 3. Uptake 1 tranpsort protein 4. Noamine oxidase 5. Cathecol-O-methyl transferase
3 - uptake 1 transport protein Slide 43 [pic]
