Homeostasis & Autonomic Nervous System L1 Flashcards
define homeostasis
maintenance of stable internal environment
- Maintenance of equilibrium (through compensation)
- Maintenance of variables (e.g. blood pressure) within -
limited ranges
- involves integrated function of different organ systems
what is the result if homeostasis is not maintained
disease
what are the steps of homeostatic control
stimulus - sensor (monitoring) - controller (coordination) - effector (response) - effect
minimises disturbances
describe process of negative feedback
effector leads to reduction in stimulus
- blood pressure, plasma osmolarity, pupil diameter
how does the pupil respond to light
changes in diameter to adjust levels of light reaching retina
ganglia within retina detect light changes and send message to iris muscles via autonomic nervous system
what are the iris muscles that are involved in iris dilation
- the sphincter pupillae
- circular, constrictor, - dilator pupillae.
- radial, dilator,
what are the three control mechanisms
- nervous system
- endocrine system
- paracrine system
what is an important division of nervous system and what is it important for
autonomic nervous system
- important in maintaining homeostasis
what are the 3 main components of autonomic nervous system
- sensory afferent nerve fibres
- blood pressure via baroreceptors - control centres
- efferent pathways
what are the 3 control centres of ANS
- hypothalamus
- brain stem
- spinal cord
what are the 2 efferent pathways of the ANS
- parasympathetic
- brings processes back to normal rate - sympathetic
- prepares body for flight or fight
what do sympathetic and parasympathetic NS have in common
- both have 2 neurons in series
- the preganglionic neurone originating from CNS
- postganglionic neurone originating from autonomic ganglion
what feature of PSNS and SNS allows signal to be amplified
one preganglionic neurone can synapse with many post ganglion neurones
what are the distinct features of the PSNS
- long preganglionic neurone
- short postganglionic neurone
what is the origins of the preganglionic nerve in PSNS
- cranial nerve
- III: oculomotor (eye)
- VII: facial (lacrimal, nasal, submandibular)
- IX: glossopharyngeal (parotid)
- X: vagus (thorax and abdomen)- important - pelvic nerve
- rectum, bladder
what is the origins of the postganglionic nerve in PSNS
autonomic ganglia near or on target tissue
what are the distinct features of the SNS
- short preganglionic neurone
- long postganglionic neurone
- adrenal medulla
what is the origins of the preganglionic nerve in SNS
Thoracic 1 (T1) - Lumbar 2/3 (L2/3)
what is the origins of the postganglionic nerve in SNS
autonomic ganglia
2 Paravertebral sympathetic chains- chains that run down spinal cord
how is the adrenal medulla involved in SNS
Preganglionic neurones goes directly into it stimulating it to release adrenaline and noradrenaline into blood stream
what are the 4 types of neurotransmitters involved in ANS
- ACH
- noradrenaline
- adrenaline
- Non-Adrenergic, Non-Cholinergic (NANC) neurotransmitters
what are the two kinds of receptors involved in ANS
- Cholinergic
- Nicotinic or muscarinic - Adrenergic
- a or b
where are nicotinic cholinergic receptors used
they are on the autonomic ganglia between CNS and preganglionic neurone in both SNS and PSNS
which cholinergic receptor is used in the SNS and PSNS on autonomic ganglion
nicotinic
blocked by curare
what neurotransmitter binds to nicotinic cholinergic receptors in the SNS and PSNS
acetylcholine
what cholinergic receptor is used on target organs between postganglionic neurone and target organs
muscarinic
blocked by atropine
what neurotransmitter binds to muscarinic cholinergic receptors in the PSNS
(postganglionic neurone)
acetylcholine
what kind of receptor is muscarinic and what ion does it effect when it is active
G protein coupled receptor
causes K+ to leave target organ
what type of Adrenergic receptor is found in the SNS in postganglionic neurone
A- adrenoceptors
blocked by phentolamine
B-adrenoceptors
- blocked by propranolol
what are the types of A- adrenoceptors, where are they found, what neurotransmitter do they respond to and what is the effect
A1: postsynaptic, noradrenaline
- vasoconstriction and smooth muscle contraction
A2: presynaptic, noradrenaline
- Reduction in adrenergic and cholinergic transmission
what are the type types of B- adrenoceptors, where are they found, what neurotransmitter do they respond to and what is the effect
B1: heart, noradrenaline and adrenaline
-Increase in heart rate and force of contraction
B2: heart, adrenaline
- Vasodilation and smooth muscle relaxation
