Autonomic Nervous System Flashcards
What are the four functions of the autonomic nervous system?
1) To gather information from the internal physiology and the external environment
2) To integrate information for assessment and meaning
3) To effect a motor response
4) To regulate homeostasis for optimal performance
What length are the neurones in parasympathetic?
Long preganglionic, short postganglionic
What lengths are the neurones in the sympathetic nervous system?
Short preganglionic and long postganglionic
What are the target tissues of the sympathetic and parasympathetic nervous systems?
Smooth muscle, cardiac muscle, exocrine glands and brown fat
Action of the parasympathetic nervous system…
stimulates flow of saliva, exocrine glands and peristalsis
Stimulates secretion and release of bile
Contracts bladder
Constricts bronchi
Slows heartbeat
Action of the sympathetic nervous system…
Dilates pupil, inhibits bladder contraction, secretion of noradrenalin and adrenaline, conversion of glycogen to glucose, suppresses peristalsis and secretion. Increases heart rate.
What are the differences between the SNS and PSNS?
PSNS - Acetylcholine released by pre and postganglionic terminals.
SNS - Acetylcholine only released at preganglionic nerve terminal.
PSNS - has muscarinic receptors
SNS - has adrenergic receptors
How is acetylcholine synthesised and broken down?
Choline + Acetyl Coenzyme A >>>>>> Choline Acetyltransferase <<<<< Acetylcholine >>>>>> Acetylcholinesterase <<<<<< Choline + Acetate ......................................................................................
Also, Coenzyme A acts on acetylcholine to create more acetyl coenzyme A
Single or low frequency preganglionic firing leads to…
Release of acetylcholine which activates nicotinic receptors, triggering fast excitatory postsynaptic potentials in the postganglionic neurone.
High frequency stimulation of postganglionic parasympathetic neurone leads to…
More acetylcholine release and release of luteinising hormones-releasing peptide. The complex postganglionic response consists of a fast EPSP, slow IPSP mediated by muscarinic receptor activation of GIRKs and delayed EPSP resulting from LHRH binding to peptidergic receptors.
How does parasympathetic release of acetylcholine reduce cardiac output?
Muscarinic generation of Gbg directly activates potassium channel (GIRKs) in the pacemaker cardiocytes. this leads to them slowing their depolarisation and therefore heart rate.
Muscarinic generation of Galphai in the heart muscle decreases generation of cAMP and PKA levels leading to reduced opening of L-type calcium channels, therefore reducing the force of heart contraction.
How does sympathetic release of norepinephrine/noradrenaline increase cardiac output?
Beta1 adrenergic receptors signal via GalphaS in pacemaker cardiocytes which elevates cAMP and PKA levels, reducing the threshold voltage for action potential initiation. This therefore increases heart rate.
Beta1 adrenergic elevation of cAMP and PKA in heart muscle increases opening of calcium L-type channels therefore increasing the force of heart contraction.
Chronic alcohol use can cause what to happen to neurone?
Demyelination
Alcohol primarily effects which branch of the autonomic nervous system?
The sympathetic - increases activity
Latrotoxin has what effect on ACh?
Increases release leading to pain, cramps, sweating and fast pulse.
