Overview of the Autonomic Nervous System Flashcards
What is the ANS?
what is autonomic?
what are the 3 divisions? what do they control?
Autonomic : Provides ‘involuntary’ information from CNS to peripheral organs
e.g. increasing heart rate during exercise
Contains 3 divisions
SYMPATHETIC and PARASYMPATHETIC nervous systems linking central nervous system (CNS) to peripheral organs e.g. heart, lungs, glands
ENTERIC nervous system controlling GI tract (Not now, see Semester 2)
Clinical Relevance of ANS?
important to understand what 2 things?
Important for understanding body functions
Important regulation of many diverse systems & organs
e.g. cardiovascular system, respiratory system, alimentary system, urinal-genital system, vision
Important for understanding pharmacological treatment
Simple introduction to pharmacological basis
of treating disease therapeutics
Rational for drug treatment of diseases
Many common diseases involve the ANS and are treated by drugs that act on the ANS
e.g. Hypertension, heart failure, asthma, IBS, glaucoma
Why is the ANS so Important?
heart - san? avn? cardiac myocytes?
smooth muscle - what does ans do?
gland cells - ans function?
ANS innervates many different cell types
and controls many important functions
Heart
Sino-atrial node cells – Regulates heart rate
Atrial-ventricular node cells – Regulates electrical conduction through heart
Cardiac myocytes – Regulates contractility of heart
Smooth muscle
ANS contracts or relaxes smooth muscle cells
which are present in in many tissues/organs
e.g. blood vessels, airways, intestine, bladder
Gland cells
ANS cause secretions from glandular cells
e.g. release of saliva, sweat, gastric acid,
insulin, glucagon
Overview of Anatomy
what is ANS anatomy wise?
how is it different to somatic neruones?
what can be regulated by drugs or other areas of CNS?
ANS – Two efferent (away from) neurones arranged in series conducting electrical activity from CNS to peripheral tissue/organ
Different to somatic motor nerves – where a single efferent neurone connects CNS to skeletal muscle
Pregaglionic nerve can be controlled by other areas of CNS therefore can be regulated
Parasympathetic anatomy
where no preganglionic fibres? which cranial nerves? length? which receptors at pre and post? neuro transmitters at pre and post?
No preganglionic fribre in thoracic or lumbar regions
cranial nerves 3, 7, 9, 10
Long pre-ganglion and short post-ganglion fibre
Ach - nicotinic pre-ganglionic synapse
ach - muscarinic post-ganglionic synapse
sympathetic anatomy
where preganglionic fibres?
length?
which receptors at pre and post?
neuro transmitters at pre and post?
pre ganglion fibre from thoracic and lumbar region
short pre-ganglion and long post-ganglion fibre
hence post ganglion will go to organ
ach - nicotinic pre-ganglionic synapse
Na - a/B receptors post-ganglionic synapse
Overview of Chemical Transmission
where do the autonomic nerves communicate? (2)
essential steps in synaptic transmission (7)
Autonomic nerves communicate at synapses
Between autonomic nerves - at ganglia AND
Between autonomic nerves and peripheral organs – at post-ganglionic junctions
Synapses use chemical transmission for communication
Essential steps in chemical transmission :
Synthesis of neurotransmitter
Storage of NT in vesicles (hence won’t break down)
Arrival of AP at synaptic terminal
Terminal depolarises, activation of voltage-gated Ca2+ channels, Ca2+ influx
Ca2+-dependent release of NT
NT binds to receptor induces response
Uptake/breakdown of NT
Overview of Chemical Transmission in ANS
neurotransmitters?
what do all preganglionic fibres release? act where?
postganglionic parasympathetic nerves release? act where?
what is the exception?
postganglionicsympathetic nerves release? act where?
what is the exception?
stimulation of preganglionic fibres release what from adenal glands? (2) post ganglionic?
Neurotransmitters - Acetylcholine (Ach) and Noradrenaline (NA)
All pre-ganglionic sympathetic/parasympathetic nerves release Ach. Ach acts at nicotinic receptors (Nic) at ALL autonomic ganglia
Post-ganglionic parasympathetic nerves release Ach which acts at muscarinic receptors (Mus)
Exception - non-adrenergic-non-cholinergic (NANC) nerves which use other chemicals such as nitric oxide (penis)
Post-ganglionic sympathetic nerve release NA
which acts at a or B adrenoceptors
Exception – In sweat glands, sympathetic nerves release Ach which acts at muscarinic receptors (Mus)
Stimulation of pre-ganglionic sympathetic fibres release
adrenaline (80%) and noradrenaline (20%) from adrenal glands. NO post-ganglionic fibres are involved in innervation of adrenal glands
Functions of Sympathetic and Parasympathetic
Nervous Systems
2 functions?
The ANS is composed of two separate branches
SYMPATHETIC NERVOUS SYSTEM
“Fear, fight and flight”
PARASYMPATHETIC NERVOUS SYSTEM
“Rest and digest”
General Rules of about Functions of
Sympathetic and Parasympathetic Nervous Systrems
what do they innervate?
Effect on heart? intestine? iris? hence?
effect on salivary gland? hence?
effect on sweat glands? blood vessels? kidney? hence?
effect on pancreas, secretory cells of stomach, lungs? hence?
what is special about lungs?
Sympathetic and Parasympathetic innervate same organ to produce opposite effects
e.g. Heart - sym increase / parasym decrease = heart rate and force of contraction
Intestine- sym decrease / parasym increase motility
Iris - sym dilates / parasym constricts pupil
Sympathetic and Parasympathetic innervate same organ
to produce the same effect
e.g. both increase secretions from salivary gland
Some organs are only innervated by Sympathetic
e.g. sweat glands, kidney, blood vessels
Some organs are only innervated by Parasympathetic
e.g. pancreas, secretory cells of stomach, lungs
(but airways contain β-adrenoceptors, modulated by circulating adrenaline -> sympathetic release this)
ANS Contains both Afferents and Efferent fibres
Responses to a decrease in blood pressure (e.g. Standing up)?
ANS is of primary importance in mediating homeostatic involuntary mechanisms – achieved through feedback systems
Example: Responses to a decrease in blood pressure (e.g. Standing up)
Drop in blood pressure
↓
Change in baroreceptor activity (stretch receptors in aortic arch)
↓
Change in firing of sensory afferent fibres to CNS
↓
Sensory information processed by CNS
↓
Signals are sent out via sympathetic nerves (efferent fibres) to the heart, blood vessels, kidney to increase in blood pressure
