autonomic nervous systems Flashcards
what components of the nervous system is part of the autonomic nervous system?
visceral efferent component
controls involuntary actions
no conscious though needed
what are controlled by visceral efferents in the ANS
smooth muscles
cardiac muscles
various glands
what are the 2 divisions on the ANS?
parasympathetic nervous system
sympathetic nervous system
where are the cell bodies for the sympathetic nervous system?
cell bodies of pre-ganglionic neurons in the thoracic and lumbar regions of spinal cord
T1-L2
core origin - body wide actions
where are the cell bodies for the parasympathetic nervous system?
cell bodies of pre-ganglionic neurons in the:
brain stem
CN 3, 7, 9 - head structures
CN 12 - thoracic and abdominal organs
Sacral Spinal cord
S2, 3, 4 - pelvic organs
top & tail origin - core action
organisation of sympathetic nervous system
pre and post ganglionic neurons are similar in length
synapse in sympathetic chain or one of the collateral (or pre-vertebral) ganglia or in adrenal medulla
nervous and endocrine component in SNS
- adrenal medulla part of SNS but secretes adrenaline hormone too
organisation of parasympathetic nervous system
long pre-ganglion neuron
short post-ganglionic neuron
ganglion is nearer effector organ
long pre as parasympathetic longer than sympathetic
sympathetic nervous system roles
more widespread action - often affecting whole body (endocrine link)
associated with homeostasis - blood pressure, thermoregulation
fight, flight or fright
- meeting demands of active muscles
- anxiety has more active flight/fright mechanism
can have more drastic effect than PNS
doesn’t try to preserve energy
parasympathetic nervous system roles
generally has discrete actions on single organs in the body ‘core’
e.g. salivary glands, heart
conservative anabolic effects - Rest & Digest
- storing energy (digestion)
- slowing heart
not a drastic change - often slow and steady
often maintains in a ready to go state
aims to save energy
4 example organs/systems that ANS effect
smooth muscle
heart
glands
metabolism
ANS HAS NO EFFECT ON BREATHING
- skeletal muscles controlled by somatic nerves e.g. phrenic innervates diaphragm
smooth muscles effected by ANS
blood vessels in various parts of the body
bronchi and bronchioles
influence of ANS on heart
rate and force of contraction of heart
GI Tract: circulation reduced to increase volume of blood to other organs and muscles
glads effected by ANS
salivary glands
gastro-intestinal glands
sweat glands
metabolism connection to ANS
parasympathetic NS - stores energy
sympathetic NS - makes energy available to organs
ANS effect on iris (radial and sphincter musclees)
parasympathetic - contraction
sympathetic - contraction
ANS effect on ciliary muscle
parasympathetic - contraction
sympathetic - relaxation
ANS effect on salivary glands
parasympathetic - copious, watery
sympathetic - viscous, low volume
both cause secretion but of different qualities
ANS effect on on lacrimal glands
parasympathetic - secretion
sympathetic - secretion
ANS effect on nasal glands
parasympathetic - secretion
ANS effect on blood vessels
parasympathetic - no direct effect; indirectly GIT receives more blood as more digestion
sympathetic: change in diameter of vessels and bronchioles
- constriction of alpha NA receptor
- dilation of beta NA receptor
parasympathetic ANS transmitters
Acetyl Choline (ACh)
both pre & post ganglion
sympathetic ANS transmitters
ACh pre-ganglion
Noradrenalin post-ganglion onto effector organ
Adrenaline from adrenal medulla
Noradrenaline ANS receptors
Alpha receptors
Beta receptors
why does noradrenaline have different effects on different organs?
due to 2 receptors for NA having different functions
effect of NA on alpha recpetors
vaso-constriction
contraction of smooth muscles in blood vessels
effect of NA on beta receptors
bronchodilation
relation of bronchiole smooth muscle
adrenaline ANS receptors
alpha 1 receptors
beta 1 receptor
beta 2 receptor
effect of adrenaline on alpha 1 receptors
contraction of smooth muscle
effect of adrenaline beta 2 receptors
relaxation of smooth muscle
effect of adrenaline on beta 1 receptors
increase heart rate and force of contraction
what are beta blockers?
block beta-1 adrenergic receptors only
so drug effects are restricted to heart cardiac muscles
(can interact with other receptors as not perfect)
lowers HR and force of contraction
dental use of adrenaline
usefully neurtransmitter/hormone
many local anaesthetics contain adrenaline as a vasoconstrictor (not all)
keep dose in recommended limits
- circulatory system will move injection from intended area
- vasoconstrictor needed sometimes to reduce clearance so longer treatment time
- reduced blood flow not ideal for treatment as source of immune cells
can have potential side effects in susceptible patients
e.g. those with heart conditions (work on other effectors)
what are the 2 types of cholinergic receptors?
muscarinic receptors
nicotinic receptors
distinguished by drugs, overall in areas and can give similar responses
muscarininc cholinergic receptors
5 subtypes
important in dentistry as affects salivary glands
post-ganglionic
neuro-effector junctions
blocked by atropine
- if blocked won’t respond to adrenaline
nicotinic cholinergic receptors
7 subtypes with different sub levels in each tissue too
pre-ganglionic and post-ganglionic neuron synapses
neuromuscular junctions
what organs do parasympathetic and sympathetic auntonomic nervous control?
many organs in head, thorax, abdomen, pelvis
parasympathetic more associated with body core
what organs receive sympathetic autonomic nervous control only?
blood vessels
glands in periphery e.g. skin, muscles
how is control achieve in organs receive sympathetic autonomic nerve signals only?
by varying amount of sympathetic activity
single control
what is the relationship between sympathetic and parasympathetic activity?
opposing effects usually
except genitalia (same effect here)
how are organs that receive Both parasympathetic and sympathetic autonomic nervous signals controlled?
dual control
- ‘balancing’ their activity
opposing effects working on same part
SA node dual control example
parasympathetic
- vagus nerve
- decreased HR
sympathetic
- increases HR
blood vessel single control example
blood vessels supplied by sympathetic nerves only
control of BV diameter is controlled by varying sympathetic activity
- ‘sympathetic tone’
small change in BV diameter has big change on BP
increased sympathetic activity on blood vessels
vasoconstriction
- higher BP
decreased sympathetic activity on blood vessels
vasodilation
- Lower BP
