Function of ANS Flashcards
Signs of sympathetic NS in play?
Airways dilate
Heart beats faster
Heart beats stronger
Blood diverts to muscle
Gut motility decreases
Enzyme secretion in gut
generally inhibited
Stored energy is released
Pupils dilate
Eye focus far way
Hair stands on end
Mouth becomes dry
Signs parasympathetic NS is in play?
Airways constrict
Heart beats slower
Heart beats weaker
Blood diverts to gut
Gut motility increases
Enzyme secretion in gut
generally stimulated
Energy is stored
Pupils constrict
Eyes focus close up
Hair lies flat
Mouth starts drooling
What is important in determining if sympathetic or parasympathetic NS is put into play?
Depends on what neurotransmitter is released
And what receptor types it acts on
Acetylcholine released from sympathetic and paraysympathetic pre-ganglionic fibres and it then binds to cholinergic nicotinic receptors on post ganglion fibres
IN PARAsympathetic
post ganglionic fibres also release acetylcholine and this binds to muscarinic fibres on target organs/ tissue
In sympathetic
post ganglionic fibres release adrenaline and noradrenaline and that binds to adrenergic receptors which can be of alpha and beta type
Describe the eye when sympathetic or parasympathetic NS is in play (innervation)?
sympathetic:
Radial muscle contracts and makes pupil larger and because activates α1 receptors on radial muscle of the iris through some second messenger pathways- leads to increased intracellular calcium concentrations
parasympathetic:
Contracts sphincter muscle and makes pupil smaller because activation of Activates muscarinic receptors on sphincter muscle of the iris
What happens to lense of the eye during sympathetic and parasympathetic innervation?
SYMPATHETIC
During the fight or flight response the ciliary muscle (circular muscle that surrounds whole lens) relaxes and this increases tension on suspensory ligament -will stretch the lens and make it thinner. With a thin lens, the eye is going to focus further away
Happens when noradrenaline and adrenaline activate beta 2 receptors on ciliary muscle
PARASYMPATHETIC
muscarinic receptors on ciliary muscle cause it to contract, releases tension on suspensory ligament and allows lens to bulge up. And focuses eye closer up
Differences in sympathetic and parasympathetic innervation of heart?
SYMPATHETIC
Activates β1 receptors on the pacemaker cells
Increases heart rate
Activates β1 receptors on the myocytes
Increases strength of contraction
PARASYMPATHETIC
Activates muscarinic receptors on pacemaker cells
Decreases heart rate
Little effect on myocytes
Little effect on strength of contraction
Describe sympathetic and parasympathetic innervation of lungs?
SYMPATHETIC
Activates β2 receptors on smooth muscle of airways
Makes smooth muscle relax and dilates airways
PARASYMPATHETIC
Activates muscarinic receptors
Makes smooth muscle contract and constricts airways
How are subtypes of adrenergic receptors clinically relevant?
β2 agonist (e.g. salbutamol)
Dilates airways, limited effect on the heart
β1 antagonist (e.g. atenolol)
Decreases heart rate, limited effect on airways- for blood pressure
Describe sympathetic innervation of blood vessels?
Activates α1 receptors on smooth muscle of vessels
Makes smooth muscle contract and blood flow decreases
For blood vessels that are important in supplying body during fight or flight response:
Activates β2 receptors on smooth muscle of vessels
Makes smooth muscle relax and blood flow increases
Sympathetic and parasympathetic innervation of salivary glands?
SYMPATHETIC
Activates β receptors
Stimulates thick secretion rich in enzymes
PARASYMPATHETIC
Activates muscarinic receptors
Stimulates profuse watery secretion
Describe sympathetic and parasympathetic innervation of the bladder?
SYMPATHETIC
Activates β2 receptors on smooth muscle of bladder wall
Relaxes smooth muscle and reduces pressure
Activates α1 receptors on smooth muscle of sphincter
Contracts smooth muscle and stops urination
PARASYMPATHETIC
Activates muscarinic receptors on bladder wall
Contracts smooth muscle and increases pressure
Activates muscarinic receptors on sphincter
Relaxes smooth muscle and causes urination
Describe sympathetic and parasympathetic innervation of reproductive tract?
dual innervation with complimentary effects
SYMPATHETIC
Activates α1 receptors on smooth muscle of urethra
Contracts smooth muscle and causes ejaculation
PARASYMPATHETIC
Activates muscarinic receptors on smooth muscle of corpus cavernosum
Relaxes smooth muscle and causes erection
What controls all of this?
Autonomic reflexes
Can be spinal reflexes (e.g. urination in babies)
Can have higher control (learned reflexes)
Central control
Integrated in the brain, mainly hypothalamus, thalamus and brainstem
e.g. baroreceptor reflex
Baroreceptors detect changes in blood pressure
Integrating centre looks at the information
Coordinates a sympathetic and parasympathetic outflow to vary heart rate, strength of contraction, and constriction of blood vessels accordingly
