Lecture 14- Autonomic Nervous System Flashcards
auto
self
nomos
law
autonomic broadly means
self governing
what does the ANS doe
• Controls all involuntary functions e.g. heart rate, BP, GI motility, Iris diameter
ANS is sedated from
voluntary (somatic) nervous system
ANS is entirely
effectent
ANS is divided anatomically into
Sympathetic and Parasympathetic division
sympathetic division innervated
during stressful situations - fight or flight response
during the flight or flight response (sympathetic innervation) what happens to the body
- increased HR - increased force of contraction - increased BP
parasympathetic division regulates
basal activities
basal activities
e.g. basal heart rate Rest and digest
anatomical divisions of the brain stem and spinal cord
• Medullary • Cranial • Thoracic • Lumbar • Sacral
neurones in the parasympathetic NS
Long myelinated pre-ganglionic neurone
Short myelinated post-ganglionic neurone
with ganglia located within innervated tissue
neurones in sympathetic NS
Short preganglionic myelinated neurone and long unmyelinated post-ganglionic neurone
- ganglia located in paravertebral chain close to the spinal cord
origins of parasympathetic neurones
The parasympathetic division of the ANS originates (bilaterally) from the brainstem (medulla) and from sacral segments of the spinal cord.
origins of sympathetic neurones
in lateral horn of the lumbar and thoracic spinal cord
ganglia of sympathetic neruones
located in paravertebral chain close to the spinal cord
Neurotranmitters of the ANS
ACh and NA
pre-ganglionic neurones are all
cholinergic
- use ACh as their NT
Parasympathetic and sympathetic pre-ganglionic release of ACh results in
activation of post-ganglionic nicotinic ACh receptor
parasymapthetic post-ganglionic neuroen NT
also cholinergic
Parasympathetic post-ganglionic neurones release of Ach
Act on muscarinic ACh (mACh) receptors in the target effector tissue
GPCR (M1,M2, M3,M4,M5)
Sympathetic post-ganglionic neurones neurotransmitter
Most are Noradrenergic
noradrenaline interacts with
one of trwo major classes of adrenoreceptro:
- Alpha adrenoreceptors
- Beta adrenoreceptors
SOME SPECIALISED SYMPATHETIC POST-GANGLIONIC NEURONS THAT ARE CHOLINERGIC, NOT NORADRENERGIC e.g
Those innervating sweat glands and pilorection
how many mACh receptors
M1-M5
types of adrenorecpetor
other NT found in the ANS
Non-adrengeric non-cholinergic transmitters (NANCs)
NANCs
ATP
NO
5HT (serotonin)
Neuropeptides e.g. VIP, Substance P
These may be co-released with either NA or ACh
third division of the ANS??
The enteric nervous system
- Control the GI system, possessing 5 million neurons.
- Capable of operating independently of the CNS
the adrenal meduall (adrenal gland- which secretes adrenaline) is……. by the sympathetic nervous system
inebriated- sitmulated
preganglionic sympathetic innervation which controls the adrenal medulla
Sympathetic post ganglionic neurons in the adrenal glands are different:
They differentiate to form neurosecretory chromaffin cells
Chromaffin cells can be considered as postganglionic sympathetic neurons that
do not project to a target tissue
Instead on sympathetic stimulation these cells release adrenaline into the bloodstream
where are chromaffin cells found
adrenal meduall
chromaaffin cells innverated by
pre-ganglionic symapthetic neurones
(act as post-ganglionic neurones)
What are the physiological consequences of sympathetic stimulation of the heart (B1)?
- Tachy cardia (positive chronotropy)
- SA node
- Positive inotropy
- Ventricles
What are the physiological consequences of sympathetic stimulation of smooth muscle in blood vessels ( a1 and B2)?
Arterior contraction/ venous contraction
What are the physiological consequences of sympathetic stimulation of smooth muscle in Lungs, GI and GU tract ( B2)?
Bronchial/intestinal/uterine relaxation
What are the physiological consequences of sympathetic stimulation of smooth muscle in eye (a1)?
Radial muscle contraction
What are the physiological consequences of sympathetic stimulation of glands ?
increased secretion e.g. salivary
What are the physiological consequences of sympathetic stimulation ofthe kidney (a1)?
renin release
What are the physiological consequences of parasympathetic stimulation of heart (M2)?
Bradycardia- SAN node
Reduced cardiac conduction velocity – AV node
What are the physiological consequences of parasympathetic stimulation of smooth muscle (M3)?
- Bronchial contractions- lungs
- Increased intestinal mobility
- Bladder contraction (detrusor) and relaxation (sphincter)
- Penile erection- GU tract
- Ciliary muscle and iris sphincter contraction – eye
What are the physiological consequences of parasympathetic stimulation of glands (M3)?
Increased sweat/salivary/ lacrimal secretion
