where does the cell body of preganglionic neuron lie generally?
in the brain or spinal cord
where do axons of the preganglionic neuron go?
through white ramps to get to sympathetic ganglia where it synapses with a postganglionic neurone
what is another name for preganglionic neuron?
visceral motor neuron
what are sympathetic ganglia?
sites of synapses between pre and post ganglionic neurons
where does the sympathetic trunk ganglia lie?
either side of the vertebral column
what makes up the sympathetic chain?
sympathetic ganglia and sympathetic trunk
where does the postganglionic neutron lie?
outside the CNS in the PNS
where does the cell body of a postganglionic neuron lie?
in autonomic ganglia
where do postganglionic axons terminate?
visceral effectors (mainly to smooth muscle surrounding blood vessels)
where do the cell bodies of preganglionic neurons in the thoracolumbar division lie?
the lateral horns of the grey matter
which vertebral segments make up the thoracolumbar division?
12 thoracic segments
first 2 lumbar segments
what is the thoracolumbar outflow?
axons of the preganglionic neurons of the thoracolumbar division
name the three cervical ganglia
superior, middle and inferior cervical ganglia
what does the superior cervical ganglia innervate and what action does this bring around?
innervates iris of the eye, skin of face and salivary gland
causes pupil dilation, blushing and reduction of saliva
what are the cervical ganglia attached to?
thoracic chain below
what does the cardiac plexus do?
provides sympathetic innervation of the heart
plexus forms around the aorta and atria
what nerves make up the cardiac plexus?
branches of the upper thoracic chain
what does the pulmonary plexus do?
sympathetic innervation of the lungs
plexus forms around the large pulmonary arteries
what neurotransmitter do preganglionic neurons release and what effect does it have?
acetylcholine
activates postganglionic
what type of receptors are on autonomic ganglia?
cholinergic nicotinic types
what neurotransmitter do postganglionic neurons release and what effect does it have?
noradrenaline
makes arterial smooth muscle contract
what receptors on smooth muscle does noradrenaline act on?
alpha-1 adrenoreceptors
what additions to the sympathetic chain are there below the diaphragm?
prevertebral ganglia
what makes up the prevertebral ganglia?
celiac plexus
superior and inferior mesenteric ganglion
what are the greater and lesser splanchnic nerves?
long preganglionic sympathetic axons to the celiac and mesenteric ganglia
what does the coeliac plexus supply?
vasoconstrictor nerves to the stomach and duodenum
what does the superior mesenteric plexus supply?
ascending and descending colon
what does the inferior mesenteric plexus supply?
bladder and reproductive organs
where are the adrenal glands found?
on top of the kidneys
what are the names of the outer and inner parts of the adrenal glands?
outer - cortex
inner - medulla
describe how adrenaline is made from tyrosine
tyrosine –> DOPA –> dopamine + OH –> noradrenaline + methyl –> adrenaline
what are catecholamines and name the main ones?
hormones produced by the adrenal glands
dopamine, noradrenaline and adrenaline
which sympathetic neurons are noradrenergic?
sympathetic post ganglionic apart from the sweat glands
which hormone do sweat glands use?
acetylcholine
how does the sympathetic NS regulate the distribution of blood around the body?
active at all times
ongoing amounts of vasoconstriction
operates at a low level when youre resting or stressed
give an example of drugs that block the resting tone of sympathetic output
alpha blockers like prazosin
what are side effects of alpha blockers?
postural hypotension
what is postural hypotension and how does it occur?
when you faint when you stand up
body cannot increase vasoconstrictor tone in leg muscle when you stand up so the BP drops and you faint
what adrenoreceptors are found in the brain and heart?
beta-adrenoreceptors
explain how and why sympathetic activity increases during exercise
exercising muscle release local chemical vasodilators
vasodilation would cause low bp and drop in total peripheral resistance
sympathetic outflow increases at start of exercise
global vasoconstriction via noradrenaline esp of non-exercising muscle
cardiac output redirected to exercising muscle
total peripheral resistance is maintained
what are adrenoreceptors?
receptors for adrenaline and noradrenaline
what are the types of adrenoreceptors?
alpha - a1, a2
beta - b1, b2, b3
what types of receptors does noradrenaline act on?
alpha
what action does alpha 1 receptors bring about?
increases contraction
what receptor is mainly found on vascular smooth muscle?
alpha 1
what do alpha 1 antagonists do?
reduce blood pressure
give an example of an alpha 1 antagonist
prazosin
what action does alpha 2 receptors bring about?
reducing noradrenaline release by negative feedback
inhibit insulin release in the pancreas
stimulate glucagon release
contraction of sphincters of gastrointestinal tract
increased thrombocyte aggregation
what receptors are found on presynaptic sympathetic nerve terminals?
alpha 2
what do alpha 2 agonists do?
reduce blood pressure by inhibiting noradrenaline release
give an example of alpha 2 agonist
clonidine
what type of receptors does adrenaline act on?
beta
what do beta 1 receptors do and where are they found?
increase fore and rate of contraction of myocardium
found mainly on heart and kidneys
what do beta 2 receptors do and where are they found?
relax muscle
found mainly in bronchial smooth muscle, gastrointestinal tract, liver and uterus
what do beta 3 receptors do?
increase lipolysis and gluconeogenesis in adipose tissue
what receptors are beta blockers selective for?
beta 1
what are beta blockers used to treat?
manage abnormal heart rhythms
prevent second heart attack
reduce HR and force of contraction in hypertensive patients
what are side effects of beta blockers?
bronchoconstriction fatigue dizziness depression loss of libido exacerbating diabetes
why are beta blockers not the first choice of treatment for hypertension?
not as effective as diuretics, ACE inhibitors and calcium channel blockers
what is the effect of blocking beta 2 and beta 3 receptors?
exacerbating diabetes
what does salbutamol do?
relaxes bronchial smooth muscle in asthmatics by acting on beta 2 receptors
how does the sympathetic nervous system react in severe blood loss?
arterial vasoconstriction in non-essential organs to maintain BP and perfusion of vital organs
kidneys release renin to maintain blood pressure
ADH stimulated to reduce urine output
what do alpha receptors do in severe blood loss?
causes smooth muscle to constrict
platelets become more sensitive to collagen to increase clotting
what does cortisol do?
stimulates adrenaline and noradrenaline synthesis
how is cortisol released
psychological stressors activate the sympathetic NS and the hypothlaamo-pituitary-adrenal axis
HPA releases adrenocorticotrophic hormone
ACTH stimulates cortisol release from adrenal cortex
where is cortisol released from
adrenal cortex