Autonomic Physiology Flashcards
What does the autonomic nervous system control?
It controls things that you don’t consciously think about.
Smooth muscle surrounding blood vessels, airways, bladder, gut and sex organs.
Secretion from glands.
Focusing of the eye.
What is different about the autonomic nervous System to the somatic system?
It has pre and post ganglionic fibres (myelinated and unmyelinated) and generally acts on smooth muscle.
It has less specialised junctions and can excite or inhibit it’s target.
What are the two sections of the autonomic nervous system?
The sympathetic system which stimulates fight or flight.
The parasympathetic system which involves rest and digest.
Describe the structure of the sympathetic system
It exists from the spinal cord from in the thoracic and lumbar regions. It has short pre ganglionic fibres and long post ganglionic fibres.
The ganglia lie close to the spinal cord in sympathetic trunk or in collateral ganglia or paravertebral ganglia.
White ramus- pre ganglionic fibres
Grey ramus- post ganglionic fibres
There is lots of divergence and convergence between pre and post ganglionic fibres so if one is activated so will a lot of others.
What kind of receptors does acetylcholine act on?
Cholinergic receptors that include nicotine and muscerinic receptors.
What receptors does noradrenaline act on?
Adrenergic receptors such as alpha and beta receptors. They are G protein coupled and occur in different tissues.
What neurotransmitters and receptors does the sympathetic nervous system use?
Pre ganglionic fibres release acetylcholine to act on cholinergic receptors (nicotinic).
Post ganglionic fibres release noradrenaline to act on either alpha or beta receptors.
Post ganglionic cells of adrenal medulla have no axons but release noradrenaline and adrenaline into the blood.
Describe the structure of the parasympathetic nervous system
It exits from the cranial and sacral regions. The ganglia lie close to or within the targets as the post ganglionic fibres are very short.
What neurotransmitters and receptors does the parasympathetic nervous system use?
Preganglionic fibres release acetylcholine to act on nicotinic receptors.
Postganglionic receptors release acetylcholine to act on muscarinic receptors.
What do the alpha and beta receptors trigger?
Alpha receptors generally make muscles contract.
Beta receptors generally make the muscle relax.
What muscles in the eye are affected by the two autonomic nervous systems?
The radial muscle contracts to dilate the pupil.
The circular/sphincter muscle contracts to constrict the pupil.
The ciliary muscle contracts to focus the eye close up and relaxes to make the eye focus far away.
What effect does the sympathetic system have on the heart?
It activates beta one receptors on pacemaker cells to increase the heart rate and activates mainly beta one receptors on myocytes to increase the strength of contraction (para doesn’t have an opposite effect on myocytes).
Which system has an effect on blood vessels?
The sympathetic system controls both constriction and relaxation. (Alpha one and beta two)
Which system has an effect on the energy stores?
The sympathetic nervous system activates alpha and beta receptors on hepatocytes to stimulate glycogenolyis and gluconeogenesis. It activates alpha and beta receptors on lipocytes to increase lipolysis.
Give an example of dual innervation with complementary effects
In the reproductive tract the sympathetic system activates alpha one receptors on smooth muscle on urethra and contracts it to cause ejaculation. The parasympathetic system activates muscarinic receptors on smooth muscle of corpus cavernosum to relax it and cause an erection.
