the nervous system Flashcards
what is the sympathetic nervous system responsible for?
fight-or-flight response
-increase in HR, force of contraction and blood pressure
what is the role of the parasympathetic nervous system?
regulation of basal activity
what are the anatomical divisions of the brain stem and spinal cord?
medullary, cranial, thoracic, lumbar, sacral
which regions of the spinal cord are involved with the sympathetic and parasympathetic nervous system?
sympathetic: thoracic and lumbar divisions
parasympathetic: medullary and sacral
what is the significance of the paravertebral column?
the location of chemical communication between the sympathetic/parasympathetic nervous system and the effector tissue
what is meant by pre-ganglionic neurone?
the first of 2 axonal projections between the spinal cord and the tissue, myelinated
what are the general rules for parasympathetic nerves?
- long, myelinated pre-ganglionic fibres
- short, unmyelinated post-ganglionic fibres
- ganglia located within innervated tissues
what are the general rules for sympathetic nerves?
- short, myelinated pre-ganglionic fibres
- long, unmyelinated post-ganglionic fibres
- ganglia located in the paravertebral chain close to the spinal cord
which neurotransmitter do all pre-ganglionic neurons use? what does this result in?
Acetylcholine
activation of post-ganglionic nicotinic ACh receptors
which neurotransmitter do parasympathetic post-ganglionic neurons use and how?
Acetylcholine
ACh acts on muscarinic ACh receptors in the effector tissue
which neurontransmitter is used by sympathetic post-ganglionic neurons? give exceptions to this
noradrenaline; interacts with a and B-adrenoceptors
neurons innervating sweat glands/hair follicles may be cholinergic
give examples of non-adrenergic, non-cholinergic (NANC) neurotransmitters
ATP, NO, 5HT (serotonin), neuropeptides
how do sympathetic post-ganglionic neurones in the adrenal glands differ from other symp. post-ganglionic nerves?
they are differentiated to form neurosecretory chromaffin cells, which do not reach the effector tissue. instead they release adrenaline into the blood stream
what are the effects of parasympathetic release of ACh on the heart?
- Bradycardia; ACh acts at M2 muscarinic receptors at SA node
- reduced cardiac conduction velocity: acts at AV node
what are the effects of parasympathetic release of ACh on the smooth muscle?
- bronchiolar contraction
- increased intestinal motility/secretion
- bladder contraction
- penile erection
- cililary muscles and iris sphincter contraction
- all utilise M3-muscarinic receptors
what are the effects of sympathetic release of noradrenaline on the heart?
- tachycardia: NA acts on B1-adrenoceptors in SA node
- positive inotropy: NA acts on ventricles
what are the effects of sympathetic release of noradrenaline in the smooth muscle?
- arteriolar contraction (a1 receptor) and relaxation (B2)
- bronchiolar, intestinal and uterine relaxation
- bladder sphincter contraction
- radial muscle contraction
where can we intervene with ANS activity?
at points of chemical communication
what are the basic steps of neurotransmission?
1) uptake of precursors 2) synthesis of transmitter 3) vesicular storage of transmitter 4) degradation of transmitter 5) depolarisation by propagated action potential 6) depolarisation-dependent influx of Ca2+ 7) exocytotic release of transmitter 8) diffusion to post-synaptic membrane 9) interaction with post synaptic receptors 10) inactivation of transmitter 11) re-uptake of transmitter 12) interaction with pre-synaptic receptors
what is the potential affect of manipulating cholinergic function?
potentially affects all ganglia and all parasympathetic post-ganglionic function
how is acetylcholine synthesised?
acetyl CoA + choline -> acetylcholine + coenzyme A via choline acetyltransferase
where is choline acetyltransferase found?
cholinergic terminals
which enzyme is used to degrade ACh and where is it found?
acetylcholine esterase
found in cholinergic synaptic plates
what is the basis for drugs which act selectively at autonomic ganglia? name one of these drugs
nAChRs at autonomic ganglia and the neuromuscular junction differ in structure
trimethapan
