Lecture 17- Autonomic nervous system Flashcards
What is the effect of the sympathetic nervous system on the kidney?
1.beta 1 receptor=increase in renin secretion rates 2.alpha 1B receptor=decrease in Na+ absorption 3.alpha 1A receptor= decrease in renal blood flow -more retention of water in tubule, lower blood flow
What does most of visceral activity need?
-visceral motor system
What are the differences between somatic, sympathetic and parasympathetic nerves?
-somatic motor neurons= have body in CNS and protected form the environment by the blood brain barrier and go to target -ANS- has an intrevening synapse, in ganglia
What is the difference in sympathetic and parasympathetic nerves?
- parasympathetic= the ganglia are within the tissue of the target so the postganglion fibre is short
- opposite with the sympathetic
Why is it good that the ANS neurons have that extra synapse?
-the ganglion, the extra neuron gives us more modulation, which we want in ANS where have to weigh more factors
Where are the cell bodies of sympathetic neurons?
- intermediolateral cell column
- in thoracic and lumbar spinal cord only
What does the sympathetic trunk look like?
sympathetic trunk= ganglia, in the swelling is where the ganglion cells are pregaglionic= myelinated -postganlionic cells= grey -another group of ganglionics= prevertebral ganglion = goes to the gut -these are usually in the midline of the gut
Where are the cell bodies of parasympathetic neurons?
- parasympathetic cells=
1. in the brainstem
2-sacral spinal cord in=midbrain and medulla
- long projections, many project via the vagus nerve
- preganglionic in different regions! symp vs parasym
Where in the midbrain are the parasympathetics?
- nucleus ambiguus
- dorsal motor nucleus of vagus
- salivatory nucleii
What innervates the blood to penis?
-parasympathetic (ejaculation is stimulated by sympathetic)
Do tissues receive innervation from both parasympathetic and sympathetic?
-yes -often the innervation goes to different cells in the tissue, -pupil size= para=constricts, symp= makes them bigger -each goes to different muscles -same in pancreas
What is the special example of sympathetic and parasympathetic innervation?
-the same muscles or cells get the innervation from sympathetic and parasympathetic— heart pacemaker cells parasympathetic= slows heart rate, sympathetic= faster heart rate (faster firing of the pacemaker cells)
Via which receptor and transmitter does the somatic nervous system work?
- N1 nicotine acetylcholine receptor
- via acetylcholine
What receptor and neurotransmitter does the parasympathetic nervous system use (both pre and postganglionic)?
- preganglionic= N2 receptor, (Acetylcholine)
- postganglionic= M (muscarinic acetyl choline receptor)
- in both acetylcholine
What receptor and neurotransmitter does the sympathetic nervous system use (both pre and postganglionic)?
2 types:
- pre-N2 receptor (acetylcholine) then post alpha and beta adrenergic receptors (norepinephrine)
- pre- N2 receptor (acetlycholine) and release eponephrine via adrenal medulla
Where does adrenal medulla receive innervation from?
-adrenal medulla= receives input from pre ganglion neuron and releases adrenalin into the circulation -adrenal medulla part of the sympathetic
Which nerves constrict blood vessels?
-sympathetic
What is the cascade of adrenaline?
-catacholamines -adrenergic receptors -dopamine is precursor to noradrenaline
How do dopamine and norepinephrine get made?
- activate postsynaptic and presynaptic receptors
- noradrenaline gets taken back in as does dopamine= cycling
- many drugs (cocain etc) block the transporters that take up the noradrenaline and dopamine
What input do most organs receive?
-receive input from the autonomic nervous system, not all organs receive input from both e.g. many blood vessels = SNS only
What does the autonomic nervous system consist of?
-of two neurons connected in series -the neuron innervating the target occurs outside the CNS
What are the preganglionic axons of the sympathetic division like?
-short -the ganglionic axons project long distances to contact the target tissue
What are the preganglionic axons of the parasympathetic division like?
-long -the ganglionic axons are locate in ganglia in the target tissue
What does the stimulation of sympathetic and parasympathetic innervation have?
-often reciprocal actions -in life work synergistically or under different conditions
What neurotransmitter do preganglionics (ANS) use?
-acetylcholine -acts on ionotropic nicotine receptors N2
What transmitters do ganglionics use?
-sympathetic= noradrenaline (adrenoceptors) -parasympathetic= acetlycholine (muscarinic receptors)
What nervous system does the intestine have?
-extensive nervous system that receives input from the autonomic nervous system but can function independently = enteric nervous system
Where are complex inputs integrated?
-complex sensory inputs from the viscera and higher senses are integrated to enable co-ordinated functioning of the autonomic nervous system -hypothalamus is a major conductors of these co-ordinated responses
What is the anatomy of the pituitary, thalmus etc.?
-
What is the pathway of viscera(ANS) informing the higher centres?
- the preganglionic neurons on their own do not do that much,
- how the brain integrates information to drive the output according to need
- the motor pattern
- end organs provide feedback(the end organ that is important is brain, provides feedback to itself to tell if it is getting enough glucose)
- (baroreceptor reflex)
- the feedback goes to the medulla, the nucleus of the solitary tract
- within the medulla there are loops that can go back to the end organ (baroreceptor reflex is one of these)
- when you get up = barocreceptor reflex makes sure that the blood doesn’t pool in your limbs but goes to the head! so you don’t faint
- unconscious control 2nd loop= from nucleus of solitary tract to hypthalamus, then amygdala then to the cortex= this is the signals that we are aware of= constricted gut etc.
- the info gets processed in the brain, in hypothalamus is important= conductor, from there many projections (to brainstem, etc.)
- hypothalamus sends lot of information and regulates amygdala plays an important role in fearful situations,
Why is hypothalamus key?
- hypothalmus is key, projects to the motor neurons and the endocrine system (via vasopressin for example)
- receives info, contextual and sensory
