Autonomic nervous system Flashcards
Where do afferent and efferent nerve fibres leave and enter the CNS?
Spinal cord and cranial nerves
What fibres are included in the afferent sensory division?
Somatic and visceral sensory
What fibres are includes in efferent motor division?
Somatic motor and visceral motor
What are visceral motor functions divided into?
Divided in sympathetic and parasympathetic pathways
Pathways innervate identical organs with antagonistically stimulating effects
What is the autonomic nervous system?
Involves motor neurones that are not under the control of the conscious areas of the brain, control involuntary bodily functions (breathing rate, heart rate, dilation, constrictions and secretions.
What is the structure of preganglionic sympathetic fibres?
Myelinated preganglionic fibres leave the CNS and synapse in a ganglion with unmyelinated post ganglionic fibres
Ganglia is close to CNS, therefore preganglionic sympathetic fibres are short
Compare the preganglionic and postganglionic sympathetic fibres with parasympathetic fibres:
Sympathetic: Preganglionic fibres are shorter in comparison to parasympathetic
Postganglionic fibres are longer than PS.
What is the effect of the sympathetic system?
Increased heart rate, blood pressure, dilated bronchi, to increase airflow
Vasodilation in skeletal muscle to allow increased blood flow
Gastrointestinal motility and blood flow decreased
Increasedblood glucose t support high ATP demand
Where do preganglionic sympathetic fibres arise from?
Thoracolumbar segments of the spina cord
Upper 2/3 lumbar, and thoracic
Where do preganglinic sympathetic fibres arise from within the spinal cord?
Lateral horn of the spinal great matter, leaving through the ventral nerve rots
Where do post-ganglionic fibres have their cell bodies?
In sympathetic chain of ganglia that lies either side of the vertebral column or plexus
What are the sympathetic plexi?
Coeliac, superior mesenteric and inferior mesenteric.
Where do preganglionic sympathetic fibres enter?
The sympathetic chain, enter the chain through the white ramus communicans
How is electrical transmission transmitted to structures in head and thorax? (Sympathetic)
Synaptic contact with postganglionic cell bodies in the sympathetic chain of ganglia
How do post-ganglionic fibre return to the spinal cord?
Grey Ramus Communicans
How do preganglionic fibres innervate strictures within the pelvic and abdominal viscera?
Pass uninterrupted through the sympathetic chain ganglia, and travel to the plexuses where corresponding postganglionic cell bodies are located
What neurotransmitter is released at sympathetic preganglionic nerve terminals?
Acetylcholine
Which neurotransmitter is released at sympathetic postganglionic nerve terminals?
Noradrenaline
Which organ is directly innervated by preganglionic fibres?
Adrenal medulla
What effect does the parasympathetic system exert?
Inhibitory effect on viscera with an antagonistic effect on the sympathetic division , concerned with rest
Where do preganglionic parasympathetic nerve fibres arise?
Craniosacral
Where do the postganglionic ganglia lie?
Close to the innervated structures, resulting in longer preganglionic fibres
Which neurotransmitter is released at both pre/and post ganglionic synapses?
Acetylcholine
Where do visceral motor nuclei originate from?
Hypothalamus
Where is the hypothalamus located?
Within the diencephalon
Where are the adrenal glands located?
Superior to the kidney
Which nerve innervates the adrenal medulla?
Preganglionic sympathetic nerve
Where are baroreceptors located?
Carotid sinuses, and aortic arch
What occurs due to reduction in stretch detected by baroreceptors?
.This reduces the stretch on the baroceptors, reduced stimulation is immediately responded by the cardiac control centre- Sends signals to the sympathetic nerve, through the medulla oblogata to stimulate the heart rate and increase the blood pressure by vasoconstriction. Increased electrical stimulation results in release of noradrenaline onto the sino-atrial node, increases frequency of waves of excitation and thus contraction (systole).
Which nervous system influences gut function?
Enteric nervous system
Which type of receptors reside within the gastrointestinal tract?
Chemoreceptors
Which nervous system is concerned with digest?
Parasympathetic
Which nerves do not innervate the lung?
Sympathetic nerves
How does the lung receive sympathetic innervation?
Adrenaline secretion exerts a sympathetic influence through bronchodilation
What is the parasympathetic response to high light intensity?
Pupillary reflex causes pupils to constrict
Oculomotor nerve
What happens to the pupils at low light intensity?
Pupil dilation
What effect does parasympathetic stimulation exert in the micturition reflex on detrusor muscles?
Detrusor muscles contract
What is the purpose of contracted detrusors muscles?
Increases bladder pressure
Which sphincter relaxes during the micturition reflexes?
Internal urethral sphincter
How is the sympathetic pathway inactivated during the micturition reflex?
Onuf’s nucleus is inhibited
What happens during the micturition reflex?
Urine secretion through the bladder and urethra
Where do afferent fibres arising from the bladder through the spinal cord terminate?
Pontine micturition centred cerebellum
What is required for urine excretion to proceed?
Voluntary decision,
Which neurones are excited during the micturition reflex?
neurones on pontine micturition centre transmit electrical impulses to excite sacral pregnaglionic neurones
Which nerve innervates the detrusor muscles?
Pelvic nerve (S2-4)
Which receptors respond to acetylcholine on the detrusor muscles?
Muscarinic ACh receptors
What type of receptors are nicotinic acetyl choline receptors?
Ion channel linked receptors
What type of receptors are Muscarinic ACh receptors?
G-coupled receptors
Which components combine to produce acetylcholine?
Choline and acetyl CoA
Which enzyme catalyses the formation of acetylcholine?
Choline acetyl transferase
How is acetylcholine packaged into synaptic vesicles?
Intrinsic vesicular transportors
Which two receptors do ACh bind onto?
Muscarinic and nicotinic
Which enzyme cleaves and hydrolyses acetylcholine?
Acetylcholinesterases
How is choline taken up into the presynaptic terminal?
Choline-reuptake protein
How is acetylcholinesterase inhibited?
Accumulation and elevated concentration of acetylcholine present in the synaptic cleft
How is noradrenaline produced?
Tyrosine converted to DOPA by tyrosine hydroxylase
DOPA decarboxylated by DOPA decarboxylase into dopamine
Dopamine beta hydroxylase forms NA
Which molecule is the initial precursor of dopamine?
Tyrosine
Which enzyme catalyses the hydroxylation of tyrosine into DOPA?
Tyrosine hydroxylase
Which is the final enzyme for the formation of dopamine from DOPA?
DOPA decarboxylase
Which enzyme is packaged with dopamine by intrinsic transporter proteins into the synaptic vesicle?
Dopamine beta hydroxylase
How is noradrenaline removed from the synaptic cleft?
Transporter reuptake proteins in the presynaptic terminal
Glial cells
Which enzyme degrades noradrenaline?
Monoamine oxidase (MOA) Catechol-o-methyltransferase (COMT)
Which enzyme converts NA to adrenaline in the adrenal gland?
Phenylethanol methyl transferanse
