Mairead - Parasympathetic Division Flashcards
Where are the ganglia found in the parasympathetic division?
The ganglia are close to or in the wall of its effector organs
Where are the cell bodies of the preganglionic nerves located?
(2)
In the brainstem nuclei
In the lateral horns of the sacral region (S2-S4) of the spinal cord
What are the brainstem nuclei?
(3)
Nuclei = collection of nerve cell bodies found in the CNS
Brainstem = central trunk of the brain, consisting of the medulla oblongata, pons and midbrain, continuing downwards to form a spinal cord
=> brainstem nuclei = preganglion nerve cell bodies in the brainstem of the CNS
The brainstem nuclei have fibres, these run in association with what four cranial nerves?
III
VII
IX
X
What is cranial nerve III called?
Oculomotor nerve
What is cranial nerve VII called?
Facial nerve VII
What is cranial nerve IX called?
Glossopharyngeal IX
What is the cranial nerve X called?
Vagus nerve (X)
The parasympathetic fibres that run in association with the cranial nerves III, VII and IX are responsible for controlling what visceral structures?
(5)
Intrinsic eye muscle
Nasal glands
Tear glands
Salivary glands
Parotid glands
What do the parasympathetic fibres of the vagus cranial nerve do?
(3)
They provide innervation to structure in the neck, thorax and abdomen
The ganglia are located in the walls of these organs
This amounts to 75% of parasympathetic innervation
Preganglionic fibres extend from what segments of the spinal cord?
They extend from the sacral region, from S2 to S4
What are the preganglionic fibres of the sacral region responsible for?
(3)
They form the pelvic nerves
These innervate the organs of the abdomen and the pelvis
Ganglia are located in the walls of these organs
How much divergence is there in the parasympathetic division?
Divergence is 1 to 6-8
Why is there less divergence in the parasympathetic division?
(3)
The preganglionic axons synapse in one ganglion only
The postganglionic axons generally innervate one target organ only
The parasympathetic response is more specific and localised
What is the parasympathetic neurotransmitter?
Its always acetyl choline
What is always the response at the ganglia?
Excitatory
What are the two responses at the target organs?
Excitatory
Inhibitory
What are the two types of parasympathetic receptors?
Nicotinic
Muscarinic
What are nicotinic receptors?
(3)
Type of cholinergic receptor - acetylcholine
Receptors are found in the ganglia and in the neuromuscular junctions
Always excitatory
What are muscarinic receptors?
(3)
Type of cholinergic receptor
‘G’ proteins which when stimulated cause the activation or inhibition of specific enzymes
The effect of activation is longer lasting and either inhibitory or excitatory
What are the five types of muscarinic receptors?
M1
M2
M3
M4
M5
Which muscarinic receptors are excitatory?
M1
M3
What does M1 control?
Salivary and gastric acid secretion
What does M3 control?
Gland secretion
Smooth muscle
What muscarinic receptor is inhibitory?
M2
What does M2 do?
Slows heart rate -> control of cardiac nodal cells
What is the main difference between nicotinic receptors and muscarinic receptors?
Nicotinic are fast and ionotropic
Muscarinic are slow and metabotropic
What hormones are involved in the parasympathetic division?
None
List some body functions/organs the parasympathetic division controls
(8)
Constriction of the pupil
Secretion of digestive hormones from digestive glands, increased motility of the gut
Stimulation of defecation
Contraction of the bladder
Relaxation of the sphincters
Constriction of the airways
Slows the heart rate -> decreases force of contraction
Sexual arousal
Write a note on sympathetic drugs
Sympathomimetic drugs can be taken orally and have long lastnig effects
- e.g. eye drops or inhalers
alpha or beta blockers -> important in treatment of high blood pressure
Write a note on parasympathetic drugs
Parasympathomimetic - Increase gut motility
Parasympathetic blockers control cramps and diarrhoea
