Lecture 8 Flashcards
What is the role of the ANS? What is it entirely regulated by?
- To control all involuntary (vegetative) functions, e.g.: HR, BP, GI motility etc.
- The ANS is separate from the voluntary (somatic) motor system. It is entirely efferent (but is regulated by afferent inputs).
What are the key afferent/sensory inputs to the ANS and what do they monitor?
- Sensory neurones monitor CO2, O2 and nutrients in blood, as well as arterial pressure and GIT composition
- Chemoreceptors in carotid body monitor blood O2, CO2 and pH. Chemoreceptors in the carotid artery relay information to the CNS via the glossopharyngeal nerve
- Primary sensory neurones project onto second order sensory neurones in medulla oblongata
SENSORY INFORMATION CONSTANTLY MODULATES THE ACTIVITY OF THE EFFERENT NEURONES OF THE ANS (ANS - VIA THE SYMPATHETIC AND PARASYMPATHETIC)
How is the ANS divided?
- Parasympathetic division
- Sympathetic division
Many tissues recieve both sympathetic and parasympathetic nervous systems
When are the 2 branches of the ANS activated?
- Sympathetic to stressful situations (fight or flight).
- Parasympathetic regulates basal activities (rest & digest)
Give examples of ‘fight or flight’ responses (sympathetic nervous system)
- Increase heart rate
- Increase force of contraction
- Increase blood pressure
This will help the body ‘fight’ in stressful situations
Structure of the ANS: Sympathetic system - which part of the spinal cord?
Where the sympathetic nervous system originates:
Thoracic
Lumbar
Structure of the ANS: Parasympathetic system - where this originates
- vagus nerve
Medullary
Sacral
Vagus nerve:
parasympathetic nerve number 10 is the vagus nerve
Vagus nerve carries information from the CNS out to the key tissues of the body including the heart, lungs and some parts of the GI tract
Where are the cell bodies of sympathetic and parasympathetic neurones arising from the CNS found?
Sympathetic = Thoracic and Lumbar regions Parasympathetic = Medullary and Sacral regions
Describe the general structure of sympathetic and parasympathetic neurones
- nerve make up
- myelination
- where to
- where from
- Both have cell bodies in CNS
- Both have myelinated pre-ganglionic fibres
- Both have unmyelinated post-ganglionic fibres
- Both originate in the lateral horn of their respective CNS regions (mentioned this regions in last flashcard)
- Shorter pre-ganglionic fibres in sympathetic, longer in parasympathetic
- Ganglia within innervated tissues in parasympathetic, ganglia close to spinal cord in sympathetic
Summary of parasympathetic nerves and sympathetic nerves
- *Parasympathetic nerves:**
1. Originate in the lateral horn of the medulla and sacral spinal cord
2. Have long myelinated preganglionic fibres
3. Have short unmyelinated postganglionic fibres
4. Ganglia are located within the innervated tissues
5. Have actions that oppose the sympathetic nervous system - *Sympathetic nerves:**
1. Originate in the lateral horn of the lumbar and thoracic spinal cord
2. Have short myelinated preganglionic fibres
3. Have long unmyelinated postganglionic fibres
4. Ganglia are located in the paravertebral chain close to the spinal cord
5. Have actions that oppose the parasympathetic nervous system
Third division of the autonomic nervous system (ANS)
Enteric nervous system
- has sympathetic and parasympathetic inputs
- Controls the gastrointestinal system, possessing approximately 500 million neurons, and capable of operating independently of the CNS
What neurotransmitter is released from both pre-ganglionic fibres? What does this result in the activation of?
- ACh
- Post-ganglionic nAChR’s (ligand-gated ion channels)
What neurotransmitters are released by the post-ganglionic branches of the ANS? What receptors do these act upon?
Parasympathetic = ACh, acting on mAChR’s in target tissue (GPCR’s)
Sympathetic = mostly noradrenaline (NA), acting on either alpha or beta-adrenoreceptors
What are the sub-divisions of muscarinic acetylcholine receptors and adrenoreceptors?
Muscarinic acetylcholine: M1 - M5
Adrenoreceptors: α1, α2 , and β1 , β2, β3
Which post-ganglionic sympathetic fibres are cholinergic rather than noradrenergic?
What transmitters are sometimes co-released with NA or ACh?
- Those innervating sweat glands and hair follicles, they release ACh rather than NA
- ATP, NO, 5-HT, Neuropeptides.
Why are sympathetic postganglionic neurones in adrenal glands different to the rest?
- They are differentiated to form neruosecretory chromaffin cells. - Chromaffin cells can be considered as postganglionic sympathetic neurons that do not project to a target tissue
- Instead they release adrenaline into the blood stream.
- can see, a release of ACh onto Chromaffin cells, chromaffin cells contain nAChR that depolarisae the chromaffin cell, chromaffin cell then secretes adrenaline into the blood stream (hormone)
Summary of: Sympathetic system, parasympathetic system, somatic efferent system
