Anatomy + Physiology of the autonomic nervous system Flashcards
what is the autonomic nervous system
the autonomic nervous system is a branch of the peripheral nervous system and it means INDEPENDENT= i.e. the autonomic nervous system is not under conscious control, but is controlled from the brainstem by mechanisms mostly not amenable to conscious control
It branches into the sympathetic, parasympathetic and enteric nervous system
A GROUP OF NEURONAL CELL BODIES LOCATED OUTSIDE OF CNS= _______
A GROUP OF NEURONAL CELL BODIES IN THE CNS= __ ______
A GROUP OF NEURONAL CELL BODIES LOCATED OUTSIDE OF CNS= GANGLIA
A GROUP OF NEURONAL CELL BODIES IN THE CNS= A NUCLEUS
What is the enteric nervous system?
enteric nervous system (ENS) is a large division of the peripheral nervous system (PNS) that can control gastrointestinal behaviour .
- Submucous plexus: control of secretion
- Myenteric plexus: smooth muscle contraction, peristalsis
Types of neurons in the plexi: sensory afferent nerves, interneurones, secretomotor neurones, motor neurones
the sympathetic nervous system leaves the spinal cord at what vertebral level and where are the sympathetic chain ganglia found?
The SNS leaves the spinal cord at T1-L2
the sympathetic chain ganglia are found on the posterior wall of the ribcage
what 3 destinations can a pre-ganglionic nerve have
The pre-ganglionic nerve can have 3 destinations
1. The sympathetic trunk ganglion at the same spinal level
2. The sympathetic trunk ganglion at the higher or lower level
A prevertebral ganglion
what is the difference between a pre-ganglionic + post-ganglionic neuron
The preganglionic neuron travels from its origin in the brain or spinal cord to a ganglion (collection of cell bodies outside the CNS). The postganglionic neuron begins in and travels from the ganglion to the smooth muscle or gland being innervated.
the cell bodies for the sympathetic nervous system are found in which horn of the spinal cord
The cell bodies for the sympathetic nervous system are found in the lateral horn of the spinal cord
- This allows the thoracolumbar region to control all visceral organs
This divergence allows mass action to be coordinated simultaneously
define convergence vs divergence
Divergence = pre-ganglionic fibres branch out to postganglionic fibres at different levels of the chain
Convergence = a postganglionic neuron can receive information from many pre-ganglionic fibres
what is usually the largest of the cervical ganglia
superior cervical ganglion
what are the sympathetic actions of the head
Sympathetic actions in the head are limited mainly to pupil dilation, blushing and reduction of salivation
The sympathetic nervous system normally keeps all the arterioles of the vascular beds in the body slightly _______
The sympathetic nervous system normally keeps all the arterioles of the vascular beds in the body slightly CONSTRICTED
Below the diaphragm
* The main sympathetic chain continues below the diaphragm but in addition there are ganglia which have migrated away from the spinal cord and form plexi
* The prevertebral ganglia consist of one large or several closely adjacent small ganglia and a mesh of pre- and post-ganglionic neurones.
* These are the celiac (solar) ganglion (or plexus), the superior mesenteric ganglion (or plexus) and the inferior mesenteric plexus
The long preganglionic axons to the celiac and mesenteric ganglia are called the greater and lesser __________ _______
Below the diaphragm
* The main sympathetic chain continues below the diaphragm but in addition there are ganglia which have migrated away from the spinal cord and form plexi
* The prevertebral ganglia consist of one large or several closely adjacent small ganglia and a mesh of pre- and post-ganglionic neurones.
* These are the celiac (solar) ganglion (or plexus), the superior mesenteric ganglion (or plexus) and the inferior mesenteric plexus
The long preganglionic axons to the celiac and mesenteric ganglia are called the greater and lesser SPLANCHNIC NERVES
Which plexus supplies sympathetic (vasoconstrictor) nerve fibres to the stomach and initial parts of the small intestine?
The coeliac (celiac) plexus supplies sympathetic (vasoconstrictor) nerve fibres to the stomach and initial parts of the small intestine.
What are the functions of the sympathetic nervous system?
- The sympathetic nervous system regulates the distribution of blood around the body
- It is tonically active at all times.
However it operates at a low level when you are resting, not exercising or stressed.
SNS
- dilates pupils
- inhibits salivation
- relaxes bronchi
- accelerates heartbeat
- inhibits peristalsis + secretion
- stimulates glucose production + release
- secretion of adrenaline+ noradrenaline
- inhibits bladder contraction
- stimulates orgasm
Preganglionic neurons have small myelinated axons, these are known as type ___
Postganglionic neurons have unmyelinated axons, these are known as type ___
- Preganglionic neurons have small myelinated (type Ab) axons
Postganglionic neurons have unmyelinated (type C) axons
describe sympathetic neurotransmission
Sympathetic neurotransmission
* The preganglionic neurons release acetylcholine in the ganglion to activate the postganglionic neuron.
* All autonomic ganglia are of the cholinergic nicotinic type
* The postganglionic sympathetic neurons project to smooth muscle in arterioles (small arteries) and produce vasoconstriction.
* The postganglionic neuron releases noradrenaline on to the arterial smooth muscle to make it contract via an action on alpha 1 (α1) adrenoreceptors
Noradrenaline (norepinephrine) act on other adrenoreceptors to have other effects
tell me the following adrenoreceptor functions:
alpha 1 (α1)
alpha 2 (α2)
β1
β2
β3
alpha 1 (α1) = contriction of vascular smooth muscle, bladder, GI sphincters,glycogenolysis
alpha 2 (α2) = VASOCONSTRICTION + inhibitory feedback mechanism
β1= heart; cardiac contractility, AV-node conduction, renin secretion
β2= lung smooth muscle; bronchodilation, uterus inhibition of labour, glycogenolysis
β3= lypolysis + thermogenesis
- The first neuron in the parasympathetic system arises in either the BRAINSTEM or the SACRAL spinal cord.
- The parasympathetic system is also known as the cranio-sacral autonomic outflow.
Which nerve provides most of the parasympathetic innervation
- The first neuron in the parasympathetic system arises in either the BRAINSTEM or the SACRAL spinal cord.
- The parasympathetic system is also known as the cranio-sacral autonomic outflow.
Most of the parasympathetic innervation to the body is from the VAGUS nerve
Both sympathetic and parasympathetic systems have ____ neurones in series in the motor outflow.
In the parasympathetic system the ganglion is a small structure embedded in the target organ, not a separate structure like the sympathetic ganglia.
Both neurones in the parasympathetic outflow are ________
The first synapse is _____, like the sympathetic system. The second neurone acts on MUSCARINIC (G protein linked) acetylcholine receptors.
Both sympathetic and parasympathetic systems have TWO neurones in series in the motor outflow.
In the parasympathetic system the ganglion is a small structure embedded in the target organ, not a separate structure like the sympathetic ganglia.
Both neurones in the parasympathetic outflow are CHOLINERGIC
The first synapse is NICOTINIC, like the sympathetic system. The second neurone acts on MUSCARINIC (G protein linked) acetylcholine receptors.
Parasympathetic innervation to the head is along which 3 cranial nerves? What effects does stimulation of these nerves produce
Parasympathetic innervation to the head is along cranial nerves III, VII & IX.
Stimulation of these nerves increases secretion of tears, saliva, and nasal mucus. (Also constricts pupil of eye).
The preganglionic neurons are in the various cranial nerve nuclei.
The postganglionic neurons arise in various named ganglia
Sacral parasympathetic preganglionic neurons are found in the intermediolateral horn (a subdivision of the ventral horn) of S1-S4 spinal segments.
They exit the spinal cord, travel in the pelvic splanchnic nerve.
They relay in parasympathetic ganglia to innervate the ______,_____ and ______
this is very important in…..
Sacral parasympathetic preganglionic neurons are found in the intermediolateral horn (a subdivision of the ventral horn) of S1-S4 spinal segments.
They exit the spinal cord, travel in the pelvic splanchnic nerve.
They relay in parasympathetic ganglia to innervate the rectum, genitals and bladder.
Very important in maintenance of continence
their innervation is ‘S2, S3 and S4 keep sh*t off the floor’
What nerve is commonly damaged in childbirth and can lead to incontinence
S2-S4 OFTEN DAMAGED IN CHILDBIRTH = WHY WOMEN OFTEN HAVE INCONTINENCE AFTER The pudendal nerve (S2-S4) is a mixed nerve mainly in charge of the sensory and motor supply of the perineum and external genitalia in both sexes. The nerve arises in the pelvic cavity from the sacral plexus, more specifically from the anterior rami of spinal nerves S2, S3 and S4.
Parasympathetic nervous system functions
- Increased secretion from salivary glands
- Increased GI motility and secretion
- Bladder contraction
- Sphincter relaxation
- Decreased heart rate and contractility
- Bronchoconstriction and secretion
- Pupils contract (miosis) and lens thickens (short range vision)
Lacrimation (crying) and penile erection (vasodilatation)
what are the function of the following muscarinic receptors
*M1 mAChR
*M2 mAChR
*M3 mAChR
There are various forms of muscarinic acetylcholine receptors on the end organs of the parasympathetic system called M1 – M5
They have diverse functions:
M1 mAChR:
Secretion from salivary glands
Gastric acid secretion from stomach
Memory function in brain
M2 mAChR:
Slows heart, also has CNS effects, eg hypothermia
M3 mAChR:
Stimulate insulin secretion from pancreatic beta cells
Bronchoconstriction
In general, they cause smooth muscle contraction and increased glandular secretions (overlap with M1).
