Autonomic Nervous System Flashcards
What is an afferent neurone?
A sensory neurone
What does an afferent neurone do?
Carries signals from periphery to CNS
What is an efferent neurone?
A motoneurone or autonomic neurone
What does an efferent neurone do?
Carries signals from the brain or spinal cord to the periphery
What is a ganglion?
A collection of normal cell bodies in peripheral nervous system
What is a pre-ganglionic neurone?
One immediately proximal to ganglion
What is a post-ganglion neurone?
One that is immediately distal to the ganglion
What is an effector?
A target organ through with the nervous system exerts its actions
What is the nervous system split into?
NAME?
What is the relationship between PNS and CNS?
Clearly defined, but linked and dependant on one another. They are continuums of the same cell
What is the central nervous system split into?
NAME?
What is the CNS characterised by?
Bony encasements
What is the brain encased in?
Cranium
What encases the spinal cord?
Stacking of vertebral discs
What is the CNS suspended in?
Cerebrospinal fluid
What is the CNS responsible for?
Sophisticated function of nervous systems
What does the PNS consist of?
- Axons of cranial nerves
- Axons of spinal nerves
- Ganglia
- Nerve plexuses
- Enteric nervous system
How many pairs of ganglia are there the PNS?
- 25 autonomic
- 31 sensory
What are nerve plexuses?
Collections/junctions of neurones
What are the 3 types of nerve plexuses?
- Brachial
- Lumbar
- Sacral
What is the enteric nervous system related to?
The gut
What does the PNS connect?
The CNS to its target organs, or sensory organs to CNS
What does the PNS rely on?
The integrity of the CNS
How can the CNS and PNS be divided?
Into their direction of signalling
What are the two directions of signalling?
NAME?
Where does afferent signalling lead?
To the somatic nervous system
Where does efferent signalling lead?
To the autonomic nervous system
What can the autonomic nervous system be divided into?
- Sympathetic
- Parasympathetic
- Enteric
What carries the output for the somatic nervous system?
1 neurone
Where are the neurones carrying the output of the somatic nervous system located?
Spinally or cranially
Where does an efferent neurone terminate?
Directly on effector organ
What is the effector organ?
Skeletal muscle
What is skeletal muscle activated to do?
Carry out a specific task
What is happening when skeletal muscle isn’t carrying out a specific task?
It is inactive
What is the exception to skeletal muscle being inactive when not performing function?
Motor tone
How is motor tone controlled?
Turned on/off by individual at will
When is skeletal muscle inactivated?
During REM
What is not inactivated during REM sleep?
Muscles that control the eyes, and involved in respiration
Are efferents developed at birth?
No
What is the result of efferents being underdeveloped at birth?
We have to acquire motor skills
When are efferents fully developed?
By puberty
When do efferents start to go downhill?
Age 19+
Is the somatic nervous system under voluntary control?
Yes
What is the purpose of the autonomic nervous system?
Subserves ‘fundamental’ life functions
What fundamental life functions are carried out by the autonomic nervous system?
- Survival of individual
- Promotion of species
- Care of offspring
What does the autonomic nervous system maintain?
A constant internal environment in the body- homeostasis
What does the autonomic nervous system become active along with?
Organogenesis
When does the autonomic nervous system function stop?
It functions non-stop throughout life
How does the autonomic nervous system control function?
By changing the continuous output in 2 opposing systems
What do the predominant actions of the ANS reflect?
An imbalance in the outputs of its two ‘opposing’ systems
What can the autonomic nervous be split into?
NAME?
What are the general actions of the ANS?
NAME?
What is meant by the ANS being responsible for consistency?
It establishes and maintains homeostasis of internal environment in the body
How does the ANS achieve consistency?
Through regulation of systems in the body
What systems does the ANS regulate to ensure consistency?
- Cardiovascular
- Respiratory
- Digestive
- Thermoregulative
What does the ANS do to enable an intermittent change in bias?
Promotes excretory mechanisms of body as and when necessary and appropriate
What are the effector organs of the ANS?
- Visceral organs
- Smooth muscle
- Secretory glands
- Cardiac muscle
What are the similarities between the sympathetic and parasympathetic nervous system?
- Common standard anatomical layout
- Equal numbers of synapses in a series arrangement
How to the sympathetic and parasympathetic nervous systems differ?
- In detail of respective anatomy
- Various synapses use different neurotransmitters
What are the differences between the sympathetic and parasympathetic nervous system the basis of?
General therapies
How does the layout of the autonomic nervous system differ from the somatic?
General layout more complex
How is the autonomic nervous system laid out?
- Always 2 neurones arranged in series
- 1 cell has cell body in CNS
- 1 cell has cell body in PNS
How do the neurones in the ANS exert actions?
Via 3 classes of effector organs
What does the layout of the ANS allow for?
A lot of flexibility
How does the general layout of autonomic efferents appear?
Very simple
What is the general layout of autonomic efferents?
- 2 neurone chains
- 1 neurone in CNS
- 1 neurone wholly in PNS
What is the neurone of autonomic efferents in the CNS called?
Pre-synaptic
Does the pre-synaptic neurone of autonomic efferents supply effector organs?
Not directly
What is the autonomic efferent neurone wholly in the PNS called?
Post-synpatic
What does the post-synaptic neurone of autonomic efferents rely on?
The pre-synaptic neurone to drive it
Where does the post-synaptic neurone of autonomic efferents terminate?
Directly on an effector organ
Give 4 examples of autonomic effector organs
- Smooth muscle
- Secretory glands
- Viscera
- Cardiac muscle
What are transmitters and receptors of the ANS the essence of?
Therapeutics and it’s side effects
What are most organs innervated by?
The ANS
What do most organs receive?
Dual innervation of SNS and PNS
What can be said of most effects of the PNS and SNS?
They are reciprocal
What does autonomic tone vary between?
SNS and PNS dominance
What is predominant ANS tone determined by?
The balance of outputs of SNS and PNS
What receives only SNS drive?
Sweat glands
In what ways can the bladder malfunction?
- Can go into state of retention
- Can be that nothing can be retained
What can cause bladder malfunction?
If the nerves at spinal roots L1-L2 of the sympathetic nervous system, which supply the detrusor blood vessels, or spinal roots S2-S4 of the parasympathetic nervous system are damaged
What part of bladder control is voluntary?
The voluntary sphincter
What spinal roots are involved with the voluntary bladder sphincter?
S2-S4 (Ventral horn - Onuf’s nucleus)
What are the clinical implications of over-activity of the PNS?
NAME?
What can shortage of substrate to the brain lead to?
Fainting
What can shortage of substrate to the tissues of the body lead to?
Necrosis
What is duality of ANS systems rooted in?
2 independent anatomical profiles
What are both divisions of the ANS characterised by?
2 neurones in a chain
What is the neurone of the ANS that is located in the CNS known as?
Pre-ganglionic
Where is the CNS location of the pre-ganglionic neurone of the ANS?
Either brainstem or spinal cord
Are the ANS axons in the CNS myelinated?
Yes
What are the ANS axons of the neurones in the CNS known as?
White Rami Communicates (Communicans)
What does ANS axonal length in the CNS vary depending on?
ANS divison
What is the ANS neurone in the PNS known as?
Post-ganglionic
Where is the stomata of the ANS neurone in the PNS located?
Outside the CNS
What do the stomata of the ANS neurone in the PNS form?
Swellings known as ganglia
Are the ANS axons in the PNS myelinated?
No
What are the ANS axons in the PNS known as?
Grey Rami Communicates (Communicans)
What is the sympathetic nervous system also known as?
Fight-or-flight system
When is the SNS predominantly expressed?
In stressful situations
What is the result of SNS activity?
NAME?
Where does the SNS flow out from?
Spinal cord only
Where to the SNS nerve fibres have cell bodies?
- All 12 thoracic segments of spinal cord (T1→ T12)
- 1st 2 lumbar segments (L1 and L2)
How can complications arise in the SNS?
Following transections of the spinal cord in accidents
What do the post-ganglioic neurones of the SNS express?
Nicotinic receptors
Of what nature are the post-ganglionic neurones of the SNS?
NAME?
Where are the post ganglionic neurones of the SNS adrenergenic?
Adrenal medulla
Of what nature are the pre ganglionic neurones of the SNS?
Cholinergenic
What do effector organs express?
A variety of receptors- α and ß receptors
What is the efferent system associated with?
The paravertebral chain
Where do the majority of efferents of the SNS terminate?
In the paravertebral chain
What is the result of most efferents of the SNS terminating in the paravertebral chain?
Short preganglionic fibres
What are the 3 possible modes of termination of SNS efferents?
NAME?
What do the nerves that don’t synapse in the paravertebral chain tend to be?
Splanchnic nerves
Of what nature are sympathetic postganglionic nerves?
Noradrenergic
What is meant by noradrenergic?
They transmit with noradrenaline
What are the exceptions to the rule of sympathetic postganglionic fibres being noradrenergic?
NAME?
What are the neurones responsible for sweating called?
Pseudomotor
What behaviour do α receptors exhibit?
Either α 1 or α 2 behaviour
What are ß receptors divisible into?
ß 1 or ß 2
What can α and ß receptors exhibit?
Presynaptic inhibition of each other
Where do preganglionic neurones of the SNS have their cell bodies?
In the thoraco-lumbar cord
How long are the pre-ganglionic neurones of the SNS?
Relatively short
What do pre-gaglionic neurones of the SNS do to transmit impulses?
Secrete acetylcholine as the transmitter
How long are the post-gangliotic neurones of the SNS?
Relatively long
What do post-ganglionic neurones of the SNS secrete as their neurotransmitter?
Noradrenaline or adrenaline
What happens when the parasympathetic nervous system is active?
- Reduces heart rate, and force of contraction of the heart
- Promotes digestion
- Promotes bodily functions
- Promotes sleep
Where do the parasympathetic messages flow from?
The the brain and spinal cords
Give 4 cranial nerves
NAME?
What spinal cord levels are used by the PNS?
S2, S3 and S4
What could be said of the pre-ganglionic neurones of the PNS?
They are long and cholinergic
What can be said of the post-ganglionic fibres of the PNS?
They are short, express nicotinic receptors and are cholinergic
What do effector organs in the PNS express?
Muscarinic receptors
What does the layout of autonomic efferents in the PNS allow?
Flexibility by design
How does the layout of autonomic efferents in the PNS allow flexibility?
NAME?
What are nicotinic receptors stimulated by?
Nicotine
What are muscarinic receptors blocked by?
Atropine
