Autonomic nervous system Flashcards
What is the nervous system broken down into?
- Central nervous system
- Peripheral nervous system
What is the central nervous system composed of?
- Brain
- Spinal cord
What is the peripheral nervous system broken down into?
- Autonomic nervous system
- Somatic nervous system
To what does the autonomic nervous system communicate?
- Internal organs
- Glands
To what does the somatic nervous system communicate?
- Sense organs
- Voluntary muscles
What is the autonomic nervous system broken down into?
- Sympathetic division
- Parasympathetic division
What is the function of the sympathetic division?
Arousing
What is the function of the parasympathetic division?
Calming
What is the somatic nervous system broken down into?
- Sensory (afferent) nervous system
- Motor (efferent) nervous system
What is the function of the sensory nervous system?
For sensory input
What is the function of the motor nervous system?
For motor output
Describe the communication link between afferent visceral/sensory input to CNS integration and effector function
Afferent visceral/sensory input is sent in to the CNS, to be processed then depending on the information (electrical conduction / chemical transmission) will be sent into the A.N.S or the S.N.S and then onto effector function.
What type of control is the A.N.S usually involved in?
Subconscious and involuntary
What type of control is the S.N.S usually involved in?
Conscious and voluntary
Give three examples of control areas of the A.N.S
- Mobility - cardiac and smooth muscle
- Secretory glands
- Metabolic - liver and adipose tissue
Give an examples of a control muscle of the S.N.S
Skeletal muscle
What is the function of the efferent division of the P.N.S
It is communication link by which the CNS controls muscles and glands, the effector organs that carry out intended effects or actions
How does CNS regulate the effectors?
By initiating action potentials in the cell bodies of efferent neurons whose axons terminate on these organs
What does the A.N.S regulate? ( x 4 systems)
- Cardiovascular
- Renal
- Gastrointestinal
- Thermoregulatory
Why is A.N.S regulation so important?
To enable the body to meet the continual and ever-changing stresses to which it is exposed.
What innervates cardiac, smooth muscle and glands?
Autonomic nerve fibres
What does the ANS play a role in regulating thanks to autonomic nerve fibres? (9)
(1) Blood pressure and flow,
(2) Gastrointestinal movements and secretions
(3) Body temperature,
(4) Bronchial dilation,
(5) Blood glucose levels,
(6) Metabolism,
(7) Micturition and defecation,
(8) Pupillary light and accommodation reflexes,
(9) Glandular secretions
What is a muscle or gland innervated by autonomic fibres is called?
An effector organ
What happens if the autonomic nerve fibres to an effector organ are cut?
The organ may continue to function, but will lack the capability of adjusting to changing conditions
What are the two functional parts of the ANS?
- Sympathetic nervous system
- Parasympathetic nervous system
When is the sympathetic system involved?
When there is an emergency or where there is stress involved - flight or fight
What is the parasympathetic system involved in (and allows us to do)?
In nonemergencies - allows us to unwind and conserve energy and to “rest and digest”
What are ANS inputs called?
Visceral afferents
What are ANS efferent pathways formed by?
A two neuron chain
What is the direction of impulse in the ANS efferent pathway?
CNS → Preganglionic fibre → autonomic ganglion → Preganglionic neurotransmitter → Postganglionic fibre → Postganglionic neurotransmitter → Effector organ
What do myelinated preganglionic fibres exit the spinal cord via?
Ventral roots
Which fibres are often unmyelinated (C-fibres)?
Postganglionic fibres
Give three points about the preganglionic neuron
- Cell body in brain / spinal cord (lateral horn)
- Axon is myelinated
- Synapses in ganglion
Give three points about the postganglionic neuron
- Cell body is autonomic ganglion
- Axon is unmyelinated
- Synapses on visceral effector
Autonomic nerves pathway
Spinal cord → Preganglionic neuron (myelinated) →Autonomic ganglion → Postganglionic neuron (unmyelinated) → Effectors
Where do sympathetic nerves arise from?
From the lateral horn of the thoracic & lumbar regions of the spinal cord
What size is the axon of preganglionic cell?
Short
Where is the 1st synapse of the sympathetic nervous system?
It’s near the spinal cord within sympathetic chain ganglia
What does the sympathetic system use at the 1st synapse in the ganglion?
Acetylcholine
What does the sympathetic system release at the 2nd synapse in the ganglion?
Noradrenaline
Why is adrenal medulla an exception?
As it’s directly innervated by the preganglionic sympathetic neurons
What is released at the adrenal gland?
Epinephrine released into blood
Where do parasympathethic nerves arise form?
From cranial (brain) & sacral (lower region of spinal cord)
What size (vague) are the axons of preganglionic neuron?
Very long
Where do parasympathetic nerves synapse?
Near their endpoint - muscles/glands
What does the parasympathetic system use at the 1st synapse in the ganglion
Acetylcholine
What does the 2nd synapse of the parasympathetic system release?
Acetylcholine
What is the difference between the preganglionic neuron of the parasympathetic and sympathetic systems?
Para - Soma is usually in the brain-stem or sacral spinal cord
Sym - Soma is usually in the spine
What is the difference between the postganglionic neuron of the parasympathetic and sympathetic systems?
Para - Soma is usually in a ganglion near the target organ
Sym - Soma is in a sympathetic ganglion, located next to spinal cord
What is the difference in the neurotransmitters release from postganglionic synapse in parasympathetic and sympatic systems?
Para - Acetylcholine or nitric oxide
Sym - Norepinephrine
What response is sent to target organ in the parasympathetic nervous system?
‘Rest and digest’
What response is sent to target organ in the sympathetic nervous system?
‘Fight or flight’
What is the neurotransmitter released from the preganglionic synapse is the parasympathetic and sympathetic nervous systems?
Acetylcholine
What is adrenal medulla?
A modified sympathetic ganglion
What is the adrenal gland apart of?
The endocrine system
What do the sympathetic pre-ganglionic fibres do?
They directly stimulate the adrenal medulla (neuroendocrine chromaffin cells)
What do chromaffin cells do in response to stimulation?
They synthesise adrenaline from tyrosine
What is the difference and similarity between adrenaline and noradrenaline?
Adrenaline gives rise to similar effects to noradrenaline except via the bloodstream