Autonomic Nervous System - Structure Flashcards
ANS Type of control
Reflex control of smooth and cardiac muscle
ANS regulation
Unconscious regulation of body’s internal environment
ANS operates through
reflex arcs
Components of reflex arcs
Input
Central Relay
Output
ANS Inputs
Thermoreceptors - Temperature
Nociceptor - Pain
Chemoreceptors - Chemical changes
Baroreceptors - Blood pressure
Input receptors can be found
Heart Blood vessels Lungs Kidneys Gut Bladder Other
ANS Outputs
Autonomic Nerve Fibres
Two divisions of ANS are based on
Anatomical and physiological differences
Two divisions of ANS are
- Sympathetic Nervous System
2. Parasympathetic Nervous System
The sympathetic Nervous System is also known as
Thoracolumbar division
Nerves leave the SNS from
Thoracic T1-T12
Lumbar L1-L3
Sympathetic Trunk of Ganglia is also known as
Sympathetic Chain
PSN is also known as
Craniosacral division
PSN nerves leave from
Cranial Region
Sacral S1-S3
What is a dual innervation?
Input from SNS and PSN
SNS is energy
expending
PSN is energy
conserving
The balance between SNS and PSN is co-ordinated by
hypothalamus
PSN dominates
at rest
SNS become active when
energy expenditure is required
Neurotransmitters of ANS
Acetylcholine
Noradrenaline
Neurotransmitters of ANS bind to
post-ganglionic receptors neurons or on target organs
Same transmitter different actions
SNS and PSN output is a
two-neurone output pathway
ANS two neurones meet at the
autonomic ganglion
Neuron 1 and 2 are called?
pre-ganglionic nerve fibre (1)
post-ganglionic nerve fibre (2)
SNS - Pre-ganglionic nerve is
Short
SNS - Post-ganglionic nerve fibre is
Long
PSN - Pre-ganglionic nerve fibre is
Long
PSN - Post-ganglionic nerve fibre is
short
Anatomical differences SNS and PSN
SNS nerve fibres leave the spinal cord at the THORACOLUMBAR division of the ANS.
PSN nerve fibres leave the spinal cord at the CRANIOSACRAL division of the ANS.
SNS pre-ganglionic nerve fibre is short, and the post-ganglionic nerve fibre is long.
PSN pre-ganglionic nerve fibre is long, and the post-ganglionic nerve fibre is short.
Physiological difference between SNS and PSN
Both use acetylcholine (ACh) at the ganglion
At target organ:
SNS uses Noradrenaline (NA) - except at sweat glands where ACh is used.
PSN uses ACh
What action do SNS and PSN have on the heart
SNS - Increases heart rate
PSN - Decreases heart rate
Adrenal Gland is situated
on top or near kidneys
Role of Adrenal Medulla
Acts as a combination of the sympathetic ganglion and a gland.
Secretes adrenaline and noradrenaline into the circulation (blood)
The effect is prolonged and distant actions
