Autonomic Nervous System Flashcards
What is the visceral efferent component?
The autonomic nervous system (ANS)
What type of involuntary activities does the autonomic nervous system control?
- Smooth muscle activity
- Cardiac muscle activity
- Various glands
What are the 2 divisions of the autonomic nervous system?
Sympathetic and parasympathetic
Where are the cell bodies of pre-ganglionic neurons located in the parasympathetic division of the ANS?
- Brainstem: CN 3, 7, 9, 10
- Sacral spinal cord: S 2, 3, 4
Where are the cell bodies of pre-ganglionic neurons located in the sympathetic division of the ANS?
- Thoracic and lumbar regions of the spinal cord: T1 - L2
Describe the pre and post ganglionic neurons in the parasympathetic NS
Long preganglionic neuron synapse with short postganglionic neuron near effector or in effector organ
Describe the pre and post ganglionic neurons in the sympathetic NS
Preganglionic and postganglionic neurons are similar in length. Synapse in sympathetic chain or one of the collateral ganglia in the adrenal medulla
Describe the effects the parasympathetic NS has on the body
- Generally has discrete actions on single organs, in the body ‘core’: salivary glands, heart
- Conservative, anabolic effects: storing energy, digestion, slowing the heart
- Rest & digest
Describe the effects the sympathetic NS has on the body
- More widespread actions, often affecting the whole body (distribution of sympathetic nerves, circulating adrenaline)
- Homeostasis: blood pressure, thermoregulation
- Flight, fight or fright: meeting demands of active muscles, anxiety
What effect does the sympathetic NS have on the iris (radial muscle, spinchter muscle)?
Contraction
What effect does the sympathetic NS have on the ciliary muscle of the eye?
Relaxation
What effect does the sympathetic NS have on salivary glands?
Secretion (viscous, low volume)
What effect does the sympathetic NS have on lacrimal glands?
Secretion
What effect does the sympathetic NS have on blood vessels?
Constriction (alpha)
Dilation (beta)
What effect does the parasympathetic NS have on the iris (radial muscle and sphincter muscle)?
Contraction
What effect does the parasympathetic NS have on the ciliary muscle?
Contraction
What effect does the parasympathetic NS have on salivary glands?
Secretion (copious, watery)
What effect does the parasympathetic NS have on lacrimal glands?
Secretion
What effect does the parasympathetic NS have on nasal glands?
Secretion
Which neurotransmitters are used in the parasympathetic NS?
Acetylcholine (ACh) - at pre and post ganglionic neuron synapse and also at post ganglionic neuron/effector synapse
Which neurotransmitters are used in the sympathetic NS?
Acetylcholine (ACh) - at pre and post ganglionic neuron synapse
Noradrenaline at post-ganglionic neuron/effector synapse
Adrenaline released from adrenal medulla
What is another name for adrenaline?
epinephrine
What effects does noradrenaline have?
Depends on the receptor
1) alpha receptor: noradrenaline causes vasoconstriction
2) beta receptor: bronchodilation
What effects does adrenaline have?
Depends on the receptor:
1) alpha-1 = contraction of smooth muscle
2) beta-2 = relaxation of smooth muscle
3) beta-1 = increase heart rate and force of heart contraction
Which receptor do beta blockers act on?
Beta-1 receptors
Effects are restricted to the heart
Why do many local anaesthetics contain adrenaline?
Used as a vasoconstrictor
Less blood to wash away anaesthetic -> prolongs activity of anaesthetic
What are the 2 classes of cholinergic receptor?
Muscarinic and nicotinic
Where are muscarinic receptors located?
Post-ganglionic/neuro-effector junctions
What can muscarinic receptors be blocked by?
Atropine
Where are nicotinic receptors located?
Pre-ganglionic/post-ganglionic synapse Neuromuscular junctions (NMJs)
What type of receptor does acetylcholine act on?
Cholinergic receptors: muscarinic and nicotinic
Many organs in the head, thorax, abdomen and pelvis receive both sympathetic and parasympathetic supply. They usually have opposing effects. How is control achieved?
By balancing the effects of sympathetic and parasympathetic nervous supply
Blood vessels and glands in the periphery (e.g. skin) receive sympathetic supply only. How is control achieved?
Varying amount of activity in sympathetic neurons
