Nervous System Flashcards
What are the actions of the sympathetic nervous system?
Raises heart rate Increases force of contraction Constricts most blood vessels Slows GI transit Constricts sphincters Bronchodilates Increase sweating Dilates pupil (mydriasis) Secretion of seminal fluid/movement of sperm
What are signs of Frey syndrome?
Gustatory sweating of face
What are the actions of the parasympathetic nervous system?
Slows heart rate (no effect on force) Relaxes blood vessels Speeds up GI transit Relaxes sphincters Increases salivation Bronchoconstricts Constricts pupil (miosis) Erection
What are dendrites?
Receptive projections sensitive to neurotransmitter input
What is the soma of a neuron?
Metabolic centre
What is an axon?
One-way rapid communication between cell body and axon terminals
What is an axon terminal?
Form connections with other neurons/effector tissue via synapses
What makes up the CNS?
Brain, spinal cord, retina & CNII
What makes up the PNS?
Spinal & cranial nerves (all except CNII)
Autonomic nervous system
Somatic sensory and motor nerves
What are the 3 branches of motor output?
Somatic motor - skeletal muscle
Brachio motor - pharyngeal arch muscle
Visceral/autonomic motor - organs and vessels
What are the 3 branches of sensory input?
Somatic sensory - sensations from somatic tissue
Visceral sensory - sensations from organs and vessels
Special visceral sensory - taste
At what levels of the spinal cord is a lateral horn seen?
T1-L2 and S2-4
Where do neurons controlling lateral horn cells (or autonomic brainstem nuclei) arise?
Hypothalamus
Where does the sympathetic chain extend up to and finish?
Near base of skull
Ends at tip of sacrum
Which branch of the ANS would be damaged by vertebral damage at L1 level?
Parasympathetic
What does the sympathetic chain communicates with spinal nerves via?
Rami communicans
What is the difference between grey and white rami communicans?
White = preganglionic sympathetic neurons passing into chain Grey = postganglionic sympathetic neurons passing from chain into spinal nerve
Give examples of nerves which emerge from the sympathetic chain
Thoracic and cardiac splanchnic nerves
What is a dorsal root ganglion?
Cell bodies of sensory neurons
At what levels are white rami communicans seen?
T1-L2
At what vertebral levels are grey rami communicans seen?
All levels
Where can brainstem or spinal cord injury proximal to T1 cord level affect supply to?
Sympathetic supply to head
Describe the sympathetic supply to the face
Reticulospinal tract neurons originate in brainstem/hypothalamus
Descend to T1 & synapse with preganglionic neuron in lateral horn
Exit cord with T1 spinal nerve
Travel to sympathetic chain
Run up chain to cervical ganglia & synapse with postganglionic neuron
Postganglionic neurons enter head as plexus around internal carotid artery
Supply face via external carotid artery
What are the 3 sympathetic chain ganglia in the neck?
Superior cervical - C1-4
Middle cervical - C5-6
Stellate - C7-T1, near lung apex
What are sympathetic nerves in the head distributed with?
Cranial nerves and arteries
Describe the distribution of the superior cervical ganglion to the face
Sympathetic neurons form a plexus around the internal carotid artery which join parasympathetic nerves
Distributed with arterial branches
Forms deep petrosal nerve which joins parasympathetic greater petrosal nerve and CN VII
Run to pterygo-palatine ganglion from which they are distributed
Distributed with branches of CN V
What can be the effects of a pterygo-palatine fossa tumour?
Can compress pterygo-palatine ganglion causing loss of sympathetic and parasympathetic innervation to the face
What does loss of sympathetic supply to the head lead to?
Horners syndrome Uneven pupil size / Pupil constriction (miosis) Vasodilation Ptosis - eyelid droop Lack of sweating (anhydrosis)
Which cells of the adrenal medulla release adrenaline?
Chromaffin cells
Describe parasympathetic outflow from the CNS
Parasympathetic nuclei sit in the brainstem
Outflow with CN III, VII, IX & X
Outflow with S2-4 spinal nerves
Which cranial nerve do parasympathetic post ganglionic neurons hitchhike with?
CN V
What can Frey syndrome be caused by?
Parotid surgery or injury
Parasympathetic nerves regrow to skin so innervate muscarinic receptors of sweat glands
What are the 2 principal transmitters in the peripheral nervous system?
Acetylcholine
Noradrenaline
What neurotransmitters does the sympathetic nervous system use?
ACh at pre ganglionic terminals
NA at post ganglionic terminals
Which neurotransmitters does the parasympathetic nervous system use?
ACh at both pre and post ganglionic terminals
Which ACh receptor types does the parasympathetic system use?
Nicotinic at pre ganglionic terminal
Muscarinic at post ganglionic terminal
What are the sympathetic exceptions to the use of nicotinic ACh receptors?
Sweat glands & chromaffin cells in adrenal medulla - muscarinic receptors
What effects do a1 receptor agonists induce?
Blood vessel constriction
GI smooth muscle relaxation
Sphincter contraction
What effects do B1 agonists have?
Increased HR
Increased speed of AV node conduction
increased contraction force
GI smooth muscle relaxation
Where are muscarinic M1 receptors located?
Autonomic ganglia, induce EPSP
Where are muscarinic M2 receptors located?
Heart
Negative chronotropic effects on sinoatrial node, & dromotropic on AV node & atria
Where are muscarinic M3 receptors located?
Smooth muscle and vascular endothelial cells
Cause smooth muscle contraction e.g. Pupil, GI transit
Vascular smooth muscle relaxation - Ca2+ influx and NO release from
endothelial cell – the NO causes decrease in Ca2+ in vascular myocytes)
What is the typical ion concentration of Ca2+ inside and outside the cell?
Inside: 0.2μM
Outside: 2mM
What is the typical ion concentration of Cl- inside and outside the cell?
Inside: 5mM
Outside: 115mM
