Lecture 4: Autonomic Nervous System Flashcards
Label an axon slide 4
Ya
Understand how the extension of the meninges envelop the peripheral nerves. Name which meninges surround what part of the nerve.
Dura mater becomes epineurium
Arachnoid mater becomes perineurium
Pia mater becomes endoneurium
The diameter of a nerve fibre is correlated with its function
Slide 5
What forms the sheath around axons in the CNS?
What forms the sheath around the axons in the PNS?
CNS = oligodendrocytes PNS= Schwann cells
What is multiple sclerosis?
Oligodendrocytes are damaged but shwann cells are not
Ie peripheral myelin sheath remain in tact while central myelin sheaths degenerate
Describe the autonomic nervous system
Refer to slide 10
The ANS consist of motor fibres that stimulate involuntary smooth muscle, cardiac muscle and glands.
What are each of the types of neurons for each function ie refer to slide 11
Ya
What is the 2 divisions of the autonomic nervous system, and how are they different?
And what are they concerned with?
Sympathetic and parasympathetic. They are divided by their location of pre-synaptic cell bodies and ganglia. They are concerned with involuntary processes (heart rate, respiration, digestive processes etc
Memorise the table on slide 14
Do it
All sympathetic and parasympathetic nerves contain both general and visceral afferent SENSORY and general visceral efferent MOTOR fibres true or false?
True
Genera visceral afferent (sensory) -mostly sympathetic mediate visceral reflexes ie gag reflex and organic sensations. True or false?
True
Wear is the pre-synaptic cell bodies of the sympathetic NS?
What does its stimulation prepare the body for?
in the lateral horn of grey matter of T1-L12
The para vertebral ganglia in the sympathetic trunk
Stimulation prepares the body for fight or flight
List some of the sympathetic NS activity?
Contracts pupils Reduces secretions from lacrimal and salivary glands Increases heart rate and cardiac output Relaxes bronchial muscles Dilates or constricts skeletal muscle? Constricts arteries to skin and viscera Reduces gut motility and secretions Sphincters contract Relaxes gallbladder Increases secretions from sweat glands
Where are the pre-ganglionic sympathetic neurons for the entire body?
In the interomediolateral cell collumn. Lies between segments T1-L2
What is the course for the pre-synaptic sympathetic motor fibres?
4 pathways:
1. Ascend and then synapse
2. Synapse at same level
3. Descend and then synapse
4. Pass through and continue on through abdominopelvic splanchnic nerve.
They synapse in para vertebral or pre vertebral ganglia
Visceral efferent motor fibres
Axons leave spinal cord through anterior (motor) root
Enter anterior rami of spinal nerves (T1-L2)
Enter into white rami communicantes and pass into sympathetic trunk
4 possible courses (same level, up, down, through)
What is the pathway of sympathetic neurons: C1-C8 levels?
Cell body of pre-synaptic sympathetic neuron in interomediolateral cell column of T1-L2 spinal cord.
Pre-synaptic sympathetic neurons ASCEND to cervical level and synapse in one of three cervical ganglia.
Post synaptic neuron leaves sympathetic trunk and enters grey rami communicante before entering anterior and posterior rami of spinal nerves.
What is the pathway of sympathetic neurons: T1-L2?
Cell body of pre-ganglionic sympathetic neuron in interomediolateral cell collumn of T1-L2.
Myelinated axon leaves spinal cord via anterior (motor) root and enters white rami communicate.
Synapses in sympathetic trunk (splanchnic nerves in pre vertebral ganglia instead)
Post ganglionic unmyelinated neuron leaves via grey rami communicante and enters anterior and posterior rami of spinal nerves.
Slide 24
Pathways of sympathetic neurons: L3-Co levels
Cell body of pre-ganglionic sympathetic neuron in interomediolateral cell column of T1-L2.
Myelinated pre-synaptic sympathetic neuron axon descends in sympathetic trunk and synapses with post-ganglionic neuron in the ganglia of the trunk.
Post-ganglionic unmyelinated neurons leaves the sympathetic trunk via grey rami communicante and enters anterior and posterior rami of spinal nerves.
There are far more POST-synaptic sympathetic fibres than pre-synaptic. True or false?
Post-synaptic sympathetic neurons pass out of sympathetic chain via the grey rami communicantes. True or false?
True
True
This way they can reach virtually all areas of the body to innervate blood vessels, sweat glands and visceral structures.
What is splanchnic nerves?
Myelinated pre-ganglionic fibres passing through the sympathetic trunk without synapsing. Greater splanchnic nerve: T5-T9 Lesser splanchnic nerve: T10-T11 (Synapse in ganglia of celiac plexus) Least, lower splanchnic nerve: T12 Synapse in ganglia if renal plexus
Give a summary on the sympathetic division?
Pre-ganglionic neurons: short, myelinated, cell bodies in lateral horns of grey matter in spinal cord from T1-L2 (thoraco-lumbar outflow)
Ganglionic neurons: sympathetic chain or collateral ganglia on abdominal aorta
Post ganglionic neurons: long, exit sympathetic trunk in gray rami -> spinal nerve-> effector organs.
What is the parasympathetic division responsible for?
We’re are they located? What’s their characteristics?
Etc
Responsible for rest and digest
- preganglionic fibres are long, myelinated, travel through cranial nerves 3, 7, 9 and 10 plus spinal nerves S2-S4
- synapse with short post-ganglionic fibres tha are very close to, or directly on, effector organs
- restricted distribution: head, viscera of trunk, erectile tissue of genitalia.
- not part of spinal nerves except anterior rami (S2-S4)
List the parasympathetic nerves that flow out of the cranium and what they do
CN 3: oculomotor nerves = pupil construction, lense bulge
CN 7: facial nerves= increase secretions from nasal, lacrimal and salivary glands
CN 9: glossopharyngeal nerves= increased secretions from parotid salivary glands
CN 10: vagus nerve = slows HR, contracts bronchioles, dilates visceral arteries, increases gut motility and secretions
Describe referred abdominal pain
Feeling of pian at a location other than the site of origin of the stimulus but in an area supplied by same or adjacent segments of spinal cord.
- Pain afferent a from abdominal viscera follow sympathetic splanchnic nerves back to spinal cord (T5-L2)
- Afferent fibres synapse in dorsal root ganglia. Pain and somatic sensory afferent a synapse in same location = confuses brain!
- visceral pain perceived as somatic pain over corresponding dermatomes.
What does the hypothalamus have to do with the autonomic functions of the body?
Controls all autonomic functions of the body.
Anterior hypothalamus=> excitatory effect on parasympathetic nervous system.
Posterior hypothalamus => excitatory effect on sympathetic nervous system
Hypothalamospinal tract => conveys descending autonomic fibres that influence sympathetic neurons in interomediolateral cell column and preganglionic neurons of sacral parasympathetic nucleus.
What is horners syndrome?
It is die to lesion in pathways of sympathetic fibres travelling to the head.
Clinical signs:
Ptosis: drooping of upper eyelid die to paralysis of superior tarsal smooth muscle
Miosis: pupillary constriction die to paralysis of pupillary dilatory smooth muscle
Anhidrosis: loss of sweating die to loss of sweat gland innervation by sympathetic fibres.
Flushed, warm dry skin: vasodilation of subcutaneous arteries due to lack if vascular tone and sweat gland innervation.
Refer to summary on slide 43
Do it
What 4 cranial nerves carry parasympathetic fibres?
3, 7, 9, 10
