M6S2 Autonomic Nervous System

Question 1

Autonomic Nervous System (ANS)

Answer 1

-aka visceral motor system
-responsible for transmitting involuntary signals from CNS to smooth muscle, cardiac muscle, and glands
*refer to goodnotes for image

Question 2

Organization of the ANS

Answer 2

• two neuron pathway, meaning that between the CNS and any target organ, there are 2 neurons

Central Nervous System

1. Preganglionic Fibre
   -preganglionic neuron has its cell body within CNS
   -axon enters into PNS and travels to autonomic ganglion
2. Autonomic ganglion
   -where preganglionic and postganglionic neurons meet and communication
   -located in PNS
3. Postganglionic Fibre
   -entirely in PNS
   -cell body is in autonomic ganglion, while it’s axon travels to target organ

Effector Organ

Question 3

The autonomic nervous system can be divided into what two opposing divisions

Answer 3

Sympathetic, parasympathetic

Question 4

Divisions of ANS in detail

Answer 4

-regulates function of internal organs like heart and stomach and controls smooth and cardiac muscles, and glands (things don’t have power over)
-effects on organs and muscles and glands are by no means consistent based on signals CNS sends like:
Changing body temperature, sending extra blood to area, slowing heart beat
-run by two competing organs to either excite (sympathetic) or seduce body (parasympathetic (conserves energy for later)).
-Makes body experince stress, relaxation, fear, courage
-two competing systems differ in:

1. sites of origin of neurons from the CNS
   Sympathetic nervous systems = thoracolumbar area (between thoracic and lumbar vertebrae)
   Parasympathetic nervous systems = craniosacral (base of brain and just superior to tailbone) (around where sympathetic nervous systems do)
2. relative lengths of fibres
   -as appear in different areas of body, neurons themself have slightly different forms, namely length of their axons
   -look at fibres before run into ganglia and after come out
   Preganglionic cell/ fibres - the neurons before ganglion
   Postganglionic cell - the neurons after ganglion
   Sympathetic system = preganglionic fibres must shorter than postganglionic fibres (which makes sense as pre close to spinal cord so not far to go to CNS but lots to reach effectors
   Parasympathetic system = preganglionic fibres much longer than postganglionic fibres (as parasympathetic are so close to or even inside effector organs. Pre goes from cranial to lungs, liver, bladder to effector)
3. Location of their ganglia
   -both parts of autonomic system require 2 neurons in order to work, meet in ganglia (clusters of neurons cell bodies that house millions of synapses)
   Sympathetic ganglia - closer to spinal cord (so can send flight or fight signal far and wide ex. Heart, lungs)
   Parasympathetic ganglia - way out from the spine, near or even inside their effector organs (occur when have time and every to do it like digesting food, uses more specific signals) not everyone involved

Explain why in sympathetic system feel so crazy when one little thing go off compared to parasympathetic which don’t require urgent, all on deck care

Question 5

Comparing sympathetic and parasympathetic nervous system (origin, response, effect)

Answer 5

*refer to image on goodnotes

Question 6

Autonomic pathway: sympathetic

Answer 6

-nerves exit from spinal cord to supply innervation to the body

1. Lateral horn of spinal cord
   -sympathetic preganglionic axons leave lateral horn from spinal cord, along with somatic motor axons to form anterior root
2. Sympathetic truck
   -preganglionic axons pass through spinal nerve to sympathetic trunk, a structure lateral to spinal cord on either side
   -provides pathway for sympathetic fibres to travel through body, both superiorly and inferiorly
3. Ganglion
   -preganglionic neurons synapse with postganglionic neurons in ganglia
4. Effector organ
   -postganglionic axons leave sympathetic trunk to enter spinal nerve and extend to effector tissue/organ at approximately that vertebral level
   *refer to goodnotes for image

Question 7

Autonomic pathway: parasympathetic pathways

Answer 7

-as parasympathetic neurons originate from Brainstem or sacrum, can follow pathway either way

1. Brain/sacrum
   Preganglionic neurons leave brain or spinal cord at level of sacrum
2. Autonomic ganglia
   Preganglionic neurons meet postganglionic neurons in ganglia close to viscera
3. Head/thorax to descending colon/bladder and reproductive organs
   -postganglionic neurons travel to effector organs:
   -postganglionic neurons from CN III, VII, IX supply the head
   - CN X supplies the thorax to descending colon
   - S 2,3,4 supply the terminal gut and pelvic viscera (bladder and reproductive organs)