11 Anatomy of the Autonomic Nervous System Flashcards
Q: What are the 3 nervous systems?
A: central, peripheral, autonomic
Q: Define viscera.
A: the internal organs in the main cavities of the body, especially those in the abdomen
Q: What is the autonomic system responsible for? Where do the different components of the ANS arise?
A: involuntary control of viscera
different parts of the CNS
Q: What are the divisions of the autonomic system? What is the largest component of the ANS?
A: -sympathetic **
-parasympathetic
=> 2 main ones
-enteric= gut system (particularly involved in bowel movements
Q: How are the physiological outcomes of the ANS mainly split? What are these groups called? Energy consumption?
A: parasympathetic
- localised
- conserves body energy (low demand)
sympathetic
- mass responses
- requires lots of NRG
- mobilises multiple body systems at one time
Q: In what situation is the sympathetic NS needed? why?
A: fight or flight response as whole body needs to be activated
Q: Draw a simple diagram explaining central autonomic control. Describe. (6)
A: 2 things initiate:
- higher brain centres: memories and past experiences may modify response
- homeostatic changes: internal monitoring (MAIN)
- > hypothalamus: core of control
- > medulla
2 outcomes:
- sympathetic
- parasympathetic
Q: What is the basic structure for all autonomic pathways? (3)
A: 1. preganglionic neuron which has cell body in CNS
- synapses with ganglion cells in ganglion = accumulation of cell bodies in peripheral system
- post ganglionic fibre goes into body and innervates organs
Q: How do the sympathetic and parasympathetic systems differ in terms of ganglia? (2,1)
A: sympathetic:
- found in sympathetic trunk
- structure is closer to spinal cord that the organ/viscera being innervated
parasympathetic:
-Found close to or even in the organ/viscera they innervate (hence more localised action)
Q: Define afferent nerves and afferent nerves.
A: Afferent nerves carry sensory impulses from all parts of the body to the CNS -> SENSORY
Efferent nerves - “messages” are conducted from the CNS to the muscles and the organs of the body -> MOTOR
Q: In the sympathetic NS, where do the pre-ganglionic efferent fibres arise from? (2) Appearance? Called?
A: Thoracic (spinal) nerves Upper Lumbar (spinal) nerves (L1-3) -> end point varies person to person
in these vertebrae, cross section shows extra grey matter in between curves of butterfly
due to origins: Thoracolumbar outflow
Q: Why do you get sympathetic outflow at some levels but distribution to body from all levels? (4)
A: -due to sympathetic chain= chain of ganglia (close to spinal cord)
-structure allows a number of ways for sympathetic fibres to emerge from T1 to L2/3 and distribute in the body
- easiest way is to just go out spinal cord at that level
- others pass up/down through chain and then distribute with other spinal nerves
Q: Describe the sympathetic pathway (adaption of the basic one for autonomic pathways). (4)
A: 1. Preganglionic neurons in the lateral column grey matter of spinal cord T1 to L2/3
- Emerge from the spinal cord via the ventral root of the spinal nerve
- Pass through ventral ramus to white rami communicantes to ganglion
- Postganglionic fibres distributed to effector organ via grey rami communicantes
Q: Once the sympathetic fibres reach the ganglion, what are the different paths it can take? (3)
A: -immediately synapse within ganglion cell in ganglion at that level
- go through ganglion without synapsing and go up and down to other ganglia
- go through ganglion without synapsing and go to more peripheral subsidiary ganglion
Q: Where does the sympathetic trunk extend from and to? How many ganglia are there in the:
cervical region? importance?
thoracic region?
lumbar region?
pelvis?
A: base of skull to coccyx= base of vertebral column
3 -> important ganglia for head and neck
11 or 12
4 or 5
4 or 5
Q: Where do ganglia of the cervical region lead to? (4) how? From thoracic region? (2) Lumbar region?
A: (cervical post ganglionic fibres form plexus around structures)
- plexus around pharynx
- cardiac p
- thyroid p
- pulmonary p
- p around thoracic aorta
- splanchnic nerves -> go down through diaphragm and innovate contents of abdomen
-Lumbar splanchnic nerves take part in all plexi of sympathetic nerves in abdominal and pelvic regions
Q: Name 7 sympathetic actions.
A: -Blood vessels (vasoconstrictor)
- Sweat glands (secretomotor) = promotes sweat
- Hairs (motor) = stand up
Viscera
- dilation of pupils
- dilation of arterioles
- movement of alimentary tract
- urinary bladder (relaxes walls= allows more urine accumulation, constricts sphincters= no urine release)
Q: What’s the relationship between motor nerves and sympathetic nerves in terms of voluntary muscles?
A: Accompany motor nerves to voluntary muscles but only distributed to blood vessels supplying the muscles
No sympathetic control of voluntary muscles
Q: In the parasympathetic NS, where do the pre-ganglionic efferent fibres arise from? (2) Called?
A: -cranial nerves
-sacral (spinal) nerves
due to origin: cranio scral outflow
Q: What part of the autonomic NS originates from the cervical level?
A: none
Q: Where does sacral outflow (parasympathetic) first go to? then? (2) Difference?
A: 1. Anterior rami of S2-4
2. Visceral branches passing directly to pelvic viscera i.e. pelvic splanchnic nerves
OR to minute ganglia in wall of viscera giving rise to postganglionic fibres
fibres have emerged from spinal cord and go straight out and follow spinal nerve at that level only and go to ganglia which are actually in walls of what is being innervated
Q: Parasympathetic action? (5)
A: -Motor fibres to rectum
- Motor fibres to bladder wall= urine release
- Inhibitory fibres to bladder sphincter
- Erection of penis/clitoris via vasodilator fibres
- Fibres also pass superiorly to supply large part of the gut with visceromotor innervation= gut movement
Q: How many cranial nerves do we have? types?
A: 12, some have parasympathetic functions
Q: Which cranial nerves have parasympathetic functions? Name.
A: cranial nerve CN III= oculomotor nerve
VII= facial nerve
IX= glossopharyngeal
X= vagus
Q: Which ganglion does CN III go to? What travels on from there? to? (2) What is CN III involved in?
A: (oculomotor nerve)
- ciliary ganglion
- postganglionic fibres go to sphincter pupillae and ciliary muscle inside eye
controlling most muscles around eye that allows movement
Q: Which ganglions does CN VII go to? (2) What travels on from them? to? (2,2) What does CN VII promote/cause? (2)
A: (facial nerve)
-Submandibular ganglion
postganglionic fibres to submandibular and sublingual salivary glands (can stimulate salivation is mouth)
-Pterygopalatine ganglion (can cause tears)
postganglionic fibres to paranasal sinuses and lacrimal glands (can cause tears)
Q: Which ganglion does CN IX go to? What travels on from there? to?
A: (glossopharyngeal nerve)
- Otic ganglion
- postganglionic fibres to parotid gland
Q: Where does CN X go to? (2) via? Where does it branch? (5)
A: (vagus nerve)
- enters neck and thorax via carotid sheath (which also contains carotid artery and internal jugular vein)
- branches to lungs, heart, oesophagus, stomach, intestines
Q: What is the enteric system? Function types? (2) Roles. (3,3) Can be overridden by? (2)
A: intrinsic autonomous innovation within gut in walls of alimentary tract
Sensory – monitoring mechanical, chemical and hormonal activity of gut
Motor – gut motility, secretion, vessel tone
Can be overridden by sympathetic and parasympathetic systems
Q: Describe the baroreceptor reflex.
A: 1. reduced venous blood
- decreased CO= decreased arterial BP
- less baroreceptor firing (get decreased vagal tone to heart)
- increased sympa nerve activity = increases CO and increases TPR
- increase arterial BP
Q: What is postural hypotension?
A: when stand can’t get enough blood round body so faint as arterial BP was not maintained (impaired sympa activity)
once supine, blood flow to brain restored
Q: Name and describe 2 drugs that affect pupils.
A: pilocarpine activates muscarinic receptors of pupil and get constriction
tropicamide blocks musc and get pupil dilation
Q: Describe the pupillary light reflex.
A: 1. light shines in eye
2. sensory detects (optic nerve) (cranial II sensory)
para nerves originate from edinger westphal nucleus
- go back via oculomotor nerve (cranial III)= pre gang
- post gang= from ciliary ganglion (para)
- pupillae sphincter affected
