Anatomy + Physiology of the autonomic nervous system

Question 1

what is the autonomic nervous system

Answer 1

the autonomic nervous system is a branch of the peripheral nervous system and it means INDEPENDENT= i.e. the autonomic nervous system is not under conscious control, but is controlled from the brainstem by mechanisms mostly not amenable to conscious control

It branches into the sympathetic, parasympathetic and enteric nervous system

Question 2

A GROUP OF NEURONAL CELL BODIES LOCATED OUTSIDE OF CNS= _______
A GROUP OF NEURONAL CELL BODIES IN THE CNS= __ ______

Answer 2

A GROUP OF NEURONAL CELL BODIES LOCATED OUTSIDE OF CNS= GANGLIA
A GROUP OF NEURONAL CELL BODIES IN THE CNS= A NUCLEUS

Question 3

What is the enteric nervous system?

Answer 3

enteric nervous system (ENS) is a large division of the peripheral nervous system (PNS) that can control gastrointestinal behaviour .

• Submucous plexus: control of secretion
• Myenteric plexus: smooth muscle contraction, peristalsis
  Types of neurons in the plexi: sensory afferent nerves, interneurones, secretomotor neurones, motor neurones

Question 4

the sympathetic nervous system leaves the spinal cord at what vertebral level and where are the sympathetic chain ganglia found?

Answer 4

The SNS leaves the spinal cord at T1-L2

the sympathetic chain ganglia are found on the posterior wall of the ribcage

Question 5

what 3 destinations can a pre-ganglionic nerve have

Answer 5

The pre-ganglionic nerve can have 3 destinations
1. The sympathetic trunk ganglion at the same spinal level
2. The sympathetic trunk ganglion at the higher or lower level
A prevertebral ganglion

Question 6

what is the difference between a pre-ganglionic + post-ganglionic neuron

Answer 6

The preganglionic neuron travels from its origin in the brain or spinal cord to a ganglion (collection of cell bodies outside the CNS). The postganglionic neuron begins in and travels from the ganglion to the smooth muscle or gland being innervated.

Question 7

the cell bodies for the sympathetic nervous system are found in which horn of the spinal cord

Answer 7

The cell bodies for the sympathetic nervous system are found in the lateral horn of the spinal cord

• This allows the thoracolumbar region to control all visceral organs
  This divergence allows mass action to be coordinated simultaneously

Question 8

define convergence vs divergence

Answer 8

Divergence = pre-ganglionic fibres branch out to postganglionic fibres at different levels of the chain

Convergence = a postganglionic neuron can receive information from many pre-ganglionic fibres

Question 9

what is usually the largest of the cervical ganglia

Answer 9

superior cervical ganglion

Question 10

what are the sympathetic actions of the head

Answer 10

Sympathetic actions in the head are limited mainly to pupil dilation, blushing and reduction of salivation

Question 11

The sympathetic nervous system normally keeps all the arterioles of the vascular beds in the body slightly _______

Answer 11

The sympathetic nervous system normally keeps all the arterioles of the vascular beds in the body slightly CONSTRICTED

Question 12

Below the diaphragm
* The main sympathetic chain continues below the diaphragm but in addition there are ganglia which have migrated away from the spinal cord and form plexi
* The prevertebral ganglia consist of one large or several closely adjacent small ganglia and a mesh of pre- and post-ganglionic neurones.
* These are the celiac (solar) ganglion (or plexus), the superior mesenteric ganglion (or plexus) and the inferior mesenteric plexus
The long preganglionic axons to the celiac and mesenteric ganglia are called the greater and lesser __________ _______

Answer 12

Below the diaphragm
* The main sympathetic chain continues below the diaphragm but in addition there are ganglia which have migrated away from the spinal cord and form plexi
* The prevertebral ganglia consist of one large or several closely adjacent small ganglia and a mesh of pre- and post-ganglionic neurones.
* These are the celiac (solar) ganglion (or plexus), the superior mesenteric ganglion (or plexus) and the inferior mesenteric plexus
The long preganglionic axons to the celiac and mesenteric ganglia are called the greater and lesser SPLANCHNIC NERVES

Question 13

Which plexus supplies sympathetic (vasoconstrictor) nerve fibres to the stomach and initial parts of the small intestine?

Answer 13

The coeliac (celiac) plexus supplies sympathetic (vasoconstrictor) nerve fibres to the stomach and initial parts of the small intestine.

Question 14

What are the functions of the sympathetic nervous system?

Answer 14

• The sympathetic nervous system regulates the distribution of blood around the body
• It is tonically active at all times.
  However it operates at a low level when you are resting, not exercising or stressed.

SNS
- dilates pupils
- inhibits salivation
- relaxes bronchi
- accelerates heartbeat
- inhibits peristalsis + secretion
- stimulates glucose production + release
- secretion of adrenaline+ noradrenaline
- inhibits bladder contraction
- stimulates orgasm

Question 15

Preganglionic neurons have small myelinated axons, these are known as type ___
Postganglionic neurons have unmyelinated axons, these are known as type ___

Answer 15

• Preganglionic neurons have small myelinated (type Ab) axons
  Postganglionic neurons have unmyelinated (type C) axons

Question 16

describe sympathetic neurotransmission

Answer 16

Sympathetic neurotransmission
* The preganglionic neurons release acetylcholine in the ganglion to activate the postganglionic neuron.
* All autonomic ganglia are of the cholinergic nicotinic type
* The postganglionic sympathetic neurons project to smooth muscle in arterioles (small arteries) and produce vasoconstriction.
* The postganglionic neuron releases noradrenaline on to the arterial smooth muscle to make it contract via an action on alpha 1 (α1) adrenoreceptors
Noradrenaline (norepinephrine) act on other adrenoreceptors to have other effects

Question 17

tell me the following adrenoreceptor functions:
alpha 1 (α1)
alpha 2 (α2)
β1
β2
β3

Answer 17

alpha 1 (α1) = contriction of vascular smooth muscle, bladder, GI sphincters,glycogenolysis
alpha 2 (α2) = VASOCONSTRICTION + inhibitory feedback mechanism
β1= heart; cardiac contractility, AV-node conduction, renin secretion
β2= lung smooth muscle; bronchodilation, uterus inhibition of labour, glycogenolysis
β3= lypolysis + thermogenesis

Question 18

• The first neuron in the parasympathetic system arises in either the BRAINSTEM or the SACRAL spinal cord.
• The parasympathetic system is also known as the cranio-sacral autonomic outflow.

Which nerve provides most of the parasympathetic innervation

Answer 18

• The first neuron in the parasympathetic system arises in either the BRAINSTEM or the SACRAL spinal cord.
• The parasympathetic system is also known as the cranio-sacral autonomic outflow.
  Most of the parasympathetic innervation to the body is from the VAGUS nerve

Question 19

Both sympathetic and parasympathetic systems have ____ neurones in series in the motor outflow.
In the parasympathetic system the ganglion is a small structure embedded in the target organ, not a separate structure like the sympathetic ganglia.
Both neurones in the parasympathetic outflow are ________
The first synapse is _____, like the sympathetic system. The second neurone acts on MUSCARINIC (G protein linked) acetylcholine receptors.

Answer 19

Both sympathetic and parasympathetic systems have TWO neurones in series in the motor outflow.
In the parasympathetic system the ganglion is a small structure embedded in the target organ, not a separate structure like the sympathetic ganglia.
Both neurones in the parasympathetic outflow are CHOLINERGIC
The first synapse is NICOTINIC, like the sympathetic system. The second neurone acts on MUSCARINIC (G protein linked) acetylcholine receptors.

Question 20

Parasympathetic innervation to the head is along which 3 cranial nerves? What effects does stimulation of these nerves produce

Answer 20

Parasympathetic innervation to the head is along cranial nerves III, VII & IX.
Stimulation of these nerves increases secretion of tears, saliva, and nasal mucus. (Also constricts pupil of eye).
The preganglionic neurons are in the various cranial nerve nuclei.
The postganglionic neurons arise in various named ganglia

Question 21

Sacral parasympathetic preganglionic neurons are found in the intermediolateral horn (a subdivision of the ventral horn) of S1-S4 spinal segments.
They exit the spinal cord, travel in the pelvic splanchnic nerve.
They relay in parasympathetic ganglia to innervate the ______,_____ and ______
this is very important in…..

Answer 21

Sacral parasympathetic preganglionic neurons are found in the intermediolateral horn (a subdivision of the ventral horn) of S1-S4 spinal segments.
They exit the spinal cord, travel in the pelvic splanchnic nerve.
They relay in parasympathetic ganglia to innervate the rectum, genitals and bladder.
Very important in maintenance of continence

their innervation is ‘S2, S3 and S4 keep sh*t off the floor’

Question 22

What nerve is commonly damaged in childbirth and can lead to incontinence

Answer 22

S2-S4 OFTEN DAMAGED IN CHILDBIRTH = WHY WOMEN OFTEN HAVE INCONTINENCE AFTER The pudendal nerve (S2-S4) is a mixed nerve mainly in charge of the sensory and motor supply of the perineum and external genitalia in both sexes. The nerve arises in the pelvic cavity from the sacral plexus, more specifically from the anterior rami of spinal nerves S2, S3 and S4.

Question 23

Parasympathetic nervous system functions

Answer 23

• Increased secretion from salivary glands
  
  • Increased GI motility and secretion
  • Bladder contraction
  • Sphincter relaxation
  • Decreased heart rate and contractility
  • Bronchoconstriction and secretion
  • Pupils contract (miosis) and lens thickens (short range vision)
    Lacrimation (crying) and penile erection (vasodilatation)

Question 24

what are the function of the following muscarinic receptors
*M1 mAChR
*M2 mAChR
*M3 mAChR

Answer 24

There are various forms of muscarinic acetylcholine receptors on the end organs of the parasympathetic system called M1 – M5
They have diverse functions:
M1 mAChR:
Secretion from salivary glands
Gastric acid secretion from stomach
Memory function in brain
M2 mAChR:
Slows heart, also has CNS effects, eg hypothermia
M3 mAChR:
Stimulate insulin secretion from pancreatic beta cells
Bronchoconstriction
In general, they cause smooth muscle contraction and increased glandular secretions (overlap with M1).

Question 25

what do u know about atropine?

Answer 25

Blockade of the parasympathetic nervous system
The classic muscarinic acetylcholine receptor antagonist (blocker) is Atropine.
This is a competitive, reversible nonspecific antagonist of muscarinic acetylcholine receptor
Used preoperatively, for bradycardia, and as eye drops
Atropine was first extracted from the berries of the deadly nightshade plant (atropa belladonna)

Atropine main actions

• Decreases bronchial, GI and other secretions (saliva, tears)
• Causes tachycardia due to block of parasympathetic actions on heart,

Causes pupil dilation (mydriasis) (makes you look aroused!)

Question 26

The role of the CNS in regulating the autonomic nervous system

Question 27

what does the hypothalamus manage

Answer 27

The hypothalamus helps manage your body temperature, hunger and thirst, mood, sex drive, blood pressure and sleep.

• Hypothalamus is a central hub for integrates incoming stimuli from lower- and higher-level centres
  
  • Systemic (from blood & cerebrospinal fluid; e.g. hormones)
  • Interoceptive (the spinal cord and brainstem; e.g. touch/pain)
  • Emotion (corticolimbic system of the brain; e.g. fear)
• It coordinates the functions of the autonomic, emotional and neuroendocrine systems and as such integrates feedback from the viscera
• It responds to these stimuli by releasing hormones (via the pituitary gland) and activating neuronal systems (both down to the brainstem/spinal cord and up to the cortex)
  The hypothalamus is involved in many processes related to internal equilibrium

Question 28

where is cortisol released from

Answer 28

cotrisol is released from adrenal cortex

Question 29

where is adrenaline and noradrenaline released from

Answer 29

adrenaline and noradrenaline is released from the adrenal medulla

Question 30

The hypothalamus causes the release of adrenaline from adrenal medulla, explain what happens next

Answer 30

• The hypothalamus causes the release of adrenaline from adrenal medulla
  
  • Alpha receptors constrict vessels in the gut and redistribute the blood to the exercising muscle.
  • Beta 1 receptors increase cardiac output, while beta 2 receptors relax bronchial smooth muscle to increase ventilation and oxygen uptake.
• The hypothalamus causes the release of cortisol from the adrenal cortex to
  
  • Increase blood glucose and lipolysis
    Supress the immune system