Overview of the Nervous system

Question 1

What does the autonomic nervous system do?

Answer 1

-It provides ‘involuntary’ information from the CNS to peripheral organs e.g. increasing heart rate during exercise.

Question 2

What does the somatic nervous system do?

Answer 2

-It provides ‘involuntary’ information from the CNS to motor nerves, skeletal muscles and sensory nerves

Question 3

Do the sympathetic and parasympathetic nervous systems link the central nervous system to peripheral organs?

Answer 3

-Yes they do they link the Central Nervous (system) to peripheral organs such as the heart, lungs and glands

Question 4

What is the Clinical relevance of the Autonomic Nervous system?

Answer 4

• Its important for understanding body functions= as its an important regulation of many diverse systems and organs such as cardiovascular system.
• Its important for understanding pharmacological treatment= as many common diseases involve the ANS and are treated by drugs that act on the ANS e.g. heart disease

Question 5

Why is the Autonomic Nervous System so important?

Answer 5

• It innervates many different cell types and controls many important functions.
• In the heart for example:
• SA node= Regulates heart rate,
• AV node cells= Regulate electrical conduction through heart,
• Cardiac myocytes= Regulates contractility of heart,

In Smooth muscle= The ANS contracts or relaxes smooth muscle cells which are present in many tissues/organs e.g. blood vessels or bladder.

In Gland cells= ANS causes secretions from glandular cells e.g. release of saliva, sweat, insulin, glucagon

Question 6

Overview of Anatomy about the Autonomic Nervous System.

Answer 6

• In the ANS two efferent (away from) neurones arranged in series conduct electrical activity from the Central Nervous system to peripheral tissue/organ,
• In comparison Somatic motor nerves are different- where a single efferent neurone connects CNS to Skeletal muscle.

-An Autonomic ganglion (plural ganglia)- is a group of neuronal cell-bodies lying outside of the CNS

Question 7

Overview of Anatomy- Pre and post ganglionic nerves

Answer 7

• Parasympathetic nerves= Long pre-ganglionic nerves and Short post-ganglionic nerves.
• Sympathetic nerves= Short pre-ganglionic nerves and long post- ganglionic

Question 8

Overview of Chemical transmission,

Answer 8

• Autonomic nerves communicate at synapses,
• Between autonomic nerves at ganglia and between autonomic nerves and peripheral organs- at post ganglionic junctions,
• Synapses use Chemical Transmission for communication

Question 9

Overview of Chemical transmission in ANS

Answer 9

• The Neurotransmitters= Acetylcholine (Ach) and Noradrenaline (NA),
• All pre-ganglionic sympathetic/parasympathetic nerves release Ach acts at nicotinic receptors(Nic) at all Autonomic Ganglia ,
• Post-ganglionic Parasympathetic nerves release Ach which acts at Muscarinic receptors (Mus),
• Post-ganglionic sympathetic nerves release NA (Non-Adrenaline) which acts as Adrenoceptors.
• Stimulation of pre-ganglionic sympathetic fibres release adrenaline (80%) and noradrenaline (20%)

Question 10

What are the functions of Sympathetic and Parasympathetic Nervous systems?

Answer 10

• The ANS is composed of two separate branches:
• Sympathetic Nervous system= ‘Fear, fight and flight’
• Parasympathetic Nervous system= ‘Rest and digest’

Question 11

What are some rules about the functions of the sympathetic and parasympathetic Nervous systems?

Answer 11

• Sympathetic and parasympathetic systems innervate the same organ to produce opposite effects e.g. heart rate and force of contraction
• Sympathetic and Parasympathetic innervate same organ to produce same effect e.g. both innervate secretions from salivary gland,
• Some organs are only innervated by Sympathetic= e.g. sweat glands, kidney, blood vessels.
• Some organs are only innervated by Parasympathetic e.g. pancreas, secretory cells of stomach, lungs

Question 12

ANS contains both Afferents and Efferent fibres

Answer 12

• Autonomic Nervous system is of primary importance in mediating homeostatic involuntary mechanisms- achieved through feedback systems.
• Example: responses to a decrease in blood pressure (e.g. standing up)
  1) Drop in blood pressure,
  2) Change in baroreceptor activity (stretch receptors in aortic arch)
  3) Change in firing of sensory afferent autonomic nerves (afferent fibres) to CNS,
  4) Sensory information processed by CNS
• Signals are sent out via sympathetic nerves (efferent fibres) to the heart, blood vessels, kidney to increase in blood pressure.