Autonomic nervous system Flashcards
What is the function of the autonomic nervous system?
To control all involuntary responses
Is the autonomic nervous system sensory/afferent or motor/efferent or both?
Motor/efferent
What is the other division of the motor/efferent nervous system? How is it different?
Somatic nervous system - controls all voluntary responses
What are the two divisions of the autonomic nervous system?
Sympathetic nervous system
Parasympathtic nervous system
What is the function of the sympathetic nervous system?
To control all involuntary responses to stressful situations
What is the function of the parasympathetic nervous system?
To control all involuntary responses in resting conditions
Where do the sympathetic nerve fibres originate from?
Lateral horn of spinal cord in thoraco-lumbar regions
Where do sympathetic nerve fibres travel to from the spinal cord?
To the paravertebral sympathetic chain
Where do sympathetic nerve fibres travel to from the paravertebral sympathetic chain?
To their target tissues
Where do parasympathetic nerve fibres originate from?
Lateral horn of spinal cord in medulla and sacral regions of spinal cord
How many neurones are there in autonomic nerve fibres?
Two
What are the names of the two neurones in autonomic nerve fibres?
First one is called pre-ganglionic
Second one is called post-ganglionic
What are ganglia in autonomic nerve fibres?
Where many autonomic neurones synapse
Are the pre-ganglionic and post-ganglionic neurones myelinated?
Pre-ganglionic one is myelinated
Post-ganglionic one is unmyelinated
What are the relative lengths of the pre-ganglionic and post-ganglionic neurones?
In sympathetic nerve fibres, pre-ganglionic is short and post-ganglionic is long
In parasympathetic nerve fibres, pre-ganglionic is long, post-ganglionic is short
How long is the pre-ganglionic neurone in parasympathetic nerve fibres?
So long that it often reaches the target tissue and the ganglion and post-ganglionic neurone both occur in the target tissue
Where are sympathetic ganglia located?
Paravertebral sympathetic chain
What neurotransmitter do pre-ganglionic neurones release?
Both sympathetic and parasympathetic pre-ganglionic neurones release acetylcholine
What type of receptor is found on the post-ganglionic neurones in their synapse with the pre-ganglionic neurone?
Both sympathetic and parasympathetic post-ganglionic neurones have nicotinic acetylcholine receptors
What neurotransmitter do post-ganglionic neurones release?
Sympathetic post-ganglionic neurones release noradrenaline
Parasypathetic post-ganglionic neurones release acetylcholine
What type of receptor is found in target tissue in their synapse with post-ganglionic neurones?
Sympathetic target tissue has adrenoceptors
Parasympathetic target tissue has muscarinic acetylcholine receptors
What is the exception to neurotransmitters released by post-ganglionic neurones and the receptor found in target tissue in the synapse?
Some sympathetic post-ganglionic neurones release acetylcholine
which binds to muscarinic acetylcholine receptors in the target tissue
seen in sweat glands, hair follicles
What are neurotransmitters other than acetylcholine and noradrenaline in the autonomic nervous system called? What are some examples?
Non-adrenergic-non-cholinergic transmitters
- ATP
- NO
How are non-adrenergic-non-cholinergic neurotransmitters released in the autonomic nervous system?
Co-released with either acetylcholine or noradrenaline
What is the exception to there being two neurones in autonomic nerve fibres?
Sympathetic nerve fibres to adrenal glands only contain pre-ganglionic neurone
adrenal medulla chromaffin cells act as the post-ganglionic neurones
What do chromaffin cells do when stimulated?
Release adrenaline and smaller amounts of noradrenaline into the blood
What are the receptors for parasympathetic post-ganglionic neurones in the heart?
M2
Where are M2 receptors in the heart located?
SA node
AV node
What is the outcome of activation of the different M2 receptors in the heart?
SA node - negative chronotropy
AV node - reduced cardiac conduction velocity
What are the receptors for parasympathetic post-ganglionic neurones in smooth muscle?
M3
What is the outcome of activation of M3 receptors in bronchiolar smooth muscle?
Bronchoconstriction
What is the outcome of activation of M3 receptors in intestinal smooth muscle?
Contraction of smooth muscle
giving increased motility
What is the outcome of activation of M3 receptors in bladder smooth muscle?
Contraction of bladder detrusor muscles
relaxation of sphincter muscles
giving passing of urine
What are the receptors for sympathetic post-ganglionic neurones in the heart?
B1
Where are B1 adrenoreceptors located in the heart?
SA node
Ventricles
What is the outcome of activation of the different B1 adrenoceptors in the heart?
SA node - positive chronotropy
Ventricles - positive inotropy
What are the receptors for sympathetic post-ganglionic neurones in smooth muscle?
Vascular smooth muscle - A1, B2
Bronchial smooth muscle - B2
Intestinal smooth muscle - B2
Bladder smooth muscle - B2
What is the outcome of activation of A1 adrenoceptors in vascular smooth muscle?
Vasoconstriction
What is the outcome of activation of B2 adrenoceptors in vascular smooth muscle?
Vasodilation
What is the purpose of vasoconstriction and vasodilation stimulates by sympathetic post-ganglionic neurones?
Redirect blood to muscles from other tissues
What is the outcome of activation of B2 adrenoceptors in bronchiolar smooth muscle?
Bronchodilation
What is the outcome of activation of B2 adrenoceptors in intestinal smooth muscle?
Relaxation of smooth muscle
decreased motility
What is the outcome of activation of B2 adrenoceptors in bladder smooth muscle?
Bladder sphincter muscle contracts
urine is contained in bladder
What is dysautonomia?
Means malfunctioning of the autonomic nervous system
