Basic Autonomic Functioning Flashcards
Whats the difference between the effectors innervated by the ANS compared to the Somatic nervous system?
ANS = smooth muscle, cardiac muscle, and glands
not under conscious control
SNS= skeletal muscle
under conscious control
What are the divisions of the ANS
Sympathetic
Parasympathetic
Enteric
What is the difference between neurotransmission in somatic nervous system compared with the autonomic nervous system at the effector
SNS it is discrete can control specific muscle fibres (on off switch) released via synapse at NMJ
ANS= Post ganglionic neurone NT realised from varicosities on effect (small swellings)
many varicosities leads to large scale realises of NT over many cells therefore is said to be diffuse
What is the difference between the SNS and the PNS in terms of function?
Why is this not always the best?
SNS alert and active
(in extreme situations freight flight fight response) but is active all the time in normal conditions
PNS rest and digest (energy conservation)
Very general classification doesn’t quite fit for things like male sex organs
What is a difference between the PNS and SNS in terms of there anatomical strucutre
SNS =
short preganglioninc neurone cell body of preganglionicn neurone thoracicolumbar origin (T1-L2)
Ganglia located in Sympathetic chain close to spinal cord
Long postganglioninc neurone
PNS
long preganglionic neurone
Cell bodies originate from craniosacral origin (CN’s III, VII, IX, X and then S2-S4)
Ganglia located very close to target organ or in the walls of it!
Short postganglionic neurone
What is the difference between the PNS and SNS in terms of neurotransmission
SNS:
Preganglionic neurone releases ACh binds to nAChR’s on postganglionic neuron
Postganglioninc neurone releases Noradrenaline acts on mainly alpha adrenergic receptors
PNS:
Preganglionic neurone releases ACh that acts on nAChR’s on the postganglioinc neurone
Postganglioninc neurone releases ACh too that binds to muscarinic AChR’s on target tissue
What is special about the sweat glands
Receive SNS innervation only
Postganglioninc neurone releases ACh instead of Noradrenaline like you would expect (is still SNS though due to embryological origin)
What is special about the adrenal medulla?
Why is it significant?
Only directly receives preganglioninc SNS innervation
synapse with chromaffin (neuroendocrine) cells derived from neural crest that produce mainly adrenaline but also some noradrenaline
Adrenaline and noradrenaline in this case are therefore hormones and act on non-innervated receptors e.g. smooth muscle in bronchioles and in walls of blood vessels
Describe the effect ANS innervation on the heart
SNS innervation increases the contractility of the heart and increases the heart rate
PNS innervation decreases the heart rate and the contractility of the heart
What type of innervation do most organs have
Dual innervation PNS and SNS
Describe the innervation of the GI tract in terms of PNS and SNS
PNS and SNS can also influence the Gi tract not just enteric
SNS decreases motility (peristalsis) and decreases secretions
Decreased blood flow to Gi tract
PNS increases motility (peristalsis) and increases the amount of secretions released to digest food
increase blood flow to the Gi tract to allow for absorption
how is pupil diameter controlled?
PNS and SNS work antagonistically
SNS fibres innervate radial muscle (dillator pupillae) causing contraction and pupil dilation
PNS fibres innervate circular muscles (sphincter pupillae) causing contraction and constriction
Diameter is controlled by a interplay between SNS and PNS action
Give two examples of single innervation in the ANS
Sweat glands only SNS innervation
MOST blood vessels SNS only
What is the case in most blood vessels?
Only have SNS innervation
Increased SNS activity results in contraction of smooth muscle –> vasoconstriction
Decreased SNS activity vasodilation
What is significant about blood vessels in the head and neck
They have dual innervation
SNS causes vasoconstriction
PNS causes vasodilation
What is significant about the exocrine glands of the head and neck e.g salivary glands?
How do the salivary glands work?
What is the normal level of saliva production?
Receive both PNS and SNS innervation however it is not antagonistic
SNS and PNS innervation both promote production of saliva
Blood vessels supplying the head and neck region have both PNS and SNS innervation
SNS innervation causes vasoconstriction of blood vessels supplying the salivary gland –> this results in less raw components getting to the gland therefore meaning there is less saliva production and the saliva that is produced is thick and sticky (leads to people saying I have a dry mouth when doing speeches)
PNS innervation of blood vessels supplying the salivary gland causes vasodilation
increased amount of raw materials can get to gland leading to increased production of very watery saliva
Normally the PNS dominates over the SNS effect so there is an average quantity of reasonably watery saliva produced
Go on a run decreases
eat something increases
Why is it that blood vessels supplying the heart brain and skeletal muscles vasodillate?
how does this occur
SNS activity body wide results in vasoconstriction of most blood vessels (through release of NA acting primarily on alpha adrenergic receptors on smooth muscle)
Inc SNS activity body wide results in increased activation of neuroendocrine cells in adrenal medulla resulting in increased production of mainly adrenaline but also a smaller amount (20%) NA
Adrenaline binds also binds to alpha adrenergic but preferentially binds to beta adrenergic receptors which are found in high quantities in the smooth muscle of blood vessels supplying the heart and SK muscles
Binding results in vasodilation
Give an important example of where the SNS and PNS work together
Male sex organs
PNS results in erection (point)
SNS results in ejaculation (shoot)
What is the body response to cold and example of
Somatic and ANS working together
Cold SNS causes vasoconstriction of blood vessels supplying the skin
Somatic nervous system increased activity of SK muscles causing shivering to generate heat
