AUTONOMIC FUNCTION Flashcards
Explain the combined action of pupil dilation and constriction
- Iris is smooth muscle and so autonomically innervated
- There is an inner band of smooth muscle
- Dilator Pupillae muscle is innervated by SNS and this results in pupil dilation
- Constrictor pupillae muscle is innervated by PNS and results in pupil constriction
- There is combined action
- Usually PNS is dominant
Give an example of a structure that has single innervation
Blood vessels
Most blood vessels are only innervated by SNS. The level of vasoconstriction or vasodilation depends on the activity of the SNS
Increase in SNS –> Vasoconstriction
Decrease in SNS –> Vasodilation
Blood vessels that aren’t single innervation are in the head and reproductive system - they have Bothe SNS and PNS innervation
Explain the dual innervation of the salivary gland
They have dual innervation where both the SNS and PNS work alongside each other - NOT antagonistic
Both the PNS and SNS stimulate secretory molecules to be released
Secretory molecules are delivered to the salivary gland from blood vessels. Increase in SNS means an increase in vasoconstriction of blood vessels and so less secretory molecules in the gland. PNS results in vasoconstriction and so more secretory molecules in the gland
PNS usually dominant
Explain how SNS innervation can sometimes lead to vasodilation in some blood vessels
Most blood vessels have alpha receptors. These bind to noradrenaline produced by postganglionic neurones in the SNS. This binding results in vasoconstriction
Some blood vessels (e.g vessels of skeletal muscle) have beta receptors. SNS activity that is body-wide will stimulate the adrenal medulla and produce adrenaline. Beta receptors bind to adrenaline and causes vasodilation of blood vessels
Most receptors in the cardiac muscle are beta receptors
The expression will be somewhere in the middle
Which nervous system is responsible for the male erection?
PNS (point)
Which nervous system is responsible for the male ejaculation?
SNS
