Overview of Autonomic Function Flashcards
What is an advantage of somatic neurones only innervating one myofibril?
Allows for precise activation of effectors (skeletal muscle), as compared to mass activation in the autonomic nervous system.
How does the somatic nervous system differ from the autonomic nervous system in terms of the number of neurones between the CNS and the effector?
- There are no neurones between the CNS and skeletal muscles in the somatic nervous system because post-ganglionic neurones of the somatic nervous system originate from the CNS.
- In the ANS, many neurones can exist between the CNS and the effector as the post-ganglionic neurones’ somata are in the PNS.
How do autonomic post-ganglionic synapses differ from somatic post-ganglionic synapses? What is the functional implication of this?
- There are many synaptic terminals along the axons of autonomic fibres (beads on a string).
- Many potential points of neurotransmitter release.
- Functional implication is that multiple effector cells can be activated.
How does the sympathetic innervation of sweat glands differ from the sympathetic innervation of most other effectors?
- Acetylcholine is used as the neurotransmitter between sympathetic postganglionic neurones and the sweat glands (as opposed to noradrenaline which is what you’d expect from a sympathetic postganglionic fibre).
- Here, acetylcholine acts on M3 muscarinic receptors.
- The postganglionic fibres of sweat glands therefore mimic the postganglionic fibres you would expect to see in the parasympathetic system.
Why are the cells of the adrenal medulla said to be neuroendocrine cells?
Their products are released directly into the bloodstream - Endocrine
The adrenal medulla contains neurones similar to sympathetic postganglionic neurones - Neurological
The cells release the neurotransmitter noradrenaline - Neurological
What are the two ways of bringing about sympathetic activity?
- By means of sympathetic innervation.
- By means of circulating adrenaline in the blood that act on non-innervated receptors.
What term best describes the interaction between sympathetic and parasympathetic effects?
Antagonistic
Give an example of where sympathetic and parasympathetic effects to an organ are antagonistic but act on different effectors.
Pupil:
Dilation: SNS -> Dilator Pupillae
Constriction: PNS -> Constrictor Pupillae
Which blood vessels and exocrine glands of the body receive both sympathetic and parasympathetic innervation (as opposed to just sympathetic)?
Blood vessels in the head and reproductive system
and
Exocrine glands in the head and neck
If both parasympathetic and sympathetic innervation of exocrine glands in the head and neck stimulate the glands to release their products, why does the parasympathetic nervous system result in greater volumes of the product being released?
The parasympathetic nervous system will cause vasodilation, so more nutrients will reach the gland. Leads to greater volumes produced.
Sympathetic will cause the opposite.
How does the sympathetic nervous system cause vasodilation?
- Alpha 1 receptors cause vasoconstriction.
- Beta 2 receptors cause vasodilation.
- If a blood vessel has a high enough concentration of beta receptors, vasodilation will occur, because the effects of beta 2 receptor activation overcome that of alpha 1 receptor activation.
- Also directly via sympathetic fibres (in some blood vessels).
Where might blood vessels that contain a high concentration of beta receptors be found?
At skeletal muscle.
List the effects of sympathetic stimulation of the salivary glands.
Saliva production reduced.
List the effects of sympathetic stimulation of the oral / nasal mucosa.
Mucus production reduced.
List the effects of sympathetic stimulation of the heart.
Heart rate and contractility increased.
