Drugs Acting on Autonomic Nervous System - Autonomic Nervous System: General Considerations

67 important questions on Drugs Acting on Autonomic Nervous System - Autonomic Nervous System: General Considerations

What regulates autonomic functions in the autonomic nervous system?

The highest regulation occurs in the hypothalamus, involving sympathetic and parasympathetic nuclei.

Where are the cell bodies of autonomic afferent fibres located?

They are located in the dorsal root ganglion and sensory ganglia of cranial nerves.

What kinds of reflexes do autonomic afferents mediate?

They mediate visceral pain and various visceral reflexes, including cardiovascular and respiratory.
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What divides the motor limb of the autonomic nervous system?

It is divided into sympathetic and parasympathetic pathways for organ innervation.

What is the function of neurohumoral transmission?

Nerves release chemical messengers to transmit messages across synapses and neuroeffector junctions.

Which substance was proven to be a vagal transmitter in 1926?

Acetylcholine was determined to be the vagus substance released during stimulation.

What modulates the release process of neurotransmitters?

The release can be modulated by the transmitter itself and other agents activating specific receptors.

How does an excitatory postsynaptic potential (EPSP) occur?

An EPSP happens due to increased permeability to cations, causing depolarization in the membrane.

What terminates the action of neurotransmitters?

The transmitter is degraded, reuptaken, or diffuses away after binding to receptors.

What does cotransmission imply about neurotransmitter release?

Many neurons release more than one active substance, complicating the one-neurotransmitter model.

Which cotransmitter is associated with acetylcholine in autonomic cholinergic neurons?

Vasoactive intestinal peptide (VIP) is commonly released alongside ACh.

In sympathetic nerves, which cotransmitter is known for long-lasting effects?

Neurotransmitter neuropeptide-Y (NPY) is associated with long-lasting vasoconstriction.

What is indicated by nonadrenergic, noncholinergic transmission?

It shows alternative responses from autonomic innervation during total blockade of classic transmitters.

Describe the time-course of action between primary transmitters and cotransmitters.

They usually have different time-courses, affecting how quickly responses manifest.

What does the autonomic nervous system (ANS) control?

It regulates visceral functions and operates below the level of consciousness.

What type of nerves do most visceral pathways consist of?

These pathways primarily consist of mixed nerves carrying nonmyelinated fibres.

Where are the cell bodies of autonomic afferents located?

Cell bodies are found in the dorsal root ganglion and sensory ganglia.

What reflexes do autonomic afferents mediate?

They mediate visceral pain, cardiovascular, respiratory, and other reflexes.

What areas in the CNS are involved in autonomic functions?

There are no exclusively autonomic areas; significant intermixing occurs with somatic innervation.

What is the highest regulatory seat for autonomic functions?

The hypothalamus regulates autonomic functions with different nuclei for sympathetic and parasympathetic.

Which nuclei in the hypothalamus are primarily sympathetic?

The posterior and lateral nuclei are identified as primarily sympathetic.

Which organs receive innervation from both sympathetic and parasympathetic divisions?

Many organs receive both types of innervation with antagonistic functions.

What primarily increases sympathetic influence on atrial fibres?

Sympathetic influence decreases refractory period of atrial fibres.

Which structures only receive sympathetic innervation?

Most blood vessels, spleen, sweat glands, and hair follicles are examples.

What is neurohumoral transmission?

This process involves nerves transmitting messages via humoral messengers.

Who suggested that sympathetic nerves release an adrenaline-like substance?

Elliott proposed this idea back in 1905.

What did Otto Loewi demonstrate in 1921?

He provided proof of humoral transmission using frog hearts.

What is the transmitter found to be released by the vagus nerve?

The chemical identified was acetylcholine, referred to as 'parasympathomimetic'.

What is the sympathetic transmitter identified in 1946?

Noradrenaline was shown to be the main sympathetic transmitter.

What criteria must a substance meet to be a postjunctional neurohumoral transmitter?

It must be present in the presynaptic neuron and released upon nerve stimulation.

How is the resting transmembrane potential established?

It is created by high K+ permeability and low Na+ permeability across the axon membrane.

What happens to the Na+ conductance during stimulation of a neuron?

It causes a sudden increase in Na+ conductance, leading to depolarization.

How is repolarization achieved following depolarization?

K+ ions exit the cell due to their concentration gradient.

Which agents can block impulse conduction?

Tetrodotoxin and saxitoxin can abolish Na+ conductance in nerve fibers.

Where is the transmitter stored before release?

It is stored in synaptic vesicles within the prejunctional nerve endings.

What causes exocytosis during transmitter release?

Calcium (Ca2+) entry fluidizes membranes, promoting vesicular fusion.

What happens during EPSP generation?

It involves an increase in permeability to cations like Na+ or Ca2+.

How does IPSP affect the membrane?

It increases permeability to anions, leading to hyperpolarization of the membrane.

What does a suprathreshold EPSP generate?

It results in a propagated postjunctional action potential (AP).

How are transmitter actions terminated?

They can be locally degraded or taken back into the prejunctional neuron.

What mediates reuptake of transmitters like norepinephrine?

Norepinephrine transporter (NET) facilitates this process.

What role does cotransmission play in neural signaling?

It shows that neurons can release more than one active substance.

What cotransmitters are associated with ACh in cholinergic neurons?

They commonly include VIP and ATP.

Which transmitter is associated with nitrergic nerves?

The transmitter identified is nitric oxide (NO).

What can affect receptors at some distance from the site of release?

Cotransmitters like NO and VIP can diffuse widely.

What differentiates the action time between primary transmitters and cotransmitters?

Their time-course of action usually differs significantly.

What are examples of amino acid transmitters?

Glutamate and GABA are notable amino acid transmitters.

What is a consequence when peptide neurotransmitters diffuse away?

They are broken down by peptidases at distant sites.

In nonadrenergic, noncholinergic (NANC) transmission, what can happen?

Limited responses can occur even during total adrenergic and cholinergic blockade.

What is the relationship between ATP and NA in sympathetic neurons?

ATP and NA have different action times, with ATP acting faster than NA.

How does cotransmission challenge the classical neurotransmitter model?

It indicates the complexity of neurotransmitter dynamics in neuronal signaling.

Which neurotransmitter is typically encountered in sympathetic neurons?

The primary neurotransmitter commonly found is noradrenaline (NA).

How many active substances can peripheral and central neurons release upon stimulation?

They can release more than one active substance.

What regulates the postsynaptic sensitivity to primary transmitters?

Cotransmitters can modify the responsiveness at the postsynaptic site.

What type of receptors affect transmitter release in prejunctional membranes?

Specific receptors located on the prejunctional membrane modulate release.

What is a characteristic of cotransmitters like NO in terms of function?

They can exert a trophic influence on synaptic structures.

How does the presence of different transmitters in a neuron complicate signaling?

Multiple transmitters can lead to overlapping and nuanced effects.

What defines the function of a cotransmitter in nervous tissue?

Its role can include modifying the response or acting as an alternative transmitter.

Where do cotransmitters get stored in a neuron?

They are stored in specific synaptic vesicles, separate from primary transmitters.

What is the role of ATP in nerve signaling within the autonomous nervous system?

It serves as a cotransmitter, influencing neuronal activity and response.

How do cotransmitters affect vasoconstriction in vascular adrenergic nerves?

They can cause long-lasting vasoconstriction effects.

What is an example of a neurotransmitter involved in gastrointestinal function?

Nonadrenergic, noncholinergic transmission can evoke responses in the gut.

What physiological areas have shown varied responses due to cotransmission?

These have been identified in areas like the vas deferens and urinary tract.

What does the autonomic nervous system (ANS) primarily control?

It primarily controls visceral functions below the level of consciousness.

Where are the cell bodies of autonomic afferent fibres located?

They are found in dorsal root ganglion and sensory ganglia.

Which part of the CNS regulates autonomic functions?

The hypothalamus regulates these functions with sympathetic and parasympathetic nuclei.

What mediates visceral pain and reflexes in the ANS?

Visceral afferents carry impulses that mediate visceral pain and reflexes.

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