Autonomic Nervous System and Visceral Reflexes

A comprehensive set of flashcards covering the key aspects of the autonomic nervous system, visceral reflexes, and the roles of neurotransmitters in the human body.

What does the Autonomic Nervous System (ANS) control?

Glands, cardiac muscle, and smooth muscle.

Name the primary target organs of the ANS.

Viscera of thoracic and abdominal cavities, cutaneous blood vessels, sweat glands, and arrector muscles.

What is denervation hypersensitivity?

Exaggerated response of organs when ANS nerves are severed.

Define visceral reflexes.

Unconscious, automatic, stereotyped responses to stimulation involving visceral receptors and effectors; controlled by ANS.

What are the components of a visceral reflex arc?

Receptors, afferent neurons, integrating center, efferent neurons, effectors.

What tasks does the sympathetic division of the ANS perform?

Prepares the body for physical activity such as exercise, trauma, and fear; initiates the fight-or-flight response.

What happens to heart rate and blood pressure during sympathetic activation?

Heart rate and blood pressure increase.

What function does the parasympathetic division serve?

Calms many body functions and reduces energy expenditure; it assists in bodily maintenance.

What is autonomic tone?

Normal background rate of activity representing the balance of sympathetic and parasympathetic divisions.

List the cranial nerves associated with the parasympathetic division.

Oculomotor (CN 3), Facial (CN 7), Glossopharyngeal (CN 9), Vagus (CN 10).

What are the two subsystems of the ANS?

Sympathetic and parasympathetic.

How do sympathetic and parasympathetic divisions differ in structure?

Sympathetic division has short preganglionic and long postganglionic fibers; parasympathetic has long preganglionic and short postganglionic fibers.

What role do baroreceptors play in the ANS?

They sense increased blood pressure and help regulate heart rate through reflex arcs.

What neurotransmitter is primarily involved in the sympathetic pathway?

Norepinephrine (NE).

Identify the neurotransmitter secreted by parasympathetic postganglionic neurons.

Acetylcholine (ACh).

What are adrenergic fibers?

Nerve fibers that secrete norepinephrine (NE).

What is the role of the adrenal medulla in the ANS?

It secretes catecholamines (epinephrine and norepinephrine) into the bloodstream during sympathetic activation.

What is a key difference in the pathways of somatic and autonomic motor neurons?

Autonomic pathways involve two neurons (preganglionic and postganglionic) while somatic pathways involve one direct neuron to the target organ.

Define dual innervation.

Most viscera receive nerve fibers from both sympathetic and parasympathetic divisions.

How can sympathetic and parasympathetic divisions exert opposing effects on the same target organ?

By secreting different neurotransmitters and having different types of receptors on target cells.

What is the effect of activating alpha-adrenergic receptors?

Usually excitatory effects on the target organ.

Which division of the ANS is responsible for 'rest and digest'?

Parasympathetic division.

What is the significance of the enteric nervous system?

It controls digestive tract motility and secretion independently, with its own neurons and ganglia.

What is Hirschsprung disease?

A hereditary defect causing the absence of enteric plexus in part of the bowel, leading to severe constipation.

How does the hypothalamus function in controlling the ANS?

It contains nuclei that regulate various primitive functions connected to the autonomic responses.

What happens to blood vessels during sympathetic activation?

They typically constrict, leading to increased blood pressure.

What are the two categories of cholinergic receptors?

Muscarinic and nicotinic receptors.

What effect does norepinephrine have on target cells?

It can be either excitatory or inhibitory depending on the type of adrenergic receptor present.

What is the role of MAO inhibitors in pharmacology?

They block the breakdown of monoamine neurotransmitters and are used in treating depression.

What is sympathetic tone?

Baseline activity level of the sympathetic nervous system that affects blood vessel constriction.

What is cooperative effects in dual innervation?

Both divisions work on different effectors to produce a unified overall effect, like saliva production.

How does caffeine affect neurotransmission?

It competes with adenosine, promoting wakefulness by blocking sleep-inducing receptors.

What follows an increase in sympathetic nervous activity?

Vasoconstriction and elevation in heart rate and blood pressure.

What is the function of splanchnic nerves?

They lead to collateral ganglia for innervating abdominal organs without synapsing at sympathetic ganglia.

Explain the role of the Vagus nerve in the parasympathetic division.

It innervates many thoracic and abdominal viscera for functions like slowing heart rate.

What are the effects of muscarinic receptors on target cells?

They can have excitatory or inhibitory effects through second-messenger systems.

What differentiates the sympathetic chain ganglia?

They run alongside the vertebral column and connect to multiple spinal nerves.

What physiological changes occur during parasympathetic activation?

Decrease in heart rate, increased digestion processes, and reduced energy expenditure.

What is the significance of the collateral ganglia?

They contribute to the abdominal aortic plexus and innervate abdominal organs.

What types of actions are autonomic reflexes classified as?

Unconscious and automatic.

What is the main function of the hypothalamus regarding the ANS?

It integrates autonomic functions related to emotional responses like hunger and thirst.

Describe the role of preganglionic fibers in the autonomic pathway.

They extend from the CNS to the autonomic ganglion, where they release neurotransmitters.

What is a primary characteristic of the enteric nervous system?

It operates independently from the central nervous system for gut control.

What types of fibers extend from the sympathetic chain to target organs?

Postganglionic fibers.

How does the sympathetic division influence blood glucose levels?

It increases blood glucose levels for energy.

What physical changes does parasympathetic activity instigate during homeostasis?

It promotes digestion and energy conservation.

What neurotransmitter does the adrenal medulla mainly release?

Epinephrine (adrenaline).