Ganglion Blockers Flashcards

Flashcards on Ganglion Blockers

Ganglia

Serve as relay stations for autonomic signals.

Acetylcholine (ACh)

The neurotransmitter involved in autonomic ganglia transmission.

Ganglion Blockers

Block nicotinic receptors at autonomic ganglia, inhibiting sympathetic and parasympathetic signals.

Clinical Use of Ganglion Blockers

Rarely used clinically but important in pharmacological and physiological research.

Ganglion Blockers MOA

Block autonomic ganglia by affecting nerve conduction, neurotransmitter synthesis, release, or reuptake (presynaptically) or interaction between ACh and its receptor (postjunctionally).

Nicotinic Receptors

Ganglionic blockers specifically act on these receptors of both parasympathetic and sympathetic autonomic ganglia.

Ganglionic Nicotinic Blockers: Group 1

Includes nicotine and related drugs (e.g., lobeline, tetraethylammonium, hexamethonium); initially stimulates then blocks ganglia; not therapeutically useful.

Ganglionic Nicotinic Blockers: Group 2

Includes Trimethaphan, Mecamylamine; have some therapeutic usefulness but are rarely used; inhibit postsynaptic action of Ach.

Tolerance to Ganglion Blockers

Prolonged administration of these drugs leads to the development of tolerance to their pharmacological effects.

Hypertensive Crisis

Ganglion blockers retain some usefulness in the emergency treatment of this condition.

Controlled Hypotension

Ganglion blockers can be used to achieve this in plastic, neurological, and ophthalmological surgery.

Ganglion Blockers Side Effects

Mild untoward responses include mydriasis, dry mouth, urinary hesitancy, and constipation; more serious include marked hypotension and paralytic ileus.

Nicotine

A component of cigarette smoke, is a poison with many undesirable actions and no therapeutic benefit (except in smoking cessation therapy).

Nicotine Effects on Autonomic Ganglia

Depending on the dose, depolarizes autonomic ganglia, resulting first in stimulation and then in paralysis of all ganglia.

Nicotine Stimulatory Effects

Complex and result from increased release of neurotransmitters in both sympathetic and parasympathetic ganglia.

Cardiovascular Effects of Nicotine

Mimic those seen after activation of the sympathoadrenal system due to release of epinephrine and norepinephrine.

Respiratory Effects of Nicotine (Low Doses)

Stimulate respiration through activation of chemoreceptors in the aortic arch and carotid bodies.

Respiratory Effects of Nicotine (High Doses)

Directly stimulate or depress the respiratory centers.

CNS Effects of Nicotine

Stimulatory and depressant effects including tremors, convulsions, and release of antidiuretic hormone.

Nicotine Absorption

Well absorbed from mucous membranes in the oral cavity, gastrointestinal tract, and respiratory system.

Nicotine Absorption Rate (Oral Mucosa)

If tobacco smoke is held in the mouth, 66 to 77% of the nicotine will be absorbed.

Nicotine Absorption Rate (Inhaled)

Approximately 90 to 98% of the nicotine will be absorbed if tobacco smoke is inhaled.

Nicotine Metabolism

The liver, kidney, and lung metabolize approximately 80 to 90% of the alkaloid.

Trimethaphan Camsylate

An extremely short-acting ganglion blocker used for controlled hypotension during surgery and in hypertensive crisis.

Trimethaphan Camsylate Administration

Administered via continuous infusion to maintain its antihypertensive effect.

Trimethaphan Camsylate Caution

Should be used with caution in patients with allergies due to histamine-releasing properties.

Mecamylamine Hydrochloride

A secondary amine ganglion blocker that easily penetrates cell membranes.

Mecamylamine Absorption

Well absorbed orally and crosses both blood-brain and placental barriers; distribution is not confined to the extracellular space.

Mecamylamine Accumulation

High concentrations of the drug accumulate in the liver and kidney and it is excreted unchanged by the kidney.

Mecamylamine Side Effects

Mostly CNS effects, including tremors, mental confusion, seizures, mania, and depression.

Mecamylamine Use Today

Rarely used today as an antihypertensive drug because it blocks both parasympathetic and sympathetic ganglia.

Autonomic Nervous System

Controls involuntary functions of the body.

Sympathetic Nervous System

The 'fight or flight' system.

Parasympathetic Nervous System

The 'rest and digest' system.

Tetraethylammonium

A nicotinic blocker

Hexamethonium

A nicotinic blocker

Lobeline

A nicotinic blocker

Mydriasis

Dilation of the pupil of the eye.

Syncope

Temporary loss of consciousness caused by a fall in blood pressure.

Paralytic ileus

Obstruction of the intestine due to paralysis of the intestinal muscles.

Angina

Chest pain caused by reduced blood flow to the heart.

Chemoreceptors

Sensory receptors that respond to changes in the chemical composition of the blood or other fluids.

Aortic arch

The curved portion of the aorta from which arteries branch off to the head, neck, and arms.

Carotid bodies

Small clusters of chemoreceptor cells located near the fork of the carotid artery that detect changes in blood oxygen, carbon dioxide, and pH.

Adrenal medulla

The inner part of the adrenal gland that produces epinephrine and norepinephrine.

Adrenergic

Relating to or denoting nerve cells in which epinephrine or norepinephrine serves as the neurotransmitter.

Positive inotropic effect

An increase in the force of contraction of the heart.

Positive chronotropic effect

An increase in the heart rate.

Myocardium

The muscular tissue of the heart.

CNS depressant

A drug that slows down the activity of the brain and nervous system.

Tolerance

Reduced response to a drug after prolonged use.

Antidiuretic hormone

A hormone that helps the body retain water by reducing urine production.

Pituitary

The master gland of the endocrine system, located at the base of the brain.

Gastric acid

A digestive fluid secreted by the stomach.

GIT

Gastrointestinal tract.

Mucous membranes

The lining of various body cavities that secrete mucus.

Oral cavity

The mouth.

Gastrointestinal tract

The digestive system.

Respiratory system

The system that allows us to breathe.

Blood-brain barrier

A protective barrier that prevents unwanted substances from entering the brain.

Placental barrier

A barrier that separates the maternal and fetal blood circulations.

Alkaloid

A nitrogen-containing organic compound of plant origin that has pharmacological activity.

Sympathoadrenal system

The sympathetic nervous system and adrenal medulla working together.

Hypotension

Low blood pressure.

Hypertension

High blood pressure.

Essential hypertension

High blood pressure with no known cause

Neurotransmitter

A chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.

Nicotinic receptor

A type of cholinergic receptor that binds acetylcholine and nicotine. They are present in the autonomic ganglia, neuromuscular junction, and the brain.

Neuromuscular junction

A synapse between a motor neuron and a skeletal muscle fiber.

Neuromuscular antagonist

A drug that blocks the action of a neurotransmitter at the neuromuscular junction, causing muscle paralysis.

Postsynaptic

Occurring or situated after a synapse.

Presynaptic

Occurring or situated before a synapse.

Action potential

A brief electrical signal that travels along the axon of a neuron.

Depolarization

The process of making the inside of a cell less negative relative to the outside.

Reuptake

The process by which a neurotransmitter is reabsorbed by the presynaptic neuron after it has performed its function.

Synthesis

The production of a chemical compound by a living organism.

Therapeutic

Relating to the treatment of disease or injury.

Ganglion

A structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber.

Autonomic ganglia

Clusters of neuronal cell bodies in the autonomic nervous system.

Sympathetic ganglia

Ganglia associated with the sympathetic nervous system, located near the spinal cord.

Parasympathetic ganglia

Ganglia associated with the parasympathetic nervous system, located near or within the organs they innervate.

Cardiovascular system

The system responsible for circulating blood throughout the body.

Chronotropic effect

Affecting heart rate.

Inotropic effect

Affecting the force of heart muscle contraction.

Adrenal gland

Endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol.

Epinephrine

A hormone produced by the adrenal medulla that has stimulatory effects on the body; also known as adrenaline.

Norepinephrine

A neurotransmitter and hormone that has stimulatory effects on the body; also known as noradrenaline.

Respiratory center

The area of the brain that controls breathing.

Brainstem

The part of the brain connecting the spinal cord to the forebrain and cerebrum.

Tremor

An involuntary quivering movement.

Convulsions

Sudden, violent, irregular movements of a limb or of the body, caused by involuntary contraction of muscles.

Diuresis

Increased or excessive production of urine.

Tolerance (drug)

A person's diminished response to a drug, which occurs when the drug is used repeatedly and the body adapts to its continued presence.

Absorption

The process of absorbing or assimilating substances into the cells or across the tissues and organs through diffusion or osmosis, as in absorption of nutrients by the digestive system.”

Distribution (pharmacokinetics)

The process by which a drug leaves the bloodstream and enters the tissues and organs of the body.

Excretion

The process by which metabolic waste products are eliminated from the body.

Metabolize

To break down substances within a living organism.

Muscarinic acetylcholine receptors

A type of acetylcholine receptor that is stimulated by muscarine and blocked by atropine. They are found in various tissues and organs, including the heart, smooth muscle, and glands.

Anticholinergic

An agent that blocks the neurotransmitter acetylcholine in the central and peripheral nervous system.

Histamine

An organic nitrogenous compound involved in local immune responses, as well as regulating physiological function in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus.