Sympathetic Nervous System: Anatomy and Function

Sympathetic Nervous System (SNS)

Part of autonomic nervous system for stress responses.

Autonomic Nervous System (ANS)

Regulates involuntary body functions like heart rate.

Neurotransmitter

Chemical messenger transmitting signals across synapses.

Noradrenaline

Primary neurotransmitter in SNS, affects various organs.

Adrenaline

Hormone released during stress, enhances fight-or-flight response.

Varicosities

Buds from axons releasing neurotransmitters into extracellular space.

Receptors

Proteins that bind neurotransmitters to elicit responses.

G-protein Coupled Receptors

Receptors that activate intracellular signaling pathways.

a1-adrenoceptors

Excitatory receptors causing smooth muscle contraction.

a2-adrenoceptors

Inhibitory receptors reducing neurotransmitter release.

b1-adrenoceptors

Excitatory receptors increasing heart rate and contractility.

b2-adrenoceptors

Receptors causing smooth muscle relaxation, especially in bronchi.

b3-adrenoceptors

Receptors involved in lipolysis in adipose tissue.

Mydriasis

Pupil dilation caused by SNS activation.

Glycogenolysis

Breakdown of glycogen to glucose during stress.

Renin Release

Hormonal release from kidneys, increases blood pressure.

Lipolysis

Breakdown of fats for energy during stress.

Vasodilation

Widening of blood vessels, reducing blood pressure.

Vasoconstriction

Narrowing of blood vessels, increasing blood pressure.

Adrenergic Agonists

Drugs activating adrenergic receptors to mimic SNS effects.

Adrenergic Antagonists

Drugs blocking adrenergic receptors to inhibit SNS effects.

Phenylephrine

a1 agonist used for nasal congestion relief.

Salbutamol

b2 agonist used to relax bronchial muscles.

Prazosin

a1 antagonist used to treat hypertension.

Propranolol

b1/b2 antagonist reducing heart rate and anxiety.

Sympathomimetics

Drugs mimicking SNS effects, can cause insomnia.

Sympatholytics

Drugs inhibiting SNS effects, may cause fatigue.

Catechol-O-methyltransferase (COMT)

Enzyme degrading catecholamines like noradrenaline.

Monoamine Oxidase A (MAO-A)

Enzyme degrading neurotransmitters in presynaptic neurons.

Extraneuronal Transport

Transport of neurotransmitters into non-neural cells.

Adrenal Medulla

Inner part of adrenal gland, secretes adrenaline.

Dopamine

Precursor to noradrenaline, involved in neurotransmission.