Autonomic Nervous System Part 2 - Lec 4

Autonomic Nervous System (ANS) Part 2 - Lec 4

• Functions of the Autonomic Nervous System: The two systems (sympathetic and parasympathetic) sometimes work opposite one another.

The Eye

• Sympathetic: Dilates the pupil (mydriasis), increases light entering the eye, often during periods of excitement. Relaxes the ciliary muscles, increasing tension on ligaments, causing lens to be less convex, good for distance vision.
• Parasympathetic: Constricts the pupil (miosis), decreases light entering the eye, when too much light hits the eye, or when looking at something close up. Contracts the ciliary muscle, relaxing tension on ligaments, causing lens to be more convex, good for close-up vision.

Eyelid

• Sympathetic: Elevates the upper eyelid (levator palpebrae superioris muscle).
• Parasympathetic: No effect.

Eyeball

• Sympathetic: Can cause exophthalmos (bulging of the eye) due to Muller's muscle contraction.
• Parasympathetic: No effect.

Blood Vessels

• Sympathetic: Causes vasoconstriction (narrowing of blood vessels), reducing blood flow.
• Parasympathetic: No effect.

Glands of the Body

• Nasal, Lacrimal, Salivary, and GI Glands:

  • Sympathetic: Little viscous, concentrated secretions; high enzyme and mucus content.
  • Parasympathetic: Strong stimulation; copious quantities of watery secretions (enzymes, mucus, etc.) released by facial, sublingual, submaxillary, lacrimal, and glossopharyngeal nerves (IX).

• Sweat Glands:

  • Sympathetic: Large quantities of sweat (except on palms and soles), thick, odoriferous secretion.
  • Parasympathetic: Not considered a primary parasympathetic function.

• Axillary Apocrine Glands: Thick, odoriferous secretion, providing lubricant to aid in sliding motion.

  • Sympathetic: The function is thought to aid in movement, lubrication, and odor.
  • Parasympathetic: Not considered a primary parasympathetic function.

Gastrointestinal Tract (GIT)

• Sympathetic: Inhibits peristalsis, increases sphincter tone, slows food passage, decreases secretion, and may cause constipation.
• Parasympathetic: Enhances GIT activity; promotes peristalsis, relaxes sphincters, enhances secretion rates, promotes defecation.

Cardiovascular System (CVS)

• Sympathetic: Increases overall heart activity (e.g., heart rate and strength of contraction).
• Parasympathetic: Decreases overall heart activity (e.g., heart rate), allowing heart to rest between activities.

Lungs

• Sympathetic: Bronchodilation (widening of airways).
• Parasympathetic: Bronchoconstriction (narrowing of airways), increasing bronchial gland secretion, may lead to coughing or phlegm production.

Spleen

• Sympathetic: Contracts spleen capsule, causing stored blood to be released into circulation.
• Parasympathetic: No effect.

Urinary Tract

• Sympathetic: Relaxes urinary bladder wall, contracts internal urethral sphincter, causing retention of urine.
• Parasympathetic: Contracts urinary bladder wall, relaxing internal urethral sphincter, causing urination.

Sexual Organs

• Sympathetic: Contracts smooth muscles of vas deferens, seminal vesicles, and prostate, stimulating ejaculation.
• Parasympathetic: Stimulates secretions in seminal vesicles/prostate, causes erection of the penis.

Skin

• Sympathetic: Vasoconstriction of skin blood vessels.
• Parasympathetic: No significant impact.

Skeletal Muscles

• Sympathetic: Vasodilation of skeletal muscle blood vessels (important in reducing fatigue, improving function).
• Parasympathetic: No effect.

Metabolism

• Sympathetic: Generally catabolic (breakdown of molecules); increases glycogenolysis in liver and muscles, elevated blood glucose.
• Parasympathetic: May be anabolic (building processes); promotes glycogen storage in liver and muscle tissues, supports restorative processes.

Horner's Syndrome

• Cause: Damage to sympathetic chain or superior cervical ganglion.
• Location: Affects half of the face.
• Symptoms: Ptosis (drooping upper eyelid), miosis (constricted pupil), anhydrosis (loss of sweating), enophthalmos (eye sunken), and erythema (redness).

Generalized Sympatho-Adrenal Effect ("Fight or Flight")

• Time: Occurs during stress or emergency situations.
• Involvement: Generalized sympathetic discharge and adrenal medulla stimulates substantial adrenalin release.
• Goal: Aids the body for major exertion through mobilization of energy.

Autonomic Neurotransmitters

• Primary neurotransmitters: Acetylcholine and norepinephrine (sympathetic nerves primarily use norepinephrine, while parasympathetic nerves primarily use acetylcholine).

Adrenergic Receptors

• Specific receptors for norepinephrine (e.g., α1, β1, α2, β2) are discussed for various organs.

High Nervous Control of Autonomic Functions

• Anatomical locations controlling ANS are noted; including the cerebral cortex, hypothalamus, reticular formation, and spinal cord. This is a complex overview and further details are recommended for complete understanding.