Immunity

Overview of Immunity

The immune system protects the body from pathogens and foreign substances through a complex network of cells, molecules, and responses. Immunity can be classified as innate or adaptive, each with distinct mechanisms and components.

• NK cells (Natural Killer cells): Lymphocytes that target and destroy virus-infected cells and tumor cells without prior sensitization.

• Interferons: Proteins released by host cells in response to pathogens, especially viruses, that help inhibit viral replication and activate immune cells.

• Complete antigens: Substances that can provoke an immune response and react with the products of that response (antibodies or T cells).

• Adaptive immunity: Specific defense system involving lymphocytes (B and T cells) that recognize and remember specific pathogens.

• Innate immune system defenses: Non-specific defenses including physical barriers (skin, mucous membranes), phagocytes, and chemical mediators.

• Phagocyte mobilization: The process by which phagocytic cells (e.g., neutrophils, macrophages) are recruited to sites of infection or injury.

• Fever: An increase in body temperature that enhances immune function and inhibits pathogen growth.

• Autoimmune disease: Disorders in which the immune system attacks the body's own tissues.

• Inflammation: A localized response to injury or infection characterized by redness, heat, swelling, and pain.

• Passive immunity vs Active immunity:

  • Passive immunity: Short-term immunity acquired by receiving antibodies from another source (e.g., maternal antibodies, antibody therapy).

  • Active immunity: Long-term immunity developed after exposure to an antigen (infection or vaccination).

Example:

Vaccination is an example of active immunity, while receiving antivenom after a snake bite is passive immunity.

Endocrine System

Introduction to the Endocrine System

The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate various physiological processes. Hormones act as chemical messengers and influence growth, metabolism, and homeostasis.

• Endocrine gland stimulus: The mechanism by which endocrine glands are triggered to release hormones, such as humoral, neural, or hormonal stimuli.

• Define hormones: Chemical messengers produced by endocrine glands that travel through the blood to target organs.

• List of hormones which work through second messenger system:

  • Examples: Insulin, Glucagon, ACTH, TSH, FSH, LH

  • Second messenger systems often involve cyclic AMP (cAMP) or calcium ions.

• List of hormones which are lipid soluble and make a hormone receptor complex inside the cytosol:

  • Examples: Steroid hormones (e.g., aldosterone, cortisol, sex hormones)

  • These hormones pass through the cell membrane and bind to intracellular receptors.

• Oxytocin: A peptide hormone involved in uterine contraction and milk ejection.

• Antidiuretic hormone (ADH): Regulates water balance by increasing water reabsorption in the kidneys.

• Is the posterior lobe of the pituitary gland a true endocrine gland? No, it stores and releases hormones produced by the hypothalamus.

• Parathyroid gland and hormone mechanism: Parathyroid hormone (PTH) regulates calcium levels in the blood by acting on bones, kidneys, and intestines.

• Mineralocorticoid (aldosterone): A steroid hormone produced by the adrenal cortex that regulates sodium and potassium balance.

Example:

ADH deficiency leads to diabetes insipidus, characterized by excessive urination and thirst.

Special Senses

Introduction to Special Senses

Special senses include vision, hearing, taste, and equilibrium. These senses rely on specialized organs and neural pathways to process external stimuli.

• Follicle-stimulating hormone (FSH): Essential for reproductive function; deficiency can lead to infertility.

• Cholesterol: Precursor for steroid hormone synthesis.

• Insulin and Glucagon: Regulate blood glucose levels.

• Pineal gland and melatonin: Regulates circadian rhythms and sleep-wake cycles.

• Growth hormone: Stimulates growth and cell reproduction.

• Thyroid hormone: Regulates metabolism.

• Role of ACTH, TSH, FSH, LH: Tropic hormones that stimulate other endocrine glands.

• Extrinsic eye muscles: Control eye movement; innervated by cranial nerves III, IV, and VI.

• Ceruminous glands: Produce earwax (cerumen) for protection.

• Primary function of cerumen: Protects the ear canal from dust, microorganisms, and water.

• Tinnitus, vertigo, and gradual hearing loss: Symptoms of inner ear disorders such as Meniere's disease.

• Blind spot of the eye: The optic disc, where the optic nerve exits the retina; lacks photoreceptors.

• Visual pathway: Retina → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus → Visual cortex.

• Transplantation of tissues: Corneas can be transplanted without rejection due to lack of blood vessels and immune privilege.

• Middle ear and inner ear: Structures involved in hearing and balance.

• Myopia (nearsightedness): Light focuses in front of the retina; distant objects appear blurry.

• Hyperopia (farsightedness): Light focuses behind the retina; close objects appear blurry.

• Presbyopia: Age-related loss of lens elasticity, leading to difficulty focusing on close objects.

• Bitter taste: Elicited by specific taste receptors on the tongue.

• Cochlea: Spiral-shaped organ in the inner ear responsible for hearing.

• Semicircular canals: Detect rotational movement and contribute to balance.

• Tympanic membrane: Eardrum; vibrates in response to sound waves.

• Vestibule: Central part of the bony labyrinth in the inner ear; involved in balance.

• Structure regulating light to visual receptors: The iris controls the amount of light entering the eye.

• Order of structures for light passage: Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina.

• Lens elasticity and presbyopia: Decreased elasticity leads to presbyopia.

• Function of the iris: Regulates pupil size and light entry.

• Color blindness: Results from absence or malfunction of cone cells; most commonly red-green color blindness.

• Equalization of pressure in middle ear: Eustachian tube connects middle ear to nasopharynx.

• Eye structures: Conjunctiva (mucous membrane), cornea (transparent front), sclera (white outer layer).

• Pilocarpine eye drops: Used to treat glaucoma by increasing outflow of aqueous humor.

• Sound perception: Sound is processed in the temporal lobe of the cerebral cortex.

• Retinal sensitivity and visual acuity: Bright light decreases sensitivity but increases acuity.

• Intraocular pressure: Elevated pressure can lead to glaucoma and optic nerve damage.

• Presbyopia and aging: Age-related changes in the lens require corrective lenses.

• Roller coaster sensations: Dizziness and vertigo originate from the vestibular apparatus in the inner ear.

Example:

Presbyopia is commonly corrected with reading glasses, which compensate for the loss of lens elasticity.

Table: Comparison of Immunity Types

Table: Hormone Mechanisms

Key Equations

• Second Messenger System (cAMP):

• Osmotic Regulation by ADH:

Additional info: Some explanations and examples were expanded for clarity and completeness.