Endocrine and Special Senses Study Guide PDF

Overview of the Endocrine System ​ Definition: Composed of glands that secrete hormones directly into the bloodstream to act on specific target tissues. ​ Hormones: Chemical messengers that regulate body processes. ○​ Types: ​ Amino acid-based hormones (e.g., p...

Overview of the Endocrine System ​ Definition: Composed of glands that secrete hormones directly into the bloodstream to act on specific target tissues. ​ Hormones: Chemical messengers that regulate body processes. ○​ Types: ​ Amino acid-based hormones (e.g., protein hormones). ​ Steroids (derived from cholesterol). ​ Basic Hormone Action: ○​ Travel through blood, targeting specific cells with appropriate receptors. ○​ Hormones can have varied effects depending on the target tissue. Major Endocrine Glands & Hormones ​ Pineal Gland: Produces melatonin (regulates sleep-wake cycles). ​ Hypothalamus: Controls the pituitary gland, secreting, releasing and inhibiting hormones. ​ Pituitary Gland (Master Gland): ○​ Anterior Lobe: Produces 7 hormones: ​ Tropic hormones: TSH, ACTH, FSH, LH (stimulate other glands). ​ Non-tropic hormones: GH, PRL, MSH. ○​ Posterior Lobe: Stores and releases hypothalamic hormones: ​ Oxytocin: Uterine contractions and milk ejection. ​ ADH (vasopressin): Water retention by kidneys. ​ Thyroid Gland: Produces thyroid hormone (TH) (metabolic rate) and calcitonin (reduces blood calcium). ​ Parathyroid Glands: Secretes PTH (raises blood calcium levels). ​ Adrenal Glands: ○​ Adrenal Medulla: Produces epinephrine and norepinephrine (fight-or-flight response). ○​ Adrenal Cortex: Produces: ​ Mineralocorticoids (e.g., aldosterone for blood pressure regulation). ​ Glucocorticoids (e.g., cortisol for stress response). ​ Pancreas: ○​ Alpha cells: Produce glucagon (raises blood sugar). ○​ Beta cells: Produce insulin (lowers blood sugar). ​ Gonads: ○​ Testes: Produce testosterone (sperm production, male traits). ○​ Ovaries: Produce estrogen (female traits) and progesterone (uterine preparation for pregnancy). Mechanisms of Hormone Secretion 1.​ Humoral Stimuli: Triggered by changes in blood levels of ions/nutrients (e.g., low blood calcium → PTH release). 2.​ Neural Stimuli: Nerve fibers directly stimulate hormone release (e.g., adrenal medulla → epinephrine). 3.​ Hormonal Stimuli: Hormones stimulate other glands (e.g., hypothalamus → anterior pituitary → other glands). Additional Endocrine Structures ​ Heart: Produces ANP (lowers blood pressure). ​ Kidneys: Secrete renin (regulates blood pressure) and erythropoietin (stimulates red blood cell production). ​ Skin: Produces a precursor of vitamin D. ​ Placenta: Produces hormones to sustain pregnancy. Disorders ​ Pituitary Disorders: ○​ Gigantism: Excess GH in children. ○​ Dwarfism: Deficiency of GH. ​ Pancreatic Disorders: ○​ Diabetes Mellitus: ​ Type 1: Insufficient insulin due to autoimmune destruction of beta cells. ​ Type 2: Insulin resistance, managed by diet and exercise. Special Senses The human body has five special senses: taste, smell, sight, hearing, and balance, along with the general sense of touch. Below is a concise breakdown for easy understanding. 1. Taste (Gustation) ​ Receptors: Chemoreceptors respond to food dissolved in saliva. ​ Taste Buds: Located primarily on the tongue within: 1.​ Fungiform Papillae (tip of tongue)  2.​ Circumvallate Papillae (back of tongue) ​ Cell Types in Taste Buds: 1.​ Gustatory Epithelial Cells (taste cells) 2.​ Basal Epithelial Cells (supporting cells) 3.​ Replaced every 7–10 days. ​ Five Basic Tastes: Sweet, sour, salty, bitter, umami. ​ Pathway: 1.​ Taste information travels via cranial nerves VII (Facial) and IX (Glossopharyngeal). 2.​ Synapse in the medulla → thalamus → cerebral cortex. 2. Smell (Olfaction) ​ Receptors: Chemoreceptors in the olfactory epithelium (pseudostratified columnar tissue). ​ Cell Types: ○​ Olfactory Sensory Neurons ○​ Supporting Epithelial Cells ○​ Olfactory Stem Cells ​ Olfactory Cilia: Capture and dissolve odor molecules in mucus. ​ Pathway: Olfactory nerve → cribriform plate → olfactory bulb → cerebral cortex and limbic system. 3. Sight (Vision) ​ Dominant Sense: ○​ 70% of sensory receptors are in the eyes. ○​ 40% of the cerebral cortex processes visual information. Anatomy of the Eye ​ Outer Layer (Fibrous Layer): ○​ Sclera: White, tough connective tissue; provides shape and anchors muscles. ○​ Cornea: Transparent, anterior part; focuses light. ​ Middle Layer (Vascular Layer): ○​ Iris: Colored part; controls pupil size (light adjustment). ​ Sphincter Pupillae: Constricts pupil. ​ Dilator Pupillae: Enlarges pupil. ○​ Choroid: Darkly pigmented to prevent light scattering.  ​ Inner Layer (Retina): ○​ Two layers: ​ Pigmented Layer: Absorbs excess light. ​ Neural Layer: Contains: ​ Photoreceptors: ​ Rods: Vision in dim light. ​ Cones: Color vision and clarity. ​ Bipolar Cells: Relay signals. ​ Ganglion Cells: Generate nerve impulses. ○​ Macula Lutea: High cone density for sharp vision. ○​ Fovea Centralis: Center of sharpest visual focus. Internal Fluids ​ Vitreous Humor (Posterior Segment): ○​ Jellylike; supports eye shape, transmits light. ​ Aqueous Humor (Anterior Segment): ○​ Continuously renewed; provides nutrients to lens and cornea. 4. Hearing and Balance Hearing and balance rely on the inner ear: ​ Hearing: Vibrations converted into neural signals by the cochlea. ​ Balance: Maintained by the vestibular system (semicircular canals and vestibule).