Special Senses

Receptors and Their Locations

The special senses include vision, hearing, equilibrium, taste, and smell. Each sense relies on specific receptors located in specialized organs:

• Vision: Photoreceptors (rods and cones) in the retina of the eye.

• Hearing: Mechanoreceptors (hair cells) in the cochlea of the inner ear.

• Equilibrium: Mechanoreceptors in the vestibular apparatus (semicircular canals, utricle, saccule) of the inner ear.

• Taste: Chemoreceptors in taste buds on the tongue.

• Smell: Chemoreceptors in the olfactory epithelium of the nasal cavity.

Function of Special Senses

Each special sense functions by converting environmental stimuli into electrical signals interpreted by the brain:

• Vision: Light is focused onto the retina, where photoreceptors generate action potentials sent to the brain via the optic nerve.

• Hearing: Sound waves vibrate the tympanic membrane and ossicles, stimulating hair cells in the cochlea.

• Equilibrium: Movement of fluid in the vestibular apparatus stimulates hair cells, providing information about balance and spatial orientation.

• Taste: Chemicals in food bind to taste receptors, generating nerve impulses.

• Smell: Odor molecules bind to olfactory receptors, triggering action potentials.

Additional info:

Refer to Quiz 2 study guide for detailed items on each special sense.

Endocrine System

Enzyme Amplification in Hormone Action

Enzyme amplification refers to the process by which a single hormone molecule can trigger the production of many enzyme molecules, greatly magnifying the hormone's effect.

• Example: One hormone binding to a receptor can activate a cascade, resulting in the synthesis of thousands of product molecules.

Hormone Interaction with Target Cells

Hormones interact with specific target cells that possess receptors for that hormone. This is known as target cell specificity.

• Example: Insulin acts only on cells with insulin receptors.

Steroid vs. Protein Hormones

• Steroid hormones: Lipid-soluble, derived from cholesterol, act on intracellular receptors, often affecting gene expression.

• Protein hormones: Water-soluble, act on cell surface receptors, often using second messenger systems.

Fast Acting vs. Slow Acting Hormones

• Fast acting: Typically protein hormones, act via second messengers (e.g., epinephrine).

• Slow acting: Steroid hormones, act via gene transcription (e.g., cortisol).

Hormone Details

• Target cells/tissues: Each hormone acts on specific cells or tissues.

• Functions: Hormones regulate growth, metabolism, reproduction, etc.

• Stimulation/Suppression: Hormone release is regulated by feedback mechanisms.

• Imbalances: Can cause disorders (e.g., hypothyroidism, diabetes).

Pituitary Dwarfism vs. Cretinism

• Pituitary dwarfism: Caused by growth hormone deficiency; normal body proportions.

• Cretinism: Caused by thyroid hormone deficiency; stunted growth and mental retardation.

Major Metabolic Hormone

• Thyroid hormone (T3/T4): Regulates metabolism.

Diabetes Mellitus

• Type 1: Autoimmune destruction of beta cells; insulin deficiency.

• Type 2: Insulin resistance; often associated with obesity.

• Glycosuria/Glucosuria: Presence of glucose in urine.

• Polyuria: Excessive urination.

• Polydipsia: Excessive thirst.

• Ketosis: Accumulation of ketone bodies due to fat metabolism.

• Stimuli for insulin: High blood glucose.

• Stimuli for glucagon: Low blood glucose.

• Complications: Cardiovascular disease, neuropathy, nephropathy, retinopathy.

• DKA (Diabetic Ketoacidosis): Severe hyperglycemia, acidosis, dehydration; signs include fruity breath, rapid breathing.

Anterior vs. Posterior Pituitary

• Anterior pituitary: True endocrine gland; produces hormones.

• Posterior pituitary: Not a true endocrine gland; stores and releases hormones made in the hypothalamus.

Hormones That Increase Blood Glucose

• Glucagon, Growth Hormone (GH), Epinephrine, Glucocorticoids.

Gluconeogenesis and Glycogenolysis

• Gluconeogenesis: Formation of glucose from non-carbohydrate sources.

• Glycogenolysis: Breakdown of glycogen to glucose.

Thymus Importance

• Site of T cell maturation; essential for immune function.

Short-term vs. Long-term Stress Responses

• Short-term: Mediated by adrenal medulla (epinephrine/norepinephrine); increases heart rate, blood pressure.

• Long-term: Mediated by adrenal cortex (cortisol); increases blood glucose, suppresses immune system.

Adrenal Medulla in Stress Response

• Releases catecholamines (epinephrine, norepinephrine) for fight-or-flight response.

General Adaptation Syndrome (GAS)

• Alarm: Immediate response to stress; adrenal medulla releases catecholamines.

• Resistance: Adrenal cortex releases cortisol; body adapts to stress.

• Exhaustion: Prolonged stress depletes resources; risk of illness.

Blood

Properties and Components of Blood

• Blood: Connective tissue composed of plasma and formed elements (erythrocytes, leukocytes, platelets).

• Plasma: Water, proteins (albumin, globulins, fibrinogen), nutrients, hormones, waste products.

Functions of Blood

• Transport of gases, nutrients, hormones, waste.

• Regulation of pH, temperature, fluid balance.

• Protection against infection and blood loss.

• Hemoglobin: Binds oxygen and carbon dioxide.

Erythropoietin and RBC Production

• Erythropoietin: Hormone produced by kidneys; stimulates RBC production.

• Stimulus: Low oxygen levels (hypoxia).

• Altitude: Increased altitude lowers oxygen, stimulating erythropoietin and RBC production.

Anemia

• Anemia: Reduced oxygen-carrying capacity of blood.

• Causes: Blood loss, iron deficiency, vitamin B12 deficiency, sickle cell disease.

Polycythemia

• Polycythemia: Excess RBCs; increases blood viscosity, risk of clotting.

Blood Types

• A, B, AB, O; determined by antigens on RBCs.

Erythroblastosis Fetalis

• Occurs when Rh-negative mother carries Rh-positive fetus; maternal antibodies attack fetal RBCs.

Leukocytes

• Granulocytes: Neutrophils, eosinophils, basophils; contain granules.

• Agranulocytes: Lymphocytes, monocytes; lack granules.

• Functions: Defense against pathogens.

Normal WBC Range and Disorders

• Normal WBC: 4,000–11,000/µL.

• Leukopenia: Low WBC count; risk of infection.

• Leukocytosis: High WBC count; may indicate infection or leukemia.

Hematocrit Values

Additional info:

Review blood case study and postlab activity from Lab 8 for applied understanding.