Midterm 2 Study Guide: Special Senses, Endocrine System, and Blood

Special Senses

Receptors and Locations

The special senses include vision, hearing, taste, smell, and equilibrium. 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.

• Taste: Chemoreceptors in taste buds on the tongue.

• Smell: Olfactory receptors in the nasal epithelium.

• Equilibrium: Mechanoreceptors in the vestibular apparatus of the inner ear.

General Function: Special senses detect specific stimuli and transmit information to the brain for interpretation.

• Example: Light stimulates photoreceptors, which send signals to the visual cortex for image processing.

The Endocrine System

Hormone Action and Enzyme Amplification

Hormones regulate physiological processes by binding to target cells. Enzyme amplification refers to the process where a single hormone molecule triggers the activation of many enzymes, amplifying the cellular response.

• Target Cell Specificity: Only cells with specific receptors respond to a given hormone.

• Example: Insulin acts on cells with insulin receptors to promote glucose uptake.

Steroid vs. Protein Hormones

• Steroid hormones: Lipid-soluble, derived from cholesterol (e.g., cortisol, estrogen).

• Protein hormones: Water-soluble, composed of amino acids (e.g., insulin, growth hormone).

Fast Acting vs. Slow Acting Hormones

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

• Slow acting: Usually 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 metabolism, growth, reproduction, etc.

• Regulation: Hormone release is stimulated or suppressed 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; impaired growth and mental development.

Major Metabolic Hormone

• Thyroid hormone (T3/T4): Regulates basal metabolic rate.

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 stimulates insulin release.

• Stimuli for Glucagon: Low blood glucose stimulates glucagon release.

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

• DKA (Diabetic Ketoacidosis): Severe insulin deficiency; signs include fruity breath, rapid breathing, confusion.

Pituitary Glands

• Anterior pituitary: True endocrine gland; produces hormones.

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

Hormones Increasing Blood Glucose

• Glucagon, Growth Hormone (GH), Epinephrine, Glucocorticoids: All increase blood glucose levels.

Key Terms

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

• Glycogenolysis: Breakdown of glycogen to glucose.

Thymus Importance

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

Adrenal Medulla and Stress Response

• Adrenal medulla: Releases epinephrine and norepinephrine during stress.

General Adaptation Syndrome (GAS)

• Stages: Alarm, Resistance, Exhaustion.

• Hormones: Cortisol, epinephrine, and others mediate the stress response.

Blood

Properties and Components

Blood is a connective tissue composed of plasma and formed elements (cells).

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

• Formed elements: Erythrocytes (RBCs), leukocytes (WBCs), platelets.

Functions of Blood

• Transport: Oxygen, carbon dioxide, nutrients, hormones, waste.

• Regulation: pH, temperature, fluid balance.

• Protection: Immune response, clotting.

• 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 stimulates erythropoietin, increasing RBC production.

Erythropoiesis and Reticulocyte Count

• Erythropoiesis: Formation of RBCs from stem cells in bone marrow.

• Reticulocyte count: Indicates rate of RBC production; useful in diagnosing anemia.

Anemia

• Definition: Reduced oxygen-carrying capacity of blood.

• Causes: Blood loss, iron deficiency, vitamin B12 deficiency, genetic disorders (e.g., sickle cell anemia).

• Examples: Iron-deficiency anemia, pernicious anemia, hemolytic anemia.

Polycythemia

• Definition: Excess RBCs; increases blood viscosity.

• Danger: Risk of clotting, stroke, heart failure.

Blood Types and Compatibility

Blood types are determined by antigens on RBCs. Compatibility is crucial for transfusions.

Blood Type	Can Receive From	Can Donate To
A	A, O	A, AB
B	B, O	B, AB
AB	A, B, AB, O	AB
O	O	A, B, AB, O

Erythroblastosis Fetalis and Rh Status

• Erythroblastosis fetalis: Hemolytic disease of the newborn due to Rh incompatibility.

• Rh-negative mother: If exposed to Rh-positive fetal blood, may produce antibodies that attack fetal RBCs in subsequent pregnancies.

Leukocytes (White Blood Cells)

• Granulocytes: Contain granules; include neutrophils, eosinophils, basophils.

• Agranulocytes: Lack granules; include lymphocytes, monocytes.

• Functions: Immune defense, phagocytosis, antibody production.

Leukocyte	Type	Function
Neutrophil	Granulocyte	Phagocytosis of bacteria
Eosinophil	Granulocyte	Combat parasites, allergies
Basophil	Granulocyte	Release histamine, inflammation
Lymphocyte	Agranulocyte	Antibody production, immune response
Monocyte	Agranulocyte	Phagocytosis, become macrophages

WBC Range and Disorders

• Normal WBC range: 4,000–11,000 cells/µL.

• Leukopenia: Low WBC count; may indicate infection or bone marrow disorder.

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

• Leukocyte disorders: Include leukemia, lymphoma, infectious mononucleosis.

Hematocrit Values

• Normal values: Males: 42–54%; Females: 38–46%.

Additional info: Academic context and examples were added to expand brief study guide points into full explanations.