Some Medical & Applied Sciences Group 1 – cardiology, cytology, dermatology Group 2 – endocrinology, epidemiology, gastroenterology Group 3 – geriatrics, gerontology, gynecology Group 4 – hematology, immunology, neonatology Group 5 – nephrology, neurology, obstetrics Group 6 – oncology, opthalmology, orthopedics Group 7 – pathology, pediatrics, pharmacology Group 8 – podiatry, psychiatry, radiology Group 9 – otolaryngology, toxicology, urology Mrs. Guzman - histology

Homeostasis All homeostatic control mechanisms have at least three components: Receptor –Sensor Control Center –Determines Set Point Effector –Output (organ)

Homeostasis Components of Feedback Mechanisms: 1. Stimulus: The change from ideal or resting conditions. 2. Receptor: The cells or tissue which detects the change due to the stimulus. 3. Relay: The transmission of the message, via nerves or hormones or both, to the effector. 4. Effector: The cells or tissue, usually a gland or muscles, which cause the response to happen. 5. Response: An action, at cell, tissue or whole organism level which would not have occurred in the absence of the stimulus. 6. Feedback: The consequence of the response on the stimulus. May be positive or negative.

Homeostasis Components of Feedback Mechanisms: 1. Stimulus: The change from ideal or resting conditions. 2. Receptor: The cells or tissue which detects the change due to the stimulus. 3. Relay: The transmission of the message, via nerves or hormones or both, to theeffector. 4. Effector: The cells or tissue, usually a gland or muscles, which cause the response to happen. 5. Response: An action, at cell, tissue or whole organism level which would not have occurred in the absence of the stimulus. 6. Feedback: The consequence of the response on the stimulus. May be positive or negative.

A feedback mechanism starts with a Stimulus Receptor Response Feedback

Homeostasis Feedback Mechanisms: Negative Positive

Negative Feedback Most common homeostatic feedback mechanism The response diminishes the original stimulus Reduces the output or activity of any organ or system back to its normal range of functioning.

Negative Feedback Examples: Body Temperature –Nervous System Blood Calcium Levels (Normal = 2.2-2.6 mmol/L) –Endocrine System Blood Pressure: Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both are the effectors. The heart rate would decrease as the blood vessels increase in diameter (or vasodilation). This change would result in the blood pressure to fall back to its normal range.

Positive Feedback Rare homeostatic feedback mechanism The response enhances the original stimulus

Positive Feedback Examples: Hemorrhage Childbirth (release oxytocin to intensify the contractions that take place during childbirth) Lactation Childbirth Positive Feedback Video

Choose the true statement regarding positive feedback It occurs when the heart rate increases during exercise. It reinforces or strengthens the original stimulus. Positive feedback mechanisms are usually of long duration. It produces dilation of surface blood vessels when a person exercises on a hot day.

Homeostatic Imbalances in the Body 1. Integumentary System –Burns, Cutaneous Legions (Cold Sores, Impetigo, Psoriasis), Skin Cancer 2. Skeletal System –Rickets, Abnormal Spinal Curvatures (Scoliosis, Kyphosis, Lordosis),Osteoporosis

Cutaneous Legion Rickets

Homeostatic Imbalances in the Body 3. Muscular System –Muscular Dystrophy, Myasthenia Gravis 4. Nervous System –Multiple Sclerosis, Huntington’s Disease, Parkinson’s Disease, Alzheimer’s Disease

Myasthenia Gravis Multiple Sclerosis

Homeostatic Imbalances in the Body 5. Endocrine System –Goiter, Graves’ Disease, Pituitary Dwarfism, Infertility 6. Cardiovascular System –Pericarditis, Valvular Stenosis, Varicose Veins, Atherosclerosis

Goiter Varicose Veins

Homeostatic Imbalances in the Body 7. Lymphatic System –Allergies, Immunodeficiencies (SCID, AIDS), Autoimmune Disease (Lupus, Rheumatoid Arthritis, etc) 8. Respiratory System –Sinusitis, Tonsillitis, Pleurisy, Emphysema, Bronchitis, Cystic Fibrosis

Rheumatoid Arthritis Emphysema

Homeostatic Imbalances in the Body 9. Digestive System –Gallstones, Heartburn, Gastric Ulcers 10. Urinary System –Kidney Stones, Addison’s Disease, Polycystic Kidney Disease

Gastric Ulcer Kidney Stones

Kidney Stone Removal Video

Homeostatic Imbalances in the Body 11. Reproductive System –Pelvic Inflammatory Disease, Cervical Cancer, Testicular Cancer