Homeostasis
Sensors, a control center and effectors hold a regulated variable near a set point, mostly by negative feedback.
Your body holds dozens of variables inside narrow ranges: core temperature, blood pressure, blood glucose, the pH and salt content of your blood. Each one is held the same way. A sensory receptor detects the variable, a control center compares it with a set point, and effectors push it back. Because the correction opposes the change, this is negative feedback, and it is how almost all regulation works.
Watch for it everywhere. When you stand up quickly and blood pools in your legs, pressure sensors in your arteries fire less, your brainstem raises heart rate and tightens arterioles, and your blood pressure recovers within seconds. The same loop, with different parts, runs your thermostat, your breathing and your kidneys. Positive feedback, which amplifies a change, is rare and always has an end point, such as childbirth or a clot sealing a wound.
Where it shows up
Chemistry and physics for physiology
Signals, repair and control
Integumentary system
- Functions of the skin
- Burns, wounds and skin repair
Bone tissue
- Bone remodeling and fracture repair
- Bone and blood calcium
Nerves, reflexes and pathways
- Reflexes
The autonomic nervous system
- Autonomic control and visceral reflexes
The endocrine system
- Hypothalamus and pituitary gland
- Thyroid and parathyroid glands
- The pancreas and blood glucose
- Adrenal glands
Blood
- Blood composition and functions
- Red blood cells and hemoglobin
- Hemostasis and clotting
The cardiovascular system
- Cardiac output and its control
- Short-term blood pressure regulation
- Long-term blood pressure regulation
- Hypertension, heart failure and shock
Lymphatic and immune systems
- Innate immunity
- Immune disorders
The respiratory system
- Carbon dioxide transport
- Control of breathing
Metabolism and nutrition
- Fed and fasting states
- Energy balance and body temperature
The urinary system
- Glomerular filtration
- Concentrating the urine
- Urine, clearance and kidney hormones
Fluid, electrolyte and acid–base balance
- Body fluid compartments and water balance
- Electrolyte balance
- Regulating acid–base balance
- Acid–base disorders and compensation
The reproductive system
- Spermatogenesis and male hormones
- Hormonal control of the ovarian and uterine cycles
Development and inheritance
- Maternal changes during pregnancy
- Labor and birth
- Newborn adjustments and lactation
- Aging across the body