. 2015 Dec;39(4):259–266. doi: 10.1152/advan.00107.2015

Table 1.

Homeostatically regulated variables typically found in undergraduate human physiology textbooks

Regulated Variable	Normal Range or Value	Sensor (Location If Known)	Control Center (Location)	Effectors	Effector Response
Arterial Po₂	75–100 mmHg	Chemosensors (carotid bodies and aortic body)	Brain stem	Diaphragm and respiratory muscles	Change breathing frequency and tidal volume
Arterial Pco₂	34–45 mmHg	Chemosensors (carotid bodies, aortic body, and the medulla)	Brain stem	Diaphragm and respiratory muscles	Change breathing frequency and tidal volume
K⁺ concentration	3.5–5.0 meq/l	Chemosensors (adrenal cortex)	Adrenal cortex	Kidneys	Alter reabsorption/secretion of K⁺
Ca²⁺ concentration	4.3–5.3 meq/l (ionized)	Chemosensors (parathyroid gland)	Parathyroid gland	Bone, kidney, and intestine	Alter reabsorption of Ca²⁺, alter resorption/building of bone, and alter absorption of Ca²⁺
H⁺ concentration (pH)	35–45 nM (pH 7.35–7.45)	Chemosensors (carotid bodies, aortic body, and floor of the fourth ventricle)	Brain stem	Diaphragm and respiratory muscles	Change breathing frequency and tidal volume and change secretion/reabsorption of H⁺/bicarbonate ions
H⁺ concentration (pH)	35–45 nM (pH 7.35–7.45)	Chemosensors (kidney)	Kidney	Kidney
Blood glucose concentration	70–110 mg/dl	Fed state: chemosensors (pancreas)	Pancreas	Liver, adipose tissue, and skeletal muscle	Alter storage/metabolism/release of glucose and its related compounds
Blood glucose concentration	70–110 mg/dl	Fasting state: chemosensors (hypothalamus, pancreas)	Hypothalamus	Liver, adipose tissue, and skeletal muscle
Core body temperature	98.6°F	Thermosensors (hypothalamus, skin)	Hypothalamus	Blood vessels and sweat glands in the skin as well as skeletal muscles	Change peripheral resistance, rate of sweat secretion rate, and shivering
Core body temperature	98.6°F	Thermosensors (hypothalamus, skin)	Hypothalamus		Alter heat gains/losses
Mean arterial pressure	93 mmHg	Mechanosensors (carotid sinus and aortic arch)	Medulla	Heart and blood vessels	Alter heart rate, peripheral resistance, inotropic state of the heart, and venomotor tone
Blood volume (effective circulating volume)	5 liters	Mechanosensors	Medulla	Heart	Alter heart rate, peripheral resistance, and inotropic state of the heart
		(Blood vessels: carotid bodies)	Hypothalamus	Blood vessels	Alter Na⁺ and water reabsorption
		(Heart: atria and ventricle)	Atria	Kidneys	Alter water absorption
		(Kidney: juxtaglomerular apparatus and renal afferent arterioles)	Kidney	Intestine
Blood osmolality	280–296 mosM/kg	Osmosensors (hypothalamus)	Hypothalamus	Kidneys	Alter water reabsorption

This table includes commonly found components of control systems involved in physiological regulation (i.e., homeostasis). This is not meant to be an exhaustive list but rather reflect the current understanding of homeostatically regulated variables that undergraduate physiology students should understand and be able to apply to problems (e.g., making predictions about responses to perturbations or explaining symptoms of disease).