Homeostasis, Coordination and Response in Humans

Thirty vocabulary flashcards summarizing key terms related to homeostasis, endocrine and nervous control, and associated physiological processes.

Homeostasis

Maintenance of a relatively constant internal environment so that metabolic processes occur at optimal rates.

Negative Feedback

A homeostatic mechanism that counteracts changes in the internal environment and restores conditions toward the set norm.

Hormone

A chemical substance produced by a gland, carried by the blood, that alters the activity of specific target organs and is destroyed by the liver.

Endocrine Gland

A ductless gland that secretes hormones directly into the bloodstream.

Exocrine Gland

A gland that produces and secretes substances through ducts to an external or internal surface (e.g., salivary or sweat glands).

Islets of Langerhans

Clusters of endocrine cells in the pancreas that secrete the hormones insulin and glucagon into the bloodstream.

Antidiuretic Hormone (ADH)

Hormone produced by the hypothalamus and released by the pituitary that increases water reabsorption in kidney collecting ducts.

Osmoregulation

Control of water and solute concentrations in the blood to maintain constant water potential.

Insulin

Pancreatic hormone that lowers blood glucose by increasing cellular uptake and conversion of excess glucose to glycogen in liver and muscles.

Glucagon

Pancreatic hormone that raises blood glucose by stimulating conversion of stored glycogen to glucose in the liver.

Diabetes Mellitus

Chronic condition characterized by persistently high blood glucose due to insulin insufficiency or resistance.

Type 1 Diabetes

Autoimmune destruction of insulin-producing cells leading to insufficient insulin; usually early onset and requires insulin injections.

Type 2 Diabetes

Condition in which target cells become resistant to insulin; often associated with obesity and sedentary lifestyle and managed by diet, exercise, and medication.

Sensitivity

The ability of an organism to detect and respond to changes in its environment.

Central Nervous System (CNS)

Part of the nervous system consisting of the brain and spinal cord that coordinates and regulates bodily functions.

Peripheral Nervous System (PNS)

All nerves outside the CNS, including cranial and spinal nerves, that connect the CNS to the rest of the body.

Neurone

A nerve cell composed of a cell body, dendrites, and an axon that transmits nerve impulses.

Synapse

A small gap between neurones where nerve impulses are transmitted via neurotransmitters.

Reflex Action

An immediate, involuntary response to a specific stimulus without conscious control.

Sensory Neurone

Neurone that transmits nerve impulses from receptors to the central nervous system.

Relay Neurone

Interneuron located in the CNS that passes impulses from sensory to motor neurones.

Motor Neurone

Neurone that transmits nerve impulses from the central nervous system to effectors such as muscles or glands.

Vasodilation

Widening of arterioles near the skin surface to increase blood flow and enhance heat loss.

Vasoconstriction

Narrowing of arterioles near the skin surface to reduce blood flow and conserve body heat.

Accommodation (Eye)

Adjustment of lens thickness by ciliary muscles to focus near or distant objects on the retina.

Pupil Reflex

Cranial reflex where pupil size changes in response to light intensity to regulate light entry into the eye.

Photoreceptors

Light-sensitive cells (rods and cones) in the retina that generate nerve impulses when stimulated by light.

Thermoregulation

Maintenance of a constant body temperature through nervous mechanisms such as sweating, shivering, and blood flow adjustments.

Osmoreceptors

Receptors in the hypothalamus that detect changes in the water potential of blood plasma.

Neurotransmitter

Chemical released at a synapse that carries a nerve impulse across the gap to the next neurone.