BIOL 1103 Unit 8-Homneostasis

What is homeostasis?

The maintenance of a steady internal state in the body despite fluctuations in the external environment.

What is the internal environment of the body?

The extracellular fluid (ECF), which includes blood plasma, interstitial fluid, and lymph fluid.

What is extracellular fluid (ECF)?

Fluid outside cells, including blood plasma, interstitial fluid, and lymph fluid.

What is the optimum temperature for homeostasis?

37.5 ºC.

Which systems regulate homeostasis?

The nervous and endocrine systems, acting together or independently.

How does the nervous system regulate homeostasis?

It detects changes and sends nerve impulses to counteract disruption.

How does the endocrine system regulate homeostasis?

It secretes hormones to regulate internal conditions, usually working more slowly than nerves.

What is a feedback loop?

A mechanism to deal with stress in order to regain homeostasis through monitoring, control, and effectors.

What are the five parts of a feedback loop?

Input (stimulus), Sensor (receptors), Control centre (often hypothalamus), Effector (target tissues), and Output (resulting change).

What is negative feedback?

A process where a change initiates a response that opposes it, stabilizing the system at a set point.

Example of negative feedback in blood pressure regulation?

Baroreceptors detect increased blood pressure → brain processes signal → heart slows down and vessels vasodilate → blood pressure decreases.

What happens when body temperature gets too cold?

Receptors detect cold → hypothalamus activates → shivering, vasoconstriction, hormone release → body warms up.

What happens when body temperature gets too hot?

Receptors detect heat → hypothalamus activates → sweating, vasodilation, fewer hormones, decreased muscle tone → body cools down.

What is positive feedback?

A process where the output amplifies the input, rare in normal physiology.

Examples of positive feedback?

Childbirth contractions, urination, breastfeeding, blood clotting.

How does positive feedback work in childbirth?

Baby’s head stretches cervix → receptors send signals → brain releases oxytocin → stronger contractions → more stretching until delivery.