Homeostasis

What is Homeostasis? It’s about balance! Homeostasis is the physiological state of the body in which internal conditions are kept within a range that is suitable for life processes. The human body can deal with a range of environmental stimuli. Humans operate best at : 37°C body temp 0.1% blood sugar Blood pH of 7.35

How is Balance Maintained? There are several body systems involved in the maintenance of homeostasis: Nervous System Endocrine System Musculoskeletal System Integumentary System Excretory System Reproductive System

How is Balance Maintained? Homeostatic mechanisms involve the monitoring of internal and external conditions, as well as the changes the body undergoes to maintain balance. Four components of homeostatic systems: Sensor Integrator (control centre) Effector (Regulator) Response Example: Arterial stretch receptors (sensor) detect pressure changes (stimulus) in arteries which signals brain . The brain (integrator) then relays information to adjust the strength of the heart’s contractions (effector). Blood pressure will increase or decrease depending on the initial pressure (response).

Negative Feedback Negative feedback systems are mechanisms that restore conditions to their original state. Classic example: Household thermostat Called negative feedback because a change in variable being monitored triggers control mechanism to counteract further changes.

Negative feedback

Positive Feedback Less common in the body and they reinforce changes. Example: Birthing process Progesterone drop initiates contractions Contractions release oxytocin, which causes stronger contractions

Positive feedback

Thermoregulation Maintenance of body temperature. Endotherms (like us mammals) maintain constant body temperatures despite surroundings. Hypothalamus (in brain) is our thermostat (monitor).

Case Study: TEACUP THE FROZEN CAT!

Response to Heat Brain detects a rise in body temp. Hypothalamus sends signal to sweat glands to start sweating and blood vessels to dilate. Evaporation cools body and more blood flows to skin where it loses heat.

Response to Cold Hypothalamus sends message to organs and tissues to increase temperature. Blood vessels contract. Smooth muscles around hair follicles contract (goose bumps) to trap air near skin. Shivering to generate heat.

Prolonged Cold Exposure Increase in brown fat (often found in babies). Brown fat really efficient at generating heat.

Interesting thermoregulation Exercise Endotherms - Some organisms exercise to maintain core body temperatures eg. Honey bees Fur Distribution – Dogs have uneven distribution of fur and curl up when cold to cover exposed surfaces Elephants have big ears! Panting