5 Coordination and regulation:endocrine systems

Death at sea

2207 people left the UK, 1502 people died in a freezing ocean

• If a body deviates too far from the normal steady state of a variable, death can occur.

• Tissue fluid and plasma form the internal environment of body cells.

• The internal environment is relatively stable.• Fluids located outside cells are termed

extracellular.• Fluid located within cells is intracellular.• Exchange of substances occurs between the

various fluids of the body.

!!! Plasma- special form of ECF surrounding RBCs in vascular system

BODY

cell

Intracellular fluid- cytosol

Extracellular fluid

cell

cell

What variables are subject to homeostasis?

• nutrients • blood volume• temperature • blood pressure• water • ions, such as Na+,

Ca+, Cl−

• carbon dioxide• pH (hydrogen ion

concentration) • red blood cells.• oxygen

Read pages 137/8.

• Homeostasis is the condition of a relatively stable internal environment.

• Homeostasis is essential for cell functioning.• Homeostasis can be disrupted by agents such

as disease and trauma.• Most body systems play various roles in

homeostasis.• The hormone and nervous systems are the

two systems that coordinate all other systems of the body.

• Do QC. 1-8

Homeostasis: hormones in action

• All negative feedback systems involve sensors that monitor the state of a particular variable and compare that state with optimal levels.

• All negative feedback systems involve effectors that respond to messages from sensors and act to maintain a variable within its optimal limits.

• Although the majority of hormone systems operate by negative feedback, positive feedback systems do exist.

• Read. pp139/44 QC 9-12

Hormones as cell communicators