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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
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