Homeostasis 04 September 2021 Key words Vasodilation Vasoconstriction

Homeostasis 04 September 2021 Key words: Vasodilation, Vasoconstriction, Negative feedback, Hypothalamus Starter: How would you feel in these areas & how would your body respond?

The big picture: “What do we need to control in the body? ” Learning outcomes ü To define what we mean by homeostasis. ü To explain some conditions in the body which need to be controlled. ü To analyse how body temperature is regulated in the body.

Homeostasis • Homeostasis is… keeping a constant internal environment • In order for our tissues and cells to function properly, the internal conditions of the body must be kept constant – what are the 4 main conditions we need to control?

Homeostasis • 4 main constants are – Water – Ion levels – Body Temperature – Glucose

Parts of the body involved: • Kidneys : – regulate water & mineral salts (ion) concentration • Skin : – regulate body temperature liver • Liver & pancreas : – regulate blood glucose level skin tissue cells kidney blood + pancreas

Task • Complete the graded sheet on thermoregulation and homeostasis. Support: Text books, phones (stick to GCSE websites) LO’s: ü To define what we mean by homeostasis. ü To explain some conditions in the body which need to be controlled. üTo analyse how body temperature is regulated in the body.

Stop! Time to self-assess Using the answer sheets I have put on your desk check your work. You should: Write a WWW/EBI on your sheet Instead of writing an INT use the answer sheets to improve your work: Time allowed: 7 mins

Homeostasis the maintenance of a stable internal environment • The conditions inside your body need to be kept steady, even when the external environment changes. • Examples: - Water levels - Core Body Temperature - Blood Glucose levels • Controlled by the nervous system and hormones (endocrine system) • Keeping a stable internal environment is really important because your cells need the right conditions in order to function properly.

Changes due to temperature To keep warm: - Shivering – uses energy - Releasing energy from food - Vasoconstriction - Hairs stand on end To keep cool: -Sweating which evaporates transferring heat to the environment -Vaso-dilation -Hairs lie flat Controlled by the hypothalamus in the brain

THERMOREGULATION How we keep (or maintain) a steady body temperature. Our body temperature is 37°C This is the temperature that our chemical reactions work best at. We must maintain it to prevent illnesses such as hypothermia and heat stroke. Being too hot or cold can lead to death…! It is negative feedback as it restores temperatures to normal- any change has a response which counteracts it

Cool Day Vasoconstriction Hot Day Vasodilation

Exam style question Explain how the body maintains a constant temperature (6 marks) 6 marks= 6 minutes

Peer assessment Regulated by the hypothalamus in the brain Reference to negative feedback Maintain 37°C Allow two marks for changes when the body is too hot e. g. hairs lie flat, vasodilation, sweating etc. • Allow two marks for changes when the body is too cold e. g. shivering, hairs standing on end, vasoconstriction etc. • •