Normal dietDrunk plenty

of water

Has been exercising but not drunk anything

Who’s urine? MATCH UP!

Learning Objective

To be able to explain how our bodies control water content.

Title - Homeostasis

Learning Outcome

• Homeostasis involves making sure that our bodies have the correct levels of 4 key things.

• Can you name two of them?

What is Homeostasis?

• Homeostasis makes sure our body has the correct levels of;

Temperature

Carbon dioxide

OxygenWater

Homeostasis involves maintaining a

constant environment in the body

In Out

BreathSweatFaecesUrine

Food and drinkWater made in respiration

B2 : How does the body control water balance?

Our bodies need a balanced water level to keep the internal concentration of our cells at the correct level

for them to work properly.

The kidneys

Kidneys do two main jobs:

1. Remove waste urea from the blood.

2. Keep a balance of other chemicals in the blood – including water.

How kidneys work

Filtering all small molecules from the blood.

Reabsorbing all of the glucose.

Reabsorbing as much salt as the body needs.

Reabsorbing as much water as the body needs.

Excreting the remaining urea, excess water and salt as urine, which is stored in the bladder.

Water balance

The concentration of blood plasma is monitored as it passes through the brain.

If the blood is too dilute then kidneys excrete more water in the urine.

If the blood is too concentrated then kidneys excrete less water in the urine.

The amount of water in the blood depends on: external temperature, exercise, intake of fluids and salts.

ADH and water balance.

The concentration of urine is controlled by a hormone called ADH (anti-diuretic hormone).

It is released into the bloodstream by the pituitary gland.

Normal blood concentration

Blood too concentrated – detected in brain

ADH secreted by pituitary gland

ADH causes kidneys to reabsorb more water to blood

Normal blood concentration

Blood too dilute – detected in brain

ADH not secreted by pituitary gland

kidneys reabsorb less water to blood

Water Balance

Outcomes: create a think board on homeostasis and water balance.

Which hormone controls water content in the body?

Where is it released from?

What 3 main things can effect the concentration of urine?

(D)

How do the Kidneys help keep water in the body balanced?

(C)

Draw a flow diagram of how the concentration of urine is controlled by a hormone

(B)

Explain in as much detail as possible (use as many science key words as you can) how Alcohol and Ecstasy affect ADH production

(A)

TITLE: Controlling Water Content

True/False Quiz!

• Your urine is always the same.• The pituitary gland monitors blood plasma.• Homeostasis maintains a constant internal environment.• The liver helps balance water and waste in the body.• Alcohol suppresses ADH production.• Ecstasy increases ADH production.

FALSE

TRUETRUE

FALSE

TRUE

TRUE

Dehydration

Drowning

Which is the odd one out?

bacteria

virus

fungus

B2 past EXAM questions!

• I will be round to mark them as you go ready to put into your progress folder.

ALL must do 2 exam questionsSOME will do more so can pick their highest grade for progress folderFEW will do all exam questions for a PRIZE!

Exam Question (hard)

3 marks – pick from the following

• number of bacteria after 2 hours is 12 800 (or 1.28 x 104), which is a sufficient number to cause food poisoning

• idea that if conditions were not optimum the actual number may be lower than this

• idea that not enough data/evidence/information, or would need to measure more things, to conclude that person will definitely get food poisoning

• idea of immune response against bacteria or toxins / acid in stomach destroying bacteria or toxins

Testing Urine• Draw the following table in your books neatly.

• Test the 3 urine samples for protein and for sugar using the equipment available.

• EXTENSION: explain in as much detail as possible what homeostasis is and how water content is controlled in the body.

Sample Protein Sugar

A

B

C

Drug Trials• Outcomes: create a Powerpoint on the use of drug trials

in medical science.

Include information on the following:- Laboratory testing on human cells [C]- Laboratory testing on animals [C-B]- Human clinical trials [A]

- ‘blind trails’ (you’ll need to know what a placebo is)- ‘double blind trials’ - ‘open label trials’

Homeostasis

• How hot do you think our core body temperature is?• 370c

How do we maintain our body temperature in hot environment

Red cheeks

Hairs lie flat

Sweating

Controlling body temperature

• If the body temperature gets too high, the blood flows closer to the skin.

• This is the reason why we get red cheeks.

Sweating

• When your body is hot, sweat glands are stimulated to release sweat.

• The liquid sweat turns into a gas.

Sweating

The skin

Effects of overheating• Being to hot is dangerous.• If too much water is lost through sweating,

the body becomes d_ h _d_ a _ _d.• This can lead to heat stroke and even

death.

How do we maintain our body temperature in a cold

environment?

Shiver

Hairs stand on end

Respire more

Respire more

Effects of being too cold• If the body temperature

fall too low, sweating stops and the muscles begin to s _ _ ver.

• Hypothermia is when the body temperature falls too far below 37oc.

• This causes unconsciousness and sometimes death

Body temperature readings

• Where on the body can body temperature readings be taken from?

ANUS

FINGERSKIN

SURFACE

EARMOUTH

Task• Complete the worksheet.• If you need help put your hand up.