Excretion

By the end of this lesson, you should be able to:

2.77 understand that organisms are able to respond to changes in their environment

2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis

2.79 understand that a coordinated response requires a stimulus, a receptor and an effector

2.68 recall that the lungs, kidneys and skin are organs of excretion 

Starter:

Make a brainstorm of some things which need to be maintained or controlled within the body.

Homeostasis

Remove Waste Products: P246-247

CARBON DIOXIDE

How it’s formed

Why it has to be removed

Where it’s removed

UREA

How it’s formed

Why it has to be removed

Where it’s removed

Maintaining Body Balance

Blood Sugar

Water and Ion content need to be controlled

Body temperature

Carbon Dioxide

What organs are involved?

Gap Fill

blood carbon dioxide constant controlled environment enzymes homeostasis

glucose temperature urea water

The internal ……………… of your body is kept relatively …………… by a whole range of processes that together are known as ……………… . Waste products such as …………… and ………………have to be removed from your ………….. all the time. The …………. and ion concentration in your blood are constantly ………………. and so is your blood ………….. level. Your body ………….. is kept within a narrow range so your …………. work effectively.

By the end of this lesson, you should be able to:

2.69 understand how the kidney carries out its roles of excretion and osmoregulation 

2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

Kidney Structure and Function

Flash Version

The Urinary System

How the Kidney Works

By the end of this lesson, you should be able to:

2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

2.71 describe the structure of a nephron 2.74 understand that selective reabsorption of

glucose occurs at the proximal convoluted tubule 2.73 understand that water is reabsorbed into the

blood from the collecting duct 2.76 understand that urine contains water, urea and

salts.

Starter:

The Kidneys

Function

1. Filtering the blood – urea, glucose, mineral ions, amino acids and water diffuse from the blood and into the kidney tubules.

2. Large molecules such as proteins and red blood cells are too large and remain in the blood.

3. All the sugar is reabsorbed back into the blood by active transport

4. Mineral ions are selectively reabsorbed by active transport depending on the body needs

5. Water is selectively reabsorbed depending on the body needs

6. Excess ions, water and Urea are stored in the bladder and released as urine.

Capillary pressure forces fluid from blood into the bowman's capsule.

The Glomerular filtrate consists of water, ions and small molecules. The proteins and blood cells are too large and the selective process is known as Ultrafiltration.

All glucose is reabsorbed in the proximal convoluted tubules

Questions

1. What is the function of the kidneys? (2)2. How do they carry out their job (3)3. What is contained in Urine and how is it

created? (3)4. Explain how your kidney would maintain

the water and mineral balance of your blood on:

a: A cool day when you stayed indoors and drank lots of tea. (2)b: A hot sports day when you ran three races and forgot your drinks bottle. (2)

By the end of this lesson, you should be able to:

2.90 understand the source, role and effect of the hormone ADH in regulating the water content of the blood.

2.75 describe the role of ADH in regulating the water content of the blood

Starter:

Control of Water

Osmoregulation

Too Much Water

Too Much Water

1) Hypothalamus detects too much water in blood.

1) Hypothalamus detects too much water in blood.2) Pituitary gland releases less ADH

2) Pituitary gland releases less ADH

3) Kidneys reduce blood water level

3) Kidneys reduce blood water level

4) So more water reaches bladder (urine more dilute)

4) So more water reaches bladder (urine more dilute)

5) Blood water level returns to normal

5) Blood water level returns to normal

Osmoregulation – ADH conserves water

Too little Water

Too little Water

1) Hypothalamus detects too little water in blood.

1) Hypothalamus detects too little water in blood.2) Pituitary gland releases ADH

2) Pituitary gland releases ADH

3) Kidneys maintain blood water level

3) Kidneys maintain blood water level

4) So less water is lost in urine (urine more concentrated)

4) So less water is lost in urine (urine more concentrated)

5) Blood water level returns to normal

5) Blood water level returns to normal

Negative Feedback

Change in Internal

Environment

Internal Environment Normal

Internal Environment Returns to

Normal

Correcting Action

Detector Senses Change

By the end of this lesson, you should be able to:

2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

Starter:

Control of Body Temperature