The Kidneys + The menstrual cycle

Question 1

Explain why it is important that the body keeps the level of water in the blood as constant as possible

Answer 1

it is important that the body keeps the level of water in the blood as constant as possible

This is because if the blood becomes too dilute then water moves into cells by osmosis (from a dilute solution to a concentrated solution across a partially permeable membrane) and they may burst.

and if the blood becomes too concentrated then water moves out of cell by osmosis (from a dilute solution to a concentrated solution across a partially permeable membrane)
and the cells may shrivel

If body cells gain or lose too much water by osmosis then they don’t work efficiently

Question 2

How does the body take in water

Answer 2

The body takes in water through food and drink

Question 3

Describe the different ways that water can leave the human body

Answer 3

Water leaves the body via the lungs during exhalation.
Water, ions and urea are lost from the skin in sweat
(sweat also contains ions and contains the waste product urea)
Excess water, ions and urea are removed via the kidneys in the urine.

Question 4

Which types of water loss does the body have no control over

Answer 4

There is no control over water loss via the lungs during exhalation or water, ion or urea loss from the skin by sweating. This is because sweating is part of the body’s temperature control system.

Question 5

Which types of water loss does the body have control over

Answer 5

The body can control how much water is lost in urine

Question 6

What happens do the kidneys do if the blood is too dilute

Answer 6

If the blood is too dilute, the kidneys remove the excess water and they produce a greater volume of urine.

Question 7

Describe how the kidneys remove the waste product urea

Answer 7

Humans have two kidneys
Blood enters the kidney through an artery and this blood contains the waste product urea
The kidney removes this urea as well as excess ions and excess water
These leave the kidney as urine and this is stored in the bladder
The blood now leaves the kidney through a vein. The blood now contains no urea

This is called filtration

Question 8

Describe how the kidneys adjust the levels of water and ions (molecules) in the blood

Answer 8

The blood passes through the capillaries.
Here, small molecules are filtered out of the blood
These include urea, ions and water, as well as the sugar glucose.
These pass into tiny tubules (a very small tube)

Now, all of the glucose, some of the ions and some of the water is reabsorbed back into the blood.
This is called selective reabsorption.

Urea, excess ions and excess water are released as urine

All of the urea has been removed from the blood and the concentrations of water and ions have been adjusted

Question 9

https://www.youtube.com/watch?v=DbLVB_EDnRs&list=PL9IouNCPbCxW3lptxS1yHCP2I9YDfM2co&index=10
3:23
EXPLAIN WHY THE GRAPH IS LIKE THIS

Answer 9

This shows the concentrations of glucose, ions and urea in the blood before and after it has passed through the kidneys

The concentration of glucose in the blood has not changed.
This is because the kidneys filter glucose out of the blood but then reabsorb it all back into the blood

The concentration of ions in the blood has decreased
This is because the kidneys filter ions out of the blood, but they then reabsorb a certain amount of ions back into the blood depending on the needs of the body

The concentration of urea in the blood falls to virtually zero as it passes through the kidneys
That is because the kidneys filter out all of the urea and do not reabsorb it

Question 10

Explain the role of the kidney in maintaining the concentration of substances in the blood

Answer 10

The blood passes through the capillaries.
Here, small molecules are filtered out of the blood
These include urea, ions and water, as well as the sugar glucose.
These pass into a tube

Now, all of the glucose, some of the ions and some of the water is reabsorbed back into the blood.
This is called selective reabsorption.

Urea, excess ions and excess water are released as urine

All of the urea has been removed from the blood and the concentrations of water and ions have been adjusted

Humans have two kidneys
Blood enters the kidney through an artery and this blood contains the waste product urea
The kidney removes this urea as well as excess ions and excess water
These leave the kidney as urine and this is stored in the bladder
The blood now leaves the kidney through a vein. The blood now contains no urea

Question 11

Explain how the body can have excess amino acids

Answer 11

Proteins are long chains of amino acids
We get a lot of protein in our diet
When we digest this protein, amino acids pass into the blood
(the problem is that) We often eat more protein than the body needs. causing the body to have excess amino acids.

_____________
spec: The digestion of proteins from the diet results in excess amino acids which need to be excreted safely

Question 12

Explain how the body deals with excess amino acids

Answer 12

The liver breaks down the excess amino acids and produces the chemical ammonia
This process is called deamination
Ammonia is a very toxic chemical so the liver immediately converts it to urea
The urea can be safely excreted by the kidneys

Answer 13

A person is exercising on a hot day
The body sweats to cool down
This means that the body is losing water

Question 14

Describe how the hormone ADH is used to control the water level in the blood

What happens if the blood becomes too concentrated

Answer 14

how negative feedback controls water content
(receptor in the brian detects that the water content is too high/low
coordination centre in the brain recieves the information and coordinates a response
The pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubule/pituitary gland releases more ADH, so more water is reabsorbed from the kidney tubules)

If the blood becomes too concentrated (the level of water in the blood falls), then the pituitary gland releases the hormone ADH into the bloodstream

ADH travels to the kidneys and it causes the kidney tubules to become more permeable to water (more water can now pass out of the kidney tubules)

This means that more water is reabsorbed from the tubules back into the blood

Because of this, less urine is produced and the amount of water in the blood rises back to its normal level.

As the level of water in the blood returns to normal, the pituitary gland stops releasing ADH

This is called a negative feedback cycle
This is controlled by negative feedback.

Question 15

What happens if the blood becomes too dilute

Answer 15

If the concentration of blood becomes too dilute (concentration of water in the blood rises), the pituitary gland stops releasing ADH

This means that the kidneys reabsorb less water into the blood
Now more urine is produced and the concentration of water in the blood returns to normal

Question 16

How can the blood become too dilute

Answer 16

If a person drinks a large amount of water
This causes the concentration of water in the blood to rise

Question 17

What is kidney dialysis

Answer 17

The process of cleansing the blood through a dialysis machine when the kidneys fail

Question 18

Describe how kidney dialysis works

Answer 18

When a patient has kidney failure, their blood will contain a higher concentration of water, ions and urea than it should.

In kidney dialysis, the patient’s blood passes over a semi-permeable membrane.
This allows urea, ions and water through but it will not allow larger molecules such as proteins to pass through
Blood cells are also too large to pass through the membrane

On the other side of the membrane there is the dialysis fluid
The dialysis fluid contains the normal concentrations of glucose, water and ions but it does not contain any urea.
This means that useful dissolved ions and glucose wont be lost from the blood during dialysis.

There is a concentration gradient for urea. So the urea diffuses from the blood into the dialysis fluid.
The dialysis fluid is constantly refreshed. This ensures that there is always a large concentration gradient for urea.

The dialysis fluid also contains the normal concentrations of water and ions
This means that some of the excess water and some of the excess ions will diffuse from the blood into the dialysis fluid

Because of this, the concentrations of water and ions in the patient will return to normal

Question 19

State the advantages of kidney dialysis

Answer 19

There is no shortage of dialysis machines

Question 20

State the disadvantages of kidney dialysis

Answer 20

Kidney dialysis can be inconvenient.
Patients have to visit a hospital several times a week
They also have to eat a controlled diet so they do not produce too much urea

Requires frequent treatments (which make it inconvenient) and a (patients have to follow a) controlled diet

Kidney Dialysis is expensive in the long term (it is expensive and requires long term treatment)

Question 21

State a better alternative to kidney dialysis

Answer 21

A kidney transplant

Question 22

What is a kidney transplant

Answer 22

In a kidney transplant, the diseased kidney is replaced with a health kidney from a donor

Question 23

State the advantages to a kidney transplant

Answer 23

Allows a patient to lead a normal life
Only expensive initially

Question 24

State the disadvantages to a kidney transplant

Answer 24

There is a shortage of kidney donors

The donated kidney may be rejected by the patient’s immune system

Patients have to take anti-rejection drugs for the rest of their lives

Question 25

Filtration

Question 26

What do reproductive hormones cause to happen during puberty

Answer 26

During puberty reproductive hormones cause secondary sex
characteristics to develop E.G. pubic hair

Question 27

What is the main reproductive hormone for men and where is this produced

Answer 27

In men, the testes produce the hormone testosterone. Testosterone stimulates the testes to produce sperm

Question 28

What is the main reproductive hormone for female and where is this produced

Answer 28

In women, the ovaries produce the hormone oestrogen.

Question 29

What happens for women when puberty begins

Answer 29

Once puberty begins, eggs in the ovaries start to mature. Every 28 days an egg is released. This is called ovulation

Question 30

What cycle is the release of an egg every 28 days part of

Answer 30

The release of an egg every 28 days is part of the menstrual cycle

Question 31

Describe what happens in the menstrual cycle

Answer 31

Every 28 days, the ovaries releases an egg. This is called ovulation.

In preparation for this, the uterus lining becomes thick and spongy.
The egg now makes its way down to the uterus.
If sperm is present, then the egg can be fertilised
If this happens it can implant into the uterus wall and develop into a baby.

However if the egg does not get fertilised then both the egg and the uterus lining are released.
This is called a period.

Question 32

Describe the roles of hormones in human reproduction, including the hormones involved in the menstrual cycle

Answer 32

Follicle stimulating hormone (FSH) causes an egg to mature in the ovary

Luteinising hormone (LH) causes this egg to be released (ovulation)

Oestrogen (produced by the ovary) and progesterone are involved in maintaining the uterus lining, in case the egg is fertilised and implants

(oestoregen causes the lining of the uterus to develop
progesterone maintains the lining of the uterus)

Question 33

Describe how the hormones interact in the control of the menstrual cycle

Answer 33

In the first stage, Follicle stimulating hormone (FSH) is released by the pituitary gland.

FSH travels in the blood to the ovaries where it causes an egg to mature.
At the same time, FSH triggers (stimulates) the ovaries to make oestrogen. Oestrogen cause the lining of the uterus to become thick.
Oestrogen (inhibits) stops the pituitary gland from releasing any more FSH

Instead, the pituitary gland now releases luteinising hormone (LH).
LH causes the mature egg to be released (ovulation)
Once the ovary has released its egg, the ovary now produces the hormone progesterone

Progesterone has two effects
Progesterone stops (inhibits) the pituitary gland from releasing FSH and LH. This is to prevent any more eggs from maturing or being released
Progesterone keeps the lining of the uterus thick (maintains the lining of the uterus) in case a fertilised egg implants.

If fertilisation does not take place, then the level of progesterone falls.
The uterus lining and the egg are now released and the women has a period.

Question 34

https://bam.files.bbci.co.uk/bam/live/content/zysktv4/small

Interpret this graph (of these hormones during the menstrual cycle)

Answer 34

The level of FSH rises and this triggers the ovaries to release oestrogen
As the level of oestrogen increases, this inhibits the production of FSH, so the level of FSH falls

Oestrogen triggers the release of LH so the LH level rises to a peak around day 14
LH triggers ovulation and once this happens, the ovary now produces progesterone
So the progesterone level now rises

As the level of progesterone increases, this inhibits the production of FSH and LH, so the level of FSH and LH falls

However if fertilisation does not happen, then the progesterone levels fall again and the women has her period