Animal Coordination, Control and Homeostasis

Question 1

What are hormones?

Answer 1

• chemical messengers released directly into the blood
• they are carried in the blood to other parts of the body but only affect target organs
• hormones are produced (and secreted by) various glands, called endochrine glands. these glands make up your endochrine system

Question 2

SB7a Hormones

Describe the different hormones released by the endocrine glands

Answer 2

1. Pituarty Glands
- Releases many hormones including; ACTH, FSH, LH, and growth hormone.
- Located in the brain

2. Thyroid Glands
- Releases many hormones, including thyroxine which is involved in regulating rate of metabolism, heart rate and temperature
- Located in the front of the neck

3. Pancreas
- Contains cells that produce insulin and others that produce glucagon.

4. Ovaries
- Produces the sex hormones oestrogen and progesterone

5. Testes
- Releases the sex hormone testosterone.

6. Adrenal glands
- Releases several hormones, including adreline.

These are all part of the hormonal system which uses chemicals called hormones, which are carried via the blood to the target organ.

Question 3

S87b Hormonal control of metabolic rate

Explain the purposes of adrenalin produced by the body in the blood vessels.

Answer 3

1. Wide blood vessels
- Diameter of blood vessels leading to muscles widens, which increases blood flow to muscles

2. Narrow blood vessels
- Diameter of blood vessels leading to other, organs narrows, which reduces the blood flow to those organs and increases the blood pressure

Question 4

What is the difference between nerves and hormones?

Answer 4

• Nerves are very fast whilst hormones are a slower action
• Nerves act for a very short time whilst hormones act for a long time
• Nerves act on a very precise area whilst hormones act in a more general area

Question 5

How does adrenaline work on the heart?

Answer 5

To get a ‘fight or flight’ response, adrenalone activates processes that increase the supply of oxygen and glucose to cells…

• Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force, so heart rate and blood pressure increase
• this increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration

Question 6

How does adrenaline work on the liver?

Answer 6

• Adrenaline binds to recpetors in the liver
• this causes the liver to break down its glycogen stores to release glucose
• this increases the blood glucose level, so there’s more glucose in the blood to be transported to cells

Question 7

What are negative feedback systems?

Answer 7

• Used to control the levels of hormones (and other substances) in the blood
• When the body detects that the level of a substance has gone above or below the normal level, it triggers a response to bring the level back to normal again

Question 8

How does thyroxine regulate metabolism?

Answer 8

• When blood thyroxine levels are lover than normal, the hypothalamus is stimulated to release thyrotropin releasing hormone (TRH)
• TRH stimulates the pituitary gland to release thyroid stimulating hormone (TSH)
• TSH stimulates the thyroid gland to release thyroxine, so the thyroxine level rises back towards normal
• When blood thyroxine levels become too high, the release of TRH from the hypothalamus is inhibited, reducing production of TSH, so the blood thyroxine level falls

Question 9

What is the menstrual cycle?

Answer 9

Stage 1:
day 1 is when menstruation starts. when the lining of the uterus breaks down

Stage 2:
the uterus lining is repaired. from day 4-14, the uterus lining builds up again until it becomes a thick, spongy layer full of blood vessels, ready for a fertilised egg to implant there

Stage 3:
an egg develops and is released from the ovary (ovulation) at about day 14

Stage 4:
the lining is then maintained for about 14 days, until day 28. if no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again, and the whole cycle starts over

Question 10

What hormones control the menstrual cycle?

Answer 10

FSH (follicle-stimulating hormone):
- triggered by oestrogen and progesterone levels dropping
- released by the pituitary gland
- cause the egg follicle to mature in one of the ovaries
- stimulates to ovaries to produce oestrogen

Oestrogen:
- triggered by rising FSH levels
- released by the ovaries
- causes the lining of the uterus to thicken and grow
- Inhibits the release of FSH
- a high level stimulates an LH surge from the pituarty gland.

LH (luteinising hormone):
- released by the pituitary gland
- the LH surge stimulates ovulation at day 14 - the follicle ruptures and the egg is released
- Inhibits the release of oestrogen
- stimulates the remains of the follicle to develop into a structure called a corpus luteum - which secretes progesterone

Progesterone:
- released by the corpus luteum after ovulation
- maintains the lining of the uterus
- inhibits the release of FSH and LH
- when progesterone levels fall, and there is low oestrogen, the endometrium breaks down
- a low progesterone level allows FSH to increase and then the whole cycle starts again

Question 11

How are hormones used in clomifene therapy?

Answer 11

• some women are infertile because they don’t ovulate or don’t ovulate regularly
• these women can take a drug called clomifene. This works by causing more FSH and LH to be released by the body, which stimualtes egg maturation and ovulation
• by knowing when women will be ovulating, the couple can have intercourse during this time period to improve the chance of becoming pregnant

Question 12

How are hormones used in IVF (in vitro fertilisation)?

Answer 12

• Involves collecting eggs from the woman’s ovaries and fertilising them in a lab using the man’s sperm
• Once the embryos are tiny balls of cells, one or two of them are transferred to the woman’s uterus to improve the chance of pregnancy
• FSH and LH are given before egg collection to stimulate egg production (so more than one egg can be collected)

Question 13

Describe some issues of using fertility treatments.

Answer 13

• As several embryos are implanted, the risk of multiple births is quite high ( Increasing the risk of miscarriage or stillbirths )
• The success rate is not very high; IVF treatment failures can be emotionally upsetting & physically stressful for couples.

Question 14

What is an ART?

Answer 14

• Assisted Reprodcutive Technology
• fertility treatment that involves eggs being handled outside the body
• IVF is an example of this

Question 15

How is oestrogen used as a contraceptive?

Answer 15

• can be used to prevent the release of an egg
• if oestrogen is taken every day to keep the level of it permanently high, it inhibits the production of FSH, and after a while egg development and production stop

Question 16

How is progesterone used as a form of contraceptive?

Answer 16

• one way is by stimulting the production of thick cervical mucus, which prevents any sperm getting through the entrance to the uterus and reaching the egg
• oral contraceptives like the combined pill (prog + oest) and the mini pill (prog only)
• contraceptive injections

Question 17

Adv. of hormonal contraceptive measures

Answer 17

• when used correctly, hormonal methods are more effective at preventing pregnancy than barrier methods
• hormonal methods mean the couple does not have to stop and think about contraception each time they have intercourse (which they would for barrier)

Question 18

Disadv. of hormonal contraceptive measures

Answer 18

• hormonal methods can have unpleasant side-effects, such as headaches, acne and mood changes
• hormonal methods don’t protect against sexually transmitted infections (STIs) - condoms are the only form of contraception that do this

Question 19

What is homeostasis?

Answer 19

• means maintaining a constant internal environment
• conditions in your body need to be kept steady because your cells need the right conditions in order to function properly
• can be dangerous for your health if conditions vary too much from normal levels

Question 20

Examples of homeostasis

Answer 20

Blood glucose regulation: you need to make sure the right amount of glucose in your blood doesn’t get too high or too low

Thermoregulation: you need to reduce your body temperature when you’re hot but increase it when the environment is cold

Osmoregulation: you need to keep a balance between the water you gain (in drink, food, and from respiration) and the water you pee, sweat and breathe out

Question 21

How is glycogen stored in the body?

Answer 21

• the normal metabolism of cells removes blood
• vigorouse exercise removes much more glucose from the blood
• excess glucose can be stored as glycogen in the liver and in the muscles
• when these stores are full, then the excess glucose is stored as lipid (fat) in the tissues

Question 22

How does the body control too high blood glucose concentration?

Answer 22

• when blood with too much glucose enters the blood stream, insulin is secreted by the pancreas
• the glucose in the blood (along with insulin) moves from the blood into liver and muscle cells
• the insulin then makes the liver turn glucose into glycogen
• as a result, blood glucose concetration is reduced

Question 23

How does the body control too low blood glucose concentration?

Answer 23

• when blood with too little glucose enters the blood stream, the pancreas secretes glucagon
• glucagon then makes the liver turn glycogen stored into glucose
• the glucose is released into the blood stream by the liver
• as a result the blood glucose concentration increases

Question 24

SB7e Control of blood glucose

Explain what causes Type 1 diabetes
and how it can be controlled

Answer 24

Type 1 diabetes:
- This is when the pancreatic cells that should produce insulin don’t.
- This is because the cells have been destroyed by the bodies immune system. This means their body cannot control rising blood glucose concentration.
- When blood glucose levels are to high, some can be detected in the urine. So glucose in the urine is usually the first test to be done for type 1 diabetes
- Controlled: People with type 1 diabetes have to inject insulin into the fat below the skin, where it can enter the blood, causing blood glucose concentration to fall

Question 25

# ***SB7f Type 2 diabetes*** Explain what causes **Type 2 diabetes** and how it can be controlled.

Answer 25

**Cause:** - This is caused by **insulin-releasing cells** not producing enough **insulin**, - Or by **target organs** not **responding** properly to the hormone **How it can be controlled:** - For some, just eating **healthy** and keeping sugar **low** in diet can control their diabetes - Being **physically active** can also help, because it takes glucose out of the blood. - Those with more severe type 2 diabetes may be given **medicine** to reduce the amount of glucose released by the liver into the blood, - Or to increase the **sensitivty** of the cells in target organs that respond to insulin

Question 26

# ***SB7g Thermoregulation*** Explain how **thermoregulation** takes place, referring to the **hypothalamus & dermis**

Answer 26

**1. Hypothalamus** - The hypothalamus is a small part of the brain that constantly monitors **temperature** - It recieves information from **temperature receptors** in the **dermis** of the skin. **2.** If blood or brain temperatures drop below **37C** / detects a **cold enviroments**, the following effects can happen - **Shivering** is when muscles start to contract and relax rapidly, Some of the **energy released** from cell respiration for **shivering** warms you up. - Contraction of **erector muscles** in the **dermis** of skin causes **body hairs** to stand up. While not useful for humans, in **mammals** it traps the air next to the skin to act as an **insulator** - **Reduction of blood flow near the skin** keeps warm blood deeper inside the body. This reduces the **rate of transfer** of energy to the air by breathing

Question 27

# ***SB7g Thermoregulation*** Explain how thermoregulation takes place, in reffering to the **hypothalamus & epidermis**.

Answer 27

- If body temperature **rises above 37C**, the **hypothalamus** detects this change and causes sweating. - Sweat spreads out as a thin layer over the **skin epidermis**, where it **evaporates**. As sweat evaporates it **transfers energy** from the skin to the surroundings by heating, so the skin **cools down** - The hypothalamus also **increases blood flow** nearer to the surface of the skin. This makes it **easier for the blood** to transfer energy to the air, so **we cool down**.

Question 28

# ***SB7g Thermoregulation*** Explain how **thermoregulation** takes place, referring to **Vasoconstriction & Vasodilation**

Answer 28

**1. Vasoconstriciton** - When it is cold, the hypothalamus sends **nerve impulses** to small **arteries** deep in the skin, causing them to **narrow**. - This narrowing of the blood vessels is called **Vasoconstriction** - This **reduces blood flow** in **capillaries** near the surface of the skin and helps to **reduce energy transfer** to surroundings. **2. Vasodilation** - When the body is hot, the hypothalamus causes the blood vessels to **widen ( vasodilation )** - This increases blood flow through the skin **capillaries**, bringing **warm blood nearer to the surface** of the skin and increasing **energy transfer** to surroundings.

Question 29

# ***SB7f Type 2 diabetes*** Evaluate the correlation between **Type 2** diabetes and **body mass**.

Answer 29

- As the number of people with **type 2 diabetes** has increased, so has the **average body mass**. We say these 2 factors are **correlated**. - Scientists believes the **more fat someone has on their body**, the more likely they are to **develop type 2 diabetes**. Whether someone has the right mass for their height can be found with; **1. BMI** -> mass ( kg ) / height ( m )^2 **2. waist:hip ratio** -> As people increase in mass, they tend to **develop more fat on their waist**, when compared to their hip.

Question 30

# ***SB7h Osmoregulation*** Explain what is ment by **osmoregulation** and why is it important.

Answer 30

- **Osmoregulation** is the control of the balance of **water** and **mineral salts** in the body. - If the balance of water and mineral salts is wrong, then cells may take in or lose to much water by **osmosis**. - This can damage cells because water in cells allows all the **molecules in the cell's reaction to move around.** - Water is also needed to **maintain the shape** of the cell.

Question 31

# ***SB7h Osmoregulation*** Explain the structure of the **urinary** system.

Answer 31

***Function of urinary system:*** - It is to remove excess amounts of substances from the blood, including **water and mineral salts**. It also removes waste products like **urea** - **Urea** - produced from the breakdown of **amino acids** in the liver that are in greater amounts than needed. ***Structure:*** - The **renal veins** carry **blood with waste** removed back to the **body**. - The **ureters** carry urine from the **kidneys** to the **bladder** - The **bladder** stores urine - The **renal arteries** carry blood from the **body to the kidneys** - The kidneys remove substances from the **blood** and make **urine**. - A muscle keeps the exit from the **bladder closed** until the person decides to urinate - Urine flows through the **urethra** to the outside of the body.

Question 32

# ***SB7h Osmoregulation*** Describe the **2** different methods of treating **kidney failure**.

Answer 32

**1. Kidney dialysis** - Blood carrying waste products **( urea, glucose, excess water, excess salt ions etc )** passes into the machine from a **vein**. - Dialysis fluid contains the **same concentration** of glucose as **blood plasma** - Between the dialysis fluid and the blood their will be a **semi-permeable membrame** in which; **urea, excess water & salt ion + waste products** are diffused out while glucose is constantly **diffusing in and out** of the blood. - This blood with the **waste removed** will be passed from a machine to a vein. **2. Organ Donation** - This is when a kidney from **another person** is put into the patients body. - Replacing a kidney involves several hours of surgery, so **may not be suitable for all**. - Kidneys also have **antigens** on them, this can cause the **rejection** of a donated kidney - Even with a good match the patient may need **life long medication** to prevent kidneys from being rejected - The medication affects the **body's response to infection**, so the patient may catch infection **more easily**.

Question 33

# ***SB7i The kidneys*** Explain the process of how the **nephrons** in the body produced **urine**.

Answer 33

**1.** Blood flows through a **network of capillaries** called a **glomerulus**, which runs inside the **bowman's capsule** of each nephron. **2. Filtration** - The bowman's capsule and glomerulus are adapted to let **very small molecules ( water, urea, glucose )** through into the **nephron**. - Large molecules such as **protiens, and blood cells**, stay in the blood. **3. Selective reabsorption** - this occurs in the nephron to useful substances **( including glucose and mineral ions )**. - These substances are **pumped through proteins** in the cell membranes in the first **convuluted tubule** of nephron, by **active transport**. - No glucose is usually left in urine. **4.** Water is reabsorbed by **osmosis**, depending on the how much the body needs. This happens in the **loop of Henle** and in the **collecting duct**. **5.** At the end of the nephron the **remaining fluid** flows into the **ureter**. The fluid contains **excess water** that the body does not need, plus **urea and other susbtances**. - It is now called urine.

Question 34

# ***SB7i The kidneys*** Explain how the **nephron** is adapted to it's function

Answer 34

**1.** There is a large surface area of contract between the **nephron and capillaries**. **2.** The cell membrane of the cells lining the **first convoluted** tubule has tiny folds called microvilli. These increase the **surface area:volume ratio** of the cells. **3.** Cells that have protien pumps in the **cell membranes** contain many **mitochondria**.

Question 35

# ***SB7i The kidneys*** Explain the effect of **ADH** on the collecting duct.

Answer 35

- When the **pituitary gland** detects that there is too little water in the blood, it releases the **hormone ADH**. - **ADH** changes the **permeability** of the **collecting duct** in nephrons and increases the **concentration of urine**. - If the **collecting duct** is permeable, **water is absorbed** by osmosis from the **collecting duct** back into the blood. - When there is **plenty of water** in the blood, the **pituatary gland** stops releasing **ADH**.