Topic 7 - Animal coordination, control and homeostasis

Question 1

Where are hormones produced and transported around the body

Answer 1

• Hormones produced by ENDOCRINE glands, released into blood
• travel around body in blood until reaching target organ
• hormone causes target organ to respond, eg by releasing another chemical substance
• different hormones, different target organs, different responses

Question 2

Describe all the hormones and their target organs

Answer 2

TRH and CRH - pituary gland
TSH - thyroid gland
ADH - kidney
FSH and LH - ovaries
INSULIN and GLUCAGON - liver, muscle and adipose tissue
ADRENALIN - various organs, eg heart, liver, skin
PROGESTERONE - uterus
OESTROGEN - ovaries, uterus, pituary gland
TESTOSTERONE - male reproductive organs

Question 3

Explain the main differences between hormones and nerve impulses

Answer 3

HORMONES:

• chemical signal
• transported in bloodstream
• cells in particular tissues (more specific)
• slow
• long duration

NERVES:

• electrical signal
• transmission between/through nerve cells
• muscles or glands
• very rapid
• short duration

Question 4

Explain the effects of adrenalin and what its in response to

Answer 4

—> ADRENALIN released from adrenal glands, response to stress. Causes fight or flight

Effects:

• increases heart rate
• constricts some blood vessels, make blood pressure higher
• dilates other blood vessels, increases blood flow to muscles
• causes liver to convert glycogen -> glucose, which is released into the blood

Question 5

Explain what thyroxine controls and how it controls it

Answer 5

—> THYROXINE controls metabolic rate (rate of cells respire - rate of energy transfers)

How it controls metabolic rate:

1. low levels stimulates TRH production in hypothalamus
2. causes TSH release from pituitary gland
3. TSH acts on thyroid to produce thyroxine
4. when normal levels thyroxine stops the release of TRH and the production of TSH

Question 6

Describe the stages in the menstrual cycle

Answer 6

MENSTRUATION - break down of uterus lining - begins on day 1 of the cycle and usually lasts about 5 days

second week - the lining of the uterus is gradually built up

OVULATION - release of egg from ovary - day 14

Days 14 to 16 - fertilisation most likely

lining continues to build up - weeks 3 and 4

If fertilisation occurs, uterus lining is maintained and menstruation doesn’t happen

Question 7

Which two hormones control the menstrual cycle and their roles and where are they produced

Answer 7

OESTROGEN - causes growth and repair of lining of uterus wall. Oestrogen inhibits FSH, produced in the ovaries

PROGESTERONE - produced by adrenal cortex, ovaries and testes. triggers lining to thicken

Question 8

Explain the interactions of oestrogen, progesterone, FSH and LH in the control of the menstrual cycle

Answer 8

1. FSH secreted from pituitary gland, causes a follicle in ovary to mature
2. As matures, secretes oestrogen which inhibits FSH and starts thickening lining
3. high concentration of oestrogen —> surge in LH from pituitary
4. ovulation caused when egg is released from follicle
5. ruptured follicle becomes a corpus luteum - secretes progesterone, oestrogen - cause more thickening of lining
6. Progesterone inhibits FSH and LH. If egg isnt fertilised —> corpus luteum breaks down, progesterone concentration falls
7. triggers menstruation, FSH not inhibited, can be secreted from pituitary gland

Question 9

Explain the two types of contraception

Answer 9

HORMONAL - releasing hormones to prevent ovulation, thicken mucus at the cervix, preventing sperm
Eg :
Hormone pills, implants or injections

BARRIER - stops sperm reaching egg
Eg :
Male and female condoms, the diaphragm, caps and sponges

Question 10

Give one advantage and one disadvantage of hormonal contraceptives compared with condoms

Answer 10

Hormonal contraceptives more effective than condoms ( >99%) at preventing pregnancy.

condoms protect STD’s, hormonal contraceptives do not

Question 11

Explain how fertility drugs can be used to help fertility

Answer 11

CLOMIFENE can be used to cause + FSH and LH

1. Fertility drug given to stimulate eggs to mature
2. Eggs taken from ovaries
3. Eggs + sperm in dish for fertilisation
4. Fertilised eggs —> embryos
5. When embryos are tiny balls of cells, one or two placed in mothers womb to develop

Question 12

Define IVF (in-vitro fertilisation)

Answer 12

Fertilisation outside a woman’s body

Offered to those with conceiving problems

Question 13

Follicle-stimulating hormone (FSH) is used to stimulate ovulation in a woman undergoing IVF treatment, even if she ovulates naturally, explain why. (2 marks)

Answer 13

stimulate the maturation of many eggs. Normally only one egg would mature in a normal cycle.

Question 14

What is an advantage of using FSH in IVF treatment

Answer 14

Stimulating more eggs -> more embryos can be produced.

means enough embryos for woman to undergo several cycles if necessary

Question 15

Explain homeostasis

Answer 15

Maintains conditions in body, constant level, response to internal/external change.

NEGATIVE FEEDBACK mechanisms respond change, help restore normal level

Question 16

Define the relationship between thermoregulation and body temperature

Answer 16

THERMOREGULATION keeps core body temperature steady (around 37 degrees)

Controlled by hypothalamus (Thermoregulatory centre monitors and controls temp) , triggers change in skin and muscles

Question 17

What corrections does the body make to a hot temperature environment

Answer 17

INCREASES energy transferred to surroundings by:

• changes triggered - blood flow so more blood flows near skin surface (dilate or constrict to change blood flow)
• sweat glands release more sweat onto skin surface to evaporate
• sebaceous glands produce oil that helps sweat spread out on skin

Question 18

What corrections does the body make to a cold temperature environment

Answer 18

REDUCES energy transferred -> surroundings by:

• less blood near surface
• sweat stopped produced by glands
• body hairs raised by erector muscles in skin (goosebumps)

Question 19

Explain why its important for the enzymes in our bodies that our internal temperature is fairly constant (2 marks)

Answer 19

Enzymes work fastest @ optimum

lower or higher, aren’t active, chemical reactions arent carried out as normal, causing harm to body

Question 20

Define osmoregulation and its effect on animal cells

Answer 20

Controls amount water lost in urine, controls amount water in body

Stops animal cells swelling up/shrinking by osmosis if body water content changes

Question 21

Explain the structure of the skin in thermoregulation

Answer 21

Vasodilation/vasoconstriction changes blood flow in surface capillaries depending on temperature in dermis

Sweat glands in dermis release sweat when warm to lose heat through evaporation

hair muscle contracts when cold to pull hairs upright, trapping layer of air, when warm hairs lie flat

Question 22

Describe the role of the dermis and epidermis of the skin in cooling the body (4 marks)

Answer 22

Sweat glands in the dermis secrete sweat on to the epidermis. This evaporates, cooling the body down.

Muscles in dermis relax, hairs can lie flat. there is thinner layer of insulating air trapped against epidermis

Question 23

Explain and describe vasoconstriction and the structure when a cold temperature is detected

Answer 23

More blood flows through deep skin blood vessels so less blood flows through surface capillaries

This keeps warm blood deeper in the skin so less heat is transferred to air. Little heat loss from skin

Question 24

Explain and describe vasodilation and the structure when a hot temperature is detected

Answer 24

Less blood flows through deep skin blood vessels and more blood flows through surface capillaries.

This increases heat loss by radiation

Increases blood flow of warm blood near skin so heat can transfer easily to air

Question 25

Explain how shivering affects body temperature when a cold environment is detected

Answer 25

Muscles quickly contract and relax in succession (causing shivering) releasing energy to warm the body

Question 26

Describe osmoregulation in terms of a negative feedback system (3 marks)

Answer 26

If there is too much water in the body this means that more water is excreted in urine. If there isn’t enough water then less water is excreted in urine, helping to increase water levels again. This is an example of negative feedback because the body works to restore the balance

Question 27

A pale skinned person may look pink after exercise. Identify what causes this change (1 mark) Describe and explain what effect this has on body temperature (2 marks)

Answer 27

They look pink because more blood is flowing near the surface of the skin as a result of vasodilation (1) This increases the rate of transfer of heat energy from the body to the environment and so reduces body temperatures

Question 28

Explain how the hormone insulin controls blood glucose concentration

Answer 28

If the blood glucose concentration is too high, the pancreas produces the hormone insulin, this causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage Insulin controls the storage of glycogen in your liver and muscles

Question 29

Explain how blood glucose concentration is regulated by glucagon

Answer 29

When blood glucose levels fall, the pancreas releases glucagon This causes your liver to break down the glycogen back into glucose

Question 30

Explain the importance of glucose and pancreas

Answer 30

GLUCOSE is vital for respiration, allowing the body to release energy The PANCREAS monitors and controls blood glucose concentration using insulin and glucagon

Question 31

Explain the effect of low glucose on the pancreas, liver and blood glucose levels

Answer 31

PANCREAS - insulin not secreted into the blood LIVER - doesn’t convert glucose into glycogen BLOOD GLUCOSE LEVEL - Increases

Question 32

Explain the effect of high glucose on the pancreas, liver and blood glucose levels

Answer 32

PANCREAS - insulin secreted into the blood LIVER - converts glucose into glycogen BLOOD GLUCOSE LEVEL - decreases

Question 33

Explain the cause of type 1 diabetes

Answer 33

Caused when the immune system has damaged the persons insulin-secreting pancreatic cells, person doesn’t produce INSULIN

Question 34

Explain how type 1 diabetes can be controlled

Answer 34

Inject insulin into the fat below the skin They have to work out the right amount of insulin to inject so that the blood glucose concentration is kept within safe limits

Question 35

Explain the cause of type 2 diabetes

Answer 35

Person doesn’t produce enough insulin but their liver and muscle cells have become RESISTANT to it

Question 36

Explain how type 2 diabetes can be controlled

Answer 36

Most people eat less sugary foods and exercise Medication can be used if needed

Question 37

Evaluate the correlation between body mass and type 2 diabetes including waist:hip calculations and BMI

Answer 37

Measurements of fat, estimations used: 1. BMI : mass (kg) / height^2 (m) (Assumes that the mass of the body tissues is in proportion to height) 2. Fat closely linked to cardiovascular disease is abdominal fat Divide waist by hip measurement to get waist:hip ratio

Question 38

Describe the structure of the urinary system

Answer 38

RENAL VEINS - carry cleaned blood back to the body URETERS carry URINE from the kidneys to the bladder BLADDER stores urine Urine flows through the URETHRA to the outside of the body RENAL ARTERIES carry blood from the body to the kidneys KIDNEYS remove substances (urea) from blood and makes urine A muscle keeps the exit from the bladder closed until we decide to urinate

Question 39

What is the difference between urea and urine, and the ureter and urethra

Answer 39

Urea is produced from the breakdown of excess amino acids in the liver, its toxic in excess however urine contains urea, water and salts. Ureters are tube-like structures that connect the kidneys with the urinary bladder however urethra is a tube that connects the urinary bladder to the outside of the body

Question 40

Explain how the structure of the nephron is related to its function in filtration in the glomerulus and Bowman’s capsule

Answer 40

Filtration of small molecules from blood into tubule, including water, glucose, salts and urea in the glomerulus and bowmans capsule Glomerulus - small knot of capillaries Bowman’s capsule - cup shaped

Question 41

Explain how the structure of the nephron is related to its function in selective reabsorption of glucose

Answer 41

Selective reabsorption of glucose from tubule back into blood by active transport (Selective reabsorption - useful molecules absorbed back into blood, other molecules left in tubule)

Question 42

Explain how the structure of the nephron is related to its function in reabsorption of water

Answer 42

Reabsorption of water that the body needs from the tubule back into the blood (osmoregulation) This happens in the COLLECTING DUCT

Question 43

Explain the effect of ADH on the permeability of the collecting duct in regulating the water content of the blood

Answer 43

ADH - increases permeability of cell membranes in collecting duct of nephron So more water reabsorbed from urine by osmosis

Question 44

Explain the function of the hormone ADH

Answer 44

Amount of water reabsorbed from the nephrons is controlled by ADH (Antidiuretic hormone) Regulates water content of blood (osmoregulation)

Question 45

Explain what is meant by a negative feedback mechanism, using ADH production as a example (4 marks)

Answer 45

As increase in blood water content causes the pituitary gland to secrete less ADH. This causes less water to be reabsorbed by the collecting duct in the kidneys so more water is excreted by kidneys. A decrease in blood water content causes the pituitary gland to secrete more ADH, which causes less water to be excreted by the kidneys. This is a negative feedback mechanism because a change in blood water content causes an opposite change that restores the ‘normal’ blood water content

Question 46

Describe kidney dialysis as a treatment for kidney failure

Answer 46

KIDNEY FAILURE is when it stops working so excess water, mineral ions and urea build up KIDNEY DIALYSIS is carried out every 2 or 3 days It uses diffusion which restores which restores normal dissolved substance concentrations in the blood. Urea then diffuses out of the blood into the dialysis fluid Dialysis fluid contains the same concentration of useful substances as blood so glucose and mineral ions aren’t lost

Question 47

Describe kidney transplant as a treatment for kidney failure

Answer 47

Healthy kidney connected to blood circulation to replace PROBLEMS : Antigens on transplanted kidney cells different to patients. Antibodies in patient attack kidney and reject it PREVENTING REJECTION: - antigens must be as similar as possible - drugs for life to reduce effects of immune system (patient may get more infections than usual)