B3-Organism Level Systems

Question 1

1.) Describe the role of sensory neurones.

Answer 1

1.) Send electrical impulses from the receptor to the CNS

Question 2

2.) Give an example of the effector.

Answer 2

2.) Muscle or Gland

Question 3

3.) Describe the path way from the stimulus through the central nervous system.

Answer 3

3.) Stimulus, Receptor, Sensory neurone, CNS, Motor neurone, Effector and Responce.

Question 4

4.) Draw a diagram of a typical neurone and label all of its parts.

Answer 4

4.) Dendrites, cell body, nucleus, axon and insulating sheath.

Question 5

5.) Describe what happens in the synapse.

Answer 5

5.) The electrical impulse triggers the release of transmitter chemicals which diffuse across the synapse.
These chemicals bind to receptor molecules in the membrane of the next neurone. This sets off a new electrical impulse.

Question 6

6.) What is the job of the myeline sheath?

Answer 6

6.) It insulates the electrical message.

Question 7

7.) What is the purpose of a reflex arc?

Answer 7

7.) They allow for even quicker responses they play a protective role to stop you getting hurt.

Question 8

8.) Describe the pathway of a reflex arc from stimulus to response.

Answer 8

8.) Stimulus to the sensory neurone to a relay neurone bypassing the CNS along the motor neurone to the effector which releases a response.

Question 9

9. ) Describe the functions of these structures in the eye:
   a. ) iris
   b. ) lens
   c. ) ciliary body

Answer 9

9. )a.) Iris controls how much light enters the eye.
   b. ) Lens refracts the light on the retina.
   c. ) Ciliary Body works with the suspensory ligaments to alter the shape the lens.

Question 10

10.) Describe the path way of light through the eye.

Answer 10

10.) The cornea refracts light into the eyes, the iris controls how much light enter the eye, the lens refracts light onto the retina the rods and cones then the optic nerves carries impulses to the brain.

Question 11

11.) How and what changes the lens to allow you to see short and long distances.

Answer 11

11. )a.) Short distances the ciliary muscle contracts which slackens the suspensory ligaments and the lens becomes a rounded shape.
    b. ) Long distances ciliary muscles relaxes suspensory ligaments pull tight and the lens becomes thinner.

Question 12

12.) What do the cones and the rods do and what is the condition called that means you can’t see colours.

Answer 12

12. )a.) Cones help us to see colour and reside in the back of the eye on the retina.
    b. ) Rods help us to detect light especially in dim light.
    c. ) Colour-blind is the disorder the most common being the red-green.

Question 13

13.) Produce a sketch of the brain an label the cerebrum , cerebellum, pituitary gland, hypothalamus and medulla.

Answer 13

13.) Cerebrum - outer wrinkly bit
Hypothalamus - small bean above the pituitary gland
Pituitary Gland - Small bean under hypothalamus and it is connected to a tube
Medulla - B-shaped part which is quite long
Cerebellum - at the back of the brain which looks like a clover.

Question 14

14.) What do all the parts of the brain do?

Answer 14

14. )a.) Cerebrum is responsible for consciousness, intelligence, memory and language.
    b. ) Hypothalamus is responsible in maintaining temperature at the normal level and it produces hormones which are responsible for the pituitary gland.
    c. ) Pituitary Gland is responsible for making hormones such as FSH and LH needed in the menstrual cycle.
    d. ) Medulla is responsible for unconcious activities like breathing and heart rate.
    e. ) Cerebellum is responsible for muscle co-ordination.

Question 15

15.) Describe the difficulties involved in investigating the brain.

Answer 15

15.) If someone is severely brain damaged they may not be able to give informed consent. People have to donate their brains to research. There maybe problems with interpreting the fRMI results as there maybe to much activity in the brain.

Question 16

16.) What is the endocrine system?

Answer 16

16.) Hormones and chemicals stored in glands which make up the endocrine system which moves through the blood and controls the rate of reactions in the body.

Question 17

17.) What does thyroxine do?

Answer 17

17.) It regulates the metabolic rate - the speed at which chemical reactions occur in the body

Question 18

18.) Explain how negative feedback system helps to control the level of thyroxine in the blood.

Answer 18

18.) A low thyroxine level is deleted in the blood and TSH is released from the pituitary gland this causes thyroxine levels to increase to a normal level and it continues to increase until the brain detects there is too much thyroxine in the blood and it tells the pituitary gland to stop producing TSH and the levels of thyroxine decrease making them return back to normal. The negative feed back system keeps the amount of thyroxine at the right level.

Question 19

19.) Describe the effect of adrenaline.

Answer 19

19.) Prepares the body for fight of flight by binding to the receptors on the heart causing the heart muscle to repeatedly contract so heart rate and blood pressure increases, this increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration. It binds to the receptors in the liver causing the breakdown of glycogen into glucose increasing blood glucose levels for respiration.

Question 20

20. ) What do the following hormones do :
    a. ) testosterone
    b. ) oestrogen
    c. ) progesterone
    d. ) FSH

Answer 20

20. )a.) Testosterone - main male sex hormone produced in the testes and it stimulates testosterone and is important for the development of the male reproductive system.
    b. ) Oestrogen - main female sex hormone produced in the ovaries involved the menstrual cycle and promotes female sexual characteristics such as breast development.
    c. ) Progesterone - produced in the ovaries and helps to support pregnancy and the menstrual cycle.
    d. ) FSH - produced in the pituitary gland along with LH and help to control menstrual cycle.

Question 21

21.) Explain how the menstrual cycle work.

Answer 21

21.) FSH causes an egg to mature in one of the ovaries and stimulates the ovaries to produce oestrogen. Oestrogen then causes the lining of the uterus to thicken and grow it stimulates LH and inhibits FSH so only one egg is released. LH stimulates the release of an egg (day 14) ovulation and indirectly stimulates progesterone. Progesterone maintains the lining and inhibits LH and FSH when progesterone falls so does oestrogen and the lining breaks down and FSH and LH increases.

Question 22

22.) Explain how the contraceptives using progesterone are and their names.

Answer 22

22.) Injection (3 months), Implant (3 years), IUS - T-shaped piece of plastic inserted into the uterus(3-5 years), Mini pill - taken every day.
Stimulates thick cervical mucus, thins the lining and prevents ovulation by inhibiting FSH and LH.

Question 23

23.) Explain how the contraceptives using oestrogen and progesterone work and their names.

Answer 23

23.) Combined pill - 21 day cycle and 7 days no pill
Patch - worn in a 4 week cycle replaced once a week for 3 weeks
Stimulates thick cervical mucus, thins the lining and prevents ovulation by inhibiting FSH and LH.

Question 24

24.) How do hormones help pregnancies?

Answer 24

24.) FSH and LH produce eggs needed to reproduce and progesterone helps to support pregnancy.

Question 25

25.) Explain the four non-hormonal methods of contraception.

Answer 25

25. )a.) Barrier methods - Condom(98% effective), Female Condom (95% effective), Diaphragm - fits over the cervix to stop the sperm meeting the egg has to be fitted by a GP and the first time it is used with spermicide (92-96%.)
    b. ) IUD’s - T-shaped devices that contain copper inserted into the uterus to alter the lining of the womb so the egg can’t implant (99% effective for 10 years.)
    c. ) Natural Methods - Not having intercourse at the time of ovulation and withdrawal and are very inaffective.
    d. ) Sterilisation - is a surgical procedure to cut and tie tubes in the reproductive system. The methods are over 99% effective.

Question 26

26.) What are some pros and cons to all forms of contraception?

Answer 26

26. )a.) Side-effects such as mood swings, irregular periods, acne and headaches.
    b. ) Possibility of doing it wrong if the condom splits or the pills aren’t taken properly.
    c. ) Medical input may be uncomfortable about procedures involved.
    d. ) Length of action, some contraceptive methods last a long time and people may decide they want to start a family but can’t until the contraception wears off.
    e. ) Sexually Transmitted Diseases are only stopped by condoms only pills won’t work against STI’s.

Question 27

27.) Explain how auxins make the plant shoot grow toward the light.

Answer 27

27.) The auxins in the shoot cause the plant to be positively phototropic because they collect near the shaded side of the shoot causing the underside of the shoot to elongate and grow upwards towards the sun.
( in roots it causes the underside of the plant to stop growing an the top of the root elongates and it is positively gravitropic.

Question 28

28.) What does gibberellin do?

Answer 28

28.) It stimulates seed germination, flowering and stem growth ( causes stems to elongate) and it work along with auxins.

Question 29

29.) What does ethene do?

Answer 29

29.) It calls the cells in the leaf to expand and fall off and it stimulates enzymes which cause the fruit to ripen.
(Auxin inhibits the shedding of young leaves.)

Question 30

30.) Describe the four ways in which plant hormones are used to control plant growth.

Answer 30

30. )a.) Selective Herbicides - auxins are used to disrupt the natural growth of broad leaf plants.
    b. ) Growing from a cutting of root powder - auxins are agin used and they cause roots to grow.
    c. ) Producing seedless fruit - auxins and gibberellin are applied to unpollinated flowers causing the fruit to grow but the seed to not grow.
    d. ) Controlling dormancy - gibberellin will cause seeds to germinate at times of the year they wouldn’t otherwise.

Question 31

31.) What is homeostasis? and why is it important?

Answer 31

31. )a.) Homeostasis is to maintain a constant internal environment.
    b. ) This is important because it allow metabolic reactions vital for keeping you alive can continue at an appropriate rate.

Question 32

32.) Explain how body temperature is reduced when you are too hot.

Answer 32

32.) Erector muscles relax and hair lies flat, you sweat a lot as when the water evaporates it takes some of the energy from the body, blood vessels dilate to reach the cool surface of the skin to transfer energy to the surroundings.

Question 33

33. ) How does the body return the sugar levels when
    a. ) its too high
    b. ) its too low

Answer 33

33. )a.) The sugar is too high in the blood and insulin is excreted by the pancreas insulin makes the liver turn glucose into glycogen which is stored in the liver and blood sugar levels return to normal.
    b. ) The blood has a low level of sugar glucagon is excreted by the pancreas glucagon turns glycogen into glucose in the liver and glucose in the blood increases.

Question 34

34.) Explain how type 1 and 2 diabetes can be treated.

Answer 34

34. )a.) Type one diabetes is regulated by taking shots of insulin as their pancreas can’t make insulin their intake depends on how active they are and their diet.
    b. ) Type 2 diabetes is when a person becomes resistant to insulin, there are no drugs to treat it they must have a healthy and active lifestyle and lose weight.

Question 35

35.) Describe how the water potential of tissue fluid may cause the cells to shrink.

Answer 35

35. )a.) If the water in the tissue is higher than that in a cell the water will flow into the cell via osmosis and make it lysis
    b. ) If the water potential in the tissue is lower than in the cell then water from the cell moves into the tissue via osmosis and the cell becomes crenated
    c. ) If the water potential in the cell and the tissue are the same then water will move in and out of them both and the cell remain normal.

Question 36

36.) Sketch a kidney tubule and label all the parts explain how a nephron works.

Answer 36

36.) (see page 54)
Blood flows through the glomerulus at high pressure and small molecules (sugars, water, salt) are filtered in the capsule the liquid then flows through a tubule and selectively reabsorbed - all the sugar is sufficient salt and water - whatever isn’t reabsorbed forms urine, which is excreted by the kidneys.

Question 37

37.) Describe how the brain responds when it detects a rise or fall in the water level.

Answer 37

37. )a.) A rise in the water level and the brain (hypothalamus) detects a lot of water and tells the pituitary glad to stop producing ADH so the kidney reabsorbs less water.
    b. ) A fall in the water level in the blood and the brain tells the pituitary gland to produce more ADH and the kidney reabsorbs more water.

Question 38

38.) How does the kidney respond to an excess or lack of water intake?

Answer 38

38. )a.) An excess of water mean the kidney excretes more water as it is not needed by the body and the urine is less concentrated.
    b. ) A lack of water means the kidney will reabsorb more water and nine will me more concentrated also you will sweat less.

Question 39

39.) What do the circular and radial muscles do?

Answer 39

39. )a.) Circular muscles when they contract they stop a lot of light reaching in to the eye when it is bright.
    b. ) Radial muscles when they contract the pupil dilates to allow a lot of light into the eye when it is dark.