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Flashcards in Coordination and Response Deck (71):
1

What is homeostasis?

The maintenance of a constant internal environment. Examples include body water content and body temperature.

2

What does a coordinated response require?

- A stimulus- the ‘trigger’ (a change in the internal or internal environment e.g. water levels).
- A receptor- detects the stimulus.
- An effector- carries out the response.

3

How does the hormonal (endocrine) system work?

- Signals are carried as chemical substances.
- Carried in the blood.
- Carried in the blood to the whole body, so it is possible that every cell or organ in the body is affected.
- Produced by special endocrine glands.
- Slow response.
- May have long-term effects.

4

What are hormones?

Chemical substances that are produced by endocrine glands and are carried in the blood to effector organs, which carry out the response.

5

What are the source, role and effects of adrenaline?

Source:
Produced by adrenal glands (located at the top of each kidney).
Role:
When you feel afraid or excited (or angry, sad, nervous etc.), the brain sends nerve signals to the adrenal glands causing the production of adrenaline.
Effects:
- Increase in heart rate to increase the blood and oxygen supply to muscles.
- Dilation of the blood vessels inside muscles to increase oxygen/ glucose supply.
- Triggers the breakdown of lipids to produce fatty acids and glycerol. The fatty acids are respired to provide the muscles with energy (ATP).
- Triggers the breakdown of glycogen into glucose in the liver/muscles. This glucose is respired to provide the muscles with energy (ATP).

6

What are the source, role and effects of insulin?

Source:
Produced by the pancreas.
Role:
After a meal, there are increased levels of glucose in the blood. The pancreas detects this and secretes insulin.
Effects:
Insulin stimulates the uptake of glucose into muscle cells and the conversion of glucose into glycogen in liver cells. This allows for blood glucose levels to stay within the safe limits.

7

What causes secondary sexual characteristics?

Testosterone is produced in the testes. Oestrogen is produced by the ovaries. These hormones cause the development of secondary sexual characteristics during puberty.

8

What secondary sexual characteristics are developed in males at puberty?

Pelvis remains narrow- helps with fast running.
No development of breasts.
Hair develops on pubic region and under arms as well as face (beard).
Voice box grows larger- gives a low-pitched voice.
Greater proportion of body mass becomes muscle rather than fat.

9

What secondary sexual characteristics are developed in females at puberty?

Pelvis enlarges so that hips widen- this allows the passage of a baby through the pelvic girdle during labour/birth.
Breasts grow with fat deposits- they provide milk for the newborn baby.
Hair develops on the pubic region and under arms.
Voice box remains small.
Greater proportion of body mass is maintained as fat rather than muscle- this provides a supply of nutrients during pregnancy.

10

What is the ‘journey’ of sperm?

Testis, vans deferens, prostate gland, urethra

11

What are the testes?

The site of sperm foundation, as a result of meiotic cell division inside millions of small tubules. This only happens below body temperature, which is why the testes are suspended in the scrotum- this keeps them cool.

12

What is the vans deferens?

The tube that stores sperm before ejaculation, when they are passed, along with semen produced by the seminal vesicles and prostate glands, into the urethra.

13

What is the prostate gland?

Where the vans deferens joins to the urethra. It produces semen, the fluid in which sperm swim.

14

What is the urethra?

Carries urine or sperm from the body.

15

What is the pubic bone?

Forms part of the pelvic girdle.

16

What is the bladder?

Stores urine produced by the kidneys, which is released at intervals from the body via the urethra.

17

What is the scrotum?

A sac of skin that holds the testes outside the abdominal cavity.

18

What is the lining of the uterus?

Provides a site for the development of a placenta, which allows the blood of the developing embryo to exchange materials with the mother’s blood.
In non-pregnant women, the lining is shed every month as part of the menstrual cycle.

19

What is the oviduct (Fallopian tube)?

It carries the egg released by the ovary towards the uterus. The journey may take 2-4 days.

20

What is the muscle wall of the uterus?

It stretches to allow the growth of the embryo, and later pushes the foetus out during labour.

21

What is the vagina?

Where sperm are deposited during sexual intercourse. This is also the route taken by the baby during birth.

22

What is the cervix?

The entrance to the uterus, through which sperm must swim if they are to fertilise an egg.

23

What is the ovary?

The site of egg and hormone production as part of the menstrual cycle.

24

Where is fertilisation of an egg most likely to happen?

Near the start of the oviduct, on the day after ovulation.

25

What is the role of the placenta?

The placenta allows the exchange of materials between the blood of the mother and the blood of the embryo/foetus.
Oxygen, glucose, amino acids, mineral ions and vitamins diffuse from the mother’s blood to the foetal blood. Waste products such as carbon dioxide and urea diffuse from the foetal blood to the mother’s blood.

26

What is the role of the amniotic fluid?

The embryo/foetus is surrounded by a layer of fluid called the amniotic fluid- this fluid cushions and protects the embryo/foetus and offers insulation for it, keeping the temperature constant.

27

How is the placenta adapted for he efficient exchange of substances?

The placental villa provide a large surface area to maximise diffusion of materials between the two bloodstreams.
The capillaries in the villi and the maternal capillaries are in close proximity to each other, allowing for fast and easy diffusion of substances without the two bloodstreams ever coming into contact with each other.
There is a large number of these capillaries, providing a good blood supply for the diffusion of substances.
The villi walls are very thin so there is only a short diffusion distance, allowing for faster diffusion.

28

What is FSH and what is it’s role in the menstrual cycle?

FSH (follicle-stimulating hormone) is a hormone which is released from the pituitary gland at the base of the brain. This occurs a few days after the lining of the uterus is shed. FSH stimulates the growth of a new egg cell in the ovary. A cluster of cells called a follicle develops around the egg cell.
The follicle cells produce oestrogen. For the first 14 days of the cycle, the oestrogen levels in the blood increase. This increase causes the formation of a new lining inside the uterus.

29

What is LH and what is it’s role in the menstrual cycle?

At day 14 of the menstrual cycle, the hormone LH (luteinising hormone) is produced by the pituitary gland. LH causes the release of the egg from it’s follicle in the ovary. This is known as ovulation. The released egg is moved into and along the fallopian tube by tiny hairs (cilia).
LH also causes the follicle cells left in the ovary to switch from producing oestrogen to producing progesterone. Therefore, progesterone levels in the blood increase promoting further growth of the uterus lining.

30

What are the differences between the nervous system and the endocrine system?

Nervous:
- Signals are electrical impulses.
- Carried along nerve cells.
- Carried along nerve axons to a specific site, so that only a single cell or organ is affected.
- Carried from receptors in sense organs, along nerves to the CNS, then to the effector.
- Fast response.
- Effects last a short time.

Endocrine:
- Signals carried as chemical substances.
- Carried in the blood.
- Carried in the blood to the whole body, so it is possible that every cell or organ in the body is affected.
- Produced by special glands (endocrine glands).
- Slow response.
- May have long-term effects.

30

What does the nervous system consist of?

- The central nervous system (CNS): brain and spinal chord.
- The peripheral nervous system (PNS): all of the other nerves connecting the CNS to the rest of the body.

31

Describe the nerve pathway (what happens?!).

1. Stimulus- changes in the internal or external environment.
2. Receptor- detects the stimulus.
3. Sensory neurone- carries electrical impulses within the CNS.
4. Relay neurone- carries electrical impulses within the CNS.
5. Motor neurone- carries electrical impulses from the relay neurone in the CNS to the effector (eg. Muscle or gland).
6. Effector- carries out response.
7. Response (rapid).

32

Describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object.

1. A receptor in the finger detects the pain/heat. Electrical impulses are carried along the sensory neurone to the CNS.
2. A relay neurone in the spinal chord carries electrical impulses and connects the sensory neurone to the motor neurone.
3. A motor neurone carries impulses to the effector (muscle), causing it to contract so that the finger is quickly withdrawn from the flame.

33

What are neurotransmitters?

They are chemical substances that help carry information from one neurone to another.

34

What is the role of neurotransmitters at synapses?

1. The arrival of an electrical impulse at the synapse causes the release of neurotransmitter molecules (which are stored in vesicles) into the synaptic gap.
2. Neurotransmitter molecules diffuse across the synaptic gap from neurone A to neurone B.
3. Neurone B then creates an electrical impulse as a result. This will continue to travel along this neurone.

35

How is body temperature regulated?

Receptors in the hypothalamus monitor the temperature of the blood. If the temperature rises above normal, a cooling response will occur. This involves:
- Sweating.
- Vasodilation.
- Flattening of hairs on the skin.

36

How does sweating cool you down?

Sweat glands become more active and produce more sweat if you are too hot. This sweat evaporates from the surface of the skin, drawing heat away with it and therefore cooling the skin.

37

How do blood vessels change when your body temperature changes?

Too hot:
The diameter of arterioles near the surface of the skin increases (vasodilation), allowing increased blood flow through capillaries under the skin surface. More heat can then be lost through radiation, cooling the skin.

Too cold:
Conversely, a fall in temperature will cause a constriction of arterioles (vasoconstriction), decreasing blood flow through capillaries under the skin surface. Less heat can then be lost through radiation.

38

How do hairs on the skin help to regulate body temperature?

Too hot:
Lie flat on the skin and allow cool moving air closer to the skin surface.

Too cold:
A fall in temperature will cause hair muscles in the skin to contract, so the hairs are raised upwards erect. This traps a layer of warm air, insulating and heating the skin. It also prevents cool moving air from reaching the skin surface.

39

What is the eye?

The eye is a specialised sense organ (contains receptors) that allows us to detect the stimulus of light.

40

What is the ciliary body, and what is its function?

Muscles that pull on the suspenders ligaments holding the lens, to change its shape for focusing.

41

What are the suspensory ligaments, and what is their function?

Attach lens to ciliary body, holding the lens in place.

42

What is the retina, and what is its function?

Layer of light sensitive receptor cells, with connections to the optic nerve. Includes two types of receptor cells: rods (detect black and white) and cones (detect colour).

43

What is the sclera, and what is its function?

Strong white wall of eyeball.

44

What is the lens, and what is its function?

Transparent, focuses light rays.

45

What is the fovea, and what is its function?

Central region of retina providing detailed, colour vision as it contains densely packed cones.

46

What is the vitreous humour, and what is its function?

Jelly-like liquid behind lens.

47

What is the optic nerve, and what is its function?

Carries nerve impulses to the brain.

48

What is the blind spot, and what is its function?

A region lacking receptor cells, where the optic nerve leaves the eye.

49

What is the choroid, and what is its function?

A pigmented layer of tissue that prevents reflection of light rays inside the eyeball.

50

What is the iris, and what is its function?

Varies the diameter of the pupil, which helps to regulate the amount of light entering the eye.

51

What is the aqueous humour, and what is its function?

Watery liquid between the cornea and lens.

52

What is the pupil, and what is its function?

Aperture (hole) through which light rays pass into the back of the eye.

53

What is the cornea, and what is its function?

Transparent front to the eyeball, allowing rays of light into the eye.

54

How does light enter the eye?

Light rays from an object pass into the eye through the transparent cornea. The cornea is covered by a thin sheet of protective cells called the conjunctiva.
The light rays refract (bend) as they enter the front of the eye (part of the focusing process).

55

How does the eye focus light (describe accommodation)?

The lens focuses the light. The lens is suspended by ligaments attached to the ciliary body. The changes in the shape of the lens allow the eye to focus on nearer and more distant objects, and these changes are brought about by contraction or relaxation of the ciliary muscles. This process is known as accommodation.

56

How does the eye focus on distant objects?

- Ciliary muscles relaxed.
- Tension on the suspensory ligaments increases (pulled tight).
- Lens pulled thin and flat.

57

How does the eye focus on near objects?

- Ciliary muscles contracted.
- The suspensory ligaments become slack (do not pull on the lens).
- Lens spring back to be fatter (more spherical).

58

How does the eye control the amount of light entering it?

The iris (a coloured ring of muscle with a hole in the middle: the pupil) regulates the total quantity of light entering the eye.
Light rays must pass through the pupil before they enter the lens.
The diameter of the pupil can vary depending on the state of the two types of muscles in the iris: the circular (sphincter) and radial (dilator) muscles.

59

What happens to the eye in bright light?

The circular muscle fibres in the iris contract and the radial muscles relax. As the circular muscles shorten, they press upon the inner edge of the iris, causing the pupil to become smaller (constrict), and less light to enter the eye.

60

What happens to the eye in dim light?

The radial muscle fibres of the iris contract and the circular muscles relax. As the radial muscles shorten, they pull on the inner edge of the iris, widening the pupil (dilation) and allowing more light to enter the eye.

61

Why does the pupil constrict faster than it dilates?

Large amounts of light are more dangerous for the eye than small amounts of it. It is therefore more important for the pupil to be reduced in size (constrict) rapidly to prevent too much light reaching the lens than being able to dilate rapidly.

62

What are tropisms?

Tropisms are directional growth responses that plants carry out in reaction to specific stimuli. If the growth is towards the stimulus, the tropism is positive. If the growth is away from the stimulus, the tropism is negative.

63

What are the geotropic and phototropic responses of roots and stems?

Stimulus: gravity
Name of response: positive geotropism
Example: seedling roots grow down, towards the centre of the Earth.

Stimulus: gravity
Name of response: negative geotropism
Example: seedling shoots grow up, away from the centre of the Earth.

Stimulus: light
Name of response: positive phototropism
Example: seedling shoots grow towards a light source

Stimulus: light
Name of response: negative phototropism
Example: seedling roots grow away from a light source


64

What are auxins?

Plant growth regulators

65

Describe positive phototropism when there is light all around.

Auxins are produced in the shoot tip, and transported down the shoot. These auxins cause the cells dividing in the tip to elongate. If the concentration of auxins is equal on all sides of the growing shoot, the cells on all sides will elongate at the same rate, so the shoot will grow in a straight line.

66

Describe positive phototropism when there is light shining from the left or right of the plant.

Auxins are produced in the shoot tip, and transported down the shoot. If light is shining onto the plant from the right, the auxins will be distributed unevenly. A higher concentration of auxins will build up on the left side of the growing shoot. The cells here will therefore elongate at a faster rate than on the right side, causing the shoot to bend right (towards the light). If light is shining from the left, the opposite will happen and the shoot will bend to the left.

67

Why do plant roots demonstrate positive geotropism and plant shoots demonstrate negative geotropism?

Plant roots grown downwards (positive geotropism) to obtain water and mineral ions and help them anchor the plant so that it is not easily uprooted.
Plant shoots grow upwards (negative geotropism) to reach the light and carry out photosynthesis.

68

Why do plant shoots grow upwards in terms of auxins?

The auxins produced in the horizontal shoot tip become concentrated on the lower side (because of gravity). The auxins here cause the cells on the lower side to elongate and grow, causing the tip to grow upwards (negative geotropism).

69

Why do plant roots grow downwards in terms of auxins?

The auxins produced in the horizontal root tip become concentrated on the lower side. The auxins here inhibit/prevent elongation and growth of cells on the lower side, causing the tip to grow downwards (positive geotropism).

70

What is a coleoptile?

A coleoptile is the first shoot that emerges from certain plants (eg. Wheat, maize, grasses etc.).