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B3 Flashcards

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1
Q

What is the nervous system made up of?

A

Neurones

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2
Q

What do sensory receptors do?

A

They can detect a change in the environment (a stimulus). Different sensory receptors detect different stimuli. eg. Receptors in the eye detect light

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3
Q

What happens to a stimulus when it is detected?

A

The information is sent as electrical impulses along sensory neurones to the central nervous system.

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4
Q

What does the CNS consist of?

A

The brain and the spinal cord.

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5
Q

What does the CNS do with an electrical impulse?

A

It sends the information along the motor neurone to an effector (muscle or gland). The effector respons accordingly - eg. a muscle may contract or a gland may produce a hormone

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6
Q

What does the axon do in a neurone?

A

Electrical impulses are passed across them.

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7
Q

Why do neurones have branched endings?

A

So that they can connect with lots of other neurones.

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8
Q

Why do axons have a fatty sheath?

A

It acts an electrical insulator, speeding up the electrical impulse.

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9
Q

Why are neurones long?

A

To speed up the impulse (one long neurone is much quicker than lots of short ones joined together).

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10
Q

What is the gap between two neurones called?

A

A synapse.

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11
Q

What chemicals diffuse from one neurone to another neurone across the synapse?

A

Neurotransmitters.

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12
Q

What is a reflex action?

A

They are an automatic response - the electrical impulses detected by the receptors are sent straight to the spinal cord so that there is no time wasted thinking about the right response. This type of action is often protective eg. moving your hand away from something hot

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13
Q

What does the cornea do?

A

It refracts (bends) light into the eye.

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14
Q

What does the iris do?

A

It controls how much light enters the pupil.

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15
Q

What does the lens do?

A

It also refracts light, focusing it onto the retina.

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16
Q

What do the ciliary muscles do?

A

They are attached to the suspensory ligaments - they work together to alter the shape of the lens

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17
Q

What does the retina do?

A

It’s covered in rods and cones which detect light. Rods are sensitive in dim light and cones are sensitive to different colours.

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18
Q

What happens to the ciliary muscles when looking at distant objects?

A

They relax, allowing the suspensory ligaments to pull tight. This pulls the lens into a less rounded shape so light is reflected less.

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19
Q

What happens to the ciliary muscles when looking at near objects?

A

They contract, which slacken the suspensory ligaments. The lens becomes a more rounded shape, so light is reflected more.

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20
Q

Why are some people long-sighted?

A

It is when people are unable to focus on near objects. This occurs when the lens doesn’t bend light enough or the eyeball is too short. The images of near objects are brought into focus behind the retina. A convex lens can fix this.

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21
Q

Why are some people short-sighted?

A

It is when people are unable to focus on distant objects. This occurs when the lens bends light too much or the eyeball is too long. The images of distant objects are brought into focus in front of the retina. A concave lens can fix this.

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22
Q

What does the cerebrum do?

A

It’s the “outer wrinkly bit”. It’s responsible for things like consciousness, intelligence, memory and language.

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23
Q

What does the hypothalamus do?

A

It’s involved in maintaining body temperature at the normal level. It also produces hormones to control the pituitary gland.

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24
Q

What does the pituitary do?

A

It’s a gland which produces many important hormones, such as those involved in the menstrual cycle.

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25
Q

What does the medulla do?

A

It controls unconscious activities like breathing and heart rate.

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26
Q

What does the cerebellum do?

A

It is responsible for muscle coordination.

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27
Q

Where are hormones produced?

A

They are chemical messengers produced in endocrine glands. Hormones are released directly into the blood and are then carried to other parts of the body in the plasma.

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28
Q

What is adrenaline?

A

It is produced by the adrenal glands. It prepares the body for “fight or flight” - standing your ground or running away. It does this by activating processes that increase the supply of oxygen and glucose to cells.

29
Q

What is negative feedback?

A

When the body detects that the level of a substance is above or below the normal level, negative feedback triggers a response to bring the level back to normal again.

30
Q

What is thyroxine?

A

It is released by the thyroid gland. It regulates metabolic rate - the speed at which chemical reactions in the body occur. It’s important for many processes, such as growth and protein synthesis. It is released in response to thyroid stimulating hormone (TSH).

31
Q

What is testosterone?

A

It is the main male sex hormone, produced in the testes. It stimulates sperm production and is important for the development of the male reproductive system.

32
Q

What is oestrogen?

A

It is the main female sex hormone. It’s produced in the ovaries. It’s involved in the menstrual cycle and promotes female sexual characteristics.

33
Q

What is progesterone?

A

It is produced by the ovaries. It helps to support pregnancy and is involved in the menstrual cycle.

34
Q

What is FSH and LH?

A

Follicle stimulating hormone and luteinising hormone - these hormones are released from the pituitary gland in the brain. They help control the menstrual cycle.

35
Q

What is the menstrual cycle?

A

The monthly sequence of events in which the female body releases an egg and prepares the uterus in case it receives a fertilised egg.

36
Q

What happens at stage 1 of the menstrual cycle?

A

Day 1 is when menstruation starts. The uterus lining breaks down and is released.

37
Q

What happens at stage 2 of the menstrual cycle?

A

The lining of the uterus builds up again, from day 4 to 14, into a thick spongy layer full of blood vessels ready to receive a fertilised egg.

38
Q

What happens at stage 3 of the menstrual cycle?

A

An egg develops and is released from an ovary at about day 14.

39
Q

What happens at stage 4 of the menstrual cycle?

A

The lining is maintained for about 14 days, until day 28. If no fertilised egg has implanted into the uterus wall by day 28, the spongy lining starts to break down again and the cycle starts over.

40
Q

What does FSH do in the menstrual cycle?

A

It causes an egg to mature in one of the ovaries and stimulates the ovaries to produce oestrogen.

41
Q

What does oestrogen do in the menstrual cycle?

A

It causes the lining of the uterus to thicken and grow. It stimulates the production of LH. It inhibits the production of FSH so that only one egg is produced in each cycle.

42
Q

What does LH do in the menstrual cycle?

A

It stimulates the release of an egg at day 14 (ovulation). It indirectly stimulates progesterone production.

43
Q

What does progesterone do in the menstrual cycle?

A

It maintains the lining of the uterus. When the level of progesterone falls and there’s a low oestrogen level, the lining breaks down. It inhibits the production of FSH and LH. A low progesterone level allows FSH to increase, and the whole cycle starts again.

44
Q

What does it mean if a person is infertile?

A

They can’t reproduce naturally. Infertility can be treated due to developments in modern reproductive technologies, which involve many hormones.

45
Q

What is auxin?

A

It is a plant hormone which controls growth at the tips of shoots and roots. It is produces in the tips and diffuses backwards to stimulate the cell elongation process which occurs in the plant cell.s

46
Q

What is phototropism?

A

A plants growth response to light

47
Q

What is gravitropism?

A

A plants growth response to gravity

48
Q

Are shoots positively or negatively phototropic?

A

Positively - they grow towards the light. When a shoot tip is exposed to light, auxin accumulates on the shaded side so that the cells on the shaded side elongate faster so that the shoot bends towards the light.

49
Q

Are shoots positively or negatively gravitropic?

A

Negatively - they grow away from gravity. When a shoot grows sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the lower side to grow faster, bending the shoot upwards.

50
Q

Are roots positively or negatively phototropic?

A

Negatively - they grow away from light. If a root grows towards light, more auxin accumulates on the shaded side. This auxin inhibits cell elongation on the shaded side, so the root bends downwards into the ground.

51
Q

Are roots positively or negatively gravitropic?

A

Positively - they grow towards gravity. A root growing sideways has more auxin in its lower side causing it to bend downwards.

52
Q

What is gibberellin?

A

It stimulates seed germination, stem growth and flowering. It stimulates the stems of plans to grow by stem elongation - this helps plants to grow tall. Auxin and gibberellin can work together to make plants grow massively.

53
Q

What is ethene?

A

It is produced by aging leaves and stimulates cells that connect the leaf to the rest of the plant to expand - this breaks the cell walls and causes the leaf to fall off the plant. It also stimulates enzymes that cause fruit to ripen.

54
Q

What are the 4 general things which plant hormones can do?

A

They can be used as selective herbicides, they can be used to grow plants from cuttings, they can be used to produce seedless fruit and to control dormancy.

55
Q

What is homeostasis?

A

It is how the body maintains a constant internal environment. The things needed to remain constant are blood glucose levels, water content, body temperature and carbon dioxide levels.

56
Q

What happens in the dermis if you are too hot?

A

Erector muscles relax, so hairs lie flat. Lots of sweat is produced. When this sweat evaporates, it transfers energy from the skin to the environment, cooling you down. Blood vessels close to the surface of the skin dilate - this is also known as vasodilation. It allows more blood to flow near the surface so it can transfer more energy into the surroundings.

57
Q

What happens in the dermis if you are too cold?

A

Erector muscles contract, so hairs stand on end to trap an insulating layer of air, which helps keep you warm. Blood vessels near the surface of the skin constrict - this is also known as vasoconstriction. It means less blood flows near the surface, so less energy is transferred to the surroundings. You also shiver (your muscles contract automatically) which requires respiration, so some energy is transferred to warm the body.

58
Q

What does insulin do?

A

Insulin is secreted by the pancreas when the blood has too much glucose in it. It causes glucose to move from the blood into the liver and muscle cells, where it the glucose is turned into glycogen. This reduces the blood glucose levels.

59
Q

What does glucagon do?

A

Glucagon is secreted when the blood has too little glucose in it. It causes glucose glycogen in the liver to become glucose, which is released into the blood by the liver. This increases the blood glucose levels.

60
Q

What is Type 1 Diabetes?

A

It is when the pancreas produces little or no insulin. This can cause a person’s blood glucose level to rise too high. People with Type 1 need insulin therapy ie. injecting insulin into the blood. As well as insulin therapy, people with Type 1 have to think about limiting their intake of food rich in simple carbohydrates and taking regular exercise.

61
Q

What is Type 2 Diabetes?

A

It is when a person becomes resistant to insulin. This can also cause blood sugar levels to rise to a dangerous level. Being overweight can increase the chance of developing Type 2. Type 2 can be controlled by having a healthy diet, exercising regularly and losing weight if necessary. There are also some drugs which improve the way that the body’s cells respond to insulin.

62
Q

What is water potential?

A

Body cells are surrounded by fluid called tissue fluid. It’s squeezed out of blood capillaries to supply cells with everything that they need. This tissue fluid will usually have a different water potential to the fluid inside a cell. This means that water will either move into the cell from the tissue fluid, or out of the cell, by osmosis.

63
Q

What is it called when a cell bursts with too much water in it?

A

Lysis

64
Q

What is called when a cell has not enough water and it shrivels up?

A

Crenation

65
Q

What do the kidneys do?

A

They balance the level of water in the body - they control how much water is lost by urine by varying the volume of urine produced and how concentrated it is. They also get rid of waste and control levels of other bodily substances.

66
Q

What are the kidneys made up of?

A

Kidney tubules (nephrons). In the kidneys, there is the cortex, the medulla, the ureter, the renal vein and the renal artery.

67
Q

What happens in a nephron in the kidney?

A

Blood flows through the glomerulus at high pressure and small molecules including water, sugar, salt and urea are filtered into the Bowman’s Capsule. The liquid then flows along the tubule and useful substances are selectively reabsorbed. All the sugar is reabsorbed, sufficient salt is reabsorbed (excess isn’t) and sufficient water is reabsorbed, according to levels of ADH.

68
Q

What does anti-diuretic hormone (ADH) do?

A

It controls the concentration of urine. It is released into the bloodstream by the pituitary gland. The brain monitors the water content of the blood and instructs the pituitary to release ADH into the blood according to how much is needed. ADH makes the nephrons more permeable so that more water is reabsorbed back into the blood.

Biology (6 decks)

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