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GCSE BIOLOGY > 5. Homeostasis and Response > Flashcards

5. Homeostasis and Response Flashcards

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1
Q

What is Homeostasis?

A

Homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular functions

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2
Q

Give examples of conditions maintained by Homeostasis in the body :

A

•Blood glucose concentration
•Body temperature
• Water levels

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3
Q

What two types of responses are used in body control systems?

A

Nervous and chemical

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4
Q

What three components do all control systems have?

A

•Receptors
•Coordination centre
•Effectors

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5
Q

What is the function of a receptor?

A

Receptors detect changes in the environment (stimuli)

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6
Q

What is the function of a coordination centre ?

A

Coordination centres obtain and process information from receptors

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7
Q

What is the function of a effector ?

A

Effectors (muscle of glands) bring about responses to stimuli

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8
Q

What is the function of the nervous system?

A

The nervous system allows the body to react to its surroundings and coordinate an appropriate response

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9
Q

How does stimulus lead to a response being carried out by the body ?

A

• Stimulus is converted into an electrical impulse by the receptors.
• The electrical impulse passes along sensory neurones to the central nervous system (CNS).
• The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response.

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10
Q

What sequence of events describes how the nervous system works?

A

Stimulus → receptor → coordinator → effector → response

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11
Q

What is a reflex action ?

A

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain.

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12
Q

Why are relfex actions important?

A

Reflex actions aid sruvival by preventing harm to the body

E.g. touching a hot object

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13
Q

Describe how a reflex action occurs via a reflex arc

A

-The stimulus is detected by a receptor
-An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
• At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which
passes along the relay neurone.
• The same process occurs at a synapse between a relay neurone and a motor neurone.
• At the effector, an appropriate response is carried out.

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14
Q

What is the difference between a reflex pathway and a conscious pathway?

A

Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain. In a conscious pathway, the coordination centre is in the conscious part of the brain.

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15
Q

Give the name of the body’s coordination system which involves hormones

A

The endocrine system

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16
Q

What is a hormone?

A

A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a response.

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17
Q

What type of organ secretes hormones?

A

Glands

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18
Q

Which gland controls many other glands in the body

A

The pituitary gland

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19
Q

Why is the pituitary gland considered a ‘master gland ‘?

A

It secretes a wide range of hormones, some of which may stimulate other endocrine glands.

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20
Q

What is the role of the pituitary gland in the endocrine system ?

A

• Secretes human growth hormone - controls human growth.
• Stimulates the thyroid gland.
• Stimulates ovulation and the production of oestrogen in the ovaries.
• Stimulates the production of sperm and testosterone in the testes.

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21
Q

What is the role of the thyroid gland in the endocrine system ?

A

Secretes the hormone thyroxine - controls metabolism, heart rate and body temperature.

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22
Q

What is the role of the pancreas in the endocrine system?

A

Secretes the hormone insulin - controls blood glucose levels

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23
Q

What is the role of the adrenal gland in the endocrine system ?

A

Secretes adrenaline - controls the body’s
‘fight or flight’ response.

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24
Q

What is the role of the ovaries in the endocrine system ?

A

Secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics.

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25
Q

What is the role of the testes in the endocrine system ?

A

Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics.

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26
Q

Which organ monitors and controls blood glucose concentration ?

A

The pancreas

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27
Q

How does the pancreas respond when blood glucose levels are too high ?

A

The pancreas secretes the hormone insulin.
Insulin binds to receptors on the liver and muscles, causing excess glucose to be converted into glycogen and stored.

28
Q

How does the pancreas respond when blood glucose levels are too low ?

A

The pancreas secretes the hormone glucagon. Glucagon binds to liver cells, causing glycogen to be converted into glucose and released into the blood.

29
Q

How is blood glucose concentration controlled using a negative feedback loop ?

A

When the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas.
• The action of either hormone (insulin or glucagon) helps bring back the concentration to the correct level .

30
Q

What is Type 1 diabetes?

A

Type 1 diabetes is an autoimmune disorder in which the pancreas does not produce sufficient insulin to control the blood glucose concentration.
As a result, blood glucose levels are often very high, leading to excessive urination, tiredness and weight loss.

31
Q

How can type 1 diabetes be treated ?

A

• Insulin injections before meals - allows glucose to be converted into glycogen.
• Limiting carbohydrate intake.
• Attempts using pancreas and pancreatic cell transplants; investigations into genetic engineering of pancreatic cells.

32
Q

What is type 2 diabetes ?

A

Type 2 diabetes is a disorder in which the body’s cells stop responding to insulin, leading to an uncontrolled blood glucose concentration. Its onset is linked with increasing age and obesity.

33
Q

How can type 2 diabetes be treated ?

A

• Following a carefully-controlled diet
• Doing regular exercise
• Losing weight
• Use of drugs which increase insulin production and effectiveness

34
Q

What is the function of reproductive hormones during puberty?

A

• Males: cause the development of secondary sexual characteristics.
• Females: cause the development of secondary sexual characteristics and the maturation of eggs.

35
Q

What is the main male reproductive hormone ?

A

The main male reproductive hormone is testosterone, which is produced by the testes and controls sperm production.

36
Q

What is the main female reproductive hormone ?

A

The main female reproductive hormone is oestrogen, which is produced by the ovaries and is involved in the menstrual cycle.

37
Q

What is the menstrual cycle ?

A

The menstrual cycle is the monthly cycle of physiological changes that occur in females, involving the shedding of the uterus lining (menstruation) and ovulation.

38
Q

Describe the events of the menstrual cycle

A

• Uterus lining thickens and eggs begin to mature in the ovaries.
• An egg is released from one of the ovaries (ovulation)
- uterus lining remains thick.
• If the egg is fertilised, pregnancy may occur. If not, both the egg and the uterus lining are shed during menstruation.

39
Q

what is ovulation ?

A

Ovulation is the release of a mature egg from the ovaries, which occurs approximately every 28 days.

40
Q

Name the four main hormones involved in the menstrual cycle

A

• Oestrogen
• Progesterone
• Follicle stimulating hormone (FSH)
• Luteinising hormone (LH)

41
Q

What is the role of FSH in the menstrual cycle ?

A

FSH is secreted by the pituitary gland. It controls the maturation of eggs within the ovaries (inside a follicle) and triggers the production of oestrogen by the ovaries.

42
Q

What is the role of oestrogen in the menstrual cycle ?

A

Oestrogen is produced by the ovaries and released due to the action of FSH - it causes the regrowth of the uterus lining.
It triggers the production of LH and restricts the release of more FSH.

43
Q

What is the role of LH in the menstrual cycle ?

A

LH is produced in the pituitary gland as a result of oestrogen. Its release triggers ovulation.

44
Q

What is the role of progesterone in the menstrual cycle ?

A

Progesterone is secreted from the follicle of the ovary. It sustains the uterus lining and inhibits FSH and LH.

45
Q

What is contraception ?

A

Contraception refers to any method of preventing pregnancy

46
Q

What are the two type of oral contraceptives ?

A

• Combined contraceptive pill (contains oestrogen and progesterone).
• Mini pill (contains only progesterone).

47
Q

How does the contraceptive pill prevent pregnancy ?

A

• Inhibits FSH - eggs do not mature.
• Prevents the development of the uterus lining - eggs cannot implant.

48
Q

What is the contraceptive patch ?

A

• Contains both oestrogen and progesterone.
• It is a patch that is placed onto the skin for 7 days at a time.

49
Q

What is the Contraceptive implant ?

A

A small rod inserted under the skin which continuously releases the hormone progesterone - lasts for 3 years.

50
Q

What is the contraceptive injection ?

A

An injection containing the hormone progesterone - lasts for approximately 3 months.

51
Q

What is the IUS

A

The IUS (intrauterine system) is a small plastic device that is inserted into the uterus. It releases progesterone

52
Q

What is the IUD ?

A

The IUD (intrauterine device) is a small copper-containing device inserted into the uterus, which prevents the implantation of embryos.

53
Q

What is a spermicide?

A

A spermicide is a chemical that kills or immobilises sperm cells - however, they are not very effective, and work better when combined with barrier methods.

54
Q

What is a barrier method of contraception ?

A

A barrier method of contraception involves a physical separation between the sperm and the egg. They
include:
• Condoms - thin sheath worn on the penis or inside the vagina - protects against STIs but may tear/break.
• Diaphragms - a thin cap placed over the cervix - prevent entry of sperm.

55
Q

What surgical methods of contraception are available?

A

Sterilisation - in males, the sperm ducts are tied (vasectomy) and in females, the oviducts are tied.

56
Q

What is abstinence?

A

Abstinence is the practice of not having sex, which also avoids pregnancy. Some people abstain from sex around the time of ovulation - this is known as the rhythm method, but it is quite unreliable.

57
Q

How do fertility drugs increase the chance of pregnancy?

A

Many fertility drugs contain FSH - which stimulates oestrogen production and the maturation of eggs in the ovary. They also contain LH which triggers ovulation.

58
Q

What is IVF

A

IVF (in vitro fertilisation) is type of fertility treatment:
• Mother is given FSH and LH - stimulates maturation of eggs and ovulation.
• Eggs are fertilised using sperm in a laboratory - develop into embryos.
• 1 or 2 embryos are inserted into the mother’s womb.

59
Q

What are the advantages of fertility treatment ?

A

• Allows infertile couples to have children
• Can store a woman’s eggs for later

60
Q

What are the disadvantages of fertility treatment?

A

• It can be a very expensive process.
• It has a low success rate - especially for older couples.
• Increases chance of multiple pregnancies - dangerous for mother and babies.
• Side effects of fertility drugs.

61
Q

What is negative feedback ?

A

Negative feedback is a type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level.

62
Q

What is thyroxine?

A

Thyroxine is a hormone released by the thyroid gland. Its release is triggered by the thyroid stimulating hormone (TSH). Thyroxine controls the body’s metabolic rate, growth and development.

63
Q

How is the release of thyroxine controlled by negative feedback ?

A

• Levels of blood thyroxine falls - detected by receptors in the brain.
• Pituitary gland releases more TSH.
• More thyroxine produced and released by the thyroid gland.
• Blood thyroxine level returns to normal.

64
Q

What is adrenaline ?

A

Adrenaline is a hormone secreted by the adrenal gland in times of stress. It is responsible for the ‘fight or flight response’.

65
Q

What are the effects of adrenaline?

A

• Increase in heart and breathing rate - delivers oxygen and glucose to the body.
• Stored glycogen converted to glucose.
• Dilation of pupils.
• Increased mental awareness.
• Blood diverted away from digestive system to muscles

66
Q

What is infertility

A

Being unable to concieve

GCSE BIOLOGY (15 decks)

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