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Biology > Unit 5 - Homeostasis & Response > Flashcards

Unit 5 - Homeostasis & Response Flashcards

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 function.

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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 centres
● 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 an effector?

A

Effectors (muscles or 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 a 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 reflex actions important?

A

Reflex actions aid survival by preventing
harm to the body.

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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.

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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.

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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.

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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

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 types 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.
● Increases the thickness of cervical mucus -
immobilises sperm cells.

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 which
thickens cervical mucus and prevents the
build-up of the uterine lining.

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

How do plant shoots show negative
gravitropism?

A

● In a horizontal shoot, auxin accumulates in the
lower side due to gravity.
● Cells on the lower side of shoot grow more, causing
the shoot to bend away from the direction of gravity.
● As a result, more light is usually available for
photosynthesis.

67
Q

How do plant roots show positive
gravitropism?

A

● In a horizontal root, auxin accumulates in the
lower side, causing cells to grow less.
● The root bends in the direction of gravity
● As a result, more water and nutrients are
available to the plant roots.

68
Q

What are gibberellins?

A

Gibberellins are a type of plant hormone
involved in seed germination.

69
Q

What is ethene?

A

Ethene is a type of plant hormone
involved in cell division and ripening.

70
Q

What are the uses of auxins?

A

● Weedkillers - auxin causes cells to grow at a
rapid rate, causing plant death.
● Rooting powder - auxin causes new plant to
grow very quickly.
● Tissue culture - auxin promotes growth of
roots and shoots.

71
Q

What are the uses of ethene?

A

● Control of food ripening in the food industry -
allows fruit to be ripened just before they are
sold.

72
Q

What are the uses of gibberellins?

A

● Termination of seed dormancy
● Promotion of flowering
● Increase of fruit size

Biology (7 decks)

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