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GCSE Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

Homeostasis

A

The regulation of conditions to maintain a stable internal environment, in response to internal and external conditions

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2
Q

Stimulus

A

A change in the environment

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3
Q

Receptor

A

An organ, tissue or cell that detects a stimulus

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4
Q

Coordination Centre

A

Receives receptor information, processes it and initiate a response, (brain, spinal cord)

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5
Q

Effector

A

An organ, tissue or cell that produces a response (either muscles contracting or glands secreting a hormone)

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6
Q

Synapse

A

A tiny gap between 2 nerve cells which signals must cross

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7
Q

Sensory Neurones

A

Carry impulses from the receptors to the CNS

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8
Q

Motor Neurones

A

Carry impulses from the CNS to the effectors

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9
Q

Nervous System Order

A

Stimulus - Receptors - Sensory Neurones - Coordination Centre (found in CNS) - Motor Neurones - Effector - Response

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10
Q

Reflex Arc

A

Nerve Pathway that underlies unconscious reflexes

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11
Q

Reflex Action

A

An automatic, rapid response to a stimulus which minimises any harm to the body

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12
Q

Cerebrum (Cerebral Cortex)

A

Responsible for:
- Consciousness
- Intelligence
- Memory
- Language
- Senses (sight, hearing, taste, etc)

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13
Q

Cerebellum

A

Responsible for:
- Balance
- Muscle coordination

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14
Q

Hypothalamus

A

Responsible for:
- Regulating body temperature
- Sends signals to pituitary gland

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15
Q

Medulla

A

Responsible for:
- Unconscious activities (e.g. breathing, heart rate)

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16
Q

How do scientists study brain?

A
  • By studying people with brain damage
  • By electrically stimulating different parts of the brain
  • MRI scans
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17
Q

How do scientists study brain damage?

A

For example, if someone had a stroke which caused hearing loss, scientists would know the part of the brain responsible for hearing is damaged

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18
Q

How do scientists electrically stimulate different parts of the brain?

A
  • Brain is stimulated using electrodes
  • Stimulating certain areas creates certain reactions from the body
  • From this scientists can tell what that part of the brain is responsible for
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19
Q

How do MRI scans work?

A
  • Show details of brain structure and function
  • Patients are asked to perform various tasks
  • By looking at the scan, scientists can see which parts of the brain are active when the task is carried out
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20
Q

Risks of treating the brain

A
  • Brain surgery can cause damage or side effects that can ruin a patient’s quality of life
  • Surgery risks (tumours, infection, brain trauma)
  • Brain is very complex and fragile so treating brain damage is difficult
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21
Q

Cornea

A
  • Refracts (bends) light as it enters the eye
  • Transparent to let light enter
  • Contains no blood vessels, O2 diffuses through it
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22
Q

Iris

A

Controls how much light enters the eye

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23
Q

Pupil

A

Gap in the centre of the iris that allows light to pass through to the lens

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24
Q

Lens

A

Changes shape to further refract light so it focuses on the retina

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25
Q

Retina

A

Contains light receptors that help to see colour

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26
Q

Optic Nerve

A

Carries impulses between the eye and the brain

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27
Q

Sclera

A

Tough white outer layer of the eye that protects the eye from injury

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28
Q

Iris Reflex in bright light

A
  • Reflex constricts the pupil (makes it smaller)
  • Allows less light to pass through to the lens
  • Prevents eye damage
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29
Q

Iris Reflex in low light

A
  • Reflex dilates the pupil (makes it bigger)
  • Allows more light to pass through to the lens
  • Allows us to see more clearly in the dark
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29
Q

Iris Reflex in low light

A
  • Reflex dilates the pupil (makes it bigger)
  • Allows more light to pass through to the lens
  • Allows us to see more clearly in the dark
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30
Q

Near Objects

A
  • Ciliary Muscles contract
  • Suspensory Ligament
    slackens
  • Lens thickens and strongly refracts light rays
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31
Q

Distant Objects

A
  • Ciliary Muscle relaxes
  • Suspensory Ligament pulled taught
  • Lens thins and slightly refracts light rays
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32
Q

Hyperopia (Long-Sightedness)

A
  • Light rays don’t refract enough
  • Image appears behind the retina
  • Can’t focus on nearby objects
  • Fixed using a convex lens
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33
Q

Myopia (Short-Sightedness)

A
  • Light rays refract too much
  • Image appears in front of the retina
  • Can’t focus on distant objects
  • Fixed using a concave lens
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34
Q

Other ways to correct vision

A
  • Hard and soft contact lenses
    -Laser surgery to change the shape of the cornea
  • Replacement lens in
    the eye
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35
Q

Thermoregulation

A

The regulation of internal body temperature

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36
Q

Where is the thermoregulatory centre found?

A

In the hypothalamus

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37
Q

How do our bodies warm us up?

A
  • Vasoconstriction (prevents heat loss through skin)
  • Hairs stand up (trap insulating layer of air)
  • Shivering (heat energy is released to warm us up)
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38
Q

How do our bodies cool us down?

A
  • Vasodilation (causes heat energy loss)
  • Erector muscles relax (hairs lie flat)
  • Sweat - a mix of water and urea (evaporates and carries heat energy with it)
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39
Q

Pituitary Gland

A

Located below the centre of the brain and secretes many hormones

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40
Q

Thyroid

A
  • Produces thyroxine
  • Thyroid regulates metabolism
  • Found in the neck
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41
Q

Adrenal Glands

A
  • Produce adrenaline (released during fight or flight)
  • Increases heart rate
  • Above the kidneys
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42
Q

Pancreas

A
  • Produces insulin + glucagon (lowers/raises blood glucose concentration)
  • In front of the kidneys
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43
Q

Testes

A
  • Only in males
  • Produces testosterone (controls puberty)
  • Produces male gametes (sperm)
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44
Q

Ovaries

A
  • Only in females
  • Produces oestrogen (controls puberty + menstrual cycle)
  • Produces female gametes (eggs)
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45
Q

Differences between Endocrine and Nervous Systems

A

Endocrine:
- Relies on hormones that travel in the bloodstream
- Slower
- Hormones last longer
- More general

Nervous:
- Relies on electrical impulses that travel through neurones
- Faster
- Don’t last long
- More precise

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46
Q

How does insulin lower
blood glucose levels?

A
  • Insulin binds to receptors on muscle + liver cells
  • Those cells take in glucose and store it as glycogen
  • This lowers BGC back to normal
47
Q

How does glucagon raise blood glucose levels?

A
  • Insulin binds to liver receptor cells
  • Those cells break down glycogen into glucose and release it into the bloodstream
  • This raises BGC back to normal
48
Q

Type 1 Diabetes

A
  • Starts at and early age but affects are lifelong
  • The pancreas stops producing insulin so BGC becomes to high and isn’t lowered
49
Q

Type 2 Diabetes

A
  • Happens at older age
  • The body stops responding to insulin so cells don’t take in glucose
50
Q

Type 1 Diabetes Treatment

A

Insulin injections into the abdomen/thigh

51
Q

Type 2 Diabetes Treatment

A
  • Healthy, low sugar diet
  • Lots of exercise
52
Q

Role of the kidneys

A
  • Filter the blood and remove any waste products from it
  • Regulate levels of ions + water
53
Q

Deamination

A
  • Where excess amino acids are converted into fats and carbohydrates for storage
  • Takes place in the liver
54
Q

Where is urea made?

A

In the liver during deamination

55
Q

How does water leave the body?

A
  • Sweat
  • Through the lungs when breathing
  • Through urine
56
Q

Why is water regulation important?

A
  • Cells lose/gain water depending on how much water is in the body
  • An excess of water means it enters the cells through osmosis and damages them or causes them to burst
  • A lack of water means water leaves the cell making it flaccid
57
Q

How do the kidneys filter the blood?

A
  • Selective reabsorption
  • As blood passes through the kidney, tubules absorb all small molecules
  • Things that are good for the blood (all glucose and some water) are reabsorbed back into the blood
  • Urea isn’t reabsorbed but excreted
58
Q

What happens when there is too little water in the bloodstream?

A
  • The hypothalamus signals the pituitary gland to release more ADH
  • ADH enters the kidneys and alerts the tubules to reabsorb more water
  • Less urine is produced
59
Q

What happens when there is too much water in the bloodstream?

A
  • The hypothalamus doesn’t signal the pituitary gland to release ADH
  • Less ADH enters the kidneys so less water is reabsorbed
  • More urine is produce
60
Q

Kidney system

A
  • Blood enters through renal artery and exits through renal vein
  • Kidneys produce urine
  • Urine passes though the ureters and is stored in bladder
  • Excreted through urethra
61
Q

Consequences of kidney failure

A
  • Waste substance aren’t removed from the body
  • Ion and water levels aren’t regulated
  • Causes illness and death if untreated
62
Q

Dialysis

A

Medical treatment where blood is removed, filtered and put back in the body

63
Q

How does dialysis work?

A
  • Blood passes through dialysis machine and makes contact with dialysis fluid
  • Blood and fluid separated by partially permeable membrane
  • Ions, water and glucose diffuse in and out of the blood so a good concentration of all is created in the blood
64
Q

Why is dialysis fluid constantly replaced?

A
  • To created a constant concentration gradient
  • Without one, eventually the molecules wouldn’t diffuse in and out of the blood
65
Q

Disadvantages of dialysis

A
  • Treatment is time consuming
  • Dialysis can cause blood clots and infection
  • Dialysis is a life process (has to be done regularly for life)
66
Q

Kidney transplant

A

Surgical procedure where the kidney is replaced

67
Q

Disadvantages of kidney transplants

A
  • Organ may be rejected by recipient’s immune system
  • Drugs are given to stop this but it weakens the immune system and increases chance of illness
  • Surgical risks (surgery could go wrong)
  • Lack or organ donors
68
Q

Puberty

A

Period where adolescents start to develop secondary sexual characteristics

69
Q

What are the 4 stages of the menstrual cycle?

A
  • Menstruation
  • Uterus lining develops
  • Ovulation
  • Uterus lining maintained
70
Q

Menstruation

A
  • Between days 0-7
  • Uterus lining breaks down
  • Bleeding as a result
71
Q

Lining builds up

A
  • Between days 7-14
  • Lining becomes a thick spongy layer with lots of blood vessels in it
  • This prepares the lining for a fertilised egg
72
Q

Ovulaltion

A
  • On day 14
  • Egg is released from the ovary
73
Q

Lining is maintained

A
  • 14-28 days
  • If no egg has been fertilised by day 28, menstruation occurs (cycle repeats until fertilised egg)
  • If an egg has been fertilised before day 28, it implants itself into the womb to develop into a foetus
74
Q

Follicle Stimulating Hormone

A
  • Causes egg to mature in ovary
  • Stimulates oestrogen
  • Produced in pituitary gland
75
Q

Oestrogen

A
  • Repairs, thickens and maintains uterus lining
  • Stimulates LH
  • Inhibits FSH
76
Q

Luteinising Hormone (LH)

A
  • Triggers ovulation
  • Produced in the pituitary gland
77
Q

Progesterone

A
  • Maintains uterus lining
  • Produces mucus in the cervix
  • Inhibits LH and FSH
78
Q

Contraception

A

Any method used to prevent pregnancy

79
Q

Hormonal Methods

A

Rely on the release of oestrogen/progesterone to prevent the release of an egg

80
Q

Oestrogen Pill

A
  • Taken everyday to inhibit FSH
  • Inhibiting FSH means no egg is matured or released
81
Q

Progesterone Pill

A
  • Releases progesterone
  • This produces a thick mucus in the cervix
  • Sperm can’t reach the egg
82
Q

Combined Pill

A
  • Contains progesterone and oestrogen
  • Very effective but has side effects
  • E.g. headaches, nausea
83
Q

Contraceptive Patch

A
  • Placed on the upper arm
  • Releases progesterone and oestrogen
  • Lasts 1 week
84
Q

Contraceptive injection

A
  • Progesterone is injected in the upper arm
  • Lasts 2-3 months
85
Q

Contraceptive Implant

A
  • Placed under the skin in the arm
  • Slowly releases progesterone
  • Lasts 3 years
86
Q

IUD (Intrauterine Device)

A
  • Placed inside the uterus
  • Releases progesterone
  • Lasts over 3 years
87
Q

Non-Hormonal Devices

A

Prevents the sperm from reaching the egg and fertilising it

88
Q

Copper IUD (Copper Coil)

A
  • Prevents sperm from surviving in the uterus by killing them
  • Lasts over 3 years
89
Q

Condoms

A
  • Acts a barrier and traps sperm
  • Only form of contraception that protects against STD’s as well
90
Q

Diaphragm

A
  • Fits over the cervix
  • Blocks sperm from entering the uterus
  • Unreliable so is used with spermicides
91
Q

Sterilisation

A
  • Cutting the fallopian tubes (women)
  • Cutting the sperm ducts (men)
92
Q

Natural methods

A
  • Intercourse only at certain times of the month
  • Withdrawing before ejaculation
93
Q

Abstinence

A
  • Refraining from intercourse
  • Only method that has a 100% success rate
94
Q

Infertility Problem

A
  • Low production of FSH so egg doesn’t mature properly or at all
  • FSH and LH are given in pill form to mature and release eggs
95
Q

How IVF (In Vitro Fertility) works

A
  • FSH and LH are given in pill form to mature and release eggs
  • Eggs are collected and fertilised with father’s sperm in a lab
  • Fertilised eggs are placed in an incubator and grow into embryos
  • One or more embryos are inserted into the uterus to grow into foetuses
96
Q

Pro of IVF

A
  • Allows infertile couples to have children
97
Q

Cons of IVF

A
  • Doesn’t always work (low success rate)
  • Side effects (e.g. abdominal pains, vomiting)
  • Multiple embryos can lead to multiple unwanted pregnancies
  • Leads to higher risks of complications (stillbirths, miscarriage)
98
Q

Ethical issues

A
  • IVF leads to destruction of unused embryos that had potential of life
  • Could lead to designer babies
99
Q

Adrenaline

A
  • Produced in the adrenal glands during ‘fight or flight’ response, when you’re scared, stressed or are about to exercise
  • Prepares the body for physical activity
100
Q

Adrenaline Impacts

A
  • Increased heart rate
  • Increased blood flow
  • Increased blood flow to the muscles
  • Increases glucose breakdown by stimulating the liver to breakdown glycogen
101
Q

Thyroxine

A
  • Produced y the adrenal glands in the neck
  • Main role is to increase metabolic rate
  • Pituitary gland produces TSH which stimulates the thyroid to produce thyroxine
102
Q

What happens if thyroxine levels are too low?

A
  • The pituitary gland produces more TSH
  • This stimulates the thyroid to produce more thyroxine so levels increase to normal
103
Q

What happens if thyroxine levels are too high?

A
  • Thyroxine inhibits the production of TSH form the pituitary gland
  • Less TSH means less thyroxine is being produced from the thyroid
  • Levels fall to normal
104
Q

Phototropism

A

Plant response to the stimulus of light

105
Q

Geotropism/Gravitropism

A

Plant response to the stimulus of gravity

106
Q

Auxins

A
  • Control growth at the ends of shoots and roots of a plant
  • Stimulates growth in the shoots
  • Inhibits growth in the roots
107
Q

Shoots

A
  • Positively phototropic (grow towards the light)
  • Negatively geotropic (grow away from the ground against gravity)
108
Q

Direction of growth in plant shoot

A
  • Towards the sun
  • Auxin accumulates in the shaded side of a plant
  • Auxin stimulates growth in shoots so shaded side will grow at a faster rate - towards the light
109
Q

Roots

A
  • Negatively phototropic (grow away from light)
  • Positively geotropic (grow towards the ground)
110
Q

Direction of growth in plant roots

A
  • Constantly curves upwards and downwards
  • Auxin accumulates on the lower side of root
  • Auxin inhibits growth in roots so lower side grows at a slower rate and curves downwards
  • Now there is more auxin in the upper side of the root so that side grows slower
  • Root curves upwards
  • Cycle repeats
111
Q

Uses of Auxin

A
  • Growing plant clones in tissue cultures
  • Used in rooting powder to grow plant cuttings
  • Used to kill weed by disrupting their growth pattern
112
Q

Gibberellin

A

Initiates seed germination

113
Q

Uses of Gibberellin

A
  • Controlling dormancy by inducing germination to produce multiple crops
  • Induced flowering
  • Used to grow larger fruit
114
Q

Ethene

A

Controls cell division and ripening of fruits

115
Q

Use of Ethene

A

Ripens fruit after it has been transported from different countries so it’s fresh

GCSE Biology (6 decks)

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