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OCR Gateway A GCSE Biology > B3: Organism level systems > Flashcards

B3: Organism level systems Flashcards

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1
Q

what does the nervous system do

A
  • it detects and responds to changes in your external environment
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2
Q

what does the central nervous system consists of (CNS)

A
  • brain
  • spinal cord
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3
Q

what is a stimulus

A
  • a change in the environment
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4
Q

what do receptors do

A
  • they detect the stimulus
    > different receptors detect different stimuli
  • they change the stimulus into electrical impulses that travel along neurons (nerve cells) to your CNS
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5
Q

what are neurons

A
  • specialised nerve cells which transmit electrical impulses around the nervous system
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6
Q

what are effectors

A
  • muscles or glands
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7
Q

what is a response

A
  • a reaction to the stimulus carried out by effectors
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8
Q

what are reflexes

A
  • involuntary responses that occur without conscious thought
  • you don’t have control over these responses
  • reflexes are very fast to protect us from harm
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9
Q

what are nerves

A
  • a bundle of neuron cells
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10
Q

name the different types of neurons

A
  • sensory
  • relay
  • motor
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11
Q

what do sensory neurones do

A
  • they carry electrical impulses from receptor cells to CNS
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12
Q

what do relay neurones do

A
  • they carry electrical impulses within CNS and allow sensory and motor neurones to communicate
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13
Q

what do motor neurones do

A
  • they carry electrical impulses from the CNS to effectors
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14
Q

describe the structure of a sensory neuron

A
  • dendrites so can connect with many other neurones
  • electrical impulse carried along dendron to cell body
  • from cell body carried along axon to CNS
  • axons + dendrons covered with fatty myelin sheath - electrical insulator, speeding up electrical impulse
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15
Q

describe the structure of a relay neuron

A
  • nucleus
  • cell body
  • dendrites
  • axon
  • dendron
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16
Q

describe the structure of a motor neuron

A
  • dendrites, cell body, nucleus
  • electrical impulse along axon (away from cell body) to effector
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17
Q

what is a synapse

A
  • a gap between 2 neurones
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18
Q

electrical impulses can’t travel through the synapse, what is done instead

A
  • chemicals called neurotransmitters diffuse across the gap
  • they then bind with receptor molecules on the next neuron setting off a new electrical impulse
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19
Q

describe the reflex arc with a flow chart

A

Stimulus > receptor cells > sensory neuron > relay neuron > CNS > relay neuron > motor neuron > effector > response

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20
Q

how can the components of the nervous system produce a coordinated response

A
  • it goes to all parts of the body
  • has many links
  • has different sensory receptors and is able to coordinate responses
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21
Q

describe the reflex arc (words)

A
  • a change in environment (stimulus) is detected by a receptor
  • an electrical impulse is travelled along the sensory neurone to the CNS
  • the impulse is carried through the CNS along the relay neuron until it gets to the motor neuron
  • the impulse is then passed along the motor neuron until it gets to an effector
  • the effector then brings about a response - a reflex (involuntary response)
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22
Q

what is the cornea and its function

A
  • transparent layer on the front of the eye
  • protects the eye
  • refracts (bends) light entering the eyes
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23
Q

what is the iris and its function

A
  • coloured ring of muscle
  • alters pupil size by contracting or relaxing
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24
Q

what is the pupil and its function

A
  • central hole in the iris
  • allows different amounts of light into the eye
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25
Q

what is the lens and its function

A
  • transparent flexible biconcave lens
  • focuses light rays clearly onto the retina
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26
Q

what is the retina and its function

A
  • layer of light sensitive cells + nerve endings
  • light focuses onto the retina forming an image
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27
Q

what is the optic nerve and its function

A
  • nervous tissue
  • carries nerve impulses to the brain
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28
Q

what is the ciliary body and its function

A
  • ring of ciliary muscle
  • alters the shape of the lens (accomodation)
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29
Q

what are the suspensory ligaments and its functon

A
  • ligament tissue
  • connects the ciliary muscle to the lens and helps with accomodation
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30
Q

what are the 2 sets of muscles in the iris

A
  • circular
  • radial
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31
Q

what is it called when muscles have opposite effects

A
  • antagonistic
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32
Q

if there is bright light what will happen to the muscles in the iris

A
  • circular muscle contracts
  • radial muscle relaxes
  • pupil constricts
  • lets less light in
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33
Q

if there is dim light what will happen to the muscles in the iris

A
  • circular muscle relaxes
  • radial muscle contracts
  • pupil dilates
  • lets more light in
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34
Q

how are images formed

A
  • light rays from object enters the eye and is refracted by the cornea
  • light then passes through pupil and is further refracted by the lens
  • this produces a sharp image on the retina
  • light receptors in the retina produce a nervous impulse which is carried to the brain and the impulses can be visualised
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35
Q

how do your eyes focus on a nearby object

A
  • ciliary muscle contracts
  • suspensory ligament slackens
  • lens becomes more convex - fatter
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36
Q

how do your eyes focus on a distant object

A
  • ciliary muscle relaxes
  • suspensory ligaments become taut
  • lens becomes more concave - thinner
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37
Q

what causes short sightedness

A
  • lens being too strong
  • eyeball being too long
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38
Q

what causes long sightedness

A
  • lens being too weak
    > ciliary muscles being weak causes lens to be weak as muscle wont contract enough to create a convex lens
  • eyeball being too short
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39
Q

what happens in short sightedness

A
  • the light rays bend too much
  • the light rays meet Infront of the retina so image is blurred
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40
Q

how is short sightedness corrected

A
  • by using glasses or contact lenses with a concave lens
  • this bends the light rays outwards before they enter the eye
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41
Q

what happens in long sightedness

A
  • the light rays don’t bend enough
  • the light rays meet behind the retina so image is blurred
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42
Q

how is long sightedness corrected

A
  • by wearing glasses or contact lenses with a convex lens
  • this bends the light rays inwards before they enter the eye
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43
Q

what is the focal point

A
  • where light rays meet
    > usually on the retina
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44
Q

what is colour blindness

A
  • when people have difficulty making out different colours (or can’t see colour at all)
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45
Q

what are the 2 types of photoreceptor cells in the retina and their functions

A
  • rods : respond to different light intensities
  • cones : respond to different colours
    > diff cone cells respond to red, blue and green light
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46
Q

what is the most common form of colour blindness

A
  • red - green
  • when people can’t distinguish between red + green light
    > genetically inherited condition usually affecting males
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47
Q
A
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48
Q

what is the brain made of

A
  • billions of neurones (approx. 86 billion)
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49
Q

how is the delicate nervous tissue in your brain protected

A
  • your skull
  • protective membranes
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50
Q

what is the function of the brain

A
  • to control and coordinate everything you do using all the information collected by receptor cells and your hormonal system
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51
Q

what are the main areas of the brain

A
  • cerebrum
  • cerebellum
  • medulla
  • hypothalamus
  • pituitary gland
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52
Q

what is the function of the cerebrum

A
  • controls complex behaviours
    > eg. learning, memory, personality, behaviour and conscious thought
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53
Q

what is the function of the cerebellum

A
  • controls posture, balance and involuntary movements
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54
Q

what is the function of the medulla

A
  • controls automatic processes such as heart rate and breathing rate
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55
Q

what is the function of the hypothalamus

A
  • regulates body temperature and water balance (homeostasis)
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56
Q

what is the function of the pituitary gland

A
  • stores and releases important hormones which regulate many body functions
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57
Q

in the past how have scientists worked out the function of different regions of the brain

A
  • using brain damaged patients
  • by looking at the site of damage and its effects they began to map out brain functions
  • they also placed electrodes on animal and human brains
    > the electrical impulses given out, resulted in movements which were recorded and linked back to certain areas of the brain
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58
Q

what do modern day scientists use to work out brain functions

A
  • imaging techniques such as:
    > CT (computed tomography)
    > MRI (magnetic resonance imaging)
  • these scans produce real time images throughout the brain
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59
Q

describe CT scans and how they help investigate brain function

A
  • computed tomography uses X-rays to produce 3D images to identify brain abnormalities
  • cannot be used regularly as x-ray radiation increases risk of cancer
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60
Q

describe MRI scans and how they help investigate brain function

A
  • magnetic resonance imaging scans use powerful magnets to identify brain abnormalities
  • scientists can identify areas of the brain which are active during specific activities
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61
Q

Explain some of the difficulties when investigating brain function

A
  • patients must give consent for medical info to be shared - may be unethical to study severely brain damaged person as they might not be able to give informed consent
  • many case studies need to be analysed to draw reliable conclusions
  • several areas of the brain may be involved in a specific function
  • many believe animal testing is unethical
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62
Q

what are the 2 nervous systems in mammals

A
  • CNS - brain + spinal cord[
  • Peripheral nervous systems (PNS) - consists of neurones which connect CNS to rest of body
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63
Q

what is nervous system damage

A
  • damage to any part of the CNS or PNS
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64
Q

what are the different causes of nervous system damage

A
  • injury
  • disease
  • genetic conditions
  • ingesting a toxic susbtance
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65
Q

PNS consists of motor and sensory neurones, what can damage to these neurones lead to

A
  • inability/reduced ability to detect pain
  • numbness
  • loss of coordination
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66
Q

what can damage to CNS lead to

A

more severe:
- loss of control of body systems
- partial or complete paralysis
- memory loss
- processing difficulties

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67
Q

how can PNS be treated

A
  • PNS neurones have some ability to repair themselves
  • damaged neurones often regenerate from cell body end of neurone forming new axons
  • slow process but symptoms fade overtime
  • severe cases can be treated by nervous tissue skin grafts
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68
Q

why is it difficult to treat damage and disease in the nervous system

A
  • brain and spinal cord are very difficult to access
  • tissues in CNS can’t regenerate
  • drugs can’t penetrate the blood-brain barrier
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69
Q

what are hormones

A
  • hormones are chemical messengers made in endocrine glands and secreted into the bloodstream
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70
Q

what do hormones do

A
  • they cause a response in specific cells that are found in target organs
  • they regulate the functions of many cells and organs
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71
Q

what are endocrine glands

A
  • glands that secrete hormones directly into the bloodstream
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72
Q

what are target cells

A
  • target cells are cells with the specific receptor for a hormone which produces an effect when the hormone binds to the receptor
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73
Q

what is the endocrine system

A
  • its the name given to all the endocrine glands and the hormones that they produce
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74
Q

what does the endocrine system do

A
  • the endocrine system controls and coordinates body processes with the nervous system
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75
Q

describe the similarities between the endocrine and nervous system

A
  • both send messages around the body to provide information about any changes to your internal and external environment
  • also send info as to how body should responds
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76
Q

what is the messaging system in endocrine vs nervous system

A
  • endocrine = hormones
  • nervous = nerves
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77
Q

what is the speed of communication in endocrine vs nervous system

A
  • nerves = very fast
  • hormones = slower
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78
Q

how is the information carried in endocrine vs nervous system

A
  • endocrine = travelled by chemical message through plasma
  • nervous = travelled by electrical impulse along a neurone
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79
Q

what is the duration of respond in endocrine vs nervous system

A
  • endocrine = long lasting
  • nervous = short term
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80
Q

what are the target areas in endocrine vs nervous system

A
  • endocrine = larger targeting area
  • nervous = smaller targeting area
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81
Q

what are the main endocrine glands and what do they produce

A
  • pituitary gland - LH, FSH, ADH, growth hormone
  • thyroid gland - thyroxine
  • adrenal gland - adrenaline
  • pancreas - insulin + glucagon
  • ovaries - oestrogen & progesterone
  • testes - testosterone
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82
Q

what are the functions of the pituitary gland

A
  • controls menstrual cycle (LH, FSH)
  • controls water balance (ADH)
  • stimulates growth (growth hormone)
83
Q

what is function of the thyroid gland

A
  • controls metabolic rate (thyroxine)
84
Q

what is the function of the adrenal gland

A
  • prepares the body for fight or flight (adrenaline)
85
Q

what is the function of the pancreas

A
  • controls blood glucose level (insulin and glucagon)
86
Q

what is the function of the ovaries

A
  • controls development of female sex organs and the menstrual cycle (oestrogen and progesterone)
87
Q

what is the function of the testes

A
  • controls development of male sex organs, can cause aggressive behaviour (testosterone)
88
Q

what is adrenaline

A
  • a hormone released from the adrenal glands (near your kidney)
89
Q

when is adrenaline secreted

A
  • at times of stress, fear, anxiety, excitedness, anger
90
Q

give some effects of adrenaline and reason for it

A
  • inc heart + breathing rate - delivers glucose & oxygen to muscles faster (heart) and increases respiration (breathing)
  • pupils dilate - better vision (more light)
  • glucose released from liver - cope with extra demand for oxygen
  • blood diverted from gut to muscles - more glucose and oxygen delivered to muscles
91
Q

what does thyroxine do

A
  • regulates the body’s metabolic rate - speed at which body transfers energy from chemical stores in order to perform its actions
92
Q

what is the function of thyroid gland

A
  • to take iodine, found in many foods, and convert it into thyroxine by combining it with the amino acid tyrosine
93
Q

what is a goitre and when is it prodced

A
  • a large swelling that’s produced when iodine is lacking from the diet and the thyroid gland enlarges in its attempt to produce thyroxine
94
Q

what is negative feedback

A
  • it’s a type of control that keeps internal conditions constant int body
  • any change away from normal level brings about mechanisms to reverse the change and bring it back to normal
95
Q

what does thyroxine control

A
  • how much energy is available to cells
96
Q

what is thyroxine an example of

A
  • negative feedback system
97
Q

describe thyroxine as a negative feedback system

A
  1. hypothalamus detects if more thyroxine is needed and releases TRH (thyroid releasing hormone)
  2. this causes the pituitary gland to release TSH (thyroid stimulating hormone) which causes thyroid to produce more thyroxine
  3. then hypothalamus detects when cells have enough energy and stops pituitary gland form producing TSH
  4. the thyroid stops producing thyroxine and less energy is released to cells
98
Q

describe thyroxine as a negative feedback system as a flowchart

A

hypothalamus > TRH > pituitary gland > TSH > thyroid > thyroxine > increase energy

99
Q

what is the menstrual cycle

A
  • it’s a monthly cycle during which a woman’s body gets ready for pregnancy
100
Q

how long does a menstrual cycle last

A

28 days

101
Q

what happens in the first 5 days of the menstrual cycle

A
  • period (menstruation)
102
Q

what happens after your period in the menstrual cycel

A
  • the uterus lining starts to thicken ready to receive a fertilised egg
103
Q

what happens on the 14th day of your menstrual cycel

A
  • egg is released from ovary - ovulation
104
Q

what happens in the last 14 days of your menstrual cycle after ovulation

A
  • egg dies if not fertilised
  • if fertilised the egg implants itself in the uterus lining
105
Q

what controls the menstrual cycle

A
  • 4 hormones that are made in the pituitary gland and ovaries
106
Q

what are the 4 hormones that control the menstrual cycle

A
  • FSH - follicle stimulating hormone
  • oestrogen
  • LH - luteinising hormone
  • progesterone
107
Q

what does follicle stimulating hormone do and what is it secreted by

A
  • secreted by pituitary gland
  • causes a follicle (egg) to mature in ovaries
  • stimulates ovaries to produces oestrogen
108
Q

what does oestrogen do and what is it secreted by

A
  • made and secreted by ovaries
  • causes uterus lining (endometrium) to thicken
  • inhibits FSH - to prevent more eggs maturing
  • stimulates LH production
109
Q

what does luteinising hormone do and what is it secreted by

A
  • secreted by pituitary gland
  • causes ovulation (release of an egg from ovary)
110
Q

what does progesterone do and what is it secreted by

A
  • secreted by ovaries
  • keeps uterus lining thick
  • inhibits LH and FSH
111
Q

what is the acronym for the menstrual cycle’s 4 hormones

A
  • FOLP
  • FSH > oestrogen > LH > progesterone
  • egg develops > uterus lining thickens > ovulation > maintains uterus lining
112
Q

what is contraception

A
  • any technique used to prevent pregnancy
113
Q

how does contraception work (3 ways)

A
  • stopping sperm reaching egg
  • preventing eggs from maturing
  • stopping the fertilised egg implant
114
Q

what are the 2 contraception methods

A
  • hormonal
  • non - hormonal
115
Q

how do hormonal contraception’s work

A
  • use hormones to disrupt the normal menstrual cycle
116
Q

how do non-hormonal contraception’s work

A
  • barrier methods preventing the sperm reaching the egg (condoms)
  • chemical releasing devices which kill sperm or prevent egg implanting (coil, the pill)
117
Q

what other methods of contraception’s are there apart from hormonal + non hormonal

A
  • natural methods - abstinence (no sex) + rhythm method (avoid sex around ovulation time)
  • surgical methods - must only be used if couple are sure they don’t want any more children
    > vasectomy - sperm tubes are cut and tied
    > female sterilisation - oviducts are cut and blocked
118
Q

what are the 3 non-hormonal contraceptives

A
  • condom / femidom
  • diaphragm / cervical cap
  • intrauterine device (IUD)
119
Q

what are the 3 hormonal contraceptives

A
  • oestrogen & progesterone pill (combined pill)
  • progesterone pill
  • intrauterine system (IUS, hormonal coil)
120
Q

describe how a condom/femidom works, it’s effectiveness, type, anything extra

A
  • non hormonal
  • 95-98% effective
  • placed over penis / vagina - prevents sperm entering vagina
    > prevents spread of STIs
121
Q

describe how a diaphragm / cervical cap works, it’s effectiveness, type, anything extra

A
  • non hormonal
  • 92-96%
  • inserted into vagina to cover cervix - prevents sperm entering uterus - removed after 6 or more hours after sex
    > not effective unless used in combination with spermicide
122
Q

describe how an intrauterine device (IUD, coil) works, it’s effectiveness, type, anything extra

A
  • non hormonal
  • over 99%
  • inserted into uterus - releases copper which prevents sperm surviving in uterus and fallopian tubes - can also prevent implantation of a fertilised ovum
123
Q

describe how an oestrogen + progesterone pill (combined pill) works, it’s effectiveness, type, anything extra

A
  • hormonal
  • over 99%
  • prevents ovulation - thickens mucus from the cervix, stopping sperm reaching an ovum - prevents implantation of a fertilised egg into the uterus wall
    > taken daily for 21 days of menstrual cycle
124
Q

describe how a progesterone pill works, it’s effectiveness, type, anything extra

A
  • hormonal
  • over 99%
  • thickens mucus from cervix, stopping sperm from reaching an ovum - also thins lining of uterus, preventing implantation and can prevent ovulation
    > must be taken around the same time every day
125
Q

describe how an intrauterine system (IUS, hormonal coil) works, it’s effectiveness, type, anything extra

A
  • hormonal
  • over 99%
  • inserted into uterus - has same effect on body as the progesterone-only pill
    > remains effective for 3-5 years
126
Q

what are some causes of infertility

A
  • blocked oviducts / sperm ducts
  • lack of sperm produced in testes
  • lack of mature eggs in ovaries
  • eggs not released by ovaries
127
Q

what is fertility treatment

A
  • some of the conditions in causing infertility can be treated using hormones
128
Q

describe how artificial fertility drugs can help with infertility

A
  • FSH could be taken as it stimulated eggs to mature and stimulated oestrogen ( which in turn stimulates LH + ovulation)
    > this will increase a woman’s chance of getting pregnant
129
Q

what is IVF

A
  • in vitro fertilisation (in vitro = in glass)
  • involves fertilising eggs from mother with sperm outside of body
    > expensive + unreliable
130
Q

describe how IVF is carried out (steps)

A
  • FSH and LH (fertility drugs) are given to make lots of eggs mature
  • eggs + sperm are collected + placed in a petri dish
  • eggs are checked to make sure they have been fertilised and that the early embryos are developing properly
  • when fertilised eggs form tiny balls of cells, 1/2 embryos are placed in the womb of mother
    > then if it all goes well, at least one baby will grow + develop successfully
131
Q

what are some issues with IVF

A
  • cost (very expensive)
  • multiple births + complications
  • unnatural process
  • often not successful (distressing)
132
Q

what is a tropism

A
  • a tropism is a growth respond to a one sided stimulus
  • tropism is when plants detect stimuli in their environment, and can respond by growth in a particular direction
133
Q

what is a positive tropism

A
  • if a plant grows towards the stimulus
133
Q

what is a negative tropism

A
  • if a plant grows away from the stimulus
133
Q

what is an auxin

A
  • an auxin is a plant hormone which enables a plant to grow towards/away from a stimulus
    > auxins are hormones which control the tropisms
134
Q

how do plants respond to gravity - gravitropism

A
  • gravity causes auxins to accumulate on underside of root
  • auxins at the tip prevent cell elongation so the side with less auxins grow faster causing the root to bend downwards
134
Q

what does an auxin trigger

A
  • cell elongation
  • auxins trigger growth of shoots but inhibits growth of root cells
134
Q

why does a response to the stimulus in plant occur

A
  • because of uneven distribution of auxins
  • this causes an unequal growth rate, which results in the shoot/toot bending
134
Q

where are auxins made

A
  • in cells near the tip of plant shoots or roots
135
Q

how do plants respond to light - phototropism

A
  • when light hits a side of a plant, the auxins move to the other side
    > auxins accumulate on the shaded side
  • the auxins trigger cell elongation which increases length of this side of the shoot causing it to bend towards the light
135
Q

what happens when light falls evenly on a plant

A
  • the auxins are evenly distributed throughout the tip
  • all the cells in the tip grow at the same rate so the shoot grows straight
136
Q

why is geotropism helpful

A
  • helps anchor the plant
  • absorbs minerals from soil + water
136
Q

what is the function of the plant hormone, auxin

A
  • stimulate growth by cell elongation
  • delays ripening of fruit
  • regulate fruit development
136
Q

what are some of the uses of auxins

A
  • encourage growth in plant seedlings
  • used in rooting powders to help cuttings from adult plants develop their own roots
  • selective weed killers - in high conc can disturb metabolism and kill plants
136
Q

how can you use plant hormones to delay ripening

A
  • auxins sprayed on fruit trees to delay ripening
  • this allows harvests to be collected all at the same time and prevents fruit dropping off trees early
136
Q

what are the 3 plant hormones

A
  • auxins
  • gibberellins
  • ethene
136
Q

what is the function of the plant hormone, gibberellin

A
  • promotes stem growth
  • promotes opening of buds and shoots
  • stimulates seed germination
136
Q

how does rooting powder work

A
  • contains auxins
  • promotes root growth
  • plant shoot cut off and dipped in rooting powder and planted
  • few days later roots develop from cut stem and they anchor into the soil and take up water and minerals
136
Q

what is homeostasis

A
  • homeostasis is maintaining a constant internal environment
136
Q

how can plant hormones be used to produce seedless fruit

A
  • use auxins
  • seeds are produced after plants are pollinated by insects or wind
  • if auxins are applied to unpollinated flower, the plant produces seedless fruit
136
Q

how do selective weedkillers work

A
  • contain auxins
  • they kill weeds that are broad-leaved but don’t affect narrow-leaved plants
  • the auxins make the weed grow too fast, and the rapid uncontrolled growth kills the plant
136
Q

what is the function of the plant hormone, ethene

A
  • a gas that stimulates fruit ripening ( converts starch into sugar)
136
Q

name the commercial uses plant hormones

A
  • killing weeds
  • promoting root growth
  • delaying ripening
  • ripening fruit
  • controlling dormancy
  • producing seedless fruit
136
Q

how can plants hormones be used to control dormancy

A
  • seeds remain dormant until conditions are ideal for growth
    > normally prevents germination at end of summer so they survive winter
  • gibberellins + auxins can be sprayed onto seeds to trigger germination in winter (in greenhouses)
137
Q

what’s the core body temperature

A

37 degrees Celsius

137
Q

what 3 conditions need to be controlled within the body

A
  • temperature
  • blood glucose levels
  • water levels
137
Q

how can plant hormones be used to ripen fruit

A
  • ethene sprayed on fruit trees and plants so their fruits ripen quicker
  • this allows fruits to be ready earlier in the growing season
137
Q

why do you need to maintain the body’s core temp

A

to ensure enzymes can always work efficiently

137
Q

what happens if the body’s core temp is reduced when exposed to extreme cold

A
  • enzyme reactions are too slow
  • respiration doesn’t release enough energy, so cells may die
  • risk of hypothermia
138
Q

what happens when you get too hot

A
  • arterioles (tiny blood vessels) widen, inc blood flow close to skin surface - increases heat loss to surroundings by radiation - vasodilation
  • sweat glands in skin produce more sweat - as sweat evaporates from skin’s surface it cools the body down
  • hair erector muscles relax, so hair lie flat - less air trapped, so less insulation
138
Q

what is glucose

A
  • a sugar used in respiration to release energy
138
Q

how is body temperature monitored / controlled

A
  • thermoregulatory centre is found in hypothalamus (brain) + is responsible for regulating body temperatures
  • it receives signals from receptor cells in skin (monitoring external temperature) and internal receptor cells (monitor blood temp)
  • if change in temp is detected, brain causes diff parts of body to respond by sending impulses to effectors
    > these responses return the body back to its normal temp
138
Q

what happens if the body’s core temp is increased when exposed to extreme high temperatures

A
  • enzymes may denature so body reactions can’t occur
  • in extreme circumstances you may die
138
Q

what is insulin

A
  • a hormone made by the pancreas
  • lowers blood sugar
    > stimulates liver to change glucose into glycogen
138
Q

what happens if blood sugar levels are too high

A
  • pancreas detects this and releases hormone insulin
  • insulin stimulates liver to turn glucose into glycogen (a storage carb)
  • insulin also stimulates cells to absorb more glucose from blood, resulting in inc respiration + therefore release of energy
138
Q

what happens when you get too cold

A
  • arterioles become narrower, reducing blood flow to skin’s surface - reduces heat loss to surrounding by radiation - vasoconstriction
  • sweat glands stop producing sweat - less heat loss through evaporation of sweatelax
  • hair erector muscles contract, so hair raises and traps layer of insulating air close to body - insulation
  • muscle contract + relax quickly - shivering - cells respire quicker and release heat which helps to raise blood temp
138
Q

what is glucagon

A
  • hormone made by pancreas that inc blood sugar
  • converts glycogen back into glucose
138
Q

what is diabetes

A
  • condition where blood glucose can’t be controlled
138
Q

what happens if blood sugar levels are too low

A
  • pancreas detect this and releases hormone glucagon
  • glucagon stimulates glycogen (stored in the liver) to be converted back into glucose
  • this increases blood sugar levels back to normal
138
Q

why is it important to control blood sugar levels

A
  • to remain healthy
138
Q

what is the difference between type 1 and type 2 diabetes

A
  • type 1 is when the body can’t produce insulin
  • type 2 is when the body doesn’t respond to insulin
138
Q

when does diabetes occur

A
  • type 1 usually begins in childhood
  • type 2 usually occurs later in life
139
Q

what is glycogen

A
  • a storage substance made of glucose, which is stored in the liver
139
Q

how can type 1 diabetes be treated

A
  • insulin injections
  • balanced regular diet + exercise
139
Q

how can type 2 diabetes be treated

A
  • controlled by regulating diet - reduce carb intake
  • exercise
  • lose weight if overweight
  • some cases drugs are also given to stimulate insulin production, or insulin injections are given
139
Q

what is excretion

A
  • removal of waste products
139
Q

how is water and salt lost from the body

A
  • water + salt lost through sweating + urine
  • water leaves your body as water vapour when you exhale
139
Q

why is it important to remain water balance

A
  • too much water present will move into blood cells causing them to swell and burst - lysis
  • too little water present will remove water from blood cells causing them to shrink - crenation
139
Q

what is urine

A
  • urine is a solution containing water, urea and waste substances
139
Q

why does urea need to be removed

A
  • its toxic so your body must remove it
139
Q

what is the function of the kidneys

A
  • maintaining water balance
  • they filter blood and excrete waste products in urine (toxic urea, excess salts + water)
  • selectively reabsorb useful substances such as glucose, ions, water
139
Q

what is the function of the kidneys in maintaining water balance

A
  • it varies the volume and concentration of urine and hence water excreted
139
Q

describe the general structure of a kidney + surrounding (urine)

A
  • liver : produces urea
  • kidney : makes urine
  • renal vein : carry blood away from kidney
  • renal artery : carry blood to the kidneys
  • ureter : tube that carries urine from kidneys to bladder
  • bladder : stores urine
  • urethra : tube through which urine passes to outside of body
    > kept close by ring of muscle - when muscle relaxes urine leaves body
139
Q

how is urine produced

A
  • filtration - small molecules (water, glucose, urea, salts) squeezed out of blood into kidney tubule
  • selective reabsorption - useful substances absorbed back into blood capillaries
  • urine contains mixture of urine, excess salts and excess water
139
Q

how does kidneys control urine change

A
  • if body is low on water, small concentrated volume of urine produced
  • if body has too much water, large volume of dilute urine is produced
139
Q

what does a cross section of a kidney look like - describe the structure

A
  • capsule: outer membrane of kidney protecting it from damage + maintaining shape
  • cortex: outer part of kidney - where waste substances pass from the blood into kidney tubules
  • medulla: inner part of kidney - where connecting ducts from the kidney tubules meet
  • ureter
  • renal vein
  • renal artery
140
Q

where is urine produced in the kidney

A
  • in the kidney tubules / nephron
141
Q

how does a kidney tubule work

A
  • blood enters kidney via renal artery under high pressure
  • small molecules like water, glucose, salts, and urea pass into Bowman’s capsule from the blood under the high pressure - ultrafiltration
  • selective reabsorption - useful substances (some water, glucose, salt) are reabsorbed into blood
  • substrate passes through loop of Henle where more water + salt pass from the urine into blood (osmosis)
  • blood with waste removes goes into the branch of renal vein
  • the urine then travels along the collecting duct and down the ureter until the bladder where it gets stored
142
Q

how is the volume of urine controlled

A
  • through negative feedback
143
Q

what does negative feedback of urine involve

A
  • hypothalamus and hormone ADH (anti - diuretic hormone)
144
Q

what is ADH

A
  • anti-diuretic hormone
145
Q

what does ADH do

A
  • when ADH is released by pituitary gland into bloodstream, it makes the kidney tubules more permeable to water
  • this increases reabsorption of water into bloodstream so less urine produced
146
Q

describe the negative feedback loop when dehydration is detected

A
  • dehydrated
  • detected by hypothalamus
  • pituitary gland releases ADH
  • kidney tubules more permeable
  • water reabsorbed into blood
  • small volume of concentrated urine
147
Q

describe the negative feedback loop when overhydration is detected

A
  • overhydration
  • detected by hypothalamus
  • NO ADH released
  • kidney tubules less permeable
  • less water reabsorbed
  • large volume of dilute urine
148
Q

how does the body respond to lack of water

A
  • reduction in water / inc sodium - hypothalamus triggers thirst response
  • impulse sent to brain, telling you to have more fluids
  • hypothalamus stimulates ADH to limit urine production
    > more water reabsorbed
149
Q

what is dehydration

A
  • condition when you haven’t taken enough water in your body
150
Q

what are some symptoms of dehydration

A
  • dark concentrated urine
  • headaches + dizziness
  • lack of energy
151
Q

how does the body respond to too much water

A
  • increased water potential / low sodium
  • less ADH released to increase volume of urine
152
Q

how can you become overhydrated

A
  • while exercising or exposure to high temps
    > inc rate of water loss through sweating
    > sweating removes water + salt from body
153
Q

what happens to cells if you consume a large volume of water rapidly

A
  • water will move into cells via osmosis
    > this might cause cells to burst (lysis)
  • conc of sodium decreases - leads to muscle cramping, confusion and seizures
154
Q

what can overhydration do in extreme cases

A
  • water can move into brain cells by osmosis, leading to death
155
Q

what are sports drinks often used for

A
  • rehydration
    > contain essential salts + water
156
Q

what 3 groups can sports drinks be classified into

A
  • hypertonic: high levels of glucose + salts
  • hypotonic: low levels of glucose + salts
  • isotonic - contain ion conc equal to those in blood plasma

OCR Gateway A GCSE Biology (7 decks)

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