Homeostasis and Response Flashcards
(120 cards)
1
Q
Homeostasis
A
Regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal + external changes
2
Q
What does homeostasis maintain optimal conditions for
A
- enzyme action
- all cell functions
3
Q
What do automatic control systems maintain in body
A
- body temperature
- blood glucose level
- water content
4
Q
Main components of automatic control systems
A
- receptor cells
- coordination centres
- effectors
5
Q
Receptor cells
A
Detect stimuli - changes in environment
6
Q
Coordination centres
A
Receive + process information from receptors - to organise response
7
Q
Examples coordination centres
A
- brain
- spinal cord
- pancreas
8
Q
Effectors
A
Muscles/glands which bring about responses which restore optimum levels when stimulated by coordination centre
9
Q
Function of nervous system
A
Enables humans to react to surroundings and coordinate behaviour
10
Q
Parts of nervous system
A
- central nervous system
- sensory neurons
- motor neurons
- effectors
11
Q
Sensory neurons
A
Carry electrical impulses from receptors to CNS
12
Q
Motor neurons
A
Carry electrical impulses from CNS to effectors
13
Q
Examples of receptors
A
- taste receptors on tongue
- sound receptors in ears
14
Q
What can receptors form part of
A
Larger, complex organs
15
Q
Function of effectors in nervous system
A
Muscles/glands which respond to nervous impulses - muscles may contract, glands may secrete hormones
16
Q
How does CNS coordinate response
A
- receptor stimulated
- sensory neurons carry information from receptors to CNS
- CNS decides what to do - coordinates response
- CNS sends info to effectors along motor neurons and response happens
17
Q
Synapse
A
Connection between 2 neurons
18
Q
How do nerve signals move between neurons
A
- chemical diffusion
- chemicals set off new electrical signal to next neuron
19
Q
Reflexes
A
Rapid, automatic responses to certain stimuli, don’t involve conscious part of brain - can reduce chance of being injured
20
Q
Reflex arc
A
Passage of information in a reflex from receptor to effector
21
Q
Order of reflex arc
A
- stimulus
- receptor
- sensory neuron
- CNS
- relay neuron
- motor neuron
- effector
- response
22
Q
Reflex arc
A
- receptors detect stimulus
- impulse sent along sensory neuron to relay neuron in CNS
- impulse reaches synapse between sensory/relay neuron - they trigger chemical release causing impulse to be sent along relay neuron
- impulses reach synapse between relay/moror neuron - chemicals released to send impulse along motor neuron to effector
23
Q
Reaction time
A
Time it takes to respond to a stimulus - often less than a second
24
Q
Factors affecting reaction time
A
- age
- gender
- drugs
25
Reaction time PRACTICAL
- person sits with arm resting on edge of table
- tester holds ruler vertically with 0 end level between person's thumb/forefinger
- tester lets go of ruler without warning
- person tries to catch ruler as fast as they can
- reaction time - number on ruler above thumb where it was caught
- repeat several times - mean time
- CVs - same person + hand + ruler height
26
More accurate way of measuring reaction time
Computer tests - e.g- click mouse when see stimulus on screen
27
Benefits of using computer reaction time tests
- more precise - no human errors in measurement
- more accurate - time in milliseconds
- remove possibility of person predicting when ruler will drop for example using body language
28
Hormones
Chemical messengers sent in blood
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Where do hormones go
- released directly into blood
- carried in blood to target organs
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Target organs
Particular organs which hormones only affect
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Why are hormones needed
To control things in organs/cells that need constant adjustment
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Endocrine glands
- various glands which produce + secrete hormones
- make up endocrine system
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Endocrine glands in body
- pituitary glands
- pancreas
- thyroid
- adrenal gland
- ovary
- testes
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Pituitary gland
- in brain
- 'master gland’
- secretes several hormones into the blood in response to body conditions
- the hormones act on other glands to stimulate other
hormones to be released to bring about effects
35
Pituitary gland hormone
- FSH
- LH
- TSH
- releases hormones that act on other glands causing them to release hormones
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FSH/LH target organ
Ovaries
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Pancreas hormone
- insulin
- glucagon
38
Insulin/glucagon target organ
Liver
39
Insulin/glucagon effect
Monitors/controls changes of glucose levels in blood
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Thyroid hormones
Thyroxine
41
Thyroxine target organ
Heart
42
Adrenal gland hormone
Adrenaline
43
Adrenaline target organ
- heart
- muscles
44
Oestrogen target organ
Uterus
45
Testes hormone
Testosterone
46
Testosterone target organ
Testes
47
Testosterone effect
- controls male puberty
- stimulates sperm production
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Difference between nerves/hormones
- nerves act fast, hormones act slower
- nerves act for short time, hormones act for long time
- nerves act on precise area, hormones act in more general way
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When are nerves needed
For when you need a quick response - e.g- reflex
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Why are hormones needed
For when you need a long lasting effect - e.g- adrenaline in 'fight/flight'
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How does glucose get into blood
Eating foods containing carbohydrates puts glucose into blood from gut
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How is glucose removed from blood
- normal metabolism removes it
- vigorous exercise removes much more
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What happens to excess glucose
Stored as glycogen in liver/muscles
54
What happens if blood glucose too high
- insulin released into blood
- this makes liver turn glucose into glycogen
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What happens if blood glucose too low
- glucagon released
- glucose moves from blood into cells
- liver turn glycogen into glucose
56
Type 1 diabetes
Pancreas produces too little or no insulin - blood glucose level can rise to death
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Type 1 diabetes treatment
- insulin therapy - several insulin injections throughout day to ensure glucose is removed
- usually at mealtimes
- very effective
- amount of insulin depends on diet + activity
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Type 2 diabetes
- person becomes resistant to own insulin - still produced but body cells don't respond to hormone
- blood sugar can rise to dangerous level
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Type 2 diabetes control
- obesity risk factor
- carbohydrate controlled diet
- regular exercise
60
What do hormones do at puberty
Release sex hormones that trigger off secondary sexual characteristics + cause eggs to mature in women
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Male secondary sex characteristic
Facial hair
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Female secondary sex characteristic
Breasts
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Menstrual cycle STAGE 1
- day 1 - menstruation
- uterus lining breaks down for about 4 days
64
Menstrual cycle STAGE 2
- days 4-14 - uterus lining builds up again
- builds up into thick spongy layer full of blood vessels, ready to receive fertilised egg
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Menstrual cycle STAGE 3
- day 14 - ovulation
- egg develops + released
66
Menstrual cycle STAGE 4
- days 14-28 - wall maintained
- if no fertilised egg has landed on uterus wall by day 28, spongy lining breaks down in NEXT CYCLE
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Hormones controlling menstrual cycle
- FSH
- oestrogen
- LH
- progesterone
68
FSH
- produced in pituitary gland
- causes egg to mature in one of the ovaries in a follicle
- stimulates ovaries to produce oestrogen
69
What does FSH stand for
Follicle Stimulating Hormone
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Oestrogen
- produced in ovaries
- causing lining of uterus to grow
- stimulates release of LH + inhibits release of FSH
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LH
- produced by pituitary gland
- stimulates release of egg at ovulation (day 14)
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What does LH stand for
Luteinising hormone
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Progesterone
- produced in ovaries by remains of follicle after ovulation
- maintains uterus lining in 2nd half of cycle
- progesterone levels fall - lining breaks down
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Hormonal contraceptions
- oestrogen
- progesterone
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How is oestrogen a contraception
- prevents release of egg
- taken everyday - keeps level permanently high, inhibits production of FSH, egg development/production eventually stop
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How is progesterone a contraception
Stimulates production of thick mucus, preventing sperm getting through and reaching egg
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The pill
- combined oral contraceptive pill
- contains oestrogen + progesterone
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Effectiveness of the pill
Over 99%
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Downsides of the pill
- side effects - headaches + nausea
- doesn't protect against STDs
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Benefits of progesterone-only pill
- fewer side effects than the pill
- just as effective
81
Contraceptive patch
- contains oestrogen + progesterone
- small 5cmx5cm patch stuck to skin
- lasts 1 week
82
Contraceptive implant
- inserted under skin of arm
- continuously releases progesterone - makes it hard for sperm to swim to egg
- lasts up to 3 years
83
Intrauterine device (IUD)
- T-shaped device inserted into uterus to kill sperm + prevent implantation of fertilised egg
84
Types of IUD
- plastic
- copper
85
Plastic IUD
Releases progesterone which releases mucus that stops sperm getting to egg
86
Copper IUD
Prevent sperm surviving in uterus
87
How do barrier methods work as contraception
Stop sperm getting to egg
88
Barrier contraceptive methods
- condoms
- diaphragm
- spermicide
89
Condoms
- worn over penis during vaginal intercourse to stop prevent sperm entering vagina
- only form of contraception to protect against STIs
90
Diaphragm
- shallow plastic cup fit over cervix
- must be used with spermicide
91
Spermicide
- substance that disables/kills sperm
- 70-80% effective
92
Sterilisation
- cutting/tying fallopian tubes in female OR sperm duct in male
- permanent procedure
93
Natural contraceptive method
- finding when in menstrual cycle woman is most fertile, avoiding having sexual intercourse those days
- not very effective
94
Abstinence
- not having sexual intercourse
- only way to be completely sure sperm and egg don't meet
95
Cause of female not being able to get pregnant
- levels of FSH too low to cause eggs to mature
- no eggs are released and woman can't get pregnant
96
Methods of helping fertile women have babies
- fertility drug
- IVF
97
What does a fertility drug contain
- FSH
- LH
98
How do fertility drugs work
They stimulate ovulation
99
Pros of fertility drugs
Help many women get pregnant when they previously couldn't
100
Cons of fertility drugs
- doesn't always work - some women have to do it many times, can be expensive
- too many eggs could be stimulated - unexpected multiple multiple pregnancies
101
What does IVF stand for
In Vitro Fertilisation
102
How does IVF work
- FHS + LH given to stimulate eggs to mature
- collect eggs from woman's ovaries
- fertilise them in lab with man's sperm
- fertilised eggs grow into embryos in laboratory incubator
- 1/2 embryos transferred into woman's uterus
103
What does ICSI stand for
Intra-Cytoplasmic Sperm Injection
104
How is ICSI used with IVF
Sperm injected directly into egg
105
When is ICSI often used
When man has low sperm count
106
Pros of IVF
Can give infertile couple a child
107
Cons of IVF
- may be multiple births - more than 1 embryo may grow into baby, risky for mother/babies (higher risk of miscarriage)
- low success rate - about 26% in UK, can be stressful/upsetting
- physically stressful for woman - may be reactions to hormones - vomiting, dehydration
108
Developments in IVF
- advances in microscopes
- specialised micro-tools
- time-lapse imaging
109
How can specialised micro-tools help IVF
- can be used on eggs/sperm under microscope
- can remove single cells from embryo for genetic testing to check it's health
110
Equipment of time-lapse imaging need
Using microscope + camera built into incubaor
111
How can time-lapse imaging help IVF
Growth of embryos can be continuously monitored to help identify those more likely to result in pregnancy
112
Ethical issues with IVF
- unused embryos usually destroyed, this is potential human life
- people think genetic testing before implantation can lead to selection of preferred characteristic (gender, age, ect.)
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When is adrenaline released
When brain detects fear/stress and sends nervous impulses to adrenal glands, secreting adrenaline
114
Effect adrenaline on body
- prepares body for 'fight/flight'
- triggers mechanisms that increase supply of oxygen/glucose to cells in brain/muscles - e.g- increases heart rate
115
Negative feedback systems
- body detects level of substance has gone above/below normal level
- it triggers response to bring level back to normal again
116
What is thyroxine made of
- iodine
- amino acids
117
Thyroxine function
- plays in regulating basal metabolic rate - speed at which chemical reactions occur in body while at rest
- also stimulates protein synthesis for growth + development
118
When is thyroxine released
In response to thyroid stimulating hormone (TSH) being released from pituitary gland
119
How is thyroxine in blood kept at right level
negative feedback system
120
How does thyroxine use negative feedback system
When level of thyroxine in blood higher than nomal, secretion of TSH from pituitary gland inhibited - reduces amount of thyroxine released
