Topic 5: Homeostasis and Response Flashcards
1
Q
Define ‘homeostasis’
A
The regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
2
Q
What 3 things have to be maintained in the human body?
A
Blood glucose concentration, body temperature and water levels
3
Q
What are the 3 components of your automatic control system?
A
Receptors, coordination centres and effectors
4
Q
What do receptors do?
A
Detect stimuli
5
Q
What do coordination centres do?
A
Receive and process information from receptors
6
Q
What do effectors do?
A
Bring about responses to restore optimum levels
7
Q
How are nerve cells adapted to carry electrical impulses?
A
Long, thin and have branched connections
8
Q
Explain how electrical impulses move between neurons [3]
A
- Connection between 2 neurons is called a synapse
- Nerve signal is transferred by chemicals which diffuse across the gap
- Chemicals then set off a new electrical signal to the next neuron
9
Q
Describe the reflex arc [8 steps]
A
Stimuli, receptor, sensory neurone, CNS, relay neurone, motor neurone, effector, response
10
Q
Why are reflexes important?
A
They protect us from harm
11
Q
Where is the Cerebral cortex located?
A
Top of the brain
12
Q
MILC
What is the Cerebral cortex responsible for?
A
Memory, intelligence, language and consciousness
13
Q
Where is the Cerebellum located?
A
Back of the brain
14
Q
What is the Cerebellum responsible for?
A
Muscles coordination
15
Q
Where is the Medulla located?
A
Bottom of brain/by spinal cord
16
Q
What is the Medulla responsible for?
A
Unconscious activities (breathing and heartbeat)
17
Q
What 3 methods are used to study the brain?
A
- Studying patients with brain damage
- Electrically stimulating the brain
- MRI scans
18
Q
Why is investigating the brain so difficult?
A
Due to its complexity and delicacy
19
Q
What is the job of the sclera?
A
Supports the eye
20
Q
What is the job of the cornea?
A
Refracts light into the eye
21
Q
What is the job of the iris?
A
Controls how much light can enter the pupil
22
Q
What is the job of the lens?
A
Refracts and focuses light onto the retina
23
Q
What is the job of the retina?
A
To capture the light and colour which enters the eye
24
Q
What do the ciliary muscles and suspensory ligaments do?
A
Control the shape of the lens
25
What does the optic nerve do?
Carries impulses from the receptors of the retina to the brain
26
What happens to your pupil in bright light and how?
1. Your pupil gets smaller
2. The circular muscles contract
3. The radial muscles relax
27
Why does you pupil constrict in bright light?
To reduce the amount of light that can enter the eye - protects retina
28
What happens to your pupil in dim light and how?
1. Your pupil gets bigger
2. The radial muscles contract
3. The circular muscles relax
29
Why does your pupil dilate in dim light?
To allow more light to enter the eye
30
What happens to focus on near objects?
1. The ciliary muscles contract
2. The suspensory ligaments slacken
3. The lens is thicker and refracts light rays strongly
31
What happes to focus on distant objects?
1. The ciliary muscles relax
2. The suspensory ligaments become taught
3. The lens is thinner and only slightly refracts light
32
What causes long-sightedness?
The lens doesn't refract the light enough - image appears behind the retina
33
How can long-sightedness be fixed?
Use glasses with convex lenses - increases the refraction
34
What is the medical term for long-sightedness?
Hyperopia
35
What causes short-sightedness?
The lens refracts light too much - image appears before the retina
36
How can short-sightedness be fixed?
Use glasses with concave lenses - counteracts the over-refraction
37
What is the medical term for short-sightedness?
Myopia
38
Pros of contact lenses
More convenient than glasses for sports etc
39
Cons of contact lenses
Risk of eye infections
40
Pros of laser eye surgery
Can fix hyperopia and myopia
41
Cons of laser eye surgy [2]
1. Risk of infection
2. Making vision worse than before
42
Pros of replacement lens surgery
Can fix hyperopia
43
Cons of replacement eye surgery
Can cause damage to retina
44
What does the body do when it's too hot? [3]
1. Hairs lie flat
2. Blood vessels expand (vasodilate)
3. Sweat
45
How does vasodilation cool you down?
More blood flows close to the skin's surface, so heat energy is transferred to the surroundings
46
How does sweating cool you down?
As sweat evaporates, it transfers heat energy to the surroundings
47
What does the body do when it's too cold? [3]
1. Blood vessels constrict (vasoconstrict)
2. Hairs stand on end
3. Shiver
48
How does vasoconstriction warm you up?
Less blood flows close to the skin's surface, so less heat energy is lost
49
How do hairs standing on end warm you up?
Traps a layer of insulating air, so harder to lose heat from skin
50
How does shivering warm you up?
Requires respiration which creates heat energy as waste
51
Which part of the brain controls body temperature?
Hypothalamus
52
Describe the pathway of the endocrine system [3]
1. Glands secrete hormones into bloodstream
2. Blood carries hormone to target organs
3. An effect is produced
53
What is the brain's 'master gland'?
Pituitary gland
54
What does the pituitary gland do?
Produces hormones which act on other glands to secrete their hormones
55
What does the thyroid produce?
Thyroxine
56
What does thyroxine do?
Regulates metabolism
57
What does the adrenal gland produce?
Adrenaline
58
What does adrenaline do?
Prepares your body for a 'fight or flight' response
59
What does the pancreas produce?
Insulin
60
What does insulin do?
Regulates blood glucose levels
61
What do the testes produce?
Testosterone
62
What does testosterone do? [2]
Controls puberty and sperm production
63
What do the ovaries produce?
Oestrogen
64
What does oestrogen do? [2]
Controls puberty and menstrual cycle
65
3 characterists of the nervous system
1. Fast action
2. Short-lasting
3. Precise
66
3 characteristics of endocrine system
1. Slower action
2. Long-lasting
3. General
67
Describe what happens when blood glucose levels are too high [5]
1. Blood has too much glucose
2. Pancreas secretes the hormone insulin
3. Causes glucose to move from the blood into liver and muscle cells
4. This glucose is then converted into glycogen for storage
5. Blood glucose levels reduced
68
Describe what happens when blood glucose levels are too low [5]
1. Blood has too little glucose
2. Pancreas secretes the hormone glucagon
3. Causes glycogen in cells to be converted into glucose
4. Glucose released into blood
5. Blood glucose levels increased
69
Effect of too little blood glucose
Won't be enough glucose for tissue cells to respire
70
Effect of too much blood glucose
Damages tissues
71
What is type 1 diabetes?
The pancreas produces little or no insulin
72
How is type 1 diabetes treated?
Insulin injections
73
What precautions should people with type 1 diabetes take and why? [2]
1. Limiting sugar-rich foods (which causes blood glucose levels to rise)
2. Regular exercise (helps to remove excess glucose from the body)
74
What is type 2 diabetes?
Body cells no longer respond to insulin produed by the pancreas
75
How is type 2 diabetes regulated? [2]
1. Healthy diet
2. Regular exercise
76
What are the 2 jobs of the kidneys?
1. Remove waste products
2. Regulate levels of useful things
77
# Filtration, selective reabsorption
Explain how the kidneys remove waste and regulate useful substances [5]
1. Kidneys how around 1 million structures called nephrons
2. As blood passes through, the tubules absorb anything small
3. This is known as filtration
4. The blood then reabsorbs the useful things from the tubules
5. This is known as selective reabsorption
78
# Proteins, amino acids, ammonia
What is urea? [3]
1. The digestion of proteins from our diet results in excess amino acids
2. In the liver, these amino acids are deaminated to form ammonia
3. Ammonia is toxic so is converted into urea for safe excretion
79
How are ions and water lost in the body? [2]
Sweat and during exhalation
80
Why must water levels be regulated?
Our cells can be damaged (swell and pop or shrink)
81
# ADH
What hormone controls the concentration of urine?
ADH
82
Where is ADH released from?
Pituitary gland
83
Describe what happens when water levels are too low? [6]
1. Water levels are too low
2. A signal is sent to the pituitary gland
3. Pituitary gland releases ADH into the bloodstream
4. ADH reaches kidneys and tells the tubules to reabsorb more water back into the blood
5. Amount of water in bloodstream increases
6. We produce less urine
84
Describe what happens when water levels are too high? [6]
1. Water levels are too high
2. Signals stop sending to the pituitary gland
3. Less ADH released
4. Less ADH reaches kidneys
5. Tubules reabsorb less water into bloodstream
6. We produce more urine
85
What are the consequences of kidney failure? [2]
1. Waste substances build-up in blood stream
2. Unable to regulate water and ion levels
86
# Write on paper and check!!!
Describe how dialysis works [7]
1. Person's blood supply connected to dialysis machine
2. The person's blood can pass into the machine, through the circuit and back out again
3. Whilst in the machine, the person's blood comes into contact with dialysis fluid, separated by a partially permebale membrane
4. Only things like ions and water can diffuse across, not cells and proteins
5. Dialysis fluid is a mixture with the same concentration of water and other molecules as healthy blood
6. This means that only waste substances (such as urea) and excess ions and water diffuse across. This is because there is a concentration gradient
7. The patient's blood levels are back to normal
87
Problems with dialysis [5]
1. Time-consuming - 3-4 times a week for 3-4 hours each time
2. Can cause blood clots and infections
3. Unpleasant experience
4. Expensive
5. People will have to have it for the rest of their life
88
Problems with kidney transplant [2]
1. Rejection
2. Not enough organs available
89
Describe the 4 stages of the menstrual cycle
1. Menstruation starts - uterus lining breaks down for about 4 days
2. Uterus lining builds up again, from day 4 to 14, ready to receive a fertilised egg
3. Ovulation - an egg develops and is released from the ovary on day 14
4. Wall is maintained until day 28 - if no fertilised egg lands on the uterus wall, the lining breaks down and cycle starts again
90
Describe how the 4 hormones control the menstrual cycle [5]
1. FSH stimulates an egg to mature and stimulates the ovaries to produce oestrogen
2. Oestrogen causes the lining of the uterus to grow, inhibits FSH and stimulates LH
3. LH stimulates the release of an egg on day 14
4. Progesterone maintains the lining of the uterus and inhibits LH and FSH
5. Oestrogen also maintains the uterus lining
91
What hormones can be given to women to increase fertility?
FSH and LH
92
Cons of increasing fertility with hormones [2]
1. Doesn't always work
2. Too many eggs can be stimulated - multiple births
93
Describe how IVF works [4]
1. A woman is given FSH and LH to stimulate egg maturation
2. Eggs are collected and fertilised by sperm from a man in a lab
3. The fertilised egg develops into embryos
4. One or two of the embryos are inserted into the woman's womb
94
Cons of IVF [3]
1. Low success rates
2. Emotionally and physically stressful
3. Lead to multiple births - higher chance of complications
95
How have developments in microscopy helped IVF?
Single cells can be removed from the embryo for genetic testing - to see if healthy
96
What are the ethical issues regarding IVF? [2]
1. Unused embryos destroyed - destroying potential life
2. Genetic testing could lead to designer babies
97
What does adrenaline increase? [4]
1. Heart rate
2. Blood pressure
3. Blood supply to muscles
4. Blood sugar levels
98
What happens when thyroxine levels are too high? [3]
1. Thyroxine will inhibit the pituitary gland from producing TSH
2. Less TSH means the thyroid gland won't produce as much thyroxine
3. Thyroxine levels go back to normal
99
What happens when thyroxine levels are too low? [3]
1. Pituitary gland will release TSH
2. This stimulates the thyroid gland to release thyroxine
3. Thyroxine levels increase to normal
100
# Phototropism, geotropism
What is an auxin?
A plant hormone which controls growth in the tips of shoots and roots, in response to phototropism and geotropism
101
What do auxins do in the shoots?
Promote growth
102
What do auxins do in the roots?
Inhibit growth
103
# THINK: auxins
Explain how a shoot grows towards light [3]
1. When a shoot tip is exposed to light, more auxin accumulates on the side in the shade
2. This makes the cells grow faster on the shaded side
3. So the shoot bends towards the light
104
# THINK: auxins
Explain how shoots grow away from gravity [3]
1. When a shoot is growing sideways, gravity causes more auxin to accumulate on the lower side
2. This causes the lower side to grow faster
3. So the shoot bends upwards
105
# THINK: auxins
Explain how roots grow towards gravity [3]
1. When a root grows sideways, it will have more auxin on its lower side
2. However, in the root, it inhibits growth
3. This means that the cells on the top grow faster and the root bends downwards
106
What are auxins used for? [3]
1. Killing weeds
2. Rooting powders
3. Growing cells in tissue culture
107
What is Gibberellin used for? [3]
1. Controlling dormancy
2. Inducing flowering
3. Growing larger fruit
108
What is ethene used for?
Control the ripening of fruit
