Biology - Topic 5 Homeostasis Flashcards
1
Q
What is homeostasis
A
Maintaining a stable internal environment despite changing conditions
2
Q
Why does the body need to maintain optimal conditions
A
For optimal enzyme action and cell function
3
Q
What internal conditions need to be maintained
A
Body Temperature
Blood glucose levels
Water content
4
Q
Describe the order of the control system
A
receptors ; coordination centre ; effector
5
Q
What is the role of a receptor
A
detects changes in internal or external environment
6
Q
What is the role of coordination centre
A
Interprets changes and organises a responce
7
Q
Where are the coordination centres located in the body
A
Brain, spinal cord, pancreas
8
Q
Name 2 type of effectors and state what they do
A
muscles contract when stimulated and glands release hormones
9
Q
What system does homeostasis rely on and what does it mean
A
Homeostasis relies on a system of negative feedback, meaning whenever levels of something get too high they’re brought back down, and whenever the levels of something get to low, they’re brought back up.
10
Q
what does an electrical impulse do
A
passes along nerve cells
11
Q
what is a synapse
A
the gap between two neurones
12
Q
What is released across a synapse
A
chemicals - the nerve signals are transferred by chemicals which diffuse across the gap
13
Q
What is the CNS
A
Part of nervous system - in vertebrates this consist of the brain and spinal cord only. In mammals the CNS is connected to the body by sensory neurones and motor neurones
14
Q
What is the role of a sensory neurone
A
transfer a signal from a receptor to the CNS
15
Q
What is the role of a motor neurone
A
transfer a signal from the CNS to an effector
16
Q
What is the role of a relay neurone
A
transfer a signal from a sensory neurone to a motor neurone
17
Q
What is a reflex
A
Automatic response to a stimulus that don’t involve the conscious part of your brain
18
Q
What is the pathway of a reflex arc
A
stimulus; receptor; sensory neurone; relay neurone; motor neurone; effector; responce
19
Q
Why are reflexes important
A
they prevent injury
20
Q
What is the brain made up of
A
billions of interconnected neurones
21
Q
What is the role of the cerebral cortex
A
Responsible for things like consciousness intelligence, memory and language
22
Q
What is the role of the cerebellum
A
Responsible for muscle coordination and balance
23
Q
What is the role of the medulla
A
Controls unconscious activities such as breathing and heart rate
24
Q
What is the role of the hypothalamus
A
regulates our body temperature
25
Where is the medulla found
in the brain stem
26
How do scientists study the brain
- Studying patients with brain damage - seeing what part was damaged and relaying this back to the effect it has on the patient
- Electrically stimulating the brain - by pushing a tiny electrode into the tissue and giving it a small zap of electricity scientists can see what specific parts do
- MRI scans - provides a very detailed picture of the brains structure
27
Why is treating the brain so difficult
there is a huge range of things that can go wrong
it is had to access as it is encased within the skull
it is very complicated so hard to target with medication
28
What is the cornea
transparent layer at front of the eye which refracts light
29
What is the optic nerve
carries impulses from the receptors on the retina to the brain
30
What is the pupil
the gap through the eye which light passes to reach the lens
31
what is the lens
focuses the light onto the retina
32
What are the two types of receptors called in the retina
Rod cells and Cone cells
33
what is the point where light focuses on the retina called
the fovea - this region contains the highest concentration of cone cells and gives the sharpest image
34
What is the purpose of the iris reflex
to ensure the optimum amount of light enters the eye
35
Which two muscles make up the iris
Circular and Radial muscles
36
When does the pupil constrict
When it is exposed to bright light the circular muscles in the iris contract and the radial muscles relax
37
What does FSH do
Stimulates ovaries to produce oestrogen and causes the eggs to mature
38
What does LH do
it stimulates the egg to be released
39
outline the process in which the nerve impulses are transmitted across the synapse
- The relay neurone releases a neurotransmitter
- The neurotransmitter diffuses across the synapse
- the neurotransmitter binds to second neurone
- the binding of the neurotransmitter causes an electrical impulse
40
What structures of the eye bend light that enters the eye
the lens and cornea
41
When light enters the eye where should the light be focused
the fovea on the retina
42
When looking at a nearby object what shape should the lens be
When looking at a nearby object the light from the object will hit the eye at a very wide angle so the lens must be short and fat to successfully refract the light
43
For the lens to become short and wide what must happen
the ciliary muscle contracts and the suspensory ligaments slacken
44
What happens to the ciliary muscle, suspensory ligaments, and the lens, when the eye focuses on a distant object?
The suspensory ligaments are pulled taut
Lens is pulled tall and thin
The ciliary muscle relaxes
45
What does long sighted mean
The eye is unable to focus on nearby objects
46
What is a solution to long-sightedness
To wear glasses that contain a convex lens
47
Where do the glands release the hormone
glands release hormones into the bloodstream. The hormones bind to specific cells that have the correct receptors
This will bring about some change within the cells
48
Describe the thyroid gland
Thyroid releases thyroxine. Thyroxine regulates metabolism such as heart rate. If the level of thyroxine in the blood is too low, the pituitary gland will release more thyroid stimulating hormone.
49
Describe the adrenal gland
Adrenal gland releases adrenaline. Adrenaline stimulates fight or flight response
50
Describe the pancreas in terms of insulin
The pancreas releases insulin. Insulin decreases blood sugar levels if they are too high.
51
What organ is testosterone released from
testes
52
What organ is oestrogen released from
ovaries
53
What does oestrogen and testosterone do
stimulates puberty and growth in female and males.
54
What happens if blood glucose concentrations fall too low
There won't be enough glucose for blood tissue cells to respire
55
What does the pancreas detect a change in
the pancreas detects changes in blood glucose concentration
56
Which hormone decreases blood sugar levels
insulin
57
What are the two main organs that insulin stimulates to absorb glucose from the blood?
Muscle and liver
58
When glucose is absorbed by the liver for long term storage, what molecule is it converted to?
Glycogen
59
How does glucagon work
When blood glucose levels fall too low, it's detected by the pancreas. This causes the pancreas to release the hormone glucagon into the bloodstream. The glucagon then travels around the body and binds mainly to cells in the liver. This stimulates those liver cells to break down their stored glycogen into glucose and release it into the bloodstream. This extra glucose increases blood glucose levels back up to normal.
60
what does diabetes mean
the body can't regulate the levels of glucose properly
61
Glucose is a type of
carbohydrate
62
What is the underlying issue in type 1 diabetes
The pancreas doesn't release enough insulin
63
How is type 1 diabetes managed
- Inject insulin
- Monitor diet
- Exercise regularly
64
What is the underlying issue in type 2 diabetes
The body's tissues become resistant to insulin
65
What factors increase the risk of type 2 diabetes
Poor diet
Lack of exercise
66
What are the functions of the kidneys
- Remove urea
- Regulate water levels
- Regulate ion levels
67
Describe the process of deamination
If the body has more amino acids than it needs, it can convert them into lipids or carbohydrates, which can be stored as an energy source for later
68
Where does deamination take place
in the liver
69
What is the downside to the process of deamination
It produces the waste product urea, which has to be excreted by the kidney
70
How are ions removed from the body
By sweating
By the kidneys
71
If we have too much water in the body, what could happen to our cells
They could gain water and burst
72
Each kidney contain millions of tiny units called
nephrons
73
Describe the process of filtration in the kidneys
As blood passes through the kidneys, small substances like glucose, amino acids, and water, are absorbed from the blood into the kidneys.
74
Describe the process of selective reabsorption in the kidneys
As the filtrate passes through the kidneys, useful substances like glucose are reabsorbed from the tubules, into the blood.
75
What substances are not filtered from the blood into the kidney tubules and why
Large proteins and red blood cells because they are too large to pass across
76
Which hormone is responsible for regulating water levels in the body
ADH
77
Which part of the brain detects the level of water in the body
Hypothalamus
78
Describe how the body responds to low water levels
A part of the brain called the hypothalamus detects the low concentration of water in the bloodstream.
This causes it to send a signal to the pituitary gland, which tells it to release more antidiuretic hormone (ADH).
The ADH travels around the body in the blood, and stimulates the kidneys to reabsorb more water from the tubules into the blood.
This means that less urine will be made, and the concentration of water in the blood rises.
79
Does ADH increase or decrease the concentration of water in our bloodstream
increase
80
What are the consequences of kidney failure
Increase in waste products like urea
Poor regulation of ion levels
81
Treatments for kidney failure
dialysis
kidney transplant
82
In a dialysis why is the membrane between the blood and the dialysis fluid partially permeable?
To only allow some substances to diffuse across
83
Why is fresh dialysis fluid continually pumped through the dialysis machine?
To maintain a concentration gradient for diffusion across the membrane
84
What are the disadvantages of dialysis
It is time consuming
There is a risk of infection
It is expensive to run
85
Disadvantages of kidney transplant
- The patient will be required to take immunosuppressants for the rest of their lives
- Risk of kidney being rejected by immune system
86
How long does the average menstrual cycle last?
28 days
87
87
What happens in stage one of the menstrual cycle and what is the name for this stage
Period of bleeding as the uterus lining breaks down - menstruation
88
What happens in stage two of the menstrual cycle
Building up of the uterus lining
89
What happens in stage three of the menstrual cycle - what is this stage called
release of the egg from the ovaries - ovulation
90
What happens in stage 4 of the menstrual cycle
Maintenance of uterus lining
91
Which hormone stimulates the uterus lining to develop
Oestrogen
92
What does LH do
Stimulates the egg to be released around day 14 (ovulation)
93
What does FSH do
Stimulates the egg follicle to mature
94
Which hormone maintains the lining of the uterus?
Progesterone
95
What must occur for somebody to become pregnant naturally?
The fertilised egg must implant into the uterus lining
An egg must be released from the ovaries
Sperm must reach and fertilise the egg
95
96
Which hormones can hormonal contraceptives contain
oestrogen
progesterone
97
How can oestrogen act as a contraceptive
Inhibits FSH production so the egg can't mature
98
How can progesterone act as a contraceptive?
Stimulates the production of mucus in the cervix so sperm can't enter the uterus
99
What is the longest lasting contraceptive method
Intrauterine device
100
How does a spermicide act as a contraceptive
Destroys the sperm cells
101
What is often prescribed to a women that cannot conceive naturally
If a women cannot conceive naturally she can be given FSH and LH which in many cases will restore fertility
102
What are the stages of IVF
A women is given FSH and LH to stimulate their eggs to mature
These eggs can then be collected from the woman's series. Sperm is also collected from the male.
The eggs are then fertilised by the sperm
These fertilised eggs are then left to grow into embryos in a laboratory incubator
Once the embryos are large enough, they are transferred to the women's uterus, so that they can develop into a foetus
103
Why are embryos kept in an incubator whilst in a laboratory
To provide the optimum temperature for the enzymes and thus cell growth
104
What are the cons of IVF
- It is stressful
- emotionally and physically painful (can cause abdominal pains and vomiting)
- only 25% success rate
- there is a high chance of multiple births and associated complications
105
Why do some people think that IVF is unethical
Some embryos (which had the potential for human life) are destroyed
It could lead to 'designer babies' if parents can select embryos with certain traits
106
What does adrenaline do
- increases hart rate
- increases blood pressure
- increases blood flow to muscles
- increases blood sugar levels by stimulating the liver to break glycogen down into glucose
107
Adrenaline causes the conversion of which substance?
Glycogen to glucose
108
What will the pituitary gland do if thyroxine levels are too low?
The pituitary gland will release TSH. This will stimulate the thyroid gland to release more thyroxine.
109
What does the pituitary gland do if thyroxine levels are too high
The thyroxine will inhibit the pituitary gland from producing TSH. Less TSH means that the thyroid gland will release less thyroxine.
110
What is the main role of thyroxine
To increase metabolic rate
111
What stimuli can plants detect
- light
- gravity
- touch
112
What are auxins
Auxins are a family of plant hormones
113
Where are auxins produced
In the tips and shoots of roots.
114
Shoots are considered ...(tropic)
Positively phototropic and negatively geotropic
115
Auxins always accumulate on the ...
Lower side and shaded side of the plant
116
What is phototropism
A response to light
117
Where are auxins made in the plant
In the growing tip of a stem or root
118
What happens to make a root grow in the direction of the force of gravity
The top side grows more than the bottom side
119
What is positive phototropism
Plants grow towards the light
120
What effects do auxin have on plants
Shoot - cell growth
Root - cell inhibition
121
What are the 3 uses of auxin in agriculture and horticulture?
In weedkillers, rooting powders and to promote growth in tissue culture
122
Auxins stimulate cells to grow and divide ,so how can they be used as weedkiller?
If large amount of auxins are added to plants, it can disrupt their growth process by overstimulating them. This can kill the plant.
123
What is the benefit of selective weedkiller
The kill some plants but not all
124
What is dormancy
Seeds are inactive and depo not grow or develop
125
What is germination
Seeds begin to develop and grow
126
Which plant hormone can stimulate a plant to germinate
Gibberellin
127
Which hormone is responsible for inducing fruit to ripen
Ethene
128
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