Homeostatis And Response Flashcards
1
Q
How can the cells in the body survive?
A
Within narrow physical and chemical limits. They require a constant temperature and PH as well as a constant supply of food and water.
2
Q
How does the body maintain a constant temperature and PH?
A
The body requires control systems that constantly monitor and adjust the composition of the blood and tissue.
3
Q
What do the control systems in the body include?
A
Receptors which sense changes and effectors that bring about changes.
4
Q
What is homeostasis?
A
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
5
Q
Why is homeostasis important?
A
It keeps conditions constant for enzyme action and cell functions.
6
Q
What does homeostasis include the control of?
A
Blood glucose concentration
Body temperature
Water and ion levels
7
Q
What does this automatic control system (homeostasis) involve?
A
Nervous or chemical responses.
8
Q
What do all control systems include?
A
- Cells called receptors, which detect stimuli (changes in the environment).
- Coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors.
- effectors, muscles or glands, which bring about responses which restore optimum levels.
9
Q
What temperature should the human body be kept around?
A
37 degrees
10
Q
Why does the body have a temperature that it should be kept at?
A
So there is an optimum temperature for enzymes to work.
11
Q
What does the thermoregulatory centre in the brain do?
A
- Monitors and controls body temperature
- Has receptors that monitor the temperature of the blood flowing through the brain
- Receives information (impulses) from temperature receptors in the skin.
12
Q
What happens if body temperature is too high?
A
- Vasodilation, blood vessels widen, directing more blood to the surface of the skin.
- More sweat is produced from sweat glands and evaporates
- Hair and hair erector muscles are relaxed.
13
Q
What do all the mechanisms that happens to the body when you’re too hot cause?
A
A transfer of energy from the skin to the environment.
14
Q
What happens is body temperature is too low?
A
- Vasoconstriction, blood vessels narrow directing blood away from the surface of the skin.
- Sweating stops
- Skeletal muscles uncontrollably contract and relax quickly (shiver), which transfers more heat to the blood.
- Hair and hair erector muscles stand on end to trap a layer of air.
15
Q
What does the human nervous system enable humans to do?
A
To react to their surroundings and to coordinate their behaviour.
16
Q
How is information passed along the nervous system?
A
Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
17
Q
What is the CNS?
A
The brain and the spinal cord.
18
Q
What are reflex actions and why?
A
Reflex actions are automatic and rapid so that they can protect the brain.
19
Q
How do reflex actions happen?
A
- Pain stimulus is detected by receptors.
- Impulses from the receptor pass along a sensory neurone to the CNS.
- An impulse passes through a relay neurone.
- A motor neurone carries an impulse to the effector.
- The effector (usually a muscles) responds e.g. to withdraw a limb from a source of pain.
20
Q
In a reflex action in which order is the message passes along the nervous system?
A
Stimulus - Receptor - Coordinator - effector - response
21
Q
Why does a reflex arc not include the conscious part of the brain?
A
So we cannot override the response.
22
Q
What is the position of neurones like?
A
They are not directly connected to each other.
23
Q
How do neurones communicate with each other?
A
Via synapses (gaps between neurones).
24
Q
What happens when an electrical impulse reaches a synapse?
A
A chemical is released that diffuses across the gap between the two neurones. This causes an electrical impulse to be generated in the second neurone.
25
What does the brain control and what is it made up of?
The brain controls complex behaviour. It is made up of billions of interconnected neurones and has differ t regions that carry out different functions.
26
What does the cerebral cortex do?
- Makes up 3/4 of the brain’s volume
- Mase up of neurones and nerve fibres that transfer information
- Responsible for learning, reasoning, speech, sight and hearing.
- Concerned with consciousness, intelligence, memory and language
27
What does the cerebellum do?
- Consists of nerve cells and nerve fibres.
- Coordinated muscle movement, controlling muscular activity and balance
- Responsible for carrying signals to other parts of the brain and spinal cord.
28
What does the hypothalamus in the brain do?
Releases hormones, controls temperature.
29
What does the medulla do?
- Creates sensory pathways between spinal cord and brain.
| - Controls unconscious activities e.g. heartbeat and breathing.
30
What does the pituitary gland in the brain do?
- Responsible for producing and regulating neuro chemicals
| - Produces hormones which control the body via homeostasis
31
What are the three main parts of the brain?
The cerebellum, cerebral cortex and the medulla
32
How are neuroscientists able to map the regions of the brain to particular functions?
- Studying patients with brain damage, looking at the areas affected and the change in person.
- Electrically stimulating parts of the brain, surgeons cut out part of skull and use electrical signals to stimulate parts of the brain.
- MRI scans can light up when an area is stimulated due to activity or does not light up due to damage.
33
Why is investigating and treating brain disorders very difficult?
Because of the complexity and delicacy of the brain. Hey
34
What is the eye?
A sense organ containing receptors sensitive to light intensity and colour.
35
What does the retina do?
The retina contains receptor cells that are sensitive to the brightness and colour of light.
36
What does the optic nerve do?
Carries impulses from the retina to the brain.
37
What does the sclera do?
Forms a tough outer layer with a transparent region at the front called the cornea.
38
What does the iris do?
Controls the side of the pupil and the amount of light reaching the retina.
39
What do the ciliary muscles and the suspenseful ligaments do?
They can change the shape of the lens to focus light onto the retina.
40
What are the parts of the eye?
Retina, optic nerves, sclera, cornea, iris, ciliary muscles, suspensory ligaments
41
What is accommodation?
The process of changing the shape of lens to focus on near objects.
42
How does the eye focus on near objects?
- The ciliary muscles contract
- The suspensory ligament loosen
- The lens is then thicker and refracts light rays strongly
43
How does the eye focus on distant objects?
- The ciliary muscles relax
- The suspensory muscles are pulled tight
- The lens is then pulled thin and only slightly refracts light rays much
44
What are the two common defects of the eyes?
Myopia (short sightedness) and hyperopia (long sightedness) in which light rays do not focus on the retina.
45
How are defects of the eye generally treated?
With spectacle lenses which refract the light rays so that they do focus on the retina.
46
What do new technologies to correct eye defects include?
Hard and soft contact lenses, laser surgery go change the shape of the cornea and a replacement lens in the eye.
47
Why are people short sighted?
In short sighted people, light rays meet in front of the retina and so the image is blurred.
48
How is myopia (short sightedness) corrected?
Using a diverging/ concave lens to spread light rays out before they hit the cornea do they can focus on the retina.
49
Why are people long sighted?
Light rays meet behind the retina and so the image is blurred, eye cannot focus on near by images.
50
How is hyperopia (long sightedness) corrected?
Use a converging lens to narrow beams of light rays before they hit they hit the cornea so they can focus on the retina.
51
What are contact lenses?
Lenses placed on the eye
52
What are replacement lenses?
The natural lens is left in place but a contact lens is permanently implanted or natural lens is removed and placed by an artificial lens.
53
What is laser eye surgery?
Shape of cornea is changed to cause light to be focussed closer/ further away, this is only available to adults.
54
How does the endocrine system work?
It is composed of glands which secrete chemicals called hormones directly into the blood stream. The blood carries the hormone to a target organ where it produces an effect.
55
What is the endocrine system like compared to the nervous system?
Compared to the nervous system the effects are slower but act for longer.
56
What are the parts of the endocrine system?
```
Pituitary gland (in the brain)
Pancreas
Thyroid (in the throat)
Adrenal gland (above pancreas)
Ovary
Testes
```
57
What is the pituitary gland?
The pituitary gland in the brain is a ‘master gland’ which secretes several hormones into the blood in response to body conditions. These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects.
58
What does the pancreas do?
Produces the hormone insulin which is responsible for controlling the level of glucose in the body.
59
What does the thyroid gland do?
Releases a hormone called thyroxine that controls the body’s metabolism (the way the body uses energy) it also stimulates and controls growth in young animals. Thyroxine’s controlled by negative feedback.
60
What does the adrenal gland do?
The adrenal gland produces adrenaline in times of fear of stress which increases the heart rate boosting the delivery of oxygen and glucose to the brain and muscles. Adrenaline prepares the body for ‘flight or fight’.
61
How is blood glucose concentration monitored?
It is monitored and controlled by the pancreas.
62
What happens if blood glucose concentration is too high?
- The pancreas releases more of the hormone insulin.
- Insulin causes glucose to move from the blood into the cells.
- In the liver and muscle cells, excess glucose is converted to glycogen for storage.
63
What happens if blood glucose is too low?
- The pancreas releases glucagon
| - Glucagon stimulates glycogen to be converted to glucose and releases into the blood.
64
How is what happens when blood glucose is too low an example of negative feedback?
Glucagon interacts with insulin in a negative feedback cycle to control blood glucose (sugar) levels in the body.
65
What is type 1 diabetes caused by?
The pancreas failing to produce sufficient insulin.
66
What does type 1 diabetes result in?
It results in uncontrolled high blood glucose levels.
67
How is type 1 diabetes usually treated?
It is normally treated with insulin injections.
68
What is type 2 diabetes caused by?
By the body cells no longer responding to insulin.
69
What is a risk factor of type 2 diabetes?
Obesity
70
What is type 2 diabetes treated with?
A carbohydrate controlled diet and regular exercise.
71
When are water, ions and urea lost in the body?
Water leaves the body via the lungs during exhalation. Water, ions and urea are lost from the skin in sweat. Excess water, ions and urea are removed via the kidneys in the urine. There is no control over water, ion or urea loss by the lungs or skin.
72
What happens if body cells loose or gain too much water by osmosis?
They do not function efficiently.
73
What does the digestion of proteins from the diet result in?
In excess amino acids which need to be excreted safely. In the liver these amino acids are deaminated to form ammonia. Ammonia is toxic and so it is immediately converted into urea for safe excretion.
74
How do the kidneys produced urine?
- Filtering the blood
- Selective reabsorption of useful substances, such as glucose, some ions and water
- Large molecules like proteins and red blood cells are too big to fit through the partially permeable membrane.
- This leaves urea and excess water and ions to form urea.
75
Where do the processes of producing urine take place?
In millions of small tubes in the kidneys called tubules.
76
Which hormone controls water level in the body?
ADH (anti diuretic hormone), which acts on the kidney tubules.
77
Which gland releases ADH?
The pituitary gland
78
When does the pituitary gland release ADH?
When the blood is too concentrated.
79
What does ADH cause the body to do?
It causes more water to be reabsorbed back into the blood from the kidney tubules. This is controlled by negative feedback.
80
What are people who suffer from kidney failure treated by?
An organ transplant or by using a dialysis machine.
81
What does a dialysis machine do?
A dialysis machine takes over the role of the kidneys, it is used to remove waste products from the blood 3 times a week.
82
What happens to the blood when it goes through a dialysis machine?
Arterial blood is pumped out of the arm to prevent back flow. It passes through blood thinners to prevent clotting. The blood goes through a dialysis machine and dialysis fluid moves in and carries waste products and urea is removed. Clean blood flows through bubble trap to get rid of any bubbles, clean blood returns to a vein in the arm.
83
What are the advantages of dialysis for older people?
Don’t have to wait for a kidney.
84
What are the disadvantages of dialysis for older people?
If you’re 75+ average life expectancy is 4 years.
85
What are the advantages of a transplant for older people?
Better quality of life.
86
What are the disadvantages of transplants for older people?
Medication may put patient at a greater risk of cancer/ other illnesses.
87
What are the advantages of dialysis for younger people?
Don’t have to wait for a kidney or have operations.
88
What are the disadvantages of dialysis for younger people?
Requires considerable personal discipline.
89
What are the advantages of a transplant for younger people?
Increased life expectancy, better quality of life.
90
What are the disadvantages of a transplant for younger people?
May have to be on medication for the rest of your life to prevent kidney rejection, have to have operations.
91
What do the sex hormones cause during puberty?
Secondary sexual characteristics to develop.
92
What is oestrogen?
The female reproductive hormone produced in the ovary.
93
What is ovulation?
When, at puberty, eggs begin to develop and one is released approximately every 28 days.
94
What is testosterone?
The main male reproductive hormone produced by the testes and it stimulates sperm production.
95
What is the order of the menstrual cycle?
Period (lasts 3-5 days), lining of uterus starts to thicken, egg released (day 14), egg dies if not fertilised, if egg is fertilised it settles into thick lining, back to start.
96
What are the four hormones involved in the control of the menstrual cycle?
- Follicle Stimulating hormone (FSH)
- Oestrogen
- Luteinising hormone (LH)
- Progesterone
97
What is FSH secreted by?
The pituitary gland
98
What is oestrogen secreted by?
The ovaries
99
What is LH secreted by?
Pituitary gland
100
What is progesterone secreted by?
Empty follicle in the ovaries.
101
What is the function of FSH in the menstrual cycle?
- Causes eggs to mature in the first part of the cycle
| - Stimulates the ovaries to produce oestrogen
102
What is oestrogen secreted by?
The ovaries
103
What is the function of oestrogen in the menstrual cycle?
- Inhibits FSH release
- stimulates LH release
- Makes the lining of the uterus grow again after menstruation
104
What is the function of LH in the menstrual cycle?
Stimulates the release of egg from the ovaries (ovulation)
105
What is the function of progesterone in the menstrual cycle?
- Maintains the lining of the uterus during second half of cycle.
- Inhibits both FSH and LH release.
106
How often is an egg released?
Approximately every 28 days but this can vary between different women.
107
What is negative feedback?
A reaction that causes a decrease in feedback.
108
What do the adrenal glands produce?
Adrenaline
109
When is adrenaline produced?
In times of fear or stress.
110
What does adrenaline do to the body?
It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘fight or flight’.
111
Where is thyroxine produced?
In the thyroid gland
112
What does thyroxine stimulate?
The basal metabolic rate, it plays an important role in growth and development.
113
What are thyroxine levels controlled by?
Negative feedback
114
Why do plants produce hormones?
To coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism).
115
What can I equal distributions of auxin cause in a plant?
Unequal growth rate in roots and shoots.
116
What do plant responses to changes in the external environment include?
- Shoots or roots growing towards/ away from a particular stimulus.
- Plants flowering at a particular time.
- Ripening of fruit
117
What is tropism?
When part of a plant responds to external changes in the environment by growing in a particular direction.
118
When shoots grow away from gravity what is it?
Negatively gravitropic
119
When roots grow towards gravity what is it?
Positively gravitropic
120
When shoots grow towards a light what is it?
Positively phototropic
121
When roots grow away from light what is it called?
Negatively phototropic
122
What are Tropicana controlled by?
A group of plant hormones called auxins.
123
What are the steps involved in a plant’s response to light?
1. More light reaches one side of the shoot
2. More auxin is sent down the shaded side of the shoot
3. This results in cells on the shaded side elongating more
4. The shoot, therefore, grows towards the light
124
What does auxin do in roots?
It moved to the bottom of the root and causes less elongation so the root grows downwards.
125
What are gibberellins?
Another group of plant hormones and are important in initiating seed germination.
126
What is ethene?
A had and also a plant hormone which controls cell division and the ripening of fruit.
127
How are auxins used as plant growth hormones by farmers and gardeners?
- As weed killers because they make weeds grow so rapidly that they use up all their food reserves and die.
- As rooting powders, because they make cuttings produce roots when they’re planted.
- For promoting growth in tissue culture.
128
What does the fact that auxin weedkillers are selective mean?
They can be used in lawns to kill weeds but not grass.
129
When is ethene used?
In the food industry to control ripening of fruit during storage and transport. Thank
130
How is fruit often transported?
Fruit can be picked unripe before it is transported long distances l, so that it is not damaged, it can ripen with ethene when it has reached its destination.
131
What can gibberellins be used to do?
To end seed dormancy and make seeds germinate
To promote flowering so that plants flower when there is a demand e.g. Mothers’ day or Easter
Increase fruit size
132
What is contraception?
A variety of hormonal and non-hormonal methods that control fertility.
133
What are the hormonal methods of contraception?
- Oral contraceptives
| - Injection, implant or skin patch
134
What are the non hormonal methods of contraception?
- Barrier methods
- Intrauterine devices
- Spermicidal agents
- Abstaining from intercourse
- Surgical method
135
How do oral contraceptives work?
They contain hormones to inhibit FSH production so that no eggs mature.
136
What are the advantages and disadvantages of oral contraceptives?
Advantages - High success rate
| Disadvantages- Have to remember to take it
137
How does the injection, implant and skin patch work?
They are of slow release progesterone to inhibit the maturation and release of eggs for a number of months/ years.
138
What are he advantages/ disadvantages of the injection, implant and skin patch?
Advantages- high success rate
Disadvantages (implant) - Requires surgical procedure
Disadvantages (patch) - Have to remember to change it
139
How do barrier methods work?
Barrier methods (e.g. condom and diaphragm) prevent the sperm from reaching the egg.
140
What are the advantages and disadvantages of barrier methods?
Advantages- prevent STDs, no side effects, require no medical advice
Disadvantages- not 100% effective
141
How do intrauterine devices work?
They prevent the implantation or an embryo or releases a hormone.
142
What are the advantages and disadvantages of intrauterine devices?
Advantages- lasts for 3-5 years
| Disadvantages- may cause period problems or infections
143
How do spermicidal agents work?
They kill or disable sperm.
144
What are the advantages and disadvantages of spermicidal agents?
Advantages- readily available
| Disadvantages- not very effective
145
How does abstinence work?
Abstaining from intercourse when the egg is in the oviduct.
146
How does the surgical method work?
It is the sterilisation of males and females.
147
What are the advantages and disadvantages of the surgical method?
Advantages- 100% effective
| Disadvantages- requires surgery
148
What is in a fertility drug?
FSH and LH
149
Why do some women need to take fertility drugs if they want to become pregnant?
Her own level of FSH is too low to stimulate eggs to mature.
150
What does IVF stand for?
In vitro fertilisation
151
How does IVF work?
1. A mother is given FSH and LH to stimulate the maturation of several eggs.
2. The eggs are collected from the mother and fertilised by sperm from the father.
3. Fertilised eggs develops into embryos.
4. At the stage when they are tiny balls of cells, one or two of the embryos are inserted into the mother’s uterus.
152
What are the disadvantages of fertility treatment?
- It is emotionally and physically stressful
- The success rate is not high
- It can lead to multiple births which are a risk to both the babies and the mother
