Topic 5-Homeostasis and Response Flashcards
1
Q
What is homeostasis?
A
The maintenance of constant internal environments.
Mechanisms are in place to keep optimum conditions despite internal and external changes. Needed for enzyme action and all cell functions
2
Q
What does homeostasis control?
A
- Blood glucose concentration
- Body temperature
- Water levels
3
Q
What do all control systems have?
A
- Receptors
- Coordination centres
- Effectors
4
Q
What do receptors do?
A
Cells that detect stimuli (changes in the environment)
5
Q
What do coordination centres do?
A
They process the information received from the receptors e.g brain, spinal cord and pancreas
6
Q
What do effectors do?
A
They bring about responses to bring the conditions in the body back to optimum levels e.g muscles or glands
7
Q
What are methods used by scientists to determine brain function?
A
- Studying patients with brain damage
- Electrical stimulation of the brain using an electrode
- MRI scans
8
Q
What does the endocrine system do?
A
It sends hormones (chemical messengers) around the body. When they reach a target tissue they produce a response. It is made up of glands which secrete hormones directly into the bloodstream
9
Q
What is the pituitary gland and what does it do?
A
- The master gland
- Secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate to produce different hormones
10
Q
What is the pancreas and what does it do?
A
- Releases insulin
- Controls blood glucose levels
11
Q
What is the thyroid and what does it do?
A
- Releases thyroxine
- Controls metabolic rate, heart rate and temperature
12
Q
What is the adrenal gland and what does it do?
A
- Releases adrenaline
- Is involved in the ‘fight or flight’ response
13
Q
What is the ovary and what does it do?
A
- Releases oestrogen
- Is involved in the menstrual cycle and the development of female secondary sexual characteristics
14
Q
What are the testes and what do they do?
A
- Releases testosterone
- Is involved in the production of sperm and the development of male secondary sexual characteristics
15
Q
What are the effects of adrenaline?
A
- Increase in heart and breathing rate (delivers oxygen and glucose to the body)
- Stored glycogen converted to glucose
- Dilation of pupils
- Increases mental awareness
- Blood diverted away from digestive system to muscles
16
Q
What is the thermoregulatory centre?
A
- Monitors and controls body temperature
- Found in the brain
- Has receptors that monitor the temperature of blood
- Has receptors in the skin that send impulses to the thermoregulatory centre
17
Q
What stimuli are the receptors of the eye sensitive to?
A
Light intensity and colour
18
Q
What is the function of the nervous system?
A
The nervous system allows the body to react to its surroundings and coordinate an appropriate response
19
Q
What is a hormone?
A
A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a responses
20
Q
What type of organ secretes hormones?
A
Glands
21
Q
Which organ monitors and controls blood glucose concentration?
A
The pancreas
22
Q
How does the pancreas respond when blood glucose levels are too high?
A
The pancreas secretes the hormone insulin
Insulin binds to cell in target organs (muscles and liver) causing glucose to move from the blood into muscle cells for respiration
It also causes excess glucose to be converted into glycogen which is stored in the liver
The blood glucose concentration is reduced
23
Q
What happens when the human body temperature becomes too high?
A
Sweat (evaporates from skin surface resulting in increased energy transfer away from body) is produced by sweat glands
Vasodilation means more blood flows closer to the surface of the skin, resulting in increased energy transfer from the body and into the surroundings, resulting in more heat loss
24
Q
What happens if the human body temperature becomes too low?
A
Sweating stops
Skeletal muscles contact rapidly (shivering) to generate heat from respiration
Hairs stand on end to create an insulating layer, trapping warm air
Vasoconstriction means blood does not flow so close to the surface, resulting in less heat lost
25
How does the pancreas respond when blood glucose levels are too low?
The pancreas secretes the hormone glucagon.
Glucagon binds to liver cells causing glycogen to be broken down into glucose
Glucose is released into the blood, increasing the blood glucose concentration
26
How is blood glucose concentration controlled using a negative feedback loop?
When the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas to oppose the change
The action of either hormone (insulin or glucagon) helps bring back the concentration to the correct level
27
What is type 1 diabetes?
Type 1 diabetes is an autoimmune disorder in which the pancreas does not produce sufficient insulin to control the blood glucose concentration
Glucose is excreted with urine and lots of urine is produced leaving the individual very thirsty. It also makes them tiredness and weight loss
28
How can Type 1 diabetes be treated?
It is treated with insulin injections at meal times, which results in glucose being taken up from the bloodstream
It is also advised to limit the intake of simple carbohydrates which contain lots of glucose
Doctors are attempting to cure diabetes with pancreas and pancreatic cell transplants, and genetically engineering pancreatic cells from mice to make insulin
29
What is Type 2 diabetes?
Type 2 diabetes is a disorder in which the body cells no longer respond to insulin, leading to an uncontrolled blood glucose concentration
Blood glucose levels can rise to a fatal amount
Obesity and increasing age is a risk factor for this disease
30
How can Type 2 diabetes be treated?
Following a carefully-controlled diet, reducing the number of simple carbohydrates in diet
Doing regular exercise
Losing weight
There are also drugs to make insulin more effective on body cells, help the pancreas make more insulin or reduce the amount of glucose absorbed from the gut
31
What is osmosis?
It is the process by which water molecule move from place where they are in high concentration to a place where they are in low concentration
32
In what ways is water lost from the body
During exhalation via the lungs
Sweating
Urine (some is reabsorbed in the kidney)
33
In what ways are ions lost from the body?
They are taken into the body via food
If the ion concentration is incorrect, then too little or too much water may enter body cells
This is because the water potential of the blood would be altered
They are lost in sweat
In the kidneys, certain amounts of ions are reabsorbed into the blood after it has been filtered to ensure the concentration in the blood is maintained
34
What happens when the water concentration of the blood increases?
Cells in the body take up water
This is because the concentration of water in the bloodstream is higher than the concentration of water in the cells so water moves into the cells by osmosis
Cells then expand as they take up more water, and may eventually burst
35
What happens when the water concentration of the blood decreases?
Cells in the body lose water
This is because the concentration of water in the bloodstream is lower than the concentration of water in the cells so water moves out of the cells by osmosis
Cells shrink as they lose water
36
How are excess amino acids excreted from the body?
Amino acids are the products of the digestion of proteins
Amino acids are deaminated in the liver to form ammonia. As ammonia is toxic it is converted to urea
It is lost in sweat
In the kidneys it is filtered out of the blood
37
How do the kidneys maintain the balance of water and other substances in the body?
Filtering out the waste products
Selectively reabsorbing useful substances such as glucose, ions and water
38
What is the full name of the hormone ADH?
Anti-diuretic hormone
39
Where is ADH secreted in the body?
It is released into the pancreas by the pituitary gland of the brain
40
How does ADH affect the reabsorption of water in the kidneys?
When the blood is too concentrated, the pituitary gland secretes more ADH
ADH travels in the bloodstream to the kidney and increases the permeability of kidney tubules to water
More water is reabsorbed in the kidneys, resulting in a smaller volume of more concentrated urine
41
Why is kidney failure dangerous?
When the kidneys are damaged, they may be unable to filter the blood properly. This may lead to:
A build-up of toxic molecules like urea in the body
An uncontrolled ion and water balance and cells being damaged as a result of osmosis
42
What are the two ways of treating people with kidney failure?
Dialysis
Kidney transplants
43
How does dialysis work?
Dialysis is when the function of the kidneys is carried out using an artifical membrane
Blood moves between partially permeable membranes surrounded by dialysis fluid.
Dialysis fluid has the same concentrations as ions and glucose as healthy blood
Useful ions and glucose are not lost from the blood but urea, excess ions and water diffuse across the membrane
44
What are some of the advantages and disadvantages of dialysis?
It acts as an artificial kidney and keeps people alive while they wait for a transplant
It has to be done three times a week, with the process itself taking three to four hours
Blood clots could form and you have to follow a strict diet
It is generally unpleasant and the build up of waste products between sessions can leave you feeling ill
45
What are the advantages and disadvantages of kidney transplants?
The person does not need to visit the hospital as regularly as they did when undergoing dialysis and it is cheaper than the overall cost of dialysis
The main problem is that they could be rejected from the body as a result of the immune system recognising the antigens on the donor organ as foreign
The chance of this happening can be reduced by using immunosuppressant drugs
However, this means that the person can be left vulnerable to other diseases. In addition, transplanted kidneys do not last forever
High initial cost
Shortage of donors
Infection during/after surgery
46
What is tropism?
A tropism is the response of a plant to a specific stimulus
47
What is phototropism?
Phototropism is the response of a plant's shoot or root to light
48
What is gravitropism?
Gravitropism is the response os a plant's shoot or root to gravity
49
What is auxin?
Auxin is a hormone which controls the growth of a plant's shoots and roots.
When auxin is unevenly distributed in a growing plant, the rate of growth will also be unequal
50
How do plant shoots show positive phototropism?
One side of the shoot is in the light, causing auxin to move to the shaded side
At the shaded side, the cells are stimulated to grow- the shoot bends towards the light
As a result, photosynthesis can occur at a faster rate
51
How do plant shoots show negative gravitropism?
In a horizontal shoot, auxin accumulated in the lower side due to gravity
Cells on the lower side of shoot grow more, causing the shoot to bend away from the direction of gravity
As a result, more light is usually available for photosynthesis
52
How do plant roots show positive gravitropism?
In a horizontal root, auxin accumulates in the lower side, causing cells to grow less
The root bends in the direction of gravity
As a result, more water and nutrients are available to the plant roots
53
What are gibberllins?
Gibberellins are a type of plant hormone involved in seed germination
54
What is ethene?
Ethene is a type of plant hormone involved in cell division and ripening
55
How does light intensity affect plant growth? (Practical)
DV, IV and CV
IV: Distance between light and petri dish
DV: Height of plant
CV: Same number of seeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature
56
How does direction of light affect plant growth? (Practical)
DV, IV and CV
IV: Direction of light source
DV: Direction of plant growth
CV: Same number of feeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature, distance between lamp and seeds
57
How does the angle of the petri dish affect plant growth? (Practical)
IV, DV and CV
IV: Angle of petri dish
DV: Direction of plant growth
CV: Same number of seeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature, distance between lamp and seeds, direction of light source
58
How does light intensity affect plant growth?
Instructions
First, place cotton wool in three petri dishes and the soak them with equal volumes of water
Then place ten mustard seeds in each dish
Next, leave the dishes in a warm place and allow the seeds to germinate
We need to water the seeds every day with the same volume of water
Once the seeds have germinated, we need to make sure that the three dishes have the same number of seedlings (take out ones that haven't germinated and take more out of the other dishes to match)
Next, use a ruler to measure height of each seedling. Hold stems to keep them straight but be careful to not damage the seedlings
Place the three in different conditions (full sunlight, partial light and total darkness)
Measure height of each seedling every day for at least 5 days then calculate mean for each day
59
What is meant by metabolic rate?
Rate of chemical reactions in the body
60
Give two functions of plant roots
Absorb water from the soil
Absorb minerals and nutrients
Provides anchorage/support
61
"People with the muscles disease are not able to store glycogen in their muscles
Suggest an explanation for the difference in results"
Cannot store sugar as glycogen so they need to receive glucose from somewhere else for respiration
62
Megapode birds:
- Dig a large hole in sand
- Fill the hole with dead plants
- Lay their eggs on top of the dead plants
- Cover the surface with a thick layer of sand
The dead plants in the nest decay. The decaying process helps to keep eggs warm for many weeks
Suggest how
Microorganisms respire and respiration releases thermal energy
63
"Four days after a digester was first set up, the biogas contained a high percentage of carbon dioxide
Suggest an explanation for this"
CO2 is produced by aerobic respiration
Oxygen present
Not much methane
64
The human body is kept at a constant internal temperature of about 37 degrees Celsius
Body temperature is monitored and controlled by the thermoregulatory centre in the brain
Describe what happens in the body to keep the body temp constant
There are temperature receptors in the TC and in the skin. The ones in the skin send impulses to the TC, giving information about skin temperature
If the core body temperature is too high: vasodilation (more blood flows through the skin and more heat is lost)
If core body temperature is too low, blood vessels supplying the skin capillaries constrict to reduce the flow of blood and therefore less heat is lost
65
"Describe and explain the different patterns shown in the core body temperature and skin surface temperature between 9.15 and 10.15"
Increase in core temperature due to increase in respiration which releases energy as a water product
Skin temp decreases because there is sweating which evaporates and cools the skin
66
"During a race, a cyclist's blood glucose concentration began to decrease.
Describe how the body responds when the blood glucose concentration begins to decrease
Pancreas detects low blood glucose
Produces glucagon
Glycogen is converted to glucose
67
Homeostasis keeps conditions in the body relatively constant. The amount of water in the body is controlled by homeostasis
Kidney function is controlled by a gland in the brain
Describe how the water content of the blood is controlled
If water content is too low, ADH is released from the pituitary gland into the blood
Kidney reabsorbs more water and causes more concentrated urine to be produced
If water content is too high, ADH is lowered
Less water is reabsorbed by kidney
More dilute urine produced
68
Describe how a healthy kidney produces urine
The kidney filters the blood
Reabsorbs all of the glucose and some or the ions
Reabsorbs some of the water
Releases urea
69
Marathon runners often drink sports drinks during/after a race
Explain why
To replace water/ions/salts lost in sweat
70
An athlete can run a marathon in 2 hours 15 minutes on a dry day in outside temperatures up to 35 °C.
If the air is dry, his body will not overheat.
In humid conditions the same athlete can run the marathon in the same time.
However, in humid conditions, if the outside temperature goes over 18 °C then his body will overheat.
Suggest an explanation for the athlete overheating in humid conditions.
Sweat released cannot evaporate because of high humidity/all the water vapour
Therefore less heat is lost
