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Homeostasis Flashcards

1
Q

What is homeostasis?

A

The maintenance of a stable internal
environment in the body despite
fluctuations in internal and external
conditions.

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2
Q

Why is homeostasis important?

A

To ensure optimum conditions for enzymes

and cellular processes in the body

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3
Q

State three conditions within the body that must be

controlled by homeostasis

A

● Temperature
● Blood glucose concentration
● Water levels

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4
Q

What is thermoregulation?

A

The maintenance of core body

temperature

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5
Q

Why must body temperature be controlled?

A

Enzymes work best at their optimum
temperature. Deviations from this optimum
temperature decrease the rate of
enzyme-controlled reactions.

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6
Q

What is the optimum temperature for enzymes in the

human body?

A

37°C

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7
Q

What does the maintenance of an ideal body

temperature depend on?

A

A negative feedback system involving:

● Receptors

● Hypothalamus

● Effectors e.g. sweat glands, hair erector muscles

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8
Q

Where are temperature-sensitive receptors located?

A

● Skin - epidermis (outer layer) and dermis
(below epidermis)

● Hypothalamus

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9
Q

What is the function of receptors in the skin and in

the hypothalamus?

A

They detect changes in blood
temperature and send information to the
hypothalamus.

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10
Q

What is the function of the hypothalamus?

A

It coordinates information from the
receptors and sends instructions to the
effectors.

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11
Q

What is the function of the effectors in thermoregulation?

A

They produce a response to counteract
the change in blood temperature and
return it to the set point.

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12
Q

Outline the responses of the body to an increase in

temperature above 37°C (3)

A

● Vasodilation

● Sweating

● Erector muscles relax, hairs lie flat

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13
Q

What structure produces sweat?

A

Sweat glands found in the dermis

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14
Q

How is sweat released from the skin?

A

Pores in the epidermis release sweat onto

the skin’s surface which then evaporates.

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15
Q

How does sweating help to reduce body

temperature?

A

Heat energy is used to evaporate sweat.
Increased heat transfer from the skin to the
environment decreases body temperature.

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16
Q

What is vasodilation?

A

● Dilation of blood vessels near the skin surface

● Blood flows closer to the skin surface

● Greater heat loss to the surroundings

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17
Q

Outline the responses of the body to a decrease in

temperature below 37°C

A

● Vasoconstriction

● Shivering

● Hair erector muscles contract

● Little sweat is produced

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18
Q

How does shivering help to increase body

temperature?

A

Involuntary contraction of muscles

generates heat energy from respiration

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19
Q

How does the contraction of hair erector muscles

help to increase body temperature?

A

Hairs stand on end creating pockets of
air between hairs and a layer of
insulation, which traps the warm air.

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20
Q

What is vasoconstriction?

A

● Constriction of blood vessels near skin surface

● Less blood flows close to the skin surface

● Less heat loss to the surroundings

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21
Q

Which organ is responsible for the maintenance of

blood glucose concentrations?

A

Pancreas

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22
Q

How are blood glucose concentrations controlled?

A

Controlled by the hormones insulin and
glucagon which are secreted by the
pancreas

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23
Q

Insulin and glucagon are antagonistic hormones.

What does this mean?

A

They have opposite effects which

counteract one another

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24
Q

Describe the role of insulin in the regulation of blood

sugar levels

A

● Causes liver and muscle cells to increase their
uptake of glucose from the blood

● Glucose is converted into glycogen, a storage
molecule

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25
Describe the role of glucagon in the regulation of | blood sugar levels
● Causes the breakdown of glycogen to glucose in the liver ● Glucose is released into the blood
26
What is the control of blood glucose concentration | an example of?
Negative Feedback
27
Describe what happens when blood glucose | concentrations become too high
● Blood glucose concentration increases above a set point ● Pancreas secretes insulin and stops producing glucagon ● Liver and muscle cells increase uptake of glucose ● Glucose is converted to glycogen and stored ● Some glucose may be stored as lipid in tissues ● Blood glucose concentration decreases, returning to normal levels
28
Describe what happens when blood glucose | concentrations become too low
● Blood glucose concentration decreases below a set point ● Pancreas secretes glucagon and stops producing insulin ● Liver cells convert glycogen into glucose which is released into blood ● Blood glucose concentration increases, returning to normal level
29
What is diabetes?
A condition where the homeostatic control of blood glucose levels stops working.
30
What is the cause of type 1 diabetes?
Pancreas does not produce any | insulin
31
How is type 1 diabetes treated? (3)
● Daily insulin injections at meal times ● Limiting intake of refined sugars ● Regular exercise
32
What is the cause of type 2 diabetes?
Person develops insulin resistance or doesn’t produce enough insulin (often due to obesity)
33
How is type 2 diabetes treated?
● Balanced diet (eating fewer simple sugars and replacing them with more complex carbohydrates) ● Exercise ● Medication or insulin injections (however, these are less effective)
34
How does exercise help to control diabetes?
Exercise increases respiration in muscle cells. Excess glucose is removed from the blood to produce energy in the form of ATP.
35
Why are type 2 diabetics advised to replace simple | carbohydrates with more complex carbohydrates?
● Simple carbohydrates are broken down quickly so can raise blood glucose levels rapidly. ● Complex carbohydrates take longer to break down so have a reduced effect on blood glucose levels.
36
What is the Body Mass Index (BMI)?
A value based on height and mass used to categorise an individual as underweight, normal weight, overweight or obese.
37
How is BMI calculated?
BMI = kg/m^2
38
What BMI values indicate obesity and an increased | risk of type 2 diabetes?
BMI value larger than 30
39
How is an individual’s waist-to-hip ratio calculated?
waist-to-hip ratio = waist circumeference (cm)/ hip circumference (cm)
40
What does a waist-to-hip ratio higher than 1.0 in | males or 0.85 in females indicate?
● Abdominal obesity | ● Increased risk of developing type 2 diabetes
41
What is osmoregulation?
The maintenance of constant water | levels in the body fluids of an organism
42
Why is osmoregulation important?
Prevents cells bursting or shrinking when | water enters or leaves by osmosis
43
Describe what happens to an animal cell if it is placed into a solution with a higher water concentration
● Higher concentration of water in surrounding solution ● Water molecules move down their water concentration gradient into the cell by osmosis ● Pressure inside the cell increases, cell bursts (lysis)
44
Describe what happens to an animal cell if it is placed into a solution with a lower water concentration
● Lower concentration of water in surrounding solution ● Water molecules move down their water concentration gradient out of the cell by osmosis ● Pressure inside the cell decreases, cell shrinks (crenation)
45
Describe what happens to an animal cell if it is placed into a solution with an equal water concentration
No net movement of water molecules | into or out of the cell
46
Describe the function of the kidneys
● Removes toxic waste substances from the body ● Alters blood water levels ● Alters blood ion levels
47
What is urine?
Waste product of the kidney that contains urea, excess water and excess ions
48
How is urea produced?
In the liver, urea is produced from the | breakdown of excess amino acids.
49
Identify the structures of the urinary system labelled in the diagram
``` A= kidney B = renal vein C = renal artery D = ureter E = urethra F = bladder ``` https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FBiology%2FGCSE%2FNotes%2FEdexcel%2F7-Animal-Coordination-Control-and-Homeostasis%2FFlashcards%2FFlashcards%2520-%2520Topic%25207%2520Homeostasis%2520-%2520Edexcel%2520Biology%2520GCSE.pdf Page 98
50
What is the function of the renal artery?
Supplies blood to the kidneys
51
What is the function of the renal vein?
Drains blood from the kidneys
52
What is the function of the ureter?
Takes urine to the bladder from the | kidneys
53
What is the function of the urethra?
Releases urine from the bladder, out of | the body
54
What is a nephron?
Functional unit of the kidney where filtration and selective reabsorption takes place
55
Describe filtration in the kidneys
● Blood flows through the glomerulus under high pressure ● Small molecules (e.g. urea, glucose), water and ions are filtered out of the blood and into the Bowman’s capsule of the nephron
56
Why do large molecules (e.g. red blood cells, | proteins) remain in the blood?
They are too large to fit through the | pores in the capillary walls
57
Which substances are selectively reabsorbed from | the nephron tubule?
● All sugars ● Some water ● Some ions
58
What happens to the molecules not selectively | reabsorbed?
They travel down the kidney tubule as urine and are transported to the bladder via the ureter. Here they are stored and eventually excreted.
59
How is the concentration and volume of urine | controlled?
Controlled by the secretion of | anti-diuretic hormone (ADH)
60
What producesADH?
Pituitary gland
61
Describe how ADH affects the reabsorption of water | from the kidney tubules
ADH increases the permeability of the collecting ducts, enabling more water to be reabsorbed into the blood.
62
What is required to maintain the ideal water content | of blood?
A negative feedback system involving: ● Receptors in the hypothalamus ● Hypothalamus ● Effector i.e. pituitary gland
63
Describe the negative feedback loop which occurs | when low blood water concentration is detected
● Pituitary gland detects low blood water content. ● Pituitary gland increases ADH secretion. ● ADH increases collecting duct permeability so more water is reabsorbed. ● Blood water content increases. More concentrated urine is produced. ●Blood water levels returns to normal
64
Describe the negative feedback loop which occurs | when high blood water concentration is detected
● Pituitary gland detects high blood water levels ● Pituitary gland secretes less ADH. ● Collecting duct becomes less permeable so less water is reabsorbed. ● A large volume of dilute urine is produced. ● Blood water levels return to normal.
65
How can kidney failure be treated?
● Kidney dialysis | ● Kidney transplant
66
What is kidney dialysis?
A machine artificially filters a patient’s | blood
67
How does kidney dialysis work?
● Selectively permeable barrier or membrane separates patient’s blood from dialysis fluid ● Materials are exchanged across the barrier e.g. urea, excess ions and water move out of the blood and into the dialysis fluid through osmosis ● Large cells and proteins remain in the blood
68
Describe the composition of dialysis fluid
● Same concentration of glucose and ions as in normal blood plasma ● No urea
69
What does a kidney transplant involve?
Taking a kidney from a living donor or someone recently deceased and implanting it into the patient.
70
What is the risk associated with kidney transplants?
Risk of the body rejecting the | transplanted kidney
71
What precautions are taken to minimise the risk of | rejection?
● Tissue typing ensures that the transplanted organ is ‘compatible’ with the recipient ● Immunosuppressant drugs help prevent the immune system from rejecting the organ
72
Ultrafiltration?
Water, glucose and Urea move into the Nephron at the Bowman’s capsule, out of the glomerulus under high pressures.
73
Selective Reabsorption
Selective Reabsorption of glucose and some mineral ions by active transport in the first convoluted tubule.
74
Reabsorption of water?
Reabsorption of water by osmosis, depending on how much the body needs. This happens in the loop of Henle and collecting duct.
75
Urine formed
At the end of Nephron, the remaining fluid flows into the ureter. It contains excess water, urea and other substances.

Biology (36 decks)

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