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A2 Biology > Homeostasis > Flashcards

Homeostasis Flashcards

0
Q

Define response

A

A change in behaviour or physiology as a result of a change in the environment.

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1
Q

Define stimulus

A

A change in the environment that causes a response.

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2
Q

Give an example of a gradual response to a change in external environment.

A

Growing a thicker coat in winter

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3
Q

External environment

A

The environment outside of the organism

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4
Q

Internal environment

A

The environment inside the cells of the organism bathed in tissue fluid.

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5
Q

Explain the effect of carbon dioxide production on the cells environment.

A

Carbon dioxide reacts with water resulting in carbonic acid. This dissociates into hydrogen carbonate and H+ ions which lower the ph of the cell.

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6
Q

Define excretion

A

The removal of metabolic wastes or toxins from the body.

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7
Q

Explain the neuronal system

A

Network of neurones. Neurones signal each other at synapses. Signals are conducted very quickly. Rapid response

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8
Q

Explain the hormonal system

A

Uses blood to transport signals. Endocrine gland releases hormone directly into blood. Only recognised by specific target cells. Long term responses.

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9
Q

Name the four parts of a control mechanism

A

Detector, controller, effector, feedback loop

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10
Q

Define detector

A

Detects a deviation from the norm

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11
Q

Define controller

A

Sends out information that will correct deviations detected.

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12
Q

Define effector

A

Brings about the changes to return the system to the norm.

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13
Q

Define feedback loop

A

Informs the detector of changes caused by the effector causing the effector to be switched off.

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14
Q

Define dynamic equilibrium

A

A series of oscillations about the norm.

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15
Q

Homeostasis

A

Maintaining a constant internal environment.

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16
Q

Explain negative feedback loops

A

Negative feedback loops reverse the effect of the original stimulus returning the body to the norm.

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17
Q

Explain positive feedback

A

Positive feedback systems enhance the effect of the original stimulus.

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18
Q

Define ectotherms

A

An organism that relies on external sources of heat to maintain body temperature.

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19
Q

Name a behavioural response of an ectotherm and how it regulates temperature.

A

Snakes expose body to sun allowing absorption of heat.

Snakes seek shade to get out of direct sunlight cooling them down.

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20
Q

Name a physiological response on an ectotherm and how it regulates temperature.

A

Locusts increase breathing movements allowing increased evaporation of water aiding cooling.
Horned lizards alter body shape so there is an increased surface area exposed to the sun.

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21
Q

Advantages of being an ectotherm

A

Less food used in respiration.
Can go long periods of time without food.
More energy can be used for growth.

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22
Q

Disadvantages of being an ectotherm

A

Less active in cold means a greater risk of predation.

May not be capable of activity during winter.

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23
Q

Two ways in which heat can be gained.

A

Metabolism of food.

Absorbing solar energy - directly or indirectly( convected or conducted from the ground).

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24
Q

Four ways heat can be lost.

A

Evaporation of water.
Conduction from the body to the ground.
Convection from the body to the air or water.
Radiation from body to air, water or ground.

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25
Q

Role of the hypothalamus( thermoregulatory centre )

A

Located at base of the brain. Monitors temperature of blood flowing through it continuously.
Monitors core temperature.

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26
Q

Role of peripheral receptors.

A

Found in skin. Give early warning of possible change in core temperature by sending nerve impulses to the hypothalamus.

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27
Q

Explain vasodilation

A

Shunt vessels close of and arterioles dilate.
This increases blood flow to the surface, increasing thermal energy transferred to the skin.blood cools as it radiates heat. The cooled blood returns to the core where thermal energy is transferred from tissues by conduction, cooling the tissues.

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28
Q

Explain sweating

A

When sweat evaporates it cools the surface of the skin as heat from the skin is transferred to the sweat causing it to evaporate.
The efficiency of sweating is dependent on humidity. The more humid the less efficient it is.

29
Q

Explain vasoconstriction

A

Arterioles leading to the surface capillaries constrict reducing blood flow to the surface.
This decreases the amount of heat lost through radiation.

30
Q

Explain hair erection.

A

When a nerve impulse arrives from the heat gain centre of the hypothalamus the erector muscle contracts pulling the hair upright. A layer of air is trapped next to the skin. Air is an insulator reducing heat loss through convection and radiation.

31
Q

Explain shivering

A

Rapid random contraction and relaxation of muscles. High rate of respiration to provide energy for the muscles. The respiration is inefficient 80% is released as heat energy. This is transferred to the blood passing through the muscle to be passed on to organs and tissues.

32
Q

Explain increasing the metabolic rates role.

A

Adrenalin acts on the liver causing hydrolysis of glycogen to glucose. When adrenalin reaches the tissues it creates a short increase in respiration immediately releasing energy. Transferred to the blood passing through the tissues.

33
Q

Define metabolic rate.

A

A measurement of the rate at which energy is released by the body.

34
Q

Define endocrines

A

Endocrines release hormones straight into the blood and are ductless.

35
Q

Define exocrines

A

Exocrine glands don’t release hormones. They release secretions into ducts that transport the secretions to the target tissues.

36
Q

Explain target cells

A

Target cells are cells that possess specific complementary receptors on their cell surface membrane for each particular hormone.

37
Q

Target tissues

A

A group of target cells for a specific hormone.

38
Q

Name the types of hormones

A

Protein hormones

Steroid hormones

39
Q

Properties of protein hormones

And examples

A

Derivatives of amino acids.
Non-lipid soluble and do not enter the cell as they cannot pass through the phospholipid bilayer.
E.g insulin and adrenalin.

40
Q

Properties of steroid hormones

And examples

A

Lipid soluble can enter plasma membrane
Have a direct effect on the DNA in the nucleus.
E.g oestrogen and testosterone.

41
Q

Hormone deffinition.

A

A molecule released directly into the blood that acts as a chemical messenger.

42
Q

First messenger

A

The hormone that transmits the signal throughout the body.

43
Q

Second messenger

A

The cyclic AMP that causes a specific response within the cell.

44
Q

Describe the action of adrenalin

A

The first messenger adrenalin binds to the specific complimentary receptor on the target cells plasma membrane. Adenyl cyclase is inactive. When the adrenalin binds to the receptor it interacts with a G protein which then activates the Adenyl cyclase.Adenyl cyclase causes ATP to turn into cyclic AMP. This is the second messenger which activates enzymes in the cell to cause a response.

45
Q

Location of the adrenal glands.

A

Just above the kidneys on each side of the body.

46
Q

Function of adrenal cortex

A

Uses cholesterol to produce steroid hormones.
Mineralcorticoids- help control sodium and potassium levels in blood.
Glucorticoids- help the metabolism of carbohydrates and proteins in the liver.

47
Q

Function of adrenal medulla

A

Production of adrenalin in response to pain or shock.

48
Q

Effects of adrenalin

A 
Increase heart rate, 
increase stroke volume of the heart,
 relaxes smooth muscle in the bronchioles,
 general vasoconstriction to increase blood pressure,
 stimulates glycogenolysis
dilates the pupils, 
increased mental awareness, 
inhibits action of the gut, 
causes body hair to errect.
49
Q

Pancreas function 1

A

Exocrine cells produce digestive enzymes and are secreted into tubules that form the pancreatic duct

50
Q

Pancreatic juice contents

A

Amylase
Trypinogen (an inactive protease)
Lipase

51
Q

Pancreas function 2

A

Endocrine glands
Islets of langerhans regulate blood glucose levels
Alpha cells secrete glucagon- increases blood glucose
Beta cells secrete insulin- decreases blood glucose levels
They work by negative feedback.

52
Q

Alpha-Beta cell recognition

A

Beta cells appear darker as insulin forms dark crystalline deposits.

53
Q

Problems of high/low blood glucose

A

Too high then water moves out of the cells and into the blood via osmosis
Too low and water moves into cells via osmosis causing them to haemolyse.

54
Q

Decreasing blood glucose levels

A

The beta cells in the islets of langerhans detect an increase in blood glucose concentration and secrete insulin into the blood. Insulin binds to the specific complimentary receptors on the plasma membrane of the liver and muscle tissues. This causes:
More glucose transporter proteins to be inserted into the plasma membrane.
More glucose is used in respiration
Glycogenesis
More glucose is converted to fats.

55
Q

Increasing blood glucose levels

A

Alpha cells in the islets of langerhans detect a decrease in blood glucose levels and secrete glucagon which binds to the specific complimentary receptors on the plasma membrane of liver and muscle tissues causing:
Glycogenolysis
More fatty acids used instead of glucose in respiration
Gluconeogenesis

56
Q

What is diabetes?

A

Diabetes mellitus is a disease where the body can no longer control blood glucose levels.

57
Q

Hyperglycaemia

A

Very high blood glucose levels after a sugar rich meal.

58
Q

Hypoglycaemia

A

Very low blood glucose levels after fasting or exercise

59
Q

Type 1 diabetes causes and effects

A

Usually starts in childhood.
Autoimmune response where beta cells are targeted.
Body is unable to produce sufficient insulin and can’t store excess glucose as glycogen

60
Q

Type 2 diabetes causes and effects

A

Develops later in life related to age and diet.
Insulin is still produced however the body no longer responds to the insulin
Less insulin is produced

61
Q

Treatment of diabetes

A

Type 1
Insulin injections and check blood glucose levels regularly
Type 2
Control diet by eating more complex carbohydrates.

62
Q

Uncontrolled diabetes can lead to…

A 
Heart attack
Stroke
Toe, foot, leg infections requiring amputation
Blindness
Kidney failure
Tooth and gum disease
Pregnancy complications
63
Q

Insulin production

A

Cut out insulin gene from human DNA
Insert DNA into plasmid DNA
Insert plasmid into bacteria and grow bacteria
Separate the insulin.

64
Q

Advantages and disadvantages of insulin production

A

Mass produced
Cheap
Easy to do
Less ethical issues

Still some opposition to genetic engineering

65
Q

Define myogenic

A

Can initiate its own contraction

66
Q

Name the three types of receptors used in controlling the heart.

A 
Baroreceptors (pressure change) location aorta, carotid artery
Chemoreceptors (chemical) aorta, carotid artery, medulla oblongata
Stretch receptors (vena cava, aorta, carotid artery, muscles)
67
Q

How does movement of limbs affect heart rate.

A

Stretch receptors send a signal to the cardiac accelerator centre of the cardiovascular centre of the brain (medulla oblongata). The sympathetic nervous system then sends a signal via the accelerator nerve to the sino atrial node in the heart. This increases heart rate, stroke volume and contraction strength.

68
Q

Increased co2 effect on heart rate.

A

Chemoreceptors detect a drop in ph due to co2 production.
Signal sent to medulla oblongata to the cardiac acceleratory centre. The sympathetic nervous system then sends a signal to the sino atrial node via the accelerator nerve increasing heart rate, stroke volume and contraction strength.

69
Q

Adrenalin’s effect on the heart.

A

Adrenalin released from the adrenal gland into the blood is detected by beta receptors in the heart causing heart rate to increase.

70
Q

Increase in blood pressure’s effect on the heart.

A

Baroreceptors detect an increase in blood pressure. Signal is sent to the medulla oblongata (cardiovascular centre of the brain) to the cardiac inhibitory centre. The parasympathetic nervous system sends a signal via the vegus nerve to the sino atrial node in the heart. This causes heart rate, stroke volume and contraction strength to decrease.

A2 Biology (5 decks)

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