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Biology Paper 2 > B5 - Homeostasis and Response > Flashcards

B5 - Homeostasis and Response Flashcards

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1
Q

What is homeostasis?

A

The body maintaining a stable environment for optimum conditions for enzyme and cellular functions.

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2
Q

What 3 conditions are maintained by homeostasis?

A

Water content.
Body temperature.
Blood glucose levels.

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3
Q

Why are control systems needed?

A

To ensure conditions in your body remain stable even when the external environment changes.

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4
Q

What 3 things are needed in control systems?

A

Receptor
Co-ordination center
Effector

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5
Q

What organ helps to control body temperature?

A

The liver controls metabolic reactions so the amount of heat energy transferred to the environment is controlled.

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6
Q

What is negative feedback?

A

Opposing the change.

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7
Q

What is positive feedback?

A

Acts to amplify or encourage the change e.g. when a mother breastfeeds her child, the more milk she produces.

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8
Q

Why is feedback important in control systems?

A

To make adjustments and maintain optimum conditions in an organism.

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9
Q

What is the temperature regulation center in the brain called?

A

Hypothalamus.

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10
Q

What are the body’s responses to an increase in temperature?

A

Sweating - evaporation of water takes away heat energy from the surface of the skin.
Vasodilation meaning more heat is radiated away.

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11
Q

What are the body’s responses to a decrease in temperature?

A

Muscles contract rapidly - respiration allows muscles to contract. Respiration is an exothermic process so energy released raises body temperature.
Vasoconstriction - less heat radiated away.
Sweating stops.

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12
Q

What is thermoregulation?

A

The control of body temperature.

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13
Q

What temperature do enzymes work best at?

A

37 degrees celcius.

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14
Q

What is CNS?

A

Central Nervous System.

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15
Q

What are neurones?

A

Cells that transmit electrical impulses around the nervous system.

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16
Q

Which neurons carry electrical impulses from the receptors to the CNS?

A

Sensory neurons.

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17
Q

Which neurons carry electrical impulses from the CNS to the effectors?

A

Motor neurons.

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18
Q

What is a relay neuron?

A

Sends information from one neuron to another.

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19
Q

What is another term for neurons?

A

Nerve cells.

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20
Q

What 3 things make up the nervous system?

A

Brain, spinal cord, neurons.

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21
Q

What does the CNS consist of?

A

Brains and the spinal cord.

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22
Q

What does the peripheral nervous system consist of?

A

Neurons.

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23
Q

What are receptors?

A

Groups of specialised cells that detect changes in the environment, called stimuli, and turn them into electrical impulses.

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24
Q

Where are receptors often located?

A

In the sense organs - skin, eye and ear.

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25
Q

What are effectors?

A

Produce a response.

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26
Q

What is a coordination center?

A

Obtain information from the receptors.

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27
Q

What is the name of the microscopic gap between neurons?

A

Synapses.

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28
Q

How are electrical impulses transmitted?

A

A chemical (a neurotransmitter) diffuses across the synapse to stimulate a second neurone.

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29
Q

Define a reflex action?

A

A rapid, automatic response to a stimulus.

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30
Q

Give 4 examples of reflexes performed by the human body and why this reflex is important.

A

Blink reflex - prevents the eye from getting damaged.
Knee reflex - walking / running.
Ankle reflex - walking / running.
Pupil reflex - prevents damage from bright light.

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31
Q

What is an advantage of the spinal cord being a coordination center?

A

Reactions are quicker as shorter pathway between sensory neurons and spinal cord.

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32
Q

What are the steps of a response being carried out by the body caused by a stimulus?

A
  1. The receptors convert the stimulus into an electrical impulse.
  2. This electrical impulse travels along sensory neurons to the CNS.
  3. The CNS coordinates a response.
  4. An electrical impulse is sent along motor neurons to the effector which carries out the response.
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33
Q

What is the difference between a reflex pathway and a conscious pathway?

A

Within a reflex pathway, the co-ordination center is a relay neuron found in the spinal cord or unconscious part of the brain.
Within a conscious pathway, the co-ordination center is in the conscious part of the brain.

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34
Q

What is the order of events in the reflex arc?

A

Stimulus -> receptors -> sensory neuron -> relay neuron -> motor neuron -> effector -> response

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35
Q

What is accomodation?

A

The alteration of the lens’ shape in order to focus on near or distant objects.

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36
Q

What are the two main functions of all the structures found within the eye?

A

Focusing on near or distant objects.
Adapting to light.

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37
Q

What is the function of the retina?

A

Where light is focused.
Contains photoreceptive cells which detect colour and light intensity.

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38
Q

What is the function of the pupil?

A

The hole that allows light to enter the eye.

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39
Q

What is the function of the optic nerve?

A

Carries electrical impulses from the eye to the brain.

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40
Q

What is the function of the sclera?

A

The tough supporting wall of the eye.

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41
Q

What is the function of the cornea?

A

Transparent outer layer found at the front of the eye. Refracts light into the eye.

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42
Q

What is the function of the lens?

A

Focuses light onto the retina.

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43
Q

What is the function of the ciliary muscles?

A

Muscles connected to the lens by the suspensory ligaments.
Control the shape of the lens.

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44
Q

What is the function of the suspensory ligaments?

A

Connect the ciliary muscles to the lens and holds the lens in place.
Control the shape of the lens.

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45
Q

What happens to the ciliary muscles and suspensory ligaments when the object is near?

A

Ciliary muscles contract.
Suspensory ligaments slacken.

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46
Q

What is the shape of the lens when an object is near?

A

Curved, fat.

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47
Q

What is the muscles tension on the lens when an object is near?

A

Low.

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48
Q

What is the effect on the refraction of the light when the object is near?

A

Refracts light more.

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49
Q

What happens to the ciliary muscles and suspensory ligaments when the object is far?

A

Ciliary muscle relaxes.
Ligaments pull on lens.

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50
Q

What is the shape of the lens when an object is far away?

A

Flat, thin.

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51
Q

What is the muscle tension on the lens when an object is far?

A

High.

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52
Q

What is the effect on the refraction of the light when the object is far?

A

Refracts light less.

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53
Q

What is the action of the circular and radial muscles in dim light? (the iris)

A

Circular muscles relax.
Radial muscles contract.

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54
Q

What is the action of the circular and radial muscles in bright light? (the iris)

A

Circular muscles contract.
Radial muscles relax.

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55
Q

Why is the constriction of the pupil important?

A

It avoids retinal damage.

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56
Q

Why is the dilation of the pupil important?

A

Allows more light to enter the eye.

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57
Q

What is myopia?

A

Short-sightedness. Usually occurs when lens is too curved and as a result light is focused in front of the retina.

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58
Q

How can myopia be treated?

A

Use of a concave lens, which spreads out light rays so they can be focused on the retina.

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59
Q

What is hyperopia?

A

Long-sightedness. Occurs when the lens is too flat and light is not refracted enough so light is focused behind the retina.

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60
Q

How can hyperopia be treated?

A

With a convex lens. Which brings the light rays together so they can be focused on the retina.

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61
Q

What are the two types of contact lens?

A

Hard - rigid material, long-lasting, must be kept sterile.
Soft - flexible material, lasts a shorter amount of time, more comfortable.

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62
Q

What is laser eye surgery?

A

Use of lasers to fix visual defects in adults.

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63
Q

What is done in laser eye surgery to treat myopia?

A

Lasers reduce the thickness of the cornea so light is refracted less strongly.

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64
Q

What is done in laser eye surgery to treat hyperopia?

A

Alters the curvature of the cornea so light is refracted more strongly.

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65
Q

What are the two different methods of using a replacement lenses to fix visual defects?

A

A replacement lens can either be implanted into the eye along with the natural lens.
Or replace the lens altogether.

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66
Q

What are the risks of lens replacement?

A

Retinal damage, cataracts and infection.

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67
Q

How is temperature monitored by the body?

A

Thermoregulatory center has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory center.

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68
Q

What is a tropism?

A

The response of a plant to a specific stimulus.

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69
Q

What is phototropism?

A

Response of a plants shoot or root to light.

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70
Q

What is gravitropism?

A

Response of a plants shoot or root to gravity.

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71
Q

What is auxin?

A

A hormone which controls the growth of a plant’s shoot and roots. When auxin is unevenly distributed in a growing plant the rate of growth will be unequal.

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72
Q

What happens when an auxin is unevenly distributed in a growing plant?

A

The rate of growth will be unequal.

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73
Q

How do plant shoots show positive phototropism?

A

One side of the shoot is in the light, causing auxin to move to the shaded side. Cells are stimulated to grow at the shaded side. The shoot bends towards the light.

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74
Q

How do plants show negative gravitropism?

A

Auxin accumulates in the lower side due to gravity.
Cells on the lower side grow more, causing the shoot to bend away from the direction of gravity.

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75
Q

How do plant roots show positive gravitropism?

A

Auxin accumulates in the lower side causing cells to grow less. The root bends in the direction of gravity.

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76
Q

How do plants benefit from positive gravitropism?

A

More water and nutrients are available to plant roots.

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77
Q

How do plants benefit from positive phototropism?

A

Photosynthesis occurs at a faster rate.

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78
Q

What are gibberellins?

A

A type of plant hormone involved in seed germination.

79
Q

What is ethene?

A

A type of plant hormone involved in cell division and ripening.

80
Q

What are 3 uses of auxins?

A
  • Weed killers - cause cells to grow at a rapid rate causing it to die.
  • Rooting powder - causes new plants to grow very quickly.
  • Tissue culture - promotes growth of roots and shoots.
81
Q

State the use of ethene.

A

Control of food ripening in the food industry - allows them to be ripened just before they are sold.

82
Q

3 uses of gibberellins.

A
  • Termination of seed dormancy
  • Promotion of flowering
  • Increase of fruit size
83
Q

How is temperature monitored by the body?

A

Thermoregulatory center has receptors sensitive to blood temperature.
Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory center.

84
Q

Why are reflex actions important?

A

Aid survival by preventing harm to the body.

85
Q

What is the function of the cerebral cortex?

A

Controls consciousness, intelligence, memory and language.

86
Q

What is the function of the cerebellum?

A

Controls muscular co-ordination.

87
Q

What is the function of the medulla?

A

Controls unconscious activities e.g. breathing and heart rate.

88
Q

Why is investigation and treatment of the brain difficult (4)?

A
  • Brain is complex and delicate.
  • Brain is easily damaged.
  • Certain membranes prevent drugs from reaching the brain.
  • The exact function of each part of the brain is not know so surgery is difficult.
89
Q

What 3 methods are used by scientists to determine brain function?

A

Studying patients with brain damage.
Electrical stimulation of the brain.
MRI scans.

90
Q

What stimuli are the receptors of the eye sensitive to?

A

Light intensity and colour.

91
Q

What is the function of the nervous system?

A

Allows the body to react to it’s surroundings and coordinate an appropriate response.

92
Q

What is the function of the iris?

A

Muscles that controls the size of the pupil by contracting or relaxing. Allowing the eye to adjust to bright and dim lighting.

93
Q

What 2 types of responses are used in body control systems?

A

Nervous and chemical.

94
Q

What 2 things can the hypothalamus control?

A

Body temperature.
Water levels in the blood.

95
Q

What is the function of the pituitary gland?

A

Produces many different chemicals (hormones) which help control body systems.

96
Q

What is the brain stem?

A

The primitive part and controls basic functions that keep you alive.

97
Q

Is the cerebral cortex found in every animals brain?

A

No, only found in highly intelligent animals.

98
Q

What are insulin and glucagon?

A

Hormones produced by the pancreas that regulate glucose levels in the blood.

99
Q

What is the difference in structure between glucose and glycogen?

A

Glucose is a simple sugar which is a monomer, glycogen is a polymer of glucose and is a storage molecule found in animals.

100
Q

What response does the pancreas perform when blood glucose is too high?

A

Pancreas secretes insulin into the blood, insulin binds to liver and muscle cells, causing excess glucose to be converted into glycogen and stored.

101
Q

What response does the pancreas perform when blood glucose is too low?

A

Glucagon is secreted into the blood.
Glucagon binds to liver cells.
Causing glycogen to be converted into glucose and released into the blood.

102
Q

What is the effect on the liver and muscles when glucose levels are too high?

A

Glucose in the blood moves into the liver and muscles, where it is converted into glycogen for storage.

103
Q

What is the effect on the liver and muscles when glucose levels are too low?

A

Glucose is not converted into glycogen by the liver and muscles.
The liver converts glycogen into glucose.

104
Q

Why is glucose converted into glycogen?

A

Glucose would cause lots of water to travel into the cells which could result in them dying however glycogen doesn’t effect osmosis.

105
Q

How does type 1 diabetes occur?

A

When the body doesn’t produce insulin or enough insulin.

106
Q

How does type 1 diabetes effect your physical appearance?

A

No stores of glycogen - meaning you are underweight.

107
Q

How is type 1 diabetes treated?

A

Insulin injections before meals.
Limiting carbohydrate intake.
Pancreas and pancreatic cell transplants.

108
Q

What 2 factors effect how much insulin a person with type 1 should take?

A
  1. How much they have eaten - more insulin needs to be injected.
  2. How much they have exercised - less insulin needed to be injected (as muscles take in more glucose when exercising).
109
Q

What is type 2 diabetes?

A

When the body cells stop responding to insulin, so the cells won’t take glucose in from the blood stream, leading to an uncontrolled glucose concentration.

110
Q

Why does type 1 diabetes lead to weight loss?

A

The lack of a sufficient supply of insulin prevents glucose from going into cells to release energy therefore the body starts using fat and muscle stores instead.

111
Q

What are the factors that could cause type 2 diabetes?

A

Age and obesity.

112
Q

How is type 2 treated?

A
  • losing weight
  • exercising more
  • controlled diet
  • drugs which increase insulin effectiveness
113
Q

Why is blood glucose concentration part of the negative feedback loop?

A

The action of the secreted hormone will bring blood glucose levels back to a normal concentration. Opposes the change.

114
Q

What are 4 symptoms of type 1?

A

Frequent urination
Thirst
Tiredness
Weight loss

115
Q

What age group is type 1 diagnosed at?

A

Childhood - teenagers

116
Q

What age range does type 2 usually become diagnosed?

A

Over 40

117
Q

What do MRI scans enable scientists to do?

A

To link the loss of a certain function with a particular region of the brain.

118
Q

Where are amino acids broken down?

A

Liver

119
Q

Why is a decrease in body temperature beneficial to animals during hibernation?

A

Loses less energy.
Body energy store lasts longer.

120
Q

Why does an animal have a higher body temperature when it is active?

A

Activity requires energy from respiration.
Respiration releases heat which increases body temperature.

121
Q

Why does the dilation of blood vessels in the skin decrease body temperature?

A

More blood flow near the surface of the skin.
More heat is lost.
Cools blood which cools the body.

122
Q

What is the name of the coordination system involving hormones?

A

Endocrine system

123
Q

What type of organ secretes hormones?

A

Glands

124
Q

What gland controls many other glands in the body?

A

Pituitary gland

125
Q

Why is the pituitary gland referred to as the master gland?

A

Secretes a wide range of hormones, some of which stimulate other endocrine glands.

126
Q

4 roles of pituitary gland.

A

Secretes:
- growth hormones
Stimulates:
- thyroid gland
- ovulation and oestrogen
- production of sperm and testosterone

127
Q

What is the role of the thyroid gland?

A

Secretes hormone thyroxine - controls metabolism, heart rate and temperature.

128
Q

What is the role of the pancreas?

A

Secretes insulin - controls blood glucose levels.

129
Q

What is the role of the adrenal gland?

A

Secretes adrenaline - fight or flight response.

130
Q

What is the role of the ovaries?

A

Secretes oestrogen - which co-ordinates the menstrual cycle and controls female sexual characteristics.

131
Q

What is the role of the testes?

A

Secretes testosterone - coordinates sperm and male characteristics.

132
Q

Where is ADH secreted?

A

Pituitary gland.

133
Q

In what ways is water lost from the body?

A

Sweating
Urine (some reabsorbed by kidney)
Exhalation

134
Q

In what ways are ions lost from the body?

A

Sweating
Urine (some reabsorbed by kidney)

135
Q

How are excess amino acids excreted from the body?

A

Deaminated in liver to form ammonia.
Ammonia converted into urea
Urea excreted via sweat and urine.

136
Q

How do kidneys maintain the balance of water and other substances in the body?

A

Filter blood to remove urea.
Reabsorb useful molecules e.g. glucose ions water.

137
Q

What does ADH control?

A

The water content of blood.

138
Q

How does the body respond to too little water in blood?

A

Releases more ADH.
More water absorbed by kidneys.
Less water lost in urine.
Blood water level returns to normal.

139
Q

How does the body respond to too much water in blood?

A

Releases less ADH.
Less water absorbed by kidneys.
More water lost in urine.
Blood water level returns to normal.

140
Q

What are the effects of adrenaline?

A

Increase in heart and breathing rate.
Dilation of pupils
Glycogen converted to glucose.
Blood diverted to muscles.

141
Q

What is thyroxine’s releases stimulated by?

A

TSH - thyroxine stimulating hormone released by pituitary gland.

142
Q

Why is kidney failure dangerous?

A

Unable to filter blood properly leads to:
Build up of toxic chemicals - urea
An uncontrolled ion and water balance

143
Q

State 2 ways of treating kidney failure.

A

Dialysis
Transplant

144
Q

What is the function of reproductive hormones during puberty?

A

Males - sexual characteristics
Females - sexual characteristics and maturation of eggs.

145
Q

Main male reproductive hormone.

A

Testosterone

146
Q

Main female reproductive hormone.

A

Oestrogen

147
Q

Describe events of menstrual cycle.

A

Uterus lining thickens and eggs mature in ovaries
An egg is released, lining remains thick
If egg is fertilised pregnancy may occur, if not both egg and uterus lining are shed during mensturation.

148
Q

What is ovulation?

A

Release of a mature egg from the ovaries - every 28 days

149
Q

Name 4 main hormones in the menstrual cycle.

A

Oestrogen
Progesterone
FSH
LH

150
Q

What is the role of FSH?

A

Secreted by pituitary gland.
Controls the maturation of eggs.
Triggers the production of oestrogen.

151
Q

What is the role of oestrogen?

A

Causes regrowth of uterus lining.
Triggers production of LH.
Stops release of more FSH.

152
Q

What is the role of LH?

A

Triggers ovulation.

153
Q

What is the role of progesterone?

A

Secreted from follicle of ovary.
Sustains uterus lining and inhibits FSH and LH.

154
Q

What is adrenaline?

A

Hormone secreted in the adrenal gland in times of stress.

155
Q

How is the release of thyroxine controlled by negative feedback?

A

Receptors detect low levels in the blood.
Pituitary gland releases more TSH.
More thyroxine produced by Thyroid gland.
Blood thyroxine returns to normal.

156
Q

Name 4 hormones released in the menstrual cycle.

A

FSH (follicle stimulating hormone)
LH (luteinizing hormone)
Oestrogen
Progesterone

157
Q

What gland is FSH and LH released from?

A

Pituitary gland.

158
Q

What gland is oestrogen and progesterone released from?

A

Ovaries

159
Q

What is the function of FSH?

A

Causes egg cell to mature in ovaries. Stimulates ovaries to release oestrogen.

160
Q

What is the function of LH?

A

Causes mature egg cell to be released. Stimulates release of progesterone.

161
Q

What is the function of progesterone?

A

Maintains the uterus lining.

162
Q

What is the function of oestrogen?

A

Causes uterus lining to thicken. Inhibits FSH and promotes LH.

163
Q

What does the pill contain?

A

Oestrogen and/or progesterone.

164
Q

How does the pill prevent pregnancy?

A

Prevents egg cell maturing and being released.

165
Q

What are the cons of the pill?

A

Doesn’t protect against STD’s.
Increased risk of breast cancer.
Headaches and nausea.

166
Q

What is a intrauterine device?

A

T-shaped device inserted into uterus.

167
Q

How does a intrauterine device prevent pregnancy?

A

Kills sperm
Prevents implantation of a fertilised egg cell.

168
Q

What does the plastic version of a intrauterine device do?

A

Release progesterone.

169
Q

What is the only contraceptive method that protects against STD’s?

A

Condoms

170
Q

What are the cons of condoms?

A

Can let semen through if damaged.

171
Q

What are diaphragms?

A

Prevents sperm passing through the cervix.

172
Q

What do diaphragms have to be used with?

A

Spermicide

173
Q

What does surgical contraception involve?

A

Cutting or tying the fallopian tubes or sperm ducts.

174
Q

What are the cons of tying the fallopian tubes or sperm ducts?

A

Chance they will re-join naturally.
Doesn’t prevent against STD’s.

175
Q

How long is the menstrual cycle?

A

Around 28 days.

176
Q

When is a woman most fertile?

A

Around ovulation (day14). Fertilisation must take place in the fallopian tube.

177
Q

What is ovulation?

A

When an egg cell is released from the ovaries.

178
Q

What is a natural contraceptive method?

A

Avoiding intercourse when the egg may be in the fallopian tubes. (rhythm method)

179
Q

What are the cons of the rhythm method?

A

Unreliable.
Doesn’t protect against STD’s.

180
Q

What can women take when they have low levels of hormones?

A

FSH and LH to stimulate ovulation.

181
Q

What are the pros of taking hormones to stimulate ovulation?

A

Help people get pregnant.
Non-invasive in tablet form.

182
Q

What are the cons of taking hormones to stimulate ovulation?

A

Doesn’t always work - might need to be repeated - expensive.
Too many eggs released results in multiple pregnancies.

183
Q

Which system are your kidney’s part of?

A

Excretory system / urinary system

184
Q

What is the function of the kidneys?

A

Control water balance.
Remove toxic substances.
Control balance of salts.

185
Q

Where is ADH secreted?

A

Pituitary gland.

186
Q

What does ADH actually do to the kidney tubules that allows it to absorb more water?

A

It increases the permeability of the tubules.

187
Q

What is kidney dialysis?

A

Use of specialist machinery to carry out function of the kidneys.

188
Q

What does dialysis fluid contain?

A

Same concentration of ions and glucose as the blood, so only waste molecules are lost from the blood through osmosis.

189
Q

What is urea?

A

A waste product.
Made in liver through deamination.

190
Q

Why is water regulation important?

A

Cells could swell and burst if water levels are too high.
Shrink if water levels are too low.

191
Q

Explain how filtration in the kidneys work.

A

Tubules absorb anything small e.g. water, glucose, amino acids, and urea.
Doesn’t absorb large molecules.

192
Q

What is selective reabsorbtion?

A

When all of glucose, some water (and useful molecules) are aborsbed back into blood)

193
Q

What is the hypothalamus job in water regulation?

A

Detects water levels in blood stream.

194
Q

What type of system regulates water content levels?

A

Negative feedback system

Biology Paper 2 (3 decks)

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