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Biology > 6 - Responding to Change > Flashcards

6 - Responding to Change Flashcards

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1
Q

What does the Cell body of a neurone contain?

A

Contains cytoplasm, nucleus, mitochandria and ribosomes

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2
Q

Dendrites

A

branched extensions of the cell body

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3
Q

Axon - size

A

single long fibre, can be as long as a metre and less than a micrometre wide

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4
Q

Schwann cells

A

Wrap around the axon many times, providing electrical insulation

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5
Q

Myelin Sheath

A

Made of Schwann cells
Rich in Myelin

Not all neurons are myelinated but myelinated neurons transmit nerve impulses faster

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6
Q

Nodes of Ranvier

A

Gaps between adjacent Schwann cells where there is no myelin sheath

Gaps are 2-3 micrometres wide and occur every 1-3 mm

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7
Q

2 main receptors in the human eye

A

Rod Cells

Cone cells

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8
Q

Which eye receptor has a high and which has a low sensitivity to light?

A

Rod - high sensitivity

Cone - low sensitivity

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9
Q

Visual acuity

A

the ability to distinguish between 2 close objects

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10
Q

Which eye receptor is more numerous?

A

Rod cells

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11
Q

How are rod cells distributed?

A

Evenly distributed on the retina but absent in the fovea

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12
Q

How are cone cells distributed?

A

Mainly at the fovea - a single point in the retina

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13
Q

Pigment in rod cells

A

Rhodospin

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14
Q

Pigment in Cone cells

A

Lodospin

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15
Q

Rhodospin

A

Pigment in rod cells

Detects light and dark

Monochromatic - only detects one wavelength of light

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16
Q

Lodospin

A

Pigment in Cone cells

Detects colour

Trichromatic - divided into 3 types, each detecting different wavelengths of light

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17
Q

How is light detected after it has been absorbed by photoreceptor cells?

A

Absorption of light induces a change in the membrane permeability of pigments

Na+ flood into the cell and a generator potential is established

If the generator potential reaches the threshold, a nerve impulse flows along a bipolar neurone

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18
Q

Role of dendrite

A

Carries nervous impulses towards a cell body

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19
Q

Axon - role

A

Carries nervous impulses away from the cell body

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20
Q

Where do motor neurons carry impulses?

A

CNS –> effector organs

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21
Q

What maintains resting potential?

A

Sodium-Potassium Pumps

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22
Q

What is the neurone membrane impermeable to?

A

Na+

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23
Q

What is potential differencee at resting state known as?

A

Resting Potential

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24
Q

Hyperpolarisation

A

The periodd after depolarization where the potential difference becomes slightly more negative than the resting potential

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25
Q

What happens to ion channels during the refractory period?

A

Close

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26
Q

Where does depolarization take place?

A

Along the neurone membrane

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27
Q

What diffuse sideways along the neurone axon in depolarization?

A

Na+

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28
Q

What is the effect of reaching threshold on sodium ion channels?

A

Sodium Ion channels open

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29
Q

Approximate threshold value of membrane potential, before the membrane becomes depolarised

A

-55mV

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30
Q

Diffusion of sodium ions in a neurone

A

When an action potential Is generated, there are more Na+ inside the neurone than outside, so some of these diffuse sideways along the neurone axon

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31
Q

How does Depolarisation of neurones happen?

A

Presence of sodium ions creates a change in potential difference further along the neurone membrane. this part of the neurone now becomes depolarised

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32
Q

Wave of depolarisation

A

Sodium diffuse all along the neurone in this way and a wave of depolarisation flows along the neurone

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33
Q

How does the refractory period effect the wave of depolarisation?

A

Makes it travel in just one direction

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34
Q

Structure in a neurone which carries nervous impulses away from the body

A

Axon

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35
Q

Resting potential of a neurone

A

-70mV

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36
Q

The refractory period

A

Period of hyperpolarisation in an action potential

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37
Q

Saltatory Conduction

A

The nervous impulses jumps from one node to the next

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38
Q

What happens to the postsynaptic membrane after an inhibitory neurootransmitter binds to the receptor

A

Hyperpolarisation

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39
Q

Summation

A

The process where neurotransmitters from multiple neurones are summed together to produce a response

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40
Q

Spatial Summation

A

The process where multiple presynaptic neurones form a junction with a single neurone

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41
Q

Temporal Summation

A

The process where multiple nerve impulses arrive at the same synaptic knob within a short period of time

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42
Q

Where is a neuromuscular junction between?

A

Motor neurone + Muscle cell

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43
Q

What happens after the arrival of the action potential at the synaptic knob?

A

The action potential depolarises the membrane

Voltage-gated Calcium ion channels open

Calcium ions diffuse into the synaptic knob

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44
Q

What are Cholinergic Synapses?

A

Synapses which use acetylcholine as a neurotransmitter

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45
Q

The name of the gap between the cells at a synapse

A

The synaptic cleft

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46
Q

The effect of an inhibitory neurotransmitter on the postsynaptic cell

A

It prevents an action potential from being generated in the postsynaptic cell

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47
Q

Enzyme that breaks down acetylcholine in the synaptic cleft

A

Acetylcholinesterase

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48
Q

Result of depolarisation of the postsynaptic membrane at a Cholinergic synapse

A

Generation of an action potential

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49
Q

The effect of an excitatory drug on the nervous system

A

They stimulate the nervous system to produce more action potentials

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50
Q

(Negative Feedback) - Causes a change in the body’s condition

A

Stimulus

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51
Q

(Negative Feedback) - detects change and relays information the the CNS

A

Receptor

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52
Q

Negative Feedback - counteracts change

A

Effector

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53
Q

Benefits of multiple feedback mechanisms

A

More control

Faster response

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54
Q

How do multiple feedback mechanisms provide more control?

A

The body can respond to multiple changes away from the optimum

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55
Q

How do multiple feedback mechanisms provide a faster response?

A

The body can respond in more ways to a change away from the optimum

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56
Q

2 Reasons for maintaining blood glucose concentration

A

Meeting respiratory demand

Maintaining Water potential

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57
Q

Effect of low glucose levels on respiration

A

Respiration will slow

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58
Q

Effect of low glucose levels on water potential

A

Decrease water potential of the blood

Water will move out of the tissues into the blood by osmosis, causing dehydration of the cells and cell death

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59
Q

Glycogenesis

A

When blood glucose concentration is too high, the liver cells produce enzymes that convert glucose into glycogen. This glycogen is then stored in liver cells

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60
Q

Glycogenolysis

A

When blood glucose concentration is too low, the liver cells produce enzymes that break down the glycogen stored in cells toglucose

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61
Q

Glucogenesis

A

When blood glucose concentration is too low, liver cells also form glucose from glycerol and amino acids

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62
Q

What is blood glucose concentration controlled by?

A

Homeostasis

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63
Q

Normal blood glucose concentartion

A

90mg 100cm3

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64
Q

3 processes ininvolved in controlling blood glucose conc which take place in the liver

A

Glycogenolysis

Glycogenesis

Gluconeogenesis

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65
Q

What type of cells in the pancreas detect high blood glucose levels?

A

Beta cells

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66
Q

2 hormones responsible for restoring blood glucose if the cncentartion is too low

A

Adrenaline

Glucagon

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67
Q

What enzyme is activated upon binding of adrenaline or glucagon to receptors

A

Adenylate Cyclase

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68
Q

What attaches skeletal muscle to bones?

A

Tendons

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69
Q

Agonist

A

The contracting muscle

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70
Q

Antagonist

A

Relaxing muscle

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71
Q

What are muscle fibers?

A

Long, specialized cells and bundles of muscle fiber make up skeletal muscle

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72
Q

Sarcolemma

A

The membrane of muscle fibres

Folds inwards to the sarcoplasm at certain points

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73
Q

What is the membrane of muscle fibres known as?

A

Sarcolemma

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74
Q

The name of the inwards folds of the sarcolemma

A

Transverse (T) Tubules

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75
Q

Importance of T tubules

A

Initiating muscle contraction

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76
Q

Sarcoplasm reticulum

A

Organelle in the cytoplasm which stores Calcium ions

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77
Q

What do muscle fibres contain lots of?

A

Mitochondria and nuclei

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78
Q

Myofibrils

A

Cylindrical organelles that run along the length of muscle fibres

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79
Q

Where are myofibrils located?

A

At the site of muscle contraction

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80
Q

What are myofibrils made up of?

A

Multiple units which run end-to-end along the myofibril, known as sarcomeres

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81
Q

What is the end of the sarcomere known as?

A

The Z-line

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82
Q

2 types of myofilament

A

Thick myofilament

Thin myofilament

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83
Q

What is thick myofilament made from?

A

Myosin protein

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84
Q

What is thin myofilament made from?

A

Actin protein

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85
Q

How are myosin and actin filaments arranged?

A

In alternating patterns in sarcomeres

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86
Q

A-band

A

Region where myosin and actin filaments overlap

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87
Q

H zone

A

Region with only myosin filaments

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88
Q

I-band

A

Region with only actin filament

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89
Q

When is muscle contraction initiated?

A

When an action potential arrives at a neuromuscular junction from a motor neurone

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90
Q

What happens once an action potential arrives at a neuromuscular junction from a motor neurone?

A

Depolarisation of the sarcolemma which spreads along the T tubules and into the sarcoplasm

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91
Q

What does depolarisation of the T tubules stimulate?

A

Sarcoplasmic reticulum to release Calcium ions into the sarcoplasm

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92
Q

What do Calcium ions bind to in muscle contraction?

A

A protein attached tto tropomyosin

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93
Q

What is the effect of Calcium ions binding to a protein attached to tropomyosin?

A

Protein changes shape, causing tropomysoin to be moved so that it is no longer blocking the actin-myosin binding site

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94
Q

What is the bond between actin and myosin known as?

A

actin-myosin cross bridge

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95
Q

Enzyme which hydrolyses ATP

A

ATP Hydrolase

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96
Q

The effect of the influx of Calcium ions into the sarcoplasm

A

Allows actin and myosin filaments to bind, creating an actin-myosin cross bridge

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97
Q

What activates ATP Hydrolase?

A

Calcium ions

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98
Q

What effect does the energy released from ATP hydrolysis have on myosin?

A

Causes the myosin head to bend

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99
Q

What causes the actin filament to be pulled by the myosin head?

A

The actin-myosin cross bridge

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100
Q

What is the effect of the movement of the myosin head on the actin filament?

A

Causes the actin filament to slide past the myosin filament

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101
Q

What happens to the cross bridge and the myosin head after the actin filaments have slid past the myosin filaments?

A

The cross bridge is broken and the myosin head is no longer attached to the actin filament

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102
Q

What happens to the myosin head once it is released from the actin binding site?

A

It bends back to its original position and the myosin forms a new cross bridge with a binding site further along the actin filament

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103
Q

What is the overall result as actin filaments are pulled past the myosin filaments?

A

shortening of the sarcomere

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104
Q

What does shortening of the Sarcomeres cause?

A

Muscle contraction

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105
Q

When is muscle contraction stopped?

A

When the muscle cells are no longer stimulated

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106
Q

What happens to calcium ions once muscle contraction is stopped?

A

Actively transported back into the sarcoplasm reticulum

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107
Q

What is the effect of the removal of Calcium ions on the tropomyosin?

A

The protein attached to tropomyosin undergoes a conformational change, causing tropomyosin to shift so that it is blocking the actin-myosin binding sites

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108
Q

Effect of stopping muscle contraction on the sarcomere

A

Lengthens

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109
Q

Where are calcium ions released from?

A

Sarcoplasmic Reticulum

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110
Q

What causes myosin heads to bend?

A

Energy released from ATP

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111
Q

Where does actin overlap with myosin?

A

Middle of the sarcomere

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112
Q

Sarcomere

A

Units which run along myofibrils, found at the site of muscle contraction

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113
Q

Where are slow twitch fibres found?

A

Muscles used for posture, such as the back and neck

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114
Q

Where are fast twitch fibres found?

A

Mainly in muscles such as the arms and legs

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115
Q

Slow twitch fibres - adaptatiion to functionWhat are slow twitch fibres adapted for?

A

Endurance and slow movement over long periods of time

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116
Q

Size of slow twitch fibres

A

Long and thin

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117
Q

Speed of low twitch fibres

A

Fatigue slowly and contract slowly

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118
Q

What are fast twitch fibres adapted for?

A

Fast or strong movement over short periods of time

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119
Q

Size of fast twitch fibres

A

Short and wide

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120
Q

Speed of fast twitch fibres

A

Fatiguequickly and contract quickly

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121
Q

Energy source for slow twitch fibres

A

Energy released through aerobic respiration

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122
Q

Energy source for fast twitch fibres

A

Energy released through anaerobic respiration

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123
Q

What do slow twitch fibres have lots of?

A

Mitochondria

Capillaries

Myoglobin

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124
Q

What do slow twitch fibres have less of?

A

Glycogen

Phosphocreatine

Sarcoplasmic reticulum

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125
Q

What do fast twitch fibres have lots of?

A

Glycogen

Phosphocreatine

Sarcoplasmic reticulum

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126
Q

What do fast twitch fibres have less of?

A

Mitochondria

Capillaries

Myoglobin

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127
Q

Myoglobin

A

Pigment which stores oxygen

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128
Q

How can organisms increase their chances of survival?

A

Detecting a change and responding accordingly

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129
Q

What can organisms detect changes in?

A

External environment

Internal environment

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130
Q

3 components involved in coordinating a response

A

Stimulus

Receptors

Effectors

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131
Q

Phototropism

A

Growth in response to direction of light

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132
Q

Phototropism in roots and shoots

A

Shoots are positively phototropic as they grow towards light

Roots are negatively phototropic as they grow away from light

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133
Q

Directional responses in plants

A

They regulate growth in response to a direction stimuli

Directional growth responses are called tropisms

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134
Q

Tropisms

A

Directional growth responses

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135
Q

Gravitropism

A

Growth in response to direction of gravity

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136
Q

How do roots and shoots show gravitropism?

A

Shoots are negatively gravitropic as they grow upwards, away from the gravitational pull

Roots are positively gravitropic as they grow downwards, towards the gravitational pull

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137
Q

Indoleacetic acid (IAA)

A

A type of auxin that controls the tropic response in plants

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138
Q

How is IAA transported around the plant?

A

Short distances by diffusion or active transport

Longer distances in the phloem

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139
Q

What happens when a plant detects directional stimuli?

A

IAA is transported to different parts of the plant, creating an uneven distribution of IAA

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140
Q

What happens when the distruvtion of IAA is uneven?

A

A directional growth response occurs

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141
Q

Phototropism in shoots

A

Shoots are positively phototropic

If a shoot is exposed to an uneven light source, IAA is transported to the more shaded part

A higher concentration of IAA in the shaded parts cause cells in the shaded area to elongate

Cell elongation causes the shoot to bend towards the light

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142
Q

Phototropism in roots

A

Roots are negatively phototropic

If a root is exposed to an uneven light source, IAA is transported to the more shaded part

A higher concentration of IAA in the shaded parts inhibits cell elongation on the shaded part

The root bends away from the light

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143
Q

Gravitropism in shoot

A

Shoots are negatively gravitropic

If a shoot is exposed to an uneven gravitational pull, IAA is transported to the underside

A higher concentration of IAA in the underside causes cells in the underside to elongate

Cell elongation causes the shoot to bend away from the gravitational pull

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144
Q

Gravitropism in roots

A

Roots are positively gravitropic

If a root is exposed to an uneven gravitational pull, IAA is transported to the underside

A higher concentration of IAA in the underside inhibits cell elongation on the lower side

The root bends towards the gravitational pull

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145
Q

2 ways in which simple animals respond to change

A

Taxes

Kineses

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146
Q

Taxes

A

A positively or negatively directionl stimulus

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147
Q

Kineses

A

The stimulus is non-directional

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148
Q

Why are damp / humid environments more favourable for wodlice?

A

Reduce water loss

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149
Q

Reflexes

A

Automatic response to stimuli

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150
Q

How reflexes work

A

Quick and automatic

Help an organism respond quickly to a harmful stimulus

The information is not processed in the brain and no decision is made about the response

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151
Q

3 types of neurone involved in the reflex arc

A

Sensory

Relay

Motor

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152
Q

Reflex arc in response to heat

A

Thermoreceptors in the skin detect a heat stimulus

Sensory neurone carries impulse from thermoreceptors to relay neurone in the spinal cord

Relay neurone carries impulse to motor neurone

Motor neurone carries impulses to effector

Arm moves away from hot object

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153
Q

What does IAA stand for?

A

Indoleacetic acid

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154
Q

2 important features of receptors

A

Specificity

Generatpr potentials

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155
Q

Specificity of receptors

A

Only respond to specific stimuli

This means that a receptor which responds to light will not respond to temperature or pressure

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156
Q

Generator potentials in Receptors

A

Receptors connect with sensory neurones. When stimulated, the receptor creates a generator potential in the sensory neurone

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157
Q

Pacinian Corpuscle

A

Mechanoreceptor found in the skin

Mechanoreceptors respond to changes in pressure to establish a generator potential

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158
Q

What does the pacinian corpuscle consist of?

A

Concentric rings of connective tissue that surrounds a sensory neurone

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159
Q

Resting state of the Pacinian Corpuscle

A

The charge inside the neurone is more negativ than the outside (-70mV)

This is because there are more Na+ ions outside the neurone than inside

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160
Q

Potential difference

A

Difference in charge across the cell membrane

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161
Q

What happens when pressure is applied to the pacinian corpuscle?

A

The rings of connective tissue apply pressure on the sensory neurone

The sensory neurone has stretch-mediated Na+ channels, these channels normally retsrict the movement of Na+ ions

Applied pressure causes the stretch-mediated Na+ channels to open

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162
Q

Generator potential in the pacinain corpuscle

A

Na+ ions flood into the sensory neurone through the open Na+ channels

there are now more Na+ ions insode the neurone than outside, so the charge inside the neurone becomes more positive than the outside, changing the potential difference

The generator potential has been established

163
Q

Action Potential in the Pacinian corpuscle

A

If the generator potential reaches the threshold level (about -50mV) then an action potential is produced in the sensory neurone

164
Q

Sensitivity to light in rod and cone cells

A

Rod cells - highly sensitive to light

Cone cells - less sensitive to light

165
Q

Visual acuity

A

The ability to distinguish between close objects or 2 points

166
Q

Visual acuity in rod and cone cells

A

Rod cells - low visual acuity

Cone cells - high visual acuity

167
Q

Number and distribution of rod cells

A

Highly numerous

Evenly distributed on the retina but absent in the fovea

168
Q

Number and distribution of cone cells

A

Fewer cells than rod cells

Distributed mainly at a single point in the retina called the fovea

169
Q

What do photoreceptors synapse with?

A

A bipolar relay neurone

170
Q

What does each bipolar neurone synapse with?

A

A ganglion cell - sensory neurone

171
Q

How do axons of ganglion send a signal to the brain?

A

Leave the eye via the optic nerve to send a signal to the brain

172
Q

What are differences in sensitivity to light due to?

A

Differences in how rod and cone cells connect to bipolar neurones

173
Q

How do cone cells form a synapse?

A

Each cone cell synapses with a single bipolar neurone

Sufficient light must stimulate the cone cell to generate an action potential in the bipolar neurone

174
Q

How do rod cells form synapses?

A

Several rod cells synapse with the same bipolar neurone

Light stimulating a single rod cell may not be sufficient to generate an action potential in the bipolar neurone

175
Q

Spatial Summation

A

Several rod cells synapse with the same bipolar neurone

This means that the cumulative stimulation of more than one rod cell can create an action potential in the bipolar neurone

176
Q

What does spatial summation result in?

A

Retinal Convergence - the idea that several rod cells generate a signal in a single sensory neurone

177
Q

Steps involved in the detection of light

A
  1. light is absorbed by pigments in photoreceptor cells
  2. Generator potential is created in pigment cells
  3. Nerve impulse flows along a bipolar neurone
178
Q

Sinoatrial node - location

A

Wall of the right atrium

179
Q

Sinoatrial node - role

A

Acts as a pacemaker by transmitting waves of electrical activity along the walls of the atria at regular intervals

180
Q

Effect of the electrical waves from the SAN

A

Cause the left and right atria to contract together

This forces blood into the ventricles

181
Q

Why can wavs of electrical activity not pass from the atria to the ventricles?

A

Due to a collection of non-conducting tissues

This creates a delay to ensure the atria are empty before the ventricles begin to contract

182
Q

What does the wave of electrical activity pass through after atria contraction?

A

Through the atrioventricular valve, to the bundle of His

183
Q

Bundle of His

A

A collection of conducting tissue that transmits the electrical activity to the apex of the heart and around the ventricle walls along fibres called the purkyne fibres

184
Q

What happens as the waves of electrical activity pass along the Purkyne fibres?

A

The ventricles contract together

Blood is forced out of the ventricles and out of the heart

185
Q

How does the SAN act as a pacemaker?

A

By transmitting waves of electrical activity along the walls of the atria at regular intervals

186
Q

2 main receptors in controlling heart rate

A

Chemoreceptors

Baroreceptors

187
Q

Chemoreceptors

A

Sensitive to changes in CO2 concentration

Found in the aortic body, in the wall of the atria

Found in the carotid body, in the wall of the carotid artery in the neck

188
Q

Effect of increased CO2 concentration on heart rate

A

Heart rate increases

189
Q

Baroreceptors

A

Sensitive to changes in blood pressure

Found in the walls of various arteries but particularly in the carotid sinus

190
Q

Where do chemoreceptors and baroreceptors send a signal to when stimulated?

A

Medulla Oblongata

191
Q

Cardiovascular Centre

A

Region in the medulla which modifies heart rate

192
Q

2 regions of the cardiovascular centre

A

Cardio-inhibitory centre

Cardio-acceleratory centre

193
Q

Nerve impulses from the cardiovascukar centre

A

Sent from these centres along the autonomic nervous system to the sinoatrial node

194
Q

High blood pressure

A

Detected by baroreceptors

Impulses are sent from the medulla along parasympathetic neurones to the sinoatrial node

Acetylcholine is released

Heart rate slows down and blood pressure decreases

195
Q

Low blood pressure

A

Detected by baroreceptors

Impulses are sent from the medulla along sympathetic neurones to the SAN

Noradrenaline is released

Heart rate rises and blood pressure increases

196
Q

Low CO2 / High O2

A

Detected by chemoreceptors

Impulses are sent from the medulla along the parasympathetic neurones to the SAN

Acetylcholine is released

Heart rate slows down and CO2 levels increase / O2 levels decrease

197
Q

Low O2 / High CO2

A

Detected by chemoreceptors

Impulses are sent from the medulla along sympathetic neurones to the SAN

Noradrenaline is released

Heart rate rises and O2 levels increase / CO2 levels decrease

198
Q

Which neurotransmitter is released in response to Low O2 / High CO2

A

Noradrenaline

199
Q

In which artery walls are baroreceptors mainly found?

A

Carotid artery

200
Q

Relay Neurones

A

Intermediate neurones

Recieve impulses from a sensory neurone and relay them to motor neurones

201
Q

Role of dendrites

A

Carry nervous impulses towards a cell body

202
Q

Role of axons

A

Carry nervous impulses away from the cell body

203
Q

How is resting potential maintained?

A

Sodium-potassium pumps in the neurone membrane

204
Q

How d positive ions build up outside of the cell?

A

Na-K pumps

3Na+ ions are actively transported out of the neurone by the pumps for every 2K+ that are transported in

205
Q

Potassium ion channels in the neurone membrane

A

Membrane is permeable to K+ ions

When K+ ions are transported into neurones, they can diffuse back out

The neurone membrane is also impermeable to Na+ ions so the ions cannot diffuse back into the cell after they have been transported out

206
Q

When do Na+ ion channels in the cell membrane open?

A

When the cell is stimulated

207
Q

What happens if the potential difference rises above the threshold value (-55mV)

A

The membrane will become depolarised

208
Q

More sodium channels open in the depolarised membrane

A

Sharp increase in potenttial difference to about +30mV

209
Q

All-or-nothing Principle

A

If the potential difference reached the threshold, depolarisation will always take place and the change in potential difference will always be the same

If the stimulus is stronger, action potentials wil be produced more frequently but their size will not increase

210
Q

What happens after the neurone membrane hs depolarised to 30mV?

A

Na+ ion channels close and K+ ion channels open

K+ ions are transported back out of the neurone and the potential difference becomes more negative

Repolarisation

211
Q

Hyperpolarisation

A

Short period after repolarisation of a neurone where the potential difference becomes slightly more negative than the resting potential

Prevents the neurone from being restimulated instantly

212
Q

Refractory period

A

Period of depolarisation preventing the neurone from being restimulated instantly

213
Q

What happens after the refractory period?

A

The K+ ion channels close and the membrane returns to its resting potential

214
Q

Action potential

A

The process where a neurone is depolarised and returns to resting potential

215
Q

Stages in depolarisation of neurone cell membrane

A

Stimulation

Depolarisation

Repolarisation

Hyperpolarisation

216
Q

How does the refractory period affect the wave of depolarisation?

A

Makes it travel in one direction

217
Q

Why does the myelin sheath act as elctrical insulator?

A

It is impermeable to Na+ and K+

218
Q

Saltatory conduction

A

Nervous impulses jump from one node to the next

219
Q

Effect of temperature on nerve impulse

A

An increase in temp increases KE

Ions move across the membrane more rapidly when they have more KE

220
Q

Effect of axon diameter on nerve impulse

A

Giant axons are found in the giant squid and allow it to have a rapid escape response

Greater axon diameter means there is a greater surface area for the movement of ions across the cell membrane

221
Q

Synaptic cleft

A

Gap between cells

When an action potential reaches a synapse, it must be transmitted across the synaptic cleft

222
Q

Presynaptic neurone

A

The neurone before the synapse

When an action potential reaches the end of the neurone, it is transmitted across the presynaptic membrane to the postsynaptic membrane or to an effector cell

223
Q

Synaptic Knob

A

The end of the axon of the presynaptic neurone

Swelling which contains synaptic vesicles

location where the nerve impulse is transmitted across the synaptic cleft

Contains lots of mitochondria, as it needs lots of energy to synthesise neurotransmitters

224
Q

Synaptic Vesicles

A

Located in the synaptic knob

Contain neurotransmitters, which fuse with the presynaptic membrane to release neurotransmitters into the synaptic cleft

225
Q

Neurotransmitters

A

Chemicals that allow an action potential to be transferred across a synapse

When NTs are released from the synaptic vesicles into the synaptic cleft, they bind to specific receptors on the postsynaptic membrane

226
Q

Postsynaptic membrane

A

Membrane of the postsynaptic neurone or effector cell

Receptors on postsynaptic membrane have a complementary shape to NTs released from the synaptic knob

When NTs bind to their receptors, the action potential continues

Contains only receptors, ensuring the nerve impulse moves in only one direction

227
Q

Excitatory Neurotransmitters

A

Generate an action potential in the postsynaptic cell

When the NTs bind to the receptors on the postsynaptic membrane, the membrane is depolarised

228
Q

Inhibitory Neurotransmitters

A

Prevent an action potential from being generated in the postsynaptic cell

When the NTs bind to the receptors on the postsynaptic membrane, the membrane is hyperpolarised

229
Q

Example of excitatory neurotransmission

A

Acetylcholine binds to receptors on the postsynaptic membrane in the CNS, establishing an action potential

230
Q

Example of inhibitory neurotransmission

A

Acetylcholine binds to receptors on the postsynaptic membrane in the heart, K+ ions channels are opened in the membrane

This prevents an action potential from being established

231
Q

What happens to the postsynaptic membrane after an inhibitory NT binds to the receptors?

A

Hyperpolarisation

232
Q

Neuromuscular Junction

A

Synapse between a motor neurone and a muscle cell

233
Q

What happens once an action potential arrives at the synaptic knob at the end of a motor neurone in a neuromuscular junction?

A

The action potential depolarises the membrane of the synaptic knob, causing voltage-gated Ca 2+ ion channels to open

Ca 2+ ions dissue into the synaptic knob

234
Q

Effect of increased Ca 2+ ion concentration inside the synaptic knob

A

Synaptic vesicles move and fuse with presynaptic membrane

Acetylcholine is released into the synaptic cleft via exocytosis

235
Q

What receptors does acetylcholine bind to on the postsynaptic membrane?

A

Nicotinic Cholinergic Receptors

236
Q

Effect of binding of acetylcholine in a neuromuscular junction

A

Binding of the neurotransmitter opens sodium ion channels in the postsynaptic muscle cell

237
Q

Na+ ions diffuse into the cell

A

The membrane becomes depolarised

If the potential difference reaches the threshold value, an action potential is generated and flows along the motor cell

238
Q

What is a neuromuscular junction between?

A

Motor neurone + muscle cell

239
Q

Cholinergic Synapses

A

Synapses which use acetylcholine as a neurotransmitter

240
Q

What are cholinergic synapses between?

A

2 neurones

241
Q

Type of response in a cholinergic synapse vs neuromuscular junction

A

Cholinergic synapse - Inhibitory or excitatory

Neuromuscular junvtion - always excitatory

242
Q

Depolarisation of the post synaptic membrane of the cholinergic synapse vs neuromuscular junction

A

Cholinergic synapse - action potential

Neuromuscular junction - muscle contraction

243
Q

Acetylcholinesterase

A

Enzyme that breaks down acetylcholine after it has bound to receptors on the postsynaptic membrane

244
Q

Where is acetylcholinerase located in cholinergic synapses vs neuromuscular junction?

A

Cholinergic synapse - synaptic cleft

Neuromuscular junction - clefts postsynaptic membrane

245
Q

3 ways in which excitatory drugs work

A

Mimic neurotransmitters

Inhibit enzymes

Release of neurotransmitters

246
Q

How do excitatory drugs mimic neurotransmitters?

A

Drugs with a similar shape to the neurotransmitter can bind to receptors on the postsynaptic membrane to produce an action potential

Agonists

247
Q

Example of an excitatory agonist drug

A

Nictotine can bind to cholinergic receptors in the brain to mimic acetylcholine

248
Q

How can excitatory drugs inhibit enzymes?

A

Bind to enzymes to prevent the breakdown of a neurotransmitter

The NT would continue to generate an action potential in the postsynaptic membrane

249
Q

Example of an excitatory drug inhibiting enzymes

A

Nerve gas inhibits acetylcholinesterase and stops the breakdown of acetylcholine

This causes loss of muscle control

250
Q

How do excitatory drugs release NTs?

A

Drugs can cause presynaptic neurones to release NTs

More NTs will activate more receptors and an action potential is more likely to be created

251
Q

2 ways in which inhibitory drugs work

A

Block Calcium ion channels

Block receptors

252
Q

Inhibitory drugs blocking calcium ion channels

A

Drugs can block calcium ion channels in the presynaptic membrane

Blocking calcium ion channels would prevent the release of neurotransmitters from the presynaptic neurone

253
Q

Inhibitory drugs blocking receptors

A

Drugs can block receptors on the postsynaptic membrane

If the receptors are blocked, NTs cannot bind and an action potential is not generated in the postsynaptic neurone

Antagonists

254
Q

Example of an antagonist inhibitory drug

A

Curare blocks nicotinic cholinergic receptors causing muscle paralysis

255
Q

Effect of an inhibitory NT on the postsynaptic cell

A

It preventtts an action potential from being generated in the postsynaptic cell

256
Q

Effect of acetylcholinesterase

A

Breaks down acetylcholine so that is can be reabsorbed by the presynaptic neurone and reused to synthesise more acetylcholine

257
Q

What is the result of depolarisation of the postsyanaptic membrane at a cholinergic synapse?

A

Generation of an action potential

258
Q

What attaches skeletal muscles to bones?

A

Tendons

259
Q

What do skeletal muscles consist of?

A

Many bundles of muscle fibres

260
Q

What are muscle fibres?

A

Long, specialised cells

261
Q

Name of the membrane of muscle fibres

A

Sarcolemma

262
Q

Sarcolemma

A

The membrane of the muscle fibres

Folds inwards to the sarcoplasm at certain points

The inwards folds are called Transverse (T) Tubules

263
Q

Importance of T tubules

A

Initiating muscle contraction

264
Q

Calcium ion store in the sarcoplasm

A

Sarcoplasmic reticulum

265
Q

What do muscke fibres have lots of?

A

Mitochondria and nuclei

266
Q

Myofibrils

A

Cylindrical organelles that run along the length of muscle fibres

Site of muscle contraction

267
Q

What are myofibrils made up of?

A

Multiple units which run end-to-end, called sarcomeres

268
Q

Z-line

A

End of the sarcomere

269
Q

Myofilaments

A

Sarcomeres are made up from 2 types of myofilaments

The 2 filaments slide past each other, causing muscles to contract

270
Q

Protein in thick myofilaments

A

Myosin protein

271
Q

Protein in thin myofilaments

A

Actin protein

272
Q

A-band

A

Overlapping region of thick myosin and thin actin filaments

273
Q

H-Zone

A

Region with only thick myosin filament

274
Q

M-line

A

Middle of the sarcomere where thin actin filaments and thick myosin filaments overlap

275
Q

I-band

A

Region with only thin actin filaments

276
Q

Redox behaviour of aldehydes

A

Oxidised to carboxylic acids

Reduced to primary alcohols

277
Q

Redox behaviour of ketone

A

cannot be oxidised but can be reduced to secondary alcohols

278
Q

Test for an aldehyde

A

Benedicts and Fehlings will turn blue to brick red in the presence of an aldehyde but do nothing with a ketone

Tollens reagent - silver mirror with an aldehyde, stays clear with a ketone

279
Q

What is the carbonyl group (=O) present in?

A

Aldehydes

Ketones

Carboxylic acids

Amides

280
Q

How are carbonyls reduced to alcohols?

A

Hydride reduction - nucelophilic addition-elimination

H- acts as a nucleophile, from sodum borohydride (NaBH4 -)

281
Q

Why can sodium borohydride reduce carbonyls?

A

The alcohol is less reactive

282
Q

Product of the nucleophilic addition of a cyanide ion to a carbonyl

A

Hydroxynitrile

283
Q

Nucleophilic addition of CN

A

Adding CN to a carbonyl results in a hydroxynitrile

You must add acid at the end to put a proton on the oxygen anion

If the reactant is assymetric, you get enantiomers

284
Q

KCN hazards

A

KCN - irritant

Produced HCN when wet - respiratory inhibitor

285
Q

Sliding Filament Theory

A

Explains how mucle contraction is coordinated in myofibrils

286
Q

Stages of sliding filament theory

A

Depolarisation of the sarcolemma

Contraction of the sarcomeres

Muscle contraction

Muscle relaxation

287
Q

When is muscle contraction initiated in sliding filament theory?

A

Muscle contraction is initiated when an action potential arrives at the muscle cells

The action potential depolarises the sarcolemma

288
Q

Effect of the depolarisation of the sarcolemma in sliding filament theory

A

Depolarisation of the sarcolemma causes the myosin and actin filaments to slide over each other

The sliding movement causes the sarcomeres to contract

289
Q

Muscle contraction in sliding filament theory

A

There are multiple sarcomeres along the length of myofibrils

As many sarcomeres contract simultaneously, the muscke fibres contract

Contraction of the muscle fibres causes the whole muscle to contract

290
Q

Muscle relaxation in sliding filament theory

A

After the muscle has contracted, the sarcomeres relax

The filaments slide back over each other and the muscle relaxes

291
Q

What allows sliding filament theory to take place?

A

Globular heads on myosin filaments, which allow myosin and actin filaments to bind together and slide past each other

292
Q

Binding sites on myosin head

A

2 binding sites

One can bind to actin

One can bind to ATP

293
Q

Binding site on actin filaments

A

Actin-myosin binding site, where the actin filament binds to the myosin filament

294
Q

Tropomyosin

A

Protein located on actin filaments

Blocks the actin-myosin binding site when muscle fibres are at rest

When muscle fibres are stimulated, the tropomyosin protein is moved so that myosin heads can bind to the actin-myosin binding site

295
Q

What happens when actin and myosin bind?

A

They can slide past each other to cause muscle contraction

296
Q

How does aerobic respirationmake ATP?

A

Oxidative phosphorylation

297
Q

How does anaerobic respiration make ATP?

A

Glycolysis and lactate fermentation

298
Q

Phosphocreatine

A

A molecule which can supply ATP for muscle contraction

Donates phosphate to ADP to produce ATP

During low periods of muscle activity, ATP can be used to phosphorylate creatine back to phosphocreatine

Anaerobic and no lactate is produced, but phosphocreatine is in short supply

299
Q

What causes actin and myosin filaments to slide over each other?

A

Depolarisation of the sarcolemma

300
Q

Effect of calcium ions binding to a protein attached to tropomyosin

A

Causes the protein to change shape

altering the protein causes tropomyosin to be moved
The actin-myosin binding site is no longer blocked

301
Q

Name of the bond between actin and myosin

A

Actin-myosin cross bridge

302
Q

What happens when Calcum ions activate ATP hydrolase?

A

ATP is split into ADP and inorganic phosphate

303
Q

Use of energy released when calcium ions activate ATP hydrolase

A

Causes the myosin head to bend

The movement of the head causes the actin filament to slide past the myosin filament

The actin filament is pulled by the myosin head because of the actin-myosin cross bridge

304
Q

What happens after the actin filament has slid past the myosin filament?

A

The actin-myosin cross bridge is broken and the actin filament is no longer attached to the myosin head

305
Q

What happens once the actin-myosin cross bridge is broken?

A

The myosin head bends back to its original position after it is released from the actin binding site

The myosin forms a new cross bridge with a binding site further along the actin filament

306
Q

Whay happens if action potentials are no longer stimulating the muscle cells?

A

The release of Ca 2+ ions by the sarcoplasmic reticulum will stop

The Ca 2+ ions are transported back into the SR by active transport

307
Q

Effect of removal of Ca 2+ ions

A

The protein attached to tropomysoin undergoes a conformational change

The protein changes shape, causing tropomyosin to shift so that it is blocking the actin-myosin binding sites

Myosin heads can no longer bind to actin filaments

308
Q

When does the sarcomere lengthen?

A

When actin filaments return to resting

309
Q

Where are slow twitch fibres found?

A

In muscles used for posture such as the back and neck

310
Q

Where are fast twitch fibres found?

A

Mainly in muscles such as the arms and legs

311
Q

Slow twitch fibres adaption to function

A

Adapted for endurance and slow movement over long periods of time

Muscle fibres are long and thin

The muscles fatigue slowly and contract slowly

312
Q

Fast twitch fibres adaption to function

A

Adapted for fast or strong movement over short periods of time

Muscle fibres are short and wide

The muscles fatigue quickly and contract quickly

313
Q

Energy source of slow twitch fibres

A

Energy released through aerobic respiration

314
Q

Energy source for fast twitch fibres

A

Energy released through anaerobic respiration

315
Q

Negative feedback

A

The mechanism that restores systems to the original level

316
Q

Steps in negative feedback

A

Receptors detect change

Effectors counteract change

317
Q

Benefit of multiple negative feedback mechanisms

A

More control

Faster respose

318
Q

How does negative feedback increase body temperature?

A

Shivering

Vasoconstriction

319
Q

How does glucose concentartion affect blood water potential?

A

An increase in blood glucose concentration will decrease the water potential of the blood

320
Q

What are increases in blood lucose levels monitered by?

A

Pancreas

321
Q

Glycogenesis

A

When blood glucose concentration is high, liver cells produce enzymes to convert glucose into glycogen.

The glycogen is then store in liver cells

322
Q

Glycogenolysis

A

When blood glucose concentration is too low, the liver cells produce enzymes that break down the glycogen stored in the cells to glucose

323
Q

Gluconeogenesis

A

When blood glucose concentration is too low, liver cells form glucose from glycerol and amino acids

324
Q

Effect on an increse in blood glucose concentration on the cells in the body

A

Water diffuses out

325
Q

What detects high insulin levels?

A

Beta cells in the pancreas

326
Q

Where are beta cells located?

A

Islets of langerhan

327
Q

How do beta cells respond to high blood glucose concentration?

A

Secreting insulin, which travels in teh blood to the liver and muscle cells

328
Q

What does insulin bind to?

A

Receptors on the muscle cell membranes

329
Q

Effect of insulin binding to muscle cell membranes

A

The muscle cell insert more glucose channel proteins in the cell membrane, causing

The rate of uptake by muscle cells to increase

The rate of respiration in muscle cells to increase

330
Q

How does glycogenesis happen?

A

Insulin binds to receptors on the liver cell membranes

The liver cell produces enzymes that convert glucose to glycogen

331
Q

Where is glycogen stored?

A

Liver Cells cytoplasm

332
Q

Stages in action of insulin to decrease blood glucose levels

A

Detection of high blood glucose levels in beta cells

Secretion of insulin from beta cells

Binding of insulin to muscle and liver cells

Glycogenesis

333
Q

What is low blood glucose concentration detected by?

A

Alpha cells in islets of langerhan

334
Q

How do alpha cells respond to low blood glucose concentartion?

A

Secreting glucagon into the blood, which travels in the blood to liver cells

335
Q

How does glycogenolysis happen?

A

Glucagon binds to receptors on the liver cell membranes

The liver cells produce enzymes that convert glycogen to glucose

336
Q

How does gluconeogenesis happen?

A

Binding of glucagon to liver cells also causes the release of enzymes that form glucose from glycerol and amino acids

337
Q

Adrenaline response to low glucose levels

A

Secretion of adrenaline from adrenal gland

Adrenaline binds to receptors on liver cell membrane
Activates glycogenolysis
Inhibits glycogenesis

Promotes secretion of glucagon from pancreas and inhibits secretion of insulin

338
Q

When insulin binds to receptors on the muscle cells, what 2 processes take place?

A

Rate of glucose uptake increases

Rate of respiration increases

339
Q

What does adrenaline bind to?

A

Receptors on liver cell membrane

340
Q

2 hormones responsible for restoring normal levels of blood glucose if the concentration is too low

A

Glucagon

Adrenaline

341
Q

What enzyme does the binding of adrenaline or glucagon activate?

A

Adenylate Cyclase

342
Q

Role of adenylate cyclase

A

ATP –> cAMP

343
Q

Role of cAMP

A

Activates protein kinase A

344
Q

Role of protein kinase A

A

Triggers a cascade of reactions that result in glycogenolysis

345
Q

Prrrimary messengers

A

Do not enter a cell

Exert an action on the cell membrane by binding to receptors and triggering a change within a cell

This change can be the actovation of another molecule or it may initiate a reaction

346
Q

Secondary Messengers

A

Initiate and coordinate responses that take place inside a cell

Usually activated by the binding of a primary messenger to a cell surface receptor

347
Q

cAMP - stages

A

Adrenaline or glucagon bind to receptors on the cell membranes of liver cells

This activates adenylate cyclase, which converts ATP –> cAMP

cAMP activates protein kinase A, which triggers a cascade of reactions that result in glycogenolysis

348
Q

Diabetes Mellitus

A

A chronic health condition where sufferers cannot properly control their blood glucose concentration.

Type I diabetes sufferers cannot produce insulin

349
Q

Cause of Type I diabetes

A

Beta cells in the pancreas are attacked by the immune system

The beta cells become damaged and can no longer produce insulin

350
Q

Hyperglycaemia

A

Eating causes the blood glucose concentration to increase

People with type I diabetes cannot produce insulin to counteract the increased levels of glucose so the blood glucose level remains high

Hyperglycaemia can lead to death if it is not treated

351
Q

Type I diabetes treatment

A

Insulin therapy

Too much insulin can cause a fall in glucose levels called hypoglycaemia so insulin must be carefully monitered

352
Q

Type II diabetes

A

Either don’t produce enough insulin or don’t respond to insulin

Usually develops in later life

353
Q

Causes of Type II diabetes

A

Correlated with obesity, lack of exercise, age and family history

Develops when beta cells in the pancreas no longer produce enough insulin or when the muscle nd liver cells stop responding to insulin

354
Q

Type II diabetes - Treatment

A

Eating a healthy diet and exercising

Medication to lower glucose levels, or sometimes insulin injections

355
Q

Health advice for type II diabetes

A

A balanced diet that is low in salt, fat and sugar

Regular exercise

356
Q

WHO recommendation for the food industry to help combat the rise in obesity and diabetes

A

Reducing levels of sugar, saturated fats and salts in processed food products

Developing healthy, alternative products

Having clear and simple labelling on food items showing nutritional contents

Promoting and market healthier foods, especially to children

357
Q

What will happen to the blue colour of Benedicts reagent as glucose concentration increases?

A

Become darker

358
Q

Where does osmoregulation take place?

A

Kidneys

The kidneys absorb more or less water accrding to the water potential

359
Q

Osmoregulation

A

The control of the water potential in the blood

360
Q

Blood water potential is too high

A

More water must be lost by excretion to return the water potential to normal

The blood reabsorbs less water from the kidneys

The urine is more dilute and water potential in the blood decreases

361
Q

Low blood water potential

A

Less water must be lost by excretion to retutn the water potential to normal

The blood reabsorbs more water from the kidneys

The urine is more concetrated and water potential in the blood increases

362
Q

Nephron

A

Functional unit of the kidney and each kidney has several million

The structure of the nephron is important for osmoregulation

363
Q

Bowmans capsule

A

Beginning of the tubules that make up the nephron

The capsule surrounds a network of capillaries, know as the glomerulus

364
Q

Role of the Bowmans capsule

A

The first step of filtration of the blood to form urine takes place in the Bowman’s capsule.

This produces glomerular filtrate

365
Q

How does blood flow in and out of the glomerulus?

A

In - Afferent arteriole

Out - Efferent arteriole

366
Q

Afferent vs efferent arteriole

A

The afferent arteriole is much wider than the efferent arteriole. This means that blood pressure in the capillaries is very high

367
Q

PCT - Proximal Convoluted Tube

A

Site of selective reabsorption

After the golemrular filtrate has been produced in the Bowman’s capsule, glucose and water are reabsorbed into the bloodstream through the PCT

368
Q

What happens once the glomerular filtrate has been produced in the Bowman’s capsule?

A

Glucose and water are reabsorbed into the bloodstream through the PCT

369
Q

Loop of Henle

A

Produces a low water potential in the medulla of the kidney

The loop of Henle consists of an ascending limb and a descending limb

370
Q

Ascending vs descending limb in the medulla of the kidney

A

Ascending lumb - impermeable to water

Descending limb - permeable to water

371
Q

How is water reabsorbed into the blood from the kidney?

A

Through the collecting duct

372
Q

What does the amount of water absorbed by the blood from the kidney depend on?

A

The water potential of the blood

Low - more water is reabsorbed

High - less water is reabsorbed

373
Q

Where does the formation of glomerular filttrate take place?

A

Bowman’s Capsule

374
Q

Stages of the formation of glomerular filtrate

A

Pressure filtration

Capillary endothelium

Basement membrane

Podocytes

Glomerular filtrate

375
Q

Pressure filtration in the formation of glomerular filtrate

A

The branch of capillary that enters the glomerulus is much wider than the branch that exits the glomerulus

This creates a high blood pressure in the glomerulus

The high blood pressure causes the fluid and its solutes in the blood to be forced out of the capillary

376
Q

Capillary endothelium in the formation of glomerular filtrate

A

The fluid flows through the pores in the capillary endothelium

377
Q

Basement membrane in the formation of glomerular filtrate

A

The smaller molecules filter through slit pores in the basement membrane. This is a mesh of collagen fibres and glycoprotein

Most proteins and all blood cells are too big to pass through the slit pores

378
Q

Podocytes in the formation of glomerular filtrate

A

The substances finally pass between the epithelial cells of the Bowman’s capsule

The epithelial cells, called podocytes, have finger-like projections that the substances can flow between

379
Q

Glomerular filtrate

A

The fluid that has filtered from the capillaries to the Bowman’s capsule

380
Q

What does the glomerular filtrate contain?

A

Water

Amino acids

Urea

Glucose

Inorganic ions

381
Q

Sodium-potassium pumps in PCT

A

Na+ ions are actively transported out of the PCT epithelial cells and into the blood by sodium-potassium pumps

K+ ions are also transported into the epithelium

382
Q

Co-transporter proteins in PCT

A

Active transport of Na+ ions causes the concentration of Na+ ions inside the epithelial cells to decrease

Na+ ions in the filtrate diffuse into the epithelial cells through co-transporter proteins

Co-transporter proteins allow glucose and amino acids to be transorted into the epithelial cells along with Na+ ions

383
Q

Rebsorption of glucose and amino acids in PCT

A

As glucose and amino acids are co-transpoerted into teh PCT epithelial cells, their concentration increases inside the cells

Glucose and amino acids diffuse down the concetration gradient into the blood

Blood pressure is relatively high so that substances in the blood are carried away quickly. This maintains a steep concentration gradient

384
Q

Reabsorption of water in PCT

A

The movement of Na+ ions, glucose and amino acids into the bloodstream causes the water potential in the blood to decrease and increase in the PCT

Water in the PCT diffuses into the blood through osmosis

Any substances that are not reabsorbed are excreted as waste

385
Q

Steps in movement of glomerular filtrate substances from PCT –> blood (selective reabsorption)

A

Sodium-potassium pumps

Co-transporter proteins

Reabsorption of glucose and amino acids

Reabsorption of water

386
Q

Role of Loop of henle

A

Creates a region of low water potential and high sodium concentration in the medulla of the kidney

This allows water to be reabsorbed in the collecting duct

387
Q

Role of the top of the ascending limb in the loop of Helne

A

Na+ ions are actively transported out of the top of the ascending limb in the surrounding tissue fluid in the medulla

This causes the solute concentration of the medulla to increase and the water potential to decrease

The ascending limb in impermeable to water. This means water inside the tubule cannot diffuse out

388
Q

Role of the bottom of the ascending limb in the loop of henle

A

Na+ ions diffuse out of the bottom of the ascending limb into the medulla

This further increases the solute concentration of medulla

389
Q

Role of the descending limb in the Loop of Henle

A

The descending limb is permeable to water.
This means that water inside the tubule can diffuse out becaise there is a low water potential in the medulla

The water is reabsorbed by the bloodstream

390
Q

Overall effect of the ascending and descending limb in the Loop of Henle

A

Create a high solute concentration and low water potential in the tissue fluid surronding the collecting duct

This causes water inside the collecting duct to diffuse into the surrounding tissue fluid by osmosis

The water is then reabsorbed into the bloodstream

391
Q

What does the volume of water reabsorbed by the bloodstream depend on?

A

The permeability of the collecting duct

392
Q

How does the permeability of the collecting duct vary?

A

According to the water potential of the blood

High water potential = collecting duct is less permeable to water and less water in absorbed in the blood

393
Q

Antidiuretic Hormone (ADH) - role

A

ADH controls osmoregulation

ADH influences the permeability of the distal convoluted tubule and collecting duct.

This controls how much water is reabsorbed from he kidney into the blood

394
Q

What monitors blood water potential?

A

Osmoreceptors in the hypothalamus

395
Q

How do osmoreceptors in the hypothalamus monitor blood water potential?

A

If the water potential increases, water diffuses into the osmoreceptor cells and the cell swells

If the water potential decreases, water diffuses out of the osmoreceptor cells and the cells shrink

396
Q

Role of posterior pituitary gland

A

Detects when osmoreceptors shrink and releases ADH into the blood

397
Q

ADH

A

A hormone that binds to receptors on the cell membrane of epithelial cells of the distal convoluted tube and the collecting duct

398
Q

What happens when ADH binds?

A

Vesicles containing aquaporins fuse with the cell membrane

399
Q

Aquaporins

A

Protein channels for water

Increase the permeability of the DCT and collecting duct

This means that more water is reabsorbed into the blood by osmosis

400
Q

What happens if more ADH is in the bloodstream?

A

More water is reabsorbed from the nephron into the blood

The urine is more concentration

401
Q

Osmorecptor cells

A

The cells in the hypothalamus that respond to water potential in the blood and trigger a response in the posterior pituitary gland

402
Q

Podocytes

A

Epithelial cells of the Bowman’s capsule

403
Q

Through what process is water reabsorbed into the bloodstream in the proximinal convoluted tube?

A

Osmosis

404
Q

Which limb of the Loop of Henle is impermeable to water?

A

The Ascending Limb

Biology (7 decks)

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