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Biology Paper 2 > Topic 6 Homeostasis > Flashcards

Topic 6 Homeostasis Flashcards

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1
Q

What is a stimulus

A

A detectable change in the environment

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2
Q

What are receptors

A

Cells that detect a stimulus

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3
Q

What is an example of a growth factor that controls Tropisms

A

Indoleacetic acid (IAA)

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4
Q

What does IAA do

A

Type of auxin that’s controls cell elongation in shoots and inhibits root growth made at the tip of the roots and shoots and can diffuse to other cells

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5
Q

Why does phototropism improve the survival chance of shoots

A

Light needed for LDR so plants bend towards light this so positive phototropism

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6
Q

Explain how phototropism occurs in the shoots

A
  1. Shoot tip cells produce IAA cashing cell elongation
  2. IAA diffuses to other cells
  3. If there is unilateral light IAA diffuses to words shaded side so that side elongates causing a bend
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7
Q

Explain how phototropism occurs in the roots

A

Roots do not photosynthesis so don’t require light

High conc of IAA inhibits cell elongation causing root cells to elongate on the lighter side so roots bend away from the light

Negative phototropism

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8
Q

Explain how gravitational works in the shoots

A
  1. IAA diffuses from upper side to lower side of shoot
  2. If plant is vertical causes plant to elongate and grow up
  3. I’d plant is horizontal causes shoot to bend up

This is negative gravitropism

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9
Q

How does gravitropism work in the roots

A
  1. IAA moves along to the lower side of roots so that the upper side elongated causing root to bend down to words gravity anchoring the plant in

This is positive gravitropism

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10
Q

What are the 3 neurones that make up the reflex arc

A

Sensory neutone
Relay neurone
Motor neurone

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11
Q

What is taxes

A

Organism moves it’s entire body to words favourable stimulus away from unfavourable

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12
Q

What is kinesis

A

Organism changes speed of movement and the rate it changes direction

Returns to favourable conditions

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13
Q

Where are the pacinican corpuscle found and what does it detect

A

Found mainly in fingers and feet and detects pressure

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14
Q

Explain the structure of the pacinian corpuscle

A

A sensory neurone with a neurone ending with lots of connective tissue with gel between each layer

The membranes of pacinian Corpuscle have stretch mediated sodium channels

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15
Q

Explain how the special channel proteins in the pacinian corpuscle work

A

When the sodium channels have pressure applied to them they stretch and deform allowing the channel to open allowing sodium ions to diffuse in which leads to generator potential

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16
Q

Where are the receptors rods and cones found

A

In the human retina

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17
Q

Give properties of rod cells (5)

A
  1. Rod like In shape
  2. Process images in black and white
  3. Use pigment rhodopsin
  4. Detect light at very low intensity
  5. Brain can’t distinguish between separate sources of light so you have low visual acuity (low clarity)
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18
Q

What is retinal convergence

A

Many rod cells are connected to one sensory neurone

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19
Q

Give the properties of cone cells

A
  1. Cone cells process images in colour
  2. 3 types that contain different types of iodopsin pigment
  3. High visual acuity - can distinguish between separate sources of light
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20
Q

What are the 3 colours of cone cells

A

Red, green and blue

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21
Q

Why can’t we see colour when it’s dark

A

One cone cell connects to a bipolar cell therefore cones can only respond to high light intensity

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22
Q

Where are most of the cone cells located

A

In the fovea where the highest light intensity is

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23
Q

Where are rod cells located

A

Further away from fovea as they don’t need as high light intensity

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24
Q

Where is the SAN located and what is it

A

Sinoatrial node - pacemaker of heart found in right atrium

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25
Q

Where is the AVN located

A

Atrioventricular node - located near boarder of right and left ventricle within atria

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26
Q

Where is the bundle of his

A

Runs through septum

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27
Q

Where are the purkyne fibres

A

In the walls of hr ventricles

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28
Q

Explain the control of heart rate (5)

A
  1. SAN released a wave of depolarisation across the atria causing contractions
  2. AVN released another wave of depolarisation when it first reached it. Non conductive later between atria and ventricles prevents wave of depolarisation travelling down to the ventricles
  3. Bundle of his conducts wave of depolarisation down the septum and purkyne fibres
  4. There is a short delay before the walls of the atria contract whilst AVN transmits second wave of depolarisation
  5. Allows enough time for atria to pump all the blood into ventricles, cells repolarise and cardiac muscle relaxes
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29
Q

What controls your heart rate

A

Medulla oblongata via the autonomic nervous system

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30
Q

What are the 2 parts of the nervous system that are linked to control of heart rate

A
  1. Sympathetic nervous system
  2. Parasympathetic nervous system
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31
Q

What happens if more nerve impulses are sent down the sympathetic nervous system

A

SAN release waves of depolarisation more frequently causing increase in Heart rate

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32
Q

What happens if more nerve impulses are sent down the parasympathetic pathway

A

Causes SAN to release waves of depolarisation less frequently causing decrease in heart rate

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33
Q

What are the 2 stimuli that can change the heart rate

A

PH & blood pressure

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34
Q

What detects changes in PH

A

Chemoreceptors

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35
Q

What detects change in blood pressure

A

Pressure receptors/ baroreceptors

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36
Q

Where are the 2 receptors found

A

Aorta and carotid artery

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37
Q

How does your heart rate respond to a change in PH

A

PH in the blood may de caress during times of high respiratory rate due to production of co2 or lactic acid

Excess acid mist be removed to prevent enzymes denaturing

This is done by increasing heart rate so co2 can diffuse into alveoli more rapidly

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38
Q

How does your heart rate respond to blood pressure high & low

A

If too high can cause damage to walls of arteries to counteract this more impulses via parasympathetic nervous system to decrease heart rate

If too low insufficient supply of oxygenated blood for repairing cells so more impulses along sympathetic nervous system to increase heart rate

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39
Q

Give the structure of a myelinated neurone (4)

A

Cell body - contains all organelles of a typical plant cell

Dendrites - branched that carry action potentials it surrounding cells

Axon - conductive long fibre carries nervous impulses along motor neurone

Schwann cells - wrap around axon to form myelin sheath which is a lipid so charged ions can’t pass through the gaps between the sheaths are called nodes of ranvier

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40
Q

What is a resting potential

A

When a neurone is not conducting an impulse there is a difference between electrical charge inside and outside neurone

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41
Q

Explain the resting potential of axons

A

More positive sodium ions an potassium outside compared to inside so inside of neurone is more negative

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42
Q

How are resting potentials maintained

A
  • sodium potassium pump involves active transport and ATP

2 K+ ions pumped into axon and 3 Na+ ions move out

Creates an electrochemical gradient causing K+ to diffuse out and Na+ to diffuse in

Membrane is more permeable to K+ ions as there is more K+ channels this results in more + ions outside cell compared to inside

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43
Q

What is an action potential

A

When neurones voltage increases beyond a set pint from resting potential generating a nervous impulse

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44
Q

Explain an action potential (6)

A
  1. When axon is as resting potential the sodium ion channels are closed by the potsssium channels are always open
  2. A stimulus then opens the sodium channels causing an influx of sodium to go into the axon causing potassium to leave this causes depolarisation which increases the voltage to above the threshold value
  3. Once the voltage has reached above threshold value you will have an action potential
  4. When action po trial teachers 35-40mv this causes the voltage gated sodium ion channels to close so no more sodium enters but potassium ions still move out
  5. There is a decrease in voltage (repolarisation) causes more potassium ion channels or open causing more to leave causing the voltage to decrease back to the resting state
  6. But overshoots as the potassium channel still open this is called refractory period
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45
Q

What is the all or nothing principle

A

Stimulus must be large enough o go past the minimum threshold value which is -55 volts in order to create action potential

As long as it does Reach this threshold will always peak at same point 35-40 volts but larger stimuli will have more frequent action potentials

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46
Q

Explain why the refractory period is important (3)

A
  1. Ensures discreet action potentials produced can’t be generated immediately after one another
  2. Ensures action potential travels in one direction
  3. Limited number of impulses to prevent over reaction
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47
Q

What are the 3 factors that affect the speed of conduction

A
  1. Myelination & saltatory conduction
    2 axon diameter
  2. Temperature
48
Q

What is myelination

A

Action potential jumped from node to node (saltatory conduction) means action potentials travel faster long axon

49
Q

How does the axon diameter affect speed of conductance

A

Wider diameter increases speed less leakage of ions

50
Q

How does temperature affect speed of conductance

A
  1. Ions diffuse faster (more kinetic energy)
  2. Enzymes involved work faster in higher temps more ATP for active transport
51
Q

What are synapses

A

The gaps between the neurones end of the axon and dendrite of another

52
Q

Explain the function of a synapse (6)

A
  1. Action potential arrives at synaptic knob opening the Ca2+ channels and calcium diffuses into synaptic knob
  2. Vesicles containing neurotransmitters move to words and fuse with presynaptic membrane. Neurotransmitter is released to the synaptic cleft (gap)
  3. Neurotransmitter diffuses down conc gradient across synaptic cleft to post-synaptic membrane
    Neurotransmitter then bonds to complementary shape to receptors in surface of post-synaptic membrane

4.sodium ion channels in post-synaptic membrane open and sodium diffuse in if enough diffuse in to exceed threshold value post-synaptic neurone becomes depolarised

  1. Neurotransmitter is degraded and released from receptor Na+ channels close and post- synaptic neurone re restablishes resting potential
  2. Neurotransmitter transported back into presynaptic neurone
53
Q

How is the function of the synapse unidirectional

A
  1. Vesicles containing neurotransmitters are only in pre synaptic neurone
  2. Conc gradient diffusion must occur from pre to post neurone
  3. Receptors are only on membrane of post synaptic neurone
54
Q

What is the name of the neurotransmitter for the cholinergic synapse

A

Acetylcholine

55
Q

What is the enzyme that breaks down acetylcholine into choline and acetate

A

Acetylcholineesterase

56
Q

What is summation

A

Rapid build up of neurotransmitters in the synapse to generate an action potential bye either spacial summation or temporal summation

57
Q

What is spatial summation

A

Many different neurones collectively trigger a new action potential by combining with neurotransmitter they release to exceed threshold value

58
Q

What is temporal summation

A

One neurone released neurotransmitter repeatedly over short period of time to add up to enough to exceed threshold value

59
Q

What are inhibitory synapses

A

Causes chloride ions to move into the post-synaptic neurone and potassium ions to move out

Makes membrane hyper polarise and so action potential unlikely to be reached

60
Q

What is a neuromuscular junction

A

Synapse between motor neurone and a muscle

61
Q

Give one similarity and 3 differences between neuromuscular junction and cholinergic synapse

A

Similarity
Both unidirectional

Differences

Neuromuscular- excitatory
Cholinergic - could be excitatory or inhibitory

Neuromuscular - connects motor neurone to muscle
Cholinergic - connects 2 neurones

Neuromuscular - end point for action potentials
Cholinergic - a new action potential generated in next neurone

62
Q

What is the sarcoplasm

A

Myofibrils are made up of fused cells that share nuclei and cytoplasm

63
Q

What are the sarcomere

A

Muscle fibres are made up of millions of myofibrils which collectively bring about the force to cause movement

64
Q

What are the 2 key types of proteins that make up myofibrils

A

Myosin and actin

65
Q

What does the A band of a muscle represent

A

The length of myosin which should never change

66
Q

What does the H zone represent

A

The length of myosin that isn’t overlapping with actin

This will change when the muscle contracts so H zone will shorten

67
Q

What does the I band represent

A

Actin by itself not overlapping with myosin

When muscle contracts it decreases as myosin is overlapping with actin

68
Q

What do the Z lines represent

A

The start and end of the sarcomere

These get closer together when muscle contracts

69
Q

What is the sliding filament theory

A
  1. When action potential reaches a muscle stimulates a response
  2. Calcium ions enter and cause the protein tropomyosin to move and uncover the binding sites on actin
  3. Whilst ADP attached to the myosin head the myosin heads to the actin form a cross-bridge
  4. The angle created in this cross bridge creates tension and as a result and actin filament is pulled and slides along the myosin in doing so ADP released
  5. An ATP molecule binds to myosin head and causes it to change shape slightly as a result detaches from actin
  6. Within sarcoplasm enzyme ATPase which is activated by calcium ions to hydrolyse the ATP and release enough energy for the myosin heads to return to original position
  7. Entire process repeats continuously
70
Q

What is phosphorcreatine

A

A chemical stored in muscles assists sliding filament theory by providing phosphate to regenerate ATP from ADP

71
Q

Give the structure location and general properties of slow twitch muscles

A

Confession large store of myoglobin and rich blood supply lots of mitochondria

Located in calf

Contract slower
Respire aerobically
Muscles adapted for endurance work

72
Q

Give the structure, location and general properties of fast twitch fibres

A

Thicker contain more myosin filaments
Store of glycogen
I’m over in anaerobic respiration

Found in biceps

Contract faster
Adapted for intense exercise

73
Q

What is homeostasis

A

Physiological control systems that maintain internal environment within restricted limits

74
Q

What are the 2 main things that are important to maintain

A

Stable core temperature

Stable blood ph

75
Q

What is negative feedback

A

If there is any deviation from the normal values are restored to their original level

76
Q

How can your blood glucose concentration increase

A

Ingestion of food or drink containing carbohydrates

77
Q

How can your blood glucose concentration decrease

A

Following exercise or if you haven’t eaten

78
Q

What it the role of the pancreas in blood glucose concentration

A

Detects change in the blood glucose levels.

Islets of langerhans cells release insulin and glucagon to bring blood glucose levels back to normal

79
Q

What is the role of insulin in the blood glucose concentration

A

Insulin is released when blood glucose levels are too high causes a decrease in blood glucose levels

80
Q

What is the role of glucagon in blood glucose concentration

A

Released when blood glucose levels are too low

81
Q

What is the role of Adrenalin in blood glucose concentration

A

Released by adrenal glands when body anticipates danger results in more glucose being released from hydrolysis of glycogen in the liver

82
Q

Explain what happens if your blood glucose level increases

A
  1. Change is detected by beta cells in the islets of langerhan in the pancreas
  2. Beta cells release insulin
  3. Liver cells become more permeable to glucose and enzymes are activated to divert glucose to glycogen
  4. Glucose removed from blood and stored as glycogen in cells
83
Q

Explain what happens if your blood glucose levels decrease

A
  1. Change is detected by ALPHA cells in islets of langerhan
  2. Alpha cells release glucagon and adrenal gland releases adrenaline
  3. Second messenger model occurs to activate enzymes and hydrolyse glycogen
  4. Glycogen is hydrolysed to glucose and more glucose released back into blood
84
Q

How does insulin decrease blood glucose (3)

A
  1. Attaching to receptors on surface of target cells changing tertiary structure of channel protein so more glucose can be absorbed by facilitated diffusion
  2. More protein carrier incorporated into cell membrane so more glucose absorbed from blood into cells
  3. Activating enzymes in the conversion of glucose to glycogen
85
Q

How does glucagon increase blood glucose (3)

A
  1. Attaching receptors on surface of target cells (liver cells)
  2. When glucagon binds causes proteins to be activated into arent late Cyclase and convert ATP into cyclic AMP (cAMP) this then activated enzyme protein kinase which hydrolysed glycogen into glucose
  3. Activated enzymes involved in conversion of glycerol and amino acids into glucose
86
Q

What is the 2nd messenger model

A
  1. Glucagon bings to glucagon receptor
  2. Once bound causes change in shape to enzyme add to cyclase which activated it
  3. Activated Adenyl cyclase enzyme converts ATP to cyclic AMP (cAMP)
87
Q

How does adrenaline increase blood glucose (2)

A
  1. Adrenaline attached to receptors on target cells
  2. CAMP activated enzyme that hydrolysed glycogen into glucose
88
Q

What is glycogenesis

A

Converting glucose into glycogen occurs in the liver and catalysed by enzymes there

89
Q

What is glycogenolysis

A

Hydrolysis of glycogen to glucose occurs in liver due to secondary messenger model

90
Q

What is gluconeogenisis

A

Creating new glucose from other molecules such as amino acids and glycerol in the liver

91
Q

What is type 1 diabetes what is the treatment

A

Where your unable to produce insulin could be result of autoimmune disease

Treatment is insulin injections

92
Q

What is type 2 diabetes how is it controlled

A

When receptors on target cells lose responsiveness to insulin usually develops due to poor diet

Is controlled by regulating intake of carbohydrates and increased exercise

93
Q

What is osmoregulation

A

Controlling water potential of the blood

94
Q

What happens if blood has too low of a water potential

A

Becomes hypertonic

Too much water leaves cell and moves into blood by osmosis cells shrivel

95
Q

What happens if the blood has too high a water potential

A

Hypotonic

Too much water moves from blood into cell causing cell to burst (lysis)

96
Q

What causes hypertonic blood (shrivelled)

A
  • too much sweating
  • not drinking enough water
  • lots of ions in diet e.g salt
97
Q

What is the corrective method for hypertonic blood

A

More water reabsorbed by osmosis into blood from tubules of the nephrons

Urine is more concentrated as less water is lost in urine

98
Q

What happens if someone has hypotonic blood

A
  • drinking too much water
  • not enough salt in diet
99
Q

What is the corrective mechanism for hypotonic blood

A

Less water reabsorbed by osmosis into blood from tubules of the nephron

Urine is more diluted as more water lost in urine

100
Q

Where does osmoregulation occur

A

Within nephrons in kidney

101
Q

What are the nephrons

A

Long tubules surrounded by capillaries and there are 1 million per kidney

102
Q

What is the purpose of the nephrons

A

Blood filtered here to remove waste and selectively reabsorb useful substances back into the blood

103
Q

What is the glomerulus

A

Filters small solutes from the blood

104
Q

What is the PcT

A

Proximal convoluted tubule - reabsorbs ions, water and nutrients removed toxins

105
Q

What is the descending loop of Henle

A

Aquaporins allow water to pass from filtrate into interstitial fluid

106
Q

What is the ascending loop of henle

A

Reabsorbs sodium and chlorine ions from filtrate into the interstitial fluid

107
Q

What is the distal tubule

A

Selectively secretes and absorbs different ions maintain blood ph

108
Q

What is the collecting duct

A

Reabsorbs solutes and water from filtrate

109
Q

Explain filtration and reabsorption in the kidneys

A
  1. Ultrafiltration occurs in glomerulus due to high hydrostatic pressure
    Water and small molecules forced out of capillaries and into renal capsule
  2. Selective reabsorption occurs in the proximal consulates tubule
  3. Loop of henle maintains sodium ion gradient so water can be reabsorbed into blood
  4. Water moves out of distal consulates tubule and collecting duct returns back to blood
  5. Collecting duct carries remains liquid (urine) to the ureter
110
Q

What is the hypothalamus

A

Changes in the water potential of the blood detected by osmoreceptors

111
Q

What happens if the water potential of blood is too low

A

Water leaves the osmoreceptors by osmosis and shrivel stimulating the hypothalamus to produce more hormone ADH

112
Q

What happens if water potential of blood is too high

A

Water enters the osmoreceptors by osmosis and stimulated hypothalamus to produce less ADH

113
Q

Where is ADH produced

A

Hypothalamus

114
Q

Where does ADH move to

A

Posterior pituitary

115
Q

What does ADH stand for

A

Antidiuretic hormone

116
Q

What does ADH do

A

Causes increase in permeability of walls of collecting ducts and distal convoluted tubule

More water leaves nephron and reabsorbed into blood so urine more concentrated

Biology Paper 2 (4 decks)

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