3.6 Organisms respond to changes in their internal and external environments Flashcards
1
Q
How are reflex arcs protective
A
Kept as short as possible (3 neurones & 2 synapses)
Brain is bypassed so no thinking required
Innate not learnt
e.g. escape predators, prevent damage, homeostasis
2
Q
Reflex arc
A
Stimulus - Receptor -Sensory neurone - Rela neurone - CNS - Motor neurone - Effector
(synapses between neurones)
3
Q
Taxes definition
A
A directional response to a stimulus
4
Q
Kinesis definition
A
A response that involves movement in random directions
5
Q
Structure of a Pacinian corpuscle
A
- Lamellae tissues surrounds sensory neurone ending
- Sensory neurone axon surrounded by myelin sheath
- Sodium ion stretch mediated channel proteins in membrane
6
Q
How does Pacinian corpuscle work
A
- Pressure causes membrane / lamellae to become deformed
- Sodium ion channels in membrane open and sodium ions move in
- The greater the pressure the more channels open / sodium ions enter.
7
Q
Cone cells
A
- High visual acuity
- Each cone cell is connected to a single neurone
- Cone cells send separate impulses to brain
8
Q
Rod cells
A
- High visual sensitivity
- 3 rod cells connected to a single neurone
- Enough transmitter to overcome threshold / spatial summation to overcome threshold
9
Q
Optical pigment in cone cell
A
Iodopsin
10
Q
Optical pigment in rod cell
A
Rhodopsin
11
Q
Role of SAN (sinoatrial node)
A
Initiates a wave of depolarisation, causing the atria to contract
12
Q
Role of AVN (Atrioventricular node)
A
Is stimulated and passes along stimulation to Bundle of His
13
Q
Role of bundle of His
A
Splits into two fibres called Purkyne fibres which carry the wave of excitation along them
14
Q
Role of Purkyne fibres
A
Spread around the ventricles and initiate the depolarisation of the ventricles, causing them to contract
15
Q
Cardiac cycle (neurone)
A
- Sinoatrial node sends out wave of excitation
- Atria contract
- Atrioventricular node sends out wave of excitation
- Along bundle of His and Purkyne fibres
- Ventricles contract
16
Q
Why is it important for there to be a delay before the AVN sends out a wave of excitation
A
Ensures atria have had enough time to empty their blood into the ventricles
17
Q
What is meant by the autonomic nervous system
A
Unconscious / involuntary processes
18
Q
Where are chemoreceptors and baroreceptors found in the heart
A
Aorta
19
Q
Role of chemoreceptor
A
Detect changes in pH of blood
20
Q
Myelinated motor neurone structure
A
Dendrites
Nucleus
Axon
Schwann cells
Nodes or Ranvier
Axon membrane
21
Q
How is a resting potential maintained
A
- Higher concentration of sodium ions outside neurone membrane AND higher concentration of potassium ions inside neurone membrane
- Membrane is more permeable to potassium ions
- Sodium ions actively transported out and potassium ions in
22
Q
Explain why the transmission of impulses is faster along a myelinated axon than a non-myelinated axon [3]
A
- Myelinated provides electrical insulation
- In myelinated saltatory condition
- In non-myelinated depolarisation occurs across whole length of axon
23
Q
What is saltatory conduction
A
When action potentials jump from one node to the next
24
Q
Generation of an action potential
A
- Stimulation and excitation of neurone
- Sodium ion channels open
- sodium ions diffuse into axon down electrochemical gradient
- Threshold of -55mV reached, opening even more sodium ion channels
- At +40mV repolarisation
- Sodium ion channels close, potassium ion channels open
- Potassium ions diffuse out of neurone down concentration gradient restoring resting potential
- Hyperpolarising - K+ channels close slowly so inside becomes more negative
- Sodium-Potassium pump restores potential difference to -70mV
25
What causes the refractory period
Potassium ion channels take a while too close, so it takes a while
26
All or nothing principle
Either an action potential will be generated or it wont, no intermediate
27
Factors affecting speed of conductance
Temperature - increased rate of diffusion
Axon diameter - less resistance to ion flow
Myelination - allows saltatory conduction
28
Cholinergic synapse 6 marker
1. Calcium ion channels open
2. Calcium ions diffuse into pre synaptic membrane
3. Causes fusion of synaptic vesicles with presynaptic membrane
4. Neurotransmitter released into synaptic cleft
5. Neurotransmitter diffuses across synaptic cleft
6. Neurotransmitter attaches to receptors on post synaptic membrane
7. Stimulates opening of sodium ion channels
8. Sodium ions flow into postsynaptic membrane
9. Acetylcholine is broken down by acetylcholinerase and the products return to the presynaptic neurone
29
What is a neuromuscular junction
A neuromuscular junction is where a motor neurone meets a skeletal muscle fibre.
Neuromuscular junctions are distributed along the muscle's length.
Very similar to a synaptic cleft
30
Neuromuscular junction vs cholinergic synapse
Neuromuscular
- Only excitatory neurotransmitters
- Ends at the neuromuscular junction, where the impulse ends and a contraction occurs
- Many receptors on post synaptic membrane
Cholinergic
- Excitatory and inhibitory neurones
- Ends at another neurone, where the impulse continues
- Less receptors on post synaptic membrane
31
How do muscles act (1)
In antagonistic pairs against and incompressible skeleton
32
Gross skeletal muscle structure
Sarcolemma - cell membrane
Sarcoplasm - cytoplasm
Sarcoplasmic reticulum - ER
Many shared nuclei and mitochondria
33
How do antagonistic muscle pairs work
When one muscle contracts, the opposing muscle relaxes.
The contracting muscle shortens and pulls on its attached tendon.
This tendon pulls on the bone, causing movement at the joint.
The relaxing muscle lengthens to allow the movement.
34
Microscopic skeletal muscle structure
H zone - Band of only myosin
Z line - End of each sarcomere
M line - Centre of a sarcomere
I band - Band where there is only actin
A band - Band where both filaments overlap
Actin filament
Myosin filament
35
Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force of muscle contraction.
1. (Less/No) tropomyosin moved from binding site
2. (Fewer/No) actinomyosin bridges formed;
3. Myosin head does not move
36
Describe the roles of calcium ions and ATP in the contraction of a myofibril. (5)
1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
2. (Calcium ions) cause movement of tropomyosin (on actin);
3. (This movement causes) exposure of the binding sites on the actin;
4. Myosin heads attach to binding sites on actin;
5. Hydrolysis of ATP (on myosin heads) causes myosin heads to bend;
6. (Bending) pulling actin molecules;
7. Attachment of a new ATP molecule to each myosin head causes myosin heads to detach (from actin sites).
37
Role of phosphocreatine
Donates phosphate to ADP to form ATP.
ATP can phosphorylate creatine ton phosphocreatine.
38
The structure and adaptations of slow skeletal muscle fibres.
Large store of myoglobin - Myoglobin has a higher affinity for oxygen than haemoglobin so carries more oxygen for more efficient aerobic respiration over long time periods.
Rich blood vessel supply - This provides more oxygen to respiring cells.
Many mitochondria - This allows more ATP synthesis.
39
The location of slow and fast skeletal muscle fibres.
Slow - legs (places that require endurance)
Fast - eyes
40
The structure and adaptations of fast skeletal muscle fibres.
More myosin filaments - This increases the ability for muscles to generate a greater force.
High concentration of glycogen - This can be broken down into glucose to provide more respiratory substrates.
High concentration of enzymes involved in anaerobic respiration
Store of phosphocreatine - This can be broken down rapidly to provide phosphates to synthesise ATP during contraction.
41
H zone
Band of only myosin
42
Z line
End of each sarcomere
43
M line - Centre of a sarcomere
Centre of a sarcomere
44
I band
Band where there is only actin
45
A band
Band where both filaments overlap
46
The importance of maintaining a stable core temperature and stable blood pH
Enzymes are denatured at low/high pHs and high temperatures
Enzymes work too slow if at low temperatures
47
The importance of maintaining a stable blood glucose concentration in terms of availability of respiratory substrate and of the water potential of blood.
Too high glucose concentration - cell might shrink due to low water potential of blood, excreted in urine
Too low glucose concentration - cell might burst due to high water potential of blood. May not be enough glucose for respiration
48
What does a negative feedback loop do
restores systems to their original level
49
Glycogenesis
The formation of gylcogen from glucose removed from the blood
50
Glycogenolysis
The breakdown of stored glycogen into glucose, which can be released into the blood
51
Gluconeogenesis
Synthesis of glucose form other molecules such as amino acids
52
Action of Insulin
- Attaches to receptors on the surfaces of target cells
- Controls the uptake of glucose by regulating the inclusion of channel proteins in the surface membranes of target cells
- Activating enzymes involved in the conversion of glucose to glycogen.
53
Action of Glucagon
- Attaches to receptors on the surfaces of target cells
- Activates enzymes involved in the conversion of glycogen to glucose
- Activates enzymes involved in the conversion of glycerol and amino acids into glucose.
54
Action of Adrenaline
- Attaches to receptors on the surfaces of target cells
- Activates enzymes involved in the conversion of glycogen to glucose.
55
Explain why glucose is found in the
urine of a person with untreated diabetes.
1. High concentration of glucose in blood/filtrate;
2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;
3. Carrier/co-transport proteins are working at maximum rate
56
Describe the role of glucagon in gluconeogenesis.
(Attaches to receptors on target cells and) activates/stimulates enzymes;
2. Glycerol/amino acids/fatty acids into glucose;
57
What is a primary messenger + example
Messengers that do not enter cells, they bind to receptors and trigger change (either a reaction or activating another molecule)
e.g hormones
58
What is a secondary messenger + example
Messengers that initiate and coordinate responses form inside the cell, normally activated by primary messengers binding to a cell surface receptor.
e.g. cAMP
59
Describe cAMP's role as a secondary messenger
- Adrenaline/glucagon are primary messengers and bind to receptors on liver cells
- Activating adenylate cyclase, which converts ATP to cyclic AMP (cAMP)
- cAMP activates enzyme protein kinase A, which triggers reaction causing glycogenolysis
- Glycogenolysis breaks down glycogen into glucose
60
How is high blood glucose concentration dealt with
1. Detection by beta cells in islets of Langerhans
2. Beta cells secrete insulin into the blood
3. Insulin binds to receptors on muscle cells membranes
4. Muscle cells insert more glucose carrier proteins into the cell surface membrane
5. Insulin binds to receptors on the liver.
6. The liver cells produce enzymes that convert glucose to glycogen.
61
How is low blood glucose concentration dealt with - glucagon
1. Detection by alpha cells in islets of Langerhans
2. Alpha cells secrete glucagon into the blood
3. Glucagon binds to receptors on liver cell membranes
4. Glycogen converted to glucose by enzymes
5. Binding of glucagon also causes the release of enzymes that form glucose from glycerol and amino acids. (gluconeogenesis)
6. Glucagon also slows rate of respiration in cells
62
How is low blood glucose concentration dealt with - adrenaline
1. Adrenal gland secretes adrenaline
2. Adrenaline binds to receptors on the liver cell membrane.
3. Activation of glycogenolysis (glycogen → glucose).
4. Inhibition of glycogenesis (glucose → glycogen).
5. Adrenaline also promotes secretion of glucagon from the pancreas and inhibits secretion of insulin.
63
Cause of type 1 diabetes
Immune cells attack beta cells
Beta cells damaged and no longer produce insulin
64
Cause of type 2 diabetes
Beta cells no longer produce enough insulin
OR
When muscle cells/liver cells stop responding to insulin
65
Treatment of type 1 diabetes
Insulin injections to combat hyperglycemia
Not too much otherwise hypoglycemia
Diet
66
Treatment of type 2 diabetes
Diet
Exercise
Sometimes medication
67
Increased blood pressure
Detected by baroreceptors
Send impulses to cardiac centre
More impulses to SAN
By parasympathetic nervous system
Acetylcholine released
68
Increased blood pH
Chemoreceptors detect increase in CO2 concentration
Send impulses to cardiac centre
More impulses to SAN
by sympathetic nervous system
69
When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicle in the presynaptic knob. Describe how.
1. Depolarisation of membrane cause calcium ion channels to open
2. Ca2+ enter by facilitated diffusion
3. Causes synaptic vesicle to fuse with presynaptic membrane
70
How myosin molecules moves mitochondria towards presynaptic membrane
1. Myosin head attaches to actin AND bends
2. This pulls mitochondria along the actin
3. Next myosin attaches to actin and bends
71
Suggest and explain one advantage of the movement of mitochondria towards the presynaptic membrane.
Mitochondria supply additional ATP
For:
- Active transport
- Movement of vesicles
- For myosin to move past actin
72
Bowman's capsule
Beginning of the tubules that make up the nephron.
Surrounds a network of capillaries - the glomerulus
The first step of filtration of the blood to form urine takes place in the Bowman's capsule. This step produces the glomerular filtrate.
73
Afferent and efferent arterioles
Blood flows into the glomerulus through the afferent arteriole and out of the glomerulus through the efferent arteriole.
The afferent arteriole is much wider than the efferent arteriole. This means that the blood pressure in the capillaries is very high.
Small molecules are absorbed, but large structures remain in the blood.
74
Proximated Convoluted Tubule (PCT)
Site of selective reabsorption.
After the glomerular filtrate has been produced in the Bowman's capsule, glucose and water are reabsorbed into the bloodstream through the PCT.
75
Loop of Henle
Produces a low water potential in the medulla of the kidney.
Consists of an ascending limb and a descending limb.
The ascending limb is impermeable to water.
The descending limb is permeable to water.
76
Collecting duct
Water is reabsorbed into the blood through the collecting duct.
The amount of water that is absorbed depends on the water potential of the blood.
If blood water potential is low, more water is reabsorbed.
If blood water potential is high, less water is reabsorbed.
This is osmoregulation.
77
Osmoregulation pathway
Bowman's capsule -> Glomerulus -> Afferent arteriole -> Efferent arteriole -> PCT -> Loop of Henle -> Collecting duct
78
Role of ADH
- Increases permeability of DCT (Distal Convoluted Tubule) and collecting duct som less water absorbed in urine, more reabsorbed
- Opens aquaporins so water reabsorbed by osmosis
79
Aquaporins
- ADH increases permeability of DCT and collecting duct
- ADH binds to receptor causing protein channels called aquaporins to move into their cell surface membrane
- An increase in aquaporins allows more water ro pass through the membrane by osmosis
80
Osmoregulation
1. Osmoreceptors in the hypothalamus detects the change in water potential of the blood.
2. Hypothalamus produces ADH which it secretes into the pituatary gland
3. Posterior pituitary gland releases ADH
4. ADH makes the collecting duct more permeable, causing more water to be reabsorbed by osmosis from the DCT and collecting duct
5. Less water is lost in urine
6. Blood water returns to normal
81
Ultrafiltration
1. Blood enters through the afferent arteriole, which splits up into the glomerulus, increasing hydrostatic pressure of blood
2. Water and small molecules are forced out of the capillaries, this is the glomerulus filtrate
3. Large proteins and blood cells are too big to fir through the gaps in the capillary so remain in the blood
4. This blood leaves for the efferent arteriole
82
What is urea made from
Ammonia and CO2. Urea is less soluble and toxic than ammonia
83
IAA causing the cell to elongate
1. IAA molecules bind to receptors on the cell surface membrane
2. Stimulating ATPase proton pumps to pump H+ ions from the cytoplasm into the cell wall
3. Acidifying the cell wall
4. Activates expansin proteins which loosen the bonds between fibrils
5. At the same time K+ ion channels are stimulated to open
6. Leads to an increase in K+ ion concentration in the cytoplasm, decreasing its water potential
7. causes the cell to absorb water by osmosis which is then stored in the vacuole
8. Increasing the internal pressure, causing the cell wall to stretch
9. Cell elongates
84
Phototropism
Growth in response to the direction of light
85
Gravitropism
Growth in response to the direction of gravity
86
Distribution of IAA
IAA can be transported over short distances (by diffusion or active transport) and longer distances (in the phloem) around the plant.
When a plant detects directional stimuli, IAA is transported to different parts of the plant.
This creates an uneven distribution of IAA.
Where the distribution of IAA is uneven, a directional growth response occurs.
87
Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes.
1. High concentration of glucose in blood/filtrate;
2. Not all the glucose is (re)absorbed at the
proximal convoluted tubule;
3. Carrier/co-transport proteins are working at
maximum rate
88
A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV to 0 mV.
Explain why [3]
1. No/less ATP produced;
2. No/less active transport
3. Electrochemical gradient not maintained
89
Why must glucose be converted into glycogen
Glucose is soluble so will reduce the water potential of the cell, causing water to move in by osmosis which could make it burst
90
PCT adaptations
- Microvilli provide a large surface area for reabsorption
- Lots of mitochondria to provide energy for active transport of sodium ions
91
Growth factor definition
Chemicals that influence pant development by modulating cell elongation and division
92
Positive phototropism
1. IAA is produced in cells in the tip of the plant shoot
2. IAA is transported down the plant shoot
3. Light stimulates IAA to move to the shaded side of the shoot
4. IAA becomes concentrated and stimulates cell elongation on shady side
5. Shoot bends towards to light
93
Negative phototropism & positive gravitropism
1. IAA is produced in cells in the tip of the plant root
2. IAA is transported down the plant root
3. Light stimulates IAA to move to shaded side of shoot
4. Gravity pulls IAA to lower side of root
5. IAA becomes concentrated and inhibits cell elongation on shaded lower side
6. Root bends away from light and towards the pull of gravity
94
Role of IAA in shoot elongation
1. Auxin binds to cell surface membrane
2. Hydrogen ions are actively transported from cytoplasm into cell wall
3. Cell wall becomes more plastic
4 Cell elongates and plant grows
