1
Q
taxes,taxis (singular)
A
is a simple response in which direction of movement of the organism is determined by the direction of the stimulus - movement of a whole organism towards (positive) or away (negative) from directional stimulus
2
Q
positive phototaxis
A
- movement of simple photosynthesising organisms towards light - increases their change of survival as they need light
3
Q
negative phototaxis
A
- eg earthworms move away from light - increasing their chance of survival as they move into soil and are not expose to predators
4
Q
chemotaxis
A
- movement towards or away from high conc of a particular substance - eg bacteria move towards a food source of away from toxic compounds
5
Q
kineses
A
- this is a form of response in which the organism does not move of away from a stimulus - response is related to intensity of the stimulus and involves a change in the rate of movement - eg- woodlice in a dry env respond by moving more rapidly but turning less often
6
Q
tropism -shoots
A
- is the growth of part of a plant in response to a directional stimulus - positive or negative depending on growth towards or away from the stimulus - can maintain the shoots and roots of plants - plant shoots grow towards light (positive phototropism) and grow away from gravity (negative geotropism)
7
Q
tropism - roots
A
- plants roots grow away from light (negative phototropism) and towards gravity (positive geotropism) - grow towards water - positive hydrotropism
8
Q
Indoleacetic acid (IAA)-auxin
A
- is a plant growth factor that stimulates plant growth - it is produced in the growing regions of a plant eg shoot and root tips - causes cell elongation in shoots - inhibits cell elongation in roots
9
Q
IAA and phototropism
A
- cells in the shoot tip produce IAA that diffuses down the shoot and stimulates upward growth of the shoot - if shoot is exposed to unidirectional light stimulus, light causes the movement of IAA from the illuminated side to the shaded side of the shoot - can cause build up on shaded side of shoot - high conc of IAA causes greater elongation of the cells on the shaded side - bends towards the light
10
Q
what makes the heart beat
A
- the heart is myogenic - this means that’s the heart cusses itself to beat without any external stimulation
11
Q
SAN
A
- patch of modified muscle cells in wall of right atrium - produces regular bursts of electrical impulses - impulses spread through the walls of r/l atria - atria contract together - SAN sends impulses to AVN
12
Q
AVN
A
- ventricles are electriclly insulated from atria - AVN receives impulses from SAN - delay before AVN reacts - AVN sends impulses down a groip of muscles fibres - Bundle of His - Bundle splits into finer muscles fibres called Purkyne fibres which carry electrical activity - ventricles contract together after the atria - ventricular contraction starts at the bottom, - pushing the blood up into the arteries
13
Q
autonomic nervous system
A
- is a part of the nervous system which controls the heart rate - overall control of the ans is by centred in the medulla and hypothalamus - two divisions of the ans are the sympathetic nervous system and the parasympathetic nervous system - both sns and pns generally have antagonistic (opposing) effects on the organs they supply eg increase in heart rate is due to release of noradrenaline by sympathetic neurons whereas acetylcholine by pns slows down heart rate
14
Q
Sympathetic pathway
A
- heart rate is speeded up eg during exercise - by the medulla sending more impulses along sympathetic neurones to the SAN/ neurotransmitter noradrenaline is released by sympathetic neuron stimulating SAN
15
Q
Parasympathetic pathway
A
- heart rate is slowed down by the medulla sending more impulses along parasympathetic neurones to SAN / neurotransmitter acetylcholine is released by pns inhibiting the SAN
16
Q
heart rate during exercise process
A
1- increase in rate of respiration 2-increases production of co2-dissovled carbonic acid lowers ph in the blood 3-chemorecpetors in the aortic and carotid bodies are stimulated/ detected ph 4- this transmits more impulses to cardiac centre in medulla 5- increases heart rate by transmitting more impulses from medulla vis sympathetic pathway to SAN
17
Q
blood pressure during heart rate (exercise)
A
1- during exercise, there is an increase in venous blood returning to the heart 2- cardiac muscles contract more strongly 3- increasing blood pressure detected by baroreceptors 4- sends impulses to the medulla 5- stimulates cardioinhibitory centre and inhibiting the cardio acceleratory centre 6- more impulses move down parasympathetic neurons to SAN-decreasing heart rate
18
Q
the resting potential
A
- neurons are polarised ( inside the axon is neg charged eg -70mV) - is when potential difference across the membrane of an axon when an impulse is not being transmitted is known as resting potential
19
Q
resting potential being maintained
A
1- membrane being differentially permeable eg more permeable to loss of potassium ions than intake of sodium ions - this is due to many more potassium channels being open than sodium channels 2- sodium/potassium pump actively transports the ions (3 na+ out and 2 k+ ions in) against their diffusion gradients which requires atp 3- there is a higher conc of na+ and lower conc of k+ outside the axon 4- more k+ inside than na+ memrabne becomes more permeable
20
Q
depolarisation
A
- an action potential involves a change in the potential across the axon membrane from a negative inside value eg -70mV to a positive value of +40mV - when a receptor is stimulated above it’s threshold it generates an action potential and transmits a nerve impulse - results from an increase in permeability of an axon membrane to sodium ions as sodium channel proteins (voltage-gated channels) in the membrane open - the sodium ions diffuse in down conc gradient - causes more sodium channels to open, more sodium ions diffuse
21
Q
repolarisation
A
- when the membrane is fully depolarised the sodium channels close - permeability of the membrane to sodium ions decreases - the potassium voltage-gated channels in the membrane open - more potassium ions begin to diffuse out of the axon - sodium/potassium pump restores the resting potential by actively removing sodium ions which entered and returns potassium ions back into the axon
22
Q
Hyperpolaristion
A
- k+ channels take longer to close - the potential across the cell membrane becomes slightly more negative than the rest
23
Q
“All or nothing” principle
A
- stimulus must be above certain threshold for an impulse to be generated - a larger stimulus causes a higher frequency of impulses
24
Q
factors affects speed of conductance along neuron
A
Temp -an increase in temp increases the speed of transmission- increase in the diffusion of ions in and out axon - axon diameter- greater the diameter of an axon the faster the speed of conduction - myelination - myelinated neurons the speed of transmission increased as action potential ‘jumps’ from one gap to the next
25
Synaptic transmission
- action potential arrives at synaptic knob causes depolarisation of the presynaptic membrane - stimulates calcium channels to open in the presynaptic membrane and calcium ions diffuse into the synaptic knob - calcium ions cause the synaptic vesicle to fuse with pre synaptic membrane and break open - neutransmitter eg acetylcholine is released and diffuses across the synaptic cleft - acetylcholine attaches to specific protein receptor sites on the postsynaptic membrane - This stimulates the entry of sodium ions - leads to depolarization of the postsynaptic neuron and transmission of an impulse - acetylcholine is broken down in the postsynaptic membranes by acetylcholinesterase forming acetyl and choline
26
Rods
- particularly useful for vision at low light intensities/possesses high visual sensitivity
27
Cones
- are important for good discrimination of detail eg high visual acuity and enable colour vision
28
Visual sensitivity
- refers to ability to see at low light intensities - rods have higher visual sensitivity than cones / two reasons - rhodopsin which is photosensitive pigment in rods is broken down at lower light intensities than iodopsin in photosensitive pigment in cones - serveal rod synapse with one bipolar neuone whereas cone synapses with one bipolar neuron - many rods synapse to a single bipolar cell - stimulates of serves; roses next to each other has an additive effect ( spatial summation )
29
visual acuity
- acuity refers to the ability to discriminate detail - comes have high visual acuity as most cones synapse with only one bipolar neuron - has 1:1 maximum possible acuity / which is greatest at the fovea as it only contains cones - Rods have low visual acuity due to rods sharing a bipolar neuron
30
colour vision
- 3 types of cones / all possess a different pigment / -red/blue/green light sensitive cones absorb light corresponding to the wavelengths of each colour - each pigment has its own absorption peak - when a cone cell absorbs more light/produces a greater frequency of impulses
31
Muscle fibres
- are cylindrical in shape and are enclosed by a cell surface membrane or sacrolemma - have many nuclei - contain numerous protein strands or myofibrils - arranged in parallel to give a striped appearance
32
skeletal muscle strcutre
a band - all myosin / thicker than actin i band - actin only / lighter section -darkest section / where actin and myosin overlap m line- connects myosin filaments in the a-band h zone- at the centre of the a-band/contains only myosin filaments z line- connects these actin filaments and is the boundary of the scaromere
33
muscle contraction
- h zone within the a-band narrows / contains only myosin filaments - outer darker regions of the a band becomes wider / contains overlapping actin and myosin filaments -a-band remains the same size -the i-band narrows -z-line moves closer together
34
myosin and actin
- myosin forms the thick filaments and is composed of many myosin molecules bundled together - heads of the myosin extend out from the shaft of the surface -myosin heads have ATP hydrolase / hydrolyse ATP providing energy for muscle contraction -actin forms the thin filament and possesses binding sites for myosin heads
35
mechanism for muscle contraction/ formation of cross bridges between actin and myosin
- the binding site on actin filaments in relaxed muscles is covered by protein/tropomyosin - muscle contraction is stimulated/activated by calcium ions released from the sacroplasmic reticulum/ in the muscles fibre when the fibre is stimulated -when released / calcium ions bind to tropomyosin/ causing it to change shape and move to the binding site - this enable actinmyosin bridges to forms myosin heads attach to actin filaments - calcium ions stimulate action of atp hydrolase present on myosin heads / hydrolyses atp / providing energy to move myosin head which pulls actin filament and detach the myosin heads which breaks bridges
36
slow skeletal muscle fibres
- contract slowly - many mitochondria per fibre - energy released slowly through aerobic respiration - high resistance to fatigue - good for endurance events eg marathons - low conc of glycogen - low conc of phosphocreatine
37
fast skeletal muscle fibres
- contracts very quickly - few mitochondria per fibre - energy released quickly through anaerobic respiration - low resistant to fatigue - good for short bursts of energy eg sprints - high conc of glycogen - high conc of phosphocreatine
38
uses of atp in muscles
-to move myosin heads which pull actin filament -to detach the myosin head which breaks the actin-myosin bridges -for reabsorption of ca ions into endoplasmic reticulum by active transport
39
atp production / phosphocreatine
-phosphocreatine is stored in muscles / used to as a reserve supply of phosphate to combine with ADP to form ATP (in fast muscle fibres) produced in anaerobic respiration
40
atp production/ anaerobic respiration
- atp is made rapidly in glycolysis produces pyruvate / oxygen is in short supply pyruvate is converted into lactate builds up in the muscle and causes muscle fatigue
41
Sliding filament hypothesis
- Myosin and actin filaments slide over one another to make sarcomeres contract - Myofilaments don't contract - Simultaneous contraction of lots of sarcomeres means myofibrils and muscle fibres contract - Sarcomeres return to their original length as muscle relaxes
42
In resting (unstimulated) muscle, why are actin-myosin binding sites blocked by tropomyosin?
So myofilaments can't slide past each other ∵ myosin heads can't bind actin-myosin binding site on actin filaments
43
Describe how muscles contract in detail
When action potential from motor neurone stimulates muscle cell, it depolarises sarcolemma - Depolarisation spreads down T-tubules - sarcoplasmic reticulum releases Ca²⁺ into sarcoplasm - Influx of Ca²⁺ causes tropomyosin molecules to more, exposing binding sites - Myosin heads, have ADP attached, attach to binding site on actin, creating actin-myosin cross bridge - Ca²⁺ activate ATPase to hydrolyse ATP to ADP - Energy released causes myosin heads to bend, pulling actin filament - Another ATP molecule attaches to myosin head, causing myosin to detach from actin - With ADP myosin head can reattach to actin - Myosin head then reattaches to different binding sites further along actin
44
Why is anaerobic respiration only good for short periods of hard exercise?
-ATP rapidly made by glycolysis -Lactate quickly builds up in muscle & = muscle fatigue
45
muscle contraction steps
At rest, troponin blocks tropomyosin binding site on actin 1. Action potential arrives 2.causes sarcoplasmic reticulum to release ca ions into sarcoplasm 3. ca ions activates atp/ hydrolyses to provide energy for muscle contraction and allows myosin head to bend and pull actin 4. Ca ions bind to tropomyosin / changes it shape 5. This pulls attached top myosin out of the actin myosin binding site / exposes the binding site 6. Allows myosin the bind and bend / forms actin myosin cross bridges
46
ATP uses / aerobic respiration
-generated via oxidative phosphorylation in mitochondria / used in long period low intensity exercise
47
ATP uses / anaerobic respiration
- made by glycolysis /produces pyruvate converted into lactate / which builds up in the muscles causing muscle fatigue / used in short period of exercise
48
homeostasis
- involves physiological control systems that maintain the internal environment within restricted limits
49
homeostasis / maintains
- a stable core temperature to provide an optimum temp for enzyme activity - a stable blood ph to provide an optimum ph for enzyme activity - a stable blood glucose conc to provide substrate for respiration to release energy - water potential of blood within restricted limits so that excess water does not enter or leave body cells by osmosis
50
Control of blood glucose concentration / increase in blood glucose
Increase in blood glucose - pancreas detects a rise in blood glucose conc / which secretes insulin / attaches to specific receptor on the surface of target cells eg liver and muscles - insulin activates enzymes in the liver and muscles that convert glucose into glycogen (glycogenesis) / excess glucose converts into glycogen
51
decrease in blood glucose
- blood conc decreases eg during exercise / detected by pancreas which secretes hormone glucagon into the blood
52
Control of blood glucose concentration
increase in blood glucose,Increase in blood glucose - pancreas detects a rise in blood glucose conc / which secretes insulin / attaches to specific receptor on the surface of target cells eg liver and muscles - insulin activates enzymes in the liver and muscles that convert glucose into glycogen (glycogenesis) / excess glucose converts into glycogen
53
decrease in blood glucose
- blood conc decreases eg during exercise / detected by pancreas which secretes hormone glucagon into the blood - glucagon attaches to specific receptors on the surface of target cells of liver and activates enzymes which hydrolysis glycogen. Into glucose (glycogenolysis)/ glucose is released into the blood - during extensive exercise or starvations glucagon activates enzymes which convert glycerol and amino acids into glucose (gluconeogensis) which is released into the blood
54
Adrenaline
- hormone released by adrenal glands when glucose conc is low - attached to receptors on the surface of specific target cells and activates enzymes to hydrolysis glycogen into glucose
55
Second messenger model of adrenaline and glucagon
- adrenaline and glucagon bind to surface receptors of these cells / first messenger - when they attach to this specific receptors its activates the enzymes adenyl cyclase in cell membrane -adenylate cyclase converts ATP to cyclic AMP / which acts as a second messenger - cyclic AMP activates enzymes protein kinase which stimulates hydrolysis of glycogen to glucose - glucose is released into the blood to increase blood glucose
56
Type 1 diabetes
-occurs when the cells in the pancreas's responsible for production of insulin are destroyed by immune system / occurs in childhood / no insulin produced
57
Type 2 diabetes
- usually in adult life - failure to produce insulin - fewer insulin receptors are faulty / no longer produce insulin - cells take up less glucose / converted into glycogen / blood glucose conc remains high
58
Managing diabetes / type 1
- insulin dependent / must inject themselves daily with insulin
59
Managing diabetes / type 2
- have high blood glucose / needs to control their diet
60
Control of blood water potential
Regulation of water levels in the blood to maintain homeostasis.
61
Ultrafiltration
- occurs in the glomerulus and the renal bowman's capsule of each nephron resulting in the formation glomerular filtrate
62
Ultrafiltration process
-Blood enters the glomerulus through the afferent arteriole. -Blood leaves the glomerulus via the smaller efferent arteriole, maintaining a high hydrostatic pressure. -This high pressure forces molecules, like water and small solutes, out of the blood through pores in the capillary endothelium / holds back blood cells -The molecules move through the basement membrane, which has that act as a selective filter / main fine filter preventing large molecules and blood cells from passing into the Bowman's capsule. The molecules move through the Bowman's capsule epithelium, which has specialised cells called podocytes with extensions known as pedicels that wrap around capillaries and help to filter the blood. Filtered fluid collects in Bowman's capsule.
63
simple ultrafiltration process
- renal artery - affernt arteriole (blood under high pressure) contraction of LV -glomerulus (capillary network) - ultrafiltration occurs - efferent arteriole
64
proximal convoluted tubule (PCT)
first section of the renal tubule that the blood flows through; reabsorption of water, ions, and all organic nutrients by facilitated diffusion and then by active transport / water absorption moves by osmosis / down wp gradient
65
PCT adaptations for selective reabsorption
- microvilli (large SA) - tight junctions between cells (prevents cells diffusing back into glomerular filtrate/into adjacent cells) - short diffusion pathway - basal channels - mitochondria (ATP for active transport of glucose/ions)
66
Role of Loop of Henle
To allow mammals to produce urine that is more concentrated than their own blood
67
Loop of Henle
1- na and cl ions are actively transported out of the ascending limb / ascending limb is impermeable to water / increases in wp filtrate and declares wp in surrounding tissue fluid of medulla 2- creates a high conc of ions in tissue of the medulla 3- tissue of medulla has a low water potential
68
distal convoluted tubule (DCT)
segment of the nephron between the nephron loop and the collecting duct
69
Rods vs Cones
Rods
-found in the retina except the fovea
- used in low light
- contains pigment rhodopsin
-low visual acuity
Cones
- found in fovea
- work in bright light
- contains pigment for red, blue and green
- high visual acuity
70
Fovea
- contains only cones
- cones are tightly packed
- each cone its own bipolar neuron / separate impulses
- three types of cones / colour vision
71
What causes vision using the fovea
- fovea contains many cone cells
72
Why fovea has high visual acuity
- each receptor has its own bipolar neurone
- no spatial summation
73
ADH
Antidiuretic hormone. Therefore, ADH causes an increase in the permeability of the walls of the collecting duct and distal convoluted tubule to water.
74
Aquaporin
This means more water leaves the nephron and is reabsorbed into the blood by osmosis, so urine is more concentrated. Aquaporin pores are inserted into cell membrane, increasing flow of H2O out of tubule.
75
Hypothalamus
Changes in the water potential of the blood are detected by osmoreceptors here.
76
ADH production
If the water potential of the blood is too low water leaves the osmoreceptors by osmosis and they shrivel. This stimulates the hypothalamus to produce more of the hormone ADH.
77
ADH reduction
If the water potential of the blood is too high water enters the osmoreceptors by osmosis. This stimulates the hypothalamus to produce less ADH.
78
Social behaviors
Affects some social behaviors in mammals.
79
Produced by
nypothalamus
80
Released by
posterior pituitary
81
ADH release
The hypothalamus is where ADH is produced. ADH then moves to the posterior pituitary and from here it is released into capillaries and into the blood.
82
ADH target organ
ADH travels through the blood to its target organ, the kidney.
83
Loop of Henle
Maintaining Sodium Ion Gradient
84
Descending Limb
The walls are thin and permeable to water, but impermeable to ions. As the filtrate moves down the descending limb, water moves out by osmosis into the surrounding medulla, due to the lower water potential in the interstitial space. This concentrates the filtrate.
85
Ascending Limb
The walls are thick and impermeable to water. Sodium ions are actively transported out of the ascending limb into the surrounding medulla using ATP from mitochondria in the epithelial cells. At the base of the ascending limb where the filtrate is very concentrated, sodium ions also diffuse out. This creates a high concentration of sodium ions in the medulla, lowering its water potential, which is essential for water reabsorption later.
86
Proximal convoluted tubule
reabsorbs ions, water, and nutrients; removes toxins and adjusts filtrate pH
87
Glomerulus
filters small solutes from the blood
88
Descending loop of Henle
aquaporins allow water to pass from the filtrate into the interstitial fluid
89
Ascending loop of Henle
reabsorbs Na* and Cl- from the filtrate into the interstitial fluid
90
Distal tubule
selectively secretes and absorbs different ions to maintain blood pH and electrolyte balance
91
Collecting duct
reabsorbs solutes and water from the filtrate
unit 6
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