Topic 6 last Flashcards
(63 cards)
1
Q
What are stimuli?
A
- Internal/external changes to the environment
2
Q
What are 3 different responses?
A
- Tropisms
- Taxes and Kineses
- Simple reflexes
3
Q
What is a tropism?
A
- Growth response of a plant to a stimulus
4
Q
How are tropisms controlled?
A
- Growth factors such as hormones
5
Q
Where are growth factors produced?
A
- Produced in growing regions and move to other tissues, where they regulate growth in response to a direcitonal stimulus
6
Q
Phototropism vs Gravitropism?
A
Phototropism
Shoots - IAA causes cell elongation
Roots - IAA inhibits cell elongation
- Light is detected by receptors in the shoot
Positve phototropism:
- IAA diffuses to the darker side
- Concentration of IAA increases on this side
- IAA causes cells on the darker side to elongate so the shoot bends towards the light
Negative phototrpoism:
- In roots, IAA does the opposite
- IAA diffuses to the darker side (underside)
- Cell elongation is inhibited, root bends downwards.
Negative Gravitropism
- IAA diffuses to lower side of the shoot
- Concentration of IAA increases on the lower side
- IAA causes elongation directly upwards
Positive Gravitropism
- IAA diffuses to lower side of the root
- Inhibits cell elongation and root bends downwards.
7
Q
Taxis vs Kinesis
A
- Responses that maintain a mobile organism in a favourable environment
Taxis - Organism moves towards/away from a directional stimulus
Kinesis
- Organism’s movement affected by a non-directional stimulus such as humidity
- Cause rate of turning to increase or decrease to move the organism away from the stimulus
8
Q
How do simple reflexes work?
A
- Receptor detects stimulus
- Sensory neurone carries impulse from receptor to relay neurone
- CNS processes response
- Relay neurone carries impulse to the motor neurone
- Motor neurone carries impulse from relay neurone to effector
- Effector carries out response (muscle or gland)
9
Q
Why are simple reflexes important?
A
- FAST
(Does not involve concious part of the braint because the impulse is carried directly from a sensory neurone to a motor neurone via a relay neurone. - LOCALISED
- Target cells, stimulus produce same response
- SHORT LIVED
- Re uptake of neurotransmitter is rapid
- Response is involuntary where the body cannot override it.
(Aid survival by protecting the body from tissue damage and escape from predators)
10
Q
Different types of receptors
A
Baroreceptors (pressure)
Chemoreceptors (chemical)
Photoreceptors (light)
11
Q
Outline pacinian corpuscle
A
- Detect pressure/vibrations
- Contain sensory neurone endings wrapped in tissues of lamella
- Found in fingertips, soles, joints
1) Pressure cause lamellae to be deformed
2) Increase in pressure deforms stretch mediated sodium ion channels
3) Sodium ion channels open and sodium ions diffuse into the sensory neurone ending
4) Depolarises the membrane creating generator potential
5) AP triggered when threshold reached
12
Q
How is AP generated?
A
- Potential difference between inside and outside
- Resting potential is -70mV when cell is at rest
- When stimulus is detected, the membrane becomes more permeable so ions diffuse across it and the potential difference increases
- Change in potential difference is called the generator potential
- If the change is large enough and exceeds the threshold value, then an action potential is triggered.
13
Q
Outline how the retina responds to light?
A
- Light is detected by photoreceptors
- Light is absorbed by optical pigments
- Light bleaches the pigments, altering the membrane permeability to sodium ions
- Generator potential is created and if large enough and over threshold, causes an action potential
- Bipolar neurone connects to the optic nerve, taking the impulses to the brain
14
Q
Compare rods and cones?
A
- Rods have high sensitivity because many rods connect to 1 bipolar neurone so many weak generator potentials combine to reach threshold
- Cones have low sensitivity to light as 1 cone connects to a bipolar neurone meaning it takes more light to reach the threshold and generate an action potential
- Rods have low sensitivity to colour as they are ponly sensitive to light levels
- Cones have high sensitivity to colour as there are 3 different types of cones representative of different colours
- Rods have low visual acuity (how clearly you can see objects at a distance) because many rods connect to 1 bipolar neurone so light from 2 points close together can’t be distinguished.
- Cones have 1 cone connected to 1 bipolar neurone so separate impulses are sent, many action potentials triggered so the brain receives many impulses.
15
Q
What does myogenic mean?
A
- Muscle initiates contraction without nerves
16
Q
Heart contraction process
A
- SAN in right atrium sets the frequency at which the cardiac muscle cells contract, sending out regular electrical impulses to the atrial wall, causing atria to also contract.
- impulse spreads from SAN across both atria, causing contraction simultaneously
- Septum prevents impulses crossing
- Impulses reaches AVN
- AVN passes impulse to the Bundle of His fibres, which conduct the impulse down the Purkyne fibres
- Impulse reaches the heart apex causing them both to contract simultaneously, from bottom up.
17
Q
Why is there a short delay during heart contraction
A
- To allow all the blood to empty from the atria before ventricles contract.
18
Q
How do we actually control heart rate?
A
- Done by the autonomic nervous system
- Controlled by the medulla
- Heart rate is changed in response to internal stimuli (blood pressure (barocreceptors) , chemicals in the blood (chemoreceptors) E>G carbon dioxide)
- Sends electrical impulses to the medulla via sensory neurones which processes the info and sends the impusle to the SAN down the autonomic nervous system (sympathetic - increase heart rate (noradrenaline), parasympatheitc - decreases heart rate via acetylcholine (less frequent heart contractions)) Antagonistic
19
Q
where do noradrenaline and acetylcholine bind to?
A
- The SAN
20
Q
Structure of motor neurone
A
- Cell body
- Dendrites (recieves electrical impulses)
- Nucleus
- Axon (transfers electrical impulses to synapse)
- Myelin sheath (electrical insulation made of schwann cells)
- Synapses
21
Q
How is the Resting potential established
A
- 3 sodium ions actively transported out
- 2 potassium ions actively transported in via sodium-potassium pump
- outside of axon is more positive than inside of axon
- resting potential is -70mV
22
Q
How is the Action potential created
A
- Depolarisation involves stimulus exciting membrane so the cell membrane becomes more permeable to sodium ions
- Sodium ion channels open allowing diffusion of sodium ions
- Inside becomes more positive as potassium ion channels stay closed.
- Repolarisation involves sodium ion channels closing and potassium ion channels opening so potassium ions diffuse out of the neurone.
- Inside of neurone becomes more negaitve and voltage decreases back to normal level.
- Hyperpolarisation involves potassium ion channels remaining open for a short time and too many potassium ions diffuse out of neurone
- Resting potential is re established
23
Q
3 advantages of refractory period
A
Refractory period is the time delay which prevents ion channels from opening
- Keeps action potential unidirectional
- No overalp
- Time limit to action potential frequency
24
Q
Myelination vs Unmyelination
A
- Myelination sees regular breaks in insulation (nodes of ranvier)
- APs only occur at nodes of ranvier
- APs jump via saltatory conduction between nodes of ranvier
- Quicker nerve transmission, so less energy is needed from the sodium potassium pump
25
All or nothing
- Action potential only happens if stimulus reaches threshold
- Action potential is always the same size
- Size of stimulus from frequency of impulses and neurones with a different threshold value
26
Factors that affect speed of impulse
- Myelination
- Axon diameter - less resistance to the flows of ions
- Temperature - more kinetic energy
27
What is a synpase?
- Junction between neurones or neurones and a muscle
- Found at the ends of axons
- Most use cholinergic synapses or neuromuscular junctions
28
Outline transmission across a cholinergic synapse...
- Action potential arrives at synpatic knob of presynaptic neurone
- Stimulates calcium ion channels to open allowing diffusion and influx of calcium ions, triggering vesicles to move to the membrane, releasing acetylcholine into the synpatic cleft
- Acetylcholine diffuses across celft and binds to receptors on the post synpatic membrane so sodium ions diffuse into post synpatic neurone when sodium ion channels open.
- If threshold reached, another AP is triggered.
29
Why are synpases unidirectional?
- Synapses only travel in one direction because receptors are only found on the post synaptic membrane
- Neurotransmitter is only made and released from pre synaptic neurone's side.
30
What is summation?
- Low frequency action potentials cause insufficient amounts of neurotransmitter to be released to trigger a new action potential.
Temporal - Presynaptic neurone connect to single postsynaptic neurones and releases neurotransmitter in timed intervals.
- Spatial summation is when lots of pre synaptic neurone bind to the post synaptic neurone and exceed the threshold value, triggering an action potential.
31
What is inhibition?
- When some synapses make it less likely for a new action potential to be triggered in the post synaptic neurone.
- Neurotransmitters may bind to chloride ions causing them to open and negative ions influx the post synaptic neurone
- May cause K+ channels to open so K+ diffuses out which lowers resting potential more negative
32
Neuromuscular junction structure
- Synpase between motor neurone and muscle fibre.
- Many neuromuscular junction along a muscle
- Acetylcholine used
33
Differences between cholinergic and neuromuscular..
Cholinergic:
- Neurone to neurone
- Motor sensory or relay
- Excitatory or inhibitory
- New AP is triggered
- Ach binds to receptors on post synaptic neurone
- Less receptors
Neuromuscular junction:
- Neurone to muscle
- Motor neurones only
- Excitatory only
- AP ends here
- Ach binds to the receptors on muscle fibres
34
Effects of drugs on synapses
- Some may have similar shapes to neurotransmitters which bind to receptors and cause more action potentials
- Act as blockers to prevent neurotransmitters from binding so fewer sodium ion channels open and fewer action potentials are triggered
- Inhibit enzyme breakdown and prevent neurotransmitters from being broken down. b
35
3 type of muscle
- Smooth
- Cardiac
- Skeletal
36
Antagonistic meaning
- When one contracts, other relaxes
37
Structure of skeletal muscle
- Muscle made of muscle fibres
- Muscle fibres are made up of organelles called myofibtrils
- Cytoplasm is called sarcoplasm
- Sarcolemma has folds called T-tubules which help spread electrical impulse
- Mitochondria
- Sarcoplasmic reticulum stores calcium ions needed for contraction.
38
Structure of myofibrils
- Bundles of thick and thin myofilaments that move past each other to make muscles contract
- Myofilaments are Myosin (thick) and Actin (thin)
39
What is the sarcomere?
- A single contractile unit
40
What are Z lines
- Ends of the sarcomere
41
What are A bands, I bands and H zones
- A bands are the length of the myosin
- I band contains actin only
- H zone contains myosin only
- M line is the middle of myosin
42
What shortens and stay the same length
- I band shortens when the thick filaments shortens as the thick and thin filaments slide past
- H zone shortens
- A band stay the same because the myosin filaments themselves do not shorten
- Myofilaments stay the same length because they themselves don't shorten.
43
How do myofibrils contract?
- Tropomyosin blocks myosin head from binding to the actin-myosin binding site so the myosin can't bind and myofilmanets can't slide past each other.
- Action potential reaches neuromuscular junction
- Acetylcholine diffuses over to the postsynaptic membrane and binds to receptors
- Depolarisation of the sarcolemma
- Wave of depolarisation spreads along T-tubules and sarcoplasmic reticulum.
- Calcium ions bind to troponin, causing it to change shape which pulls tropomyosin out of the actin myosin binding site.
- Myosin head binds to actin myosin binding site. (actinmyosin bridge)
- Calcium ions activate ATP hydrolase which hydrolyses an ATP that is bound to the myosin head
- Energy released causes the myosin head to bend which pulls actin filament along.
- ATP attaches to myosin head and hydrolyses to break the bridge and then another myosin heads binds to a different actin myosin binding site further along.
44
How to generate ATP?
- Aerobic respiration
- Anaerobic respiration (slower ATP production)
- ATP-Pcr system (Phosphocreatine provides an extra phosphate molecule for ATP synthesis)
- ADP+PCr - > ATP + Creatine
45
What is an issue with creatine?
- Small amounts so is used as short term energy.
46
Slow vs Fast Muscle Fibres
Slow:
- Works for long times without getting tired
- Long periods of low intensity
- Aerobic
- Thin in diameter, red in colour
- More widespread
Fast:
- Short periods of high intensity
- Anaerobic
- Thick in diameter but pale.
47
What is homeostasis?
- The use of physiological control systems that maintain the internal environment within restricted limits.
- Core temperature, blood glucose and blood pH are controlled.
- Enzymes are important in regulating and increasing the rate of metabolic reactions so need to be controlled.
48
Negative feedback outlined
- Restores systems to their original level
- Stimulus is a change to the internal environment
- Passed onto a receptor or coordinater
- Nerve impulses or hormones are sent out leading to the reversal of the change
49
How is the body prepared for all types of negative feedback?
- By having different negative feedback mechanisms meaning that can reverse the change in multiple directions from the norm. #
- More control due to quicker responses.
50
Positive feedback
- Increasing amplification from the norm
- Blood clotting platelets releasing chemicals to activate more platelets.
51
Factors that influence concentration of blood glucose
- Food intake, exercise and metabolic rate
(glucose)
(Exercise causes higher demand so does metabolism)
52
3 processes involved in blood glucose control?
- Glycogenesis - glucose converted into glycogen (insulin)
- Glycogenolysis - hydrolysis of glycogen into glucose (glucagon/adrenaline)
- Gluconeogenesis - conversion of non-carbohydrates into glucose
53
Role of the pancrease in blood glucose control
- Alpha (secrete glucagon by detecting low glucose)
- Beta cells (secrete insulin by detecting high levels of glucose)
54
Controlling blood glucose when too high/ too low?
- Insulin binds to specific receptors on CSM of target cells
- Glucose channel proteins change shape and open allowing more glucose to enter cells from the blood
- Triggers the fusion of channel-containing vesicles with the CSM of target cells, increasing number of glucose channel proteins in the membrane.
- Activation of enzymes involved in the formation of glycogen (glycogenesis)
LOW:
- Glucagon binds to specific receptors on the CSM of target cells
- Activates enzymes that convert glycogen into glucose (glycogenolysis)
- Activates enzymes that convert glycerol and amino acids into glucose (gluconeogenesis)
55
Second messanger model
- Glucagon/Adrenaline bind to receptors on CSM
- This activates Adenylate Cyclase enzyme which catalyses cAMP from ATP
- Protein kinase enzyme activates a chain of reaction (cascade effect) leading to glycogenolysis.
(amplifies the effects)
56
Type 1 vs Type 2
Type 1:
- Pancrease doesn't produce enough insulin
- Caused by an autoimmune disease that destroys b cells that produce insulin
- Thirst is a symptom
- So is excessive urination
- Weight loss as you respire lipids
- Treatment could be regular insulin injections.
Type 2:
- Pancreas stops responding to glucose
- Glycoprotein receptors on the CSM of target cells are less responsive to insluin
- Obesity
- Management of diet and exercise and losing weight are ways to treat type 2.
57
What is osmoregulation?
- Control of the water potential of the blood
58
3 steps of osmoregulation?
- Ultrafiltration - formation of glomerular filtrate
- Selective reabsorption - reabsorption of useful substances, such as glucose, amino acids, and ions
- Osmoregulation
59
How does ultrafiltration happen?
- Happens at glomerulus and bowman's capsule.
- Efferent arteriole's are smaller in diameter than the afferent arteriole so the hydrostatic pressure in the glomerular capillaries increases and small molecules are forced through a 3 layer filter into the bowman's capsule.
- 3 layer filter is made of collagen, endothelium, basement membrane and podocytes.
- RBCs don't pass through
- Glucose, water, amino acids, excess vitamins, urea pass through.
60
How does selective reabsorption happen?
- Useful substances such as glucose, amino acids and ions return.
- Pass back into blood capillaries wrapped around the PCT.
- Done by co-transport.
61
How does osmoregulation happen?
- At the loop of henle, medulla sees a loweringof water potential, so that water can be reabsorbed at the descending limb, the Distal Convoluted Tubule and collecting duct by osmosis.
- Top of the ascending limb, sodium ions pumped into medulla by active transport, the ascending limbs is impermeable to water so water remains in the tubule which lowers the WP of the medulla.
- Water moves out of the descending limb which is permeable to water by osmosis.
- Descending limb is not permeable to ions so the filtrate becomes more concentrated.
- Bottom of ascending limb - Sodium ions move into the medulla lowering WP of medulla even more.
- Water is reabsorbed by capillary system.
62
How much water is reabsorbed at the DCT and Collecting Duct
Low water potential in blood:
- Detected by osmoreceptors in hypothalamus
- Posterior pituitary gland stimulated to release more ADH into the blood.
- ADH binds to receptors on the cell membrane lining the distal convoluting tube and collecting duct.
- Triggers vesicles containing aquaporins to fuse with the cell surface membrane so more aquaporins are incorporated into the cell surface membrane of cells lining the DCT and collecting duct.
- More water leaves by osmosis
- Less water lost, urine concentrated.
63
High water potential?
- High water potential is detected by osmoreceptors in hypothalamus
- Posterior pituitary gland releases less ADH into blood
- Less ADH molecules bind to receptors in cell surface membrane of cells lining the DCT and collecting ducts so less aquaporins are incorporated into the cell surface membrane of cells lining these tubules.
- DCT and collecting duct less permeable to water so there are fewer places for water to leave by osmosis
- More water lost
- urine more dilute with water.
