Topic 6 Homeostasis Flashcards
1
Q
What is a stimulus
A
A detectable change in the environment
2
Q
What are receptors
A
Cells that detect a stimulus
3
Q
What is an example of a growth factor that controls Tropisms
A
Indoleacetic acid (IAA)
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
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
6
Q
Explain how phototropism occurs in the shoots
A
- Shoot tip cells produce IAA cashing cell elongation
- IAA diffuses to other cells
- If there is unilateral light IAA diffuses to words shaded side so that side elongates causing a bend
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
8
Q
Explain how gravitational works in the shoots
A
- IAA diffuses from upper side to lower side of shoot
- If plant is vertical causes plant to elongate and grow up
- I’d plant is horizontal causes shoot to bend up
This is negative gravitropism
9
Q
How does gravitropism work in the roots
A
- 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
10
Q
What are the 3 neurones that make up the reflex arc
A
Sensory neutone
Relay neurone
Motor neurone
11
Q
What is taxes
A
Organism moves it’s entire body to words favourable stimulus away from unfavourable
12
Q
What is kinesis
A
Organism changes speed of movement and the rate it changes direction
Returns to favourable conditions
13
Q
Where are the pacinican corpuscle found and what does it detect
A
Found mainly in fingers and feet and detects pressure
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
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
16
Q
Where are the receptors rods and cones found
A
In the human retina
17
Q
Give properties of rod cells (5)
A
- Rod like In shape
- Process images in black and white
- Use pigment rhodopsin
- Detect light at very low intensity
- Brain can’t distinguish between separate sources of light so you have low visual acuity (low clarity)
18
Q
What is retinal convergence
A
Many rod cells are connected to one sensory neurone
19
Q
Give the properties of cone cells
A
- Cone cells process images in colour
- 3 types that contain different types of iodopsin pigment
- High visual acuity - can distinguish between separate sources of light
20
Q
What are the 3 colours of cone cells
A
Red, green and blue
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
22
Q
Where are most of the cone cells located
A
In the fovea where the highest light intensity is
23
Q
Where are rod cells located
A
Further away from fovea as they don’t need as high light intensity
24
Q
Where is the SAN located and what is it
A
Sinoatrial node - pacemaker of heart found in right atrium
25
Where is the AVN located
Atrioventricular node - located near boarder of right and left ventricle within atria
26
Where is the bundle of his
Runs through septum
27
Where are the purkyne fibres
In the walls of hr ventricles
28
Explain the control of heart rate (5)
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
29
What controls your heart rate
Medulla oblongata via the autonomic nervous system
30
What are the 2 parts of the nervous system that are linked to control of heart rate
1. Sympathetic nervous system
2. Parasympathetic nervous system
31
What happens if more nerve impulses are sent down the sympathetic nervous system
SAN release waves of depolarisation more frequently causing increase in Heart rate
32
What happens if more nerve impulses are sent down the parasympathetic pathway
Causes SAN to release waves of depolarisation less frequently causing decrease in heart rate
33
What are the 2 stimuli that can change the heart rate
PH & blood pressure
34
What detects changes in PH
Chemoreceptors
35
What detects change in blood pressure
Pressure receptors/ baroreceptors
36
Where are the 2 receptors found
Aorta and carotid artery
37
How does your heart rate respond to a change in PH
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
38
How does your heart rate respond to blood pressure high & low
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
39
Give the structure of a myelinated neurone (4)
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
40
What is a resting potential
When a neurone is not conducting an impulse there is a difference between electrical charge inside and outside neurone
41
Explain the resting potential of axons
More positive sodium ions an potassium outside compared to inside so inside of neurone is more negative
42
How are resting potentials maintained
- 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
43
What is an action potential
When neurones voltage increases beyond a set pint from resting potential generating a nervous impulse
44
Explain an action potential (6)
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
45
What is the all or nothing principle
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
46
Explain why the refractory period is important (3)
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
47
What are the 3 factors that affect the speed of conduction
1. Myelination & saltatory conduction
2 axon diameter
3. Temperature
48
What is myelination
Action potential jumped from node to node (saltatory conduction) means action potentials travel faster long axon
49
How does the axon diameter affect speed of conductance
Wider diameter increases speed less leakage of ions
50
How does temperature affect speed of conductance
1. Ions diffuse faster (more kinetic energy)
2. Enzymes involved work faster in higher temps more ATP for active transport
51
What are synapses
The gaps between the neurones end of the axon and dendrite of another
52
Explain the function of a synapse (6)
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
5. Neurotransmitter is degraded and released from receptor Na+ channels close and post- synaptic neurone re restablishes resting potential
6. Neurotransmitter transported back into presynaptic neurone
53
How is the function of the synapse unidirectional
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
What is the name of the neurotransmitter for the cholinergic synapse
Acetylcholine
55
What is the enzyme that breaks down acetylcholine into choline and acetate
Acetylcholineesterase
56
What is summation
Rapid build up of neurotransmitters in the synapse to generate an action potential bye either spacial summation or temporal summation
57
What is spatial summation
Many different neurones collectively trigger a new action potential by combining with neurotransmitter they release to exceed threshold value
58
What is temporal summation
One neurone released neurotransmitter repeatedly over short period of time to add up to enough to exceed threshold value
59
What are inhibitory synapses
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
What is a neuromuscular junction
Synapse between motor neurone and a muscle
61
Give one similarity and 3 differences between neuromuscular junction and cholinergic synapse
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
What is the sarcoplasm
Myofibrils are made up of fused cells that share nuclei and cytoplasm
63
What are the sarcomere
Muscle fibres are made up of millions of myofibrils which collectively bring about the force to cause movement
64
What are the 2 key types of proteins that make up myofibrils
Myosin and actin
65
What does the A band of a muscle represent
The length of myosin which should never change
66
What does the H zone represent
The length of myosin that isn’t overlapping with actin
This will change when the muscle contracts so H zone will shorten
67
What does the I band represent
Actin by itself not overlapping with myosin
When muscle contracts it decreases as myosin is overlapping with actin
68
What do the Z lines represent
The start and end of the sarcomere
These get closer together when muscle contracts
69
What is the sliding filament theory
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
What is phosphorcreatine
A chemical stored in muscles assists sliding filament theory by providing phosphate to regenerate ATP from ADP
71
Give the structure location and general properties of slow twitch muscles
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
Give the structure, location and general properties of fast twitch fibres
Thicker contain more myosin filaments
Store of glycogen
I’m over in anaerobic respiration
Found in biceps
Contract faster
Adapted for intense exercise
73
What is homeostasis
Physiological control systems that maintain internal environment within restricted limits
74
What are the 2 main things that are important to maintain
Stable core temperature
Stable blood ph
75
What is negative feedback
If there is any deviation from the normal values are restored to their original level
76
How can your blood glucose concentration increase
Ingestion of food or drink containing carbohydrates
77
How can your blood glucose concentration decrease
Following exercise or if you haven’t eaten
78
What it the role of the pancreas in blood glucose concentration
Detects change in the blood glucose levels.
Islets of langerhans cells release insulin and glucagon to bring blood glucose levels back to normal
79
What is the role of insulin in the blood glucose concentration
Insulin is released when blood glucose levels are too high causes a decrease in blood glucose levels
80
What is the role of glucagon in blood glucose concentration
Released when blood glucose levels are too low
81
What is the role of Adrenalin in blood glucose concentration
Released by adrenal glands when body anticipates danger results in more glucose being released from hydrolysis of glycogen in the liver
82
Explain what happens if your blood glucose level increases
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
Explain what happens if your blood glucose levels decrease
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
How does insulin decrease blood glucose (3)
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
How does glucagon increase blood glucose (3)
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
What is the 2nd messenger model
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
How does adrenaline increase blood glucose (2)
1. Adrenaline attached to receptors on target cells
2. CAMP activated enzyme that hydrolysed glycogen into glucose
88
What is glycogenesis
Converting glucose into glycogen occurs in the liver and catalysed by enzymes there
89
What is glycogenolysis
Hydrolysis of glycogen to glucose occurs in liver due to secondary messenger model
90
What is gluconeogenisis
Creating new glucose from other molecules such as amino acids and glycerol in the liver
91
What is type 1 diabetes what is the treatment
Where your unable to produce insulin could be result of autoimmune disease
Treatment is insulin injections
92
What is type 2 diabetes how is it controlled
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
What is osmoregulation
Controlling water potential of the blood
94
What happens if blood has too low of a water potential
Becomes hypertonic
Too much water leaves cell and moves into blood by osmosis cells shrivel
95
What happens if the blood has too high a water potential
Hypotonic
Too much water moves from blood into cell causing cell to burst (lysis)
96
What causes hypertonic blood (shrivelled)
- too much sweating
- not drinking enough water
- lots of ions in diet e.g salt
97
What is the corrective method for hypertonic blood
More water reabsorbed by osmosis into blood from tubules of the nephrons
Urine is more concentrated as less water is lost in urine
98
What happens if someone has hypotonic blood
- drinking too much water
- not enough salt in diet
99
What is the corrective mechanism for hypotonic blood
Less water reabsorbed by osmosis into blood from tubules of the nephron
Urine is more diluted as more water lost in urine
100
Where does osmoregulation occur
Within nephrons in kidney
101
What are the nephrons
Long tubules surrounded by capillaries and there are 1 million per kidney
102
What is the purpose of the nephrons
Blood filtered here to remove waste and selectively reabsorb useful substances back into the blood
103
What is the glomerulus
Filters small solutes from the blood
104
What is the PcT
Proximal convoluted tubule - reabsorbs ions, water and nutrients removed toxins
105
What is the descending loop of Henle
Aquaporins allow water to pass from filtrate into interstitial fluid
106
What is the ascending loop of henle
Reabsorbs sodium and chlorine ions from filtrate into the interstitial fluid
107
What is the distal tubule
Selectively secretes and absorbs different ions maintain blood ph
108
What is the collecting duct
Reabsorbs solutes and water from filtrate
109
Explain filtration and reabsorption in the kidneys
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
What is the hypothalamus
Changes in the water potential of the blood detected by osmoreceptors
111
What happens if the water potential of blood is too low
Water leaves the osmoreceptors by osmosis and shrivel stimulating the hypothalamus to produce more hormone ADH
112
What happens if water potential of blood is too high
Water enters the osmoreceptors by osmosis and stimulated hypothalamus to produce less ADH
113
Where is ADH produced
Hypothalamus
114
Where does ADH move to
Posterior pituitary
115
What does ADH stand for
Antidiuretic hormone
116
What does ADH do
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
