Organisms respond to changes in their internal and external environments 6 Flashcards
(89 cards)
1
Q
What is a taxes
A
Movement of a motile organism in response to a stimulus (usually an environmental change)
2
Q
What is a positive taxis
A
organism moves towards a stimulus (usually favourable)
3
Q
What is a negative taxis
A
organism moves away from a stimulus (usually unfavourable)
4
Q
What is the purpose of a taxis
A
Increases chances of the organism’s’ survival in all cases
5
Q
What is kineses
A
A form of response in which the motile organism does not move towards/away from a stimulus, but instead shows a random, non-directional response (eg. the organism changes the speed at which it is moving and the rate at which it changes direction in response to a stimulus)
6
Q
What is a tropism
A
The growth of plants in response to a directional stimulus
e.g. The plant grows towards (positive response) or away (negative response) from a stimulus
7
Q
What is the kinesis for water
A
hydrotropism (positive in roots)
8
Q
What is the kinesis for gravity
A
gravitropism (positive in roots, negative in shoots)
9
Q
What is the kinesis for light
A
phototropism (positive in shoots, negative in roots)
10
Q
What is a reflex arc
A
a completely involuntary and instantaneous movement in response to a stimuli
11
Q
Describe the structure of a myelinated motor neurone
A
- dentrites/dendrones
- cell body
- nucleus
- axon
- myelinated sheath
- schwann cells
- nodes of ranvier
- axon terminals
12
Q
Definition of the nervous system
A
a system that uses nerves to pass electrical impulses to communicate
13
Q
Definition of the hormonal system
A
a system that produces chemicals that are transported in the blood to their target cells (via receptors) to communicate
14
Q
Differences between the nervous and hormonal systems
A
NERVOUS SYSTEM
- short-lived
- transmission by neurones
- very rapid acting
- usually temporary and reversible
- muscles
HORMONAL SYSTEM
- long lasting
- transmission by blood stream
- relatively slow
- may be permanent and irreversible
- glands
15
Q
How does phototropism work in plants
A
SHOOTS
IAA moves to the shaded side of stem, causes elongation of cells here, so the plant will bend towards the unidirectional light
this is positive phototropism
ROOTS
IAA moves to the shaded side of the stem, but inhibits the elongation of cells, so the roots bend away from the unidirectional light
this is negative phototropism
16
Q
How does gravitropism work in plants
A
IAA moves to the underside of shoots and roots and either inhibits or stimulates growth, causing the plant to bend against/with gravity
In shoots, there is negative gravitropism and in roots there is positive gravitropism
17
Q
What is the nervous system made up of
A
receptors
sensory neurones
CNS and relay/intermediate neurone
motor neurone
effectors
18
Q
What is smooth muscle
A
muscle that contracts without conscious control, found within walls of internal organs
19
Q
What is cardiac muscle
A
muscle that contracts without conscious control but only found in the heart
20
Q
What is skeletal muscle
A
muscle that we use to move limbs and ourselves
21
Q
What are antagonistic pairs of muscles
A
Muscles that move a bone together, where one contracts (agonist) and the other relaxes (antagonist).
Examples are our triceps and biceps
22
Q
What are the features of a neurone
A
Cell body
Nucleus
Schwann cells
dendrones/dendrites
axon
nodes of ranvier
axon terminals
axoplasm
23
Q
What is an action potential
A
A nerve impulse is an action potential that moves along a neurone in one direction
24
Q
What ensures that the action potential only travels in one direction along a neurone
A
The section behind the action potential is repolarising
The refractory period is where a neurone cannot be stimulated anymore and has to wait to be stimulated again
the voltage gated Na+ channels are closed and will not open. In addition, the voltage gated K+ channels are open.
25
Describe what happens during an action potential
A stimulus arrives and disturbs the resting membrane potential (of -70mV), causing voltage-gated Na+ channels to open.
Na+ rushes into the axoplasm by diffusion, down its concentration/electrochemical gradient, causing the membrane to depolarise (the inside now becomes more positively charged than the outside).
When the membrane potential reaches +40mV the voltage-gated Na+ channels close and the voltage-gated K+ channels open.
K+ rushes out of the axon into the surrounding tissue fluid by diffusion, causing the membrane to repolarise (becoming more negatively charged on the inside again compared to the outside).
The membrane potential overshoots the resting membrane potential to lower than -70mV (e.g. -80mV) -> hyperpolarises
At this point, the voltage-gated K+ channels close.
The Na+/K+ pump then restores the membrane back to the normal resting membrane potential of -70mV.
26
What is a nerve impulse
an action potential that moves/spreads along a neuron in one direction
27
Can you explain the meaning of the all-or-nothing principle
- A specific level (strength) of stimulus is required to meet the threshold value to trigger an action potential
- If a stimulus is too small that the threshold is not met, an AP will not be generated
- All APs are more or less the same size - a bigger stimulus will not generate a bigger AP
28
What is the relationship between size of stimulus and action potential
The larger the stimulus, the higher the frequency of Action potentials that pass along the neuron in a given time
29
What makes it so the action potentials travel faster along a myelinated neurone opposed to an unmyelinated neurone
Saltatory conduction in myelinated neurones is faster - action potentials only occur at the Nodes of Ranvier
30
Factors affecting the speed of conduction of an action potential in a nerve
- axon diameter
- myelination
- temperature
31
What does the pacinian corpuscle respond to
pressure
32
What is the pacinian corpuscle structure
Layers of connective tissue with a viscous gel inbetween layers
the end of a nerve ending
Strech mediated Na+ channels
33
Describe how a Pacinian Corpuscle produces a generator potential when stimulated (3 marks).
Increased pressure deforms/changes stretch mediated sodium channel.
sodium channels open and sodium ions flow in.
which cause depolarization which leads to generator potential.
34
What is a generator potential
The initial depolarisation (diffusion of Na+ ions into the axon), which may or may not reach the threshold at the first node of ranvier and therefore may or may not trigger an action potential
35
What is a synapse
the point/junction where one neurone connects/joins with another neurone or with an effector
36
Outline the structure of a synapse
Pre synaptic Knob
- synaptic vesicles
- neurotransmitters
- Ca2+ VGC
- Pre synaptic membrane
- synaptic cleft
Post synaptic Knob
- proteins receptors
- post synaptic membrane
37
What are the two kinds of synapses and give the examples of each
excitatory (releases acetylcholine) and inhibitory (releases GABA)
38
Synapses are unidirectional. What does this mean
the impulse travels in one direction only
39
How is temporal summation created at a synapse
A single presynaptic neurone releases neurotransmitter many times over a short period of time due to a high frequency of action potentials travelling along the presynaptic neurone. This results in the release of enough neurotransmitter to reach the threshold and trigger an action potential on the postsynaptic neurone.
40
How is spatial summation created at a synapse
Multiple presynaptic neurones together release enough neurotransmitter to reach the threshold and trigger an action potential on the postsynaptic neurone (however, on their own they did not release sufficient)
41
what is the arrangement of cells in the retina
ganglion cells (optic nerve), bipolar cells and the cones/rods
42
Compare and contrast cone and rod cells
Cone
- responds to high light intensity
- contains pigment called iodopsin
- used to see coloured light
- has good visual acuity
- each cone synapse connects to one bipolar cell
Rod
- responds to low light intensity
- contains pigment called rhodopsin
- used to see black and white
- has low visual acuity
- 3 rod cells have a synapse to one bipolar cell (spatial summation)
43
Where are cone cells distributed on the retina
concentrated at the fovea
44
Where are rod cells distributed on the retina
the periphery of the fovea
45
What is visual acuity
The ability to tell apart two points that are close together.
46
Why is visual acuity different in cone and rod cells
Cone cells only connect to one other neuron, so each individual stimuli can be distinguished.
Rod cells connect in 3's to one bipolar cell, and so the different polarisations of light get merged
47
Heart muscles are myogenic. What does this mean?
The muscles contracts by itself rather than a nerve.
48
The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricualr node (AVN). Describe how.
5 marks
SAN is myogenic and acts as a pacemaker.
The SAN depolarises and send a wave of electrical excitation over the atria, causing them to contract (atrial systole)
There is a brief delay where the electrcial impulse travels over nonconductive tissues and the AVN, allowing the atria to fully empty and the ventricles to fill up fully.
The electrical wave of excitation travels down the Bundle of His and towards to apex of the heart, where it spreads up the purkyne fibres.
This causes the ventricles to contract (ventricular systole)
After this, the atria and ventricular muscles relax and fill up passively with blood (atrial and ventricular diastole)
49
What is the voluntary nervous system
the control system associated with the voluntary control of muscles
50
What is the autonomic nervous system
the involuntary movement of muscles in response to a stimulus
51
What are the two sides of the autonomic nervous system and what are they
Parasympathetic division
- these motor neurones have a suppressive effect on effectors -> involved in conserving energy
Sympathetic division
- these motor neurones have a stimulatory effect on effectors
52
What is the definition of homeostasis?
The maintenance of more or less constant internal environments in organisms
53
Explain the formation of tissue fluid
- higher osmotic pressure at the arteriole end, lower at the venule
- higher hydrostatic pressure at arteriole end, lower at the venule
- higher water potential at the arteriole end than the venule
- both of these pressures (osmotic and hydrostatic) force fluid from the bloodstream to move to the tissue cells surrounding the blood vessel
- because the blood has a higher X than the surrounding tissue
- RBCs WBCs plasma proteins all remain in the blood
- so as a result, water potential in the blood vessel decreases below the water potential of the surrounding tissue, so fluid enters back in at the venule end down its pressure/water potential gradient
- 10% of tissue fluid does not make it to the blood vessel, and therefore is removed by the lymphatic system as lymph
54
Where does the exchange of blood and tissue occur?
capillaries
55
What are the features of capillaries that make them perfect for exchange between blood and tissue
- one cell thick, so short diffusion pathway
- have pores (fenestrae) that allow water to move out more easily
- the small diameter only allows one RBC to fit through at a time, so direct diffusion
56
What is the importance of homeostasis?
provides organisms with the ability to maintain a constant internal environment to withstand greater changes in the external environment, allowing them to survive a greater range of habitats
57
What is the importance of homeostasis specifically, think enzymes, water potential and glucose
Enzymes are sensitive to changes in temperature & pH and are essential for all the chemical reactions inside cells (metabolism).
Blood glucose needs to be high enough to supply cells with respiratory substrate. Too much glucose in the the blood lowers its water potential.
Changes in water potential would cause cells to shrink or swell and affect their function. Therefore solute concentrations need to be maintained.
58
What is negative feedback
when the output from the system counteracts/opposes the input and so turns the system off because the body is brought back to the set point
59
How does maintaining a constant body temperature allow metabolic reactions in cells to proceed with maximum efficiency?
5 marks
1. Body temp. / 37 °C is optimum temp for enzymes;
2. excess heat denatures enzymes / alters tertiary structure / alters shape of active site / enzyme so substrate cannot bind / eq;
3. reactions cease / slowed;
4. too little reduces kinetic energy of molecules / molecules move more slowly;
5. fewer collisions / fewer ES complexes formed’
60
What happens during thermoregulation, include both extremes
notes.
61
What is the main store of glucose in animals, and what are the structural relations to its function
- glycogen
- highly coiled, so compacts and a lot can fit into a small space
- highly branched, so more ends/surface area for hydrolysis of the molecule to release glucose more rapidly, and so it is more readily available for respiration
- doesn't affect water potential within a cell, so won't force water out of the cell
62
What does each of the following do to glucose levels in the blood?
- glucagon
- insulin
- adrenaline
explain how SPECIFIC TERMINOLOGY
- glucagon
increases blood glucose concentrations when they are two low, by causing glycogenolysis in the liver, where glycogen is hydrolysed and stimulating the liver to release glucose into the blood
- insulin
decreases blood glucose concentration when they are too high, by causing glycogenesis in the liver, where the liver is stimulated to absorb glucose and condense it into glycogen as a store
- adrenaline
increases blood glucose concentrations REGARDLESS of whether they are too high, normal or too low, to make glucose readily available for a predicted increase of respiration rates due to flight or fight activation
63
Where are glucagon and insulin released and by what
In the endocrine cells called ISLETS OF LANGERHANS, in the pancreas
Glucagon is released by alpha cells
Insulin is released by beta cells
64
What is an endotherm?
What is an ectotherm?
endotherms are organisms where their body temperature is controlled within themselves (metabolic activities)
ectotherms are organisms where their body temperature is controlled externally, and so they obtain their heat from environmental sources
65
What are some symptoms of diabetes
- High blood glucose concentration
- Presence of glucose in urine due to high concentration in the blood
- Need to wee excessively (body trying to get rid of excess blood glucose)!
- Weight loss
- Increased thirst and hunger
66
What causes type I diabetes
- genetic, where no insulin is produced
- beta cells are destroyed
- so NO insulin is produced
- it can also be from an autoimmune response where the immune system has attacked the B cells in the Islets of Langerhans
67
What causes type II diabetes
- the pancreas still produces insulin but the body becomes ‘resistant’ to/ loses responsiveness to insulin
- Can result from a loss of (fewer) insulin protein receptors on body cells or receptors no longer respond to insulin
- therefore less glucose taken up into cells
68
What is diabetes?
A metabolic disorder caused by the inability to control blood glucose concentrations by homeostasis either due to the complete lack of the hormone insulin (produced by the beta cells of the pancreas) or a loss of responsiveness to insulin.
69
Outline the second messenger model
- glucagon/adrenaline binds to their protein receptors on liver/muscle cells
- this changes the tertiary structure, which in turn activates adenylate cyclase
- adenylate cyclase causes ATP to convert into cAMP
- cAMP acts as the 2nd messenger, and activates (switches on) protein kinase
- protein kinase is an enzyme that catalyses the hydrolysis of glycogen into glucose
70
Describe how the regular contraction of the atria and ventricles is initiated and coordinated by the heart itself. (5)
- the sinoatrial node depolarises which causes a wave of electrical excitation to be sent over the atria , causing them to contract
- the heart is myogenic, meaning it causes itself to contract
- there is a brief delay as the wave of electrical excitation passes over nonconducting tissue, and reaches the atrioventricular node
- this allows the atria to fully empty of blood, and allows the ventricles to fully fill up
- the wave of electrical excitation travels down the Bundle of His/ the septum of the heart towards to apex, and then up the purkyne fibres from the apex up the sides of the ventricles
- this cause the ventricles to contract
71
Describe the sliding filament theory
- myosin head with ADP attached forms cross birdges with actin
- power stroke occurs, where the myosin head changes shape and loses ADP, pullin gactin over myosin
- ATP attaches to the myosin head, causing it to detach from actin
- ATPae hydrolyses ATP --> ADP, so the myosin head can return to original position (like cocking a gun)
- myosin head re-attaches to actin to further along the filament
72
describe the structure of a skeletal muscle
make up of muscle fibre bundles
which are long cylindrical cells containing several nuclei
each muscle fibre is made up of myofibrils
myofibrils are responsible for the visibility of h bands, I bands and A bands
73
insulin
where is it made
what is it made of
when is it released into the blood
where are its target cells
- beta cells of the islets of Langerhans in the pancreas
- protein
- when the beta cells of the islets of Langerhans detect that blood glucose concentration is too high
- mainly the liver and skeletal muscles
74
what happens when insulin binds to its target cells (in the liver and skeletal muscle)
- insulin binds to target cells on the cell surface membrane
- vesicles with embedded glucose carrier proteins fuse with the cell surface membrane
- the increased number of glucose carrier proteins in the CSM allows more glucose to enter the cell via facillitated diffusion
- the activation of insulin receptors also activates enzymes that convert glucose to glycogen
75
Glucagon
Where is it made
whats it made of
when is it released into the blood
where does it act
- alpha cells in the islets of Langerhans in the pancreas
- protein
- when alpha cells in the islets of Langerhans detect that blood glucose levels are too low
- only on the liver
76
what happens when glucagon binds to its target cells (in the liver)
- glucagon binds to its receptors on the CSM of its target cells
- the liver cells respond by activating enzymes involved with converting glycogen back to glucose, and converting glycerol or amino acids to glucose
- glucose then diffuses out of the target cell back into the blood
77
adrenaline
where is it produced
when is it released
where are its target cells
- adrenal glands above the kidneys
- in response to stress, excitement, fight or flight
- liver and skeletal muscles
78
how do target cells react when adrenaline binds to them
they activate enzymes that convert glycogen back into glucose
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what is the difference between adrenaline and glucagon in terms of blood glucose regulation
- glucagon increase the blood glucose concentration whenever the conc is too low
- adrenaline causes the release of glucose into the blood in stressful situations, and this glucose can then be respired in tissue cells for more ATP
80
outline the structure of a myofibril
Z lines - the boundary between two sarcomeres
I bands - only actin
A bands - a bit of both -> actin and myosin
H zone - only myosin
81
explain the role of Ca2+ ions in muscle contraction
- Ca2+ diffuses into the sarcoplasm when Ca2+ voltage gated protein channels open
- Ca2+ binds to troponin, causing tropomyosin to shift
- this exposes binding sites on the actin filaments
82
how does the sliding filament action cause a myofibril to shorten
- actin filaments are pulled towards each other
- because myosin heads flex in opposite directions
- so the distance between adjacent sarcomere Z lines shorten
83
what do we observe on a microscope when a sliding filament action occurs
- H zone narrows
- I bands get narrower
- Z bands get closer together
- A zone remains the same
84
where are fast twitch and slow twitch muscles found in the body
Slow twitch - sites of sustained contraction --> calf muscle
Fast twitch - sites of short term contraction --> biceps
85
explain the structure and properties of slow twitch muscles
- high glycogen store: many terminal ends can be hydrolysed to release glucose for respiration
- contains myoglobin: higher affinity for oxygen than haemoglobin at Lower partial pressures
- many mitochondria: so aerobic respiration can occur, producing ATP
- surrounded by blood vessels: to maintain a high supply of oxygen and glucose at the respiring cells
86
Explain the structure and properties of fast twitch muscles
- more myosin filaments
- thicker myosin filaments
- high conc of enzymes involved in anaerobic repsiration
87
following the release of acetylcholine into the neuromuscular junction, a muscle contraction occurs.
Describe the sequence of events, following the release of acetylcholine that leads to stimulation of this contraction.
Do not include in your answer the events following the release of calcium ions in the myofibril
- acetyl choline diffuses across synaptic cleft
- acetylcholine attaches to protein receptors on sarcolemma
- sodium ions then enter through sodium voltage gated channel proteins, leading to depolarisation of the sarcolemma
- calcium ions are then released by the sarcoplasmic reticulum
88
inhibitory synapses cause hyperpolarisation in postsynaptic neurones.
explain how this inhibits synaptic transmission
the inside of the post synaptic neurone is more negative
so more sodium ions are required to enter to reach depolarisation
89
