Survival, Response, Nervous System Flashcards
1
Q
External stimuli
A
Temperature
pH
Pressure
Humidity
2
Q
Internal stimuli
A
Change in pH
Blood glucose concentration
Blood water potential
3
Q
Why do woodlice spend more time in humid areas
A
Likelihood of dessicated is less
Due to their relatively large SA:VOL
And open gas exchange surface
And no waxy waterproof cuticle on exoskeleton
4
Q
What are gibberellins
A
Growth factors
Stimulate flowering and seed germination
Growth of stem and flowering of plant
5
Q
Threshold
A
Minimum intensity required to result in an action potential
6
Q
Why aren’t neurones myelinated
A
They are so short and small that they only carry an impulse over short distances
7
Q
What are neutotransmitters
A
Chemical transmitters that diffuse across synaptic clefts from the pre synaptic neurones membrane where they are synthesised to the post synaptic neurones membrane
Binding to the complementary receptor on the post synaptic membrane
8
Q
Where is acetylcholine used
A
Parasympathetic branch of autonomic nervous system
Cholinergic synapse
Neuromuscular synapse
9
Q
What is the maximum frequency of action potentials limited by
A
Refractory period length
10
Q
Frequency of action potentials is related to what
A
Intensity of stimulus
11
Q
Stimulus reaction pathway
A
Stimulus Receptor Sensory neurone Coordinator Inter neurone/relay Coordinator Motor neurone Effector Response
12
Q
Stimulus
A
Detectable change in the internal or external environment of an organism
That produces a response
To keep optimum conditions for survival
13
Q
Instinctive behaviour
A
Inate responses to stimuli
Genetically determined so not learned
14
Q
Examples of instinctive behaviour
A
Kinesis
Taxis
Reflex arc
15
Q
What is a reflex
A
An innate response to stimuli
Producing a specific short lived response
16
Q
What is kinesis
A
Random locomotion of whole organism in response to a stimulus
Inate
AKA rate of change of movement
17
Q
Kinesis in woodlice
A
Move around more (speed and rate of turning) in low humidity
Rate of movement related to intensity of stimulus
Random movements (not directional)
Don’t move along a gradient of humidity
Just more likely to reach Hugh humidity by chance
Adaptive response
18
Q
How do you investigate kinesis
A
Choice chamber
19
Q
What is taxis
A
Directional locomotion of whole organism
Either towards
Or away
From a stimulus
20
Q
Two types of taxis
A
Positive taxis (towards stimulus) Negative taxis (away from stimulus)
21
Q
Examples of taxis
A
Phototaxis (light)
Aerotaxis (air)
Chemotaxis (chemical)
22
Q
Explain taxis in earthworms
A
Negative phototaxis Away from light Increases chance of survival in soil More likely to find food More likely to avoid predators Less likely to dehydrate
23
Q
Similarities between taxis and kinesis
A
Both involve locomotion of whole organism in response to a stimulus
Both inate
24
Q
Taxis vs kinesis
A
Taxis is directional movement whereas kinesis is random
Taxis is a response towards or away from a stimulus whereas kinesis is a change in rate of movement
25
What is a tropism
Growth movement
Of part of a plant
In response to a directional stimulus
Towards or away
26
Two types of tropism
Positive (towards)
| Negative (away)
27
Examples of tropisms
Phototropism (light)
Geotropism (gravity)
Halotropism (salt)
Hydrotropism (water)
28
What are growth factots
Synthesised in cells throughout plants
Diffuse through tissue
In response to a stimulus
Stimulating or inhibiting growth in the tissue that produced it
29
Growth factor vs hormone
Growth factors affect the tissue that released them
| Hormones affect a distant target organ
30
Growth factor vs nervous system
Growth factors effect is a lot slower than an electrical impulse
Electrical impulse can travel all over whereas growth factor is localised
31
What are auxins
Growth factors that cause shoot growth by cell elongation
Cell wall becomes loose and cells get longer
Moves through plant tissue and brings about tropisms
Due to uneven distribution of auxin in growing region
Causing uneven growth
32
IAA
Indoleacetic Acid
Plant growth factor
Synthesised in shoots and roots
Diffusing into growing regions
33
IAA in shoots
Synthesised in the shoot tips
Diffuses into growing region
Light causes movement of IAA from light to shaded side
Proportionally more IAA on shaded side
Causing directional growth
Promoting elongation on shaded side
Uneven growth as shoot bends towards light
Positive phototropism
34
IAA in roots
```
IAA synthesised in roots
IAA diffuses into growing region
IAA moves towards underside/shaded side
Inhibits elongation
Proportionally IAA on underside
Directional uneven growth down into the soil
```
35
How does the nervous system work
Detection of stimuli by receptors
Transmission of nerve impulses by neurones
Response by effectors
36
What is the nervous system
Nervous system provides a rapid response to stimuli
| Involving nerve transmission along neurones and chemical transmission across synapses between neurones
37
Endocrine vs nervous system
Endocrine system involves hormones for communication whereas nervous system has neurotransmitters
Endocrine system has a slower, longer lasting response than the nervous system
38
What does the nervous system consist of
Central nervous system (brain and spinal cord)
Peripheral nervous system (nerves originating from brain and spinal cord)
Autonomic (involuntary/subconscious)
Voluntary (voluntary conscious control)
39
What are neurones
Specialised cells adapted to their function
| Which is to carry electrical impulses from one part of the body to another
40
Types of neurones
Sensory neurone (receptor to CNS)
Inter (relay or bipolar neurone)
Motor (CNS to effector)
41
Features of a motor neurone
```
Dendrites
Nucleus
Cell body
Schwann cells
Myelin sheath
Nodes of Ranvier
Terminal end branch
Axon
```
42
Dendrites
Many thin extensions projecting out from the cell body
Carry electrical impulses towards cell body
Recieve impulses from other nerve cells
43
Cell body function
```
Soma
Contains organelles like RER, 80s ribosomes
For protein synthesis
To synthesise neurotransmitters
Contains nucleus
```
44
Schwann cells
```
Synthesise myelin (lipid)
Which insulates the axon
```
45
Myelin
```
Lipid
Synthesised by schwann cells
Insulating electrical impulses along axon to allow for saltatory conduction
Increasing the speed of transmission
Provides protection
```
46
Nodes of Ranvier
Gaps between schwann cells
Where myelin sheath is absent
And saltatory conduction can occur
47
Axon
Carries nerve impulses away from cell body
48
Terminal end branches
Connect neurone to effector
49
What is resting potential
At rest there is a potential difference
Of -70mV across axon membrane
Due to the outside of the membrane being slightly more positive
Higher concentration of positive Na+ ions outside neurone
Higher concentration of K+ inside neurone so diffuse out through leaky potassium ion Channel proteins
Remains polarised until stimulus of threshold potential
50
How is a resting potential established
Sodium potassium pump actively transports 3 Na+ out of axon and 2 K+ into axon
Using energy from ATP hydrolysis
K+ diffuses out if axon by potassium channel protein down a concentration gradient
Making the inside more negative than outside of the membrane
51
Synoptic links
Na+/K+ pump for active transport
Many mitochondria in neurones to synthesise ATP
Channel proteins involved in facilitated diffusion of ions
Proteins are specific shapes and structures
52
All or nothing principle
If a stimuluses intensity is below threshold there is no action potential
Anything at threshold or above generates a full sized action potential
Regardless of increase in stimulus (only affects frequency)
53
Depolarisation
Stimulus (-50mV) opens voltage gated Na+ channel proteins
Na+ ions diffuse into cell down concentration gradient
Via facilitated diffusion
Higher concentration of positive Na+ ions inside the cell makes the inside relatively more positive than outside
54
Repolarisation
```
+40mV action potential reached
Causing Na+ channel proteins to close
K+ channel proteins to open
K+ rapidly diffuses out
Down a concentration gradient
Making the inside more negative again
```
55
Hyperpolerisation
Potassium channels remain open longer than needed
To reach resting potential
Making the inside even more negative
Sodium potassium pump restores the resting potential of -70mV once -80/-90mV reached
56
Action potential
Period of inexcitability
| Following the transmission of an impulse
57
What is the refractory period determined by
The short time taken to return the membrane to resting potential
58
Advantage of refractory period
Prevents overstumulation
Which would waste valuable ATP
Lead to neurone death
59
What is a nerve impulse
Movement/propagation of an action potential along a neurone
Action potential acts as stimulus to adjacent polarised areas of membrane
Causing action potential to be passed along
60
What affects the rate of nerve transmission
Temperature
Axon diameter
Myelin sheath and saltatory conduction
61
Explain myelination and saltatory conduction
Impulse travels by jumping from one node of ranvier to the next
Occurs because myelin sheath insulates the axon so depolarisation can only occur at the nodes where there are gaps/myelination absent/axon membrane is exposed
Pumps and channel proteins only found at the nodes
Electrocurrents produced depolarises next node
And impulse jumps from 1 to next
Increasing the rate of transmission
Because depolarisation can only occur at the nodes so less of the neurone needs to be depolarised
Sodium diffuses between nodes
62
How does temperature affect nerve transmission
Higher temperature means greater kinetic energy
Increasing the rate of diffusion of ions
Which increases the rate of conduction of ions
63
How does axon diameter affect rate of nerves transmission
Larger diameter means larger membrane surface area
Increasing number of channel proteins
Increases the rate of diffusion and hence conduction
64
Why are impulses described as unidirectional
Only go one way
| From pre-synaptic neurone membrane to post-synaptic neurone membrane
65
How do you identify pre and post synaptic neurones
Vesicles containing neurotransmitters only produced in pre-synaptic neurone
Neurotransmitter receptor proteins only to on post-synaptic neurone membrane
66
Why are synapses needed
Electrical impulses can't jump the gap between neurones
| Impulses transmitted between neurones across a synapse using chemical messengers called neurotransmitters
67
What is ACh
Acetylcholine
Neurotransmitter involved in the parasympathetic branch of the autonomic nervous system and cholinergic synapses
Diffuses from the pre-synaptoc neurone membrane to the post-synaptic neurone membrane
Bind to their complementary receptors on post-synaptic membrane
68
How does the synapse work
1. Action potential arrives at synaptic knob
2. Causing voltage gated calcium ion channels in the pre-synaptic membrane to open
3. Calcium ions diffuse into synaptic knob by facilitated diffusion since there is a higher concentration in the synaptic cleft
4. Calcium ions activate enzymes that cause synaptic vesicles to move towards the pre-synaptic membrane
5. Vesicles fuse with the pre-synaptic membrane and release ACh via exocytosis
6. ACh diffuses down a concentration gradient and binds to specific ACh receptors on post-synaptic membrane
7. Opening sodium ion channel proteins so sodium ions diffuse in
8. If membrane reaches threshold potential then it depolarises the membrane and an action potential created
9. Spreading along axon of post synaptic neurone
10. Acetylcholinesterase hydrolysed ACh into choline and ethanic acid
11. Which diffuse back across synaptic cleft and across the pre-synaptic neurone membrane
12. ATP synthesised in mitochondria used to resynthesise ACh which is then stored in vesicles
69
Pros of synapse
Prevents impulse going in the wrong direction
Filters out low level stimuli so if threshold isn't reached at post synaptic neurone membrane no action potential generated
Preventing overstimulation
And a waste of valuable ATP
70
Cons of synapse
Delays impulse slightly
71
How does a neuromuscular junction work
1. Action potential arrives at synaptic knob
2. Causing voltage gated calcium ion channels in the pre-synaptic membrane to open
3. Calcium ions diffuse into synaptic knob by facilitated diffusion since there is a higher concentration in the synaptic cleft
4. Calcium ions activate enzymes that cause synaptic vesicles to move towards the pre-synaptic membrane
5. Vesicles fuse with the pre-synaptic membrane and release ACh via exocytosis
6. ACh diffuses down a concentration gradient and binds to specific ACh receptors on post-synaptic membrane
7. Opening sodium ion channel proteins so sodium ions diffuse in
8. If membrane reaches threshold potential then it depolarises the membrane and an action potential created
9. Spreading along axon of post synaptic neurone and propagated along length of muscle fibre
10. Acetylcholinesterase hydrolysed ACh into choline and ethanic acid
11. Which diffuse back across synaptic cleft and across the pre-synaptic neurone membrane
12. ATP synthesised in mitochondria used to resynthesise ACh which is then stored in vesicles
72
What is a neuromuscular junction
Synapse between motor neurone and muscle cell
Using acetylcholine neurotransmitter
Which binds to nicotinic cholinergic receptors
73
Differences between cholinergic synapse and neuromuscular junction
Receptors: Neuromuscular post synaptic membrane has more
Acetylcholinesterase: Neuromuscular post synaptic membrane folds to form lots of clefts that increase the surface area for more embedded enzyme
Response: When a motor neurone fires an action potential along response is always triggered in muscle cell but not the case for cholinergic synapses
74
What are cholinergic synapses
Most synapses are cholinergic
Meaning they use acetylcholine as the neurotransmitter
Acetylcholine is the most abundant neurotransmitter
75
How is the potential across membrane reversed when an action potential is produced
Sodium channel proteins close at +40mV
Potassium channel proteins open
Potassium ions diffuse out of the axon down a concentration gradient
Sodium/Potassium pump helps restore the ion distribution
76
How does myelination affect nerve impulses
Impulse jumps from node to node
Depolarisation only at node
Since sodium ion/potassium ion diffusion can only occur where there is no myelin sheath at the nodes of ranvier
So action potential only occurs here
Fewer jumps/depolarisations to reach the length of the axon
77
What is summation
Build up of neurotransmitter within the synapse
78
Temporal summation
Different neurones converge at a single synapse
Action potential arrives from a number of different neurones
Occurring over the same time period
Causing the release of enough neurotransmitter to cause an action potential in the post synaptic neurone
May be a mixture of inhibitory and excitatory neurotransmitter
79
Spatial summation
One pre synaptic neurone but impulses arrive in rapid succession
Giving a cumulative effect which is sufficient to depolarise the post synaptic neurone
Causing the release of enough neurotransmitter to cause an action potential in the post synaptic neurone
80
What is fatigue
Rate of transmitter released is higher than the rate at which it is reformed
Pre synaptic neurone can't release enough neurotransmitter to generate an action potential in post synaptic neurone until its regenerated
81
What are excitatory neurotransmitters
Cause an action potential in the post synaptic neurone
By making the resting potential inside neurone less negative than the outside
So less sodium ions needed to reach threshold
82
What are inhibitory neurotransmitters
Affect a different receptor on the post synaptic membrane
Resting potential becomes hyperpolarised/more negative
Post synaptic membrane less likely to reach threshold potential and generate an action potential
83
2 ways drugs can affect synapses
Excitatory effect
| Inhibitory effect
84
How can drugs have an excitatory effect on synapses
Stimulate the nervous system by creating more action potentials in post synaptic neurone
Increase release of neurotransmitter
Inhibit enzyme that hydrolyses NET
Similar shape to NET so bind to receptors on post synaptic membrane and mimic NETS effect (agonist)
85
How can drugs have an inhibitory effect on synapses
Create fewer action potentials on the post synaptic membrane
Inhibit the release of neurotransmitter
Hyperpolarise the membrane so resting potential becomes more negative and harder to reach threshold potential
Bind to and block receptors on the post synaptic membrane due to similar shape to NETS
86
List some drugs
```
Alcohol
Amphetamines
Cocaine
Codeine
Caffeine
Curare
Heroin
Nicotine
Valium
```
87
Cocaine
Prevents hydrolysis of neurotransmitter involved in sympathetic branch of autonomic nervous system
88
How do codeine and heroin work
Bind to endorphin receptors which are neurotransmitters involved in sensory nerve pathways and specifically pain pathways
89
Valium
Increases the effects of GABA
90
Caffeine
Reduces the threshold value for neurone excitation
91
Nicotine
Similar shape to ACh
| Binds to nicotinic cholinergic receptors
92
Curare
Blocks ACh affects by blocking receptors at neuromuscular junctions
Muscles can't be stimulated
Paralysis
93
Alcohol
Inhibits neurotransmitter release from presynaptic neurone so fewer receptors activated
94
Amphetamines
Stimulate neurotransmitter release from presynaptic neurone so more receptors activated
95
Advantage of taxis/kinesis
Increased likelihood of returning to favourable conditions with better...
Food availability
Temperature
Less competition
Less predators
SPECIFIC TO Q
96
Why do unmyelinated axons use more ATP than myelinated axons
ATP needed for active transport
In myelinated axons, active transport of sodium and potassium through the sodium potassium pump only takes place at the nodes of Ranvier
Whereas active transport occurs along the whole length of an unmyelinated axon
97
Why do we need proteins to transport sodium and potassium
They are ions
So they are charged particles
Charged particles can't cross the phospholipid bilayer unaided
98
How does GABA inhibit nerve impulse transmission
Binds to receptors on post synaptic membrane
Opens chloride ion protein channels
Chloride ions diffuse in
Inside is more negatively charged than the outside (hyperpolarised)
Threshold not reached by stimulus
No depolarisation
Reduced effect of sodium ions entering
99
What is an agonist
Binds to receptor
Similar shape to NET
Producing a similar response to intended neurotransmitter
100
What is an antagonist
Binds to receptor
Similar shape to NET
Stopping it producing the correct response
101
How is a resting potential maintained
Membrane relatively impermeable to sodium ions
Voltage gates sodium channels closed
3 sodium ions pumped out and 2 potassium ions pumped in by active transport via sodium potassium pump
Potassium ions diffuse out down their concentration gradient
Through leaky potassium channel proteins
Increased sodium outside the neurone
So inside more negative than outside
102
Purpose of acetylcholinesterase
Hydrolyses acetylcholine into choline and ethanoic acid
So acetylcholine doesn't stay bound to the receptor on the post synaptic neurone membrane and keep repeating action potentials/overstimulation
Choline and ethanoic acid diffuse back across synaptic cleft
Transported across the presynaptic membrane
ATP released from ATP hydrolysis by mitochondria used to resynthesise acetylcholine
Which is then stored in vesicles
103
Advantage of mitochondria noting to the presynaptic membrane when nerve impulses arive
Causes calcium channel proteins to open
Calcium diffuses in
Causes vesicles to fuse with the membrane by activating enzymes
104
Advantages of simple reflexes
```
Rapid
Protect against damage to body tissue
Do not have to be learnt
Help escape predators
Enable homeostatic control
```
105
How do synapses ensure nerve impulses only travel in one direction
Receptors only on the post synaptic neurone membrane
| Neurotransmitters only made and stored and released from the pre synaptic neurone
