Biology cell specialisation and Tissue structure and function Flashcards
(278 cards)
1
Q
Why does a cell specialises ?
A
A cell specialises because the shape and contents of a cell help it to carry out its function.
2
Q
What is the cell organisation order ?
A
Specialised cells are organised into tissues . Tissues into organs and organs into organ systems. Organ systems into organism
3
Q
What are some examples of tissues ?
A
Muscle Tissue and xylem tissue
4
Q
What are some examples of organs ?
A
The animal heart
Plant leaf
5
Q
What are some examples of organ systems ?
A
The female reproductive system
6
Q
What are the features of a red blood cell ?
A
No nucleus
Haemoglobin
Biconcave shape
Small Size
7
Q
Why do red blood cells have no nucleus ?
A
This frees up more room for haemoglobin. This maximises the amount of oxygen that red blood cells can carry
8
Q
Why do red blood cells have haemoglobin ?
A
Haemoglobin carries oxygen which will then be released to the body cells to be used for respiration.
9
Q
Why do red blood cells have a biconcave shape ?
A
This creates a large surface area and allows for the rapid diffusion of oxygen.
10
Q
Why are red blood cells a small size ?
A
Red blood cells are small so that they can pass through tiny capillaries.
11
Q
What name is given to the shape of red blood cells?
A
Biconcave
12
Q
What are the features of white blood cells ?
A
Have a nucleus
Can change shape
13
Q
What do white blood cells do ?
A
They defend against infection
14
Q
Why do white blood cells change shape ?
A
This allows the white blood cells to squeeze through the walls of blood vessels into body tissues and to engulf harmful microorganisms
15
Q
What would happen if red blood cells had a nucleus?
A
There would be less room for haemoglobin and oxygen.
16
Q
Where does gas exchange take place in plants ?
A
Gas exchange takes place in the mesophyll cells
17
Q
Where are mesophyll cells located ?
A
They are located in the middle layer of plant leaves.
18
Q
What are mesophyll cells the site of ?
A
They are the site of photosynthesis
19
Q
Why do Mesophyll cells have a large surface area ?
A
To allow rapid exchange of carbon dioxide and oxygen with the environment.
20
Q
What happens in the stomata ?
A
Carbon dioxide diffuses into plant leaves through pores on the underside of the leaf called stomata.
21
Q
What is the underside of a leaf called ?
A
The underside of the leaf is called the epidermis.
22
Q
What do stomata also play a role in ?
A
In controlling water
23
Q
What is in the stomata and why ?
A
There is a guard cell on either side of a stoma that can open and close the stomata to control water loss
24
Q
What happens when the Guard cells swell ?
A
When the guard cells swell the stomata opens.
25
What are the features of Root hair cells ?
No chloroplasts
Long projections
26
Where are Root hair cells located ? and why
They are located underground. This means that they do not contain chloroplasts . There is no light for photosynthesis
27
Why do the long projections of root hair cells do ? and why
Root hair cells have long projections that increase the surface area that the plant can use to absorb water and minerals.
28
What are root hair cells specialised to do ?
Root hair cells are specialised to increase the efficiency of water absorption and the uptake of minerals required for the plants survival
29
What are root hair cells ( 3 things)
Eukaryotes
Specialised
Not used for photosynthesis
30
What are Gametes ? ( full definition)
Gametes are sex cells . Gametes are haploid reproductive cells that fuse during fertilization to form a new organism, carrying genetic information from each parent.
31
What is the function of sperm cells ?
Sperm cells must swim towards the egg.
32
How does the tail move in a sperm cell ?
The tail moves with energy provided by mitochondria in the midpiece of the sperm.
33
what are the features of sperm cells ?
Long tail
Genetic material is contained in the head of sperm cells
Head is covered by acrosome
Very small
34
Why is there genetic material in the head of a sperm cell ?
The genetic material is contained in the head of the sperm cell, inside a nucleus. The head of the sperm is the only part to enter the egg of a female
35
Why is head of the sperm cell covered with an Acrosome ?
The head is covered by an acrosome , which releases enzymes to break to break down the zona pellucida
36
Why are sperm cells very small ?
Sperm cells are very small so males can make many of them to increase the chance of fertilisation.
37
What are the features of Egg cells ?
-much bigger than sperm cells
- cytoplasm in high in nutrients
- role of Zona pellicuda
38
Why are egg cells much bigger than sperm cells ?
Females produce less eggs than males produce sperm , but more is invested in each egg
39
Why is the cytoplasm in the egg cell highly in nutrients ?
The cytoplasm of the egg cell is high in nutrients which are used when the embryo is growing.
40
What must happen to the Zona Pellicuda in a egg cell ?
The zona pellucida must be penetrated by a sperm in order for the egg to be fertilised
41
What does the zona pellicuda play a role in the egg cell ?
The zona pellicuda plays a role in preventing polyspermy, where more than one sperm fertilises the egg.
42
What is the name of the outer membrane of an egg cell?
Zona pellicuda
42
What is the structure of the human gas exchange ?
Trachea
Bronchi
Bronchioles
Capillary
Alveolus
42
What is the entrance to the huma gas exchange system ?
The trachea is the entrance to the human gas exchange system
43
What happens when you breathe in ?
When you breathe in , air flows through the trachea
44
What surrounds the front of the trachea ?
Ridges of cartilage surround the front of the trachea
44
What do the Ridges of cartilage provide at the front of the trachea ?
They provide protection and structure
45
Why is there no cartilage at the back of the trachea ?
There is no cartilage at the back of the trachea so that the oesophagus is not constricted.
46
What is the oesophagus ?
Oesophagus is the tube where food travels.
47
What does the trachea divide into ?
The trachea divide into two bronchi
48
Where does air flow along each bronchus into ?
Air flows along each bronchus to a lung.
49
What are the bronchi made from ?
The bronchi are made from cartilage and smooth muscle
50
What does Each bronchus divide into ?
Each bronchus divides into many smaller bronchioles
51
What do the many bronchioles branch into the lungs into what ?
The many bronchioles branch throughout the lungs into small air sacs called alveoli
52
What are the Alveoli ?
The alveoli are sacs that fill with air when you breathe in.
53
Where does oxygen in the alveoli diffuse into ?
Oxygen in the alveoli diffuses into the bloodstream.
54
Where does carbon dioxide in the bloodstream diffuse into ?
Carbon dioxide in the bloodstream diffuse into the alveoli
55
How many alveoli are there in the lungs ?
There are millions of alveoli in the lungs
56
What do the alveoli provide in the lungs ?
The alveoli provide a large surface area for gas exchange
57
What is ventilation controlled by ?
Ventilation is controlled by the ribcage, intercostal muscles and the diaphragm.
58
What happens when you breathe in ?
the 3 structures move to allow the lungs to fill with air.
58
What is lined with the columnar epithelium ?
The trachea , bronchi and large bronchioles are lined with columnar ciliated epithelium.
58
What happens when you breathe out ?
The 3 structures move to allow air to leave the lungs.
59
What are goblet cells ?
Goblet cells are the mucus secreting cells of ciliated epithelium.
60
What do the capillaries do ?
They provide a large surface area for gas exchange between the alveoli and the bloodstream
60
What does the mucus trap ?
It traps dust, particles and pathogens
61
What are 3 features of ciliated cells ?
They are columnar in shape. They have multiple , thin projections form their surface. Cilia contract and waft the mucus produced by goblet cells up the trachea to the back of the throat, where it is swallowed.
61
What is each alveolus surrounded by ?
Each alveolus is surrounded by an network of capillaries
62
What is the name of the mucus-secreting cells of ciliated epithelium?
Goblet cells
62
What is the alveolar epithelium made up of ?
The alveolar epithelium is made up of a single layer of squamous epithelial cells that line the walls of the alveoli.
63
What are alveoli ?
Alveoli are the millions of air sacs within the lungs where gases are exchanged with the bloodstream.
63
What are any swallowed pathogens destroyed by ?
Any swallowed pathogens are destroyed by stomach acid
63
What are features of squamous epithelial cells ?
Generally round , flat and have a small centrally located nucleus.
64
In the alveoli what are the squamous cells arranged as ?
In the alveoli , the squamous cells are arranged in a single layer to facilitate gas diffusion.
65
What does the squamous epithelium do ?
It provides a very short diffusion distance from the alveoli to the capillaries which maximises the rate of gas exchange
66
What do the capillaries supply and where ?
The capillaries supply carbon dioxide to the alveoli and oxygen is rapidly carried away from the alveoli
67
What does the steep concentration gradient allow ?
The steep concentration gradient allows quick diffusion of gases into and out of the bloodstream.
67
What do the quick transport of gases in the bloodstream maintain ?
The quick transport of gases in the bloodstream maintains a steep concentration gradient into and out of the bloodstream
68
What does cigarette smoke contain ?
It contains harmful chemicals such as nicotine, carbon monoxide and carniogens
69
Why is nicotine harmful to the heart ?
Nicotine is very addictive and puts strain on the heart.
70
What is the impact of carbon monoxide on the heart ?
It puts strain on the heart by reducing oxygen transport in the blood.
70
How does carbon monoxide affect red blood cells ?
It reduces their ability to carry oxygen by binding to haemoglobin with 200 times the affinity of oxygen.
71
How does nicotine affect heart function ?
It acts as a stimulant, causing the heart to beat faster and with greater force, increasing blood pressure
72
What health conditions can be caused by nicotine and carbon monoxide ?
Both substances can cause heart disease and strokes.
72
What is a common symptom of emphysema ?
Shortness of breath
72
How does smoking affect the alveoli ?
Smoking damages the elastic fibres in the alveoli, preventing elastic recoil and causing overinflation of the lungs
72
What is Emphysema and what causes it ?
Emphysema is a condition where gas exchange can not happen efficiently, often caused by damage to the alveoli from smoking
72
What condition is formed by both bronchitis and emphysema ?
Chronic obstructive Pulmonary disease
73
What are common symptoms of COPD ?
Cough
Breathlessness
Wheezing
74
What happens to the cilia cells when smoke is inhaled ?
Smoke damages the cilia cells of the airways
74
What is the role of the cilia in the airways ?
Cilia waft away mucus produced by goblet cells
75
What happens when cilia are damaged ?
Muscle builds up because it cannot be cleared effectively
76
What condition can result from mucus build up in the airways ?
Bronchitis, where the airways are partially blocked with mucus
77
What can the carcinogens in the tar in cigarettes can cause ?
The carcinogens in the tar in cigarettes can cause tumours to form in the airways
78
What can smoking cause ?
Smoking can cause mouth, throat and lung cancers
79
What disease is not caused by smoking?
Kidney failture
80
What happens when arteries reach an organ ?
When arteries reach an organ , they split into many smaller vessels called arterioles.
80
What are the harmful chemicals found in cigarette smoke ?
Carbon monoxide
Nicotine / Tar
Carcinogens - cancer causing chemicals
81
What do veins do ?
Veins transport blood back to the heart
81
How can the direction of blood flow be controlled ?
The direction of blood flow can be controlled by contracting the arterioles to restrict blood flow and relaxing the arterioles to allow blood to flow
82
Why is the lumen of veins wider than the arteries ?
The lumen of veins is wider than the arteries which allows the blood to flow at low pressure.
83
What are the features of veins ?
There is a thin muscle wall and elastic tissue in the vein walls.
84
Why do veins have valves ?
To prevent the backflow of blood and to ensure blood flows towards the heart
85
What do arteries do ?
Arteries transport blood away from the heart to the organs
86
What is one feature of arteries ?
Artery walls have thick layers of muscle
87
What do the artery walls do ?
They maintain a high pressure so blood can be pumped around the body.
88
Why does the artery wall have elastic fibres ?
Elastic fibres in the artery wall allow the arteries to stretch.
89
Why is the endothelium folded ?
The endothelium is folded which also allows the arteries to stretch.
90
Which blood vessel contains valves ?
Veins
91
What is a network of capillaries called ?
Capillary bed
92
What can damage the endothelium of arteries ?
The deposition of white blood cells and lipids can damage the endothelium of arteries
93
What happens if white blood cells and fatty materials continue to be deposited in the artery walls?
They will begin to form hard , fibrous plaque
94
What happens as fibrous plaque builds up in arteries ?
the lumen of the artery becomes narrower.
95
How does plaque build up affect blood flow ?
It restricts the flow of blood through the arteries
96
What impact does a narrower lumen have on blood pressure ?
It increases blood pressure
97
What can Atheroma cause ?
Atheroma's can causes diseases of the heart
97
What is the presence of fibrous plaque in an artery called ?
Atheroma
98
What is coronary heart disease ?
It is a type of disease that is associated with many atheroma.
98
What is Atherosclerosis ?
It is the blockage of an artery by the build-up of flatty plaques
98
What can atherosclerosis cause ?
It can cause sever pain known as angina and complete blockage of the arteries will cause myocardial infarction, the death of cardiac muscle tissue known as a heart attack
98
What do skeletal muscle do ?
They contract and relax to allow you to move your body.
98
What do antagonistic pair s consist of in a skeletal muscle ?
Antagonistic pairs consist of an agonist and an antagonist
98
What do Tendons attach skeletal muscles to ?
Tendons attach skeletal muscles to bones.
99
What do Muscles work ?
Muscles work in a pair to move the bones
100
what is a pair of muscles called ?
A pair of muscles is called an antagonistic pair
100
What happens in an antagonistic pair ?
One muscle contracts when the other muscle relaxes
101
What is the muscle that is relaxing called ?
The muscle that is relaxing is called the antagonist
101
What is the muscle that is contracting called ?
The muscle that is contracting is called the agonist.
102
What do skeletal muscle consist of ?
Skeletal muscle consist of many bundles of muscle fibres.
102
What are muscle fibres ?
Muscle fibres are long , specialised cells
102
What is the sarcolemma ?
The membrane of the muscle fibres is called the sarcolemma
103
What does the sarcolemma fold inwards to and when ?
The sarcolemma folds inwards to the sarcoplasm at certain points
103
What are the inward folds called ?
The inward folds are called transverse tubules.
103
Why are transverse tubules important ?
The tubules are very important in initiating muscle contraction.
103
What is the sarcoplasmic reticulum ?
The sarcoplasmic reticulum is an organelle in the sarcoplasm
103
What does the sarcoplasmic reticulum do ? and why is it important ?
The sarcoplasmic reticulum is a store for calcium ions. This is important in muscle contraction
104
What do muscle fibres also have ?
Muscle fibres also have many mitochondria and nuclei
104
What do the mitochondria provide in a skeletal muscle ?
The mitochondria provide lots of ATP to power muscle contraction
104
What are myofibrils ?
Myofibrils are cylindrical organelles that run along the length of muscle fibres
105
What are myofibrils the site of ?
Myofibrils are the site of muscle contraction
105
What are the features of muscle fibres ?
Myofibrils
Sarcolemma
Transverse tubules
Sarcoplasmic reticulum
Mitochondria
105
What are myofibrils made up ?
They are made up of multiple units that run end to end along the myofibril
106
What are the units called ?
These units are called sarcomeres.
106
What is the end of a sarcomere called ?
The end of a sarcomere is called the Z line
106
What are sarcomeres made up from ?
sarcomeres are made up from two types of myofilaments
106
What do the 2 myofilaments do and why ?
The two myofilaments slide past each other . This movement is what makes muscles contract
106
What are the 2 types of myofilaments and which one is thick and thin ?
Thick myofilaments are made up of myosin protein.
Thin myofilaments are made of actin protein.
107
How are myosin and actin filaments arranged ?
They are arranged in an alternating pattern in sarcomeres.
108
What myosin filaments act over what ?
Thick myosin filaments overlap with the thin actin filaments at each end
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What is the overlapping region called between the 2 filaments ?
The overlapping region is called the A band
109
What is the region with only the myosin filament called ?
The H zone
110
Where do thin actin filaments only overlap with myosin filaments in the sarcomere ?
In the middle of the sarcomere
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What is the middle of the sarcomere called ?
The middle is called the M line
112
What is the region with only the actin filament called ?
The region with only actin filament is called the I band
113
What are the 2 types of skeletal muscle fibres ?
Slow and fast twitch muscle fibres
114
Where is the energy source for slow twitch fibres ?
Rely on energy released through aerobic respiration
114
Where are fast twitch fibres located and given an example ?
Found mainly in muscles such as the arms or the legs
114
Where are slow twitch fibres located and give an example ?
Found in muscles used for posture such as the back or the neck
115
What are fast twitch muscle adapted for and their function ?
It is adapted for fast or strong movement over short period of time.
Muscle fibres are short and wide.
The muscle fatigue quickly and contracts quickly
115
What are slow twitch muscle fibres adapted for and their function ?
It is adapted for endurance and slow movement over long periods of time
Muscle fibres are long and thin
The muscle fatigue slowly and contracts slowly
116
Where is the energy source for fast twitch fibres ?
Rely on energy released through anaerobic respiration
117
What are the 3 main types of neurone ?
Sensory neurone
Motor neurone
Relay neurone
117
What is the cell structure of slow twitch fibres ?
- Lots of mitochondria to maintain aerobic respiration
- lots of capillaries to supply muscle fibres with oxygen
- low levels of glycogen
- low levels of phosphocreatine's
- large stores of myoglobin
- Less sarcoplasmic reticulum
118
What is the structure of fast twitch fibres ?
- Fewer mitochondria
- Fewer capillaries
- High levels of glycogen
- High levels of phosphocreatine
- Small stores of myoglobin
- More sarcoplasmic reticulum
119
What do sensory neurones do ?
They carry nerve impulses from receptors into the central nervous system (CNS)
120
What is another name for a relay neurone ?
Relay neurones are intermediate neurones
120
What do Motor Neurones do ?
They carry impulses from the CNS to effector organs such as muscles or glands
121
What do relay neurones do ?
They receive impulses from a sensory neurone and relay them to motor neurones
122
What is a basic structure of a neurone ?
Dendrites
Axons
Cell body
123
What do dendrites do in neurones ?
Dendrites carry nerve impulses towards a cell body
124
What do Axons do in neurones ?
Axon carries nerve impulses away from the cell body
125
What is the cell body in Neurones ?
It is where the nucleus is normally located.
126
What do Myelin sheaths do in neurones ?
Myelin sheaths insulate neurones , increasing the speed of impulse transmission
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126
127
Where are Schwann cells wrapped around in ?
Schwann cells are wrapped around the axon of the neurone .
127
127
What are Motor neurones in vertebrates usually ?
They are usually myelinated
127
What do Non myelinated neurones still contain ?
They still contain dendrites, axons and a cell body
127
What do Schwann cells form ?
these cells form the myelin sheath
127
What are the gaps between Schwann cells called ?
Gaps between Schwann cells are called Node of Ranvier
127
What do non myelinated neurones not contain ?
They do not contain a myelin sheaht
127
Do non myelinated neurones conduct impulses slower or faster than myelinated neurones ?
Slower
128
Where are non myelinated neurones found ?
They are found in the autonomic nervous system
128
What is the autonomic nervous system ?
It is part of the nervous system that supplies the internal organs such as the stomach , intestine and kidneys
128
What does nerve transmission to internal organs not need ?
Nerve transmission to internal organs often does not need to be as fast as transmission to muscles
128
What are factors that speed up transmission of nerve impulses ?
Myelination
Temperature
Axon Diameter
128
How does axon diameter affect speed up transmission of nerve impulses ?
Giant axons are found in the giant squid and allows it to have rapid escape response. Greater axon diameter means there is a greater surface area for the movement of ions across the cell membrane.
129
What are the key features of resting potential of a neurone ?
Potential difference
Potassium ion channels
Resting potential
Sodium potassium pumps
130
What is potential difference in biology ?
The difference in charge across a neurone membrane
130
What are potassium ion channels ?
Potassium ions diffuse through the neurone cell membrane through these proteins
131
What is resting potential ?
The potential difference when a neurone is at rest
132
What are sodium - potassium pumps ?
Pumps in the neurone cell membrane that actively transport sodium ions out of the neurone and potassium ions in.
133
What is the approximate threshold value of membrane potential, before the membrane becomes depolarised?
-55mV
133
How does the refractory period affect the wave of depolarisation?
Makes it travel in one direction
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What is the structure in a neurone that carries nervous impulses away from the cell body?
Axons
135
What is Depolarisation ?
Depolarisation is an all-or-nothing response. If the potential difference reaches the threshold, depolarisation will always take place and the change in potential difference will always be the same.
136
What happens at resting potential ?
At resting state, there is a difference in charge across the neurone membrane: the inside of the neurone is more negatively charged than outside. The difference in charge is called a potential difference.
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What is the approximate value of the resting potential of a neurone?
-70mV
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When a neurone is stimulated, the Na+ ion channels in the cell membrane open, and Na+ ions flood into the neurone. What effect does this have on the membrane potential?
The membrane potential becomes more postive
139
To what membrane potential must the neurone membrane depolarise to before the sodium ion channels close and the potassium ion channels open?
+30mV
140
What name is given to the period of hyperpolarisation in an action potential?
The refractory period
141
How can myelination speed up the transmission of nerve impulses?
Schwann cells wrap around the axon of neurones to create a myelin sheath.
The myelin sheath acts as an electrical insulator because it is impermeable to ions (Na+ and K+).
Depolarisation and action potentials cannot occur at the myelinated parts of the axon and can only occur in the gaps between (the nodes of Ranvier).
The nervous impulse jumps from one node to the next. This is called saltatory conduction.
142
What is a synapse ?
It is a junction between two neurones or between a neurone and an affector
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What is the structure of a synapse ?
Electrical impulse in
Nerve 1
Synapse
Neurotransmitter
Nerve 2
New electrical impulse created
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What are the features of a synapse ?
Synaptic cleft
Presynaptic neurone
Synaptic knob
Synaptic vesicles
Neurotransmitters
Postsynaptic membrane
145
What is the name of the gap at a synapse between the cells ?
At a synapse there is a gap between the cells. The gap is called the synaptic cleft
146
What is the presynaptic neurone ?
The presynaptic neurone is the neurone before the synapse
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What happens when an action potential reaches the end of the presynaptic neurone ?
When an action potential reaches the end of the neurone, it is transmitted across the presynaptic membrane to the postsynaptic membrane or to an effector cell
146
What happens when an action potential reaches a synapse ?
When an action potential reaches a synapse , it must be transmitted across the synaptic cleft
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What is the name of the end of the axon of the presynaptic neurone ?
The end of the axon of the presynaptic neurone is called the synaptic knob.
147
What is the synaptic knob ? ( full definition)
The synaptic knob is a swelling which contains synaptic vesicles. It is the location where the nerve impulse is transmitted across the synaptic cleft
148
Where are synaptic vesicles located and what are they ?
Synaptic vesicles are vesicles located in the synaptic knob.
148
What are Neurotransmitters ?
Neurotransmitters are the chemicals that allow an action potential to be transferred across a synapse.
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Why are there lots of mitochondria in the synaptic knob ?
There are also lots of mitochondria in the synaptic knob. This is because lots of energy is needed to synthesise neurotransmitters.
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What do the synaptic vesicles contain and what do they do ?
The vesicles contain neurotransmitters. the vesicles fuse with the presynaptic membrane to release neurotransmitters into the synaptic cleft.
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What happens when neurotransmitters are released ?
When neurotransmitters are released from the synaptic vesicles into the synaptic cleft , they bind to specific receptors on the postsynaptic membrane.
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What is the postsynaptic membrane ?
The postsynaptic membrane is the membrane of the postsynaptic neurone or effector cells
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What is the function of receptors on the postsynaptic membrane ?
Receptors on the postsynaptic membrane have a complementary shape to the neurotransmitters released from the synaptic knob
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What happens when neurotransmitters bind to their receptors on the postsynaptic membrane ?
When neurotransmitters bind to their receptors, the action potential contibues
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Why are there only receptors on the postsynaptic membrane ?
There are only receptors on the postsynaptic membrane. This ensures the nerve impulse only moves in one direction.
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What is the end of the axon of the presynaptic neurone called?
Synaptic knob
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What are the 2 different types of neurotransmitters ?
Excitatory or inhibitory
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What happens when neurotransmitters bind to receptors on the postsynaptic membrane ?
The membrane is depolarised, which leads to the transmission of the nerve impulse.
155
What is an example of an excitatory neurotransmitter ?
Acetylcholine is an example. When it binds to receptors on the postsynaptic membrane in the CNS , an action potential is estabilished
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What do Excitatory neurotransmitters do ?
They generate an action potential in the postsynaptic cell
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What do Inhibitory neurotransmitters do ?
They prevent an action potential from being generated in the postsynaptic cell
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What happens when the neurotransmitters bind to the receptors on the postsynaptic membrane ?
The membrane is hyperpolarised
157
What happens when acetylcholine binds to receptors on the postsynaptic membrane in the heart ?
Potassium ion channels are opened in the membrane. This prevents an action potential from being established.
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What is Summation ?
It is the process where neurotransmitters from multiple neurones are summed together to produce a response.
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What are the 2 types of summation ?
Spatial summation and temporal summation
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When does spatial summation take place ?
It takes place when multiple presynaptic neurones form A junction with a single neurone.
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How does spatial summation lead to an action potential ?
If neurotransmitter release from several presynaptic neurons leads to sufficient depolarisation , the postsynaptic neurone reaches the threshold potential and fires an action potential
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Why is spatial summation important in neutral communication ?
It allows weak signals from multiple neurones to combine, Increasing the likelihood of effective neutral transmission and enhancing responsiveness to stimuli.
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How does spatial summation differ from temporal summation ?
It involves multiple neurons releasing neurotransmitters at the same time while temporal summation occurs when a single neuron releases neurotransmitters in rapid succession.
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What is Temporal summation ?
It takes place when multiple nerve impulses arrive at the same synaptic knob within a short period of time.
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What happens in Temporal summation ?
More neurotransmitter is released into the synaptic cleft so more neurotransmitter is available to bind to receptors on the postsynaptic membrane
166
What can the neurotransmitter establish together in temporal summation ?
It can establish a generator potential that reaches the threshold value and an action potential is generated.
167
What happens after the arrival of the action potential at the synaptic knob?
The action potential depolarises the membrane
Voltage-gated calcium ion channels open
Calcium ions diffuse into the synaptic knob
168
What are the differences between neuromuscular junctions and cholinergic synapses?
Types of postsynaptic cell
Number of receptors
Types of response (inhibitory and/or excitatory)
Result of depolarisation
Location of the enzyme acetylcholinesterase
169
Where is acetylcholinesterase stored in a neuromuscular junction?
Clefts in the postsynaptic membrane
170
How does Acetylcholine bind to Receptors
Acetylcholine binds to specific receptors on the postsynaptic membrane called nicotinic cholinergic receptors. Binding of the neurotransmitter opens sodium ion channels in the postsynaptic muscle cell.
171
what is the stages of transmission across a neuromuscular junction ?
1. Arrival of the action potential at the synaptic knob
2. Release of acetylcholine
3. Binding of acetylcholine to receptors
4. Removal of acetylcholine by acetylcholinesterase
172
What is the enzyme that breaks down Acetylcholine in the synaptic cleft ?
Acetylcholine is broken down in the synaptic cleft by an enzyme called acetylcholinesterase.
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What is a neuromuscular junction between ?
Motor neurone and muscle cell
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Where is acetylcholinesterase stored in a neuromuscular junction?
Clefts in the postsynaptic membrane
175
What happens when the postsynaptic membrane is depolarised in a cholinergic synapse ?
Depolarisation of the postsynaptic membrane results in an action potential allowing the signal to be transmitted to the next neuron.
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What are the differences between neuromuscular junctions and cholinergic synapses?
Types of postsynaptic cell
Number of receptors
Types of response (inhibitory and/or excitatory)
Result of depolarisation
Location of the enzyme acetylcholinesterase
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What are excitatory drugs and what do they do ?
They stimulate the nervous system producing more action potentials on the post synaptic membrane.
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How do agonist drugs affect neurotransmission ? and give an example ?
Agonist drugs mimic neurotransmitters by binding to receptors on the postsynaptic membrane , triggering an action potential . Nicotine binds to nicotinic cholinergic receptors to mimic acetylcholine
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What role does acetylcholine play in a cholinergic synapse ?
Acetylcholine is the neurotransmitter released into the synaptic cleft binding to receptors on the postsynaptic membrane and initiating depolarisation.
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How do drugs inhibit enzymes to affect neurotransmitter breakdown ?
Drugs can bind to enzymes to prevent neurotransmitter breakdown , allowing continued neurotransmitter activity and action potential generation
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What happens if neurotransmitter breakdown is prevented ?
The neurotransmitter will persist in the synaptic cleft continuously stimulating the postsynaptic membrane
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What is an example of enzyme inhibition affecting neurotransmitter breakdown ?
Nerve gas inhibits acetylcholinesterase stopping acetylcholine breakdown which leads to loss of muscle control
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What enzyme does nerve gas inhibit ?
Acetylcholinesterase , the enzyme responsible for breaking down acetylcholine.
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What are the consequences of inhibiting acetylcholinesterase ?
Acetylcholine remains in the synapse continuously stimulating muscle contraction , leading to paralysis or loss of control.
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What can drugs cause presynaptic neurones to do ?
Drugs can cause presynaptic neurones to release neurotransmitters
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What happens when there is more neurotransmitters ?
More neurotransmitters will activate more receptors and an action potential is more likely to be created.
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What can drugs also do ?
Drugs can block calcium ion channels in the presynaptic membrane
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What would blocking calcium ions do ? and give an example
Blocking calcium ions would prevent the release of neurotransmitters from the presynaptic neurone. E.g. alcohol.
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What can drugs do on the postsynaptic membrane ?
Drugs can block receptors on the postsynaptic membrane
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What happens if receptors are blocked ?
If receptors are blocked neurotransmitters cannot bind and an action potential is not generated in the postsynaptic neurone.
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What is the name of drugs that block receptors and give an example ?
Antagonists.
Curare blocks nicotinic cholinergic receptors causing muscle paralysis.
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What can chemical imbalances in the brain lead to ?
It can lead to ill health , including Parkinson's disease and depression
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When does Parkinson's disease develop ?
It develops when nerve cells that produce dopamine are lost
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Why is dopamaine important ?
Dopamine is important in coordinating body movement
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What are the symptoms of people that have Parkinson's disease ?
Tremor
Stiff muscles
Slow movement
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What can increasing dopamine levels do ?
Increasing dopamine levels can alleviate the effects of Parkinson's disease
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What has been associated with depression ?
Low serotonin levels have been associated with depression
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What is serotonin ?
Serotonin is a neurotransmitter thought to be associated with a good mood
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What works by increasing the serotonin levels in the body ?
Some antidepressants work by increasing the serotonin levels in the body.
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What is used to treat Parkinson's disease ?
L - Dopa ( levodopa) is used to treat Parkinson's disease
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What does Parkinson's disease result from ?
It results from a loss of neurons that produce dopamine.
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What is MDMA and where is it found ?
It is an amphetamine found in ecstasy, a class A drug
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How does MDMA work ?
It works by increasing the activity of neurotransmitters including serotonin
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What does MDMA do ?
It stops serotonin from being absorbed properly, so more serotonin is released
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What can MDMA give someone a sense of and what is the result ?
It can give someone a sense of euphoria as a result of excessive serotonin release, but this results in a feeling of a comedown several hours after taking MDMA
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