Neurobiology & Immunology Flashcards
1
Q
What can the nervous system be divided into?
A
The central nervous system CNS
the peripheral nervous system PNS
2
Q
What is the CNS made up of?
A
The brain
The spinal cord
3
Q
Function of the brain in the CNS?
A
Processing of information
4
Q
Function of the spinal cord in the CNS?
A
Connects brain with PNS
5
Q
What structure is in the peripheral nervous system?
A
Nerves
6
Q
Function of nerves in the PNS?
A
Carries information to and from all parts of the body
7
Q
The overall functions of the PNS can be split into the _____ nervous system (SNS) and the _____ nervous system (ANS)
A
Somatic
Autonomic
8
Q
Is the Somatic Nervous System voluntary or involuntary?
A
Voluntary
9
Q
Is the Autonomic Nervous System voluntary or involuntary?
A
Involuntary
10
Q
What does the autonomic nervous system consist of?
A
Sympathetic System
Parasympathetic system
11
Q
Describe the sympathetic system of the ANS?
A
Prepares the body for action
‘Flight or fight’ response
12
Q
Describe the parasympathetic system of the ANS?
A
Calms body down
Prepares body for rest and allows recovery - ‘rest and digest’
13
Q
What does the somatic nervous system include?
A
The spinal nerves and contains sensory and motor neurones
14
Q
What does the SNS control?
A
Voluntary movements of skeletal muscle and is also responsible for involuntary reflex actions
15
Q
How does the ANS regulate the internal environment?
A
By controlling the heart, blood vessels, bronchioles, and alimentary canal to maintain heartbeat, breathing rate and digestive processes
16
Q
What does the ANS control?
A
Involuntary functions through smooth muscle, cardiac muscle and glands
17
Q
What does the ANS consist of?
A
Sympathetic and parasympathetic systems that work to regulate processes
18
Q
Why is the relationship between the sympathetic and parasympathetic systems described as antagonistic?
A
They affect the same body structures but exert opposite effects
19
Q
Describe the sympathetic effect of the ANS on heart rate
A
Increases rate
20
Q
Describe the parasympathetic effect of the ANS on heart rate
A
Decreases rate
21
Q
Describe the sympathetic effect of the ANS on breathing rate
A
Increases rate and depth
22
Q
Describe the parasympathetic effect of the ANS on breathing rate
A
Decreases rate and depth
23
Q
Describe the sympathetic effect of the ANS on peristalsis
A
Decreases rate
24
Q
Describe the parasympathetic effect of the ANS on peristalsis
A
Increases rate
25
Describe the sympathetic effect of the ANS on secretion of digestive juices and bile
Decreases rate
26
Describe the parasympathetic effect of the ANS on secretion of digestive juices and bile
Increases rate
27
Examples of effectors
Muscles/glands
28
Examples of stimuli
Temperature of blood/skin
29
Example of a response
Muscle contraction
30
Describe a sensory and motor pathway
* Stimulus is detected by receptors in external sensory organs (eyes, ears) or internally (thermoreceptors)
* sensory neurone carry impulses from sense organs to CNS
* motor neurone carry impulses from CNS to muscles and glands
* response eg muscle contraction
31
What is a neural pathway?
The route that a nerve impulse follows through the nervous system
32
What’s a converging neural pathway?
Several impulses from several neurones all travel to one neurone
33
What’s the purpose of a converging neural pathway?
It increases the sensitivity to excitatory or inhibitory signals allowing weak stimulus to be amplified, as in the visual pathway
34
What are rods and cones?
Photoreceptors whose pigments break down in the presence of light
35
___ are not very sensitive to light so ___ is needed to break the pigments down
Cones
Daylight
36
___ are so sensitive to light they react in very __ light
Rods
Dim
37
What happens as light intensity entering the eye decreases?
Cones cease to function and rods take over
38
What kind of pathway do rods form and why?
Converging pathways, allowing several impulses to be transmitted simultaneously
39
The ____ effect for several rods with the same neuron results the in transmission _____ being met, enabling transmission of the nerve impulse. This allows vision in total darkness
Cumulative
Threshold
40
What happens in diverging neural pathways
Impulses from one single neuron travel to several neurons, allowing the pathway to reach several destinations at the same time
41
Diverging neural pathways allow ___ ___ control
Fine motor
42
The SNA controls skeletal muscles via what?
Motor neurons
43
The diverging pathway of motor neurons for skeletal muscles allows what?
Simultaneous stimulation of the muscles in the hand to allow the fingers and thumb to operate in unison
44
The neural pathway of the hypothalamus diverges into branches exerting what?
Coordinated control in temperature regulation
45
What is a reverberating pathway?
In a reverberating pathway, neurons later in the pathway link back to earlier neurons so that the nerve impulse passes repeatedly through the circuit
46
What do reverberating pathways allow?
Allow impulses to be recycled enabling repeating stimulation of the pathway
47
How long can a pathway reverberate and transmit impulses?
For seconds, hours or a lifetime
48
Example of a reverberating neural pathway?
Pathway that controls breathing
49
Function of the cerebrum
Responsible for memory, conscious thought and intelligence
50
Cerebral cortex =
Outer layer of cerebrum
51
Function of the cerebellum
Controls balance and muscle coordination
52
Function of the medulla
Controls heart rate and breathing rate
53
What is the cerebral cortex?
The outer part of the cerebrum and is the centre of conscious thought
54
What is the cerebral cortex able to do?
Recall memories and alter behaviour in light of past experience
55
3 key function of the cerebral cortex?
* received sensory information
* coordinates voluntary movement
* makes decisions based on experience
56
What is the cerebrum divided into?
Two halves
Left and right cerebral hemispheres
57
Each cerebral hemisphere processes information from and controls?
The opposite side of the body
58
The left hemisphere receives info from the ___ visual field and controls the ___ side of the body
Right
59
What is the corpus callosum?
A bundle of nerve fibres which connects the cerebral hemispheres
60
What does the corpus callosum allow?
The transfer of information from one hemisphere to the other enabling the brain to act as an integrated whole
61
What would happen if the corpus callosum was absent?
The exchange of information between the cerebral hemispheres cannot take place and each hemisphere receives only half the field of view
62
Function of the motor area of the cerebral cortex?
Coordination of voluntary movement
63
Function of the sensory area of the cerebral cortex?
Receives information from body receptors
64
Functional areas of the cerebral cortex?
* Motor area
* Sensory area
* Visual area
* Auditory area
* Speech motor area
65
What do the sensory areas of the cerebral cortex do?
Receive information as sensory impulses from receptors
| eg touch receptors in skin
66
What do the association areas of the cerebral cortex do?
Analyse and interpret the impulses receives from the sensory areas and deal with thought processes, language, personality, imagination and intelligence (make decisions)
67
What do the motor areas of the cerebral cortex do?
Receive info from association areas and ‘carry out orders’ by sending motor impulses to the appropriate effectors
(Eg skeletal muscles)
68
What is memory?
The capacity of the brain to store information, retain it and retrieve it when required
69
How does the brain form new memories?
Info coming in is changed into a usable form - encoded - and then stored.
It must also be retrieved at a later date
70
What is encoding?
Information that we can see, hear, think, and feel is changed into a form the brain can process and store
71
What is storage?
The retention of information over a period of time - 30s or a lifetime
72
What is retrieval?
Recovery of stored material
73
What is the quality of the memory affected by during encoding?
The attention given to the task of encoding
74
What’s shallow encoding?
Information is encoded by rehearsal (less effective)
75
What is elaborative encoding?
Associating information or linking them to their meaning leads to improved information retention
76
What is the sensory memory?
Retains all visual and auditory input very briefly (0.5-3secs)
Only selected images and sounds are encoded and passed to the STM
77
What is the short term memory (STM)?
Limited capacity (~7 items)
Holds info for up to 30s
To avoid loss of info from STM we use rehearsal
This helps transfer info to LTM
Info not transferred is displaced
78
What happens to information that is not transferred to the LTM?
It is lost by displacement (pushed out by incoming info) or decay (breakdown of a fragile memory trace)
79
What’s the long term memory (LTM)?
Unlimited capacity and stored info for a long period of time
80
How can the STM be increased?
Chunking
81
What is STM chunking?
A meaningful unit of information made up of smaller units eg phone number
82
What is rehearsal?
Repeating a piece of information that you are trying to memorise over and over
helps extend the time the info is maintained in STM
Promotes transfer of info into LTM
83
What is the serial position effect?
Items at the start and end of a list are more easily recalled than the items in the middle
84
What is The transfer of information from STM to LTM aided by?
* Rehearsal
* Organisation
* Elaboration
85
What is organisation?
Info organised into categories are more easily transferred to LTM
86
What is elaboration of meaning?
By analysing the meaning of the item to be memorised and taking note of its various features and properties it becomes more interesting and meaningful - makes an impression
87
What is a contextual clue?
Relates to the time and place when the information was encoded and committed to the LTM
Triggers memories
88
What are glial cells?
Support and maintain neurons
Produce the myelin sheath (lay down layers of plasma membrane)
89
What do neurones consist of?
* Cell body
* Axon
* Several dendrites
90
What’s the cell body of a neurone?
Control centre of the cells metabolism
Contains ribosomes, nucleus and cytoplasm
91
What are dendrites?
Nerve fibres which receive impulses and pass them towards cell body
92
What’s an axon?
Single nerve fibre carries impulses away from cell body to effector
Pass of impulses to next neuron in sequence
93
What are the 3 types of neuron?
Sensory
Inter
Motor
94
What is the myelin sheath?
A layer of fatty material surrounding axons which insulated the acid and greatly increases the speed of impulse conduction from node to node along an axon
95
What’s myelination?
The development of myelin around the axon
96
Myelination is not complete when?
Not complete at birth and continued during development until adolescence
97
What are the small gaps in the myelin sheath called?
Nodes
98
What happens in unmyelinated fibres?
The axon is exposed and the speed of the impulse is greatly reduced
99
Why are responses to stimulus in the first 2 yrs of life not as rapid or coordinated?
Myelination is not complete
100
What is a synapse?
The tiny region of functional contact between the axon ending of one neuron and the dendrite of the next neuron in a pathway
101
What is the nerve cell before the synaptic cleft called?
Presynaptic neuron
102
What is the nerve cell after the synaptic cleft called?
Postsynaptic neuron
103
What’s the synaptic cleft?
The space between the presynaptic and postsynaptic neurons
104
How are messages relayed across synaptic clefts?
By neurotransmitters
105
How do neurons connect muscle fibres and endocrine glands?
Via spaces similar to synaptic clefts
106
What do neurotransmitters do?
Relay impulses across the synaptic cleft
107
Where are neurotransmitters stored?
In vesicles in axons endings of presynaptic neurones
108
When are neurotransmitters released into the synaptic cleft?
On arrival of an impulse
109
What happens to neurotransmitters after they are release?
Diffuse across cleft and bind to receptor sites on postsynaptic membrane which opens ion channels, causing an impulse to be initiated in the postsynaptic membrane
110
Examples of neurotransmitter?
Acetylcholine
Noradrenaline
111
What does the removal of neurotransmitters prevent?
The continuous stimulation of postsynaptic neurons
112
How is acetylcholine removed?
Broken down by an enzyme on the postsynaptic membrane
113
How is noradrenaline removed?
Reabsorbed by the presynaptic membrane and stored in vesicles for reuse
114
Describe what kind of signal acetylcholine released between a motor neurone and a heart muscle fibres produces?
An inhibitory effect
The rate and strength of contraction of cardiac muscle is reduced
115
Describe the signal acetylcholine released between a motor neurone and a skeletal muscle fibre produces?
Excitatory effect on the muscle making it contract
116
What kinds of signal can neurotransmitters produce?
Excitatory or inhibitory
117
A nerve impulse is only transmitted across a synapse if?
It causes the release of a minimum number of neurotransmitter molecules to bind to a sufficient number of receptor sites and reach the threshold
118
How is weak stimuli filtered out?
By the synapse acting as an unbridgeable gap
119
Example of weak stimuli
The continuous low level drone of machinery does not trigger the release of enough neurotransmitter, but a sudden increase in volume can make a person aware of the machinery
120
What is summation?
The cumulative effect of a series of weak stimuli that together bring about an impulse
121
What are endorphins?
Neurotransmitters which act as natural pain killers in the body
They combine with receptors of synapses and block transmission of pain signals
122
Where are endorphins produced?
The hypothalamus
123
What does the level of production of endorphins increase in response to?
* physical/emotional stress
* severe injury
* long periods of vigorous exercise
* certain foods (chocolate)
124
Increased levels of endorphins cause?
* changes in appetite
* release of sex hormones
* feelings of euphoria
125
What is dopamine?
A neurotransmitter which induces the feelings of pleasure and featured in a behavioural reward pathway
126
What is the reward pathway?
Involves neurons which secrete or respond to dopamine
This is activated when an individual engaged in a survival behaviour that is beneficial to them (eating when hungry)
127
What does centre ‘No in the reward pathway do?
Releases dopamine and induces a pleasurable feeling (nucleus accumbens)
128
What does centre View in the reward pathway do?
Releases dopamine when a need is satisfied
129
What is the frontal area of the cerebral cortex responsible for in the reward pathway?
Cognitive appreciation of pleasure
130
What are the brains pleasure centres?
Centres N and V in the reward pathway
131
What is Alzheimer’s disease?
An incurable and terminal form of dementia where the brain gradually degenerates
Impulses cannot be transmitted as normal
132
What is the cause of Alzheimer’s?
It is thought the loss of neurons which make acetylcholine is the cause
133
Treatment of Alzheimer’s?
Some drugs such as cholinesterase inhibitors, which increases the acetylcholine concentration in the synaptic clefts, improving communication between neurons
134
Effectiveness of drugs for Alzheimer’s?
In some people they do improve the symptoms and temporarily slow down the disease but are mostly found to be ineffective
135
What is Parkinson’s Disease?
A severe loss of dopamine leads to muscle tremors, difficulty in initiation of movement and speech, reduced fine motor control
136
How is Parkinson’s caused?
By loss of neurons that synthesise dopamine
137
Treatment for Parkinson’s?
L-dopa
Inhibition of MAO
Stem cells
138
L-dopa treatment for Parkinson’s?
Dopamine cannot cross the BBB but L-soap can and is converted to dopamine
As it penetrates the whole brain (dopamine normally only releases in specific areas) can cause unpleasant side effects
139
Inhibition of MAO treatment for Parkinson’s?
Drugs which inhibit the action of MAO so any dopamine present can have a longer lasting effect
140
Stem cell treatment for Parkinson’s?
Skin cells are being used to produce IPSC’s which are then induced in vitro to develop into cultures of brain neurones.
These can be used to gain a better understanding of why these neurons die and could be used to treat PD
141
Drugs treating neurotransmitter-related diseases are ____ in structure to _______ and act as ____ or ____
Similar
Neurotransmitters
Agonists
Antagonists
142
Treatment of neurotransmitter-related disorders?
Agonist drugs
Antagonist drugs
Inhibitor drugs
144
What is an agonist?
A chemical that binds to specific receptors and stimulates post synaptic neurones in a pathway
145
Why do agonists do?
Mimic the action of neurotransmitters triggering the normal cellular response and promoting enhanced levels of nerve impulses
146
What’s an antagonist drug?
A chemical which binds to specific receptors and blocks receptor sites
147
What do antagonist drugs do?
Prevents the normal neurotransmitter from binding to receptor sites, resulting in a reduction of nerve impulses being transmitted
148
What do recreational drugs lead to changes in?
* Mood - more confident, happier, aggressive
* Cognitive thinking - poorer at problem solving + decision making
* Perception - misinterpretation of environment - sights colours etc
* Behaviour - stay awake longer, increased self confidence
149
How can recreational drugs interact with neurotransmitters?
* stimulate the release of natural neurotransmitters
* act as an agonist by initiating the action of a neurotransmitter
* act as an antagonist by binding with receptors and block the action of a neurotransmitter
* inhibit the reuptake of a neurotransmitter
* inhibit the breakdown of a neurotransmitter by an enzyme
150
Describe cocaine and what it does?
Produces feelings of well being and limitless energy
Induces hallucinations and leads to social withdrawal, depression an dependence
Inhibits dopamine reuptake and the pathway is overstimulated
151
Describe MDMA and what it does?
Users feel more alert and energetic
Can cause anxiety, panic attacks, paranoia and depression
Dancing for long periods under the influence can cause overheating and dehydration
Inhibits serotonin reuptake, promoting temporary heightened well being
152
Describe cannabis and what it does?
Acts as a pleasurable stimulant and then as a sedative
User may feel excited, restless and inhibited initially then drowsy and falls into a deep sleep
Heavy use can trigger schizophrenia
Cannabinoids bind to cannabinoid receptors which are normally occupied by a neurotransmitter which transmit impulses controlling muscles and regulation of pain sensitivity
153
Describe nicotine and what it does?
Highly addictive and chemicals are responsible for diseases such as cancer
Normally nicotinic acetylcholine receptors in brain are occupied with acetylcholine causing transmission of nerve impulses
Such transmission leads to an increase in dopamine, serotonin and noradrenaline
Nicotine mimics effect and increases activity of these nicotinic acetylcholine receptors resulting in euphoria, relaxation and eventual addiction
154
Describe alcohol and what it does?
A depressant, causes feelings of relaxation and good humour initially then loss of consciousness following excessive consumption
GABA receptors have an inhibitory effect and alcohol mimics this reducing feelings of anxiety
Can lead to elevated dopamine levels and person feels good temporarily as the reward system in the brain continued to be over stimulated
155
What is drug addiction also know as?
Sensitisation
156
What is drug addiction?
A chronic disease where the sufferer compulsively seeks the drug regardless of the consequences
The initial drug taking was voluntary but neural changes as a result of the addiction over ride self control
157
What does repeated use of a drug that acts as an antagonist do? (Drug addiction)
Continually blocks specific receptors preventing the normal neurotransmitter from acting on them
The nervous system compensated for the reduced stimulation by increasing the number of receptors and their sensitivity
This leads to addiction as the user craves more of the drug
158
What is drug tolerance also known as?
Desensitisation
159
What does repeated use of a drug that acts as an agonist do? (Drug tolerance)
Results in receptors being repeatedly stimulated
The nervous system compensates for overstimulation by reducing the number of receptors and their sensitivity
A larger dose of the drug is now required to produce the original effect
160
What is immunity?
The body’s ability to resist infection by a pathogen
161
What is a pathogen?
Any bacterium, virus or other organism that can cause disease
162
What’s a non specific immune response?
Works against any type of disease causing agent
163
What’s a specific immune response?
Works against a particular pathogen
164
Non specific chemical immune responses?
* tears and saliva
* mucus
* secretions from sweat and sebaceous glands
* stomach acid
165
Describe the immune response of tears and saliva?
Tears and saliva contain lysozyme which digests bacterial cells walls + destroys them
166
Describe the immune response of mucus?
Mucus traps micro-organisms which are swept up upward by cilia
167
Describe the immune response of secretions from sweat and sebaceous glands?
Secretions from sweat and sebaceous glands keep skin at a low pH so microbes cannot thrive
168
Describe the immune response of stomach acid?
Cells lining the stomach produce acid which destroys microbes
169
Non specific physical responses?
* skin
| * mucous membranes
170
Describe the immune response of skin
Skin is composed of densely packed epithelial cells and is found in the skin and inner lining of digestive + respiratory systems, offering physical protection against bacteria and viruses when it is intact
171
Describe the immune response of mucous membranes?
Mucous membranes linings the digestive and respiratory tract form a physical barrier
172
What is the 2nd line of defence for non specific immune responses?
Inflammatory response
Phagocytosis
173
What is the inflammatory response?
When the body is physically injured, cut or invaded by micro organisms, it triggers the inflammatory response, a localised defence mechanism
174
What are mast cells?
They are found throughout the body and contain histamine.
175
What does histamine cause?
Vasodilation of the arteries
Increased capillary permeability
176
Describe what happens with mast cells following injury?
1) Damaged mast cells become activated and release large quantities of histamine
2) Blood vessels in the area dilate
3) Capillaries in the area become more permeable
4) The area becomes red and inflamed
177
Increased blood flow and permeability of capillaries due to histamine leads to?
• the accumulation of phagocytes to the damaged tissue
| • accumulation of clotting elements to the injured area
Blood clots and tissue repair begins
178
What is a phagocyte?
A phagocyte is a motile white blood cell, can recognise pathogens by their antigens and will destroy pathogen ya by phagocytosis
179
Describe phagocytosis
Phagocyte engulfs the pathogen enfolding it within the membrane to form a vesicle
The cytoplasm of a phagocyte contains digestive enzymes - lysozyme sun vesicles called lysosomes
These fuse to the pathogen filled vesicle and destroy the pathogen
Dead bacteria and phagocytes accumulate at an infected area as pus
180
What are cytokines and what do they do?
Protein molecules released by phagocytes
They act as a signal causing more phagocytes to accumulate at the site of infection
181
What are antigens?
Proteins on the surface of cells that trigger on a specific immune response
182
2 types of lymphocytes?
B-lymphocytes
T-lymphocytes
183
Where are lymphocytes derived from and what to they develop into?
Lymphocytes are derived from stem cells in bone marrow
Some pass to the thymus gland and develop into T-lymphocytes
Others mature in the bone marrow and become B-lymphocytes
184
What do B-lymphocytes do?
* Produce antibodies against antigens leading to the destruction of a pathogen
* Produce memory cells capable of making antibodies in future
185
What are antibodies?
Y shaped protein molecule
Each arm has a receptor site specific to particular antigen on a pathogen
186
How do antibodies work?
Antibodies bind to antigens, forming an antigen-antibody complex, inactivating the pathogen which is then destroyed by phagocytosis
187
What is an allergic reaction?
Sometimes the immune system over reacts when B-lymphocytes respond to harmless substances (pollen, dust, feathers, penicillin)
This hypersensitivity in the form of an exaggerated (sometimes damaging) immune response is called an allergic reaction
188
What’s anaphylactic shock?
A life threatening reaction caused by an allergen that has been injected (bee venom) or consumed (peanuts)
The person is so allergic that mast cells secrete large quantities of histamine which triggers vasodilation and great loss of circulatory fluid to the tissues and a drop in blood pressure
Death can occur within minutes if not treated
189
How do inhibitor drugs work?
By preventing the removal of neurotransmitter from synaptic clefts by inhibiting enzyme action or reabsorption
190
What do T-lymphocytes do?
Destroy infected cells by recognising the antigens of pathogens on the cell membrane and inducing apoptosis
191
When does the T-lymphocyte become activated?
When the antigen receptor of a T-lymphocyte binds with the antigen on a pathogen
192
What does the activated T-lymphocyte produce?
* clones of activated T cells
| * memory cells capable of recognising the same foreign antigen in the future
193
What is apoptosis?
Programmed cell death
194
Describe apoptosis
Activated T-lymphocytes attach to infected cells and release proteins
The proteins diffuse into the cell causing the production of self-destructive enzymes which cause cell death
The dead cell remains are engulfed and digested by phagocytosis
195
Why are each person’s body cells different?
Because they posses a combination of cell surface proteins that is unique to that person
196
Any T lymphocyte with an antigen receptor that ___ __ _ ___ ___ _____ _____ is identified and destroyed by apoptosis
would fit a body cell surface protein
197
What is agglutination and what does it cause?
Clumping of red blood cells (caused by incompatibility between donor cells and recipients plasma)
Causes major blockage of small blood vessels
198
What causes autoimmune diseases?
Failure of the regulation of the immune system leads to T-lymphocytes responding to self antigens
199
Describe rheumatoid arthritis?
Causes chronic inflammation of the synovial membrane in joints
The membrane swells up, cartilage and bone are gradually destroyed and replaced by fibrous tissue
This can join the two bones together, making the joint immovable
200
Describe Type 1 Diabetes (auto immunity)
Insulin producing beta cells in the pancreas are attacked and destroyed by T-lymphocytes from the body’s immune system
Blood glucose levels cannot then be controlled
201
Describe multiple sclerosis
T-lymphocytes regard molecules on the myelin sheath as antigens
They attack + destroy the myelin sheath resulting in the ability of the nerve cells to transmit impulses being seriously impaired
202
What are memory cells?
Some cloned B+T lymphocytes survive long term as memory cells -
these destroy invading pathogens before the individual shows symptoms
203
What does the HIV virus do?
Attacks and destroys T-lymphocytes
204
How can you get HIV?
```
Via:
• unprotected sex
• passed from mother to baby
• sharing injecting equipment
• contaminated blood transfusions and organ transplants
```
205
What is AIDS?
A deficiency disease caused by HIV
206
How does HIV attack T lymphocytes?
By attaching to specific receptors on the T-lymphocyte and entering the host cell
207
HIV contains ___
RNA
208
Why does HIV need DNA and what does it do to produce it?
It needs DNA to transcribe the mRNA so it introduces an enzyme to bring about the reverse of normal transcription to produce viral DNA from viral RNA
209
How long can viral DNA lie dormant for?
Viral DNA is incorporated into host cells DNA and can lie dormant for years before directing synthesis of new viral particles
210
How do viral particles escape from the host cell?
By budding and infecting other cells
This causes the destruction and depletion of T lymphocytes
211
What happens as the number of T lymphocytes decreases due to HIV?
The person is susceptible to opportunistic infections such as pneumonia
At this point the person is suffering from AIDS
212
What is immunity?
Protection gained as a result of the person’s body producing its own antibodies
213
What’s naturally acquired immunity?
Person survives an infection by a pathogen
Their second exposure to the same antigen results in a secondary response
214
What is artificially acquired immunity?
Vaccination
215
What is a vaccination?
A form of immunisation where a weakened or inactive form of the pathogen is deliberately introduced into the body
216
What does a vaccine act as?
An antigen to initiate the immune response and create memory cells
217
What do memory cells do?
Initiate the secondary response of the person is exposed to the disease at a later date
218
Antigens used in vaccines can be?
* Inactivated pathogen toxins (tetanus)
* Dead pathogens (polio)
* Weakened pathogen (MMR)
* Parts of a pathogen (HPV)
219
Why is an adjuvant used in vaccines?
In a vaccine, the antigen is mixed with an adjuvant which makes the vaccine more effective + increases the immune response (but does not cause the disease)
220
When does herd immunity occur?
When a large percentage of the population is immunised
221
Herd immunity reduces?
Reduced the spread of diseases (the probability of non-immune individuals coming into contact with an infected individual is low)
The normal chain of infection is therefore disrupted
222
For herd immunity to be effective?
Only a minority of the population can be left unvaccinated
223
Which non vaccinated/ vulnerable sub groups does herd immunity provide protection for?
* Those who have a medical condition/ immune disorder
| * the elderly and new born babies who are too young to be vaccinated
224
What’s the herd immunity threshold?
The percentage of immune individuals in a population above which a disease no longer manages to persist
225
What does the value of herd immunity threshold depend on?
* the type of disease
* effectiveness of the vaccine
* population density
226
What are mass vaccination programmes designed to do?
Establish herd immunity for common diseases
227
Successful mass vaccination programmes?
TB
Polio
228
When do difficulties in mass vaccination programmes arise?
When widespread vaccination is not possible due to malnutrition and poverty (in the developing world)
When vaccines are reflected by a percentage of the population (in the developed world)
229
What is antigenic variation?
Some pathogens change their antigens (the antigens on their surface differ from the original strain)
Means memory cells are not effective against them
230
What does antigenic variation enable the influenza virus to do?
Avoid immunological memory and re infect a person
231
Why must at risk individuals be vaccinated every year with a new version of the influenza vaccine?
Antigenic variation - old vaccines ineffective against new strains
232
What are new vaccines and drugs required to undergo and why?
Medical trails to establish their safety and efficacy (produce the intended result) before they can be licensed for use
233
Describe phase 1 of a clinical trail
Small doses of treatment tested on a very small number (25-50) of volunteers to check that it is safe
234
Describe phase 2 of a clinical trail
Treatment tested on a large number (150-300) of people who have the illness to test if the treatment is safe and effective to find out what the optimum dose may be
235
Describe phase 3 of clinical trials
Treatment tested on a very large number (1000-2000) of people who have the illness using a randomised, placebo-controlled, double-blind protocol
236
Describe what happens if phase 3 of a clinical trial is successful
Results submitted and license sought to manufacture the new treatment
237
What is a placebo drug?
A drug with the same appearance as a new drug but lacking the active ingredient being tested
238
What is the point of placebo drugs?
This assesses the placebo effect where people feel better because they think they’ve been given a treatment
Allows a valid comparison to be made between test group and control group to assess effect of new treatment
239
What’s a double blind trail?
Neither the subjects nor the doctor know who is in which group (test or control) or who is receiving which treatment
This eliminates any bias affecting the results
240
What is randomisation?
Participants are randomly placed in groups by a computer whilst ensuring that group composition is as similar as possible in distribution of age, gender, etc
This reduces bias and experimental error from the trial
241
Why does using a very large sample size reduces experimental error?
The larger the group, the more confidence the researchers an have in the differences between the test and control groups
Also allows results to be compared to determine whether differences between the groups are statistically significant
242
Why would 16 year olds have a faster average time to complete a puzzle than 8 year olds?
As children get older they learn faster how to complete puzzles
243
What is herd immunity?
A large percentage of the population have been immunised
This means that there is a very low chance that non-immune individuals will come into contact with infected individuals
244
How can diseases of infancy be reduced in countries through community responsibility, other than by vaccination programmes?
Better medical care
Or
Clean water
245
Suggest how pulmonary TB (in the lungs) is transmitted between individuals?
Inhaled air/ droplet infection
246
Non pulmonary TB is often associated with HIV infection
Suggest a reason for this association?
HIV attacks lymphocytes reducing the ability of the immune system to respond to the bacterial infection
247
Name the part of the heart that regulates heart rate
Medulla
248
Describe how an impulse is transmitted from neuron A to neuron B
1) Vesicle releases neurotransmitter
2) Neurotransmitter diffused across synaptic cleft
3) Neurotransmitter binds with receptor
4) A minimum amount of neurotransmitter is required to transmit impulse
249
Describe the effect thy sensitisation has on the synapse and the consequences for the individual?
Effect - Increased number of/sensitivity of receptors
Consequences - leads to addiction
250
Explain why the heart continues to contract when both the sympathetic and parasympathetic nerves are blocked?
The SAN controls the heart beat and still sends impulses to the AVN
