Biology - Unit 5 Flashcards
What two sources of evidence have led to our understanding of how the brain works?
Animal studies and studying human brains
How have brain diseases increased understanding of the brain?
What effect damage to different parts of the brain have
How are animals used for brain studies?
Effect if removing parts of the brain
Effect of artificially stimulating part of the brain
How the brain develops
What does the frontal lobe do?
Emotions
Speech
Decision making
Rational thought
What does the cerebrum do?
Integrates impulses in
Function of the parietal lobe
Memory and recognition Calculation Movement Sensation Orientation
Occipital lobe function
Eyesight
Temporal lobes function
Language Hearing Smell Auditory information Memory
Hypothalamus function
Homeostasis
Autonomic nervous system control
Pituitary gland function
Keeping water balance by releasing diuretics
Releases hormones like LH and FSH
Basal ganglia function
Motor control
Corpus callosum function
Connects the two hemispheres
Cerebellum function
Body control
Motor memory
Posture and balance
Medulla oblongata function
Breathing
Heart rate
Digestion
Sorts information
Olfactory bulb function
Sense of smell
Brain stem function
Joins to the spinal cord
How do CAT scans work?
Thousands of small X-ray beams passed through
Beam attenuated by tissue density
Data put together
What does attenuated mean?
Reduced in strength
How does MRI work?
Magnetic fields and radio waves passed through
Different tissues respond differently
How do fMRI scans work?
Monitors uptake of oxygen as deoxyhaemoglobin absorbs signal
Advantages of fMRI
Constant picture
Can see movement of oxygen
How do ultrasound scans work?
High frequency sound waves
How do X-rays scans work?
X-rays passed through body
Dense matter reflects them
What experiment did Crowley and Katz perform?
Injected newborn ferrets with radioactive tracers
Tracers moved from one eye and found in specific bands in visual cortex
Conclusions of Crowley and Katz experiments
Neurones ordered in ocular dominance columns from birth
Experiments of Horton and Hocking
Prematurely delivered three monkeys
Kept in dark with radioactive tracer in eye
Found fully developed ocular tracers by time would have normally born
Horton and Hocking conclusions
Ocular dominance columns formed before birth
Visual cortex development due to genetic factors initially
Experiments of Hubel and Weisel on kittens and monkeys
Stitched shut one or both of animals eyes at different ages and for different lengths of time
Hubel and Weisel findings
Shut one eye at one week old and uncovered eye worked fine - swap eyes after a few months and animal could not see
If did same at 4 months old, no effect
Findings by Hubel and Weisel
Critical windows of development
What are critical windows of development?
Periods of time during which vital connections are made in the brain in response to specific stimuli
Visual cortex development
Initially, dendrites for both eyes overlap
If both eyes used as much, columns form of equal size for each eye (No overlap)
If one eye used more, its columns are larger
What has been found from studying newborn babies brains?
There is discrimination towards paying more attention to biological movement than non-biological
The younger you are the better your face recognition is
Severe sensory deprivation can cause improper brain development
Polks research shows
Brain patterns more similar in identical twins than non for face/place recognition
Little difference with regards to word and letter response
Work of Polk
Presented fraternal and identical twins with various scrambled images including letters and faces
What is species-characteristic behaviour?
Innate behaviour
Seen in every member of a species
Not learned
What is individual-characteristic behaviour?
Learned behaviour
Singular members who learn from experience
What is habituation?
Animal starts ignoring repeated stimulus as no punishment nor reward
Gills of animal stop retreating when touched
What are conditioned reflexes?
Learning to associate new stimuli with an existing unconditioned reflex
Pavlov’s dogs
What is trial-and-error (operant) learning?
When an animal learns to associate a piece of trial behaviour with a reward or punishment so repeat or not
What is imprinting?
Young animal identifies with another organism and follows it around and relates to other similar objects
What is exploratory (latent) learning?
Animal explores new surroundings and learns them without any reward or punishment
What is insight learning?
Based on thought and reasoning
Once problem solved, the solution is remembered
How can habituation be shown using a land snail?
Poke it and its antennae withdraw
Takes less time to take them out again as the number of pokes increase
What is the cause of Parkinson’s?
Nerve cells which produce dopamine die so movement slows as dopamine allows messages to be sent to the brain
What are the risk factors of Parkinson’s?
Genetics Toxins Herbicides Head trauma Stroke Age
Why is Parkinson’s difficult to treat?
We do not know the risk factors or what causes the dopamine-producing cells to die
What are the symptoms of Parkinson’s?
Main symptoms:
Tremors
Slow movement
Stiff and inflexible muscles
Others:
Fatigue
Dementia
Depression
How does L-Dopa work to treat Parkinson’s?
It is converted into dopamine in the brain so more dopamine will be produced
What are the benefits of L-Dopa being used to treat Parkinson’s?
Greatly relieves stiffness and slowness of movements
Can be combined with carbidopa to improve action and reduce side-effects
What are the problems with using L-Dopa to treat Parkinson’s?
Less effective after 4-5 years as brain cells continue to die
Side effects:
Dyskinesia- muscle spasms
Low blood pressure
Arrhythmia
How do dopamine agonists act to treat Parkinson’s?
Bind to dopamine receptors in brain synapses and mimic action of dopamine
What are the benefits of using dopamine agonists to treat Parkinson’s?
Last longer in the brain than L-Dopa
Effectiveness does not wane over time
What are the problems with using dopamine agonists to treat Parkinson’s?
Not as effective as L-Dopa
Cause similar side-effects to L-Dopa
Can cause problems in controlling impulsive and compulsive behaviour
How do MAOB inhibitors work?
Block the action of MAOB which breaks down dopamine
What are the benefits of MAOB inhibitors?
Slows loss of dopamine
Can be used to make L-Dopa last longer or reduce amount needed
What are the problems with MAOB inhibitors?
When combined with L-dopa:
Dyskinesia
Hallucinations
On own:
Headache
Depression
Aching joints
What are the psychological symptoms of clinical depression?
Continuous low mood Feeling hopeless Low self-esteem Guilt ridden Irritable Anxiety
What are the physical symptoms of clinical depression?
Slow speaking or slow movement Change in appetite/weight (Usually decreased) Constipation Unexplained aches and pains Loss of libido Disturbed Sleep
What is the neurotransmitter involved in depression?
Serotonin
What is the role of serotonin in Depression?
Low levels result in fewer impulses so reduced brain activity. Low levels related to depression
What are the treatments for Depression?
Talking therapies Antidepressant drugs: -SSRIs inhibit re-uptake proteins -TCAs increase levels of serotonin -MAO inhibitors prevent neurotransmitter breakdown Ecstasy
What are the effects of Prozac at synapses?
Inhibits re-uptake proteins
More serotonin in synaptic cleft
More impulses travel
Symptoms reduced
What is the effect of ecstasy on the concentration of serotonin in the synaptic cleft?
Greater concentration as the re-uptake proteins are inhibited
How does ecstasy work to inhibit the re-uptake proteins?
Similar shape to serotonin so blocks them off
Why does taking ecstasy produce a high?
More serotonin in the synaptic cleft
Limbic system stimulated more
Feeling of reward
What is pharmacogenomics?
The study of how a persons genetics affect their response to drugs
What is the purpose of pharmacogenomics?
Can tailor drugs to specific peoples genes so that it has maximum effect and minimum side-effects
What are the responses to drugs?
Full response - Beneficial and non-toxic
Partial response - Beneficial but toxic
Non responsive - Not beneficial but non-toxic
Severe adverse reaction - Toxic and not beneficial
What factors influence drug response?
Gender Age Weight Diet Genetics Co-medication Environmental agents (E.g. Smoking) Disease
How important are genetics in drug response?
Account for between 20-95% of variation in response
What are the stages of drug action in the body?
Absorption Distribution Target interaction Metabolism Excretion
What are the two main gene groups involved in drug response?
Pharmacokinetic - Affects how the drug is handled by the body (E.g. Drug metabolising enzymes)
Pharmacodynamic - The drugs effect on the body (E.g. Receptors)
What are SNPs?
Single nucleotide polymorphisms
Genetic variants that affect a drugs action
Haplotypes - Combinations of related SNPs
How is pharmacogenomics enhancing the treatment of cancers?
Drugs that target the genetics of cancer cells to reduce toxicity and increase efficacy
How does Herceptin act to combat cancers?
Targets the chemical which causes massive growth
Block growth factors
Targets Her2 proteins on cancer cells
Why is Herceptin not perceived to be truly based on pharmacogenetics?
Targeted for tumour cells genetics not persons genome
What is efficacy?
Maximum beneficial response a drug can produce
% of recipients who show a therapeutic response at a given dose
What is toxicity?
The extent to which a drug has adverse side effects
% of recipients who show adverse side effects
What is the optimal dose range of a drug?
That at which efficacy is greatest and toxicity lowest
Why will pharmacogenomics not replace proper clinical management?
Need to choose best drug based on other factors as well
What are the benefits of tailoring drugs?
More effective
Lower dosage needed
Less side-effects
Where can pharmacogenomics save lives?
Minimising deaths due to severe adverse reactions
Why are microbes frequently used in genetic engineering?
Easy and cheap to culture
Reproduce rapidly
Easily identified
How do scientists know which microbes have taken up new genes?
Incorporate antibiotic resistance into new genes
Only ones with new genes survive antibiotics
What were the problems with previous methods of getting insulin?
Got from animals
- Immune system attacked the insulin
- Supply relied on animals being slaughtered
What is humulin?
Pure human insulin produced by bacteria
How is humulin produced?
One of each of the two polypeptide chains inserted into two bacteria using vectors
How is proinsulin production different to humulin production?
Only requires one type of bacteria while humulin requires two
What is the problem with using prokaryotes for drugs?
Cannot make complex human proteins
What is the use of bananas in GMOs?
Bananas are being developed which contain vaccines or vitamins
What is a crown gall?
A tumour which appears on a plant
What is the use of crown galls in transgenic plant technology?
It forms on the plant and can be taken and cultured and used to produce new plants containing the genes
What is the method of transgenic plant creation?
Ti plasmid removed from A. Tumefaciens bacterium
Gene to be carried inserted into plasmid
Plasmid returned to bacterium
Bacterium inserted into plant
Crown gall develops on plant which can be taken and cultured
What is a tropism?
A growth in response to stimulation
What are the stages of plant growth through mitosis?
Division - Mitosis Assimilation - New material brought in Elongation - Vacuoles develop -Cellulose wall stretches -Large central vacuole forms
Where does the most plant growth occur?
At the meristems (Just behind stem and root tips)
What are short-day plants?
Plants that flower when nights are long and days are short
What are long-day plants?
Plants that flower when nights are short and days are long
What is photoperiodism?
A plants ability to flower in response to changes in the photoperiod (Relative lengths of day and night)
What are day-neutral plants?
Plants whose flowering is unaffected by the lengths of the day and night
What is the environmental cue for flowering?
Length of darkness
What was the work by Hamner and Bonner with regard to critical periods?
Long-day plant can flower if in a short day, the long night is interrupted by a flash of light
What are the effects of red light on plant germination?
Inhibits short-day
Stimulates Long-day
Stimulates seed germination
What are the effects of far-red light on plant germination?
Inhibits seed germination
Inhibits long-day
Stimulates short-day
What is the photosensitive pigment involved in plant germination?
Phytochrome
How is Pfr converted into Pr?
Darkness - Slow conversion
Far-red light - Rapid conversion
How is Pr (P660) converted into Pfr (P730)?
Daylight
White light
Red light
What is etiolation?
Rapid growth in an attempt to reach light
What is the effect of Pr build-up/darkness on plant growth?
Tall and thin Small, pale leaves Long internodes Fragile stems Little chlorphyll
What is the effect of Pfr build-up on plant growth?
Green leaves Chlorophyll formation Thick Strong stem Shorter internodes
What did the experiments which proved the existence of florigen involve and show?
All but one leaf covered, entire plant flowers - Chemical produced which travels across plants
Only flowers if exposed leaf left in place for time - Takes time to synthesise chemical and travel it
Flowers if light-induced plant grafted on - Moves from leaf into plant
What were the experiments which proved the existence of auxin?
Darwin: -Covering apex -Removing apex Boysen-Jenson: -Effect of inserting mica barrier unilaterally Paal: -Tip replaced off-centre Went: -Tip incubated on gelatin block. Block replaced off-centre
What is IAA?
The first auxin discovered
What is an auxin?
The growth substance involved in phototropisms
How are neurones adapted for their function?
Long and thin - Take up little space but reach where needed
Not bound to other neurones - Can make and break connections
Flexible - Make connections easily
Chemical messengers to cross synapses
What is the difference between an axon and a dendron?
Axons carry impulses away from the nerve cell body while dendrons carry them towards it.
What is the structure of a motor neurone?
Cell body with dendrites
Axon
Synaptic bulbs
Effector
What is the structure of a sensory neurone?
Receptor Dendrites Dendron Connection to Cell body Axon Synaptic bulbs
What is the structure of a relay neurone?
Dendrites Dendron Cell Body Axon Synaptic bulbs
What is the structure of a myelin sheath?
Schwann cell wrapped around axon multiple times
Cytoplasm and nucleus on outside
Node of Ranvier between adjacent ones
Why are myelin sheaths important?
Protect nerves from damage
Speed up transmission of nerve impulse
What was the method used to discover how neurones work?
Took giant squid axons
Electrode filled with conducting solution inserted
Electrode attached with wire to amplifier
Two electrodes, one inside axon and one outside detect voltage
Difference amplified and displayed
What is the resting potential of an axon?
-70mV
How is the resting potential of an axon maintained?
Na+/K+ pump creates concentration gradient
K+ channel allows diffusion out
What is the action potential of an axon?
+40mV
How is an action potential formed?
Na+ channels open
K+ channels close
What are the stages of the refractory period?
Absolute refractory period - Impossible to re-stimulate
Relative refractory period - Threshold has been raised
What is an axons refractory period?
Its recovery time following an action potential
How is an action potential conducted along a nerve fibre?
The change in potential difference in one section due to the action potential causes a change in potential difference and therefore an action potential in the adjacent section
What is saltatory conduction?
The jumping of a nerve impulse from node to node along a myelinated nerve fibre
How are impulses transmitted across synapses?
Calcium ions flow in Vesicles fuse to pre-synaptic membrane Neurotransmitter (Acetylcholine) released into synaptic cleft Neurotransmitter fuses to receptors Na+ flows in EPSP or IPSP set up Cholinesterase breaks down acetylcholine Acetylcholine re-absorbed
What is an EPSP and IPSP?
EPSP (Excitatory post-synaptic potential) - Inside of post-synaptic membrane becomes more positive than resting potential
IPSP (Inhibitory post-synaptic potential) - Inside of post-synaptic membrane becomes more negative than resting potential
What is spatial summation?
Multiple action potentials arrive at a synapse at once
What is temporal summation?
Two action potentials from the same fibre arrive slightly after one another
What is facilitation?
Where multiple small impulses add together to create a larger one which can overcome the threshold
What is accommodation?
When neurones stop responding to a repeated stimulus
What is a primary receptor?
A dendrite