Topic 8 Flashcards
what is a stimulus?
any change in the internal or external environment
what are receptors?
cells or proteins on a cell surface membrane that detect a change
what are effectors?
cells that bring about a response to a stimulus, to produce an effect
give two examples of effectors
muscle cells and cells in the pancreas
how do receptors communicate with effectors?
via the nervous system or hormonal system
how does the nervous system send information?
as electrical impulses
what are the 3 main types of neurones?
sensory, motor and relay neurones
what is the function of a sensory neurone?
transmits electrical impulses from the receptors to the central nervous system
what is the function of a motor neurone?
transmits electrical impulses from the central nervous system to effectors
what is the function of a relay neurone?
transmits electrical impulses between the sensory and the motor neurones
what is the process of a mammal responding to dim light?
stimulus- dim light
receptors- photoreceptors in eyes detect lack of light
CNS- processes the information
effector- radial muscles in iris are stimulated by motor neurones
response- radial muscles contract to dilate pupils
what is the process of a mammal responding to bright light?
stimulus- bright light
receptors- photoreceptors in eyes detect bright light
CNS- processes information
effector- circular muscles in iris are stimulated by motor neurones
response- circular muscles contract to constrict pupil
what is the reflex arc?
stimulus, receptors, sensory neurone, relay neurone, motor neurone, effector (muscles/glands), response
what is a gland?
a group of cells that are specialised to secrete a useful substance, such as a hormone
what can stimulate a gland to secrete a hormone?
glands stimulated by change in concentration of specific substance (sometimes another hormone) or by electrical impulses
what does the hormonal system use for communication?
chemicals
what does the nervous system use for communication?
electrical impulses
which is faster, nervous or hormonal communication? Why?
nervous as electric impulses are fast and hormones travel at ‘speed of blood’
does nervous or hormonal communication have widespread response? Why?
hormonal has widespread response as target cells can be all over the body, nervous has localised response
why does hormonal communication have a long-lived response?
hormones aren’t broken down very quickly
why does nervous communication have a short-lived response?
neurotransmitters removed quickly
what type of neurones are in the brain?
unmyelinated neurones
what are the 4 types of tissues in mammals?
connective, epithelial, nervous, muscle
what are the 3 types of muscle tissue?
skeletal, cardiac, smooth
what is included in the central nervous system?
brain and spinal cord
what is included in the peripheral nervous system?
all neurones not in the brain and spinal cord
what is a nerve?
a bundle of neurones
what 2 systems make up the peripheral nervous system?
motor and sensory systems
what 2 systems make up the motor system?
somatic nervous system and autonomic nervous system
what is the somatic nervous system?
made of motor neurones
a single motor neurone transports impulses from CNS to effectors
voluntary movements
what is the autonomic nervous system?
regulates involuntary processes
involves multiple neurones linked with a ganglion
what is a ganglion?
a collection of neuronal bodies (core section of a neurone) found between neurones in the peripheral nervous system
what 2 systems make up the autonomic nervous system?
sympathetic (flight or flight) and parasympathetic (rest and digest)
what are the roles of the hypothalamus?
controls thermoregulation
secretes hormones which control the pituitary gland and others which control the water potential of the blood
what is the role of the posterior lobe of the pituitary gland?
secretes the hormone ADH which controls osmotic balance, blood pressure and kidney function
what is the role of the cerebrum?
2 hemispheres and 4 lobes:
frontal, parietal, occipital and temporal
decision making, sensory perception, vision and auditory information
what is the role of the cerebellum?
balance, posture and fine tuned movement
what is the function of the anterior lobe of the pituitary gland?
secrete hormones such as LH and FSH
what is the function of the medulla oblongata?
contain cardiac centre which controls heart rate
what are nodes of ranvier?
gaps between the Schwann cells in the myelin sheath
what are the Schwann cells?
cells that make up the myelin sheath
what are the Schwann cells made of?
lipids
where is the cell body of a motor neurone?
at the start of the neurone- in the CNS
where is the cell body of a sensory neurone?
in the middle of the neurone- in the PNS
where is the cell body of a relay neurone?
in the CNS
compare the axons of a sensory and motor neurone
sensory- shorter motor- longer
compare the dendrites of a sensory and motor neurone
sensory- longer motor- shorter
what is a similarity between a motor and sensory neurone?
both are myelinated
what is saltatory conduction?
the quick conduction which occurs when the neurones have a myelin sheath (the impulse ‘jumps’ from node to node)
why are most neurones in the brain unmyelinated?
it would be a waste of energy for the brain to form the lipids
what are concentrated in the nodes of ranvier?
sodium ion channels
where does the depolarisation of a neurone occur?
at the nodes of ranvier
how does an impulse ‘jump’ from node to node?
the neurone’s cytoplasm conducts enough electrical charge to depolarise the next node
what are the 3 stages of an action potential?
depolarisation, repolarisation, hyperpolarisation
what is happening at resting potential?
inside the cell is negative compared to the outside
resting potential is -70mv
more sodium ions outside the cell, ion pump uses active transport to move sodium ions out and creates electrochemical gradient
there is an even amount of potassium ions either side of the membrane as the membrane is permeable to potassium
what happens during depolarisation?
stimulus
some voltage gated sodium ion channels open and sodium moves down electrochemical gradient (into the cell)
threshold of -55mv reached
all sodium ion channels open
potential difference reaches +40
what happens during repolarisation?
sodium ion channels close and potassium voltage gated ion channels open
potassium ions diffuse down the concentration gradient and out of the cell
(as there are more potassium ions inside than outside of the cell)
what happens during hyperpolarisation?
the voltage gated potassium ion channels are slow to close which creates a slight ‘overshoot’ and too many potassium ions leave the cell
potential difference reaches -90mv
sodium-potassium ion pump uses active transport (and ATP) to move 3 sodium ions out and 2 potassium ions in
what is the refractory period?
the period after an action potential when the ion channels are still recovering and cannot be made to open so that section of the membrane cannot be excited again straight away
what 2 things does the refractory period cause?
ensures that action potentials are unidirectional and only travel in one direction
acts as a time delay so that action potentials don’t overlap but pass as discrete (separate) impulses
what does a bigger stimulus cause?
more frequent impulses
how do local anesthetics work?
bind to sodium ion channels in the membrane of neurones and stops them from opening. This prevents depolarisation and therefore an action potential form occurring
what are the stages of an impulse crossing a synapse?
- impulse triggers presynaptic membrane to depolarise
- voltage gaited calcium ion channels open and calcium enters the presynaptic knob
- vesicles containing neurotransmitter move closer to the presynaptic membrane and fuse to the presynaptic membrane
- through exocytosis the neurotransmitter is released into the synaptic cleft
- neurotransmitter diffuses across cleft and bind to specific receptors on the postsynaptic membrane
- this triggers depolarisation on the postsynaptic membrane
- sodium voltage gated ion channels open and sodium ions enter the cell
- action potential continues down postsynaptic membrane (if its a neurone)
- neurotransmitter is broken down by enzymes in the cleft or taken by reuptake into the presynaptic membrane or diffuse back to the presynaptic membrane
what could be postsynaptic?
effector: neurone, muscle, gland
what are the 2 types of light receptors/photoreceptors in the retina?
rod and cones cells
how do rod and cone cells act as transducers?
convert light energy into an electrical nerve impulse
how many rod cells signal to one bipolar neurone?
three
how many cone cells signal to one bipolar neurone?
one
what is the name of the light sensitive pigment in rod cells?
rhodopsin
what happens to rhodopsin when it is hit by light?
it is bleached/ broken down into opsin and trans retinal
why are rod cells very sensitive to low light intensities?
rhodopsin doesn’t take much energy to be broken down so is broken down by low intensity light
summation increases the chance of the threshold being reached
in low light intensity why is the image in the brain low resolution?
the brain doesn’t know which rod cell the impulse has come from- only which bipolar cell
do rod cells produce coloured or black and white images?
black and white
do cone cells produce coloured or black and white images?
coloured
why do cone cells only respond to high intensity light?
no summation so less chance of the threshold being reached
iodopsin requires high light intensity to be broken down
what is the name of the light sensitive pigment in cone cells?
iodopsin
where is the highest concentration of cone cells found?
in the fovea where light is directly focused by the lens
what happens in a rod cell in the dark?
sodium ions diffuse in though open ion channels and are pumped out via active transport
inside is negative compared to outside- depolarised
calcium ions move into the rod cell
inhibitory neurotransmitter glutamate released
glutamate inhibits action potential in postsynaptic membrane (on bipolar cell)
no information goes to the brain
what happens in a rod cell in the light?
rhodopsin hit with light
rhodopsin broken down into opsin and trans-retinal (bleaching)
opsin binds to membrane causing sodium ion channels to close
sodium ions cannot diffuse back into the cell
outside of the membrane has more sodium ions- membrane is hyperpolarised
calcium ion channels not triggered to open
neurotransmitter (glutamate) not released
depolarisation/action potential occurs as sodium ion channels open
what are the 4 problems with studying the brain?
skull (difficult to ‘see’ through), complex interconnections, fragile, blood brain barrier
what does CT stand for?
computerised tomography
what does a CT scan use?
x-rays
how do different tissues look in a CT scan?
denser tissue absorbs more radiation and so shows lighter
do CT scans show structures or functions?
structures
what are the advantages of a CT scan?
cheaper
what are the disadvantages of a CT scan?
low resolution, black and white, risk of damage from radiation (although small)
what does MRI stand for?
magnetic resonance imaging
what does an MRI use?
radio waves and magnetic fields
how do different tissues look in an MRI scan?
tumour cells show as lighter than healthy tissue
does an MRI scan look at structure or function?
structure
what are the advantages of an MRI scan?
higher resolution than a CT, shows exact size and location of tumour, no ionising radiation used so no risk of damage
what are the disadvantages of an MRI scan?
black and white, more expensive than a CT, no people with pacemakers as no metal
what does fMRI stand for?
functional magnetic resonance imaging
what does fMRI use?
radio waves and magnetic fields
how do different tissues look in an fMRI scan?
more oxygenated blood flows to active areas, molecules in the oxygenated blood respond differently to the magnetic field and show as lighter/coloured
does an fMRI look at structure or function?
both
what are the advantages of fMRI?
looks at structure and function, high resolution, coloured image
what are the disadvantages of fMRI?
expensive
what does PET stand for?
positron emmission tomography
what do PET scans use?
radioactive tracers
how do different tissues look in a PET scan?
area with high amounts of tracer show brighter/more coloured
does a PET scan look at structure or function?
both
what are the advantages of PET scans?
very detailed, show if areas are active or inactive
what are the disadvantages of PET scans?
expensive
which scans form live images and which don’t?
fMRI and PET scans do, MRI and CT don’t
how do animal experiments show nature affects brain development?
genetically similar rats in same environment showed different brain developments
how do animal experiments show nurture affects brain development?
rats reared in isolation have similar brain abnormalities to those with schizophrenia
how do twin studies show nature affects brain development?
twins have similar IQ scores
how do twin studies show nurture affects brain development?
no differences in reading ability between identical and non-identical twins
how do cross-cultural studies show nature affects brain development?
similarities between different cultures may be due to genetics
how do cross-cultural studies show nurture affects brain development?
any differences between different cultures may be due to different upbringings
how do brain damage studies show nature affects brain development?
after brain damage, if a characteristic doesn’t develop (as nurture isn’t having an effect)
how do brain damage studies show nurture affects brain development?
after brain damage, if a characteristic does develop the upbringing is why the characteristic is occurring
what are plant hormones called?
growth factors
define tropisms
responses by plants to a directional stimuli
what is a positive tropism?
growth towards the stimulus
what is a negative tropism?
growth away from the stimulus
what is phototropism?
a plant’s growth response to light
what is geotropism?
a plant’s growth response to the earth’s gravitational field
name a type of auxin
IAA
where is auxin made?
in tips of stems and roots (meristems)
how does auxin move around the plant?
diffusion, active transport or via the phloem
what is the effect of IAA in the roots?
high concentrations inhibit growth
what is the effect of IAA in the shoots?
causes cell elongation
what are the 4 growth factors in plants?
auxins, ethene, gibberellins, ABA
what is the role of auxin?
cell elongation in shoots and inhibits growth in roots
what is the role of gibberellin?
stimulates cell division and differentiation
what is the role of ethene?
stimulates fruit ripening and flowering
what is the role of ABA?
involved in leaf falling
where do auxins gather in phototropism?why?
on the shaded as sunlight breaks down auxin
what happens in shoots during phototropism?
auxins gather on shaded side, auxin causes growth, more growth on shaded side, shoot bends towards light
what happens in roots during phototropism?
auxins gather on shaded side, auxins inhibit cell growth, more growth on sunny side, root bends away from light
why does cell elongation occur?
vacuole grows and cell wall elongates to cope with increasing pressure
which part of the plant has the most growth?
the meristem
where do auxins gather in geotropism?
on the lower side
what happens in shoots during geotropism?
auxins gather on lower side, auxins cause growth, more growth on lower side, shoot grows upwards
what happens in roots during geotropism?
auxins gather on lower side, auxins inhibit growth, more growth on upper side, root grows downwards
what are the 6 stimuli plants can respond to?
Light (direction, intensity& length of exposure), gravity, touch, temperature, water, chemicals
what are photoreceptors in plants called? what do they do?
phytochrome (absorb light)
what are the 2 types of phytochrome?
PR and PFR
what is the far red phytochrome?
a transcription factor
describe PR
absorbs red light and converts to PFR during the day, inactive phytochrome
describe PFR
absorbs far red light and converts to PR at night, active phytochrome
what reaction involving phytochrome happens at night?
PFR absorbs far red light and converts into PR slowly
what reaction involving phytochrome happens during the day?
PF absorbs red light and converts into PFR rapidly
what is the wave length of red light?
660
what is the wave length of far red light?
730
what is the effect of PFR on short day plants?
inhibits flowering
when do short day plants flower?
when days are short/nights are long and interrupted
what is the effect of PFR on long day plants?
promotes flowering
when do long day plants flower?
when days are long/ nights are short
what controls the amount of PR/PFR?
the length of darkness
define habituation
the reduced response to an unimportant stimulus after repeated exposure over time
why is habituation beneficial?
means animals don’t waste energy responding to unimportant stimuli, they can spend more time doing other activities essential for survival (feeding)
what are the stages of habituation?
repeated exposure means less calcium ions enter the presynaptic neurone, less neurotransmitter released, less receptors stimulated, less sodium ion channels open, less chance of threshold being reached, less action potentials reach effector
what neurotransmitter is involved in depression?
serotonin
what causes depression?
lack of serotonin
why does lack of serotonin cause depression?
serotonin is involved in pathways which control mood, emotions, sleeping and walking
give 4 symptoms of depression
tiredness, hopelessness, low self esteem, low energy levels
what is the effect of ecstasy?
blocks re-uptake channels and so keeps serotonin in the synaptic cleft- keeps triggering action potentials on the postsynaptic membrane
what are the treatments of depression?
MAOI, SSRIs (selective serotonin reuptake inhibitors), Prozac
what are the effects of MAOI?
MAOI inhibits the enzyme which breaks down serotonin and so the concentration of serotonin in the synaptic cleft remains high
what are the effects of SSRIs?
selective serotonin re-uptake inhibitors- prevent the re-uptake of serotonin at synapses
what are the effects of Prozac?
inhibits re-uptake channel proteins on presynaptic membrane, so more serotonin left in synaptic cleft
what neurotransmitter is involved in Parkinson’s?
dopamine
what causes Parkinson’s?
lack of dopamine due to death of dopamine producing cells
give 3 symptoms of Parkinson’s
tremors starting in one hand, changes to speech, difficulties with balance
why is Parkinson’s so difficult to treat?
80% of damage to cells occurs before diagnosis, dopamine cannot cross blood brain barrier
what are the treatments of Parkinson’s?
(no cure but palliative drugs available)
L-Dopa, dopamine agonists, MOAB inhibitors, Deep Brain Stimulation
what are the effects of L-Dopa?
can cross blood brain barrier and is converted into dopamine by an enzyme, only 5-10% reaches brain with the rest being metabolised into dopamine elsewhere causing harmful side effects, given intravenously, results vary
what are the effects of dopamine agonists?
acts in similar way to dopamine, binds to postsynaptic receptors and triggers action potentials in the postsynaptic membrane
what are the effects of MOAB inhibitors?
inhibit enzymes which break down dopamine so concentrations of dopamine in the synapse remain high (levels will still reduce as Parkinson’s develops)
what are the effects of deep brain stimulation?
electrodes implanted into brain, shocks mimic action potentials which release dopamine
how do neurotransmitters get out of the postsynaptic receptors?
enzymes
how do neurotransmitters get back into the presynaptic knob?
through re-uptake transporters (channel proteins) via facilitated diffusion
What is the human genome project?
A 13 year project to sequence all of the DNA to find the order of the bases (and then genes) in an organism (includes introns and exons)
Give 3 disadvantages of the HGP
Medication is more expensive, so may create a two tiered health service
Information may be used by insurance companies to discriminate against people who are more likely to suffer from illnesses
telling patient only drug available won’t work may have psychological consequences
Give three uses of the human genome project
Data used to identify genes and proteins involved in disease
Information used to create new drugs that target identified proteins
genetic testing to identify sufferers and carriers
What is a genome?
all the DNA in an individual
what are personalised medicines?
targeted drugs to treat a variety of human diseases in individuals with different alleles
what is pharmacogenetics?
the study of an individual’s genome to predict how they will respond to a drug treatment
how do target drugs work?
HGP identifies which alleles cause disease, location of this allele is found, drugs target specific identified allele, drug prevents translation to stop allele being expressed, harmful protein not produced
what is recombinant DNA?
the DNA which includes DNA from both organisms- in GMO
why are bacteria used in genetic modification?
they produce clones and they reproduce very quickly
what are the steps of genetically modifying micro-organisms?
plasmid extracted from bacterial cell, restriction enzyme used to cut plasmid, same restriction enzyme used to isolate wanted gene from human DNA, DNA ligase is used to insert gene into plasmid, plasmid packaged back into bacterial cell, cell division by binary fission, useful protein produced and can be extracted (insulin in waste product in bacteria), bacterial cells destroyed
where do restriction enzymes cut?
at specific loci
what additional gene is added to the bacteria to ensure that only bacteria which have successfully modified are used?
an antibiotic resistant gene, the bacteria are then exposed to the antibiotic but if the modification has been successful the bacteria will survive
what is genetic modification?
a technique which removes a gene that codes for a desired characteristic from one organism and transferring the gene into another organisms where the desired characteristic is then expressed
what are vectors?
what is used to transport the gene into the second organism (plasmid or bacteria)
what are the steps of genetically modifying a plant?
plasmid extracted from bacterial cell, restriction enzyme used to cut plasmid, same restriction enzyme used to isolate wanted gene from human DNA, DNA ligase is used to insert gene into plasmid, plasmid packaged back into bacterial cell, bacteria used to infect plant cells (bacteria is the vector)
how can animals be genetically modified?
gene that codes for desired protein is injected into the nucleus of a zygote, zygote implanted into uterus, where it develops into an adult animal, protein then can be purified (for example from the milk)
give 4 advantages of GMOs
crops can be modified to increase yield
crops can be modified to be resistant to pests so pesticide usage is reduced
vaccines can be produced by GM plant tissue which wouldn’t have to be refrigerated
diseases can be treated with human proteins (produced by GMOs) instead of with animal proteins reducing the risk of allergic reactions
give 4 disadvantages of GMOs
there may be transmission of genetic material- if herbicide resistant crops interbreed with wild plants, ‘superweeds’ could be created
wrong to genetically modify animals for human benefit
there may be longterm unforeseen circumstances on using GMOs in food
GMOs usually grown in large fields creating monocultures which are bad for biodiversity
