topic 8 exam qs

• EQ explain how increased sweating is involved in the regulation of body temperature

  -heat energy from blood in capillaries

  -absorbed by sweat

  -used to break H bonds in water

  -latent heat

  -so water evaporates

  -taking heat from the body
• EQ describe the process that occurs at a synapse that leads to habitution

  -repeated stimulus decreases sensitivity of pre synaptic membrane

  -so fewer Ca2+ ions move into presynaptic neurone

  -so fewer vesicles move towards the presynaptic membrane

  -so less neurotransmitter released

  -action potential less likely to occur in post synaptic membrane
• conclusion of habitation practical


  -with repeated stimulation, calcium ion channels in the presynaptic membrane become less responsive

  =less calcium ions cross the membrane into the presynaptic sensory neurone

  -as a result, fewer transmitters are released into the synaptic cleft

  -this means that an action potential across the post synaptic membrane is less likely

  -fewer action potential are produced in the post synaptic motor neurone so less of a response is observed

  -after a certain number of trials the snail should become unresponsive
• method for habituation practical

  1. collect one snail and place on a clean firm surface. allow snail to acclimatise to new surroundings and allow it to fully emerge from shell2. dampen a cotton wool bud with water. firmly touch the snail between the eye stalks with the dampened cotton wool bud and immediately start the stopwatch3. measure the length of time between the touch and the snail being fully emerged from its shell one again with its eye stalks fully extended4. repeat for 15 touches, timing how long it takes to remerge5. record results in table6. use spearman's rank to test significance of resultsstate controls
• what was the results and the conclusion of the kitten method?

  -the kitten stitched up eye was blind

  -ocular dominance for the stitched up eye were a lot smaller than normal

  -the ocular dominance for the open eye had expanded to take over the other columns that weren't being stimulated

  -the neurones in the visual cortex are said to have switched dominance
• what was the kitten method?

  stitched one of their eyes shut and kept like this for several months
• conclusion of monkey method?

  -there is a critical window for visual neural development which requires stimulus from the eye
• results of monkey method?

  -monkeys in group 2 had impaired vision-monkeys in group 3 were blind in the deprived eye-retinal cells were responsive in all 3 groups-cortical activity was reduced in parts of the brain that process info from the deprived eye-adults undergoing some tests showedno difference between groups
• what was the monkey method?

  1. raise monkeys from birth in 3 groups for 6 months

  group 1 are control = no blindfold

  group 2 = blindfold on both eyes

  group 3 = blindfolded on one eye (monocular deprivania)

  2. test monkeys vision, sensitivity of retinal cells and activation of neurones in visual cortex
• what did hubel and wieser do?

  investigate the critical window with monkeys and kittens
• what is the critical window?

  a period during development when an organism's phenotype is responsive to intrinsic or extrinsic (environmental) factors.
• how are neurones grouped together in the visual cortex?

  in columns called ocular ominance columns

  named associated with side of eye received info from

  arranged in alternating pattern : R L R L R L
• what is the visual cortex, whats its role and how does it work?

  an area of the cerebral cortex

  role : receives and processes information

  neurones in the visual cortex receive information from either left or right eye
• how does visual development occur?

  axons from the thalamus grow towards visual cortex in the recipital lobe
• what does hypothalamus control

  homeostasis, pituitary gland
• EQ state two functions associated with cerebral hemispheres

  think

  learn
• EQ suggest how fMRI was able to show that certain areas in the brain become more active when people ate chocolate

  -fMRI can allow brain activity to be seen in real time

  -fMRI uses radio waves

  -increases supply of oxygenated blood in active areas

  -that reflects fMRI signals

  -seen as a white area

  -compare with and without chocolate
• EQ describe how scans from an MRI may be used to investigate brain function

  -identification of location

  -size of tumour

  -type of tumour

  -blood vessels

  -monitoring treatment
• what would happen if brain tumour in frontal lobe reduced in size?

  brain functions improved

  eg thinking and memory
• EQ suggest why tumours appear white in MRI scans

  -tumour tissue differs from brain tissue

  -magnetic field absorbed

  -difference in blood supply
• EQ explain why fMRI is considered better than CT for studying brain function

  -view brain activity directly

  -see brain activity over a period of time

  -safer as does not use X rays

  -no need to use special dyes
• EQ compare the use of CT with MRI for studying brain structure

  -image resolution higher in MRI

  -MRI can identify small structures and CT cannot

  -can identify small tissues

  -MRI uses radio waves and CT uses X rays

  -both give 2D mages

  -MRI is noisy and patients need to keep still

  -images for both are at one point in tie

  -MRI more expensive than CT
• how can activity be detected for PETs

  a tracer is introduced in the blood so it can be detected

  eg radioactively labelled glucose
• PET


  -beta plus emitting radioactive tracer is used in order to stimulate positron electron annihilation to produce gamma photons

  -these are the detected using a ring of gamma cameras

  -traces metabolism, blood flow and neurotransmitter activity
• fMRI scans

  provides information about the brain in action

  -relies on oxygen uptake in active brain areas

  -because deoxyhaemoglobin (w/o O2) absorbs radio wave signals and oxy doesn't

  -so more activity means less radio waves absorbed in that area
• MRI uses


  diagnosis of

  tumours

  strokes

  brain injuries

  brain and spine infections
• MRI advantages

  safer than CT as doesn't use ionising radiation and is non invasive
• MRI scan


  -uses magnetic field and radio waves to detect soft tissue

  -under scanner magnets the protons inside the hydrogen of water in the body line up in the same direction

  -short bursts of radio waves are then sent to certain areas of the body, knocking the protons out of alignment

  -when the radio waves are turns off the protons realign which sends out radio signals

  -these signals provide information about exact location of protons in the body

  -helps distinguish between different tissue types bc protons in different tissue realign at different speeds to produce distinct signals
• CT limitations

  -frozen movement

  -examine structures rather than functions

  -limited resolution so small structures can not be distinguished

  -x rays can be harmful so used less frequently

  -patients need to remain still to prevent blurring
• CT


  -emits thousands of narrow beams of X-rays

  -different soft tissues of the brain can be distinguished
• 4 examples of brain imaging

  CT scans

  MRA

  fMRI

  PET
• EQ b)

  explain how the use of MDMA could result in the development of symptoms of depression

  -MDMA use results in depletion of serotin

  -post synaptic membrane becomes less responsive to serotonin

  -serotonin levels affect mood
• EQ a)

  describe how the use of MDMA could affect the transmission of impulses in the brain

  -MDMA stimulates release of serotonin

  -binding to post synaptic receptors

  -nerve pathways using serotonin are more likely to be stimulated
• EQ

  describe the differences in the structure of a myelinated sensory neurone and myelinated motor neurone

  in sensory neurone

  -dendron longer

  -dendron myelinated

  -axon shorter

  -cell body not at the end

  -no motor end plate
• EQ graph shows effect of opioids on diameter of the eye. between 1-5 hours the diameter increases. explain the effect of opioids on the diameter of the pupil between 1-5 hours graph shows effect of opioids on diameter of the eye.

  • between 1-5 hours after exposure to flash of light-the pupil constricts with opioids
  • the contraction of the circular muscles of iris stimulated and the contraction of the radial muscles inhibited
  • so parasympathetic nerve pathway inhibited and sympathetic nerve pathway stimulated
• EQ

  conotoxins affect membrane proteins. they affect acetylcholine receptors, voltage gated sodium and chlorine channels and calcium ion channelsanalyse this to explain how conotoxins can interfere with the conduction of nerve impulses to muscles-if acetylcholine receptors on post synaptic membrane affected, no depolarisation of post synaptic neurone

  -if calcium ion channels affected, vesicles in presynaptic neurone do not fuse with presynaptic membrane meaning no neurotransmitter released

  -if sodium ion channels affected no depolarisation of axon

  -if potassium ion channels affected, no repolarisation of axon

  -therefore no propagation of action potential
• EQ


  drugs called selective serotonin reuptake inhibitors (SSRIs) are used to reduce depression. they work by inhibiting reabsorption of serotonin at a synapseexplain how SSRIs help to maintain a feeling of well being-SSRIs bind to channel proteins

  -serotonin levels remain high in synapse

  -serotonin binds to receptor proteins in post synaptic membrane

  -depolarisation of post synaptic membrane

  -action potentials continues
• EQexplain the effect of increasing light intensity on the current produced by a rod cell

  • negative correlation showed
  • increasing light intensity decreases the current
  • because rhodopsin is broken down and opsin is released
  • therefore more opsin binds to the channel proteins on the outer segment
  • sodium gated voltage channels close
  • reducing the influx of sodium ions
• EQ

  describe the role of sodium ions in the functioning of a mammalian rod cell

  -sodium ions are pumped out of the rod cell

  -in the light sodium ions do not move back into the rod cell

  -in the dark sodium ions can move back into the rod cell

  -in the light the rod cell is hyper polarised and in the dark the rod cell is depolarised
• EQ

  Alzheimers disease is associated with the loss of neurones that produce acetylcholineit has been suggested that inhibitors of acetylcholinesterase may be useful in the treatment of Alzheimersexplain why inhibitors of acetylcholinesterase may be useful in the treatment of Alzheimers disease-acetylcholinesterase breaks down acetyl choline

  -inhibitor prevents break down of acetyl choline

  -so more acetylcholine is available to bind to post synaptic membrane

  -therefore compensating for the reduced production of acetylcholine