8B Brain, Behaviour, GMOs and HGP Flashcards
cerebrum
LARGEST part
made up of left and right cerebral hemisphere
thin outer layer = cerebral cortex -> large s.a so highly folded to fit into skull
vision -> in back of cortex
learning
thinking -> in front of cortex
emotions
movement
hypothalamus
beneath middle part
maintains BODY TEMP. (thermoregulation)
produces HORMONES that CONTROL PIT. GLAND
medulla oblongata
at base of brain , top of spinal cord
controls BREATHING rate and HEART rate
cerebellum
underneath cerebrum
also has folded cortex
coordinating movement
balance
how are CT scans used to investigate brain structure and function?
- use radiation (x-rays) to produce cross-sectional images of brain
- dense structures absorb more radiation so appear lighter
- shows major structures but NOT FUNCTIONS
pros and cons of CT scans
PROS
- non invasive
CONS
- x-rays can cause more mutations of DNA -> may lead to CANCER
- not in real-time
- look at structures not functions
how are MRI scans used to investigate brain structure and function?
use v strong MAGNETIC FIELD and RADIO WAVES to produce cross-sectional images of brain
pros and cons of MRI scans
PROS
- higher quality images than CT
- better resolution between tissue types
- MRIs let you clearly see diff between NORMAL and ABNORMAL brain tissue
CONS
- image affected by movement
- does not show bone
how fMRI scans are used to investigate brain structure and function? how do they work?
- like MRI but show CHANGES in brain activity
- detect levels of O₂ in blood -> more O₂ = more activity
- molecules in oxygenated blood respond diff to magnetic field than deoxy blood
-> signal stronger in oxy -> allows more active areas of brain to be identified - measures ratio of oxy to deoxy haemoglobin
how PET scans are used to investigate brain structure and function?
show how ACTIVE diff parts of brain are
- radioactive tracer introduced to body and absorbed into tissues
- scanner detects RADIOACTIVITY of tracer -> building up MAP of radioactivity
- diff tracers can be used -> eg. radioactively labelled glucose used to look at glucose metabolism
how can you medically diagnose from PET scans?
- to see if areas in brain are usually active / inactive
- so useful for studying disorders that change brains activity -> eg. in Alzheimer’s certain areas activity reduced
- PET scan shows this reduction compared to normal brain
habituation
process where if stimulus is repeated many times with no negative outcome -> animal learns not to respond to it
why is habituation important
so animals don’t waste energy responding to unimportant stimuli
spend more time doing other activities for their survival eg. feeding
visual cortex
area of cerebral cortex at BACK of brain
receive and process visual info
what are ocular dominance columns?
neurones in visual cortex that receive info from left / right eye
columns are SAME SIZE and arranged oil ALTERNATING PATTERN
what did Hubel and Wiesel discover?
structure of visual cortex
found left ocular columns used when cat uses right eye (stitched up left) and vice versa
describe Hubel and Wiesels experiment on KITTENS
(experiments repeated on young and adult monkeys to see same results)
used animal models to study electrical activity of neurones in visual cortex
- stitched one eye shut of each kitten
- kittens kept like this for several months before eyes unstitched -> eye was now blind
- ocular dominance columns were lot SMALLER than normal for stitched up eye and ocular dominance columns were a lot BIGGER in open eye
ocular dom. columns for open eye expanded to take over other columns that weren’t being stimulated
-> when this happens, NEURONES in visual cortex have SWITCHED DOMINANCE
-> this proves that visual cortex only develops into normal ocular dominance columns if both eyes visually stimulated in v early stages of life
describe Hubel and Wiesels experiment on CATS
same as kittens BUT EYE HADN’T GONE BLIND
cats fully recovered vision and ocular dominance columns remained the same
compare use of CT scans and MRI scans for studying brain structure
- MRI offers more IMAGE RESOLUTION
- MRI uses magnetic field whereas CT uses x-rays
- MRI more EXPENSIVE than CT
against use of animals in medical research ethical and moral points
AGAINST:
- testing on human cells and tissues and use of computer modelling provide alternative option to testing on animals
- animals should have same rights as humans when it comes to welfare and consent
- animals do still suffer distress and pain during research
-> some killed - animal and human anatomy / physiology not identical
-> medications can often have different effects on humans and animals
pro use of animals in medical research points
FOR:
- New drugs need to be tested on the whole organism NOT just on groups of cells
- testing medications on humans before we know that they are safe is UNETHICAL -> animals provide more
acceptable alternative - animal research only carried out when no alternative options and governed by strict welfare regulations
- animal anatomy is often similar to humans so results in these cases can be transferable
describe how you would investigate habituation in a snail
- allow snail to get used to surroundings for a few mins
- firmly touch damp cotton bud between eye stalks and immediately start stop watch
- measure length of time between poke and snail being fully emerged from shell again with eye stalks fully extended
- repeat prev. step 15 times, timing how long each time
- records results in suitable table
