The brain Flashcards
what is the cerebrum divided into
cerebrum is divided into two halves known as the cerebral hemispheres
The hemispheres are joined together by a band of nerve fibres known as the corpus callosum
what is the thin outer layer of the cerebrum known as
the cerebral cortex
this consists of the cell bodies of neurones
It is highly folded, which increases its surface area and allows it to contain a greater number of neurones
With more neurones in the brain, more neurone connections can be made
greater the ability of the brain to carry out more complex behaviours
what is beneath the cerebral cortex
‘white matter’
The white matter consists of the myelinated axons of neurones
what does hypothalamus monitor
the blood as it flows through the brain and, in response, releases hormones or stimulates the neighbouring pituitary gland to release hormones
4 functions of the hypothalamus
Regulating body temperature
Osmoregulation
Cells in the hypothalamus monitor the water balance of the blood and releases the hormone ADH if the blood becomes too concentrated
Regulating digestive activity
Controlling endocrine functions
what does the cerebellum do
cerebellum coordinates movement
what does medulla contain
co-ordination centres that control different functions
The cardiac centre controls heart rate
The respiratory centre controls breathing rate
How does CT scan work
produce cross-section images of the brain using x-ray radiation
A beam of x-rays are aimed at a patient
Digital x-ray detectors are used to pick up the x-rays as they exit the patient’s body
Denser tissue absorbs more of the x-ray radiation so shows up as a lighter region on a scan
What is CT scan good for
shows physical structures of the brain and allows visualisation of any tissue damage
blood is less dense than brain tissue so a CT scan can be used to locate damaged blood vessels and areas of bleeding after a patient has had a stroke
who is CT scan not recommended for
pregnant patients or children due to the risks of exposure to the X-ray radiation, which is given at a higher level than in a normal X-ray
How does MRI work
a combination of a magnetic field and radio waves to generate images through the body
what can be seen using MRI
Soft tissues
identify and locate tumours in the brain
MRI vs CT
MRI scans are considerably more expensive to carry out than CT scans
but do not carry the risk associated with the use of potentially harmful x-rays
difference between fMRI and MRI
fMRI scans allow brain function to be studied in real time
how does fMRI show which brain region is active
location of oxygenated blood indicates
which brain regions is active
what does fMRI scanner measure
measures the ratio of oxygenated to deoxygenated haemoglobin
what does PET scan use
radioactive tracers which collect in areas where there is increased blood flow
what is the visual cortex
region of the cerebral cortex in which visual information is processed
what is the cerebral cortex
the outer layer of the cerebrum
what is a critical period
stages in the lifespan of an organism where it is particularly sensitive to a specific stimulus which is required for the organism to develop properly.
what is habituation
If a stimulus is repeated many times with no negative outcome, then an animal will learn not to respond to it
what happens due to habituation
fewer calcium ions move into the presynaptic neurone on arrival of a nerve impulse
As a result, less neurotransmitter is released and an action potential is less likely to be generated in the postsynaptic neurone
what is Parkinsons disease
a brain disorder that affects the co-ordination of movement, caused by the loss of neurones in some parts of the brain
what do the lost neurones in parkinsons disease normally produce
neurotransmitter dopamine
Dopamine is involved in muscle control
Individuals that suffer from Parkinson’s disease produce insufficient amounts of dopamine due to the loss of dopamine-producing neurones
what happens when less dopamine is released into synaptic cleft
less is able to bind with receptors on the postsynaptic membrane
Fewer sodium channels on the membrane are opened so depolarisation of the postsynaptic neurone does not occur
This leads to fewer action potentials which creates the symptoms such as tremors and slow movement
types of drugs that treat parkinsons
Dopamine precursors - L dopa
These are chemicals that can be converted into dopamine in the neurones
Dopamine agonists
Produce the same effect as dopamine by binding to and activating the dopamine receptors on the postsynaptic membrane
Enzyme inhibitors
Monoamine oxidase B (MAOB) inhibitors inhibit the activity of enzymes that would normally break down dopamine in the synaptic cleft, raising levels of dopamine present in the brain
what is linked to depression
Low levels of the neurotransmitter serotonin
what does serotonin do
transmits nerve impulses through the areas of the brain that control mood
what does MDMA do
inhibits the reuptake of serotonin into the presynaptic neurone by binding to the specific proteins that enable serotonin reuptake, located on the presynaptic membrane; this increases the amount of serotonin present in the brain
Serotonin is usually reabsorbed into the presynaptic neurone to be recycled for future action potentials
MDMA also triggers the release of further serotonin from presynaptic neurones, further adding to the increase
what does a person who takes MDMA / ecstasy feel
extreme euphoria and enhanced touch and bodily sensations
where is L dopa transported from and what is it converted to
transported from the blood into the brain, where it is converted into dopamine in a reaction catalysed by the enzyme dopa-decarboxylase
what does L Dopa do
increase levels of dopamine so that more nerve impulses are transmitted in parts of the brain that control movement, giving sufferers better control over their movement and lessening the symptoms of Parkinson’s disease
What does Human genome project involve
sequencing of the entire human genome
The information gained during the HGP is stored in databases, within which genes that code for certain proteins can be found and analysed
Knowing the sequence and structure of proteins involved in disease allows the development of drugs that target specific proteins
what does genetic engineering consist of
removing a gene that codes for a desired characteristic from one organism and transferring the gene into another organism where the desired gene is then expressed
what does the genetically engineered organism contain
recombinant DNA and will be a genetically modified organism (GMO)
what removes gene coding for desired protein
Restriction enzymes
what are the copies of the gene made by PCR inserted into
small loops of DNA called plasmids, which then transfer the copies into micro-organisms
The plasmids are said to be DNA vectors
The enzyme DNA ligase catalyses the joining of the desired gene to the plasmid vector
where are the genetically modified micro organisms grown
in large fermenters containing nutrients, enabling them to multiply and produce large quantities of the new protein
The protein can be isolated and purified before being packaged and distributed
how can animals be genetically modified
gene that codes for the desired protein is injected into the nucleus of a zygote
The zygote is implanted into the uterus of a surrogate animal where it develops into an adult animal
