the brain Flashcards
4 lobes
frontal
parietal
occipital
temporal
white matter
below grey mater
composed of millions of nerve axons that connect neurones in different parts of the brain
white colour due to axon’s myelin sheath
broad band of white matter connects two cerebral hemispheres- corpus callosum
thalamus
responsible for routing all the incoming sensory information to the correct part of the brain, via axons of white matter
frontal lobe
concerned with higher brain functions
- reasoning, planning and consciousness of emotions
- forms associations and ideas
includes primary motor cortex
primary motor cortex
in frontal lobe
has neurones which connect directly to spinal cord and brain stem, and from there to muscles
sends information to the body via motor neurones to carry out movements
stores information about how to carry out different movements
parietal lobe
concerned with orientation, movement, sensation, calculation and some types of recognition and memory
occipital lobe
visual cortex
concerned with processing information from the eyes
including vision, colour, shape, recognition and perspective
temporal lobe
concerned with processing auditory information
including hearing, sound, recognition and speech (left temporal lobe)
involved in memory
hypothalamus
lies below thalamus
contains thermoregulatory centre
monitors core body temp and skin temp
initiates corrective action to restore body to optimum temperature
has centres which control sleep, thirst and hunger
acts as an endocrine glam, secreting hormones
connects directly to pituitary gland, which secretes other hormones
hippocampus
involved in laying down long-term memory
basal ganglia
collection of neurones deep within each hemisphere and are responsible for selecting and initiating stored programmes for movement
brain stem
lies at the top of the spinal column
extends from midbrain to medulla oblongata
corpus callosum
white matter composed mainly of axons
- myelin sheath gives white appearance
provides connections between the cortex and other brain structures
forms connections between the two hemispheres of the cortex
cerebellum
responsible for balance
coordinates movements as they are carried out- receives information from primary motor cortex, muscles and joints
midbrain
relays information to the central hemispheres
including auditory information to temporal lobe and visual information to occipital lobe
medulla oblongata
regulates unconscious body processes
eg HR, breathing and BP
neural plasticity
potential of neurones to change in structure and function
allows patients to recover some abilities after a stroke
CT scans
computerised axial tomography
use thousands of narrow beam x rays rotated around patient to pass through tissues from different angles
each narrow beam is reduced in strength based on the density of the tissue in its path
- x rays detected and used to produce thin slice of brain on a computer
limitations of CT
only give ‘frozen moment’ pictures
look at structures in brain rather than functions
limited resolution so small structures in brain cannot be distinguished
X rays are harmful
uses of CT
monitor the tissues in the brain over the course of an illness
detect brain disease
MRI
magnetic resonance imaging
uses magnetic field and radio waves to detect soft tissues
when placed in magnetic field, nuclei of atoms line up with direction of MF
hydrogen atoms in water are monitored in MRI because there is such a high water content in tissues under investigation
- and hydrogen has a strong tendency to line up with the magnetic field
in an MRI scanner
magnetic field runs down the centre of the tube in which the patient lies
another MF is superimposed on this
combined fields cause direction and frequency of spin of the hydrogen nuclei to change- taking energy from the radio waves to do this
when Mf is turned off, nuclei release the energy they absorbed
this energy is detected and a signal is sent to a computer, which produces an image on the screen
uses of mri
diagnosis of tumours, strokes, brain injuries and infections of the brain and spine
produces finely detailed images of brain structures- higher resolution than CT scans for brain stem and spinal cord
Functional MRI uses
provides information about the brain in action- not ‘frozen moment’ images
allows human activities to be studied
- memory, emotion, language and consciousness
used to look at functions of different areas of the brain by following uptake of oxygen in active brain areas
how does FMRI work
follows the oxygen uptake in active brain areas
deoxyhaemoglobin absorbs the radio wave signal whereas oxyhaemoglobin does not
increased neural activity in a brain area increases demand for oxygen therefore increase in blood flow
- large increase in oxyhaemoglobin levels in enhanced blood flow, so less signal is absorbed
more activity in area= less signal
PET scans
used to produce detailed images that allow structure and functioning of tissues and organs to be evaluated
use of PET scans
help diagnose cancers, heart disease and brain disorders
diagnosis and monitoring of alzheimer’s
how do pet scans work
use isotopes with short half lives (11C, 13N, 15O) that are incorporated into compounds that bind to receptors (glucose/ water)
patient injected with radiotracer
radiotracer decays and emits positrons
active tissue/ organ will have increased energy usage
increase in blood flow will show up on PET image, and more radiotracer atoms will be present in that area
when positron collides with electron, two gamma rays are emitted and these are picked up by detectors, converted into signal and displayed as an image by compuer
pet scans and alzheimer’s
accumulation of B- amyloid in brain is early sign of alzheimer’s
patients undergo pet scan with amyloid tracer to visualise fibres of B-amyloid in the brain
as condition progresses, more amyloid plaques accumulate and synapses and acetlycholine receptors are destroyed in the brain
PET allows monitoring of the disease’s clinical progression
alzheimer’s cause
neurone loss
what happens when neurones die
pieces of B- amyloid protein found in the myelin sheath clump together to form clusters of sticky plaques- which can block signalling synapses
plaques can also activate immune cells that trigger an inflammatory response
accumulation of B-amyloid in the brain is a sign of alzheimer’s
