Brain Flashcards
What is lesioning?
Experimental brain lesions. Created by using a stereotaxic apparatus to insert a fine wire into a particular part of the brain
What did phineas gage have injured?
his frontal lobe. Shown by planning, processing of emotion and rational decision making
Who is Tan?
A man who was studied by Broca who could only say the word Tan. This concludes that the brocas area in the left hemisphere is responsible for speech
Who is Henry molesian? (HM)
A patient who had surgery for intractable epilepsy. Removed a lot of his temporal lobe including his hippocampus. Concluded the hippocampus is essential for speech
What is MRI?
Magnetic resonance imaging
safer than CT scanning (no X-rays)
magnetic field. The hydrogen reverberations are detected by the scanner
Signals are examined for subtle differences between blood etc
Creates a 3D anatomical pic
used for tumors, tissue degeneration, leaks and blood clots
What are the different types of neuroimaging?
Positron emmision Tomography (PET) Magnetoencephalography (MEG) Electroencaephelography (EEG) Functional magnetic resonance imaging (fMRI) Transcranial magnetic stimulation (TMS)
Describe EEG
detects electrical currents generated by neurons on the brain surface only, by affixing metal electrodes to the scalp
Poor spatial resolution. Excellent temporal resolution.
REsolution is improved with high density arrays
What are event related potentials?
average the signals across many trials to deal with the noise. Some measure sensory response to a stimulus N100 (100ms) after the stimulus.
What is N400
Linked with language processing
Elicited in sentences where the last word is surprising although linguistically legal. The more difficult the task the greater the N400
What is fMRI?
detects fast changes aspects of brain physiology such as blood flow /oxygen use.
Does not have any radioactivity.
Can detect the iron in blood for changes
three dimensional image of the brain at work showing which parts are active.
What is TMS?
creates temporary brain dysfunction so you can perform experiments that wouldn’t be possible otherwise.
Series of strong magnetic pulses on scalp that causes temporary disruption in region below the area being stimulated on the scalp.
When does the nervous system start to develop?
3rd week of embryonic life. Small thickening on the top of the embryo. After a few days the edges of the neural plate zip together to form the neural tube
What happens at one month of the development?
separates into 3 thickenings forebrain, midbrain and hind brain
What is the somatic nervous system made up of?
afferent, efferent and cranial nerves
What is autonomic nervous system made up of?
the regulation of the viscera. the intestines, heart etc
What are the cranial nerves?
12 pairs. enter and exit from the hindbrain (pons/medulla)
poke through holes in the skull
control movements and carry sensations from head and neck
regulate glandular secretions in the head
control visceral functions
how many neurons are there?
10-100billion
What is the left hemisphere for?
language
What is the right hemisphere for?
spatial awareness
Describe the pons
Hindbrain arousal relays sensory info between cerebellum cerebrum and other parts of the brain regulates respiration involved in sleep and dreaming
What is locked in syndrome?
where youre awake and aware but cannot move due to paralysis of the body
journalist who wrote the diving bell and the butterfly using only his left eyelid
Describe the medulla
regulation of HR BP and respiration rate
involved in vomiting, defecation, reflexes and respiration
in simpler animals, crawling/swimming
Describe the cerebellum
knows what each part of the body is doing
recieves information from frontal lobes and what movements it intends to accomplish
monitors info about posture and balance
produces eye movements which compensate for changes in head movements
may play a role in learning new skills
Controls overall body/balance. damage leads to wide stance and staggering gait
sequencing and timing of precise skilled movements
damage = temors during movement
impairs performance of tasks requiring exact sequencing
What is the midbrain involved in?
auditory and visual stimuli (eye movement)
controls movement used in sexual behavior and fighting
decreases sensitivity to pain
What is blind sight?
not seeing an object but being able to grasp it
visual system that guides reaching intact but is not connected to system that sees the location of the object
What happened to patient TN?
blinded by strokes in both hemispheres
essential blind but reacts to facial expressions
describe the cortex
80% of brain volume
leadsto flexibility of behaviour
2-3mm thick. if flat would be about 2 feet
The actions of the cortex are performed by subcortical areas in non mammals as as the cortex grew the mid/hind brain became more relay stations
What is the thalamus?
receiving and relay station for sensory input
receives info from the sense organs
performs simple analysis
passes results onto primary sensory cortex
What is the hypothalamus?
homeostasis and species typical behavior
feeding, drinking, body temp, sex
Controls much of the activity of the autonomous system
What do the basal ganglia do?
regulate and smooth movement. found beside the hypothalamus
What is the Limbic system?
made up of the amygdala for emotion and the hippocampus for memory
What is the parietal lobe important for?
spatial perception
What is the temporal lobe for
receiving auditory info
What is the frontal lobe for
responsible for motor output and motor plannng
What is the differences between primary and secondary areas
primary is the basic input and output. secondary is elaborate or higher functions
What happens when there is damage to the primary visual areas?
causes a scotoma
a hole in the visual field like a blind spot
What is hemianopia?
removal of the primary visual cortex on one side causes a hemianopia on the opp side
What is hemiplegia?
paralysis of one side of the body
due to damage of contralateral cortex
paralysis is worse at the extremities
What are association areas?
don’t show fixed sensory mapping. important in higher functions
What is visual agnosia?
cannot identify familiar object
due to occipital damage and parts of temporal/parietal lobes
can identify separate details of picture but not picture as a whole
What is prosopagnosia?
damage to temporal/parietal lobes
difficulty in recognizing faces
‘man who mistook his wife for a hat’
Describe the what pathway
the ventral stream
determines what an object is
goes down into the temporal lobe
Describe the where pathway
dorsal stream
goes up the parietal lobe
determines where an object is in space
What happens when there is damage to the prefrontal cortex?
deficiency in response inhibition inability to plan appear uninvolved, depressed and apathetic sexually promiscious criminal behavior act fragrantly and crudely
What happened after a prefrontal lobotomy?
patient docile and cognitively disabled. used in 40s and 50s
What is Apraxia?
frontal lobe
serious disturbances in initiation or organization of voluntary action
unable to perform well known actions
actions become fragmented and disorganised.
What does aphasia result from?
left hemisphere language damage
where does the middle cerebral artery run?
close to the language areas
What is brocas area do?
speech production and syntax
what does wernikes area do?
speech comprehension
what does the arcuate fasiculus do?
connects the two
what does the angular gyrus do?
reading
What is brocas aphasia?
can move tongue vocalize and swear. agrammatism understanding generally alright but complete syntax not understood.
What is wernikes aphasia?
lack of comprehension
speaking is fluent and grammatical but meaningless - jargon aphasia
What is sign language aphasia?
same a spoken language as same areas are involved
What the difference between acquired and developed dyslexia?
developed - difficultly learning to read despite intelligence and education
acquired - brain damage in left angular gyrus. in those with previously normal reading. deep phonological surface
What is neglect syndrome?
People with left parietal damage tend to neglect the right side of space. can be visual auditory or tactual. problem of attention - called hemiinattention
What is anosognosia?
an emotional problem. denial of any deficit of neglect syndrome.
Why is neglect syndrome more on the left side?
Because the right side is controlled by the left hemisphere so has more language than spatial so damage does not have as much of an effect.
What is the right side of the brain dominant for?
spatial attention (neglect)
music (amusia)
facial recognition (proposagnosia)
recognition of natural objects (agnosia)
What is the left side of the brain dominant for?
language (aphasia)
recognition of manufactured objects (agnosia)
voluntary action (apraxia)
handedness
What side of the brain recognizes tools?
left
What side of the brain recognizes animals?
right
What is split brain surgery?
relief of intractable multifocal epilepsy
separates right and left hemispheres
prevents seizures from spreading throughout the brain
What is the corupus callosum?
largest central commisure. more than 200million axons. connects the two hemispheres
in 60s all commisures were sectioned (commisurotomy)
in the 70s only the corpus callosum was sectioned (callosotomy)
does split brain surgery work?
successful in controlling epilepsy
usually do anterior first and if that doesn’t work posterior
dying out with better control from drugs
What happens to split brain patients?
everyday seem fine. but sometimes get an alien hand where their hand takes on a life of its own
If they can only see a ball in their right hemisphere they cannot name the ball
What happens to left hemisphere function in the split brain?
can’t name objects etc presented in left field
cant name objects held in left hand
can understand words in the left field
suggests that right brain can understand but not speak
What is callosal agenesis?
in some people the corpus callosum does not develop. these people are naturally split brain
There is less evidence of disconnection in these people. Their interhemispheic transmisson time is about 20-30ms instead of the normal 4-6ms.
Suggests plasticity in early life
What are Probsts bundles?
remains of corpus callosum that failed to cross the midline
What do neurons do?
perform computations inside the brain that we call thought
How big are neurons?
Soma is5-100microns in diameter
dendrites are only a few hundred microns long
Whats the difference between white matter and grey matter?
white is myelinated grey is unmyelinated
What are interneurons?
interposed between other neurons. do much of the computing in the brain
What are glial cells?
about 90% of cells in the brain
act as guidewires for growing neurons
provide supportive scaffolding for neurons
and assist in repair process when neurons are damaged
What is the resting potential?
about -70mV
What is the excitation threshold?
about -55mV
What does the resting potential depend on?
positive sodium ions being outside the cell
What happens when a pulse is supplied to a neuron at resting potential?
ingoing channels open. Na pours in. The inside swings positive to the outside.
Na channels then close
potassium leaves the cell to restore the original voltage difference
What is the lock and key model?
NT molecules will only affect the post synaptic membrane if the molecule shape fits into certain synaptic receptors
How are NTs reuptaken?
inactivated by certain cleanup enzymes.
reused in synaptic uptake
What are antagonists?
drugs that block or inhibit postsynaptic effects
What are agonists?
drugs that facilitate postsynaptic effects
How can drugs effect the synapse?
stimulate or inhibit NT release
stimulate or block postsynaptic receptor molecules
inhibit reuptake
What does the venom of the black widow spider do?
Drug that stimulates NT release it is a ACh agonist releases lots of ACh exhausts victims supply of ACh lad to paralysis and death in small prey
What does the Botulinum toxin do?
inhibits NT release present in improperly canned food ACh antagonist prevents release of ACh small amount of this toxin leads to the victim being paralyzed and suffocating to death
What does nicotine do?
stimulates postsynaptic receptors
mimics ACh
low doses = pleasure and addictive
high dose = convulsions and death
What is curare?
blocks postsynaptic receptors
used on the darts of blowguns
blocks ACh receptors on muscle fibres
victim can’t breathe and suffocates to death
What do amphetamines/cocaine do?
inhibit the reuptake of NT
dopamine, NE and E
affects autonomic arousal
resulting in restlessness, insomnia, loss of appetite and euphoria
What do antidepressants do?
eg prozac
is a serotonin agonist
inhibits reuptake
relieves depression
What do benzodiazapines do?
eg valium
GABA agonist
reduces anxiety, facilitates sleep
What does heroin do?
affects endorphins
agonist
mimics at postsynaptic receptor
anaglesia, sedation, euphoria
