Final Flashcards
3 parts of the cerebral hemispheres
Cortex (surface)
white matter (nerve tracts)
deep structure (basal ganglia, anygdala and hippocampus)
commissures
in the hemispheres
Commissure are nerve bundles
the largest is the corpus callosum
Topographic organization in the brain
each area of the cortex is organized topographically
ipsilateral/contralateral organization in the brain
most of the brain is organized conralaterally, but the cerebellum is organized ipsilaterally.
physical structure of the cortex
Most of cortex is 6-layered with large pyramidal cells - Betz Cells - whose axons make up the major output
Brodmann areas
52 regions of the brain
neocortex, archicortex and paleo cortex
where is the hippocampus?
where is the cingulate cortex?
are phylogenetically older areas of the brain.
Have less layers of cells (3, 4/5)
90% of human brain is the newer neocortex
archicortex contains the hippocampus
cingulate cortex is part of the paleocortex
The cortexes and their functions
- Occiptal - vision
- parietal - somatosensory
- temporal - hearing, language, speech
- frontal - motor and general planning
Association areas of the brain
large areas, particularly in the frontal and parietal lobes that are assumed to be for higher function
overrepresentation in the somatosensory cortex
Some areas in the somatosensory cortex that are important for touch sensation are overrepresented on the topographic map of the cortex
these areas have higher two point discrimination
Phantom limbs
- When part of the body is lost, it’s corresponding region of the sensory homunculous still exists
- plasticity leads to other parts of the body connecting with this region, so sensation in those regions may lead to sensation on the phantom limb
- May be painful/unpleasant
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Common causes of prolongued pain (6)
- Shingles = postherpetic neuralgia. Reactivation of zoster virus can leave pain for months or years
- Tic Douloureux = trigeminal neuraliga. Intense facial pain. Due to pressure on the trigeminal by vascular or neuroplastic changes
- Cancer pain - tissue damage activates silent nociceptors
- Spinal nerve root compression - eg herniated disk
- fibromyalgia - widespread pain in muscles, joints, bones without known cause. More in women
- Complex regional pain syndrome - usually an entire arm or leg.
Central pain:
Damage to anterolateral disk
Damage to thalamus
Damage to the anterolateal system can cause central pain. Particularly on the spinothalamic and spinoreticular fibres.
Damage to thalamus itself can lead to central pain.
Central pain can be intense and can involve half of the body. Often resistant to analgesics.
Effect of distraction on pain
Many people don’t feel pain in urgent activites
Dstraction reduces percieved pain
Responses to pain: somatic reflexes
due to spinal cord connections
Flexor and crossed extensor reflexes - cutaneous pain in an extremity causes limb withdrawal and contralateral limb extension
scratch reflex - cutaneous pain on the body causes limb to remove the source of irritation.
Responses to pain
- autonomic responses
- emotional responses
- learning and memory
hypothalamus and brainstem
- Increased heart rate, respiration rate and blood pressure
- Nausea, vomiting, sweating, dilated pupils
cingulate cortex and limbic system
- anxiety, fear
hippocampal connections
- Important to learn to avoid pain, but people can learn to expect pain, which increases perception of pain (wind up phenomenon)
EEG
what is it
records
wave types
used clinically for
contaminated by
electroencephalogram
- small ascillating voltage recorded from the scalp.
- Mainly measures post synaptic potentials produces by thalamic signals to the cortex
- Alpha rhythms when we are relaxed, awake, eyes closed
- Beta rhythms when open eyes, alert, even in dark. Smaller and faster than alpha.
- Used clinically because epileptiform (abnormal) EEG shows off electrical activity in the brain and can be used for diagnosis of epilepsy, coma level and brain death, measurement of anaesthesia effects, detection of psychotropic drugs
- EEG can be contaminated by eye movements, tongue movements, EKG
REM sleep
when
waves look like
cycling
amount of REM
physical symptoms of REM
At the end of the first sleep cycle, the person doesn’t wake up, instead they enter into REM
REM looks similar to normal/awake/alert EEG
after a short time anodhter cycle through stages 1-4 occurs
Amount of REM increases with each cycle
REM is usually 4 times per night about 20-25% of the total sleep time
When dreaming occurs; muscles relaxed, eyes frequently active, twitches of muscles
Parasomnias
- Somnambulism
- Night terrors
- rhythmic movement disorder
- REM behaviour disorder
- Restless leg syndrome
- Somnambulism - sleepwalking and sleeptalking but not dreaming. Can’t see; often injured
- Night terrors - screaming, sweating, frightened, more than nightmare
- rhythmic movement disorder - rocking, head-rolling
- REM behaviour disorder - acting out dreams, can cause injury to sleeper or companions
- Restless leg syndrome - involuntary leg movements; genetic links
treatment for severe sleep disorder symptoms
tranquilizers - benzodiazepines
NT release during sleep and wakefulness
During wake/alert state, neurons that release norepinephrine and serotonin are active
During awake or in REM sleep, neurons that release acetyl choline are active
sleep wake cycle driven by
Circadian rhythm - a clock mechanism inherent to the brain and triggered by night/day cycle
sleep/wake cycle influenced by several areas of the brain
- superchiasmatic nucleus
- hypothalamus
- reticular system
coma
means a person cannot be aroused
result of many causes (injury, disease, drugs)
consciousness
includes
brain regions
paying attention
includes self awareness, thought, decision making, feeling, planning, imagining
structures involved in consciousness are not well know. Parts of cerebral cortex: thalamus, basal ganglia are essential
the ability to pay attention is enhanced by sensory information