The Brain
Greater than the sum of its parts
Sensory receptors
• Specialized to respond to changes in the
environment (stimuli)
types of sensory neurons
• Mechanoreceptors: touch, pressure, vibration,
stretch and itch
• Thermoreceptors: temperature changes
• Photoreceptors: light energy
• Chemoreceptors: chemicals in solution, smell,
taste, blood chemistry
• Nocioceptors: damaging stimuli that result in
pain
Spinal nerves
• Nerve pairs that arrive from
the spinal cord
Cranial nerves
• Nerve pairs that arise from
brain
All feed into here…
Like a mushroom
Four Major Divisions
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Cerebrum
Cerebellum
Diencephalon
Brain Stem
• P449 of text – overview of each area’s
function
Gross Anatomy
• Elevated ridge: gyrus (plural = gyri)
• Groove/furrow: sulcus (sulci)
• Deeper grooves = fissures
• Landmarks – same in all people
Longitudinal fissure
Lateralization = specialization of
each hemisphere
Sheep Brain Dissection
• External Anatomy today: (each person)
– Draw a top view, side view, and underneath view
– Label: transverse fissure, longitudinal fissure
– Label: brain stem, cerebrum, cerebellum
– Label: Spinal cord, medulla oblongata, pons
– Label: example of a gyrus, example of a sulcus
Corpus Callosum
• Axons connecting the
hemispheres
• Pathway for
communication
Brain Stem = highway
The cerebrum
• 80% of the brain’s mass
• Divided into section based on the major
landmarks – sulci and fissures
Named for the parts of the skull they
sit under
gray and white matter
• Gray Matter
– Top outermost portion of the cerebrum = cerebral
cortex
– Cell bodies and interneurons
• White matter
– Bulk of cerebrum
– Myelinated axons
• Dissection continued…
What does the brain do?
Electrical and magnetic detection
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Electroencephalogram (EEG)
Transcranial magnetic stimulation (TMS)
Positron emission Tomography (PET)
Magnetic Resonance Imaging (MRI)
Electroencephalogram (EEG)
• Uses electrodes to measure electrical activity
(impulses)
Electroencephalogram (EEG)
EEG Recording from multiple places
Using a needle electrode: record
directly from surface of brain
Patient is still awake and talking
Transcranial magnetic stimulation
(TMS)
• NOVA Now segment
• Using a magnet to alter the electrical
messages of the brain
Positron emission Tomography (PET)
• Measures blood flow
• Inject radioactive material
• Detect the decay
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Same amount of env. radiation that you’d be exposed to in 3 years’ time
Short lifespan, cleared quickly by body
MRI
• Use a magnetic field to excite electrons in your
body = produce radio waves
• radio waves are measured and analyzed by a
computer
fMRI
• Looking at oxygen levels
• More oxygen = more activity
• A strong magnetic field is created by passing an electric
current through the wire loops. While this is
happening, other coils in the magnet send and receive
radio waves. This triggers protons in the body to align
themselves. Once aligned, radio waves are absorbed by
the protons, which stimulate spinning. Energy is
released after "exciting" the molecules, which in turn
emits energy signals that are picked up by the coil. This
information is then sent to a computer which
processes all the signals and generates it into an image.
The final product is a 3-D image representation of the
area being examined.
• Sensory information communicated to brain
(via spine)*
• Brain = interneurons
• Generates a motor response – delivery
• * spinal reflex = bypasses brain involvement