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 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 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 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