The Brain Sensory Control Somatosensory Cortex Motor Cortex

The Brain & Sensory Control

Somatosensory Cortex Motor Cortex e b o L al et i r a P Occipital Lo be e ob l. L ta on Fr Tem por Primary Visual Cortex Secondary Visual Cortex al L obe Gustatory Insula Auditory Cortex Olfactory Cortex

Motor & Sensory Cortex

Skin Receptors • Meissner’s = Light touch • Pacinian = Pressure, texture, pain • Ruffini’s = Direction of touch, position • Merkel’s = Pressure (baroreception) • Free endings = temperature, pain (nocireception)

Vision • Human vision is binocular and stereoscopic • Differing visual fields allow for depth perception • The optic chiasma helps direct nerve fibres to occipital lobe, corrects image

Vision • The retina contains photoreceptors: • Cones for colour: about 5 million, centrally placed • Rods for greyscale: about 100 million, peripherally placed

Vision • Light passing through the lens is refracted • Image on the retina is inverted

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Olfaction (Smell!) • Shortest sensory nerves • chemoreceptors

Degustation (Taste!) • Closely related to olfaction • Same chemicals trigger the chemoreceptors of both senses

Degustation (Taste!)

Hearing • Begins with a mechanoreceptor: the ear drum picks up vibrations • 3 middle ear ossicles (tiny bones) – the malleus, incus, & stapes - pick up & magnify the vibrations • The stapes pushes on the foramen ovale (‘oval window’) of the cochlea • Fluid in the cochlea moves back & forth, stimulating sensory hairs

Hearing • The cochlea takes the mechanical stimulus and converts it to an electrochemical signal • An action potential is triggered, and sent via the auditory nerve to the brain.

Hearing • Sound intensity can cause physical damage to these structures

Language • Not strictly sensory, but distinctly human • Left hemisphere control Wernicke’s Area: Language comprehension, meaning… Broca’s Area: Language production, speech, writing, sign language… Associative Cortex connects the two.

Birds vs. Humans Communication is not the same as Language! Birds use very few brain structures to produce innate songs, just as humans use few areas to produce emotional laughter, sobbing, and screaming. But learning and producing variable songs activates many areas of bird brains, much the way the human brain recruits many areas to produce speech. So, is bird song ‘language’?

Stroke • Ischemic: blockage (thrombus, embolism) stops blood flow • Hemorrhagic: burst blood vessel (aneurysm) causes internal bleeding • Paralysis (paraplegia, hemiplegia) • Aphasia

Autism • Complex psychosocial disorder • Unclear origins • Many brain regions involved • Language often limited • Communication, social relationships impaired

Our brain is amazing!

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