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BIOL 4370 (20)
Lecture

Oct. 17th.docx

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Department
Biology
Course
BIOL 4370
Professor
Dr.o'shaughnessy
Semester
Fall

Description
th Oct. 17 • On center ganglion cells when center is bright AND surround is dark - when light is in surround there is inhibitory response - when some of surround is lit but all of center is lit excitatory response - this enhances contrast • Center surround comes from horizontal cells (GABAergic) - when cone is surround causes more AP in dark than light because surround cones are depolarized in dark and they release glutamate onto horizontal cell which depolarizes (ligand gated Na channels) and causes Ca gated voltage channels and releases GABA onto center cone which causes a hyperpolarization of center cone (which is same as making center cone lit) • When we see object in world, object is inverted and upside down. - binocular visual field sees mostly what both the right and left eye see but it has a left monocular portion and a right monocular portion (a part which only the left or right eye can see) • Left visual field activates nasal retina of left eye and temporal retina of right eye and vice versa for right visual field - nasal axons decussate at optic chiasm - optic nerve (cranial nerve #2) only exists before chiasm (after optic chiasm axons are called optic tract) • lateral geniculate nucleus is part of thalamus that received input - LGN sends many axons (axons radiate and have a topography) • hippocampus important for memory - holes are ventricles and hold CSF (cerebrospinal fluid) - white matter in middle is called internal capsule (from thalamus up to cortex) - corpus callosum communicates between two hemispheres and has 200 million axons - thalamus houses LGN (visual) - cortex is gray matter (2mm thick in all mammals) but in humans have lots of sulcus and gyri which increases surface area greatly • cortex has 6 different layers - 2 main types of cells, pyramidal neurons (shaped like pyramids) and stellate neurons (star shaped) - pyramidal neurons are projection neurons (sends axon long distance) and are all excitatory (GABA) 70% - stellate neurons are local neurons (send axons short distance) and can be excitatory OR inhibitory 30% - layers 2/3 send axons to other areas (including hemispheres) and receiving from other areas - layer 4 is main input layer (thalamic axons terminate) synapse onto stellate neurons - layer 5 sends axons to brain stem or spinal cord (motor cortex) - layer 6 sends axons back to thalamus (more axons go back to thalamus that go out from thalamus) - layer 1 has no cell bodies. Has dendrites of pyramidal neurons and axons from other neurons (stellate). Lots of synapse in layer 1 • NISL stains can show where cell bodies are for different parts of cortex - not all parts of cortex have all 6 layers - archcortex is oldest(?) part of and has less than 6 layers - paleocortex (pyriform cortex) has 4 layers - neocortex (motor cortex) has bigger neurons in layer 5 • Brodmann’s areas numbered areas of brain in terms of difference in layers of cortex - 3,1,2 is primary somatosensory cortex - 4 is primary motor cortex - 17 primary visual cortex - 41, 42 primary auditory cortex • Primary visual cortex organization -
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