Please enable JavaScript.
Coggle requires JavaScript to display documents.
Neuroscience 1-9 (Ways to study brain function (Clinical neurological exam…
Neuroscience 1-9
-
-
Vision
Phototransduction
-rhodopsin binds to vitA and changes conformation to all-trans retinal -photoreceptors hyperpolarised by light (no AP) -glutamate is transmitter, respond to light with graded changes in potential not AP
In the dark: constant flow of Na into cell (through cGMP Na channels- always kept open by cGMP) -membrane potential is always depolarise d(-30mV) - when exposedd to light, Na channels close and cell hyperpolarises
light activates rhodopsin, initiates events that lead to closure of cGMP gated Na channels
Retina
-
-
Receptive field
ganglion cells respond to light by increasing/decreasing AP firing rate -RF is area of retina that changes one cell's membrane potential -in centre of field, get lots of APs , in periphery not as many - how we see edges and shadows
-
-
-
Touch
Mechanoreceptors
Meissner (superficial, respond to stroking movements, fast adapting)
Merkel complex (close to surface, respond to steady pressure, slow adapting)
Ruffini endings (deep, respond to skin stretch, slowly adapting)
Pacinian corpuscles (deep, fast adapting, respond to vibration)
somatosensory afferents
convey info from skin to central circuits -info from mechanosensory afferent fibre to dorsal root ganglion and up spinal cord to brain -synapses and crosses over midline -info ends up in posterior parietal cortex
-
neurons form functionally distinct columns in cortex -in cortical region representing one region, there are more than one type of mechanoreceptors being integrated there
Hearing
Transduction
vibrations in air detected by inner hair cells (do the transduction - in cochlear of inner ear) -when scapies bone of cochlear vibrates it travels through channels of cochlear
Spectral decomposition: basilar membrane anchored at one side, vibrates when fluid vibrates, tips of hair cells of corti are embedded in this membrane - get travelling wave of vibration - kind of movement depends on freq activating it - hair cells get sheared as tectorial membrane moves across basilar
tympanic membrane vibrates from sound, movement transferred to ossicle bones then oval window
impedence mismatch: mechanical waves transferred into fluid (high vibrations/small force to large force/low amp)
vibrations in cochlear fluid trigger hair cells (organ of corti- above basilar membrane) - starts AP
Mechanoelectrical transduction: -open K channel, K enters if cilia are moving, (in these cells K is high in ECF so K entering causes depolarisation) - get release of Ca - AP -blood vessel cluster (stria vascularis) behind scala media - they are full of Na/K exchange pumps, pump K out against concentration gradient so K flows in when channels open
Pitch
can label pitch -if middle of basilar membrane is most active tellsbrain that its medium freq -as membrane goes up and down, it activates that cell at that freq
neurons fire at same freq that cell is activated (up to firing limit- info at pitch above this, neuron fires less frequently)
auditory nerve fibres cross at multiple levels - when sound comes in to brain stem it is shared by ears early on
Location of sound
Superior olive- determine origin of sound, compares delay to each ear
all signals activate neurons maximally depending on how long nerve pathway is, cells maximally activated on long pathway and another cell at same time but short pathway- brain determines that long pathway sound was closer to the ear
head causes acoustic shadow- sound coming form one side is louder in one ear - trapezoid body compares the volume - input doesnt cross over - inhibits other side