Exam 3 Flashcards
hearing
- we hear the change in pressure in air that surrounds us
- helps us locate objects in space
amplitude
- how loud, measured in decibels (dB)
- the height of the wave
frequency
- the pitch
- wave cycles per second
- more cycles means higher frequency
outer ear
functions to funnel sound into middle ear
middle ear
- concentrates energy/sound from a large area to a small surface area
- sound is amplified when ear drum sends info to malleus –> incus –> stapes
- stapes sends mechanical energy to oval window
- concentration of energy from ear drum to oval window goes from a high surface area to low surface area (sounds amplification)
tensor tympani and stapedius muscles
function to dampen the vibration of ossicles in order to prevent damage to ear
inner ear
made up of cochlea
organ of corti
- has 2 sets of sensory cells:
- inner hair cells
- outer hair cells
stereocilia
protrudes from each hair cell
tip links
thin fibers that run across each hair cell’s stereocilia
auditory info sent to brain
- vibration makes stereocilia sway, causing K and Ca ion channels to open
- high concentration of K+ outside cell and low concentration inside cell
- K+ enters cell when sound waves come into ear
- K+ depolarizes hair cell, causing voltage gated Ca2+ channels to open at base of cell
- Ca2+ entry causes release of glutamate or acetylcholine to ganglion neurons
- glutamate or acetylcholine activate ganglion neurons to send sound signals to brain
hair cell depolarization
hair cells are depolarized by K+
basilar membrane
- sound vibrations cause basilar membrane to oscillate
- different parts respond to different frequencies:
- high frequency –> displaces narrow base of basilar membrane
- low frequency –> displaces wider apex
inner hair cell releases…
glutamate
outer hair cell releases…
ACh
function of inner hair cells
send auditory information to brain
function of outer hair cells
amplify sound
cortical tonotopy of auditory cortex
- higher frequency in posterior auditory cortex
- lower frequency in anterior auditory cortex
encoding frequency properties of a sound
- place coding or tonotopic representation
- temporal pattern of firing of cells:
- higher firing rates for higher frequency
encoding loudness of a sound
movement of basilar membrane
sound location detection
- binaural cues signal sound location:
- intensity differences: different in loudness at the 2 ears
- latency differences between the 2 ears in the “time of arrival” of sounds
auditory pathways of human brain
cochlear nucleus –> switches side of brain –> superior ovilary nucleus –> inferior colliculus –> medial geniculate nucleus –> auditory cortex
retina
- images a mirrored upside down on retina
- contains 3 primary layers: ganglion cell layer, bipolar cell layer, photoreceptor cell layer
- contains rods and cones
activation profile of visual system
- light bounces off image end enters eye
- light hits retina at back of eye
- visual info from retina travels down optic tract
- optic tract sends visual info to lateral geniculate nucleus (LGN) of the thalamus
- thalamus separates visual info and sends it to primary visual cortex (V1)
- V1 further breaks down components of image
- V1 is where visual perception occurs
- V1 sends info to dorsal and ventral pathways
the colors we see…
are wavelengths bouncing off that object
fovea
- where vision is sharpest and where one focuses on objects
- highest density of cones
process of light entering eye
- cornea and lens focus light entering eye onto retina
- refraction is done by cornea and lens
- bending of light focuses image onto retina
- ciliary muscles in eye adjust focus by changing shape of lens
- light hitting retina activates photoreceptors
- vision is sharpest at fovea
refraction
bending of light
optic disc
where blood vessels enter and leave eye
blind spot
due to lack of photoreceptors in optic disc
information transfer of the retina
- photoreceptors (rods and cones) respond to light
- photoreceptors do not fire action potentials, but send a signal (glutamate) to activate the bipolar cells
- the bipolar cells don’t fire action potentials but release glutamate to activate the ganglion cells
- ganglion cells are the first sight where action potentials occur
- the axons of the ganglion cells form the optic tract
bipolar cells
receive input from photoreceptors and synapse on ganglion cells, whose axons form the optic nerve
horizontal cells
are in the retina and contact photoreceptors and bipolar cells
amacrine cells
contact bipolar and ganglion cells
rhodopsin
- opsin + retinal = rhodopsin
- it is a GPCR
- when light activates retinal to change shape, the g protein (transducin) activates phosphodiesterase (PDE)
- PDE turns cGMP into GMP
- cGMP activates voltage gated Na+ channels
- light hyperpolarizes the rods
- in the dark rods are depolarized
3 types of cones
there are cones that respond to either blue, green, or red light and are called S, M, L (for short, medium, and long wavelength light)
optic tract
- groups left visual fields into the right visual cortex
- groups right visual fields into the left visual cortex
optic chiasm
- ganglion cell axons form the optic nerve and cross at the optic chiasm
- after passing the optic chiasm, the axons are called the optic tract
- most axons synapse on cells in the lateral geniculate nucleus (LGN) of the thalamus
LGN
- information is sent to LGN from optic tract
- LGN is the first structure in the brain where visual information is processed
- LGN contains layers that separate visual movement
where pathway
dorsal
V1 –> V2 –> area MT –> posterior parietal lobe
vision for movement, location
what pathway
ventral
V1 –> V2 –> V4 –> inferior temporal cortex
vision for recognition (objects, faces)
where and what pathways come together in…
- hippocampus
- why memories are highly visual (visual dreams)
- both pathways are important for autobiographical learning and memory
cochlear duct
contains tectorial membrane, organ of corti, and basilar membrane
primary regions of CNS that control movement
- ACh: initiates muscle contraction
- muscles: moves your skeleton
- spinal cord: sends and receives commands and the reflex
- basal ganglia: motor learning
- motor cortices: motor command
motor system
- brain can initiate movement and receives information about movement
- simplest form of movement is the reflex (does not require a brain)
- complex movements are obvious
- many pathologies affect motor system (parkinson’s and huntington’s)
human motor cortical areas
- premotor cortex
- supplementary motor area
- primary motor cortex
primary motor cortex
- primary motor cortex maps the body
- homunculus
homunculus
represents the area of the motor strip relating to its body part
movements are controlled at several nervous system levels
- in a reaching task, muscle cells change firing rate according to the direction of the movement
- each cell has one direction that elicits highest activity
- an average of the activity can predict the direction of the reach
premotor cortex selects motor commands
- encodes the intention to perform a particular movement; thus, they are involved in the selection of movements based on external events
- your brain will have already initiated movement before you are aware of the movement you will make
- you perceive that the choice was yours, but the choice occurred prior to perception
motor cortices receive and send…
axons/information to the basal ganglia
example of riding a bike:
- basal ganglia receives commands from motor cortex
- basal ganglia permits motor commands to initiate
- cortex may not know exactly what commands to send (but has general idea)
- commands are not accurate before learning
- during motor learning/procedural learning basal ganglia “fine tunes” motor commands
basal ganglia
motor learning AKA procedural learning
basal ganglia circuitry
substantia nigra and ventral tegmental area regulate dopamine production
additional functions of the basal ganglia
- habitual learning
- drug addiction
- procedural learning
- parkinson’s disease
- huntington’s disease
- eye movement
- motor planning
spinal cord components
cervical
thoracic
lumbar
sacral
spinal input and output
- dorsal root: carries sensory information from the body to the spinal cord
- ventral root: carries motor information from the spinal cord to the muscles
spine synapse to…
muscles at neuromuscular junction
ACh initiates muscle contraction
- motoneurons are nerve cells in the spinal cord that send their axons in innervate muscles
- action potentials travel down the motoneuron, which branches into many terminals near its target
- neurotransmitter ACh is released –> causes Ca2+ to be released –> causes myosin heads to move towards actin –> muscle contraction
