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The conversion of a stimulus into a receptor potential is called __
- physical things into voltage
If the __ is large enough, it will trigger an __ in the afferent neuron that travels along the axon into the interneuron networks of the CNS
receptor potential; action potential
(page 29 on slide)
Sensory receptor proteins that are ion channels or directly affect ion channels are __
e.g. mechanoreceptors (pressure), thermoreceptors (heat), electroreceptors (voltage-gate)
(page 6 on slide)
Sensory receptor proteins that affect ion channels through g proteins & second messengers are __
e.g. chemoreceptors (odorants), photoreceptors (light)
(page 7 on slide)
__ cells transduce energy of a stimulus into a change in membrane potential
graded membrane potentials that travel a short distance
receptor potential (EPSP for sensory cell)
Receptor potentials can generate action potentials in 2 ways:
- can generate action potentials in the receptor cell
- can trigger release of neurotransmitter so that a downstream neuron generates an action potential
(page 10 on slide)
Sensation depends on which part of the __
CNS receives the sensory messages.
- Some sensory cells transmit info to the brain about internal conditions, without conscious sensation.
- Different messages from different sensory neurons are perceived according to what brain area they are connected.
- Neuronal activity in the auditory cortex is perceived as sound. Even blind subjects report seeing "light" if their visual cortex is stimulated directly.
Intensity of sensation is coded as __
the frequency of action potentials.
- The stronger the stimulus, the more frequently afferent neurons fire action potentials.
Some sensory receptor cells are organized with other cells in __, such as eyes and ears
__ include sensory cells, associated structures, and neural networks that process the info
(page 16 on slide)
diminishing response to repeated stimulation
- enables animals to ignore background conditions but remain sensitive to changing or new stimuli
- Some sensory cells don't adapt. (e.g. mechanoreceptors for balance, pain)
Mechanoreceptors called __ detect stimuli that are used in the CNS to maintain body balance & equilibrium and to monitor the position of the head and limbs.
__ fibers, activated by __ neurons give force to allow muscle to stretch. In the capsule, the __ muscle fiber is innervated by __ neurons. A __ neuron wraps around it, where __ proteins are found. Stretching of both fibers causes opening up of these proteins, causing a __
- receptor potential
When the extrafusal muscle stretches, the muscle intrafusal muscle stretches also. The sensory neuron senses that stretch via receptor proteins. When the receptor potential reaches threshold, an action potential occurs.
(page 22 on slide)
respond to harmful stimuli that result in pain
All sensory neurons and sense cells release __
Olfactory sensors are embedded in __. Odorants bind to __.
- epithelial tissue at the top of the nasal cavity (in vertebrates);
- receptor proteins on olfactory cilia
Olfactory receptor proteins are specific for particular odorants.
Olfaction: After cAMP binds to cAMP gated ion channel, what happens?
- Na+ & Ca2+ ions enter cell.
- Ca2+ binds to Cl- channel.
- Cl- ions leave cell due to electrochemical gradient.
- Sensory neuron becomes depolarized (more positive).
- Receptor potential occurs.
- Threshold is reached and action potential occurs.
(page 28 on slide)
Olfaction: Action potential signals are relayed in the __, which releases __ to the dendrites of the __ cell. The tracts then go to the __
glomerulus; glutamate; mitral; uncus
(The glomerulus & mitral cell are located in the olfactory bulb.)
(page 29 on slide)
steps in olfactory sensation
- 1. Odorants bind to receptor proteins.
- 2. Receptor potential occurs.
- 3. Sensory neurons reach threshold and fire an action potential.
- 4. Axons go to the glomerulus, which releases glutamate to the dendrites of the mitral cell.
- 5. Mitral cell undergoes action potential.
- 6. Tracts go to the uncus.
(Sensory info does not go to the thalamus.)
(page 29 on slide)
The inner ear has 2 sets of canals, the __ for balance & the __ for hearing.
vestibular system; cochlea
The __ collects vibratory energy and the vibrations first hit the __ in the auditory canal. The __ translates the vibrations to the __ of the cochlea.
- tympanic membrane;
- ossicles (mallleus, incus, stapes);
- oval window
The ossicles translate vibration of tympanic membrane to smaller movement by greater force at the small oval window. Movement of oval window is translated into pressure changes in the fluid-filled inner ear.
(page 31 & 33 on slide)
The higher the frequency of sound, the more the vibrational energy will __
take a shortcut across the basilar membrane to the round window. The basilar membrane deflects sooner.
(page 41 and 42 on slide)
mechanoreceptors in organs of hearing and equilibrium
- sense cells
The __ sits on the basilar membrane - transduce pressure waves into action potentials, contains hair cells with microvilli called __.
organ of Corti, stereocilia
Bending of stereocilia opens or closes ion channels.
The pressure changes from the __ is translated until the energy takes a shortcut across the __ to the __. Deflections occur, pushing the hair cells in the __ up against the immovable __. The __ kicks up, causing __ to come in, causing a __. Now the cell is more __. More neurotransmitter (Ca2+) is released to the __ in the brain
- oval window;
- basilar membrane;
- round window;
- organ of Corti
- tectorial membrane;
- receptor potential;
- medial geniculate body/nucleus (in thalamus)
(page 39, 41, & 45 on slide)
loss of function of tympanic membrane or ossicles
ex. ossicle hardening
damage to inner ear or auditory nerve pathways
Hair cells in the organ of Corti can be damaged by loud sounds.