L8- Special Senses Flashcards
Transducer
Converts one energy to another form of energy
Sensory transduction
Converts a sensation into an action potential
- occurs in sensory receptors
What are the structural categories of sensory receptors?
- Free nerve endings
- Encapsulated nerve endings
- Specialized receptor cells
Free nerve ending sensory receptors
- normal dendrites
Sense: Pain, temperature, light touch,
Encapsulated nerve endings
- enclosed dendrites
Ex) pacinian corpuscle - pressure
Meissner’s corpuscle - light touch
Specialized receptor cells are
Rods and cones - light
Hair cells - balance & equilibrium
What are the two functional categories of sensory receptors?
- Type of energy transduced
- Type of information sent to brain
Thermoreceptors
Temperature
Mechanoreceptors
Deformation
Photoreceptors
Light
Chemoreceptors
Chemical
Nociceptors
Tissue damage ( pain receptors)
Proprioceptors
Body position, fine motor control
Ex) muscle spindle - stretch reflex
Golgi tendon organ - tension in tendon
Cutaneous receptors
Skin sensations
- touch/ pressure
- hot/cold
- pain
Special senses
Input from outside world (found in head region)
- sight, hearing, sound, taste, smell
Properties of sensory receptors
- Specificity
- binding due to specific characteristics - Sensitivity
- ability to detect low levels of energy - Range fractionation
- large range, of sensory input - Acuity
- discrimination- detecting two inputs
Receptive field
Region in the sensory periphery that will stimulate a sensory neuron
Difference b/w a small receptive field and a large receptive field
Small = more sensory neurons ➡️ more area in primary somatosensory field
Large = less amount of sensory receptors (neurons)
How is sensory information coded?
- Stimulus type
- receptors are stimulus specific - Intensity
- Ap frequency - Location
- Duration
- AP still arriving = stimulus present
- AP not arriving = stimulus isn’t present
Two ways of adaptation of sensory receptors
- Phasic receptors
- Tonic receptors
Phasic receptors
Fast adapting
- adapt to constant stimulus or fire when stimulus is applied/ removed ( after image)
Ex) odor, touch, temperature
Tonic receptors
Slow adapting / non adapting
Ex) pain
What are the two types of general senses?
Somatic sensory & visceral sensory
Somatic sensory input is from
Skin, skeletal muscle, joints
Visceral sensory input
Is from internal organs
What are the three regions of the ear?
Inner ear, middle ear, outer ear
Outer ear
Auricle to the tympanic membrane
Middle ear
Air filled space, 3 ossicles, opening of Eustachian tube
Inner ear contains
Houses bony labyrinth/ membranous labyrinth
(3 semicircular canals, vestibule, cochlea)
Membranous labyrinth
Fluid filled tubes/sacs inside bony labyrinth
Perilymph
Surrounds membranous labyrinth
Endolymph
Within the membranous labyrinth
The bony labyrinth within the inner ear contains what three structures? What about the membranous labyrinth?
Bony labyrinth = 3 semicircular canals, vestibule, cochlea
Membranous labyrinth = 3 semicircular ducts, utricle & saccule, cochlear duct
What is the sensory receptor found in the membranous labyrinth?
Hair cells
Hair cells
Sensory receptor of hearing & equilibrium
Vestibular apparatus
Organ of equilibrium
What structures are apart of the vestibular apparatus?
- Semicircular Canals- sense angular acceleration (spin)
- Saccule & utricle - sense verticals/horizontal acceleration (linear)
Vestibular apparatus function(s)
- spatial orientation: tells brain where head is in space
- perception of self motion
- prevents falls & dizziness
What happens when hair cells are bent to the left? The right?
Bend left = increase AP to temporal lobe
Bend right = decrease AP to temporal lobe
What houses the hair cells?
Crista ampullaris
What cause the semicircular canals to sense movement
Endolymph inside membranous labyrinth moves the cupula (gel) causing hair cells in crista ampullaris to move
What is inside the ampulla (space)
Crista ampullaris
- cupola (gel)
Hair cells
Utricle
Hair cells in macula sense horizontal acceleration
Saccule
Hair cells in macula sense verticals acceleration ( up & down)
Otolith
Calcium carbonate (crystals)
Otolith membrane
Gel
Macula
Hair cells
External ear function for hearing
Channel sound waves to tympanic membrane
Middle ear function for hearing
amplify sound waves ( malleus, incus, stapes vibrating against each other) producing fluid waves in inner ear
Inner ear function for hearing
Cochlea transduces fluid waves into action potentials
- fluid waves in perilymph bend stereocilia of hair cells ➡️ Ap down vestibulocochlear nerve
Transmission of sound waves through the ear
- Sound waves vibrate tympanic membrane
- Vibrates ear ossicles
- Pushes oval window in/out
- Creating fluid waves in perilymph of scala vestibuli
- Vibrating vestibular membrane
- Vibrating basilar membrane on which hair cells are
- Bends stereocilia of hair cells that are embedded in tectorial membrane ➡️ Ap to vestibulocochlear nerve
Every time hair cells bend, it creates an action potential.
True or false
True
Sound waves
Disturbance of air molecules
What cause a sound wave? What are its properties?
Compression - air coming closer together
Rare fractions - expanding air out
Frequency (wavelengths
Pitch
Amplitude
Volume
How is pitch coded?
The basilar membrane respond to frequencies of sound
Base = high frequency
Apex = low frequency
How is volume coded in the ear?
- coded by frequency of action potentials
Soft = decreased frequency of Ap
Loud= increase frequency of AP
Spinal organ
Functional unit of hearing
Sound wave transduction by hair cells
- fluid move,ent in cochlear duct
- hair cells bend (in tectorial membrane)
- opens mechanically gated k+ channels
- k+ diffuses into hair cell depolarizing cell membrane
- opening voltage gated ca2+ channels
- ca2+ diffuse into cell ➡️exocytosis of NT ➡️diffuse NT
- binds to ligand gated na+ channel (receptor in sensory neuron)
- if reaches threshold potential ➡️ action potential in sensory neuron to cochlear nerve
