Sensory Reception Flashcards

Sensory Reception

• Sensory Reception Steps:
  1. Reception
  2. Transduction (converting signal to electrical signal)
  3. Transmission
  4. Perception
• Small adjectives of sensory stimulus:
  • Modality: type
  • Location potential
  • Intensity: coded by action, duration frequency

Modalities

• Chemoreceptors: respond to chemicals
  • Olfaction: sense of smell - detection of chemicals in air.
  • Gustation: sense of taste - detection of ingested chemicals
    • Salty (Na+)
    • Sour (H+)
    • Sweet (sugar)
    • Umami (amino acid)
    • Bitter
• Mechanoreceptors: respond to movement
  • Touch/pressure: tactile receptors
  • Baroreceptors
  • Proprioceptors
  • Equilibrium
    • Hair cells

Transduction of Sound

1. High pressure
2. Stereocilia bends
3. Potassium channels open
4. Membrane depolarizes
5. Calcium goes in
6. Synaptic vesicles released

• Tectorial membrane
• Basilar membrane
• Axons of sensory neuron
• Inner ear
• Higher-lower frequency
• Wide-narrow

Equilibrium

• Vestibular apparatus
• Orientation
• Acceleration
• Rotation
• Vestibulo-Cochlear nerve
• Anterior canal
• Saccule
• Cochlea
• Lateral canal
• Semicircular canals
• Posterior canal

Photoreceptors (mechanoreception)

• Rods: sensitive to dim light
• Cones: detect color
• Lens focuses light onto retina
• Lens is controlled by ciliary muscles (accommodation)

Light Transduction

• Rhodopsin protein complex changes shape conformation for light
• Retinal from 11-cis retinal to all-trans retinal
• In dark: rhodopsin inactive, cGMP high
• In light: photon activates rhodopsin, decreases cGMP via phosphodiesterase

Other Senses

• Thermoreceptors: warm, cold, painful temperature
• Nociceptors: register pain -> polymodal (temp, pressure, chemical)
• Electroreceptors: detect electric field
• Magnetoreceptors

Additional Information

• Red/Green Color Blindness: caused by absence of M or L cones
• Cones control colors in eyes; rods control light
• Monosodium Glutamate - triggers umami
• Olfactory bulb: part of brain where olfactory signals are processed/interpreted
• Each olfactory neuron has only one type of receptor
• Glomeruli
• Modality = types
• Fish lateral line = pressure changes in water
• Statocysts

Sound Transduction Details

• Pressure waves pass through the air in the ear canal
• The tympanic membrane (eardrum) vibrates
• The malleus (ear bone) vibrates
• The incus (ear bone) vibrates
• The stapes (ear bone) vibrates
• The oval window vibrates
• Pressure waves travel through the fluid cochlea
• Stereocilia in the hair cells deflect (bend)
• K+ channels in the hair cell membranes open
• The hair cell membrane is depolarized
• Voltage-gated $Ca^{2+}$ channels open
• The hair cell releases neurotransmitter
• Afferent neurons transmit action potentials through the cochlear nerve

Flash of Light Pathway

1. Photons pass through cornea
2. Photons are refracted by the lens
3. Photons pass through the ganglion and bipolar cells in the retina
4. A photon is absorbed by a retinal molecule
5. Rhodopsin changes shape to its active conformation
6. Transducin molecules bind GTP
7. Transducin molecules activate phosphodiesterases
8. Phosphodiesterases break down cyclic GMP
9. cGMP-gated $Na^{+}$ channels close
10. The rod is hyperpolarized

Additional Sensory Structures

• Ampullae of Lorenzini: detects electrical fields in water
• Lateral line: senses water pressure/movement using hair cells
• Basilar membrane: vibrates in different locations in response to different frequencies of sound
• Vomeronasal organ: detects airborne odorants and pheromones
• Ommatidium: detector of light coming from a particular direction
• Ear bones: incus, stapes, malleus

Sensory Coding and Modalities

• Transduction: conversion of a signal to the control center
• Transmission: sending a signal to effector
• Sensory coding: modality (type), location, intensity
• Modalities: chemoreceptors or mechanoreceptors
• Olfaction: cochlea
• Gustation: vestibular apparatus
• Echolocation
• Gustafication: are able to detect different tastes - sweet, salty, umami, bitter, sour - by chemical composition.
  • Sweetness is detected by sugars,
  • Saltiness is detected by $Na^{+}$ ions,
  • Umami is detected by amino acids,
  • Bitterness is determined genetically,
  • Sourness is determined by acidity ($H^{+}$ ion)
• Smell is transmitted to the brain by olfaction receptors, a type of chemoreceptor; the odorant (stimulus) is received by the odorant receptor and sent to the olfacting bulb for processing. Each smell has a distinct neuron/receptor.

Sensory Systems

• Lateral line system: used by aquatic organisms to sense pressure; made of a system of canals connecting to hair cells, which activate sensory neurons (water flows through). The hair cell is above the neuron, with stereocilia connecting to kinocilium/cupula.
• Sound transduction: Sound waves go through the ear canal, to the typanic membrane/eardrum, which vibrate; then, the signal goes through the middle ear cavity by vibrations.
• Waves travel through fluid to reach the cochlea by the oval window, which vibrates in response to waves. Once the wave reaches the cochlea, the pressure is sensed by hair cells via the stereocilia. Hair cells transmit the signal by K+ of the membrane which open the pump depolarizing charging (release neurotransmitter. to the cochlear nerve.

Vision

• The eye transduces light to retina by light transduction (cones & rods)
• Optic nerve - in retina
• Light is reflected through the lens and passes through cornea to reach the retina; ganglion cell, then to the bipolar cell,
• Retinal molecules inside rhodopsin change shape (opsin) to active - trans-conformation in rods to receive color/vision. $100 \rightarrow trans$ for opsin, a retinal protein, has different types for different absorption ranges; each of the three types have "absorption scale"
• A neuron leading from the retina to the brain induces a rhodopsin-transducin change to trans conformation, where the GTP binds to cGMP triggering hyperpolarization since cGMP levels are low in response to light.