Receptors and Senses

Amelia Hoyt

Relationship Between Receptors & Senses

The senses are a result of receptors-they are used to identify changes in the

environment-detecting/processing sensory information and generating motor responses is the physiological basis for all animal behavior

Pathways

Four basic functions:1 sensory reception2 transduction3 transmission4 perception-the ultimate effect of the wide range of

sensory receptors is to open/close ion channels

1) Sensory Reception

receptor:-a sensory cell or organ-a subcellular structure that interacts directly with stimuli

types of receptors:-mechanoreceptors-chemoreceptors-electromagnetic receptors-thermoreceptors-pain receptors

-sensory transduction: conversion of a physical or chemical stimulus to a change in the membrane potential of a sensory receptor

-receptor potential: change in the membrane potential itself

2) Transduction

3) Transmission

-for many receptors, transducing the energy in a stimulus into a receptor potential initiates transmission of action potentials to the Central Nervous System

4) Perception

-color, smell, sound, taste, touch-constructions formed in the brain: do not

exist outside of it

Sensory Systems

-hearing-sight-taste and smell

Hearing

-result of mechanoreceptors -related to perception of body equilibrium

(balance)-mechanoreceptor cells produce receptor

potentials when settling particles or moving fluid causes deflection of cell-surface structures

Sight

-ability of animals to detect light and other electromagnetic radiation

-underlying mechanism for capturing light is the same despite the use of a diverse set of organs -all contain photoreceptors: cells that contain light-absorbing pigment molecules

-genes for vision present among diverse groups

Taste and Smell

-gustation: taste-olfaction: smell-both depend on chemoreceptors that

detect specific chemicals in the environment

-for terrestrial animals, taste=detection of tastants and smell=detection of odorants

-no distinction between taste and smell in aquatic animals

Senses in Cnidarians

-Cnidarians lack image-forming eyes-rely on chemoreceptors to recognize the smell and taste of prey-rely on mechanoreceptors to recognize

the pressure and vibration of prey

Senses in the Annelida (polychaetes)

-receptors detect light, chemicals, pressure

-have ciliated structures believed to be chemoreceptors

-have eyes, which can form compound images

-some species have statocysts

Senses in the Arthropoda (insects)

-modified cuticles into a diverse number of receptors

-setae-pressure sensors -antennae-compound eyes and ocelli-some species have statocysts

Senses in Mammalia (humans)

-hearing & equilibrium closely related-five types of tastants: sweet, sour, salty,

bitter, umami-vision is well-processed to form images

in color and eyes have the ability to focus by changing the shape of the lens

-individual taste cells contain receptors that only recognize one specific tastant

Hearing Disorders

Otosclerosis:-unknown causes, but likely a genetic link-result of an abnormal sponge-like bone growing in

the middle ear, preventing it from vibrating in response to sound waves

-symptoms: progressively worse hearing, better hearing in noisy rather than quiet environments, sometimes tinnitus (ringing)

-diagnosis: audiometry/audiology, or temporal bone CT

-Treatment: hearing aid, fluoride, calcium, or vitamin D, surgery (stapedectomy or stapedotomy)

Age-related hearing loss-cause: the tiny hairs in the ear becoming damaged or dying; result of accumulation of factors-symptoms: certain sounds seeming overly loud, difficulty hearing in noisy areas, high-pitched sound distinction difficulty, voices seeming slurred, tinnitus-diagnosis: audiometry/audiology-treatment: hearing aids, alternate means

of communication, surgery (cochlear implant)

Vision Disorders

-myopia: "nearsighted" result of too long eyeball length or too steep cornea

-symptoms: poor ability to see at a distance

-diagnosis: vision test-treatment: glasses, contacts, refractive

surgery

-hyperopia: "farsighted"; result of too short eyeball or too flat cornea, hereditary condition

-symptoms: difficulty seeing objects up close

-diagnosis: vision test-treatment: glasses, contacts, refractive

surgery

Taste and Smell Disorders

-Anosmia: loss of smell, wide range of causes including infection, deformed nasal bones, tumors, malnutrition, surgery, certain nasal sprays, etc.

-symptoms: loss of smell-diagnosis: inability to detect odors for an

extended period of time-treatment: has to be for underlying

causes; no treatment for the condition itself

-Aguesia: loss of or impaired ability to taste; may be general, partial, or specific to some tastants; potentially caused by: loss of smell, infection, nerve damage, etc.-symptoms/diagnosis: loss of taste to some or all tastants, sometimes loss of smell-treatment: must be geared towards

underlying cause

Conclusion

Benefits of having a sensory system:-detection of danger-detection of prey-greater awareness of surroundings-sexual selection

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