Sensory systems

Question 1

How to we get sensory information

Answer 1

Stimulation-stimulus impinges on a sensory receptor
transduction: energy from a sstimulus transformed into a graded potential in the associated sensory(afferent) neuron
Transmission: AP develops in axon of sensory neuron and it conduction to CNS
Interpretation: All nerve impulses are qualitatively alike, perception of stimulus is product of brain
6 classes of receptors:
thermoreceptors
Nociceptors
Electromagnetic receptors
Mechanoreceptors
Chemoreceptors
photoreceptors

Question 2

Thermoreceptors

Answer 2

sensitive to temp changes
-in vertebrates, most thermoreceptors are in the dermis
-Pit vipers(rattlesnakes) use thermoreception for the detection of prey. These organs are wired to the visual processing of the brain

Question 3

Nociceptors

Answer 3

impulses perceived as pain
-pain can be viewed as an adaptive mechanism to warn the body about damage
Overstimulation can also send signals as pain

Question 4

Electromagnetic receptors

Answer 4

sense eletric and magnetic fields
-all animals generate electric currents from contraction of their muscles. water is a good conduction of electricity, and thus many fish have the trait to detect electric fields

Question 5

Mechanoreceptors

Answer 5

touch, pressure, and body position
-several types of Mechanoreceptors detect mechanical distortions (touch)
-specialized sensors in skeletal muscle provide the body with feedback about body position
Vibrations, hearing, balance
-Lateral line in fish- allows fish to sense objects that reflect pressure waves and vibrations
hearing fish-otoliths in the head of fishes vibrate against hair cells. otoliths much denser than water
Terrestrial animals- a tympanic membrane (ear drum) vibrates in response to sound waves

Question 6

Hearing in humans

Answer 6

EAr drum vibrates, bones of inner ear (Malleus, incus, and stapes-evolved from bones in early mammalian jaw). oval window is the entrance to the cochlea to auditory nerves.
The eustachian tube is behind the eardrum, helps eardrum regulate pressure
1) vibration of the ear drum causes the bones of the inner ear to move: sound is amplified and transmitted to the oval window
2)oscillations of the oval window cause fluid in cohclea to move. Hair within cochlea vibrate and bend, sending impulses to sensory neurons-
loudness -depends on how many hair cells stimulated. frequency- is determined by location in cochlea where fibers in the basilar membrane resonate

Question 7

cochlea

Answer 7

oscillations of the oval window cause fluid in cohclea to move. Hair within cochlea vibrate and bend, sending impulses to sensory neurons-
loudness -depends on how many hair cells stimulated. frequency- is determined by location in cochlea where fibers in the basilar membrane resonate
-fibers vary in length and stiffness (short/stiff near the base of the cochlea) long/flexible near the apex.
High frequency sounds resonate with short fibers, low with longer

Question 8

low frequency/high

Answer 8

low goes farther
high doesnt travel as far

Question 9

Echolocation

Answer 9

Overcomes the problem of determining the location of sounds. speed of sound is a constant. location can be determined by the time is takes for the echo to return

Question 10

In mammal ears frequency is detected by

Answer 10

location along cohlea where hair cells in the basilar membrane resonate in response to sound the wavelength

Question 11

Balance and body position

Answer 11

Labyrinth of inner ear is a fluid-filled membranous chamber with semicircular canals
Linear motion- acceleration distorts the matric, causing hair cells to bend and stimulating sensory neurons
Angular motion- semicircular canal loops in a different plane
at the end of the semi canals are swollen chambers called ampullae withing this are hair cells.

Question 12

Chemoreceptors

Answer 12

contains proteins that bind with particular chemicals in the environment, causing depolarization of sensory neurons.
-terrestrial vertebrates use their tongue to taste
smell- specialized for detecting airborne particles, insects use antennae

Question 13

photoreceptors

Answer 13

sensory cells that detect electromagenetic wabes
-some animals have eyes that can detect light without forming an image (scallops, flatworms, seastarts)
-annelids, mollusks, antrohpods, vertebrades have evolved image-formining eyes.
Compounds-insect creating mosiac
camera type- focus light onto retina to have conitous imge

Question 14

Retina

Answer 14

contains rods- detect lo levels of light. hundreds may be on single nerve cell
cones- detect color when light there is enough light

Question 15

Fovea

Answer 15

region of keenest vision contains only cones in diurnal vertebrates
nocturnal animals often lack cones, black and white vision