chapter 38 pp Flashcards
Perceptions
Any sensory stimuli of which humans, and perhaps other animals, become conscious
Sensory receptors
Specialized cells capable of detecting changes in internal or external conditions, and of communicating that information to the central nervous system
Capable of facilitating sensory transduction (Conversion of an event (stimulus) occurring in the environment into a nerve impulse)
There is no difference between the nerve impulses carried by different types of sensory nerves.
Interoceptors
receive stimuli from inside the body.
exteroceptors
allow an animal to detect information in its environment
Chemoreceptors
Sensory receptors responsible for taste and smell
Photoreceptors
Sensory receptors responsible for responding to light
Mechanoreceptors
Sensory receptors stimulated by mechanical forces, such as pressure
Electromagnetic receptors
Respond to heat or light energy
Thermoreceptors
Sensory receptors stimulated by changes in temperature
Chemoreception
is found almost universally in all animals.
Thought to be the most primitive sense
Allows organisms to locate food, find a mate, detect dangerous environmental chemicals
Housefly chemoreceptors
are on their feet.
Can also detect airborne pheromones
Chemical messages passed between individuals
Snakes’ Jacobson’s organs
are in the roof of their mouths.
Send sensory information to the brain
taste buds
are located primarily on the tongue.
Taste buds open at a taste pore.
Taste buds have supporting cells and elongated taste cells that end in microvilli.
Five primary tastes
Sweet, sour, salty, bitter, and umami (savory)
Taste buds for each are located throughout the tongue, although certain regions may be more sensitive to particular tastes.
A food may stimulate more than one type of taste bud.
Brain surveys overall pattern of incoming impulses.
olfactory cells
human sense is dependent on this
Located within olfactory epithelium in the roof of the nasal cavity
Each cell ends in a tuft of cilia with receptor proteins for odor molecules.
Each cell has 1 out of 1,000 different types of receptor proteins
Photoreceptors
are sensory receptors that are sensitive to light.
Planaria
Eyespots” allow them to sense and move away from light.
Arthropods
Contain compound eyes composed of many independent ommatidia
Photoreceptors generate nerve impulses which pass to the brain by way of optic nerve fibers.
Insects have limited color vision compared to humans.
Many insects see some ultraviolet rays.
Allows them to see flower parts, nectar guides
camera-type eye
in Vertebrates and certain molluscs
Single lens focuses an image of the visual field on closely packed photoreceptors.
vertebrate lense vs mollusk lense
Vertebrate lens changes shape; molluscan lens moves back and forth.
Stereoscopic vision
(depth perception)
Found in animals with two eyesfacing forward
Common in predators; also in humans
Panoramic vision
(no overlap of images)
Wide visual field
Common in prey animals
The Human Eye 3 Layers
Sclera-Opaque outer layer
Choroid – Thin middle layer
Retina – Inner layer
Sclera
Fibrous layer covering most of the eye
In front of the eye, the sclera becomes the transparent cornea.
Conjunctiva – covers surface of the sclera and keeps the eyes moist
Choroid – Thin middle layer
Contains blood vessels
In front of the eye, the choroid thickens to form the ciliary body and the iris.
The iris regulates the size of the pupil.
The lens helps form images.
Attached to the ciliary body by ligaments
Retina – Inner layer
Contains photoreceptors called rod cells and cone cells
Contains the fovea centralis
Region of densely packed cone cells where light is focused
Vision is most acute
Blind spot
Where optic nerve exits retina, no vision is possible
ciliary muscle
Shape of lens is controlled by the ciliary muscle
distant object
ciliary muscle is relaxed; lens remains flat
far object
ciliary muscle is contracted; lens becomes more round
Rods permit vision in
low light
Peripheral vision and perception of motion
Cones permit vision in
bright light
Fine detail and color
Three types of cones, which contain B (blue), G (green), or R(red) pigments
