chapter 38: sense organs Flashcards
what are sensory receptors
Structure that receives either external or internal environmental stimuli and is a part of a sensory neuron or transmits signals to a sensory neuron
what is sensory transduction
conversion of a stimulus into a nerve impulse by using a receptor
what is perception
sensory stimulation we are aware of
what are the four main kinds of sensory receptors
-chemoreceptors
-photoreceptors
-mechanoreceptors
-thermoreceptors
what is a chemoreceptor
sensitive to chemical stimulation (taste & smell)
what are photoreceptors
respond to light (vision)
what are mechanoreceptors
respond to mechanical stimuli (pressure, sound waves, & gravity)
what are thermoreceptors
receptor that detects heat
how do sensory receptors in animals work
-Perceive very different ways
-Snakes detect infrared energy
-Bats, dolphins, whale echolocation
-Dogs sense of smell is incredibly strong
characteristics of chemoreceptors
-Chemoreceptors are universally found in animals
-Most primitive sensory receptors to have developed in animals - evolved the longest - huge variety
examples of chemoreceptors locations in animals
-Planarians: concentrated on the auricles of the head in planaria
-Arthopods: found on antennae and mouthparts in insects and other arthropods
-Fish: scattered across skin
-Snakes: Jacobson’s organs
how does human sense of taste work
-10,000 taste buds located primarily tongue along walls of papillae (small elevations)
-Taste receptors are located within taste buds in humans
-Taste buds: structure in vertebrate mouth containing sensory receptors for taste
-Generate nerve impulses in associated sensory nerve fibers
how does sense of smell in humans work
-Olfactory cells: modified neuron that is a sensory receptor for smell
-Each cell ends in a tuft of cilia
-1 out of 1,000 different types of receptor proteins
-Odor can contain many odor molecules
-Olfactory bulb direct connections with limbic system
-Emotions & vivid memories
-Smell & taste work together
how does the sense of vision work
-Photoreceptors differ in complexity in different kinds of animals
-Simplest only recognize presence & intensity of light
-Eyespots in planaria allow the direction of light to be determined
-Compound eye (Arthropods) many different visual units called ommatidia
how do animals detect light
-Some fish, reptiles, & most birds color vision
-Camera-type eyes: Type of eye found in vertebrates and certain mollusks; a single lens focuses an image on closely packed photoreceptors
what kind of animals have stereoscopic vision and why
predator, allows to lock onto target
very good at perceiving objects at different angles
what kind of animals have panoramic vision and why
prey - seeing predators with large field of visionq
how does focusing of the eye work
-Light rays pass through pupil & focused on retina
-Brain processes image in correct orientation
-Shape of lens is controlled by ciliary muscle: muscle that controls shape of lens
two kinds of photoreceptors
rods and cones
characteristics of rods
-Night vision
-Peripherial vision & motion
-sensitive to light
-100s of rods are connected to one cell, so the brain cant distinguish between individual cells and the images are not very detailed
characteristics of cones
-Primarily in fovea centralis
-Fine detail & color
-B (blue), G (green), & R (red) pigments
-each cone is attached to one cell, providing a detailed image to the brain
how do impulses get from the retina to the visual cortex
-Fibers synapse with neurons in nuclei within thalamus
-Take nerve impulses to visual area within occipital lobe
-Image inverted & reversed
-Corrected in visual regions of the brain
how does the sense of hearing and equilibrium work
-Mechanoreception sensing physical contact or movement in environment
-Receive information at distance
-Avoid danger, detect prey, find mates, ect
how does sense of hearing in insects work
Tympanum – a thin membrane stimulated to vibrate by sound waves that directly activates nerve impulses in attached receptor cells
