Chapter 45- Sensory Systems Flashcards
Sensory Receptors overview
provide information from internal and external environments
exteroceptors
sense external stimuli
interoceptors
sense internal stimuli
3 classes of Receptors
- mechanoreceptors
- chemoreceptors
- electromagnetic receptors
Mechanoreceptors
stimulated by mechanical forces such as pressure
- receptors in skin
- respond to stimuli at border btwn internal and external envir.
Chemoreceptors
detect chemicals or chemical changes
-ex. smell, taste
Electromagnetic receptors
react to heat and light energy
-ie. vision, heat
4 step process of CNS perceivance
- Stimulation-of sensory receptor cells
- transduction-in sensory receptor cells
- Transmission-along one or more sensory neurons
- interpretation-in CNS
Receptor potential
- sensory cells respond to stimuli via stimulus-gated ion channels in membrane
- if stimulus is of sufficient magnitude, a depolarization of the receptor cell occurs
Nociceptors
- mechanoreceptor
- transmit impulses perceived as pain
- most consist of free nerve endings located throughout body, especially surface
Thermoreceptors
- mechanoreceptor
- naked dendritic endings of sensory neurons that are sensitive to changes in temp.
- cold receptors located higher in skin
2 types of mechanoreceptors that respond to touch
- phasic-intermittently activated, hair follicles
- tonic-continuously activated
Proprioreceptors
- monitor muscle length and tension
- provide info about relative position or movement of animals body parts
Baroreceptors
- monitor blood pressure
- located at carotid sinus and aortic arch
- detect tension or stretch in the walls of these blood vessels
- when blood pressure decreases the frequency of barometric impulses decreases
Hearing (what is it)
- detection of soundwaves
- sound is the result of vibration traveling through a medium
- detection is possible through action of specialized mechanoreceptors in inner ear
lateral line system in fish
- consists of hair cells within longitudinal canal in the fishs skin
- hair cells are innervated by sensory neurons that transmit impulses to brain
How does vertebrate hearing occur
- tympanic membrane vibrates causing movement in malleus, incus, and stapes
- stapes vibrates against oval window
- pressure waves vibrate through cochlea
- depolarizes hair cells which send action potentials to brain
Echolocation
- mammals that can perceive presence and distance of objects by sound
- bats, shrews, whales, dolphins
Statocyst
invertebrates use this to orient themselves with respect to gravity
Utricle and Saccule
gravity receptors in vertebrates consisting of two chambers (as mentioned) in the membranous labyrinth
- utricle is more sensitive to horizontal acceleration
- saccule is more sensitive to vertical acceleration
Vestibular Apparatus
- saccule, utricle and semicircular canals
- together they detect gravity changes
Chemoreceptors
- bind to particular chemicals in the extracellular fluid
- membrane of sensory neuron becomes depolarized and produces action potentials
- used in the senses of taste and smell
- important in monitoring chemical composition of blood
Gustation
- Taste
- mixture of physical and psychological factors
- taste buds are collections of chemosensitive cells associated with afferent neurons
5 categories of taste
- sweet
- sour
- salty
- bitter
- umami (hearty)
Olfaction
- involves neurons located in upper portion of nasal passages
- receptors project into nasal mucosa, and their axons project directly into the cerebral cortex
- particles must first dissolve into extracellular fluid before they can activate the olfactory receptors
Vision
- begins with capture of light by photoreceptors
- used to determine both direction and distance of object
Flatworm eyes
-can perceive direction of light but no visual image
what 4 phyla have well developed image forming eyes
- annelids
- mollusks
- arthropods
- chordates
Sclera
white portion of the eye, formed of tough connective tissue
Cornea
-transparent portion through which light enters, begins to focus light
Iris
colored portion of the eye
-contraction of the iris muscles in bright light decreases the size of its opening, the pupil
Lens
transparent structure that completes focusing of light onto the retina
Near vs. Far vision
- lens is attached to ciliary muscles, changes shape of lens
- near vision=ciliary muscles contract-more bending of light
- far vision=ciliary muscles relax-less light bending
Rods
- on retina
- responsible for black and white vision when illumination is dim
Cones
- on retina
- responsible for color vision and high visual acuity
- momst are located in central region of retina known as focea
Basic structure of rods and cones
- inner segment rich in mitochondria and vesicles filled with neurotransmitter molecules
- packed with hundreds of flattened disks which contain photopigments
Photopigment in rods
rhodopsin
Photopigment in cones
photopsins
-3 kinds of cones
3 layers of retina
- external layer contains rods and cones
- middle layer contain bipolar cells
- layer closest to eye cavity contains ganglion cells
- -photoreceptors activate bipolar cells which activate ganglion cells which transmit impulses to brain via optic nerve
What happens to eyes in the dark
- photoreceptor cells release an inhibitory neurotransmitter that hyperpolarizes the bipolar neurons
- prevents the bipolar neurons from releasing excitatory neurotransmitter to the ganglion cells that signal to the brain
What happens to eyes in the light
- photoreceptor cells stop releasing their inhibitory neurotransmitter, in efect, stimulating bipolar cells
- bipolar cells in turn stimulate the ganglion cells, which transmit action potentials to the brain
Visual Processing
- action potentials in the optic nerves are relayed from the retina to the lateral geniculate nuclei of the thalamus
- then projected to the occipital lobes of cerebral cortex
Color blindness
- lack of one or more types of cones
- sex linked recessive trait
- people with normal vision are trichomats
Binocular vision
- primates and most predators have 3 eyes on each side of face
- 2 fields of vision overlap (binocular vision)
- prey have eyes on both sides of head
Detection of electrical currents
-elasmobranches (sharks, rays, skates) have electroreceptors called ampullae of lorenzini that sense electrical currents generated by muscle contractions of prey
Detection of Magnetic fields
-eels, sharks, bees and many birds appear to navigate along the magnetic field lines of earth
