Chapter 41: Sensory Systems Flashcards
What is echolocation?
bats use this to see in the dark. They send out sound waves and then the waves bounce off objects and the bats can then put together a picture of their surroundings.
gives them secondary vision
What is a stimulus?
a change in the internal or external environment that can be detected by the organism’s body
What detects a stimulus?
sensory receptors
What are the 5 basic types of receptors?
mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, nociceptors
What is a mechanoreceptors? ex? found in?
Detect mechanical energy when it deforms membranes, physical movement of receptor
ex) auditory receptors in the ears
found in skin, skeletal muscles, walls of blood vessels, and internal organs
What is a photoreceptors? ex?
detect the energy of light
ex) found in retina of eye
What is a chemoreceptors? ex?
detect specific molecules or chemical conditions (acidity)
ex) taste buds on the tongue
What is a thermoreceptors? ex?
detect the flow of heat energy
ex) temperature receptors in the skin
What is a nociceptors? ex?
detect tissue damage or noxious chemicals, register their activity as pain
ex) pain receptors are located in the skin and in some internal organs
What is a receptive field?
a region in which the receptor responds to a stimulus
What are some of the disadvantages of free nerve endings?
they are not as sensitive b/c stimulus has to hit the free nerve exactly
a nerve “pad” increases the receptor field which increases sensitivity
What is signal transduction?
conversion of a stimulus into a receptor potential
What do photons use for communication?
they use transduction, they are not neurotransmitters
What are the 2 ways intensity of a stimulus are registered?
1) frequency of action potentials
2) number and types of afferent neurons that the stimulus activates to generate action potentials in the pathway
What is sensory adaptation?
the frequency of action potentials generated in afferent neurons is reduced when the intensity of a stimulus remains constant
increases the sensitivity of receptor systems to changes in environmental stimuli, which may be more important to survival than constant factors
How does perceptions differ from reality?
- Lack receptors for some types of energy (e.g., X-rays)
* Sensory input is processed in various ways
How does a mechanical stimulus work?
creates tension in the plasma membrane of a receptor which causes ion channels to open, producing a receptor potential
What are the types of receptors for touch and pressure human skin has?
free nerve endings, Pacinian corpuscles, Ruffini endings, and Meissner’s corpuscles
What do free nerve endings respond to?
light touch
What do pacinian corpuscles respond to?
deep pressure and vibrations—- warning signals
What do ruffini endings respond to?
deep pressure
What do meissner’s corpuscles respond to?
light touch and surface vibrations
What are proprioceptors
a mechanoreceptor that detect stimuli used in the CNS to maintain body balance and equilibrium and to monitor the position of the head and limbs
What are muscle spindles?
bundles of specialized muscle cells wrapped with the dendrites of afferent neurons
cerebellum uses this info
What is the vestibular apparatus?
in the inner ear responsible for perceiving the position and motion of the head
made of three semicircular canals, the utricle, and the saccule – all filled with a fluid called endolymph
What are the semicircular canals?
detect rotational (spinning) motions
What is an ampulla?
each semicircular canal has an ampulla at its base, topped with sensory hair cells that synapse with afferent neurons
What are sterocilia?
Microvilli (stereocilia) extend into a gelatinous cupula which protrudes into the endolymph of the canals
When the head rotates, displacement of the cupula bends the sensory hair cells – depolarization causes release of neurotransmitters, which trigger action potentials—–allows Na+ to rush in
What is the otolitic membrane?
The utricle and saccule contain sensory hair cells covered with a gelatinous otolithic membrane in which small crystals of calcium carbonate (otoliths) are embedded
What is the orientation of the sensory hairs when the animal is upright?
sensory hairs in the utricle are oriented horizontal – those in the saccule are vertical
What is the orientation of the sensory hairs when the animal is tilted?
sensory hairs bend and action potentials are generated
What is the lateral line system?
Fishes and some aquatic amphibians detect vibrations and currents in water through a series of mechanoreceptors in the lateral line system
What are neuromasts?
In fish, the mechanoreceptors (neuromasts) also provide information about orientation with respect to gravity and swimming velocity
What are statocysts?
fluid-filled chambers with walls that contain sensory hair cells enclosing one or more movable stonelike bodies (statoliths)
When the animal moves, statoliths lag behind the movement, bending the sensory hairs and triggering action potentials
Statocysts signal the brain about the body’s position and orientation with respect to gravity
What is sound?
vibrations that travel as waves made by alternating compression and rarefraction of the air
What does the loundness/intensity of a sound depend on?
amplitude of the wave
What does the pitch (how high/low a sound makes) of sound depend on?
frequency of the waves
How do invertebrates detect sound?
through mechanoreceptors in their skin or other surface structures
How do some insects detect sound?
have complex auditory organs on either side of the abdomen or on the first pair of walking legs
These organs consist of a thinned region of the insect’s exoskeleton that forms a tympanum over a hollow chamber
Sounds reaching the tympanum cause it to vibrate – mechanoreceptors connected to the tympanum translate the vibrations into nerve impulses
What is the outer ear?
external structure (pinna) which concentrates and focuses sound waves
Sound waves enter the auditory canal and strike the tympanic membrane (eardrum), which vibrates in response
What is the middle ear?
contains three small, interconnected bones: the malleus (hammer), incus (anvil), and stapes (stirrup)
What is the oval window?
The stapes fits within an elastic membrane (oval window) and is held in place by a ligament
What is the inner ear?
contains the semicircular canals, utricle, saccule, and the cochlea – a spiraled tube
What is the structure of the cochlea?
divided into three longitudinal chambers: the vestibular canal, the cochlear duct, and the tympanic canal
What is the organ of Corti (spiral organ)?
Within the cochlear duct, the organ of Corti (spiral organ) contains sensory hair cells that detect sound vibrations
What is the round window?
At the end of the tympanic canal, sound waves are transmitted to another membrane, the round window
What is the basilar membrane?
forms part of the floor of the cochlear duct, anchors sensory hair cells in the organ of Corti
When the basilar membrane vibrates, the stereocilia are bent in relation to the stationary tectorial membrane
What is the tectorial membrane?
Stereocilia of these cells are embedded in the tectorial membrane, which extends the length of the cochlear canal
What is the cochlear nerve?
carries information through intermediate regions to the thalamus, which routes signals to specific regions in the temporal lobe, which then integrates the information
How are sensory hair cells arranged?
Sensory hair cells in a particular location in the basilar membrane are tuned to a particular sound frequency (pitch)
What is the eustachian tube?
(also called the auditory tube), a duct that leads from the air-filled middle ear to the throat
protects the tympanic membrane from damage by changes in environmental atmospheric pressure
What does stopped-up ears a result of?
When swelling or congestion due to infections prevents the tube from admitting air, we complain of having stopped-up ears— we can sense that a pressure difference between the outer and middle ear is bulging the tympanic membrane, interfering with the transmission of sounds and causing pain
What is retinal?
All animals use forms of a single pigment, retinal (synthesized from vitamin A), in photoreceptors to absorb light energy
How do earthworms see?
Earthworms have photoreceptors in their skin that allow them to sense and respond to light
How do planarians see?
have a cuplike ocellus which detects light but does not form an image – photoreceptor cells are connected to dendrites of afferent neurons, which are bundled into nerves that travel from ocelli to the cerebral ganglion
Planarians orient themselves so that the amount of light falling on their two ocelli is equal and diminishes as they swim
What is rhodopsin?
a photopigment (retinal bound to opsin) which absorbs light and causes action potentials to be generated
How do compound eyes work? what organisms are they found in?
found in insects and crustaceans
they contains many faceted visual units (ommatidia) fitted closely together. Light entering an ommatidium is focused by a transparent cornea and crystalline cone onto photoreceptor cells
The brain receives a motion-sensitive mosaic image
How do single-lens eyes work? what organisms are they found in?
found in vertebrates
Light enters through the cornea, a lens concentrates the light, and a layer of photoreceptors (retina) records the image
Muscles in the iris adjust the size of the pupil to vary the amount of light entering the eye
Muscles move the lens to focus on objects at different distances (accommodation)
What is the choroid?
inside of the sclera and is darkly pigmented
What is the purpose of the ciliary body?
changes the shape of the lens to focus light from distant or nearby objects on the retina (accommodation)
Is the lens flat or round when fousing on objects close up?
lens is rounded
Does light pass through neurons or photoreceptors first?
neurons
How many rods and cones does the human retina contain? how are they arranged?
120 million rods and 6 million cones organized into a densely packed, single layer
What is the fovea?
The image focused by the lens is centered on the fovea, a small region of the retina where cones are concentrated
How does the fovea change for animals and birds with night vision?
they lack a defined fovea
What is in the peripheral vision?
rods
How do the rods of mammals differ from other organisms?
The rods of mammals are much more sensitive than cones to low-intensity light
What are the 3 parts of a photoreceptor?
An outer segment consisting of stacked, flattened, membranous discs
An inner segment where metabolic activities occur
The synaptic terminal, where neurotransmitter molecules are stored and released
What is retinal bonded to?
opsins
What happens to the retinal of rhodopsin in the dark?
In the dark, the retinal of rhodopsin is inactive (cis-retinal) and the rods steadily release the neurotransmitter glutamate
What happens to the retinal of rhodopsin in the light?
When rhodopsin absorbs a photon of light, retinal converts to its active form, trans-retinal, and the rods decrease the amount of glutamate they release
What is the pathway for rhodopsin?
Rhodopsin is a membrane-embedded G-protein-coupled receptor – activated rhodopsin triggers a pathway that leads to the closure of Na+ channels in the plasma membrane
Closure of the channels hyperpolarizes the photoreceptor’s membrane, decreasing neurotransmitter release
The response is graded – as light absorption increases, the amount of neurotransmitter released is reduced proportionately
What are the 4 types of neurons in the retina of mammals?
bipolar cells, ganglion cells, horizontal cells, and amacrine cells
What are bipolar cells?
where processing of visual information begins and Rods and cones form synaptic
connections
What are ganglion cells?
receive signals from bipolar cells – axons of ganglion cells collect at the back of the eyeball to form the optic nerve
What are horizontal cells?
integrate inputs from multiple photoreceptors – lateral to the region of light reception
Visual processing through horizontal cells (lateral inhibition) sharpens the edges and enhances contrast in an image
What are amacrine cells?
receive inputs from bipolar cells and excite ganglion cells
How does light exposure effect bipolar cells?
In the light, decrease in neurotransmitter release from rods and cones results in hyperpolarization of depolarized bipolar cells and depolarization of hyperpolarized bipolar cells
Pathway from bipolar cells to ganglion cells?
Signals from rods and cones move vertically from bipolar cells to ganglion cells – each ganglion cell receives signals from a defined set of photoreceptors (its receptive field)
How many types of cones do humans have?
3, each containing one of three different photopigments in which retinal is combined with different opsins
blue, green, and red
What does Light that stimulates all three receptor types equally seen as?
white
What is the lateral geniculate nuclei?
Most axons enter the lateral geniculate nuclei in the thalamus, where they synapse with interneurons leading to the visual cortex
What percent of the cerebral cortex in humans is devoted to visual information?
almost 1/3
Where in the body is afferent neurons most concnetrated?
the two optic nerves
What is another name for taste?
gustation
What is another name for smell?
olfaction
What forms the basis for smell and taste?
chemoreceptors
What do chemoreceptors do?
measure the internal levels of molecules such as oxygen, carbon dioxide, and hydrogen ions
How do insects taste?
In insects, taste receptors occur inside hollow sensory bristles (sensilla) on the antennae, mouthparts, or feet
Pores in sensilla admit molecules to the chemoreceptors, which are specialized to detect sugars, salts, amino acids, or other chemicals
Where do many female insects have chemoreceptors? function?
on their ovipositors, which allow them to lay eggs on food appropriate for the hatching larvae
Where is information from taste receptors usually processed?
parietal lobes
Where is information from smell receptors usually processed?
olfactory bulbs and temporal lobes
How are olfactory receptors structured?
One end of each olfactory receptor cell has sensory hairs that project into a mucus layer that dissolves airborne molecules
The other end synapses with interneurons in the olfactory bulbs – olfactory receptors are the only receptor cells that make direct connections with brain interneurons
What are papillae?
In humans, taste buds are embedded in outgrowths of the tongue called papillae
What are taste buds?
the sensory hairs of taste receptors pass through the pore of a taste bud and project to the exterior
Pathway taste receptors relay their signals to?
thalamus
From the thalamus, some signals lead to gustatory centers in the cerebral cortex, which integrate them into the perception of taste – others lead to the brain stem and limbic system
What are the 5 basic human tastes?
sweet, sour, salty, bitter, and umami (savory)
At the phylogenetic level, what does the arrays of olfactory receptor genes in vertebrate groups show?
appear to have changed rapidly; the changes relate to each organism’s environment
What type of nerve endings do thermoreceptors and nociceptors have?
Both types of receptors consist of free nerve endings formed by dendrites of afferent neurons, with no specialized receptor structures surrounding them
What types of thermoreceptors do mammals have?
Mammals have five thermoreceptor ranges, beginning at less than 8°C and extending to above 52°C – the extremes are perceived as painful
How do invertebrates (insects) and snakes use thermoreceptors?
to detect warm-blooded prey
snakes use put organs to do this function
How does the hypothalamus of mammals function as a thermoreceptors for the brain?
highly sensitive to shifts from normal body temperature, and trigger involuntary responses such as sweating, panting, or shivering, which restore normal body temperature
Which division of the nervous system are nociceptors part of?
somatic system of the PNS
What neurotransmitters do nociceptors pathways activate?
glutamate or substance P
What do glutamate-releasing axons produce?
sharp, prickling sensations that can be localized to a specific body part
Do pain receptors adapt?
Pain receptors adapt very little or not at all – some gradually intensify the rate at which they send out action potentials if the stimulus continues at a constant level
How does the the CNS combat pain?
release endorphins that bind to receptors on substance P neurons, reducing the amount of neurotransmitter released
What are magnetoreceptors and what animals use them? what do they use them for?
Migrating butterflies, beluga whales, sea turtles, homing pigeons, and foraging honeybees have magnetoreceptors that allow them to detect and use Earth’s magnetic field as a source of directional information
What are electroreceptors and what animals use them? what do they use them for?
Many sharks and bony fishes, and some amphibians and mammals, have specialized electroreceptors that detect electrical fields
Electrical stimuli detected by the receptors are used to locate prey or navigate around obstacles in muddy water – or, by some fishes, to communicate
can be used to kill prey ex) electric eel
What are the 2 types of electroreception systems?
Some electro reception systems are passive–they detect electric fields in the environment, not the animal’s own electric currents – passive systems are used mainly to find prey
Other electro reception systems are active–the animal emits and receives low voltage electrical signals that are generated by special electric organs
