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AP Bio Notes on Sensory and Motor Mechanisms
Sensations are actually ________that reach the brain from
a sensory cell via a sensory neuron. The ________determines if the information
is important enough to be passed on to other parts of the brain based on instructions from the
________. If so, the brain then ______the action potentials and gives
us the ________of the stimulus. The colors, sounds, smells, etc. that we sense
are ________of the brain! The ______region of the brain
determines the __________ of the information in our lives. ______can also change our perceptions.
Ex. Optical illusions
Sensory receptors can be ________which detect stimuli outside the body
such as heat, light or chemicals. Or they can be ________which detect stimuli
inside the body such as ________or body position.
4 steps in sensory response:
1. ________in which the stimulus energy is
changed into a change in membrane potential. This change is a ________
potential (stronger stimulus causes a greater change) and is called the _______
potential. The receptor potential can be created by ________the membrane in such a way that ions are able to flow through.
Ex. receptors that respond to touch or pressure
Or the ________molecules may attach to ______molecules in
the receptor cell membrane and open or close ________.
Ex. Taste or smell receptors
2. ________is produced by signal transduction pathways of the receptor cell.
Ex. sound waves are amplified 20 times
3. ______is the transport of the action potential to the CNS. This may be
done by ________being released from the receptor cell to a
_________. The strength of the stimulus and receptor
potential determine the ______ of neurotransmitter released.
Some sensory neurons continuously send signals, but their ________is
increased if the stimulus is stronger. Some receptor cells are actually sensory ______.
Ex. Pain receptor cells are sensory neurons, so they are more direct.
4. ________is the processing of the sensory information. The graded
potentials from the many receptors can be added together by ________.
Sensory __________is a decrease in responsiveness to a stimulus that keeps
being ________.
Ex. You don’t notice the feel of your clothes on your skin all the time or a certain smell after a while.
The ________of receptors can vary with conditions as the threshold of conduction can be changed.
Types of sensory cells
1. ________respond to touch, pressure, stretch, ________and
________. The stimulus bends or stretches the plasma membrane which makes it
________ __ permeable to K+ and Na+ which causes an action potential.
Ex. There are mechanoreceptors near the skin surface for ____________and
deeper in the skin for ________. At the base of hairs are other
touch receptors to detect movement of the ________for very light touch.
Skin diagram:
Muscle cells have interoreceptors called ________ or stretch receptors that detect stretching of the skeletal muscle.
Mechanoreceptors that detect motion often have ________which are
receptor cells with ________or microvilli that can be bent by the stimulus to
change their permeability to K+ and Na+ which causes an action potential. Some become
___________ permeable when bent the opposite way. This enables them to detect the direction of the motion.
Ex. Hair cells in the ears for motion
2. ______receptors are naked dendrites in the epidermis of the skin called
________. They can respond to excess ________, ______or certain chemicals such as acids. Prostaglandins increase pain.
Aspirin and ibuprofen work by __________ production of prostaglandins.
3. _________detect temperature changes.
4. ________detect certain kinds of molecules and also changes in total
____________concentration (osmoreceptors). Those involved with taste are
________receptors and those for smell are ________receptors. These 2
sets of receptors respond to related chemicals, _________ and taste are related. The
binding of the chemical to the _________ molecule changes membrane permeability.
5. ________receptors respond to visible ________,
______and electricity. Those that respond to light are called
________and are often found in eyes.
Ex. Snakes have ______receptors to detect the body heat of prey.
Ex. Some birds and bees have the mineral ______in their skulls to help them orient direction with Earth’s magnetic field.
Ex. Some fish release ______currents and detect how they bend to find prey.
Photoreceptors in animals
Many animals have the same types of ________cells to absorb light. The
simplest animals with photoreceptors are the ________. They are found in 2
curved ________ found on each side of the head. If the light enters from the side,
it stimulates only ________ eye cup. The planarian turns until the stimulus is equal and this
causes its movements to be _________ from the light.
Diagram:
______ such as insects, crustaceans and polychaeta worms have a
________eye with several thousand light sensors called ______.
The many receptors provide the animal with a ________image which makes it easy
to detect ________.
Other invertebrates such as jellyfish, spiders and octopus have a ________
______eye which is like a pinhole camera. The eye has an opening called the _______
to let light in and an ________which adjusts the size of the opening. A ________
focuses the light onto the ______where the pigment containing receptor cells are found.
Vertebrates also have ________eyes.
The Vertebrate Eye
Diagram:
______- clear protective layer over the iris and pupil which helps focus light a little.
______- Opening to let light enter the eye.
______- Colored part of the eye that changes the size of the pupil to control how much light enters the eye.
______- Focuses the light on the retina.
________produces aqueous humor (liquid that fills the space between the cornea and lens).
______muscles change the shape of the lens to focus light.
______- jellylike substance between the lens and retina which gives the eye shape and helps focus light.
______- White outer protective covering of the eye.
_________- a thin layer of epithelial cells over the sclera to produce mucus to keep the eye moist.
______________- A thin pigmented inner layer between the sclera and retina. Collects extra light rays that enter the eye.
______- contains photoreceptors called ______and ______that change light
energy into electrical signals. The light is focused onto a spot on the retina called the
________ at the center of the field of vision.
______- respond to _________ light because they are more sensitive than cones. Used
for ___________ and white vision. Humans have over 20 times __________ rods than cones. (125 million rods vs. 6 million cones)
______- Respond to ___________light. Used for ______ vision.
There are ______kinds of cones that each respond to different __________ of light.
People who are ____________ have 1 or more of these types of cones that do not work
properly. The most cones are found at the _________.
Most mammals have poor color vision because most are ________and
have more of the sensitive rods. Primates, including humans have the __________
color vision of mammals. Birds also have very __________ color vision.
Our rods are found mostly on the ________of the eye and are not found
in the __________ at all. (So you can see a dim star only in your peripheral vision, but not if you try to look directly at it!)
The optic _________ carries signals from the rods and cones in the retina to the thalamus, then to the occipital lobe of the cerebral cortex to be processed.
____________ - An area of the eye where there are no photoreceptors because the optic nerve is there.
Focusing light
The light is focused on the fovea by ________the shape of the lens. When looking
at a distant object the lens is _________as the ciliary muscles ______
which allows the choroids to expand and put tension on the suspensory ligaments which
________on the lens to flatten it. When looking at close up objects, the ciliary muscles
_________which pulls the choroids owards the lens, relaxing the ______
ligaments and allowing the elastic lens to become ________.
A person who is ________ (can’t see far away) has an eye that is too ______, so the light is focused in front of the retina.
A person who is far-sighted (can’t see ________up) has an eye that is too ______so the light focuses behind the retina.
Diagram:
Near sighted Far sighted
Lenses are used to change the ________so that the light is focused on the fovea of the retina.
Diagram
Near sighted Far sighted
How rods work
Each rod or cone has a stack of folded _________in it that have visual
_________embedded in them. The visual pigments have 2 parts: a
light-absorbing pigment molecule called ________(which is made from
vitamin _____) and a protein called an ________. When the opsin of the rod
is combined with retinal, it makes the visual pigment ________.
Diagram of a rod
In the dark, ________ (cGMP) is
attached to the _________ ion channels of the rod to keep them _______.
This causes them to be ________and to release the neurotransmitter
_________at its synapses with the ________cells in the retina.
There are ______kinds of bipolar cells. Some are ________by glutamate and others
are excited by ___________, depending on which kind of ____________ each has.
Diagram of rod cell in the dark:
When light hits rhodopsin, its ____________changes shape and breaks off from the
________. This also change the ______of the opsin. This process is
called the ________of rhodopsin. The opsin is now _________
and it activates a relay molecule called ________.
Transducin is a ________in the signal transduction pathway. Transducin
activates an ________which changes cGMP to ______which breaks off
from the Na+ channels, causing them to ________. Now the membrane
______so the neurotransmitter glutamate is no longer released. This again
changes the activity of the ________cells to send the message to the brain.
Diagram:
In color vision, the cones have pigments called ________which come in 3 kinds
– red, green and blue (based on the color they ___________ best). Their absorption
spectra ________so 2 can be stimulated by one color and give us many intermediate
colors depending on which _________and how ______are responding.
Transmission to the brain
The axons of the rods and cones synapse with the ________cells which in turn
synapse with _________cells. The ganglion cells’ axons join to form the
________which leads to the brain. This is called the
________pathway. However, there are other cells which can
_________ the information to several bipolar or gangion cells. This is called
the ________pathway. The lateral pathway involves ________
cells which take the information from one rod or cone and give it to several ________
cells. Also, __________ cells give the information from one bipolar cell to several
________cells. When a horizontal cell is stimulated, it ______
the more distant rods or cones which causes the light spot to appear ___________ and
the dark near it to appear darker. This is called ______and helps sharpen edges and give more contrast in the image.
Diagram:
The optic nerves coming from each eye meet at the ________.
Near the center of the base of the cerebrum. Some of the nerves ________
at the optic chiasm so information from each eye goes to ________ sides of the brain.
Most of the axons of the optic nerves go to the _________in the brain.
From there, ________take the information to the primary visual
cortex of the _________lobe of the cerebrum for processing.
Diagram:
Hearing
The ear is used for hearing and ______.
Diagram of the human ear:
Sound is ______in the air. The vibrations enter the ______
______which carries them to the ______(ear
drum). The tympanic membrane vibrates, which vibrates 3 bones in the ________
ear: the ______, then incus, then ______bone. The middle ear
also connects to the _________which connects to the
pharynx for equalizing ____________between the ear and the outside
world. (This is why your ears pop when going up in an airplane.) The vibrating
stapes bone moves the membrane of the ____________which moves
the fluid inside the ______(in the inner ear). The cochlea has 3 chambers, the
upper ________canal, the lower ______canal and
the ____________between them. The fluid in the
vestibular and cochlear canals is called ________and the fluid in the
cochlear duct is called _________. The floor of the cochlear duct
contains the ________where the actual hair cells
involved in hearing are located. The hair cells are attached to the ________
membrane at their base and their tips can be brushed against the ________membrane as the basilar membrane vibrates.
Diagram of inner ear:
As the ______inside the cochlea are vibrated by the cochlear
fluid moving the basilar membrane, they brush against the __________
membrane. This causes them to ________. The bending causes them to
become permeable to ______, which enters and causes the hair cells to depolarize. The
hair cells release _________to the ______
nerves to create action potentials in them. Auditory nerves carry impulses to the
______which sends them to the ______lobe of the cerebral
cortex to be interpreted. The pressure of the moving fluid is released by the bulging
outward into the middle ear of the ________window at the end of the cochlea.
Interpreting sound
How loud a sound is will be detected by the ________of action potentials that
are created. A loud sound will cause sound waves with a greater _________
(height of the sound wave) which will cause _________vibrations of the
fluid and basilar membrane so the hair cells will bend ________.
The pitch (highness or lowness) of the sound is detected by __________ hair cells
are stimulated. The basilar membrane varies in its _________and
flexibility. The part near the oval window is ________and stiffer so it vibrates
more with ________pitched sounds. The part at the far end of the basilar
membrane is thicker and more ________so it vibrates best with lower pitched sounds.
Diagram:
Hair cells that respond to ____________ frequencies are easily damaged. They are not
replaced. Loss of these hair cells make it hard to hear _________, especially those of women.
Balance and body position
Also in the ________ear is the ______containing the
______and ______. They tell the brain which way is _____