Nervous System – Sensory Systems
Biol 105
Lecture 11
Chapter 9
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1. Depolarization is caused by ______ ions entering or leaving (which one) the axon
1. The gap in between two neurons is called the ________.
2. What is the name for the chemicals that are held in vesicles and released from one neuron, and bind to receptors of the next neuron?
3. What part of the autonomic nervous system stimulates digestion?
4. What is the thin outer layer of the cerebrum where most of the higher thinking and processing takes place called
5. The part of the brain that processes sensory information (except smell) is called the ______.
Concepts to Know:
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Outline
I. Senses
II. Sensory receptors
III. Touch
IV. Vision
V. Hearing and balance
VI. Smell
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Senses
Major senses – touch, hearing, smelling, taste, and seeing.
All the sensory nerves are routed through the thalamus except the nerves for smell.
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Sensory receptor cells
Sensory receptors are specialized structures that detect stimuli (stimulus)
Sensory receptor cells change the stimulation into an electrical response that is transmitted through the nerves
If a sensory receptor is continuously stimulated, it will stop responding = sensory adaptation
12.2 The Central Nervous System
12-18
12-28
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Touch
We can sense different things through touch:
Thermal Tactile Pain Vibration
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Figure 9.2 Sense receptors of the skin
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Figure 9.2 Sense receptors of the skin
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Types of receptors in the skin
Free nerve endings Merkel disks Meissner’s corpuscles Pacinian corpuscles Ruffini corpuscles Thermoreceptors
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Free Nerve Endings
Free nerve endings – tips of dendrites of sensory neurons (free nerve endings may be wrapped around hair), detect touch and pain
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Figure 9.2 Free nerve endings
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Figure 9.2 Free nerve endings
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Merkel Disks
Merkel disks – comprised of free nerve endings and Merkel cells, detect touch
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Merkel disk
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Meissner’s corpuscles
Meissner’s corpuscles – encapsulated nerve endings - detect light touch, tell us exactly where we were touched
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Meissners corpuscle
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Pacinian corpuscles
Pacinian corpuscles – layers of tissues surround the nerve ending, detects pressure when first applied, important in sensing vibration
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Pacinian corpuscle
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Ruffini corpuscles
Ruffini corpuscles – encapsulated nerve endings in deep layers that respond to continuous pressure
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Ruffini corpuscle
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Thermoreceptors
Thermoreceptors – specialized nerve endings, detects changes in temperature.
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Vision
Sight is complex:
Light enters the eye, it is focused, then the light has to be transformed into it into an electrical signal that then has to be processed.
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Vision
Light enters through the cornea
The lens focuses it to the back of the eye
The retina is a layer at the back of the eye where light is transformed into electrical signals
Copyright © 2009 Pearson Education, Inc. Figure 9.4
Retina
FoveaOptic disk(blind spot)
Optic nerve
Choroid
Sclera
Vitreous humor(fills the posteriorchamber)
Iris
Ciliary body
Pupil
Cornea
Aqueous humor(fills the anteriorchamber)
Sclera
Lens
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Layers of the Eye – Outer layer
The sclera Protects and shapes the eye Provides attachment for muscles
The cornea
Allows light to enter
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Outer Layer of Eye
Table 9.1 (1 of 4)
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Middle Layer of Eye
The choroid
Contains blood vessels that supply nutrients and oxygen.
Contains melanin, absorbs light reflected from the retina
The ciliary body
A ring of muscle that functions to focus the lens on the retina
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Middle Layer of Eye
The iris
The colored portion of the eye Contains smooth muscle that dilates or constricts
to regulate the amount of light entering the eye
The pupil
The opening in the center of the iris that lets light into the eye
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Middle Layer of the Eye
Table 9.1 (2 of 4)
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Inner Layer of Eye
Contains: Retina Photoreceptors - Rods and Cones Fovea
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Inner Layer of Eye - Retina
The retina contains photoreceptors Rods Cones – detect color
The fovea is a pit in the retina with a high concentration of cones
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Vision Depends on the Eye
Table 9.1 (3 of 4)
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Structures of the Eye
Optic Nerve Fluid
Aqueous humor Vitreous humor
Lens
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Optic Nerve
The optic nerve
Carries visual information to the brain Forms a blind spot where it leaves the retina
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Fluid in the Eye
There are two fluid filled chambers in the eye
Vitreous humor – jelly like fluid in posterior chamber. Holds retina against the wall of the eye
Aqueous humor – clear fluid in anterior chamber. Supplies nutrients and oxygen to cornea and lens, removes the waste. Creates pressure in eye to maintain shape of eye.
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Lens
The lens can change shape to focus on near and far objects.
Focuses the light onto the retina
Ciliary muscles are attached to lens by ligaments
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Vision Depends on the Eye
Table 9.1 (4 of 4)
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Photoreceptors
Cones and Rods have pigments that absorb
Cones work best in bright light and provide color vision
Rods work in low light situations but can only provide black and white vision
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Photoreceptors
The photoreceptors (rods and cones) have pigments that absorb light
When there is no light coming in, they are releasing neurotransmitters (opposite of most receptors)
When they absorb light they stop releasing neurotransmitters
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Photoreceptors
The neurotransmitters are inhibitory
When the neurotransmitters diminish, cells that process the information are stimulated
This information from these cells (bipolar and ganglion cells) is transmitted to the optic nerve to the thalamus to the visual cortex
Copyright © 2009 Pearson Education, Inc. Figure 9.8a
(a) Light enters the left eye and strikes the retina.
Light
Retina
Choroid
Sclera
Blind spot
Copyright © 2009 Pearson Education, Inc. Figure 9.8b
Ganglioncell layer
Bipolarcell layer
Retina
Photoreceptorcells
Pigment layer
Choroid
Sclera
Rod
Electricalsignals
Axons
Cone
Light
Vitreoushumor
Copyright © 2009 Pearson Education, Inc. Figure 9.8c
(c) The axons of the ganglion cells leave the eye at the blind spot, carrying nerve impulses to the brain (viewed from below) by means of the optic nerve.
Retina
Light
Optic nerve
Visual cortex
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Rods and Cones
Figure 9.9 (2 of 2)
Rod cell
Cone cell
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Which part of the human eye detects colored light?
1. Pupil
2. Rods
3. Cones
4. Cornea
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A ring of muscle that functions to focus the lens on the retina is the:
1. Iris
2. Choroid
3. Ciliary body
4. Sclera
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Figure 9.10 A standard test for color blindness
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Vision
Vision is much more complicated because these signals have to be processed into a 3-D image
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Hearing
Sound enters the ear canal and hits the tympanic membrane (ear drum).
The tympanic membrane vibrates.
This causes small bones in the ear to vibrate.
These bones focus and amplifies the vibrations onto a small place (oval window) on the cochlea.
The cochlea is a fluid filled coiled membrane.
The vibrations shakes the fluid in the cochlea
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Three regions of the ear
Outer ear – the receiver
The middle ear – the amplifier
The inner ear – the transmitter
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Three Regions of the Ear
Figure 9.12 (1 of 2)
Outerear(receiver)
Middleear(amplifier)
Innerear(transmitter)
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The Outer Ear
Consists of the:
Pinna – gathers the sound, acts like a funnel
External auditory canal – brings the sound from pinna to the tympanic membrane
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Middle Ear
Consists of the:
The tympanic membrane separates the outer ear from the middle ear, vibrates when sound waves hit it.
Three auditory bones – amplify the vibration Malleus Incus Stapes
Auditory tube (eustachian tube) – equalizes pressure between outer and middle ear
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Middle Ear
The tympanic membrane vibrates when sound waves hit it and transmits the vibration to the malleus
The vibrations are amplified by the three bones and transmitted to the oval window
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Parts of the Inner Ear
Oval window – transmits sound from the stapes to the fluid in the cochlea
Round window – relieves pressure
Cochlea – contains the receptor cells that transform the signal from vibration to an electrochemical signal to the neurons.
Vestibular apparatus – monitors position of the head
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Hearing Depends on the Ear
Figure 9.12 (2 of 2)
The pinna gathers sound and funnels it into the external auditory canal to the tympanic membrane (eardrum).
The eardrum vibrates synchronously with sound waves, causing the bones of the middle ear to move.
The three bones of the middle ear amplify the pressure waves and convey the vibrations of the eardrum to the inner ear.
The cochlea converts pressure waves to neural messages that are sent to the brain for interpretation as sound.
Malleus(hammer)
Incus(anvil)
Stapes(stirrup)
Semicircular canals
Vestibular apparatus:
Auditory nerve
Cochlea
Oval window
Eardrum(tympanic membrane)
Round window
Auditory tube(Eustachiantube)
Outer ear(receiver)
Middle ear(amplifier)
Inner ear(transmitter)
External auditory canal
Vestibule
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Cochlea
It is in the cochlea where vibrations are transformed into electrical signals that can be sent by neurons
When the fluid in the cochlea moves, it moves small “hair cells” against a membrane. This allows ion channels to open
This leads to the release of neurotransmitters, which trigger the neuron to send the message
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Hearing Depends on the Ear
Figure 9.13 (1 of 2)
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Hearing Depends on the Ear
Figure 9.13 (2 of 2)
Hair cell
Tectorialmembrane
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In the ear, the fluid filled coiled membrane that is responsible transforming the vibrations into electrical signals. This structure is:
1. Tymphanic membrane
2. Staples
3. Cochlea
4. Incus
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The tympanic membrane transmits the vibration to the ___.
Stapes Malleus Incus Oval window
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The Vestibular Apparatus
Balance depends on the vestibular apparatus of the inner ear
The vestibular apparatus is a fluid-filled maze of chambers and canals within the inner ear
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The Vestibular Apparatus - Dynamic equilibrium
Fluid filled cupulas at base of the semicircular canals have hair cells that are stimulated when head moves. Hair cells send message to the brain.
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The Vestibular Apparatus - Static equilibrium
Otoliths are small chalk like granules
When head is tilted the otoliths move and stimulate hair cells that send message to the brain
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Balance Depends on the Vestibular Apparatus
Figure 9.16a (1 of 2)
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Balance Depends on the Vestibular Apparatus
Figure 9.16a (2 of 2)
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The Vestibular Apparatus
Figure 9.16b (1 of 2)
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The Vestibular Apparatus
Figure 9.16b (2 of 2)
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Smell - olfaction
Sensory nerves for smell go directly to the cerebral cortex and to the amygdala and the hypothalamus.
They do not pass through the thalamus
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Smell - olfaction
Odor molecules bind to the receptors in the cilia of olfactory receptor cells
The receptor cells send the message to the neurons in the olfactory bulb which carry the message to the brain.
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Figure 9.17 Sense of Smell
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Figure 9.17 Sense of Smell
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Taste
Taste and smell is very connected.
The tongue has taste buds on them
The taste buds have taste cells (receptor cells) in them
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Taste
Food molecules bind to taste cells and stimulate them. The taste cells send the messages to the sensory neurons which send the message to the brain.
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Smell and Taste
Figure 9.18
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Read Chapter 6
What is the function of sensory receptor cells?
What is an example of sensory adaptation?
What are the types of senses of touch?
What are the types of sensory receptors in skin, what type of touch do they detect, be able to describe them?
Important Concepts
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What are all of the layers and structures (including the fluids) of the eye and what are their functions?
What is the blind spot?
How does the signal travel from the photoreceptors to the brain, what part of the brain receives the signal? Be able to describe in detail this process, including the cells that transmit the messages.
Important Concepts
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What are all the parts of the ear, are they part of the inner, middle or outer ear, and what is their functions? What is the path of sound waves and vibrations through the ear
How does the ear detect head movement and position?
How do we detect odor? What part of the brain receives the signal? Where are olfactory receptors found?
How do we detect tastes? What structures are responsible for taste?
Important Concepts
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Definitions
stimuli (stimulus), sensory adaptation, dilates, constrict, bipolar cells, ganglion cells, photoreceptors, transmits, amplifies, otoliths, cupula, taste buds,
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