Download Nervous System – Sensory Systems

Nervous System – Sensory Systems
Biol 105
Lecture 11
Chapter 9
Concepts to Know:
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 ______.
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Outline
I.
II.
III.
IV.
V.
VI.
Senses
Sensory receptors
Touch
Vision
Hearing and balance
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
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12.2 The Central Nervous System
12-18
12-28
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
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Optic nerve
Optic disk
(blind spot)
Fovea
Sclera
Choroid
Retina
Vitreous humor
(fills the posterior
chamber)
Lens
Ciliary body
Aqueous humor
(fills the anterior
chamber)
Cornea
Pupil
Iris
Sclera
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Figure 9.4
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
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Table 9.1 (1 of 4)
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
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Table 9.1 (2 of 4)
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
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Table 9.1 (3 of 4)
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
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Table 9.1 (4 of 4)
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
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Light
Choroid
Sclera
Retina
Blind spot
(a) Light enters the left eye
and strikes the retina.
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Figure 9.8a
Light
Vitreous
humor
Ganglion
cell layer
Electrical
signals
Bipolar
cell layer
Retina
Cone
Rod
Axons
Photoreceptor
cells
Pigment layer
Choroid
Sclera
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Figure 9.8b
Light
Retina
Optic nerve
Visual cortex
(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.
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Figure 9.8c
Rods and Cones
Rod cell
Cone cell
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Figure 9.9 (2 of 2)
Which part of the human eye detects colored light?
1.
2.
3.
4.
Pupil
Rods
Cones
Cornea
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A ring of muscle that functions to focus the lens on
the retina is the:
1.
2.
3.
4.
Iris
Choroid
Ciliary body
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
Outer
Inner
Middle
ear
ear
ear
(receiver) (amplifier) (transmitter)
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Figure 9.12 (1 of 2)
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
Outer ear
(receiver)
Middle ear
(amplifier)
Inner ear
(transmitter)
Eardrum
Malleus Incus Stapes
(tympanic membrane) (hammer) (anvil) (stirrup)
Vestibular apparatus:
Semicircular canals
Vestibule
Auditory nerve
Oval window
Cochlea
Round window
External auditory canal
Auditory tube
(Eustachian
tube)
The pinna gathers sound and
funnels it into the external
auditory canal to the tympanic
membrane (eardrum).
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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.
Figure 9.12 (2 of 2)
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
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Figure 9.13 (1 of 2)
Hearing Depends on the Ear
Tectorial
membrane
Hair cell
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Figure 9.13 (2 of 2)
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
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Figure 9.16a (1 of 2)
Balance Depends on the Vestibular
Apparatus
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Figure 9.16a (2 of 2)
The Vestibular Apparatus
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Figure 9.16b (1 of 2)
The Vestibular Apparatus
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Figure 9.16b (2 of 2)
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
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Figure 9.18
Important Concepts
 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?
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Important Concepts
 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.
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Important Concepts
 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?
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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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