CHAPTER 49: SENSORY AND MOTOR MECHANISMS By: Nicole Huffman Period 7.
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Transcript of CHAPTER 49: SENSORY AND MOTOR MECHANISMS By: Nicole Huffman Period 7.
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CHAPTER 49 :SENSORY AND MOTOR
MECHANISMS
By:
Nicole Huffman
Period 7
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KEY TERMS
Sensations: action potentials that reach the brain via sensory neurons.
Perception: constructions formed in the brain and do not exist outside it
such as colors, smells, sounds, and tastes.
Sensory Reception: the detection of a stimulus by sensory cells.
Sensory Receptors: are specialized neurons or epithelial cells that exist
singly or in groups with other cell types in sensory organs.
Exteroreceptors: sensory receptors that detect stimuli coming from outside
the body.
Interoreceptors: detect stimuli coming form within the body, such as blood
pressure and body position.
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KEY TERMS CONTINUED…
Sensory Transduction: the conversion of stimulus energy into a change
in the membrane potential of a sensory receptor.
Receptor Potential: the change in membrane potential itself.
Amplification: the strengthening of stimulus energy by cells in sensory
pathways.
Sensory Adaptation: a decrease in responsiveness during continued
stimulation.
Mechanoreceptors: sense physical deformation caused by stimuli such
as pressure, touch, stretch, motion, and sound – all forms of mechanical
energy.
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KEY TERMS CONTINUED…
Muscle spindles: dendrites of sensory neurons that spiral around the
middle of small skeletal muscle fibers each containing 2 to 12 of these
fibers surrounded by connective tissue, parallel to other muscle fibers.
Chemoreceptors: include both general receptors that transmit
information about the total solute concentration of a solution and specific
receptors that respond to individual kinds of molecules.
Electromagnetic Receptors: detect various forms of electromagnetic
energy, such as visible light, electricity, and magnetism.
Photoreceptors: electromagnetic receptors that detect the radiation
known as visible light.
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KEY TERMS CONTINUED…
Thermoreceptors: respond to heat or cold, help regulate body
temperature by signaling both surface and body core temperature.
Pain Receptors/Nociceptors: a class of naked dendrites in the
epidermis.
Lateral Line System: mechanoreceptors that detect low-frequency
waves by a mechanism similar to the function of the inner ear.
Compound eyes: consists of several thousand light detectors called
ommatidia.
Sclera: a touch, white outer layer of connective tissue.
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KEY TERMS CONTINUED…
Choroid: a thin, pigmented inner layer
Conjunctiva: A delicate layer of epithelial cells forms a
mucous membrane that covers the outer surface of the
sclera and helps keep the eye moist.
Cornea: At the front of the eye and lets light into the eye
and acts as a fixed lens.
Iris: The anterior choroid that gives the eye its color.
Pupil: the hold in the center of the iris.
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KEY TERMS CONTINUED…
Retina: the innermost layer of the eyeball and contains
the photoreceptors.
Ciliary Body: produces the clear watery aqueous humor
that fills the anterior cavity.
Vitreous Humor: fills the posterior cavity and constitutes
most of the volume of the eye.
Fovea: the center of the visual field.
Retinal: a light-absorbing molecule.
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KEY TERMS CONTINUED…
Opsin: a membrane protein.
Rhodopsin: a visual pigment in rods.
Photopsins: the three visual pigments of cones.
Ganglion cells: synapse with bipolar cells and transmit
action potentials to the brain via axons in the optic nerve.
Horizontal cells and Amacrine cells: help integrate
the information before it is sent to the brain.
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KEY TERMS CONTINUED…
Lateral Inhibition: sharpens edges and enhances
contrast in an image.
Hydrostatic Skeleton: a skeleton consisting of fluid
held under pressure in a closed body compartment.
Skeletal Muscle: muscle attached to the bones and
is responsible for their movement.
Accommmodation: the focusing of light in the retina.
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SENSORY RECEPTORS
Figure 49.2a
(a) Crayfish stretch receptors have dendrites embedded in abdominal muscles. When the abdomen bends, muscles and dendrites
stretch, producing a receptor potential in the stretch receptor. The receptor potential triggers action potentials in the axon of the stretch
receptor. A stronger stretch produces a larger receptor potential and higher frequency of action potentials.
Muscle
Dendrites
Stretchreceptor
Axon
Mem
bran
epo
tent
ial (
mV
)
–50
–70
0
–70
0 1 2 3 4 5 6 7
Time (sec)
Action potentials
Receptor potential
Weakmuscle stretch
–50
–70
0
–70
0 1 2 3 4 5 6 7
Time (sec)
Strongmuscle stretch
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(b) Vertebrate hair cells have specialized cilia or microvilli (“hairs”) that bend when sur-rounding fluid moves. Each hair cell releases an excitatory neurotransmitter at a synapse
with a sensory neuron, which conducts action potentials to the CNS. Bending in one direction depolarizes the hair cell, causing it to release more neurotransmitter and increasing frequency
–50
–70
0
–70
0 1 2 3 4 5 6 7
Time (sec)
Action potentials
No fluidmovement
–50
–70
0
–70
0 1 2 3 4 5 6 7Time (sec)
Receptor potential
Fluid moving inone direction
–50
–70
0
–70
0 1 2 3 4 5 6 7Time (sec)
Fluid moving in other direction
Mem
bran
epo
tent
ial (
mV
)
Mem
bran
epo
tent
ial (
mV
)
Mem
bran
epo
tent
ial (
mV
)
“Hairs” ofhair cell
Neuro-trans-mitter at synapse
Axon
Lessneuro-trans-mitter
Moreneuro-trans-mitter
Figure 49.2b
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Electromagnetic Receptors
• Electromagnetic receptors detect various forms of electromagnetic energy– Such as visible light, electricity, and
magnetism
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DIVERSE PHOTORECEPTORS
Eye cups
Compound Eyes
Single-lens eyes (used by vertebrates)
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HUMAN RETINA
Rods are sensitive to light but do not distinguish
colors
Cones distinguish colors but are not sensitive
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Rod Cells are light sensitive but do not distinguish
colors
Cone Cells are not as light sensitive as rods but
provide color vision and are mostly concentrated on
the fovea
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The absorption of light by rhodopsin initiates a
signal-transduction pathway
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CONES
Have 3 subclasses and more complex than the
rhodopsin mechanism.
Each has its own type of photopsin.
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RETINA, CEREBRAL CORTEX AND PROCESSING VISUAL INFO
Visual processing begins with rods and cones
synapsing with bipolar cells which then synapse with
ganglion cells.
Visual processing in the retina also involves
horizontal cells and amacrine cells.
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Lateral pathways involving horizontal or amacrine cells
can inhibit adjacent pathways:
Photoreceptors horizontal cells other photoreceptors
Photoreceptors bipolar cells amacrine cells ganglion
cells
The resulting lateral inhibition (More distance
photoreceptors and bipolar cells are inhibited sharpens
edges and enhances contrast in the image)
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The optic nerves of the
two eyes meet at the
optic chiasm.
Ganglion cell axons
make up the optic tract.
Most synapse in the
lateral geniculate nuclei
of the thalamus
The neurons then
convey information to
the primary visual cortex
of the optic lobe
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Vibrations create pressure waves in the fluid in the
cochlea that travel through the vestibular canal and
strike the round window
Cochlea
Stapes
Oval window
Apex
Axons ofsensoryneurons
Roundwindow Basilar
membrane
Tympaniccanal
Base
Vestibularcanal Perilymph
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Cochlea(uncoiled) Basilar
membrane
Apex(wide and flexible)
Base(narrow and stiff)
500 Hz(low pitch)1 kHz
2 kHz4 kHz
8 kHz16 kHz(high pitch)
Frequency producing maximum vibration
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EAR AND BALANCE
Behind the oval window is a vestibule that contains
the utricle and saccule
The utricle opens into three semicircular canals
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Utricle and saccule respond to changes in head
position relative to gravity and movement in one
direction.
Hair cells are projected into a gelatinous material
containing otoliths.
Semicircular canals respond to rotational
movements of the head
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Most fish and
amphibians have a
lateral line system along
both sides of their body
Provides a fish with
information concerning
its movement through
water or the direction
and velocity of water
flowing over its body.
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INVERTEBRATES WITH GRAVITY SENSORS AND
SOUND THAT ARE SOUND-SENSITIVE
Statocysts are mechanoreceptors that function in
an invertebrates sense of equilibrium
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INSECTS
Sound sensitivity in insects depends on body hairs
that vibrate in response to sound waves.
Many insects have a tympanic membrane stretched
over a hollow chamber
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TRANSDUCTION IN TASTE RECEPTORSTaste pore Sugar molecule
Sensoryreceptorcells
Sensoryneuron
Taste bud
Tongue
G protein Adenylyl cyclase
—Ca2+
ATP
cAMP
Proteinkinase A
Sugar
Sugarreceptor
SENSORYRECEPTORCELL Synaptic
vesicle
K+
Neurotransmitter
Sensory neuron
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MAMMALS’ OLFACTORY RECEPTORS LINE THE UPPER
PORTION OF THE NASAL CAVITY
The binding of odor molecules to olfactory receptors
initiate signal transduction pathways involving a G-protein-
signaling pathway and, often, adenylyl cyclase and cyclic
AMP.
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THE KEY TO FLIGHT IS THE AERODYNAMIC STRUCTURE OF
WINGS
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PERISTALTIC MOTION PUSHES AGAINST HYDROSTATIC
SKELETON
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When myosin
binds to actin it
forms an ATPase
which releases
the energy from
ATP for
contraction
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Graded muscle
contraction can be
controlled by regulating
the number of motor
units involved in the
contraction
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Recruitment of motor neurons increases the
number of muscle cells involved in a contraction.
Some muscles, such as those involved in posture
are always at least partially contracted.
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FAST AND SLOW MUSCLE FIBERS
Fast muscle fibers are adapted for rapid powerful
contractions and fatigue relatively quickly
Slow muscle fibers are adapted for sustained
contraction
Relative to fast fibers, slow fibers have:• Less SR → Ca2+ remains in the cytosol longer• More mitochondria, a better blood supply, and
myoglobin
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OTHER MUSCLE TYPES
Vertebrates have cardiac and smooth muscles
Invertebrate muscle cells are similar to vertebrate
skeletal and smooth muscle cells
Cardiac muscle: is similar to skeletal muscle• Intercalated discs facilitate the coordinated
contraction of cardiac muscle cells.• Can generate their own action potentials of long
duration.
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MUSCLE TYPES CONTINUED…
Smooth muscle: lacks the striations seen in both
skeletal and cardiac muscle.• Contracts with less tension, but over a greater range
of lengths, than skeletal muscle.• No T tubules and no SR
• Ca2+ enters the cytosol from via the plasma membrane
• Slow contractions, with more control over contraction strength than with skeletal muscle.
• Found lining the walls of hollow organs.
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Skeletal, voluntary or striated muscles are multinucleated, innervated by somatic nervous system
Skeletal, voluntary or striated muscles are multinucleated, innervated by somatic nervous system
Smooth or Viceral muscles are long and spindle shaped, innervated by two nerve fibers from autonomic nervous system, one from the sympathetic and one from the parasympathetic nervous system
Smooth or Viceral muscles are long and spindle shaped, innervated by two nerve fibers from autonomic nervous system, one from the sympathetic and one from the parasympathetic nervous system Cardiac muscle is
branched with intercalated discs
Cardiac muscle is branched with intercalated discs
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