Find People – Resources
Transcript of Find People – Resources
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Chapter 50:
Sensory / Motor
Mechanisms
Pathway of a stimulus:
Campbell et al. – Figure 50.2
Ability to distinguish stimuli depends on the brain:
• Sensations: Electrical impulses that reach the brain via sensory neurons
• Perceptions: Interpretation of electrical impulses by the brain
Chapter 50: Sensory / Motor Mechanisms
(1) Reception
Receptor detects
stimuli
Exteroreceptors (external)
Interoreceptors (internal)
(2) Transduction
Stimuli converted to
electrical impulse
(3) Transmission
Signal conducted
to CNS
Amplification
Strengthening of
stimulus signal
Intensity = AP frequency
Low
intensity
High
intensity
(4) Summation
Integration of
signal by CNS
Sensory Adaptation
Decrease in
responsiveness
over time
Sensory receptors are categorized by the type of energy they transduce:
1) Mechanoreceptors: Stimulated by physical deformation (e.g., touch)
• Muscle spindles = stretch receptors monitoring skeletal muscle length
• Hair cells = receptors detecting motion (e.g., hearing)
2) Nociceptors (pain receptors): Stimulated by inflamed / damaged tissue
3) Thermoreceptors: Stimulated by heat / cold
4) Chemoreceptors: Stimulated by specific molecule types
• Osmoreceptors = detect changes in [solute]
• Gustatory (taste) / Olfactory (smell) receptors
5) Electromagnetic receptors: Stimulated by electromagnetic energy
Heat
Magnetic Field
Chapter 50: Sensory / Motor Mechanisms
Light
Photoreceptors and Vision:
Invertebrates:
Allows for detection of light
intensity / directionality
B) Image-Forming Eyes:
• Accurate at detecting movement
2) Single-lens Eye (Spiders / mollusks)
• Consists of multiple ommatidia (facets)
1) Compound Eye (insects / crustaceans)
Campbell et al. – Figure 50.17
Chapter 50: Sensory / Motor MechanismsCampbell e t al. – Figure 50.16
A) Light Detection Eyes:
Planaria – Ocellus
Photoreceptors and Vision:
Vertebrates:
A) Single-lens Eye:
Cornea: Transparent; allows
light into eye
Campbell et al. – Figure 50.18
Pupil: Regulates amount of
light entering eye
Retina: Inner surface of eye;
contains photoreceptors• Fish = move lens forward / back
• Mammals = change shape of lens
Lens: Focuses image onto
back of eye
Rods (125 million) = light sensitive
Cones (6 million) = color sensitive
Color vision common in lower
vertebrates but rare in mammals…
WHY?
Chapter 50: Sensory / Motor MechanismsCampbell et al. – Figure 50.20
Physiology of Vision (example = rods):
A) Rhodopsin (light absorbing structure) triggers signal-transduction pathway:
Opsin = membrane protein
Retinal = light-absorbing pigment
• When rhodopsin absorbs light, the retinal changes shape and separates from opsin
“Bleaching”
Separation of retinal
Why does it take
several minutes for
eyes to adjust to dark?
Chapter 50: Sensory / Motor Mechanisms
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Physiology of Vision (example = rods):
A) Rhodopsin (light absorbing pigment) triggers signal-transduction pathway:
• Altered opsin (minus retinal) triggers enzymatic pathway (similar to Figure 50.21):
IMPORTANT FACT:
Light does not depolarize rod cell,
but hyperpolarizes it
Campbell et al. – Figure 50.22
Chapter 50: Sensory / Motor Mechanisms
Physiology of Vision (example = rods):
B) Retina assists cerebral cortex in processing visual information
Vertical Pathway:
Rod Bipolar Cell Ganglion Cell
Lateral Pathway:
Horizontal / Amacrine cells link
neighboring cells
Lateral Inhibition:
Horizontal cells inhibit nearby rods from firing
(sharpens edges / enhances contrast)Campbell et al. – Figure 50.23
Chapter 50: Sensory / Motor Mechanisms
Skeletal System:
• Supporting framework for the body
Types of Animal Skeletons:
1) Hydrostatic Skeleton
• Fluid-filled compartments provide
support (via pressure)
Campbell et al. – Figure 50.33
• Movement = contraction of:
1) Circular muscles
2) Longitudinal muscles
Peristalsis
• Ideal for aquatic life
• Limited vertical support
Who:
Cnidarians
Flatworms
Nematodes
Annelids
Chapter 50: Sensory / Motor Mechanisms
Skeletal System:
• Supporting framework for the body
Types of Animal Skeletons:
2) Exoskeleton (e.g., insects, crustaceans)
3) Endoskeleton (e.g., mammals)
• Rigid, encasement deposited on surface of organism
• Chitin (modified polysaccharide) / Calcium carbonate
• Muscles attach from outer “shell” to interior of body
• Must be periodically shed
• Rigid, internal skeleton supporting body (e.g., plates / bones)
• Benefits: Can grow with organism; relatively lightweight
Chitin
Chapter 50: Sensory / Motor Mechanisms
Human Skeleton = 206 bones
• Axial skeleton
• Skull, vertebral column, rib cage
• Appendicular Skeleton
• Upper / Lower limbs
Tissue Types:
1) Cartilage (flexible support / connections)
2) Bone (rigid support - matrix)
Bones connected at joints:
1) Hinge joint:
• 2 - dimensional movement (e.g., elbow)
2) Ball-and-socket joint:
• 3 - dimensional movement (e.g., hip)
Chapter 50: Sensory / Motor Mechanisms
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Function of Muscle:
4) Guard entrance / exit (e.g., lips / anus)
5) Maintain body temperature (endotherms)
• Locomotion / manipulation (skeletal)
1) Produce movement
2) Maintain posture
3) Support soft tissue (e.g., abdominal wall)
• Blood pressure
(cardiac)
• Propulsion (smooth)
Prune Belly
Syndrome
Campbell et al. – Figure 50.37
Chapter 50: Sensory / Motor Mechanisms
Gross Anatomy of Muscle: Connective Tissue Layers:
• Outside muscle covering
• Form tendons
Epimysium:
• Divides muscle into fascicles
Compartments
• Contains blood vessels/nerves
Perimysium:
• Surrounds individual muscle
fibers & ties them together
Endomysium:
Chapter 50: Sensory / Motor Mechanisms
Microanatomy of Muscle:
Transverse Tubules: Network of passageways through fiber
• Continuous with outside of cell
Sacroplasmic Reticulum: Specialized endoplasmic reticulum
• Contain calcium ions (Ca++)
Myofibrils: Cylindrical structures containing contractile fibers
Muscle Fiber (cell):
Functional Unit of Muscle
Triad
Chapter 50: Sensory / Motor Mechanisms
Multi-nucleated
Sarcolemma: Cell membrane
Sarcoplasma: Cytoplasm
Microanatomy of Muscle:
Myofibrils contain myofilaments (protein) :
1) Actin (Thin filament)
2) Myosin (Thick filament)
Sarcomere: Repeating units of
myofilaments (~ 10,000 / cell)
MyosinActin
Sarcomere
Z lineM lineI Band
A Band
Chapter 50: Sensory / Motor Mechanisms
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Chapter 50: Sensory / Motor Mechanisms
Interactions between the thick and thin filaments of sarcomeres are
responsible for muscle contraction
Microanatomy of Muscle:
Sliding Filament
Theory
Thick filaments:
• Composed of many myosin molecules
Tails: Attach molecules together
Heads: Bind with thin filament
Hinge
Chapter 50: Sensory / Motor Mechanisms
Interactions between the thick and thin filaments of sarcomeres are
responsible for muscle contraction
Microanatomy of Muscle:
Sliding Filament
Theory
Thick filaments:
• Composed of many myosin molecules
Tails: Attach molecules together
Heads: Bind with thin filament
Thin filaments:
• Composed of interwoven actin molecules
Tropomyosin: Cover active sites
Troponin: Bind tropomyosin to actin
Chapter 50: Sensory / Motor Mechanisms
Interactions between the thick and thin filaments of sarcomeres are
responsible for muscle contraction
Microanatomy of Muscle:
Sliding Filament
Theory
Chapter 50: Sensory / Motor Mechanisms
Sarcoplasmic Reticulum
Ca++
Ca++ Ca++
Ca++
Ca++ Ca++ Ca++Ca++
Ca++Ca++Ca++Ca++
Neuromuscular Junction:
• Neuron Muscle fiber
• 1 connection / muscle fiber
Sarcolemma
Sarcoplasm
T-tubule
Synaptic
Knob
Neuron
Motor End Plate
Muscle Contraction Events:
1) Acetylcholine (ACh - neurotransmitter)
released from synaptic knob
ACh ACh ACh
2) ACh binds to receptors on motor end
plate; generates AP
3) Action potential (AP - electrical impulse)
conducted along sarcolemma
Sarcomere of
myofibril
Chapter 50: Sensory / Motor Mechanisms
Sarcoplasmic Reticulum
Ca++
Ca++ Ca++
Ca++
Ca++ Ca++ Ca++Ca++
Ca++Ca++Ca++Ca++
Neuromuscular Junction:
• Neuron Muscle fiber
• 1 connection / muscle fiber
Sarcolemma
Sarcoplasm
T-tubule
Synaptic
Knob
Neuron
Motor End Plate
ACh ACh ACh
4) AP descends into muscle fiber via
T-tubules
Ca++ Ca++Ca++Ca++Ca++
5) AP triggers release of Ca++ from
sarcoplasmic reticulum
6) Ca++ initiates cross-bridging (actin / myosin)Sarcomere of
myofibril
Muscle Contraction Events:
Chapter 50: Sensory / Motor Mechanisms
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Cross-bridging Events:
1) Ca++ binds with troponin; exposes
active sites on actin
Cross-Bridging in Action:
Chapter 50: Sensory / Motor Mechanisms
Troponin
Actin
Tropomyosin
Myosin
Head
Ca++
Cross-bridging Events:
1) Ca++ binds with troponin; exposes
active sites on actin
2) Myosin head (cocked) binds with
active site
3) Myosin head pivots – pulls actin
forward
Cross-Bridging in Action:
Chapter 50: Sensory / Motor Mechanisms
Cross-bridging Events:
1) Ca++ binds with troponin; exposes
active sites on actin
2) Myosin head (cocked) binds with
active site
3) Myosin head pivots – pulls actin
forward
4) ATP binds to myosin head; head
detaches and re-cocks
Cross-Bridging in Action:
Chapter 50: Sensory / Motor Mechanisms
ATP
ATPATP
ADP
P
Re-cock
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Cross-bridging Events:
1) Ca++ binds with troponin; exposes
active sites on actin
2) Myosin head (cocked) binds with
active site
3) Myosin head pivots – pulls actin
forward
4) ATP binds to myosin head; head
detaches and re-cocks
5) Myosin head binds to active site;
Process repeated
Cross-Bridging in Action:
• Energy = Creatine phosphate
Chapter 50: Sensory / Motor Mechanisms
ATP
ATP
ADP
P
Re-cock
ATP
ADP
P
Re-cockATP
Cross-bridging Events:
1) Ca++ binds with troponin; exposes
active sites on actin
2) Myosin head (cocked) binds with
active site
3) Myosin head pivots – pulls actin
forward
4) ATP binds to myosin head; head
detaches and re-cocks
5) Myosin head binds to active site;
Process repeated
6) Process ends when APs cease
• Ca++ returned to sarcoplasmic
reticulum (active transport)
• ACh broken down by
acetylcholinesterase (AChE)
Cross-Bridging in Action:
• Energy = Creatine phosphate
Chapter 50: Sensory / Motor Mechanisms
• Rigor Mortis • Tetanus
Campbell et al. – Figure 50.29
• Lou Gerig’s Disease (ALS) • Botulism
Chapter 50: Sensory / Motor Mechanisms
What Regulates Muscle Tension Production?
Muscle Tension: Force exerted on an object by a contacting muscle
Muscle Mechanics:
1) Number of muscle fibers activated:
Motor Unit: A single motor neuron and all the muscle fibers innervated by it
All-or-none
response
Recruitment:
Addition of motor units to produce
smooth, steady muscle tension(small large motor units)
Motor unit size dictates control:
• Fine Control = 1-5 fibers / MU (e.g., eye)
• Gross Control = 1000’s fibers / MU (e.g., leg)
Diverse body movements
require variation in muscle activity
Chapter 50: Sensory / Motor Mechanisms
What Regulates Muscle Tension Production?
Muscle Tension: Force exerted on an object by a contacting muscle
Muscle Mechanics:
2) Frequency of stimulation:
Twitch = Single stimulus-contraction-relaxation sequence
Tensio
n
Time
Stim
ulu
s
Latent Period:
Time between stimulus
and tension development
LP
Ca++ release;
cross-bridge formation
Ca++ uptake;
cross-bridge detachment
CP
Contraction Phase:
Period where tension
rises to peak level
RP
Relaxation Phase:
Period where tension
falls to resting level
Twitches alone are not a
useful contraction
Chapter 50: Sensory / Motor Mechanisms
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What Regulates Muscle Tension Production?
Muscle Tension: Force exerted on an object by a contacting muscle
Muscle Mechanics:
Incomplete Tetanus: Rapid cycles of contraction & relaxationTensio
n
Time
Stim
ulu
sMaximum
Tension
Summation:
Addition of twitches to
produce a more powerful
contraction
2) Frequency of stimulation:
Chapter 50: Sensory / Motor Mechanisms
What Regulates Muscle Tension Production?
Muscle Tension: Force exerted on an object by a contacting muscle
Muscle Mechanics:
Tensio
n
Time
Complete Tetanus: Rapid stimulation erases relaxation phase
Stim
ulu
s
Maximum
Tension
SR can not reclaim Ca++
(stimulation too rapid)
Most normal muscle contraction
involves complete tetanus
2) Frequency of stimulation:
Chapter 50: Sensory / Motor Mechanisms
Too contracted = no room for movement; poor
cross-bridge formation
Too stretched = no cross-bridge
formation
Resting length = # of cross-bridges;
distance to slide
(maximal muscle force is
near / at normal resting length)
Degree of Muscle Stretch can also Affect Muscle Performance:
Chapter 50: Sensory / Motor Mechanisms
Cardiac Muscle:Skeletal Muscle: Smooth Muscle:Property
Filament
Organization
Control
Mechanism
Calcium
Source
Contraction
Energy Source
Sarcomeres along
myofibrils
Sarcomeres along
myofibrilsScattered in
sarcoplasm
NeuralAutomaticity
(pacemaker cells)
Automaticity,
neural, hormonal
Sarcoplasmic
reticulum
SR / across
sarcolemma
Across
sarcolemma
Rapid onset;
tetanus can occur;
rapid fatigue
Slower onset;
no tetanus;
fatigue-resistant
Slow onset;
tetanus can occur;
fatigue-resistant
Aerobic / Anaerobic
metabolismAerobic
metabolism
Aerobic
metabolism