Chapter 49—Sensory & Motor Mechanisms
Transcript of Chapter 49—Sensory & Motor Mechanisms
Chapter 49—Sensory & Motor
Mechanisms
If a tree falls in the forest and no one is there to hear it, does it
make a sound?
I. Sensory Reception
• Sensory Transduction
– energy from stimulus → receptor membrane potential
• Amplification– strengthening stimulus energy
• Transmission– conduction of impulse to CNS
• Integration– processing of information
Types of Sensory Receptors
• Based on the type of energy they detect:– Mechanoreceptors
• pressure, touch, stretch, motion, sound
– Pain Receptors• pain, discomfort
– Thermoreceptors• heat, cold
– Chemoreceptors• taste, smell
– Electromagnetic Receptors• light, electricity, magnetism
Stimuli start action potentials
(opens ion channels)
II. Photoreceptors & Vision
Where are the photo
receptor cells located?
Eyes contain 70% of
total sensory receptors
in body!
Which part focuses the
image?
How?
Photoreceptors: Rod Cells vs.
Cone Cells
If you are a nocturnal mammal, which
do you have more of?
What actually senses the light?
Where are
we?
III. Hearing & Equilibrium
Hearing
What type of receptor is involved?
Where are receptors located?
Sound waves create vibrations
that are conducted into the ear →
Vibrations make waves in cochlear
fluid →
hairs brush membrane →
release neurotransmitters →
triggers action potential →
brain hears sound
Human Endoskeleton
> 200 bones
3 types of
skeletons:
� hydrostatic
skeleton
� exoskeleton
� endoskeleton
3 functions of a
skeleton:
� support
� protection
� movement
Muscle MovementMuscles do work by contracting
� skeletal muscles come in
antagonistic pairs� flexor vs. extensor
� contracting = shortening
� moves skeletal parts
tendons
� connect bone to muscleligaments
� connect bone to bone
Structure of Skeletal Muscle
Striated due to repeating light and dark
bands in myofibril
A band (dark) = thick filaments = myosinI band (light) = thin filaments = actin
Sarcomere—functional unit of muscle
contraction
Figure 49.31, pg. 1081
Sliding Filament Model of Muscle Contraction
Thick & thin filaments slide past each other
(sarcomere shortens)
Caused by interaction between actin and
myosin (form cross-bridges)
Figure 49.32, pg. 1081
Actin & Myosin generate force for
muscle contraction
Figure 49.33, pg. 1082
Where does energy for contraction
come from? What happens when
you run out?
What is the trigger for muscle
contraction?
Skeletal muscle contracts only when
stimulated by motor neuron
Nerve signal (action potential)
stimulates muscle cell’sSarcoplasmic reticulum (SR) to
release stored Ca2+ into cytoplasm
Ca2+ triggers muscle action
At rest, troponin molecules hold
tropomyosin molecules so that
they cover the myosin-binding
sites on actin (no contraction)
Binding of Ca2+ exposes myosin
binding sites (contraction can
occur)
Figure 49.34, pg. 1083
Review of Skeletal Muscle Contraction
Figure 49.36, pg. 1084
um…study
this.Slow
muscle
fibers vs.
fast muscle
fibers?
Using…motor units
Motor unit—a single motor neuron and all
the muscle fibers it controls
Many fibers can contract as a group