Download Ch 50 - MsBabbey

Sensory and Motor Mechanisms
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Being able to detect and
respond to the
environment is
important for survival.
Systems involved
include: nervous,
skeletal, and muscle
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1. Sensory reception: detection of a stimulus
by sensory cells (neurons, skin, ears, eyes,
etc)
2. Transmission: an action potential is sent to
the CNS
3. Perception: the brain processes the input
into understandable images
4. Amplification and Adaptation: signals are
increased or decreased based on importance
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1. Mechanoreceptors: sense physical changes
caused by pressure, touch, stretch, motion,
and sound. Often have hairs attached
externally.
2. Chemoreceptors: detect changes in solute
such as glucose, oxygen, carbon dioxide,
amino acids. Can be internal (blood) or
external (antennae)
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3. Electromagnetic receptors: detect light,
electricity, and magnetism. Found in eyes,
skull.
4. Thermoreceptors: detect heat and cold.
Located in the skin.
5. Pain receptors: neurons that detect
thermal, mechanical, or chemical stimuli
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Hearing: ears have tiny hairs that vibrate due
to pressure waves and send signals to the
brain
Equilibrium: These same hairs help orient
your body, telling your brain the position of
your head.
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Gustation (taste) and
olfaction (smell)
depend on
chemoreceptors in the
nose and mouth.
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Invertebrates have photoreceptors, which
detect light.
Insects have compound eyes, made up to
several thousand light detectors
Our eyes have photoreceptors called rods and
cones that send information through the
optical nerve to the brain.
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Smooth muscle: evolved first, non-striated,
involuntary, digestive system, arteries, veins
Cardiac muscle: striated, in the heart,
involuntary
Skeletal muscle: striated, multi-nucleated,
voluntary, moves your body
Muscles are connected to the 206 bones in
the body
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Muscles do work in pairs, one contracts and
one extends
◦ Tendons connect bone to muscle
◦ Ligaments connect bone to bone
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Muscle cells are called
muscle fibers, and are
divided into sections
called sarcomeres
◦ Made of bands of
protein:
thin (actin) & thick
(myosin)
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Ca2+ ATPase of SR
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Sarcoplasm
◦ muscle cell cytoplasm
◦ contains many mitochondria
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Sarcoplasmic reticulum (SR)
◦ organelle similar to ER, it
stores and releases Ca2+ as
needed
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Muscle movement is activated by the release
of the neurotransmitter acetylcholine
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Nerve signal
travels to muscles
Muscles release
Ca2+
This causes
muscles to
contract
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Some animals have exoskeletons made of
chitin (arthropods and mollusks)
Internal skeletons are called endoskeletons.
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Muscles, skeletons, and the nervous system
work together to produce movement, or
locomotion, like:
Swimming (with flagella or a whole organism)
Walking, running, hopping, crawling,
maintaining balance
Flying
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