Chapter 45 Sensory and Motor Mechanics

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Chapter 45Sensory and Motor Mechanics
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• Lawson Wakeman
• Inis Hsieh

http//tonydude.net/NaturalScience100/Topics/3Mind
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The Senses

• The major senses in mammals are sight, hearing,
  taste, touch, smell, and balance.
• These senses are detected by receptors,
  structures that transmit information about the
  internal or external environment of the organism.
• Sensory receptors work in 5 steps
• Reception when the cell absorbs the energy of
  the stimulius.
• Transduction when the energy of the reception
  is converted into electrochemical energy in the
  nerves.
• Amplification the stimulus energy is
  amplified because it is often to weak to be
  carried to the nervous system.
• Transmission once amplified, the stimulus is
  sent to the nervous system in the form of an
  action potential.
• Integration the action potential is processed
  as soon as it arrives in the brain, the brain
  then has the body react accordingly.

• Types of receptors
• Mechanoreceptors React to physical changes
  (sound, touch)
• Chemoreceptors React to chemical changes (taste,
  smell)
• Electromagnetic Receptors React to
  electromagnetic radiation of different
  wavelengths (light)
• Thermoreceptors React to changes in temperature
  (heat and cold)
• Pain Receptors take a guess

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Vision

• Vision is the detection of light, this is done in
  the eyes.
• There are several types of eyes, the main 3 being
  eye cups, compound, and vertebrate eye.
• Eye cups can only detect light or the absence of
  light, compound eyes are very similar to
  vertebrate eyes.
• The eye is surrounded by the sclera, a thin white
  layer that turns into the clear cornea over the
  iris. The iris (the colored part) expands and
  contracts to allow more or less light into the
  eye. The lens focuses light onto the fovea, the
  center of vision, which is located on the retina.
  The eye is filled with the vitreous humor, a gel
  like substance.
• Light is detected by either rods or cones, rods
  detect light, but do not distinguish colors
  (black and white vision) cones detect colored
  light. There are more rods than cones (125mil
  rods and 6mil cones)
• Cones detect 3 basic colors, and any combination
  of the 3, red, green and blue light.
• The eye focuses on objects by expanding or
  contracting the lens, when focusing on objects
  closes to the eye, the lens is almost spherical,
  when looking far away, the lens is flattened.
• Once the light hits the rods or cones, it then
  goes to the bipolar cells and then ganglion cells
  where the light is processed and some information
  is integrated, then the information is sent to
  the brain.
• The rods and cones have discs that contain the
  photosensitive pigments, these discs have
  proteins called opsins, inside the opsin is the
  retinal, which detects the light. When hit by
  light, the retinals structure changes, this
  change in shape is then translated into
  information that can be sent to the brain.

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The Eye
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Hearing and Balance

• The ear area of the body actually contains two
  sense related organs, the cochlea, which detects
  sound waves, and the semicircular canals, which
  detect movement and gravity.
• The ear is separated into 3 parts, the outer,
  middle and inner ear.
• The outer has the pinna, or what we see as the
  ear and the auditory canal.
• The middle has the tympanic membrane (eardrum),
  the ossicles which consists of the malleus
  (hammer) the incus (anvil) and the stapes
  (stirrup).
• The inner ear has the cochlea, the round and oval
  window, and the auditory tube.
• Sound comes into the auditory canal and hits the
  tympanic membrane, which vibrates and as a result
  moves the malleus, incus, and stapes, which send
  the vibrations through the oval window into the
  cochlea. There, the sound waves vibrate off the
  walls of the cochlea (basilar membrane), this
  causes tectorial membrane to vibrate, then hairs
  in the organ of coti, which are attached to the
  tectorial membrane sense these movements and send
  the information to the brain.
• Balance is a bit simpler. There are 3
  semicircular canals, they are filled with a fluid
  called endolymph, this fluid moves when the body
  moves, and creates almost a current depending on
  how the body moves.
• The endolymph flows though the canals and as it
  does so, it moves capulas, inside the capulas are
  small hairs, that move with the capula.
• The movement of the hairs within the capula send
  the information of their movement to the brain
  where it is interpreted, giving us our knowledge
  of balance and gravitational position (upside
  down, right side up, sideways, etc.)

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Anatomy of the Ear
http//www.mdconsult.com/das/patient/body/13040748
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Anatomy of the Semicircular Canals
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Taste and Smell

• Taste and smell are very closely related, taste
  is considered to be concentrated smells.
• Both use chemoreceptors to determine changes in
  the chemical solutions surrounding them.
• Can you guess the organs used for taste and
  smell? (you best be able to)
• Thats right, the tongue for taste, and the nose
  for smell.
• The receptor cells on the tongue are called taste
  buds, they detect any chemical changes in their
  surrounding environment.
• There are four basic flavors, sweet, salty, sour,
  bitter. The tongue can detect any one, or any
  combination of the four basic flavors.
• All taste buds can detect all flavors, however
  some are better at others at detecting certain
  flavors.
• The nose works in a similar way, it is
  hypothesized that it detects a few basic scents
  and then any combination of them.

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Touch

• There are six different types of nerves in the
  skin
• Ruffinis end Heat
• Messiners corpuscle Touch, pressure
• Nociceptors PAIN
• End-Bulb of Krause Cold
• Pacinian corpuscle Pressure deep within the skin
• Hair movement nerves Detect movement of hairs
• These nerves are extremely important because a
  the skin covers the entire body and is the first
  line of defense against foreign invaders such as
  viruses and bacteria.
• The amount of nerves varies depending on where
  the skin is on the body, for example, the palm of
  your hand and your fingers have a lot of nerves
  because they do most the feeling and touching of
  objects in your enviroment.

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Anatomy of the Skin
End-Bulb of Krause
Messiners corpuscle
Nociceptors
Ruffinis end
Pacinian corpuscle
http//porpax.bio.miami.edu/cmallery/150/neuro/c7
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Skeletal Systems

• Support, protect, and allow movements
• Hydrostatic skeleton
• Fluid filled compartment provide support by
  pressure.
• Free to transform shape
• Ex. Cnidarians like flatworms, nematodes, and
  annelids

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Types of skeletal systems

• Exoskeleton
• Hard encasement deposited on the surface of the
  organism (Chitin)
• Must periodically shed
• Ex. Insects, crustaceans
• Endoskeleton
• Hard supporting skeleton burried inside tissue
• Able to grow with the organism
• Ex. mammals

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Muscles

• Vertebrate skeletal muscles
• Attached to the bones
• Responsible for movement
• Hierarchy of smaller and smaller units
• A skeletal muscle is a bundle of long fibers
• Each fiber is a cell with many nuclei
• Each fiber is a bundle of smaller myofibrils
• Myofibrils are made of thin and thick myofilaments

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Sarcomere

• Repeating pattern of light and dark bands
  (striated appearance)
• Fundamental unit of organization of muscle
• Thin filaments actin
• Thick filaments myosin
• I band only thin filaments
• A band broad region corresponds to the length
  of thick filaments
• H zone center of the A band, only thick
  filaments
• This arrangement is key to muscle contraction

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Sliding Filament Model

• 1. Myosin head binds to ATP in the low energy
  configuration
• 2. Myosin head hydrolyzes ATP to ADP and
  inorganic phosphate and uses energy to change
  into high energy configuration
• 3. Myosin head binds to actin to form a cross
  bridge
• 4. Myosin relaxes to low energy state and cause a
  sliding movement in the thin filament
• 5. New ATP molecule forms and causes the release
  of the myosin head
• 6. Myosin head can now begin cycle again.

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Sliding filament model diagram
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Excitation Contraction Coupling

• Muscles are at rest because myosin- actin binding
  sites are blocked by tropomyosin.
• Troponin complex controls the position of
  tropomyosin on the thin filament.
• Muscle contraction requires the cross bridge
  attachment sites to be open.
• Calcium ion must bind to the troponin to change
  the interaction between tropnin and tropomyosin.
• The whole complex changes shape to expose the
  myosin binding sites on actin, allowing the
  sliding of the thick and thin filaments.

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Excitation Contraction Coupling

• Motor neurons release acetylocholine
• Binding of acetylocholine generates action
  potential
• Action potential travels down the transverse
  tubules into the muscle fibers
• Permeability of sarcoplasmic reticulum changes
  and releases calcium ions.
• Calcium ions bind to troponin allowing muscle to
  contract
• Muscle contraction stops as the sarcoplasmic
  reticulum pumps calcium back out of the cytoplasm
• Calcium concentration decreases and the
  tropomyosin troponin complex blocks binding sites
  again.

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Graded Contraction

• A twitch
• Nervous system produce graded contraction in two
  ways
• Varying the frequency of action potentials
• Using the organization of muscles into motor
  units
• 1 action potential increase in tension that
  lasts 100 milliseconds or less.
• If a 2nd action potential is triggered before the
  response to the first is over, then the tension
  will add together to produce a greater response.
• A series of many action potentials tension
  reach a summated level that depend on the rate of
  stimulation
• A fast enough stimulation blend the separate
  small twitches into one smooth muscle contraction
  called tetanus.

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Bibliography

• Chapter 45 in the book
• answers.com
• biology.about.com
• images.google.com

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