Kinesiology The anatomy of physical activity

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KinesiologyThe anatomy of physical activity
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MusclesWhat are they and how are they important?
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The human body has in the order of 600 muscles
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Muscle makes up 30 to 35 (in women) and 42 to
47 (in men) of body mass.
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Muscles A closer look
1 Smooth Muscle 2 Cardiac Muscle 3
Skeletal Muscle
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Lets look a little closer Smooth Muscle

• 1 Located in the blood vessels, respiratory
  tract, iris of the eye, gastro-intestinal (GI)
  tract
• 2 Function to alter the activity of various
  body parts to meet the needs of the body at that
  time
• 3 Contractions are slow and uniform
• 4 Fatigue resistant
• 5 Activation is involuntary
• 6 Can undergo hypertrophy

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Lets look a little closer Skeletal Muscle

• 1 changes length to move various parts of the
  skeleton
• 2 uses graded activation to change the speed
  and smoothness of the movement
• 3 is activated through signals carried to the
  muscles via nerves (voluntary control)
• 4 can experience fatigue through repeated
  activation

Skeletal Muscle
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Lets look a little closer Cardiac Muscle

• 1 Functions to provide the contractile
  activity of the heart
• 2 Contractile activity can be gradated (like
  skeletal muscle)
• 3 Activation of cardiac muscle is involuntary
  (like smooth muscle)
• 4 Very Fatigue resistant

Cardiac Muscle
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Lets return to skeletal muscle
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What you need to know at this point
1 Muscle 2 Muscle Fiber 3 Myofibril 4
Sarcomere 5 Actin-Myosin
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What about nerves?How are they involved?
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• 1 Central Nervous System
• 2 Peripheral Nervous System

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• 1 Motor
• conducts signals to activate muscle contraction
• 2 Sensory
• collects info from the various sensors located
  throughout the body and transmits the info to the
  brain

PNS Motor and Sensory Nerves
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The neuro-muscular system?Motor units
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• is a single motor neuron and all of the
  corresponding muscle fibers it innervates. When a
  motor unit is activated, all of its fibers
  contract.

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• 1 Slow Twitch Type I
• slow oxidative
• 2 Fast Twitch Type II
• fast oxidative-glycolytic (FOG) (IIa)
• fast-twitch glycolytic fibers (IIb)

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Slow Twitch MU (Type I)

• 1 Fibers
• red
• high mitocondria
• aerobic
• sustained activity
• 2 Nerve
• small diameter
• slow conduction
• sustained 10-20 Hz

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Fast Twitch MU (Type II)

• 1 Fibers
• white fibers
• few mitocondria
• anaerobic
• power
• quick fatigue
• 2 Nerve
• larger diameter
• fast conduction
• bursts 30-60 Hz

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I said I want more force!

• 1 Size Principle
• Ask more units to participate and this is
  accomplished based on size
• 2 Rate Coding
• Ask a motor unit to work harder

Elwood Henneman
Recruiting Motor Units
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What about physical activity and neuromuscular
system? Why should we be active?
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