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Muscles II
Biology 2121
Chapters 9-10
Origins and Insertions
(1). Origin: attachment to less
or non-moveable bone
(2). Insertion: muscle inserts on
the moveable or more
moveable bone.
(3). Example
– Deltoid:
– O= scapula (spine); clavicle
I = deltoid tuberosity of
humerus
Motor Unit
• (1). Individual Muscles
– Have one or more motor units
that branches
• (2). One motor unit
– Neuron + all fibers ------ NM
junction
• (3). Firing of the motor nerve
– All fibers that branch off will fire
at same time
Muscle Contractions
• (1). Muscle Tension moves a load
• (2). Isometric vs. isotonic (next slide)
• (3). Motor Units
– Muscles do not always contract with same force
– Nerves branch out to serve different motor units
Types of Contractions
(1). Isometric
– muscle tension < load
– Load not moved
(2). Isotonic
– Shortening; muscle tension >
load
– Load is moved
Muscles Work Together and in Opposition
(1). Oppositional muscles
– Agonists vs. Antagonist
– Agonist: Biceps; Antagonist: Triceps
(2). Aiding Prime Movers
– Synergists
– Arm Abduction: supraspinatus and deltoid
(3). Immobilizing parts of a muscle
– Fixators
– Quads stabilize the knee when flexed to flex up on the toes
Fiber Types
Type I – Slow Oxidative (Red – Slow Twitch)
– Myoglobin; mitochondria; Slow contraction velocity;
resistant to fatigue; long distance running
Type II(a) – Fast Oxidative (Red- Fast Twitch)
– Opposite to type I; fatigue fast; sprinters
Type II(b) – Fast Glycolytic (White)
– Low myoglobin; glycogen; mitochondria; fatigue fast;
sprinting
Fiber Types – Effects on Contractions
Type 1 Fibers: Dark
Type 2 Fibers: Lighter
ATP Structure
How ATP is Produced
1. Creatinine Phosphate
2. Anaerobic Respiration
– No oxygen
– “Lactic Acid Fermentation”
– 1 glucose molecule = 2 ATP Net
3. Aerobic Respiration
– Oxygen available
– 1 glucose molecule = 36 ATP Net
– Mitochondria of the Cell