1. Muscle Contraction and Movement
Biology 2121

2. 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

3. Levers (1). Muscular movement resemble a ‘lever- fulcrum’ system
(2). Effort: muscle contraction; Load: bone
(3). Most skeletal muscles = 3rd class lever system

4. Levers

5. 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

6. Types of Contractions (1). Isometric (2). Isotonic
muscle tension < load
Load not moved
(2). Isotonic
Shortening; muscle tension > load
Load is moved

7. 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

8. Motor Unit (1). Individual Muscles (2). One motor unit
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

9. Twitches and Responses
Measuring Muscle Contractions:
(1). Twitch (Latent, Contraction and Relaxation)
(2). Graded Responses
Change Stimulus Frequency
Change Stimulus Strength

10. Effect of Frequency and Increasing/Decreasing Stimulus Strength
(1). Stimulus Frequency
Wave summation; tetanus
(2). Strength
Threshold and recruitment; Threshold stimulus

11. 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

12. Fiber Types – Effects on Contractions
Type 1 Fibers: Dark
Type 2 Fibers: Lighter

13. Other (1). Muscle Tone (2). Muscle Fatigue
Muscles are slightly contracted due to spinal reflexes
(2). Muscle Fatigue
Why do muscles fatigue? What does it mean?
What are contractures?
What is meant when someone goes into oxygen debt?

14. Development (1). Embryonic stem cell (2). Week 7
Myoblasts
(2). Week 7
Skeletal muscles are contracting
(3). Fusion of skeletal muscle cells

15. What to Do About Chapter 10?
Any muscle you have covered in the lab you are responsible for in lecture
Area or region of the body it is located
Part of larger grouping of muscles (quads, etc.)
Given a simple description identify the muscle (or vise-versa)
Given a general function identify the muscle (vise-versa)
Know these origins and insertions for the lecture test
Masseter; Rectus Abdominus; Deltoid; Biceps Brachii; Sartorius; Gastrocnemius

16. Additional Information Concerning Chapter 9
Be sure to compare skeletal muscle to smooth muscle using table Compare based on the following criteria:
Location; shape and appearance; regulation of contractions; speed of contraction; rhythmic contraction