Muscle Contraction and Movement Biology 2121

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

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

Levers

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 (2). Isotonic 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

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

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

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

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

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?

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

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

Additional Information Concerning Chapter 9 Be sure to compare skeletal muscle to smooth muscle using table 9.3. Compare based on the following criteria: Location; shape and appearance; regulation of contractions; speed of contraction; rhythmic contraction