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