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