bio20 9.4 - Stirling School


bio20 9.4 - Stirling School
Section 9.4
3 Types of Muscle Tissue
 1. Cardiac: muscles of the heart. (Involuntary Control)
 2. Smooth: muscle Stomach, esophagus, uterus, blood
vessels. (Involuntary Control)
 3. Skeletal: muscle that are under conscious (voluntary)
Cardiac Muscle
Smooth Muscle
 Tendon is the tissue that attaches skeletal muscle to the
 Tendonitis: inflammation of one of these structures.
 Torn Tendon
Basics of Muscles
 Contraction: when a muscle shortens
 Relaxation: when a muscle lengthens
Antagonistic Muscles
 Pairs of muscles that work against each other
 Best example: bicep and triceps (also quadriceps and
Antagonistic Muscles
Flexor vs. Extensor
 Flexor: Contracts to bend a joint (biceps)
 Extensor: Contracts to straighten a joint (triceps)
Skeletal Muscle
 Muscle cells are unique in their function as well as their
 Unlike nearly every other cell in the body, muscle cells
contain multiple nuclei.
 Muscles are composed of bundles called fibres that work
together to accomplish specific tasks.
 Muscle fibres are surrounded by a sheath called the
Skeletal Muscle
 A thread of contractile protein located in the muscles.
 2 kinds of myofilaments: 1) actin 2) myosin
 The 2 myofilaments overlap to appear striated
Sliding Filament Theory
Sliding Filament Theory
Sliding Filament Theory
Sliding Filament Theory
 Actin filaments slide over myosin filaments.
 Projections on the thicker myosin filaments form cross-
bridges on receptor sites of actin filaments.
 Cross bridges detach as actin filaments are drawn inward
Sliding Filament Theory
 Calcium binds to sites on actin to initiate formation of cross-
bridges with the myosin fibres.
 ATP begins to breakdown in presence of calcium ions.
 ATP is necessary for muscle contraction
Muscle Fatigue
Muscle Fatigue
 Lack of energy and build up of lactic acid will cause muscle
fatigue and soreness.
 Muscle tissue can store very little ATP.
Muscle Fatigue
 Creatine Phosphate in the muscle cells release ADP and help
to regenerate ATP supplies in the muscles.
 High creatine Phosphate levels = ATP levels can be
 If energy demand exceeds ATP supply, lactic acid builds up
leading to soreness.
Muscle Contraction
 Muscle action is broken down into a contraction and
relaxation cycle.
 If contraction occurs before relaxation has fully begun, the
overlap of myofilaments is increased
 This leads to a greater shortening of the muscle.
 Net Effect: greater force of contraction
 Constant muscle contraction.
Fast and Slow Twitch Muscle:
 Muscle fibres are broken down into 2 categories
 1.) Fast twitch: sprinters, explosive movements
 2.) Slow twitch: distance athletes
Myosin types
 The thick myosin determines the speed of muscle
 3 forms of myosin exist.
Type 1
 Slower muscle twitch.
 Abundant in distance runners
 Breakdown ATP slowly, but more efficiently
 Relies predominantly on aerobic respiration
Type II a and Type II x
 Faster twitch muscle
 Abundant in sprinters/football/basketball players
 Breakdown ATP faster, but less efficiently
 Rely predominantly on anaerobic respiration
Fast and Slow Twitch Muscle:
 All people have both types of muscle fiber, but in differing
Fast and Slow Twitch Muscle:
Motor System Injuries
 Muscles require a balanced diet and regular exercise to
remain healthy.
 Injuries are common when muscles are under-exercised, or
when over-exercised
 Common injuries: torn muscles, stretched tendons, torn
ligaments, joint sprains, and joint dislocations.
Arthroscopic Surgery
 Small incision(s) are made near the point of injury.
 A light source and camera as well as surgical instruments are
inserted through the incisions.
 Allows for the precise removal/repair of damaged tissue
 Advantage?
 Spares the healthy tissue, minimizing surgical damage, and
shortening recovery times.

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