Muscular System
Sports Training and Physiology
Kociuba
http://kidshealth.org/PageManager.jsp?lic=1&article_set=59302&cat_id=20607
Muscular System - Objectives
List the major functions of muscles
 Describe 4 major properties of muscles
 Compare and contrast the 3 different
types of muscles
 Explain the sliding filament theory
 Define a muscle twitch and it’s 3 phases
 Define the different types of muscle
contractions

Muscular System – Objectives 2
Name and compare the types of skeletal
muscle fibers
 Discuss the causes of fatigue during
exercise
 Explain how fibers obtain energy
 Discuss causes of hypertrophy and
atrophy
 Discuss age related changes in skeletal
muscle

Functions of the Muscular System
Body Movement
 Maintenance of posture
 Respiration
 Production of body heat
 Communication
 Constriction of organs and vessels
 Heartbeat

Functional Properties of Muscles

Contractility



The ability to shorten
forcefully
Extensibility

Excitability

Ability to respond to a
stimulus

Ability of a muscle to
be stretched beyond
it’s normal resting
length
Elasticity

Ability of a muscle to
recoil to it’s original
shape after it has been
stretched
Muscle Tissue
3 kinds or types
Skeletal Muscle
•Attached to bones
Smooth Muscle
•Walls of hollow
organs
•Blood vessels
•Eyes, glands,
and skin
Cardiac Muscle
•Found only in
The heart
Connective tissue coverings of a
Muscle
Anatomy of the Skeletal Muscle

Filaments found in the
myofibrils


Actin
Myosin
Together they make
sarcomeres that make
up…
 Myofibrils: threadlike
structure that extends
from one end of the
muscle to the other

How do muscles contract?
Sliding Filament Model
Muscle Twitch: contraction and
relaxation to a stimuli that causes action
potential in one or more muscle fibers
 Lag/Latent
phase: time it takes to
stimulate the motor neuron to cause
the muscle to contract
 Contraction phase: time during which
a contraction occurs
 Relaxation phase: time in which
relaxation occurs
Types of Muscle Contractions

Isometric:


Length doesn’t
change, but tension
increases during the
contraction phase

Isotonic:

Amount of tension is
constant but length
changes

Concentric:
shortening a muscle

Eccentric:
lengthening a muscle
Muscle Tone:

Constant tension
produced over long
periods of time
How do the muscles get energy to
contract?
ATP is the immediate source of energy
used by the muscles
 ATP must be used continuously in order to
keep a muscle contracted
 3 ways body makes ATP production for the
muscles

 Creatine
phosphate
 Anaerobic glycolysis
 Aerobic respiration
ATP Production happens in the
mitochondria

Creatine Phosphate:
Energy Source is
creatine phosphate
 Creates 1 ATP
 Oxygen is NOT
required
 Duration of energy is
10 seconds


Anaerobic Glycolysis:
Energy Source is
glucose
 Creates 2 ATP
 Oxygen is NOT
required
 Duration of energy is
up to 3 minutes

ATP Production happens in the
mitochondria

Aerobic Respiration




Energy Source is
glucose, lactic acid,
fatty acids, amino
acids
Oxygen is required
Creates up to 36 ATP
Duration of energy is
hours!!!
Exercise and Fatigue

Fatigue: decreased capacity to do work
and the reduced efficiency of performance
to do work
 Psychologic
fatigue: most common type.
Individual perceives that they can not use the
muscle anymore
 Muscular fatigue: the reduced or absent
ability of muscle fibers to respond to stimuli
Hypertrophy and Atrophy

Hypertrophy


Muscle size increases
Slow and fast twitch
muscle fibers increase
depending upon what
exercises you do

Atrophy

Decrease in muscle
size
Disuse Atrophy

Denervation Atrophy

Age related changes in skeletal
muscle
Loss of muscle fibers
as early as the age of
25
 By 80 50% of muscle
mass is gone
 Fast-twitch muscle
fibers deteriorate
faster than slowtwitch

Gross Anatomy
Generalized Groupings of the
Muscles of the Body
*We will go over in depth starting next week
with anatomy Mondays and
Injury/Rehab Fridays
The Muscular System