The Muscular System

By: Lydia AlpizarEmily BlazakStephanie ChecchioChris Kinney

Muscular System Overview

There are over 630 muscles in the human body.

They account for about 40% of body weight.

Muscles can’t push, they pull. Skeletal muscles with bones to form the

musculoskeletal system. Muscle is attached to end of bone by

tendon, stretches across a joint, and attached to another bone.

Functions of Muscles

Motion- fine and gross muscles movement, involuntary muscle movement

Maintenance of Posture- keeping the body in an upright position

Heat Production- the metabolism that occurs is essential for maintenance of body temperature

Characteristics of Muscles

Excitability - responds to stimuli Contractility - able to shorten in

length Extensibility - stretches when

pulled Elasticity - tends to return to

original shape & length after contraction or extension

Types of Muscles: Skeletal

Skeletal Voluntary, only

move in response to central nervous system

Striated Attached to bones

by tendons Controlled by

Somatic Nervous System

Human skeleton muscle

Functions of Skeletal Muscles

Most abundant tissue in the body

Controls fine and gross motor skills

Ex. Walking, writing, swimming, cutting with scissors

Types of Muscles Flexor - decreases the angle at a joint

Extensor - increases the angle at a joint Abductor - moves a bone away from the midline Adductor - moves a bone closer to the midline Levator - produces an upward movement Depressor - produces a downward movement Supinator - turns the palm upward or anteriorly Pronator - turns the palm downward Sphincter - decreases the size of an opening Tensor - makes a body part more rigid Rotator - moves a bone around its longitudinal axis

Types of Muscles: Visceral

Visceral Involuntary Smooth (not

striated) Controlled by

Autonomic Nervous System

Smooth muscle, uterus

Functions of Visceral Muscles

Located in walls of hollow organs to move particles

Muscles contract and relax to push particles along

Ex. Small blood vessels, digestive tract, urinary system, and reproductive system.

Types of Muscles: Cardiac

Cross between striated an involuntary muscle

Moves in spiraled motion to pump more blood through

Controlled by autonomic nervous system

Cardiac Muscles

Functions of Cardiac Muscles

Plays the most important role in contraction of the atria and ventricles of heart

Causes rhythmical beating of the heart which circulates the blood

Types of Muscle Cells

Cardiac: striated bands, contain one nucleus

Skeletal: striated bands, multiple nuclei

Smooth: thin elongated cells, also contain one nucleus

How A Muscle Contracts1. Nervous system sends signal from the brain

to muscle nerves in order to begin the contraction.

2. During muscle use, calcium channels open up and attaches to troponin protein, which is found between the actin filaments

3. Myosin protein moves along the actin to create “friction” and the overall contraction of the muscle.

4. ATP attaches to myosin head, breaking the bond between myosin and actin, ending the contraction.

5. Once there is no more calcium present, troponin acts as a barrier between myosin and actin to prevent any further contractions.

How A Muscle Contracts

Important components of a muscle contraction:

•Actin – muscle protein

•Myosin – another muscle protein

•Troponin – another muscle protein

•Calcium – important ion

•ATP – energy molecule

How A Muscle Contracts

Muscle Animation

All-or-Nothing Principle

There is a certain activation energy that acts as a catalyst for muscle movement. If the energy is below a certain threshold nothing will happen; if it’s above that threshold and the stimulus will activate. Regardless of how much the energy exceeds the specific threshold, nothing more will happen and the strength of the movement will be no greater or no less.

Tetany

Occurs when there is a depleted level of calcium and other high energy phosphates, mostly ATP

Best described as involuntary muscle convulsions

Example, hyperventilating, over-breathing

Fatigue

Occurs when the body cannot exert a normal amount of force or requires extra effort to reach a certain force

Causes can range from fatigue to severe disease

Physical disease is product of extreme physical activity

If untreated this disease can cause heart issue and paralysis

Muscular Dystrophy A group of disorders that involve muscle weakness and

a loss of muscle tissues that worsens over time. MD is genetic. The genes cannot make the proteins that

are necessary for muscles to properly function Symptoms:

muscle weakness that slowly gets worse delayed development of muscle motor skills difficulty using one or more muscle groups eyelid drooping difficulty walking

Physical exam and medical history will help doctors diagnose type of muscular dystrophy. Breathing exercises, physical therapy, and medications like steroids help people with MD. There is currently no cure.

Periodic Paralysis

A group of rare genetic diseases that lead to weakness or paralysis.

Caused by irregular level of potassium in the blood Symptoms:

Muscles respond irregularly to stimulation Weakness in limbs

Diagnosed by doctor by symptoms and blood test that checks the potassium levels in the blood

Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease) Disease effecting motor neurons in the brain and spinal

cord that control voluntary muscle movement. These neurons in the brain and spinal cord shrink and disappear causing muscles to no longer receive signals from the brain.

10% of cases are genetic, 90% are sporadic. Symptoms:

Weakness Cramps Muscles twitches Dropping things Having difficulty speaking

Doctors diagnose ALS by tests such as electromyogram, MRIs, spinal tap, or muscle and nerve biopsies.

ALS inevitably leads to loss of control in voluntary muscles. The survival rate is 3 to 5 years on average.