Muscular System

 

Introduction

Learn all about the human muscular system. 

There are 3 learning objectives, each learning objective contains information and questions to help prepare you for the upcoming lesson.

 

 

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1. Define and describes the structure, location and function of the each muscle

Which of the following is NOT a function of the muscular system?

5 Functions of Muscular

There are over 600 muscles in the body, accounting for nearly half of the body weight.

  • Movement
    Consider the action of picking up a pen that has  dropped onto the floor. This seemingly simple action of retrieving the pen involves the coordinated action of several muscles pulling on bones at joints to create movement. Muscles are also involved in the movement of body fluids such as blood, lymph and urine. Consider also the beating of the heart which is continuous throughout life.
     
  • Maintaining posture
    Some fibres in a muscle resist movement and create slight tension in order to enable us to stand upright. This is essential since without body posture we would be unable to maintain normal body positions such as sitting down or standing up.
     
  • The production of heat
    As muscles create movement in the body they generate heat as a by-product which helps to maintain our normal body temperature.

  • movement
  • production of heat
  • exchange of gases
  • maintenance of posture

Match the 5 muscle functions

  • Enable
    movement
  • Coverage
    for the skeleton
  • Maintain posture and
    body shape
  • Provide
    strength
  • Help to maintain
    body temperature

A voluntary muscle will only contract if a stimulus is applied to it via?

Voluntary & Involuntary Muscles

  • Involuntary muscles is not under the control of the conscious part of the brain. It is found in the walls of hollow organs such as the stomach, intestines, bladder, uterus, blood vessels and heart.
     
  • Voluntary muscle tissue is made up of bands of elastic or contractile tissue bound together in bundles and enclosed by a connective tissue sheath which protects the muscle and helps to give it a contoured shape. Voluntary muscle works intimately with the nervous system and will, therefore, only contract if a stimulus is applied to it via a motor nerve. Each muscle fibre receives its own nerve impulse so that fine and varied motions are possible. Voluntary muscles also have their own small stored supply of glycogen which is used as fuel for energy. Voluntary muscle tissue differs from other types of muscle tissue in that the muscles tire easily and need regular exercise.

  • sensory nerve
  • mixed nerve
  • motor nerve
  • association nerve

Where would you NOT find involuntary muscle tissue?

  • bladder
  • brain
  • heart
  • stomach

The smooth muscle can be found in which part of the body?

3 Types of Muscle Tissue

1. Skeletal
Striped appearance. Have many nuclei. Held together by connective tissue. Voluntary or skeletal muscle tissue consists of muscle fibres held together by fibrous connective tissue and penetrated by numerous tiny blood vessels and nerves.

Each skeletal muscle fibre is made up of thin fibres called myofibrils which are made up of two different types of protein strands called actin and myosin.

This gives skeletal muscle its striated or striped appearance. Muscle fibre contraction results from a sliding movement within the myofibrils in which actin and myosin filaments merge.

 

2. Cardiac
Striped appearance. Branched structure. Has a single nucleus.

Has intercalated discs in between each cardiac muscle cell.

It is found only in the heart and like skeletal muscle it is striated. However, it is branched in structure and has intercalated discs in between each muscle cell.

 

3. Smooth
Shaped like spindles. Has a single nucleus.

Contracts or relaxes in response to nerve impulses, stretching or hormones.

Muscle tissue makes up about 50 per cent of your total body weight and is composed of:

  • 20 per cent protein
  • 75 per cent water
  • 5 per cent mineral salts, glycogen and fat.

  • brain
  • heart
  • stomach
  • face

Joints

What is Joint?

Joints are the point at which two or more bones articulate (meet)

The impetus for any movement is derived from the contraction of a muscle. However muscles rarely connect directly to the bones – most muscles are connected to the bones by tendons.

Tendons are comprised of strong, almost inelastic white fibrous connective tissue and vary in length and thickness. When a muscle contracts it pulls on its tendon. The tendon then pulls on the bone to which it is attached to cause the bone to move at the joint.

Ligaments join bone to bone to strengthen, support and protect joints. They hold the bones together to prevent dislocation but stretch slightly to allow movement. Ligaments are thicker at the joints that require the most strength and support (e.g. the hip) but are thinner and less abundant in joints that require a lot of movement (e.g. the shoulder).

What’s the name of fibrous connective tissue surrounding whole muscles?

Fascia

  • Holds the muscle together and segregates one muscle from another, allowing their free movement. 
  • Carries nerves, blood vessels and lymphatic vessels, and fills the space between the muscles.

  • tendon
  • catilage
  • fascia
  • glucose

Fill in the blank

Fascia is fibrous  tissue surrounding whole muscles.

2. Define the terms in relation to muscles

A pair of muscles having opposite action are known as?

Origin and Insertion

Muscle attachments are known by the terms origin and insertion. Generally, the end of the muscle closest to the center of the body is referred to as the origin, and the insertion is the furthest attachment.

Origins are often shorter and broader and attach over a larger area, while insertions are commonly longer and the fibres are more densely concentrated, attaching to a smaller bone area. The insertion is generally the most movable point and, therefore, the point at which the muscle work is done.

Antagonists
This is when two muscles or sets of muscles pull in opposite directions to each other. They don’t actually work against one another but work in a reciprocal complementary way with one relaxing to allow the other to contract.

Agonists/prime movers
This is known as the main activating muscle. It is important to note that these terms are used in relation to a specific action. The roles are, therefore, relative to one another and are interchangeable. An example is the action of the biceps and triceps of the upper arm. Biceps are the agonist in flexion of the elbow joint, and triceps are the antagonist. In relation to extending or straightening the elbow the roles are reversed.

  • Antagonists
  • Synergists
  • Fixators
  • Protagonists

The end of a muscle which normally remains stationary during movement is called the?

  • Aponeurosis
  • Flixator
  • Insertion
  • Origin

Muscle Contraction

Each skeletal muscle fibre is made up of thin fibres called myofibrils which are made up of two different types of protein strands called actin and myosin. This gives skeletal muscle its striated or striped appearance.

  • Muscle fibre contraction results from a sliding movement within the myofibrils in which actin and myosin filaments merge.
  • Skeletal muscle is moved as a result of nervous stimulus received from the brain via a motor nerve.

The term muscle tone is the state of partial contraction of a muscle to help maintain body posture.

  • Good muscle tone can be recognised by the muscles appearing firm and rounded.
  • Poor muscle tone may be recognised by the muscles appearing loose and flattened.

The fuel for muscle contraction is provided by?

Muscle Fatigue

The term muscle fatigue is defined as the loss of ability of a muscle to contract efficiently due to insufficient oxygen, exhaustion of glucose and the accumulation of lactic acid.

During exercise the circulatory and respiratory systems adjust to cope with the increased oxygen demands of the body. More blood is distributed to the working muscles and the rate and depth of breathing is increased.

When muscle tissue is warm, muscle contraction will occur faster due to the increase in circulation and acceleration of chemical reactions. Conversely when muscle tissue is cooled, the chemical reactions and circulation slow down.

  • lactic acid
  • pyruvic acid
  • glucose
  • actin and myosin

Which of the following movement is supination?

Muscle Actions

Supination: turn a limb to face upwards

Pronation: turn a limb to face downwards

Flexion: bend or flex a limb inwards

Extension: bend or extend a limb outwards

Abduction: move a limb away from the midline

Adduction: move a limb towards the midline

  • Turning a limb to face downwards
  • Turning a limb to face upwards
  • Turning towards center
  • Turning outwards away from center

Which of the following in a definition of plantarflexion?

Muscle Actions

Dorsiflexion: flexing/bending foot up (with toe up, heel down)

Plantarflexion: flexing/bending foot down towards the ground (with toe down, heel up) e.g. as in walking

Inversion: turning towards centre e.g. sole of foot

Eversion: turning outwards away from centre e.g. sole of foot

  • To point the toes down towards the ground
  • To point the toes towards the sky
  • To turn the palm up to face the ceiling
  • To turn the palm of the hand down to face the door

Video of Muscle Actions

Where would you find the depressor labii inferioris?

Face / Head Muscles

The muscles of the head and face have two main functions; they enable facial expression and mastication (chewing). The muscles of facial expression differ from muscles in most other parts of the body. Because there is no deep membranous fascia beneath the skin of the head, many of the thin, flat slips of muscle, attached to the facial skeleton, insert directly into the skin.

Temporalis: Elevates, Retracts mandible

Orbicularis oculi: closes eyelids

Procerous: Draws down the medial angle of the eyeblow

Levator labii superioris: Elevates the upper lip

Zygomaticus: draws the angle of the mouth superiorly and posteriorly (smile)

Orbicularis oris: closes the mouth. often referred to as "the kissing muscle.”

Mentalis: elevates and wrinkles skin of chin, protrudes lower lip.

Depressor labii inferioris: Depression of the lower lips

Depressor anguli oris: Depresses angle of mouth

Levator anguli oris: smile (elevates angle of mouth)

Masseter: Elevates mandible

Buccinator: compresses the cheeks against the teeth and is used in acts such as blowing

  • In the eye area
  • In the ears
  • In the mouth area
  • In the neck

Which muscle closes and protrudes lips and shapes the lips during speech?

Facial Muscles

Frontalis: Elevates eyebrows in glancing upward and expressions of surprise or fright;

Nasalis: compress the nasal cartilages

Platysma: Draws the corners of the mouth inferiorly and widens it (as in expressions of sadness and fright).

  • corrugator supercilii
  • orbicularis oculi
  • orbicularis oris
  • zygomaticus major

Which two muscles run down the neck?

  • corrugator supercilii and temporalis
  • orbicularis oris and platysma
  • platysma and sternocleidomastoid
  • sternocleidomastoid and mentalis

The action of the rhomboid muscles is to?

Upper Back Muscles

Sternocleidomastoid:

  • Unilaterally; cervical rotation to opposite side, cervical lateral flexion to same side
  • Bilaterally; cervical flexion, raises the sternum and assists in forced inhalation. 

Trapezius: rotation, retraction, elevation, and depression of scapula 

Deltoid: shoulder abduction, flexion and extension

Latissimus dorsi:  Extends arm at shoulder. Adducts arm. Rotates arm medially

Teres minor: Rotate the arm laterally and draw the humerus toward the glenoid fossa

Teres major: Extending the arm when it is in the flexed position and by rotating it medially

In·fra·spi·na·tus: Rotates the arm laterally

Splenius capitis: Extend, rotate, and laterally flex the head

Rhomboid minor: Adduct and laterally rotate the scapula

Rhomboid major: Adducts scapula. Downwardly rotates scapula

Supraspinatus:  Abducts arm 

  • adduct the scapula
  • elevate the scapula
  • adduct the humerus
  • elevate the humerus

Muscles of the Rotator Cuff

Subscapularis: Rotates arm medially

Supraspinatus: Abducts arm

Infraspinatus: Rotates arm laterally

Teres minor: Rotates arm laterally

Lower Back Muscle

The action of the quadratus lumborum muscle is to?

Hip

Quadratus Lumborum: flex the trunk laterally

Psoas Major: flex the thigh

iliacus: flexes the thigh or bends the pelvis and lumbar region forward

  • Fles the trunk vertically
  • Flex the trunk laterally
  • Extend the trunk
  • Rotate the trunk

The deepest of the abdominal muscles is the?

Abdominal Muscles

Transverse abdominis: Constrict the abdominal viscera and assist in expulsion of the contents of various abdominal organs (as in defecation, vomiting, and parturition).

Internal abdominal oblique: Flexes vertebral column. Compresses abdominal wall.

External abdominal oblique: Flexes vertebral column. Compresses abdominal wall.

Rectus abdominis: Flexes lumbar region of vertebral column. Rotates lumbar region of vertebral column.

  • external obliques
  • internal obliques
  • rectus abdominus
  • transversus abdominus

Which of the following muscles does not flex the forearm?

Arm Muscles

Coracobrachialis: Flexes arm at shoulder. Adducts arm

Biceps: Flexes forearm at elbow. Supinates forearm

Brachialis:  Flexes forearm at elbow

Brachioradialis: Flexes forearm at elbow

Flexor carpi radialis: Flexes hand at wrist. Abducts hand

Pronator teres: Pronates forearm

Flexor carpi ulnaris: Flexes hand at wrist. Adducts hand

Triceps: Extends forearm at elbow

Extensor carpi radialis longus: Extends hand at wrist. Abducts hand

Extensor carpi radialis brevis: Extends hand at wrist. Abducts hand

Extensor carpi ulnaris: Extends hand at wrist. Adducts hand 

  • biceps
  • brachialis
  • pronator teres
  • triceps

The action of the hamstring muscles is?

Upper Leg Muscles

Sartorius: Flexes thigh at hip, Rotates thigh laterally, Flexes leg at knee

Rectus femoris: Extends leg at knee. Flexes thigh at hip

Vastus lateralis: Extends leg at knee. Stabilizes knee

Vastus medialis: Extends leg at knee. Stabilizes patella

Vastus intermedius: Extends leg at knee

Gracilis: Adducts thigh. Flexes leg at knee. Rotates leg medially

Adductor longus: Adducts thigh. Flexes thigh at hip. Rotates thigh medially

Gluteus maximus: Extends thigh at hip. Rotates thigh laterally. Abducts thigh

Gluteus medius: Abducts thigh. Rotates thigh medially

Gluteus minimis: Abducts thigh. Rotates thigh medially

Adductor magnus: Adducts thigh. Rotates thigh laterally. Flexes thigh at hip

Biceps femoris: Extends thigh at hip. Flexes leg at knee. Rotates leg laterally

Semitendinosus: Extends thigh at hip. Flexes leg at knee. Rotates leg medially

Semimembranosus: Extends thigh at hip. Flexes leg at knee. Rotates leg medially 

  • adduction of the thigh and flexion of the hip
  • extension of the knee and flexion of the hip
  • flexion of the hip and knee
  • flexion of the knee and extension of the hip

Which of the following muscles is not a plantar flexor of the foot?

Lower Leg Muscles

Tibialis anterior: Dorsiflexes foot at ankle. Inverts foot

Extensor digitorum longus: Extends 2nd-5th distal interphalangeal joints

Extensor hallucis longus: Dorsiflexes foot at ankle. Extends 1st interphalangeal joint

Gastrocnemius: Plantar flexes foot at ankle

Soleus: Plantar flexes foot at ankle

Flexor digitorum longus: Plantar flexes foot at ankle. Inverts foot. Flexes 2nd-5th distal interphalangeal joints 

  • gastrocnemius
  • peroneus longus
  • soleus
  • tibialis anterior

Video of Muscles Song

3. Describe disease and disorders of the muscular system

Disease and Disorders

Fibromyalgia(Fibrositis)

Build up lactic acid in the muscle. Pain, stiffness of the muscles, tendons and joints. Most common in the back, neck, shoulders and feet.

Cramp

Acute painful contraction of a muscle. often associated with a mineral deficiency, an irritated nerve or muscle fatigue.

Atony

Lack of normal tone or tension in a muscle. the muscles are floppy and lacking their normal degree of elasticity.

Atrophy

The wasting away of muscles due to poor nutrition, lack of use or a dysfunction of the motor nerve impulses.

Disease and Disorders

Myositis

inflammation of a muscle.

Spasticity

Inhibitory nerves have been cut.

Sprain

Sudden twist or wrench of the joint’s ligaments.

Strain

Over-stretching, over-use causing an injury to a muscle or its tendon

Disease and Disorders

Stress

Excessive muscle tension and subsequent muscle pain, especially in the back and neck.

Rupture

Burst or tear in the facsia or sheath surrounding muscles.

Spasm

Increase in muscle tension due to excessive motor nerve activity resulting in a knot in the muscle.

Revision

The smooth muscle can be found in which part of the body?

  • stomach
  • heart
  • brain
  • face

What’s the name of fibrous connective tissue surrounding whole muscles?

  • tendon
  • fascia
  • glucose
  • catilage

A pair of muscles having opposite action are known as?

  • Synergists
  • Fixators
  • Protagonists
  • Antagonists

The end of a muscle which normally remains stationary during movement is called the?

  • Flixator
  • Origin
  • Aponeurosis
  • Insertion

Which two muscles run down the neck?

  • platysma and sternocleidomastoid
  • sternocleidomastoid and mentalis
  • orbicularis oris and platysma
  • corrugator supercilii and temporalis

Which muscle closes and protrudes lips and shapes the lips during speech?

  • orbicularis oculi
  • zygomaticus major
  • corrugator supercilii
  • orbicularis oris

Identify the muscle that is located superiorly and working down.

  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Teres major

The action of the quadratus lumborum muscle is to?

  • Fles the trunk vertically
  • Extend the trunk
  • Flex the trunk laterally
  • Rotate the trunk

The action of the rhomboid muscles is to?

  • elevate the scapula
  • adduct the humerus
  • elevate the humerus
  • adduct the scapula

Which of the following muscles does not flex the forearm?

  • biceps
  • triceps
  • pronator teres
  • brachialis

An injury caused by excessive stretching or working of a muscle is known as?

  • spasm
  • sprain
  • strain
  • spasticity

Which of the following is not associated with muscle cramp?

  • muscle fatigue
  • mineral deficiency
  • poor nutrition
  • irritated nerve

Which muscle closes the mouth?

  • risorius
  • orbicularis oculi
  • levator anguli oris
  • orbicularis oris

The action of the zygomaticus muscle is to?

  • draw the angle of the jaw upwards
  • draw the angle of the mouth upwards
  • raise the jaw
  • draw the angle of the mouth downwards

Where is the position of the buccinator muscle?

  • corner of the mouth
  • chin
  • sides of the nose
  • in the cheek

What is the muscle that turns the head to the opposite side?

  • occipitalis
  • sternocleidomastoid
  • frontalis
  • platysma

Where is the position of the transverus muscle?

  • abdomen
  • upper thigh
  • pelvic region
  • lower back

Which of the following muscles does not rotate the humerus?

  • teres minor
  • infraspinatus
  • supraspinatus
  • subscapularis

Which of the following muscles is NOT a striated muscle?

  • heart
  • trapezius
  • intestines
  • hamstrings

Identify the different muscles

  • Levator scapulae
  • Trapezius
  • Deltoid
  • Supraspinatus
  • Rhomboids
  • Infraspinatus
  • Teres minor
  • Teres major