The Musculoskeletal System (chp 8)

muscles and skeleton

What are the types of Muscles?

Skeletal muscles

Smooth muscles

Cardiac muscles

What are skeletal muscles?

Muscles attached to the skeleton

Under conscious control and allows us to carry out a wide range of physical activities

Contraction Brings about movement in joints and gives bodies its form and contours

What are Smooth muscles?

muscles associated with the internal organs of the body and provide their movement (stomachs and intestines)

Under involuntary control

What are Cardiac muscles?

heart muscle

Contracts to reduce the space in chambers of the heart and push the blood from the heart into the blood vessels

What do muscles do?

they have special properties that together bring about movement at a joint

Contractibility

Extensibility

Elasticity

What is contractibility of the muscles?

all muscle has the ability to contract (shorten)

Muscles re designed so that when they contract, they reduce the distance between the parts they are connected to, or decrease the space they surround

What is extensibility?

ability to be stretched

What is elasticity?

ability to return to original length after stretching

How do the muscles work together? *3 points*

1. muscles are attached to the bone by fibrous elastic connective tissue called tendons. Attach bones in such a way it allow the bone to move when the muscles contract

2. Muscles can pull bones, but cannot move them apart. (1 directional of movement). There fore, muscles which move parts of the body work in pairs

3. Pairs of muscles where one muscle provides movement in one direction, and the other muscle in the other directed are called antagonists

What is the origin?

End of muscle fixed to stationary bone (bone doesn’t move in action)

What is insertion?

End of muscle fixed to moveable bone (moves in the action)

What is the belly?

the fleshy portion of the muscle between the tendons of origin and insertion

What is the Agonist muscle?

prime mover

Muscle that causes desired action

What is an antagonist muscle?

Muscle that has the opposite effect to the agonist

What is a synergist muscle?

muscles that help, indirectly, to steady the joint during movement (prevent unwanted movement)

What is a fixator?

When a synergist immobilises the joint

What is the structure of skeletal muscles?

Muscle cells are held together in bundles

Sheath of connective tissue surrounds each bundle so it can function as an INDIVIDUAL UNIT, and slide over one another as they contract

Towards the end f the muscle, the sheathes of connective tissue taper and form the tendon

What are muscle cells?

they are called, muscle fibres:

• muscle cells which are cylinder in shape

Each muscle cell lies parallel to the next, about 10-100 micrometres in diameter and few mm to several cm long

Contain MANY nuclei

What is the structure of the muscle fibres?

In muscle cells, the thin plasma membrane surrounding the cells is called the sacrolemma

Contains cytoplasm which in muscle cells is called sarcoplasm

Inside the sarcoplasm of each fibre are thread-like myofibrils lying parallel to each other. Can be hundreds to many thousands of myofibrils in each fibre

What is the structure of the myofibrils?

composed of many smaller myofilaments made of protein

These are very important as they allow contraction of the muscle

What are the two types of myofilaments?

Myosin: thick myofilaments

Actin: thin myofilaments

What is the structure of thin Actin myofilaments?

composed mostly of action

Contain tropomyosin and troponin

Double-stranded coil

What is the structure of thick Myosin myofilaments?

composed mostly of myosin

Rod-shaped (tail) with head

How do the myofilaments work?

when stimulated by NERVE IMPULSES, there is enough energy, the thick and thin filaments slide pass each other which SHORTENS the myofibril

What is the structure of myofibrils and what do they give?

Arrangement of thick and thin filaments in the myofibril gives balanced effect to the muscle

Myofibrils can be divided into units called sacromeres

Sacromeres contain actin and myosin in certain patters

Gives skeletal and cardiac muscle their striated appearance

What is the structure of a skeletal muscle? (Diagram)

What is the sliding filament model?

sliding filament theory explains how muscle contraction occurs

It is a simplified representation of the idea/process

The basis of the model surrounds actin and myosin filaments sliding over each other

How does the sliding filament model work?

Thin actin filaments slide over thick myosin filaments

The “z lines” (anchor points for actin) are drawn closer together and the sacromere is shortened, thus shortening the whole muscle

The myofilaments stay the same length, they overlap to shorten the muscle

When the muscle is relaxed, the actin and myosin are pulled back in the opposite direction, returning the muscle to its original state

What is the structure of the sacromere?

How does contraction work? Step 1

Sarcoplasmic reticulum releases calcium ions into sarcoplasm

How does contraction work? Step 2

Calcium ions will bind to troponin

→ causes troponin-tropomyosin complexes to move away from the myosin binding sites on actin

Once this happens, contraction can begin

How does contraction work? Step 3

Myosin heads contain ATP binding and ATPase enzymes

• ATP os hydrolysed into ADP, feeeing up a phosphate molecule

  → energises the myosin head

How does contraction work? Step 4

Myosin attached to the myosin binding sites in actin and myosin threads

→ forms the cross-bridge between the actin and myosin threads

How does contraction work? Step 5

Phosphate released by myosin triggers the actual power contraction stroke

How does contraction work? Step 6

ADP pockets opens up on the myosin head

How does contraction work? Step 7

Myosin head rotates and releases the ADP

How does contraction work? Step 8

As the head rotates,, it pulls the thin filaments closer to the centre of the M line

How does contraction work? Step 9

When the motion is over, the myosin awaits another ATP so it can be released from the actin binding site

How does contraction work? Step 10

If ATP is available, the myosin detaches and begins another stroke of the cycle

How does contraction work? Step 11

Myosin heads will keep binding with actin sites until the ATP runs out or the calcium levels decrease

What is the function of the skeletal system?

Storage: minerals, salts and fats

Production: contains stem cells which can become blood cells

Protection: of organ systems

Leverage: allow muscles to attach and produce gross movements

Support: provides shape and supports its parts

What is the function of bones and general information

Axil skeleton: at the midline, 80 bones

Appendicular skeleton: Appendages (limbs) and their girdles (pelvic and shoulder) 126 bones

Function: to support its respective organs

What is the anatomy of a long Bone

Diaphysis: shaft

Epiphysis: extremity of bones

Articulate cartilage: covers epiphysis

Periosteum: covering around surface of bone

Compact bone

Spongy bone

Why does your bone have cartilage?

It is soft and flexible to absorb shock

What is the structure of the Periosteum

Has 2 layers

→ fibrous layer

→ osteogeic layer

Which has 2 things

→ osteoblasts: produce bone

→ osteoclasts: break down bone

What is the structure of the Bone Tissue

Has pores that

→ living cells

→ channels for blood vessels

→ decrease weight of the bone

Has a degree of porosity

→ spongy (cancellous) bone

→ compact bone

What are the tissues of the skeletal system?

Bones are LIVING TISSUE

Compact bone: highly organised and composed of tubular osteons

Spongy bone: more porous and may be filled with red bone marrow

What is the structure of the compact bone?

Consists of small units known as osteons (similar in structure to myofibrils in muscles)

What is the structure of the osteon?

A central canal

Lamellae

Lucanae

Osteocytes

Canaliculi

What do each of the structures of the osteon do?

A central canal: space for blood vessels and nerves

Lamellae: circle of compact bony matrix

Lucanae: small spaces between lamellae

Osteocytes: cells that occupy the small spaces (Lucanae)

Canaliculi: small, canal-like, passages between lucanae (blood supply)

What is the structure of the spongy (cancellous) bone?

less organised than compact bone

Consists of random arrangement of trabecular (thin plates or bone)

Osteocytes take up places within trabecular, blood vessels and nerves pass through spaces

What is cartilage and where is it found and what does it do?

Found on the surface of bones, in trachea, end of nose etc

Provides flexibility and supports

Has very limited supply of nutrition and removal of wastes due to a lack of blood supply, therefore takes a long time to heal

What is the structure of cartilage?

Consists of collagen embedded in chondrin

Cartilage cells are known chondroblasts. Produce a matrix which gradually surrounds them until they are enclosed

When these chondroblasts are enclosed, they become chondrocytes (mature cartilage cells)

What are the types of Cartilage?

Hyaline

Fibrocartilage

Elastic cartilage

What is the hyaline cartilage?

generally found between joints (articular cartilage) where strength is important. Collagenous Fibres are closely packed

What is Fibrocartilage?

generally found in weight bearing regions, such as intervertebral discs

Coarse appearance (fibrous)

What is elastic cartilage?

generally found where flexible support is required

Eg; ears

Collagenous fibres are not closely packed (this makes it elastic)

What are articulations? (Joints)

where bones are joined together

they are classified by degree of movement

Immovable, slightly moveable, and freely moveable

What are fibrous joints?

immovable or fixed

Held together by connective tissue

Very strong

Examples

• sutures of skull

• Teeth and jaw

What are cartilaginous joints?

slightly moveable

Held in place by cartilage

Stronger than synovial

Examples

• pubic symphysis

• Intervertebral discs

What are Synovial Joints?

freely moveable

Ligaments, muscles and tendons control

Examples

• shoulder joint

• Knee joint

What are the 6 types of synovial joints?

1. Ball and socket

2. Hinge

3. Pivot

4. Gliding

5. Saddle

6. Condyloid

What is the ball-and-socket joint?

Spherical head of a bone fits into a cup-like depression of another bone

Allows for a very large range of motion

Examples:

• shoulder joint

• Hip joint

What is a hinge joint?

convex surface of one bone fits into concave of another

Allows movement in one plane-back and forth

Examples

• elbow joint

• Knee joint

What is the pivot joint?

pointed end of a bone articulates with a ring of bone/ligament

Allows for rotation

Examples:

• 1st and 2nd vertebrae (head rotation)

• Radius and ulna

What is the gliding joint?

two bones that move alongside one another

Allows for limited movement in either side to side or back and forth

Examples

• between carpal bones

• Sternum and clavicle

What is the saddle joint?

concave and convex bones fit together (like a saddle)

Allows for a large range of motion back and forth and side to side

Examples:

• thumb joining hand (metacarpal to carpal)

What is the Condyloid joint?

slightly convex bone fits into slightly concave bone

Allows for a limited range of motion both side to side and back to forth

Examples:

• between phalanges and metacarpals

• Radius and carpals

What is the structure of a synovial joint

What is the articular capsule?

Surrounds the entire joint

What is the fibrous capsule?

outer layer made up of dense connective tissues attached to bones

• flexible enough to allow movement, but strong enough to prevent dislocation of joint

What is the synovial membrane?

inner layer of capsule made up of loose connective tissue

• lines the entire cavity and is well supplied with blood vessels

What is synovial fluid?

It is secreted by synovial membrane and fills the synovial cavity

What are the functions of the synovial fluid?

Lubricate

Provide nourishment

Contains phagocytes (white blood cells)

How does the synovial fluid lubricate?

it lubricates joints and keeps two surfaces of bones from rubbing one another

How does the synovial fluid provide nourishment?

It has minerals for cartilage cells

How does the synovial fluid contain phagocytes and what does that do?

to destroy any pathogens or debris from wear and tear

Injury to a synovial joint will increase the synovial fluid, leading to inflammation

What is the articular cartilage?

covers the surfaces of bones to reduce friction on surfaces.

Takes a long time to heal, white bits have lots of white blood cells

What are articular discs?

Meniscus in knee

Direct the synovial fluid into areas of greatest need such as articulating surfavces

What is the bursae?

sacs of synovial fluid that prevent friction between features such as tendons/joints/skin & bones

Membrane bound sac

In places of friction

What are ligaments?

Join bone to bone to add strength to joints

What movements can the joints do?

Fexion

Extension

Abduction

Adduction

Rotation

What is Flexion?

decreases the angle between bones

• bicep curls

What is extension?

increases the angle between bones

• kicking a footbsll

What is abduction?

movement away from the midline of the body

• sidestepping

What is adduction?

Movement towards the midline of the body

• putting arms by your side

What is rotation?

movement of bone around long axis

• turning your head

What is Osteoporosis?

Loss of bone mass (density(

What are the causes/risk factors, symptoms and preventions/treatments for osteoporosis?

Causes/risk factors

• age (over 30)

• Menopause

• Lack of calcium/vitamin D

Symptoms

• increases risk of fractures

Preventions/treamtment

• increase calcium intake

• Regular excessive

• Quit smoking

What is osteoarthritis?

Deterioration of cartilage in joints

What are the causes/risk factors, symptoms and preventions/treatments for osteoarthritis?

Causes/rick factors

• age

• Menopause

Symptoms

• pains at joints

• Growth of bone spurs

• Restricted movement

Prevention/treatment

• medication (pain relief)

• Physiotherapy to strengthen muscles

• Surgery