Human Structure And Function Week 1

Front 1

What is Bone? (General concepts)

Back 1

1. Over 206 bones in body
2. specialized form of connective tissue
3. Living tissue which is continually shaped and remodeled by the forces it is subject to

Front 2

Bone function (general)

Back 2

1. Provides a rigid skeletal framework to support and protect other body tissues
2. Forms a system of rigid levers that are moved by attached muscles.

Front 3

Types of Bones (Name the 4 types)

Back 3

1. Short Bones
2. Flat bones
3. Long bones
4. Irrecular bones

Front 4

Short Bones

Back 4

Approximately cubical. Limited gliding motions, shock absorbers.
Ex. Talus

Front 5

Flat Bones

Back 5

Protect underlying organs and tissues. Provide areas of attachment for muscles and ligaments
Ex. Sternum

Front 6

Long Bones

Back 6

Framework of the appendicular skeleton
Ex. Humerus

Front 7

Irregular Bone

Back 7

Different shapes, special functions
Ex. Vertebra, coccyx

Front 8

Material Constituents of Bone:
Inorganic components

Back 8

calcium carbonate and calcium phosphate make up 60-70% of weight and give bone its stiffness

Front 9

Material Constituents of Bone:
Organic components

Back 9

cells, collagen, a protein that lends flexible strength, and ground substance which contains water.

proper combination of organic and inorganic components make bone strong without being brittle

Front 10

What factors may affect bone?

Back 10

Diet, vitamin D from sun, activity level, age, pathology

Front 11

Classification of Bone Tissue:
Cortical bone

Back 11

Other names???
- Low porosity
- 5-30% of bone volume occupied by non-mineralized tissue
- more dense = stiffer

Front 12

Classification of Bone Tissue:
Cancellous bone

Back 12

Other names: trabecular or spongy bone
- high porosity
- 30-90% of bone volume occupied by non-mineralized tissue
- honeycomb structure

Front 13

Long Bone Structure:
Diaphysis and Epiphysis

Back 13

Diaphysis: long shaft of long bone, cylindrical in shape

Epiphysis: Ends of long bones where longitudinal growl occurs

Epiphyseal plates, made of hyaline cartilage, produce new cells during and shortly following adolescence(fuse=longitudinal growth terminates)

Front 14

Long Bone Structure:
Condyles, Articular Cartilage, and Medullary Cavity

Back 14

Condyles: bulbous ends
Articular Cartilage: self-lubricating; protects ends of long bones
Medullary cavity: Central hollow within diaphysis

Front 15

Long Bone Structure:
ENdosteum and Periosteum

Back 15

Endosteum: Layer that lines the inner surfaces like the medullary cavity
Periosteum: Tough fibrous layer covering the outside of the bone

Front 16

Bone Growth: Longitudinal development:

Back 16

-Occurs at epiphysis/epipyseal plate (growth plate), composed of hyaline cartilage.
-During/shortly after adolescence the plate disappears and the bone fuses, terminating longitudinal growth
- Most epiphyses close around age 18 although some may be present until age 25

Front 17

Bone Growth: Circumferential development

Back 17

-occurs throughout most of the lifespan, but most rapid before adulthood
- after teens stop growing in height their bones gontinue to grow more dense until age 30 when peak bone mass is reached, remains steady until life changes/age cause bone loss

Front 18

Bone Growth: Process leading to maintaining bone mass

Back 18

-Internal layer of periosteum contains osteoblasts, which are bone FORMING cells. It builds concentric layers of new bone on top of existing ones
- at the same time, bone is resorbed around the circumference of the medullary cavity by osteoclasts, bone ABSORBING cells.
-In healthy adult bone, clast and blast activity is balanced

Front 19

Bone Modeling/Remodeling

Back 19

Bone mineralization, remodeling and bone strength in both children and adults are a function of stresses on the skeleton.
--With REDUCED stress, osteoclasts function fine, but the osteoblasts slow in activity = decrease bone density, weight & strength (atrophy)
-- With INCREASED, the osteoblasts are stimulated giving increased osteoblast activity = increased bone density, weight & strength. (Hypertrophy)

Front 20

Link between falls and fractures

Back 20

Among individuals aged 65+, fall are a factor in over 90% of fractures of the hip, distal forearm and proximal humerus

Front 21

Repetitive vs traumatic load

Back 21

Traumatic: force strong enough to cause an injury, such as a fracture (disruption in continuity of bone)
Repetitive: repeated application of a non-traumatic load that is usually of low magnitude, sometimes causes stress fractures as a result

Front 22

Types of Fractures: (Described means other than direction)
Open vs Closed
Complete vs Incomplete
Comminuted
Impacted
Avulsion
Compression
Spiral
Epiphyseal
Depressed
Greenstick

Back 22

Stress/fatigue fx: fx resulting from repetitive loading.
Open vs. closed: open= fragment of bone protrudes through the skin.
Complete/Incomplete: complete= bone broken into at least 2 parts. Incomplete = fx does not extend across bone so it still is in 1 piece.
Comminuted: bone that breaks into >2 pieces.
Impacted: One fragment driven into another portion of a bony articulation.
Avulsion: Occurs when a tendon or ligament pulls a chip of bone away from the rest of the bone.
Compression: bone is crushed, often porous bone
Spiral" Ragged break from excessive twisting force applied
Epiphyseal: epiphysis separates from diaphysis
Depressed: broken bone portion pressed inward (ex skull)
Greenstick: bone breaks incompletely, common in children

Front 23

Common SPECIFIC fractures
1. Greenstick

Back 23

Greenstick: fracture resulting from bending in which one side of the bone is fractured and the other side remains in tact, usually in children
Coles fracture: Fracture of dustal radius with dorsal displacement
Boxer's: fracture of 5th metacarpal neck

Front 24

Types of Fractures described by direction of fracture within bone

Back 24

1. Linear: fx run parallel to long axis of bone
2. Transverse: fx at a right angle to shaft of bone
3. Oblique: fx runs on a diagonal to long axis
4. Spiral: fx runs circularly around bone

Front 25

Bone Healing (4 main steps)

Back 25

1. Hematoma forms
2. Fibrocartilaginous callus forms
3. Bony callus forms
4. Bone remodeling occurs

Front 26

Osteopenia

Back 26

-Condition of reduced bone mineral density that predisposes the individual to fractures.
-34 million people in the US have low bone mass at the hip (at risk for osteoporosis)

Front 27

Osteoporosis

Back 27

-A disorder involving decreased bone mass and strength with one or more resulting fractures
- occurs when not enough bone is formed OR too much bone is removed
-Affects 10 million people in US
- diagnosed by bone density test, less than 2.5 standard deviations below that of normal adult

Front 28

Osteoporosis Risk Factors

Back 28

-H/O of fracture in self or 1st degree relative
- smoking
-Low body weight (under 127 lbs)
-Adv. age
-Caucasian risk => risk but people from all ethnic groups suffer from OP
- dementia
-female
-estrogen or testosterone deficiency
-history of calcium and vitamin D deficiency
-excessive alcohol intake
- use of meds like steroids, cancer treatments etc

Front 29

Consequences of Osteoporosis

Back 29

-as many as 1:2 women and 1:4 men will suffer a fracture due to osteoporosis, typically vertebrae, proximal femur, distal forearm
-vertebral fx associated with back pain, height loss, kyphosis... activity limitations (bending, reaching)
-hip fx associated with high morbidity and mortality
-surgery can repair or replace hips, 40% of survivors do not return to previous functioning and 30% ine year post-surgery mortality

Front 30

What are joints? (general)

Back 30

-aka articulation
-structure that connects two components
- the name tells us the articulating structures
-design and function are related
-stability as primary function vs mobility. as joints become more mobile they are less stable
-Structure varies from person to person, but differences in soft tissue = differences in ROM

Front 31

Joint Classifications: Overview

Back 31

1. Synarthroses (immovable): Sutures, syndesmoses, gomphosess
2. Amphiarthroses (slightly movable): synchondroses, symphse
3. Diarthroses (freely movable): gliding, hinge, pivot, condyloid, saddle, ball and socket

Front 32

Synarthroses (general definition)

Back 32

Fibrous joints held together by tight short fibers. Immovable or very slight movement.

Front 33

Types of Synarthroses

Back 33

1. Suture: Irregularly grooved articulating bone sheets mate closely; tightly connected by fibers continuous with the periosteum.

2. Syndesmoses: Dense fibrous tissue binds bones, permitting extremely limited movement.

3. Gomphoses: The only example is a tooth in the alveolar pocket of the mandible or maxilla.

Front 34

Amphiarthroses (general definition)

Back 34

Cartilaginous joints attenuate applied forces and permit more motion of the adjacent bones than synarthrodial joints.

Front 35

Types of Amphiarthroses

Back 35

1. Synchondroses: “Held by cartilage”. Bones held by thin layer of hyaline cartilage.

2. Symphyses: Plates of thin hyaline cartilage separate a disc of fibrocartilage from the bones.

Front 36

Diarthroses (general definition)

Back 36

Diarthroses are joints in which the articulating bones are covered with hyaline/articular cartilage. An articular capsule surrounds the joint which is
lined with a synovial membrane which secrets synovial fluid.

Ligaments help to support the joint.

Most joints in the body are diarthrotic or
freely movable.

Front 37

Joint Capsule: Outter Layer

Back 37

FIBROUS layer
-Encloses ends of 2 bones and attaches further down the bones than the inner layer
- Receives extra support by ligament and tendons.
- Poor blood supply but good nerve supply
- Heals more slowly...feels more pain.
- Receives input on speed, direction of movement, compression vs. tension, vibration and pain

Front 38

Joint Capsule: Inner layer

Back 38

SYNOVIAL layer
- Highly vascularized (good blood supply) but poorly innervated.
- Constricts or dilates in response to heat or cold. (swells in heat; constricts in cold.)
- Synovial membrane which lines the inner layer of the capsule has a primary role in production of synovial fluid.

Front 39

Associated structures for Diarthroses

Back 39

1. Bursae: small capsules lined with syn. membranes, filled with syn. fluid. Function: cushion structures they separate.
2. Tendon Sheaths: double-layered synovial structures that surround tendons in close assoc. with bones.

Front 40

How are Diarthroses categorized?

Back 40

1. the axes of rotation present: unaxial, biaxial, multiaxial
2. The planes of movement: frontal, transverse, sagittal

Front 41

Types of Diarthroses:
Gliding: non-axial

Back 41

Articulating bone surfaces are nearly flat in this type of joint
Movement = non-axial gliding
Examples: intermetatarsal, intercarpal, intertarsal, facet joint of vertebrae

Front 42

Types of Diarthroses:
Hinge: uniaxial

Back 42

-One articulating bone is convex and
the other is concave.
-Strong collateral ligaments restrict motion to a hinge-like movement.
Examples: ulnohumeral, interphalangeal joints.

Front 43

Types of Diarthroses:
Pivot: uniaxial

Back 43

Rotation is permitted around one axis
Examples: atlantoaxial, proximal/distal radioulnar

Front 44

Types of Diarthroses:
Condyloid: biaxial

Back 44

- One articulating bone surface is convex, and the other is concave
- Flexion, extension, abduction, adduction and circumduction permitted.
- Ex. : 2-5th MP joints; radiocarpal joint

Front 45

Types of Diarthroses:
Saddle: biaxial

Back 45

-The articular bone surfaces are both shaped like the seat of a riding saddle (have convex and concave components).
- Movement = like condyloid, but with > ROM. Example: CMC of thumb

Front 46

Types of Diarthroses:
Ball and socket: tri-axial

Back 46

- Joint surfaces are reciprocally convex and concave.
- Allow flexion/extension, abduction/adduction, rotation, 3 planes.
- Example: hip and glenohumeral joint

Front 47

What is articular cartilage and what does it do?

Back 47

- Articular cartilage is a special type of dense, white connective tissue
- 1-5 mm thick; coats ends of bones articulating at diarthrodial joints.
- Purposes:
1. Spreads load to reduce stress
2. Allows movement with minimum friction and wear

Front 48

Structure of articular cartilage (3 layers)

Back 48

Outer Layer:
- collagen fibers arranged parallel to surface= smooth surface.
- Function: ↓friction; distribute forces

Middle Layer:
- Collagen fibers coiled and open.
Function:
1) Allows change in length of cartilage; helps absorb forces.
2) Facilitates flow of fluid OUT of cartilage during joint compression

Inner Layer:
Calcified layer of cartilage.
Function: Anchors cartilage to bone.

Front 49

Articular cartilage (location and function)

Back 49

-Found in intervertibral disks and menisci of knee
-purposes:
1. Spreads load to reduce stress
2. Improvement of the fit of the articulating surfaces
3. Limit slip of one bone w/ respect to another
4. Protect the periphery of the articulation
5. Lubrication
6. Shock absorption

Front 50

Articular Connective tissue: Tendons

Back 50

- Connect muscles to bones
- Composed primarily of collagen and elastin
- Non-contractile; will return to original length after being stretched (unless overstretched)
- Respond to stress: hypertrophy/atrophy

Front 51

Articular Connective tissue: Ligaments

Back 51

- Connect bones to other bones.
- Composed primarily of collagen and elastin
- Non-contractile; will return to original length after being stretched (unless overstretched)
- Respond to stress: hypertrophy/atrophy

Front 52

Joint Stability and influences

Back 52

Stability: Ability to resist dislocation and injury to surrounding structures.

Influences:
- Shape of articulating surfaces
- Joint position: close vs. loose packed
- Arrangement of ligaments, muscles, tendons
- Presence of fascia: fibrous connective tissue

Front 53

Joint Flexibility and influences

Back 53

Flexibility: Term used to describe ROM allowed in
each of the planes of motion.

Influences:
- Shape of articulating surfaces
- Presence of fatty tissue or muscle
- Extensibility of collagenous tissues and muscles crossing the joint= most common factor that influences mobility.

Front 54

Rheumatoid Vs Osteo-arthrisis

Back 54

finish this later :)

Front 55

Muscle Functions -- Mobility and Stability

Back 55

Mobility: Produce or control movement of bony lever around axis
Stability: Resist movement of joint surface by approximating joint surfaces

Front 56

Skeletal Muscles

Back 56

Skeletal muscle provides forces that assist joints to move in and out of close and loose packed positions

Front 57

Skeletal Muscles: Close packed positions

Back 57

--position in which articulating bomes have their maximum area of contact with each other. Joint stability is greatest.
--close-packed position for knee wrist and interphalangeal joints is at full extension, and for the ankle it's full dorsiflexion
--any movement away from clse-packed position takes a joint into the loose-packed positionin which area of contact and joint stability is reduced.

Front 58

Examples of close-packed positions of specific joints:

Back 58

1. humeroulnar joint in extension
2. Facet joints of spine in extension
3. knee in extension and external rotation
4. radiocarpal joint in extension
5. Interphalangeal (IP) joints in extension
6. MP in flexion

Front 59

Examples of Loose Packed Positions in specific joints

Back 59

Reduced contact
e.g. Shoulder: G-H joint: 55 degrees abduction, 30 degrees horizontal adduction, AC Joint and SC Joint: Arm resting at side

Front 60

Agonist (definition)

Back 60

Agonist: Muscle direct engaged in a contraction that is responsible for producing desired motion at a joint-prime mover

Front 61

Antagonist (definition)

Back 61

Antagonist: Muscle generates force that opposes the force generated by the agonist or has the potential to oppose the agonist. Can slow/stop mvt at end of ROM to protect joints through eccentric contractions

Front 62

Synergists (definition)

Back 62

Synergists are muscles which help the agonist to perform the desired action and may also stabilize the joint to prevent undesired motion (i.e. wrist ext with finger flexion)

Front 63

Example of Agonists/Antagonists/Synergists in Wrist Flexion

Back 63

Synergists -- finger flexors

come back to this card with more info :)

Front 64

Types of Muscle Tissue: Contractile vs non contractile

Back 64

Contractile: Visoelastic muscle tissue that has capacity to develop tension-nervous system stimulates this
Non contractile: Connective tissue with no ability to actively shorten/lengthen. Contributes but not actively, such as tendon, ligaments etc

Front 65

Properties of Muscle tissue:
Concractility
Irritability

Back 65

Contractility: Unique to muscle tissue, relates to ability to actively develop tension either with shortening/lengthening/holding a position
Irritability: Ability of muscles to respond to chemical, electrical and mechanical stimuli (action potential)

These are unique to muscle tissue!

Front 66

Muscle Structure:

- Muscle fasciculi
-Muscle Fiber/Cell

Back 66

Muscle fasciculi: bundles of muscle fibers
Muscle fiber (cell): Capable of shortening to ½ its length. Therefore longer fibers can shorten over a greater distance than shorter fibers.

Front 67

Do muscles with shorter or longer fibers move the joint through a greater ROM?

Back 67

Muscles with longer fibers move joint through a greater ROM

Front 68

Info about muscles cells
-- how to increase diameter
--arrangements?

Back 68

Called “fibers” because of their threadlike appearance. The diameter of each fiber increases with physical training. Muscle fibers also have different arrangements (parallel or pennate) which affects the length-shortening relationship.

Front 69

Muscle Fiber Structure:
Nuclei

Back 69

Nuclei are located immediately under plasma membrane, which in the muscle cells is referred to as the sarcolemma. This is the delicate membrane surrounding each muscle fiber.

Front 70

Muscle Fiber Structure:
-Sarcoplasm
-Myofibrils

Back 70

Sarcoplasm: cytoplasm of muscle cells (found outside of the nucleus)
Myofibrils: Contact basic contractile structures of muscle fiber, the sarcomere

Front 71

Sarcomere (definition)

Back 71

Portion of myofribril which is arranged in bands or zones and contains myofilaments. It is the contractile unit of the myofibril and is considered the basic structural unit of the myofibril.

Front 72

Myofilaments (definition)

Back 72

--Small structures within the sarcomere and myofibril. --Two types of myofilaments: thick and thin.
--Myosin (protein) forms the bulk of the thick filaments.
--Actin (different type of protein) forms the long backbone of the thin filament.
**Both involved in the contraction sliding filament theory

Front 73

Epimyosin, Parimyosin, Endomyosin

Back 73

Define these!!!

Front 74

Sliding Filament Theory of Muscle Contraction

Back 74

When a muscle contracts, each sarcomere shortens and becomes thicker, but the myofilaments remain the same length.
Specifically, the thick and thin filaments slide past one another, increasing their overlap during contraction and decreasing their overlap during relaxation or stretch.

Front 75

Sliding Filament Theory of Muscle Contraction
-- summary of what it looks like in shortened/lengthened state

Back 75

When shortening or lengthening the actin proteins move toward myosin proteins or away from myosin proteins, respectively.
In maximally lengthened position, there is no “crossing over” of actin and myosin and no tension can be generated.
In a maximally shortened position, maximum overlap has occurred and no new tension can be developed.

Front 76

Functional Motor Unit

Back 76

Consists of a single alpha motor neuron and all the muscle fibers that the motor neuron innervates.
Alpha Motor Neuron: cell body of neuron located in anterior horn of gray matter in spinal cord.
Axon: Long fiber extending from a cell body which transmits nerve impulses to skeletal muscle.

Front 77

Motor Unit Function

Back 77

--Many motor units must fire to cause an entire muscle to contract and units all fire at different times and repeatedly
--Size of the motor unit determined by the number of fibers it contains( larger cell bodies associated with larger, gross movements and smaller cell bodies associated with smaller movements)
--Nervous system automatically selects motor units with small cell bodies first so that less tension is generated and less energy is expended

Front 78

Motor Unit functional Application
What determines response to stimulus?

Back 78

--Magnitude of response to a stimulus by muscle is affected by the number of muscle fibers stimulated.
--Conduction velocity of impulse is determined by diameter of axon.
--Total response of muscle affected by number of motor units firing at one time and by the frequency of the motor unit firing.

Front 79

Muscle Fiber Characteristics
--how many types and what are the types?
--Do we all have same distribution of types in our muscles?

Back 79

--Three types of fibers (I, IIB, IIA) in each muscle. The proportion of fibers in each muscle varies, depending upon the muscle's function.
--Each muscle is composed of a combination of each of the 3 types of fibers but due to genetics, variation exist among individuals in the percentage of each fiber type

Front 80

Type 1 Muscle Fiber

Back 80

Type I: Slow Twitch: fatigue slowly and carry one sustained activity-think of endurance events/stability/postural muscles (soleus) recruited by body first to conserve energy.

Front 81

Type IIB Muscle Fiber

Back 81

Type IIB: Fast Twitch: Respond more rapidly to stimulus, but fatigue more quickly. Take longer time to recover after a big initial response-think fast powered mobility muscles for jumping/sprinting-hamstrings
*Some conversion from Type IIB to IIA with endurance training

Front 82

Type IIA Muscle Fiber

Back 82

Type IIA: Fast Twitch Oxidative Glycolytic: Produce fast contraction and fatigues more slowly than Type IIB, but more quickly than Type I.
*Some conversion from Type IIB to IIA with endurance training

Front 83

Recruitment of Muscle Fibers of different types
--Different thresholds for activation?

Back 83

Neurons that innervate Type I fibers often have low thresholds and are easy to activate. Type I: first fibers recruited to save energy (Slow twitch)
Type II fibers are supplied by larger neurons compared to Type I and are more difficult to activate

Front 84

Fiber arrangement: Paralell

Back 84

Arrangement of mm fibers can impact function
Parallel/Strap/Fusiform: Fibers oriented parallel to longitudinal axis of muscle
eg. sartorius, sternocleidomastoid
Enables greater shortening of entire muscle than is possible with a more oblique arrangement so larger ROM can be obtained

Front 85

Fiber arrangement: Pennate

Back 85

Oblique Arrangement-Pennate is latin for feather
Shorter fibers, lie at angle to the long axis
eg) deltoid-multipennate
eg) FPL-bipennate
Allows more fibers to be packed in an area so they can generate more force than a muscle of the same size

Front 86

Examples of Parallel arrangement

Back 86

Sartorius
Rectus abdominus
Sternocleidomastoid

Front 87

Examples of Penate arragement

Back 87

flexor pollicis longus (bipennate)
deltoid (multipennate = multiple angles)
Gastrocnemius (bipennate)

Front 88

Muscle Connective Tissue

Back 88

--Interconnected tissue which surrounds individual fibers, groups of muscle fibers, entire muscle, and tendons. Lies under the skin and acts as an insulator and attaches to muscles and tendons.
--Important in developing PASSIVE tension to muscle

Front 89

Muscle Connective Tissue structure
Endomysium
Perimysium
epimysium
sharpey's fibers
fascia

Back 89

Endomysium: surrounds individual muscle fibers
Perimysium: Surrounds fasciculi
Epimysium: Surrounds entire muscle
Sharpey's fibers: Tendon sheath
Fascia: A fibrous membrane covering, supporting, and separating muscles. Also connects skin with underlying tissue. Can be superficial or deep.

Front 90

More muscle connective tissue structure
Retinaculum

Back 90

Retinaculum: Thickenings for deep fascia that hold tendons in position when the muscles contract.
Function: Prevents overstretching of muscle fibers, contributes to force developed by muscle, allows for smooth transmission of force from muscle to bone

Front 91

What is the difference between muscle and connective tissue?

Back 91

Muscle is ACTIVE, connective tissue is passive

Front 92

What is role of connective tissue?

Back 92

Passive tension is developed in the passive noncontractile components of a muscle and forms a passive elastic component of a muscle.

Front 93

Characteristics of connective tissue
Extensibility and elasticity

Back 93

Characteristics:
Extensibility (can be stretched or increased in length), elasticity (can return to normal resting length), and the fact that they cannot contract actively

Front 94

Elastic behavior of a muscle
-- Parallel Elastic Component (PEC)
-- Series Elastic Component (SEC)

Back 94

Both allow muscle to stretch and recoil in a reasonable amount of time
PEC:
--Muscular connective tissues plus sarcolemma, nerves and blood cells. These tissues run parallel to muscle fibers . Tissues shorten or lengthen when the muscle shortens/lengthens to act in parallel.
SEC:
Tendon is main component. Tendon will be under tension when the muscle actively shortens. Tendon stores energy at contraction and uses it for protection against injury, deccelerates gently

Front 95

Types of Muscle Contractions:
Isotonic vs isometric

Back 95

Isotonic: Muscle changes length and moves a load. Can be either concentric (muscle shortens) or eccentric (muscle lengthens)
Isometric: Muscle keeps the same length during the contraction but still generates tension. Both distal and proximal attachments are fixed. Shortening occurs at sarcomere level. Ex. holding an object

Front 96

Muscle Contractions:
concentric and eccentric

Back 96

-type of isotonic contraction
-concentric (muscle shortens) most common target in rehab. Muscle shortening causes bony lever to be pulled close together towards center of the muscle. Responsible for most volitional movements. (Third class lever created)
-eccentric (muscle lengthens) Occurs when muscle tension is insufficient to control opposing force. Lengthening of muscle occurs. The direction of joint motion is opposite to the net muscle force. The muscle involved acts as a brake and controls the movement. (Second Class lever)
eg) lower object to a table

Front 97

Summary of ways we can classify muscles

Back 97

1. Shape -- fiber length
2. Location-- Multi Joint/Single Joint (will discuss more in Part 2)
3. Function-Act Concentrically, Eccentrically, Isometrically and what does it do?
4. Role During Movement -- agonist, antagonist, synergist