BIO 2360 Lecture Exam 4

Joint Definition

point of contact between two bones, bone and teeth, or bone and cartilage

Fibrous joints

bones held together by fibrous cartilage

• Lack a synovial cavity

• Articulating bones are held very closely together by dense tissue

• Permit little or no movement

Types: Sutures, syndesmoses, gomphoses

Cartilaginous joints

bones held together by cartilage

• Lacks a synovial cavity

• Little or no movement

• Tightly connected by cartilage

Types

• Synchondroses

• Symphyses

Synovial Joints

Bones held together by ligaments

• Synovial cavity allows a joint to be freely moveable

• Ligaments hold bones together in a synovial joint

Articular capsule and synovial fluid

Synarthrosis

an immovable joint

Amphiarthrosis

a slightly moveable joint

Diathrosis

a freely moveable joint

Synchondroses

Type of cartilaginous joint

• Connective tissue is hyaline cartilage

• epiphyseal (growth) plate

Symphyses

type of cartilaginous joint

• slightly moveable joint

• ends of articulating bones are covered with hyaline cartilage, but a DISC of fibrocartilage connects the bones

• Intervertebral joints between the vertebrae

Articular Capsule

Part of a synovial joint

• a sleeve-like capsule that encloses the synovial cavity

• composed of: outer fibrous capsule and inner synovial membrane

Synovial Fluid

Part of a synovial joint

• synovial membrane secretes synovial fluid

• reduces friction by: lubricating the joint, absorbs shock, supplies oxygen and nutrients to the cartilage, removes CO2 and metabolic wastes from the cartilage

Bursae

Sac-like structures containing synovial fluid

Located between tendons, ligaments and bones

Cushion the movement of these body parts

Tendon Sheaths

Wrap around tendons

Reduce friction at joints

What are the two types of movement at synovial joints?

Gliding and angular movements

Gliding Definition

simple movement back and forth and from side-to-side

Angular Movements

Increase or decrease in the angle between articulating bones

Examples of gliding

Intercarpal joints, limited in range, no significant alteration of the angle between the bones

Examples of angular

Flexion, extension, hyperextension, abduction, adduction, circumduction

Flexion

Decrease in the angle between articulating bones

Bending the trunk forward

Extension

Increase in the angle between articulating bones

Opposite of flexion

Hyperextension

Continuation of extension beyond the normal extension

Bending the trunk backward

Abduction

Movement of a bone away from the midline

Moving the humerus laterally at the shoulder joint

Adduction

Movement of a bone toward the midline

Movement that returns body parts to normal position from abduction

Circumduction

Movement of a body part in a circle

Moving the humerus in a circle at the shoulder joint

Rotation

a bones revolves around its own longitudinal axis

Turning the head from side to side, such as when you shake your head “no”

Special movements

elevation, depression, protraction, retraction, inversion, eversion

Elevation

Upward movement of a part of the body

Ex. Closing the mouth

Opposite is depression

Depression

Downward movement of a part of the body

Ex. Opening the mouth

You can elevate/depress the mandible

Protraction

Movement of a part of the body anteriorly

Ex. thrusting the mandible outward

Opposing movement is retraction

Retraction

Movement of a protracted part of the body back to normal

Inversion

Movement of the foot medially

Opposing movement is eversion

Eversion

Movement of the sole laterally

Types of synovial joints

Planar, hinge, pivot, condyloid, saddle, ball-and-socket

Planar joints

permit back and forth and side to side movement

intercarpal joints

Hinge Joints

produce an opening and closing motion like that of a hinged door

permit ONLY flexion and extension

ex. knee and elbow

Pivot joints

surface of one bone articulates with a ring formed partly by another bones and a ligament

movement is rotation

Condyloid Joints

Projection of one bone fits into another oval-shaped depression of another bones

ex. metacarpophalyngeal joints

Flexion, extension, adduction, abduction, circumduction

Saddle Joints

Articular Surface of one bone is saddle-shaped, and the other bone fits into the ‘saddle’

Carpometacarpal joints

Flexion, extension, adduction, abduction, circumduction

Ball-and-socket joints

ball-like surface of one bone fitting into a cup-like depression of another bones

ex. shoulder and hip

Flexion, extension, adduction, abduction and circumduction

Suture

Ossified (highly calcified)

Synthesis (no movement)

Syndesmoses

Permits slight movement with more/longer connective tissue

Gomphoses

Synarthrotic, immovable, cone shaped peg fits into a socket

ex. articulation of teeth root into the mandible or maxilla

Three types of muscular tissue

Skeletal, cardiac, smooth

Skeletal muscle tissue

Striated (alternating light and dark bands)

Works voluntarily

Skeletal muscles move bones

Cardiac muscle

Found only in the walls of the heart

Striated like skeletal muscle

Action is involuntary: ex. contraction and relaxation of the heart

Smooth muscle tissue

Located in the walls of hollow internal structures: blood vessels, airways and many organs

Lacks the striations of skeletal and cardiac muscle tissue

Involuntary

Overview of functions of muscular tissue

Producing body movements: walking and running

Stabilizing body positions: posture

Moving substances within the body: heart muscle pumping blood

Generating heat: contracting muscle produces heat

Properties of muscle tissue that contribute to homeostasis

Excitability: ability to respond to stimuli by producing action potential

Contractility: ability to contract forcefully when stimulated to generate force

Extensibility: ability to stretch without being damaged

Elasticity: ability to return to an original length after contraction/extension

Fascia

Dense sheet or broad band or irregular connective tissue that surrounds muscles, can be deep or superificial

Deep: group muscles and fills in spaces between them

Superficial: seperate muscles from skin and protect against trauma

Extensions of deep fascia

Epimysium: outermost layer, covers entire muscle, separates 10-100 muscle fibers into bundles called fascicles

Perimysium: surrounds individual fascicles

Endomysium: Separates individual muscle fibers from one another (covers individual muscle fiber)

Microscopic anatomy of muscle tissue

Number of skeletal muscles fibers is set before you are born: last a lifetime

Muscle cell growth occurs by hypertrophy: an enlargement of existing muscle fibers rather than increase in number

Satellite cells: regenerate damaged muscle fibers

Anatomy of a muscle fiber

Sarcolemma: plasma membrane

Transverse (T tubules): spreads muscle action potential to all parts of the muscle

Myofibrils: threadlike structures that have a contractile function

Filaments: function in the contractile process, thick and thin

Sarcomeres: basic function unit of a myofibril

Sarcoplasmic reticulum (SR)

• Membranous sacs hat encircle each myofibril, stores Ca2+ (triggers muscle contraction)

Sarcoplasm: the cytoplasm of a muscle fiber

• Glycogen: synthesis of ATP and myoglobin (bind O2 aerobically)

Z discs

separate one sarcomere from the next

center of I band

connects myofibrils together and anchor thin filaments

A bands

Darker middle part of the sarcomere

thick and thin filaments overlap

I bands

lighter, contains thin filaments, but no thick filaments

Z discs pass through the center of each I band

H zone

center of each A band, contains thick but no thin filaments linM

M line

supporting proteins that hold the thick filaments together in the H zone (center)

Myosin

Thick filaments

Motor protein that can achieve motion

Convert ATP to energy of motion

Projections of each myosin molecule protrude outward (myosin head)

Actin

thin filaments

provide a site where a myosin head can attach

Tropomyosin and troponin (regulatory P proteins) are also part of the thin filament

Strands of tropomyosin cover the myosin-binding sites

Muscle contraction

Calcium ions bind to troponin to move tropomyosin away from myosin binding sites and allows for muscle contraction to begin ad myosin binds actin

Muscle relaxation

myosin is blocked from binding actin

Titin

accounts for the elasticity and extensibility of myofibrils

Dystrophin

helps transmit the tension generated by a sarcomere to the tendon

Myosin

forms the M line

Nebulin

maintains alignment of the thin filament in the sarcomere

The Sliding Filament Mechanism

Myosin heads attach and walk along the thin filaments at both ends of a sarcomere

Progressively pull the thin filaments toward the center of the sarcomere

Z discs come closer together and the sarcomere shortens

Leading to shortening of the entire muscle

The Contraction Cycle

The onset of contraction begins with the SR and releasing calcium ions into the muscle call

• Ca binds to troponin to move tropomyosin out of the way so myosin heads can now reach and bind to actin

Excitation-Contraction Coupling

An increase in Ca+ concentration in the muscle starts contraction

A decrease in Ca+ stops it as wll

Action Potentials cause CA++ to be released from the SR into the muscle cell

Ca+ moves tropomyosin away from the myosin binding sites on actin to allow cross bridges too rom

As the Ca+ level drops, myosin-binding sites are covered and the muscle relaxes

NMJ (Neuromuscular junction)

Motor neurons have a threadlike axon that extends from the brain or spinal cord to a group of muscle fiber

Action potentials arise at the interface of the motor neuron and muscle fiber

Sarcomere

Area between any two Z discs

Synapse

Where communication occurs between a somatic motor neuron and a muscle fiber

Neurotransmitter

Chemical released by the initial cell (neuron) communicated with the second cell (muscle fiber)

Motor Units

Control muscle tension

• consists of motor neurons and the muscle fibers they stimulate

• The axon of the motor neuron branches out to form NMJs with different muscle fibers

• A motor neuron makes contact with about 150 muscle fibers

• The total strength of a contraction depends on the size of the motor units and the number that are activated

Production of ATP is muscle fibers

• Is needed for pumping Ca into the SR and powering the contraction cycle

• powers contraction for only a few seconds

• ATP must be produced by the muscle fiber after the reserves are used up

What are the three ways ATP is produced in muscle cells?

By aerobic cellular respiration

By anaerobic cellular respiration

From creatinine phosphate

Creatinine Phosphate and ATP

Excess ATP is used to synthesize creatinine phosphate, which is an energy-rich moleule

Provide enough energy for contraction for about 15 seconds

Anaerobic Respiration

Series of ATP producing runs that do not need oxygen

Glucose is used to make ATP when creatinine phosphate supply is depleted

Can provide enough energy for about 30-60 seconds of muscle activity

Aerobic Respiration

Activity that lasts longer than half a minute depends on this type of of respiration, up to hours of activity

Oxygen comes from hemoglobin in the blood, and is release by myoglobin in the muscle call

Muscle Fatigue

Inability of muscle to maintain force of contraction after prolonged activity

• Inadequate release of Ca+ ions from the SR

• Depletion of creatinine phosphate

• Insufficient oxygen

• Depletion of glycogen and other nutrients

• Failure of motor neuron to release enough acetylcholine

Twitch contraction

The brief contraction of the muscle fibers in a motor unit in response to an actin potential

• latent contractions relaxation periods

Latent period

brief delay between the stimulus and muscular contraction

Contracton period

Ca++ binds to troponin

Cross-bridges form

Relaxation period

Ca++ is transported into the SR

Myosin binding heads are covered by tropomyosin

Myosin heads detach from actin

Wave summation

increased strength of contraction resulting from the application of a stimulus before the muscle has completely relaxed after a previous stimulus (fused or unfused)

Red muscle fibers

have high myoglobin content

Appear darker

White muscle fibers

have a low content of myoglobin

Appear lighter

What are the three types of muscle gibers?

Slow oxidative, fast oxidative, fast glycolytic

Cardiac muscle tissue

Principal tissue in the heart wall

• intercalated discs connect the ends of cardiac muscle fibers to one another

Cardiac muscle contraction

Last longer than skeletal muscle twitch due to the prolonged delivery of Ca+ from the ECF and SR

• stimulated by autorhythmic muscle fibers.

Continuous, rhythmic activity is a major physiological difference between cardiac and skeletal muscle tissue

Smooth muscle tissue

Activated involuntarily

Found in: walls of arteries and veins, hollow organs and walls of the airways and lungs

Microscopic anatomy of smooth muscle

• Thick and thin filaments that are not arranged in orderly sarcomeres

• Not striated

• Can be single or multi unit types: meaning the fibers contract as a single unit or each fiber singly

Contraction of smooth muscle

Contraction lasts longer than skeletal muscle

Initiated by Ca+ flow from interstitial fluid

Able to sustain long-term muscle tone

Orgin

the attachment of a tendon to the stationary bone

Insertion

the attachment of the muscles other tendon to the movable bone is called the insertion

Muscle fascicle

a small bundle of skeletal muscle fibers (muscle cells) surrounded by a connective tissue layer

What are the 5 fascicle types?

Parallel, fusiform, circular, triangular, pennate

Compromise of muscle fascicle

Longer fibers have a greater range of motion

Total cross-sectional area is the power of a muscle

Agonist

prime mover and is responsible for the action

Antagonist

performs an opposite function of the agonist

Synergist

prevent unwanted movements at other joints, aids agonist, stabilize intermediate joints