bio exam 3

synovial joints

synovial joints

joint in which two bones are separated by a joint cavity

• freely mobile

• structurally complex

• most likely to develop painful dysfunction

anatomical components of a synovial joint

articular cartilage

joint cavity

synovial fluid

joint capsule

sometimes fibrocartilage

accessory structures-

bursa

tendon

tendon sheath

ligament

articular cartilage

layer of hyaline cartilage that covers the facing surface of two bones

joint (articular cavity)

separates articular surfaces

synovial fluid

slippery lubricant in joint cavity

• rich in albumin and hyaluronic acid

• gives it a viscous, slippery texture like egg whites

• nourishes articular cartilage and removes waste

• makes movement of synovial joints almost friction free

joint (articular) capsule

connective tissue that encloses the cavity and retains the fluid

• outer fibrous capsule: continuous with periosteum of adjoining bones

• inner, cellular, synovial membrane: composed mainly of fibroblast-like cells that secrete synovial fluid and macrophages that remove debris from joint cavity

fibrocartilage

articular disc forms a pad between articulating bones that crosses the entire joint capsule.

ex. meniscus

• these cartilages absorb shock and pressure

• guide bones across each other and improve their fit

• stabilize the joints reducing chance of dislocation

bursa

fibrous sac filled with synovial fluid, located between muscles, where tendons pass over bone or between bone/skin.

• cushions muscles helps tendons slide more easily over joints, modifies direction of tendon pull

tendon sheath

elongated cylindrical bursa wrapped around a tendon

in hand and foot

tendon

strip of collagenous tissue attaching muscle to bone

ligament

strip of collagenous tissue attaching one bone to another

Range of motion (joints) is determined by

structure of the articular surface

• elbow- olecranon of ulna fits into olecranon fossa of humerus

strength and tautness of ligaments and joint capsules

• stretching of ligaments increases ROM

• double-jointed people have long/slack ligament + increased ROM

action of muscles and tendons

• nervous system monitors joint position and muscle tone

• muscle tone- state of tension maintained in resting muscles

multiaxial joint

shoulder joint that has 3 degrees of freedom or axes of rotation

Ex. hip/shoulder

more freedom=more instability

biaxial

2 degrees of freedom

ex. ankle

monoaxial

1 degree of freedom

most stable

Ex. elbow

ball and socket joint

smooth, hemispherical head fits within cup-like socket

only multiaxial joints in body

ex. shoulder/hip

condylar (ellipsoid) joint

oval convex surface of one bone fits into a complementary-shaped depression on the other

bi-axial joint

ex. radiocarpal joint, metacarpophalangeal joint

saddle joint

both bones have an articular surface that is shaped like a saddle, one concave, other convex

biaxial joint

ex. thumb joint and sternoclavicular joint

plane (gliding) joint

flat articular surfaces, bones slide over each other

usually biaxial joints

ex. between carpal bones, articular processes of vertebrae

hinge joints

one bone fits with convex surface fits into a concave depression of another bone

monoaxial joint

ex, elbow, knee, fingers

pivot joints

a bone spins on it longitudinal axis.

monoaxial

ex. C1-C2 joint, radioulnar

functions of muscles

movements, stability, control of openings, heat production, and glycemic control

muscle movements

move from place to place; move body parts; move body contents in breathing; circulation and digestion

in communication- speech, writing, facial expressions other non verbal communications

stability

maintain posture by preventing unwanted movements

antigravity muscles; prevent us from falling over

stabilize joints by maintaining tension

control of opening and passageways

sphincters: internal muscular rings that control the movement of food, blood, and other material in the body

heat production

from constant ATP use, 85% of body heat

glycemic demands

muscles absorb and store glucose which helps regulate blood sugar concentration within normal range

muscle connective tissues

perimysium, epimysium, endomysium, fascia

epimysium

fibrous sheath surrounding entire muscle, holds muscle together.

outer surface grades into fascia; inner surface projections form perimysium

fascia

sheet of connective tissue that separates neighboring muscles or muscle groups from each other and the subcutaneous tissue. connects to bone

endomysium

thin sleeve of loose connective tissue around each fiber

allows room for capillaries and nerve fibers

provides chemical environment for muscle fiber

perimysium

thicker layer of connective tissue that wraps fasicle

carries nerve, blood vessels, and stretch receptors

connective layers superficial to deep

epimysium → perimysium → endomysium

strength of muscle/direction of pull determined by…

partly by orientation of its fasicles

fusiform

thick in the middle and tapered at the end

ex. biceps/triceps

parallel

uniform width and parallel fasicles

ex. rectus abdominis

triangular (convergent)

broad at one end and narrow at the other

ex. pec major/deltoid

pennate

feather shaped

unipennate- fascicles approach tendon from one side

bipennate- fasicicles approach tendon from both sides

multipennate- bunches of feathers converge to single point

circular muscles (sphincters)

form rings around body openings

strength/muscle shapes

pennate stronger than parallel stronger than circular

indirect attachment to bone

tendons

direct attachment to bone

little seperation between muscle and bone

muscle seems to emerge directly from bone

Ex. flat bones have lots

tendons

dense regular connective tissue

collagen fibers of epi-endo-peri mysiums continue into tendon and from there into periosteum/matrix of bone

subtypes of tendons

aponeurosis- tendon is a broad flat sheet (abdomen sheet)

retinaculum- connective tissue band that tendons from seperates muscles pass under

• is a divider so that movements of one doesnt cause inflammation of another

why we dont use origin/insertion to describe?

used to be origin= stationary insertion= moving

this often isn’t accurate because

some muscles attach not on bone but on fascia or tendon of another muscle or on collagen fibers of the dermis

how we want to describe muscle attachments?

origin= closer to heart

insertion= farther from heart

or superior/inferior or proximal/distal

intrinsic muscle

entirely contained within a region, such as the hand

ex. abdomen (moves trunk, located in trunk)

extrinsic muscle

acts on a designated region but has one attachment elsewhere

ex. muscles in forearm (moves hand or wrist, located in forearm)

action

effect produced by a muscle to produce or prevent movement

four categories-

• agonist

• synergist

• antagonist

• fixator

prime mover (agonist)

muscle that produces most of force during a particular joint action

ex. bicep during flexion of elbow

synergist

muscle that aids the prime mover

-may contribute additional force, modify direction, or stabilize nearby joint

Ex. brachialis during flexion of elbow

antagonist

opposes the prime mover

-prevents excessive movement

-sometimes relaxes to give prime mover control over an action

ex. tricep during flexion of elbow

antagonistic pairs

muscles that act on opposite sides of a joint

ex bicep/tricep

fixator

muscle that prevents movements of bone

• used when dont want bone movement

ex. common in hand/ankle

innervation of a muscle

refers to the identity of the nerve that stimulates it

spinal nerves

arise from spinal cord

• emerge through intervertebral foramina

• immediately branch into posterior and anterior rami

• innervate muscles below the neck

cranial nerves

arise from the base of brain

• emerge through skull foramina

• innervate the muscles of the head and neck

• numbered 12 w/ roman numerals and directional terms

blood supply for muscles

muscular system receives about 1.24 L of blood per min rest

during heavy exercise: total cardiac output rises and muscular system share of blood to 11.6 L/min

capillaries

branch extensively through the endomysium to reach every. muscle fiber

latin names

getting phased out

describes distinctive aspects of the structure, location, or action of a muscle

ex. tibialis anterior, sternocleidomastoid

universal characteristics of muscle

excitability

• chemical signals, stretch, and electrical changes across the plasma membrane

conductivity

• local electrical excitation sets off a wave of excitation that travels along the muscle fiber

contractility

• shortens when stimulated

• only cell type to contract (only pull, cant push)

extensibility

• capable of being stretched between contractions

elasticity

• returns to its originals rest length after being stretched

skeletal muscle characteristics

voluntary, striated muscle usually attached to bone

striations- alternating light and dark transverse bands (due to arrangement of internal contractile proteins -thick/thin)

voluntary- usually subject to conscious control

multinucleiated cells- needs lots of nuclei bc of how long they can get

connective tissue within muscle

collagen

is somewhat extensible and elastic

• stretches slightly under tension and recoils when released

• resists excessive strength and protects muscle from injury

• returns muscle to its resting length

• contributes to power output and muscle efficiency

sarcolemma

plasma membrane of a muscle fiber (cell membrane)

sarcoplasm

cytoplasm of a muscle fiber

contains:

myofibrils- long protein cords occupying most of sarcoplasm

glycogen- carbohydrate stored to provide energy (more stable than glucose)

myoglobin- red pigment, provides some oxygen needed for muscle activity

sarcoplasmic reticulum (SR)

smooth ER that forms a network around each myofibril

• acts as a calcium reservoir it releases calcium through channels to activate contraction

terminal cisternae

dilated end sacs of SR which cross the muscle fiber from one side to the other

T tubules

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

triad

t tubule and two terminal cisterns associated with it

myosin (thick filaments)

shaped like a golf club head

• two chains intertwined to form a shaft like tail

• double globular heads

heads directed outwards in a helical array around the bundle

• theres a bare zone with no heads in the middle

actin (thin filaments)

two intertwined strands of actin

• string of globular actin subunits each with an active site that can bind to head of myosin molecule

has tropomyosin and troponin molecules attached

tropomyosin

each blocking six or seven active sites on actin

troponin

small calcium-binding protein on each tropomyosin molecule.

when it binds to calcium the shape changes and it pulls tropomyosin unblocking actin

elastic filaments

titin: huge springy protein that makes elastic filament

run through core of thick filament and anchor it to z disc and m line

help stabilize and position the thick filament

prevent overstretching and provide recoil

contractile proteins

myosin and actin

do the work of contraction

regulatory proteins

tropomyosin and troponin

act like a switch that determines when fiber can/cannot contract

contraction activated by

release of calcium into sarcoplasm and its binding to troponin

troponin changes shape and moves tropomyosin off the active sites on action

dystrophin

clinically important protein

• links actin in outermost myofilaments to membrane proteins that link to endomyosin

• transfers forces to muscle contraction to connective tissue ultimately leading to tendon

A band

Darkest part where thick filaments overlap a hexagonal array of thin filaments

H band

middle of A band. thick filaments only

m line

middle of H band

I band

the way the bands reflect polarized light is who they are names

I= same way

light band

z disc

provides anchorage for thin filaments and elastic filaments

end of sarcomere

sarcomere

functional contractile unit of muscle fiber

segment from z disc to z disc

muscle cells shorten because their individual sarcomeres shorten as thick and thin filaments slide past each other

during shortening

neither thick or thin filaments change length during shortening- only amount of overlap changes

structural hierarchy of muscle

whole → parts

muscle → fascicle → muscle fiber → myofribil → sarcomere → myofilament

motor units

one nerve fiber and all the muscle fibers innervated by it

• dispersed throughout muscle

• contract in unison

• produce week contraction over wide area

• provide ability to sustain long-term contraction as motor units take turns contracting

• effective contraction usually requires contraction of several motor units at once

average motor units have 200 muscle fibers

small motor units

3-6 muscle fibers

fine degree of control

eye and hand muscles

large motor units

more strength than control

powerful contractions

100’s of muscle fibers

thigh-upper arm

synaspe

point where nerve fiber meets its target cell

neuromuscular junction

when target cell is a muscle fiber

each terminal branch of the nerve fiber within the NMJ forms separate synapse with the muscle fiber

one nerve fiber stimulates the muscle fiber at several points within the NMJ

axon terminal

swollen end of nerve fiber

• contains synaptic vesicles with ACh

synaptic cleft

gap between axon terminal and sarcolemma

schwann cell

envelopes and isolates NMJ

electrically excitable

muscle fibers and neurons are electrically excitable

• their membranes exhibits voltage changes in response to stimulation

resting membrane potential -90mV

• maintained by sodium-potassium pump

excitation

process in which nerve action potentials lead to muscle action potentials

excitation-contraction coupling

events that link the action potential on the sarcolemma to activation of the myofilaments thereby preparing them to contract

contraction

step in which the muscle fiber develops tension and may shorten

relaxation

when stimulation ends, a muscle fiber relaxes and returns to it resting length

length-tension relationship

the amount of tension generated by a muscle depends on how stretched or shortened it was before it was stimulated

• if overly shortened- a weak contraction results, as thick filaments just butt against z disc

• if overly stretched- a weak contraction occurs as minimal overlap results in minimal cross bridge formation

Optimum resting length produces greatest force when muscle contract. small overlap between myofilaments