A&P Exam 2 Content: Joints, Muscular System, Muscular Tissue

Bony Joints

Synostosis

• immobile joints formed when the gap between two bones ossifies, and the bones become, in effect, a single bone

• Can occur in either fibrous or cartilaginous joints

• Example - mandibular bones in children

Fibrous Joints

Synarthrosis/synarthrodial

• Adjacent bones are bound by collagen fibers that emerge from one bone and penetrate into the other

• Three kinds: sutures, gomphoses, syndesmoses

Suture

A type of immobile fibrous joint in which short collagen fibers bind the bones of the skull to each other

• Can be classified as serrate, lap, or plane

  • Serate: interlocking wavy lines - coronal, sagittal, lamboid

  • Lap: overlapping beleveled edges - squamous

  • Plane: straight edges - palantine process of maxillae

Gomphosis

Attachment of a tooth to its socket

• held in place by a fibrous periodontal ligament

  • collagen fibers attach tooth to jawbone

Syndesmoses

Fibrous joint at which two bones are bound by long collagen fibers

• ex. interosseous membrane of radius and ulna allowing for supination and pronation

Cartilaginous Joints

Amphiarthrosis

• Two bones linked by cartilage

• Two types: synchondroses and symphyses

Synchondroses

Bones joined together by hyaline cartilage

• temporary joints in the epiphyseal plates of children

• first rib attachment to sternum

Symphyses

Two bones joined together by fibrocartilage

• pubic symphysis

• bodies of vertebrae

Synovial Joints

Diarthrosis

• joint in which two bones are separated by a joint cavity

• most are freely moveable

• structurally complex

Articular Cartilage

Layer of hyaline cartilage that covers the facing surfaces of the two bones

Joint Cavity

Separates articular surfaces

Synovial Fluid

Slippery lubricant in joint cavity

• rich in albumin and hyaluronic acid

• viscous texture

• nourishes articular cartilage and removes waste

• makes movement of articular joints almost friction free

Joint Capsule

Connective tissue that encloses the cavity and retains fluid

• outer fibrous capsule: continuous with periosteum of adjoining bones

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

Tendon

Strip of collagenous tissue attaching muscle to bone

Ligament

Strip of collagenous tissue attaching one bone to another

Bursa

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

• Cushions muscles, helps tendons slide more easily over joints

Tendon Sheath

Elongated cylindrical bursa wrapped around a tendon

What are four benefits to how exercise preserves synovial joints?

• Exercise warms synovial fluid

  • more easily absorbed by cartilage

• Cartilage then swells and provides a more effective cushion

• Repetitive compression of nonvascular cartilage during exercise squeezes fluid and metabolic waste out of the cartilage

• When weight removed, cartilage absorbs synovial fluid like a sponge taking in oxygen and nutrients to the chondrocytes

What are the special movements of the foot?

Dorsiflexion - elevating toes while swinging heels forward to take a step (heel strike)

Plantar flexion - extending foot so that toes point downward

Inversion - movement in which the soles are turned medially

Eversion - movement in which the soles are turned laterally

What are the special movements of the shoulder?

Protraction, retraction, elevation, depression and rotation

What are the two ligaments for support in the TMJ

Lateral ligament - prevents posterior displacement of mandible

Sphenomandibular ligament - on the medial side

Main ligament in the elbow that aids in pronation and supination?

Anular ligament

Muscles of the rotator cuff?

Surpaspinatus, infraspinatus, teres minor, subscapularis

Five main ligaments in the hip joint?

Anterior: Iliofemeral, pubofemoral

Posterior: Ischiofemoral

Transverse acetabular ligament

Round ligament

What are the purposes of the ACL, PCL, MCL, LCL in knee joint?

ACL - prevents hyperextension of knee when ACL is pulled tight

PCL - prevents femur from sliding off tibia

MCL and LCL prevent sliding side to side

What tendon in the ankle aids in plantar flexion?

Achilles tendon

Examples of synergists, prime movers, fixators, and antagonists in muscle action?

Prime mover: biceps brachii

Synergists: brachioradialis, brachialis

Fixator: rectus abdominus, obliques

Antagonist: triceps brachii

What is the carpal tunnel and what is the band of connective tissue that forms it called?

An opening in the wrist that is formed by the carpal bones and the bottom of the wrist and the transverse carpal ligament across the top of the wrist.

Where will you find the following connective tissue wrappings:

a. endomysium

b. perimysium

c. epimysium

a. Connective tissue around muscle cell

b. Connective tissue around muscle fascicle

c. Connective tissue surrounding entire muscle

What is the sarcoplasm and sarcolemma and where are they found?

Sarcolemma - plasma membrane of a muscle fiber

Sarcoplasm - cytoplasm of muscle fiber

What makes up the triad?

A t tubule with two terminal cisternae on either side

What are the three myofilaments and their functions?

Thick filaments - made up of myosin heads wrapped around each other

Thin filaments - made up of actin, troponin, and tropomyosin.

Elastic filaments - made up of titin, prevents overstretching

What is flaccid paralysis and what neurotoxins cause it?

Flaccid paralysis occurs when ACh is blocked by neurotoxins and the muscles are unable to contract. This can cause the heart to stop beating

Neurotoxins - botulism: caused by a toxin secreted by Clostridium botulinum. Inhibits the release of ACh

curare: competes with ACh for receptor sites but does not stimulate the muscle

What is spastic paralysis and what neurotoxins cause it?

Spastic paralysis occurs when the muscles are in a continual state of contraction.

Neurotoxins - tetanus: lockjaw caused by bacterium Clostridium tetani. Toxin blocks glycine release and causes overstimulation of muscles

pesticides may contain cholinesterase inhibitors, meaning ACh is not degraded

Describe the events that occur in excitation

Nerve signal travels to synaptic knob, casuing calcium to enter into the knob. ACh is released and begins binding to receptors in teh synaptic cleft, two by two. Calcium floods into the cell, increasing the voltage from -90mV to 75mV. Potassium floods out of the cell, making it -90mV again.

Describe the events that occur in excitation-contraction coupling

The action potential caused by depolarization travels down the transverse tubules, causing calcium to leave the SR and enter the cytosol. Calcium binds to troponin, causing tropomyosin to change shape and reveal the actin active sites.

Describe the events that occur in contraction

• ATPase in myosin head hydrolyzes an ATP molecule

• Activates the head, “cocking” it in an extended position

  • ADP and Pi remain attached

• Head binds to actin active site forming a myosin-actin cross-bridge

• Myosin releases ADP and Pi and flexes pulling thin filament with it - power stroke

• Upon binding more ATP, myosin releases actin and process can be repeated

  • recovery stroke recocks head

• Each head performs five power strokes per second

  • each stroke utilizes one molecule of ATP

What events occur in relaxation

• Nerve stimulation and ACh release stop

• AChE breaks down ACh and fragments are reabsorbed into knob

• Stimulation by ACh stops

• Ca+2 pumped back into SR by active transport

• Ca+2 binds to calsequestrin while in storage in SR

• Tropomyosin reblocks the active sites of actin

• Muscle fiber returns to its resting length

Why does rigor mortis happen?

Hardening of muscles and stiffening of body beginning 3-4 hours after death

• Deteriorating SR releases Ca+2

• Deteriorating sarcolemma allows Ca+2 to enter cytosol

• Ca+2 activates myosin-actin cross-bridge

• Muscle contracts, but cannot relax

Muscle relaxation requires ATP, which is no longer produced after death

What is isometric vs isotonic contraction?

Isometric

• muscle produces internal tension but external resistance causes it to stay the same length

• can be a prelude to movement when tension is absorbed by elastic component of muscle

• important in postural muscle function and antagonistic muscle joint stabilization

Isotonic

• muscle changes in length with no change in tension

• concentric contraction - muscle shortens as it maintains tension

• eccentric contraction - muscle lengthens as it maintains tension

Aerobic vs anaerobic respiration?

Anaerobic

• Enables cells to produce ATP in the absence of oxygen

• Yields little ATP and lactic acid, possibly contributing to muscle fatigue

Aerobic

• Produces far more ATP

• Does not generate lactic acid

• Requires a continual supply of oxygen

What is EPOC?

The difference between the elevated rate of oxygen consumption following exercise and the usual resting rate

Needed to:

• Aerobically replenish ATP

• Replace oxygen reserves on myoglobin

• Provide oxygen to liver that is busy disposing of lactic acid

• Provide oxygen to many cells that have elevated metabolic rates after exercise

Two types of muscle fibers?

Fast twitch, fast glycolytic, white, or type 2b fibers

• Well adapted for quick responses

• Fast ATPase and large SR that releases calcium quickly

• Utilizes glycolysis and anaerobic fermentation for energy

• Thick fibers, large motor units

Slow twitch, slow oxidative, red or type 1 fibers

• Well adapted for endurance

• Abundant mitochondria, capillaries, myoglobin

• Releases calcium slowly, slow ATPase

• Relatively thin fibers and small motor units