Musculoskeletal System Flashcards
0
Q
cartilage
A
- firm but elastic matrix called chondrin that is secreted by cells called chondrocytes
- cartilage is relatively avascular (without blood and lymphatic vessels) and is not innervated
1
Q
skeletal system
A
- endoskeletons: humans have these; internal so don’t protect us externally but we also don’t have to shed them either
- exoskeletons: like suits of armor, protect entire organisms because they surround them completely; org growth requires shedding of the exoskeleton
- axial skeleton: skull, vertebral column and ribcage; provices basic central framework for the body
- appendicular skeleton: arms, legs, pelvic and pectoral girdles that are attached to the axial skeleton for stability
2
Q
bone - macroscopic bone structure
A
- compact bone: where bones strength comes from
- spongy or cancellous bone: looks like a sponge; has bony oints known as trabeculae
-cavities filled with marrow (red - filled with hematopoietic stem cells, which responsible for generation of all the cells in blood; or yellow: fat, inactive
bones in appendicular skeleton called long bones which are characterize by cylindrical shafts called diaphyses and dilated ends called epiphyses; the outer portions of both kinds have compact bone
- -> long bones are filled with arrow where as epiphyses have a spongy coreinside their compact bone sheath for more effective dispersion of force at the joints
- -> fibrous sheath called periosteum surrounds long bone to protect it as well as serve as a site for muscle attachment
3
Q
microscopic bone structure
A
- compact bone is strong because of the bone matrix wich ahs both organic and inrganic components
- -> organic: collagen, glycoproteins, other peptides
- -> inorganic: calcium, phosphate, hydroxide ions
- bone is vascular and innervated which is why it hurts to break; bone remains in vigorous equilibrium between construction and dstruction called remodeling
- strong bones require uniform distribution of inorganic material - bony matrix ordered into structural units called osteons or haversian systems
- -> each osteon circals central chanal called Haversian canal surrounded by concentriccircles of bny matrix called lamellae ( haversian system center of tree stump and rings are lamellae)
- -> canals contain bood vessels, nerve fibers, lymph
- -> spaced within matrix are spaces called lacunae which house mature bone cells called osteocytes which are involved in bone maintenance
4
Q
ossification (bone formation)
A
- hardening of cartilage process calle endochondral ossification and respnsible for formation of most long bones in body
- bones can also be formed through intramembranous ossification where undifferentiated enbryonic connective tissue (mesenchymal tissue) transformed into and replaced by bone
5
Q
bone remodeling
A
- osteoblasts build bone
- osteoclasts resorb or destroy bone
- during bone reformation, calcium and phosphate are obtained from the blood
- during bne resorption (breakdown) these ions released into bloodstream
- bone remodeling affected by exercisea nd use
6
Q
joints
A
- movable joints work like door hinges and allow for bones to shift relative to one another knees and elbows); strengthened by ligaments (fibrous tissue connect bones to one another); consist of a synovial capsule which encluses the actual joint cavity
- -> all structure are solid synovial fluid eases movement of one structure over the other –> synovial fluid is lubricant
- articular cartilage coat articular surfaces of bones so impact is restricted to lubricated joint cartilage
- immovable joints (skull) bones we wouldnot want to move relative to one another
7
Q
skeletal muscle
A
- contractile unit is sarcomere and when put together end to end create myofibrils
- myofibrils surrounded by SR
- outside sr is sarcoplasm (cytoplasm)
- cell membrane is sarcolema
- many myofibrils contained in each myocyte (muscle cells)
- t tubules connected to sarcolemma and orientated perpend to myofibrils
- red and white fibers in skeletal muscle; red (slow twitch) have high myoglobin and derive energy aerobically (myoglobin binds o2 more tightly than hemoglobin); white fibers (fasttwitch) are anaerobic and less myoglobin - contract more rapidly but fatigue easier
- red fibers mitochondria rich because derive enery aerobically and white fibers mitochondira poor because dont use electron transport chain for energy
8
Q
structure of the sarcomere
A
- thick filaments made up of myosin
- thin filaments made up of actin, troponin, tropomyosin
- z lines define boundaries of each sarcomere ( responsible for striation)
- m line runs down center of sarcoere
- i band region with only thin filaments
- h zone exclusively thick filaments
- a band has thick filaments in entirety including any overlap with thin filaments
- during contraction, h zone, i band, z lines distances all become smaller but a bands size remains constant
9
Q
contraction of skeletal muscle
1. initiation
A
- nervous system send signal to contract via motor neuron and this signal travel down neuron until reaches nerve terminal where it reeases acetylcholine into synapse -> results in contraction due to binding of nt to receptor on muscle
- connection point between nerve and muscle named neuromuscular junction
- if enough ach binds to muscle cell, muscle will be depolaried and sarcolemmas permeability increase
10
Q
contraction of skeletal muscle
2. shortening of sarcoere
A
- ap at neuromuscular jnct conducted along sarcolemma and t tubule system and transmitted into muscle fiber
- sr full of calcium
- massive release of calcium ions from the sr -> calcium bind to troponin causing tropomyosin to shift exposing myosin binding sites on actin
- the newly formed actin myosin cross bridges allow myosin to pull on actin which draws thin filaments ot center of h zone and shortens the sarcomere
- atpase in myosin heads provides energy for power stroke and results in dissociation of actin from myosin - myosin then resets itself by binding another molecule of atp and is free to bind to another actin molecule
11
Q
contraction of skeletal muscle
3. relaxation
A
once SR receptors not stimulated calcium levels will fall
- sr controls intracellular calcium so muscles are contracted only when necesary
- without calcium the myosin bidning sites will be covered by tropomyosin and prevent contraction
- after death ATP is no longer produced so myosin heads cannot detach from actin making it impossibe for muscles to relax - rigor mortis
- atp is required for both the contraction and release of the muscle fibers
12
Q
stimulus and muscle response of skeletal muscle
1. stimulus intensity
A
Muscle cells exhibit what is known as an all or nonresponse they either respond completely or not at all
Stimulus must reach a threshold value to respond
Maximal response occurs when all fibers are stimulated to contract simultaneously
Tonus refers to muscles in a constant state of low-level contraction
13
Q
- Simple twitch
A
- The response of a single muscle fiber to a brief stimulus at or above that threshold
- consists of a latent. Contraction. Relaxation.
- latents is the time between reaching threshold and onset of contraction, the actual potential spreads along the muscle and allows calcium to be released from the sarcoplasmic reticulum
- Refractory period Is when the muscle will be unresponsive to stimuli there are two types of refractory period -Absolute and relative
- during absolute refractory time no amount of stimulus will generate a response because the Muscle is restoring it’s resting potential
- during relative refractupory time the muscle can still be activated but a higher than normal stimulus is required
14
Q
- Summation and tetanus
A
- frequency summation occurs when muscle fibers are exposed to frequent and prolonged stimulation and they do not have enough time to relax -> the contractions will begin to combine becoming stronger and more prolonged
- eventually contractions they become so frequent that there is no time for the muscle to relax this is known as tetanus and is stronger than a simple muscle fiber twitch
