Skeletal and Muscular Systems

Question 1

what is the purpose of the musculoskeletal system

Answer 1

• forms the basic frameowrk of the vertebrate body
• muscles and bones work in close coordination to produce voluntary mvoement
• physical support and locomotion are also functions

Question 2

what is the purpose of the endoskeleton

Answer 2

• serves as a framework within vertebraet systems
• muscles are attached to the bones permitting movement
• endoskeleton also provides protection by surrounding delicate vital organs in bone
• rib cage protects the thoracic organs (heart and lungs)
• skull and vertebral column protect the spinal cord

Question 3

what is cartilage

Answer 3

• one of two major components of the skeleton
• type of connective tissue that is softer and more flexible then bone
• retined in places where firmness and flexibility are needed: external ear, nose, walls of larynx and trachea and skeletal joints

Question 4

what is responsible for synthesizing cartilage?

Answer 4

chrondrocytes

Question 5

what is bone and the two types

Answer 5

• bone is a specialized type of mineralized connective tissue that has the ability to withstand physical stress

Compact bone

• dense and does not appear to have cavities when observed by nake dyee
• bony matrix is deposited in structural units called osteons consisting of central microscopic channels called haversian canal
  
  • surrounded by concentric circles of bony matrix (calcium phosphate) called lamellae

Spongey Bone

• much less dense and consists of inerconnecting lattice of boney spicules
• cavities between the spicules are filled with yellow or red bone marrow
  
  • Yellow marrow is inactive and infiltrated by adipose tissue
  • Red marrow is involved in blood cell formation

Question 6

what are osteocytes

Answer 6

• two other cell types found in bone tissue are osteoblasts and osteroclasts

Osteoblasts:

• synthesize and secrete the organic constituents of the bone matrix
• once surrounded by matrix they mature into osteocytes

Osteoclasts:

• large multinucleated cells involved in bone reabsorption wherein bone is broken down and minerals are released into the blood

Question 7

explain bone formation

Answer 7

• occurs by enochondral ossifcation or inramembranous ossifcation
• endochondral ossifcation: existing cartilage is replaced by bone, long bones arise primarily through endochondral ossifcation
• Intramembranous ossifcation: mesenchymal (embryonic or undifferentiaed) connective tissue is transformed into and replaced by bone

Question 8

what is the axial skeleton and how are bones held together

Answer 8

• axial skeleton is the basic frameowrk of the body, consists of skull vertebral column and rib cage
• it is the point of attachment of the appendicular skelton which includes the bones of the appendages (limbs) and the pectoral and pelvic girdles
• sutures or immoveable joints hold bones of skull together
• bones that move relative to one another are held by moveable joints and are supported by ligments

Question 9

what are ligaments and tendons

Answer 9

• ligaments serve as bone-to-bone connectors
• tendons attach skeletal muscle to bones and bend the skeleton at moveable joins

Question 10

what are origins and insertion

Answer 10

• point of attachment of a muscle to a stationary bone (proximal end of limb muscles) is the origin
• the point of attachment of a muscle to a bone that moves (distal end of limb muscles) is the insertion

Question 11

extension vs flexion

Answer 11

extension indicated the straightening of a joint

• flexion refers to te bending of a joint

Question 12

what does muscle tissue consist of and what are the 3 types of musle in mammals

Answer 12

• muscle tissue consists of bundles of specialized contractile fibers fild be connective tissue
• types: skeletal, smoother and cardian

Question 13

what is involved in nervous control of the muscular system

Answer 13

axons of the pyramidal cells of the motor cortex which descend from the brain to synpase on lower motor neurons in the brain stem and spinal cord

• pyramidal and extrapyramidal system

Question 14

what is the pyramidal system and extrapyramidal system

Answer 14

pyramidal:

• contains no intervening synpases
• able to provide rapid commands to the skeletal muscles and various other organs

Extrapyramidal

• issues somatic motor commands as a result of processing performed at the unconcious involuntary level
• red nucleus located in the mesencephalon is the commponent of the extrapyramidal system primarily in control of skeletal muscle tone

Question 15

what is skeletal muscle and what is it composed of?

Answer 15

• responsible for voluntary movements and is innervated by the somatic nervous sytem
• each fiber is a multinucleated cell created by the fusion of several mononucleated embryonic calls
• each fiber contains myofibrils which divide into contractile sacromeres
• myofibriles are envolved by sacromeres reticulum which stores calcium ions
• cutoplasm of muscle fiber is called sarcoplasm and membrane called sarcolemma

Question 16

what is the role of the sarcolemma and T system

Answer 16

• specialized cell membrane which surrounds striated muscle fiber cells
• capable of propogating an action potential and is connected to a sytem of transverse tubules (T system) oriented perpendicularly to the myofibrils
• T system provides channels for ion flow throughout the muscle fibers and can propogate an action potential

*mitochondria very abundant in muscle cells bc high enregy requirement they are distributed along myofibrils

Question 17

what is skeletal muscle refered to as and why

Answer 17

• striated muscle
• bc has striations of light and dark bands

Question 18

what are sacromeres and how are the organized

Answer 18

• composed of thick and thin filaments
• thin filaments are chains of actin molecules and thick are organized bundles of myosin mol
• organized as follows
• Z line: defines the boundaries of a single sacromere and anchors the thin filaments
• M line: runs down the center of the sacromere
• I band: region containing thin filaments only
• H zone: region containing thick filaments only
• A band: soand entire length of thick filaments and any overlapping portions of thin

*when muslces contract the Z lines move towards eachother, A band is not rduced in size whereas the Z zone and I band are

Question 19

what triggers mucel contraction, what causes the generation of an action potential

Answer 19

• stimulated be a message from somatic NS via motor neuron
• link between the nerve terminal (synpatic bouton) and sarcolemme of muscle fiber = neuromuscular junction
• space between the two is called the synpase or synpatic cleft
• depolarization of the motor neuron results in relase of neurotransmitter (acetylcholine) which diffuses across synaptic cleft and binds to recepotor on sarcolemma
• if enough receptors are stimulated the permeability of sarcolemma is altered and action potential is generated

Question 20

what occurs once an action potential is generated is muscle

Answer 20

• conducted along the sarcolemme and the T system and into the interior of the muscle fiber
• causes the sarcoplasmic reticulum to release calcium ions into sarcoplasm
• calcium ions initiate the contraction of the sacromere by binding troponin C on actin filaments
• allosteric changes occur in the proteins that allow myosin heads to bind to these sites on actin
• use of energy allows the power stroke to occur pulling Z bands closer together

*actin and myosin slide past each other and the sacromere contracts

Question 21

what is rigor mortis

Answer 21

• several hours after death muscles in the body contract and become rigid even w/o action potentials
• rigidity is caused be absense of ATP which is required for the myosin heads to be released from acitn filaments

Question 22

what are the 5 major types of muscle contraction

Answer 22

• isotonic, dynamic, concentric, eccentric and isometric
  isotonic: occurs when muscle shortens against a fixed load while tension on that msucle remains constant

dynamic: includes both concentric and eccentric, rults in change in length of the mucle with a corresponding change in tenion of that muscle

concentric: type of dynamic contraction where muscle fibers shorten and tension inc

eccentric: type of dynamic contraction where the muscle fiber lengthens and tenion inc

isometic: occurs when both ends of the muscle are fixed and no change in length occurs during contraction but tension inc

Question 23

explain the all or non respons of muscle fibers

Answer 23

• only a stimulus above the threshold value can elicit a contraction
• the strength of the contraction of a single muscle fiber cannot be increased regardless of the size of the stimulus
• strength of muscle contraction of the entire muscle can be increased by recruiting more muscle fibers

Question 24

explain a simple twitch

Answer 24

• response of a single muscle fiber to breif stimulus at or above threshold stimulus
• consists of a latent period, contraction period and relaxation period
• latent = time between stimulation and the onset of contraction
• during time lab the action potential spreads along the sarcolemma and Ca²⁺ ions are released
• after contraction period there is a breif relazation period in which muscle is unresponsibel to a stimulus (absolute refractory period)

Question 25

what is temporal summation

Answer 25

- occurs when fibers of muscle are exposed to very frequent stimuli and muscle cannot fully relax - contractions begin to cobine becoming stronger and more prolonged - contractions become continuous when the stimuli are so frequent that muscle cant relax - known as **tetanus** ans is stronger than a simple twich of a single fiber

Question 26

what is tonus

Answer 26

- state of partial contraction - muscles are never completely relaxed and maintain a partially contracted state at all times

Question 27

what occurs during strengous activity for energy

Answer 27

- during stenious activity skeletal muscles convert glucose to pyruvic acid through glycolysis enabeling skeletal muslces to contrinue contracting even in absence of oxygen - lactic acid is generated when pyruvic acid is reacted with lactate dehydrogenase: allows the pyruvate to enter the cirtic acid cycle

Question 28

what is the cori cycle

Answer 28

- during strenuous activity cori cycle converts lactic acid in liver to glucose for dischange into the bloodstream - once glucose is in the blood the muscles are able to use glucose as an immediate source of energy to rebuild glycogen reserves \*convresion of glucose into pyruvate in muscle cells is necessary for creation of ATP uring excersise does not involve the cori cycle

Question 29

what is smooth muscle and main artibutes

Answer 29

- responsible for involuntary actions and is innervated by the autonomic enrvous system - found in digestive tract, bladder, uterus, and blood vessel walls - possess one centrally located nucleus and lack the striations of skeletal msucle - non striated, one nucleus cell, involuntary/autonomic NS, smooth continuous contractions

Question 30

what is cardiac muscle and main properties

Answer 30

- muscle tissue of the heart, fibers possess characteristics of both smooth and skeletal muscle - has actin and myosin filaments arranged in sacromeres giving a striated appearance - only 1 or 2 centrally located nuclei - involuntary/autonomic NS - storng forceful contractions

Question 31

main properties of skeletal muscle

Answer 31

- striated, multinucleated, voluntary/somatic NS, strong forceful contractions

Question 32

what is the primary energy reserve for muscle contraction

Answer 32

ATP, very little ATP is actually stored in muscles so other forms o energy must be stored and rapidly converted into atp

Question 33

what is crreatine phosphate

Answer 33

- in vertebrated energy can be temporarily stored in a high energy compound: creatine phosphate