anatomy of muscles

Question 1

functions of the muscular system

Answer 1

• allows movement of body
• maintains posture
• circulates blood

Question 2

what are the types of muscles (structure / function)

Answer 2

• skeletal: voluntary, attached to bone, long cylindrical, stripes, striated, multi nucleated (peripheral), powerful, epimysium, perimysium and endomysium
• smooth: involuntary, no striations, uninucleate (basal), walls of hollow organs, follicles in skin, long tapered cells, work together / individually, endomysium
• cardiac: involuntary, walls of heart, striated, branched, uninucleate, auto rhythmic
  (pacemaker, beat without nerves), independent, endomysium

Question 3

what is a ligament vs tendon

Answer 3

• L: short band of tough flexible, fibrous connective tissue, connects two bones, holds joints together
• T: flexible but inelastic cord of strong fibrous collagen, attaches muscle to bone

Question 4

summary of skeletal muscle function

Answer 4

• connect firmly to bones through tendons
• ~40% of body weight
• contraction: force exerted = pull, always contract / shorten
• generate ATP (mechanic / heat energy), stabilise moveable joints (at rest), work in pairs or larger groups

Question 5

why is it called the musculoskeletal system

Answer 5

• skeletal system (endoskeleton) works very closely with muscles
• ability to move, collapse without it

Question 6

name flexors, extensors, adductors and abductors of the upper leg (10)

Answer 6

• F: iliopsoas (iliacus, psoas major), quadriceps rectus femoris, sartorius
• E: gluteus maximus and hamstrings
• AD: adductor group
• AB: gluteus medius, gluteus minimus, piriformis, tensor fascia latae

Question 7

what are two muscles in the upper leg with multiple actions

Answer 7

• quadriceps femoris: contraction = extension at knee and flexion at hip
• hamstrings: contraction = flexion at knee and extension at hip

Question 8

name the 4 muscles of the lower leg (calf / knee)

Answer 8

• gastrocnemius (posterior crural)
• soleus (posterior crural)
• tibialis anterior (anterior crural)

Question 9

types of skeletal muscle (arrangement of fassicles / fibres)

Answer 9

• fusiform: parallel muscular fibres to long axis of muscle (biceps brachii)
• parallel: transverse lines which divide muscle into several bellies (rectus abdominis)
• convergent: wide muscle where fibres convert into a common tendon (pectoralis major)
• pennate: short, oblique, attached to common tendon that runs through middle of muscle, unipenate (palmar interosseous) and bi pennate (rectus femoris)
• circular: concentric rings, openings (obicularis oculi)

Question 10

name the 3 main abdominal muscles

Answer 10

• transverse abdominis
• internal / external oblique
• rectus abdominis (tendinous intersections and linea albs, same layer as internal oblique - middle)

Question 11

name the 3 main back muscles

Answer 11

• trapezius
• rhomboid major
• rhomboid minor

Question 12

name the 3 groups of facial expression

Answer 12

• orbital
• nasal
• oral

Question 13

name the 2 main muscles of respiration

Answer 13

• diaphragm

- intercostal muscles (internal and external)

Question 14

name the 4 main muscles of the trunk

Answer 14

• pectoralis major
• pectoralis minor
• serrates anterior
• subclavius

Question 15

name the 3 main shoulder muscles

Answer 15

• deltoid
• rotator cuff (subscapularis, supraspinatus, infraspinatus, teres minor)
• latissimus dorsi

Question 16

name the 3 main muscles of the elbow

Answer 16

• biceps brachii
• brachialis
• triceps brachii

Question 17

name the 6 main muscles of the forearm

Answer 17

• flexor carpi ulnaris
• flexor carpi radialis
• palmaris longus
• pronator teres
• extensor carpi ulnaris
• flexor / extensors retinaculum (tendinous)

Question 18

what is carpel tunnel syndrome

Answer 18

• transverse carpal ligament: nerve, runs through forearm to hand, sensory information, lateral portion of hand, first 3 fingers and half of fourth finger
• pressure on nerves by swelling and inflammation of carpal tunnel
• impacts everything that passes through nerve, tendons / muscles, numb / tingling
• painkillers or surgery

Question 19

what are the 3 coverings of muscle

Answer 19

• epimysium: dense regular connective tissue surrounding entire muscle
• perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibres)
• endomysium: fine areolar connective tissue surrounding each muscle fibre
• each tissue extends beyond muscle belly and fuse together to form tendon and then bone

Question 20

what are the two types of fascia (connective tissue)

Answer 20

• superficial fascia: loose connective tissue and fat underlying the skin
• deep fascia: dense irregular connective tissue around muscle (all)

Question 21

describe the microscopic anatomy of a skeletal

Answer 21

• cylindrical cells up to 30 cm long
• multiple peripheral nuclei many mitochondria
• glycosomes for glycogen storage (energy), myoglobin for oxygen storage
• myofibrils (contraction, made up of sarcomeres) form muscle fibre
• sarcomere - myofibril - muscle fibre - fascicle - muscle

Question 22

what is a sarcomere

Answer 22

• smallest contractile unit of muscle
• contain protein filaments (actin and myosin)
• comprised between two transverse Z lines
• I band: striations, light band, contain Z line
• A band: dark bands (actin and myosin)
• H zone: midline of sarcomere, between two Z lines

Question 23

describe the structure of thick and thin filaments

Answer 23

• thin: actin, globular (G) subunits, G actin bears active sites for myosin head attachment during contraction, attached to Z disc / I band, contain tropomyosin / troponin (stabilise, regulate)
• thick: myosin tails (heavy polypeptide chains), myosin heads (light polypeptide chains, bridge binding site of ATP, ATPase detach P to form ADP + energy), attached to midline (H zone)

Question 24

what is the sarcoplasmic reticulum / T tubules

Answer 24

• SR: forms two transverse channels (terminal cisternae), smooth ER surrounding myofibrils, regulation of Ca levels, production of energy
• TT: membrane of sarcolemma, carry impulses to sarcolemma from surface
• terminal cisternae + TT = triad

Question 25

what are the requirements for skeletal muscle contraction

Answer 25

• activation: neural stimulation at a neuromuscular junction, binding of neurotransmitters = electric current
• exictation-contraction: generation and propagation of action potential, rise in Ca levels = contraction

Question 26

describe the events in generation of action potential in a muscle cell

Answer 26

• resting = -70mV
• local depolarisation: ACh binding opens chemically ligand gated ion channels, inflow of Na outflow of K (interior of sarcolemma = negative)
• generation / propagation of action potential: end plate potential spreads to adjacent areas, increase Na inside (-55mV = threshold = rapid depolarisation = +30mV)
• repolarisation: Na channels close, voltage gated K channels open, K efflux restores resting polarity, ACh attaches to Na K pump (energy) = restores (active)

Question 27

describe the steps involved with the sliding filament model of contraction

Answer 27

• no connection between A and M but have a high affinity for one another
• action potential triggers voltage sensitive proteins linked to Ca channels in sarcoplasmic reticulum to open
• Ca floods into cell, troponin + Ca bind = movement of tropomyosin away from active sites
• myosin heads + ADP + P + energy = head extends = binds to actin = releases stored energy and myosin changes shape = pull on strands and shrink sarcomere
• ADP + P unbind = new ATP binds in place on myosin head = release from actin, breakdown ATP to ADP + P and repeat process on another actin
• Ca unbinds and myosin cannot bind to actin anymore

Question 28

what is the all or none law

Answer 28

• contraction is complete or not at all
• entire muscle contracts at same time (motor unit)
• reaches point where all fibres are distressed and no more force can be applied

Question 29

relationship of tropomyosin and troponin and calcium levels

Answer 29

• low Ca: normal, tropomyosin blocks active site of actin, myosin cannot attach
• high Ca: Ca binds to troponin, changes shape and moves tropomyosin away from active sites, cross bridge cycle occur (contraction)

Question 30

what is the nerve-muscle functional unit

Answer 30

• small motor unit = control fine movement
• large motor unit = weight bearing muscles
• muscle fibres spread throughout muscle = single motor unit causes weak contraction of whole muscle