Case 9 Flashcards
Troponins
Troponin I binds to actin + troponinT, and inhibits actin myosin interaction unless Ca binds troponin C.
Titin
long filamentous protein links thick filaments to Zline.
Myomesins
bind to titin, generate hexagonal packing of thick filaments.
Tropomyosin
Thin filament structural component binding to actin.
A actinin
cross links actin at the sarcomere to Z disks.
Vinvulin
binds to A actinin
Dystrophin
links actin filaments to muscle cell outer membrane.
Nebulin
determines length of thin filament
Cap Z and tropomodulin
caps the + - end of thin filaments respectively.
Desmin
lonks together adjacent myofibrils at Z disk
Type of skeletal muscle fibre
determined by pattern of gene expression which is goverened bu firing pattern of motor neurone.
Type 1 fibre type
slow twitch, slow oxidative fibres. low myosin ATPase rate. Allow steady activity. Motor neurone has constant low firing frequency. Good supply of nutrients, high SA:Vol, good blood supply. Abundant mitochondria and myoglobulin so appear red. can use fat as source of energy.
Type 2a fibre type
fast oxidative glycolytic fibres. similar slow twitch. faster contraction and higher myosin ATPase activity. relitively resistent to fatigue. utilise glucose as well as fats. show burst of activity.
Type 2B fibres
fast twitch. fast glycolitic fibres. Highest myosin ATPase activity. Short maximal force. Not adapted for efficient exchange of nutrients and waste, low SA:Vol. limited blood S. pale colour as fewer mitochondria and myoglobulin. Generate ATP by substrate level phosphorylation glucose-lactic acid. Occasional bursts of high frequency impulses.
Oxidative phosphorylation
Used in slow twitch and intermediate fibres. Reduction of O2 to H2O using electrons from NADH and FADH2. Occurs in inner mitochondrial membrane. Explained by chemiosmotic theory. Involves exergonic. transmembrane chem + electical differences drives ATP synthesis.
substrate level phosphorylation
fast twitch. Direct formation ATP by phosphorylation ADP. Produced by reactions with high free energy. Dont require O2. Glycolysis: 1,3BPG + ADP - ATP + 3PG. TCA cycle, succinyl CoA + GDP - GTP + succinate. glycogen glucose lactate.
Cori cycle
oxygen is used by liver to produce glucose from lactate.
Effects of excersize on muscles
Inc mitochondria biogenesis. Via Ca signalling pathwaysas well as imbalence of ATP demand vs production which activates signalling protein kinases. AMPK fuel gauge of cell. Leptin may also operate via AMPK pathway. lack of excersize makes inc in NF-KB and myostatin which are important cell signalling molecules for muscle atrophy.
What is fitness
physically and psychologically able to meet the demands of your environment. Health related and skill related (usually task specific.)
VO2 max
the rate of volume of oxygen consumption while working at maximum capacity. can only improve by 15%
muscle unit
muscle fibres innervated by a single motor neuron
motor unit
muscle unit plus its motor neuron
motor neuron pool
coollection of neurons innervating a single muscle
Ach synthesis
Acetyl coenzyme A + choline with Choline acetyltransferace ChAT, to coenzyme A and Ach.
myocyte and fascicle
muscle cell.
bundle of myocytes. fasciculo many fascicles.
fascicle orientation
circular(orbicularis oris) Pennation, muscle fibres orientated at angle relative to line of action. uni, bi, multipennate. Parallel same direction from origin to insertion.
alpha motor neuron
supply extrafusal muscle fibre/ Large soma, fast myelinated axon. control muscle force. LMN
y motor neuron
supply intrafusal muscle spindle muscle fibers. smaller soma and myelanted axon. control muscle spindle responsiveness. LMN. CNS stimulates y resulting in contraction of intrafusal inc sensitivity.
muscle length is measured by
muscle spindles
muscle tension is measured by
golgi tendon organs
golgi tendon organs
detect force of contraction. between tendon and muscle, sensory Ib neurons. Signal via inhibitory interneurons to inhibit further contraction. golgi tendon organ - Ib - inhibitory interneuron - Alpha motor neuron
lower motor neuron lesion
weakness, atrophy, dec reflexes, dec tone
UMN lesion
weakness, inc reflex, inc tone/spasticity. Babinski sign.
osteoprogenitor cell
mesenchymal stem cell that divides into osteoblasts. Maintain the population of osteoblasts-important in repair of fracture. Located in the periosteum and bone marrow (ondosteum)
osteoblasts
form new bone matrix in a process called osteogenesis, form osteoid which is then calcified to bone. When they surround themselves in extracellular matrix, become trapped and - osteocytes-mature bone cell.
osteogenesis
osteoblasts secrete collagen and ground substances. collagen mol combine to form collagen fibres - osteoid(non calcified bone) hydroxyapatite crystals form on collagen, its now calcified.
Osteocyte
mature bone cell cant divide, occupy one lacuna, occupying layers called lamellae. Lamellae are connected by canaliculi, providing nutrients from the central canal. Can convert back to an osteoblast.
osteoclast
derived from granulocyte/monocyte progenitor cells. multinucleated involved in bone resorption. secretes enzymes which dissolve matrix release stored minerals into BS. Process - osteolysis. Important in regulating Ca and phosphate concs in body.
bone remodelling
Osteoclast adhere trabecular bone, secrete H ions and Proteolytic enzymes by osteolysis. IGF1 TGF B released which recruit osteoblasts. secrete osteoid and IGF1 TGFB into it. then calcified, some osteoblasts embedded form osteocyte.
bone remodelling following fracture
haematoma formation. fibrocartilaginous callus forms. Internal callus cartilage. External callus cart and bone. at centre differentiate into chondrocytes produce hyaline cart. At edges diff into osteoblasts begin creating bridge. Replace with woven bone, then remodelling occurs. can be stronger than before.
actin
G actin hold ADP - active site. Tropomyosin wrapped around F actin helix.
three layers of connctive tissue that extend from fascia to protect and strenghten muscle
Epimysium - encircles entire muscle. Perimysium - seperates into fascicles. Endomysium - seperatres individual fibres. extend to form tendon.
excitation contraction coupling
AP spreads along T tubule, act on longditudinal sarcoplasmic tubules to cause release of Ca into sarcoplasm from sarc retic. Ca induced Ca release: open voltage gated Ca, activates ryanodine receptor channels in sarc retic triggers release into sarcoplasm. strength of contraction depends on conc Ca store.
Ca pumped out by
Na Ca exchanger, into sarc retic by SERCA pumo and t tubule extracellular fluid through plasma mem by PMCA pump. or stored sarc retic.
bands in contraction
H + I shorten, A stays the same.
summation in muscular contraction
inc number of motor units contracting simultaneously-multiple fibre summation, inc fre of contraction-frequence summation, lead tetanisation.
types of muscle contraction
isometric-length of muscle remain unchanges. Isotonic-length shortens but tension is constant. Concentris-in direction of contractionm towards origin. Eccentric-opposite direction of contraction towards insertion
creatine phosphokinase
phosphocreatine contains high energy phosphate bonds used to phosphorylate ADP to ATP by creating kindase, located in the Z lines.
myokinase
enzyme myokinase catalyses the transfer of phosphate from one ADP to another by product adenosine monophosphate. last gasp.
muscle strength
highest amount of effort excerted to overcome the most resistence in a single effort. depends on size, fascicle arrangement, size of active motor units, multiple motor unit summation, temporal summation, fatigue.
length tension relationship
tension generated bu a muscle so force of contraction depends on how contracted it was before. when contracted at rest thick fillament nearer z lines so can only contract a little. when too stretched to start myosin heads cant get good grip so little contraction. CNS maintains muscle tone making optimum length ready for contraction.
latent period
delay about 2msec between onset of stim and twitch, time for excitation ECC, tensing of elastic components. Force generated in this time is internal tension.
muscle atrophy
remains unused, pathway that causes protein degradation is ATP dependant ubiquitin proteasome pathway. proteasomes degrade damaged or unneeded proteins by proteolysis. ubiquitin is regulatory protein that labels which cells will be targeted for proteasomal degradation.
stance phase of gait
begins with heel strike ends with push off. 60% of cycle
muscles involves in stance phase
heel strike - gluteus maxiimus and tibialis anterior. Loading response/flat foot-quadriceps femoris. Midstance-soleus and gastrocnemius. terminal stance-gastrocnemius and soleus.
swing phase of gait
when toe leaves the ground to when heel strikes
muscles involved in swing phase
preswing-rectus femoris. initial and midswing-iliopsoas and rectus femoris. terminal swing-hamstrings, tibialis ant and ankle dorsiflexors.
apraxic gait
frontal lobe damage, disorganized walking, shuffling small steps marche a petit pas, broad based, forgotten how to walk.
waddling gait/myopathic
muscle/hip disease, patient bends their pelvis forward and walks with a waddle.
crossing over/scissoring gait
bilateral spasticity. walk stiffly on toe, problems turning.
parkinsonian gait
small paces slow shuffling. stooped posture reduced arm swing. tremor. basal ganglia dysfunction.
hemiplegic
unilateral upper motor neuron lesion, MS or stroke. flexed upper limb extend lower. circumduct leg.
diplegic gait
swinging both sides
cerebellar ataxia gait
broad based, sway, fall, drunk.
sensory ataxia
over flexes hip lifts knee high slaps foot. can happen in nerve lesion.
romberg test
eyes open 3 sensory systems feed into cerebellum to maintain truncal stability. ask feet together then close eyes, if proprioception and vestibular pathways intact wont sway. if sways romberg positive. if sway eyes closed proprioception defect. if with eyes open cerebellar lesion.
orthosis
surgical device exerts ecternal forces on body sipport joint.
osteophyte
bony projections in sites of cartilage degeneration near joints. form due damage joints SA. Common from onset arthritis.
anterior cruciate ligament tear
more common in woman. grade 1: stretched but no tear, tenderness and swelling. Grade II; partially torn, tenderness and swelling may feel unstable and give way. Grade III: completly torn, Swelling, cant control knee movement give way. Lachmans test positive.
female athlete triad syndrome
eating disorder, amenorrhoea, dec bone density.
Amenorrhoea
primary-absense of menstruation by 16. secondary, absense for 3 months in woman whove had cycles. weight fluctuations effect outpul of gonadotropic hormones. dec oestrogen.
shin splints
pain along inner edge of tibia. repeated trauma to connective muscle tissue.. over pronation is common cause. pain from disruption of Sharpeys fibres that connect medial soleus through periosteum of tibia.
marfan fibres
elastic fibres
sharpneys fibres
bone fibres, or perforating fibres) are a matrix of connective tissue consisting of bundles of strong collagenous fibres connecting periosteum to bone
woven bone
Woven bone is characterized by a haphazard organization of collagen fibers and is mechanically weak. Lamellar bone is characterized by a regular parallel alignment of collagen into sheets (lamellae) and is mechanically strong.
