SWA POINTS TO NOTE Flashcards
Describe the femoral sheath with its contents and relationships.
Extension of transversalis fascia, forms a sheath around the femoral artery and vein, but contains lymph nodes medially in the “space” that is the femoral canal. The femoral nerve lies laterally, but outside the sheath (1/2)
Where would you palpate the superficial inguinal lymph nodes?
In a “T” shape – parallel to the inguinal ligament and alongside the great saphenous vein
What are the boundaries of the femoral canal?
Lacunar ligament - medial
Femoral vein – lateral
Pectineus or Pectineal ligament – posterior
Inguinal ligament – anterior
What are the four structures that enter the adductor canal, but which of these continue into the popliteal fossa by passing through the adductor hiatus?
Saphenous nerve
Nerve to vastus medialis
Femoral artery & vein (which continue into popliteal fossa)
What is it about the structure of skeletal muscle that enables it produce a diffraction pattern?
The ultrastructure of skeletal muscle fibres are such that the sarcomeres in a fibre line up with the dark A bands and the light I bands in register. This arrangement means the fibre behaves as a diffraction grating which is capable of diffracting a laser with a wavelength of around 0.6 μm.
What is the role of calsequestrin in the contractile process?
Calsequestrin is one of the main calcium binding proteins located in the sarcoplasmic reticulum of skeletal muscle. Calsequestrin can bind up to 43 Ca2+ ions per molecule and as such acts as a store for calcium. When the RYR receptor protein channel (calcium release channel of the SR) opens as a result of depolarisation of the sarcolemma via the conformational chance in the DHP receptor protein channel (L-type calcium channel of the sarcolemma), calcium dissociates from its low affinity sites on calsequestrin and diffuses down a steep concentration gradient between the inside of the SR and the cytoplasm. The end result is for the cytoplasmic calcium concentration to increase from 10 -5 M. Calsequestrin binds the Ca2+ pumped back into the SR by the Ca-ATPase during the process of relaxation.
Describe 3 events in skeletal muscle fibre activation and relaxation which have an absolute requirement for ATP
(1) ATP binds to the myosin head in order to break the link between the actin & myosin filament (the detachment step in the cross bridge cycle)
(2) ATP is hydrolysed by the myosin-ATPase located on the myosin head. This results in the production of energised myosin which can bind to the actin filament when the intracellular Ca2+ concentration increases above 10-5 M (the repriming step)
(3) ATP is required for hydrolysis by the Ca2+-ATPase enzyme of the sarcoplasmic reticulum. This active transport system is responsible for pumping Ca2+ from the cytoplasm back into the SR and so bringing about relaxation
What type of skeletal muscle fibre is innervated by alpha-motoneurones forming small motor units?
Slow oxidative
What type of skeletal muscle fibre is innervated by alpha-motoneurones forming large motor units?
Fast glycolytic
Discuss the relative yield of ATP produced by glycolysis and the citric acid cycle under aerobic and anaerobic conditions.
Glycolysis will generate about 5-8 molecules of ATP per molecule of glucose processed to pyruvate (depending whether the starting point is glucose or glucose-6-P) by glycolysis under aerobic conditions. Under anaerobic conditions glycolysis of one glucose molecule will only produce 2-3 molecules of ATP. Under aerobic conditions each turn of the citric acid cycle (starting with pyruvate) will produce about 15 molecules of ATP. Since each glucose molecules produces 2 moleculesofpyruvate,theATPyield=15x2=30.
In smooth muscle, why is there a delay between the activation of the membrane potential and the tension being produced?
The long latent period seen in smooth muscle is the result of the time required to elevate the intracellular calcium concentration above 10-5 M. Even though smooth muscle cells are small and have a high surface area/volume ratio the diffusion of calcium from extracellular space or the activation of the second messenger IP3 system takes a significantly longer time than the voltage activation seen in cardiac and skeletal muscle.
What are 3 sources of calcium involved in the excitation contraction coupling of smooth muscle and explain the release mechanism for these three sources.
- Voltage-dependant calcium channels
- depolarisation of the cell membrane will cause the voltage-dependant calcium channels to open and allow Ca2+ to diffuse from a high extracellular Ca2+concentration (2x10-3 M) through the channels to increase the intracellular Ca2+ from 10-5 M - Ligand-(hormone or neurotransmitter) gated calcium channel
- same as 1 but in this case the Ca2+ ion channel is linked to either a hormone or neurotransmitter membrane protein - Calcium from intracellular stores whose release is triggered via the activation of phospholipase C, hydrolysis of phosphatidylinositol and the formation of IP3. Activation of the IP3 receptors on the rudimentary sarcoplasmic reticulum vesicles brings about the release of stored calcium.
What would be the effects on the hand if the median nerve was damaged?
Loss of opposition
Atrophy of thenar eminence
Loss of sensation over lateral 3.5 digits
What lies immediately deep to the fibrous flexor sheath?
Synovial sheath
