A&P Week 6 part 1- skeletal muscles.

winniesmith's version from 2016-12-05 23:30

Section 1

Question Answer
What does skeletal muscle contain?connective tissue, nerve tissue and blood vessels.
3 types of connective tissueEpimysium, Perimysium, Endomysium
what is the main function of the epimysiumExterior collagen layer. Separates muscles from surrounding tissues.
what is the main function of the periysiumSurrounds muscle fibre bundles (fascicles). Contains blood vessel and nerve supply to fascicles. Separates fascicles.
what is the main function of the endomysiumSurrounds individual muscle cells (muscle fibres). Contains capillaries and nerve fibres contacting muscle cells
What are the levels of functional organization in a skeletal muscle friberSurrounded by epimysium - contain muscle fascicles.
Muscle fascicles are surrounded by perimysium - contain muscle fibers. Muscle fiber is surrounded by endomysium- contain myofibrils. Myofibril surrounded by sarcoplasmic reticulum- consists of sarcomeres.
Sarcomere - contains think and thin filaments (actin and myosin)
What is a sarcolemma?Cell membrane, surrounds the sarcoplasm. Excitable membrane, change in membrane potential begins a contaction.
what is a transversetubule?Continuous with sarcolemma. Transmit action potential through cell- conduct action potentials rapidly. Allows entire fiber to contract simultaneously.
what are myofibrils?Bundles of protein filaments (myofilaments). Myofilaments responsible for muscle contraction. Thin filaments (actin). Thick filaments (myosin).
what is the sarcoplasmic reticulum?Membranous structure surrounding each myofibril. Helps transmit action potentials to myofibril Forms chambers
What are cisternae?in sarcoplasmic reticulum. Contain high conc. of calcium ions. Release Ca2+ into sarcomeres to begin muscl contraction.
What is a sarcomere?The contractile units of muscle. Functional unit of myofibrils. Dark and Light striations, zones overlap. ( Z line to Z line)
What does Ca2+ do?Released by SR causes thin and think filaments to interact.

Section 2

Question Answer
What proteins are in a thin filament?Actin, Tropomyosin, Troponin
Structure of thin filaments at restActive sites are covered by tropomyosin, held in place by troponin.
What proteins are in thick filaments?Myosin- made up of myosin tail and myosin head- pointing away from center.
What is a skeletal muscle controlled bymotor neuron and neuromuscular junctions.
structure of NMJSingle axon branches within the perimysium. Each branch ends at an expanded synaptic terminal
what is the main neurotransmitter at synaptic terminals for skeletal muscles?ACh.
what does ACh do?ACh release alters the permeability of the sarcolemma, triggering muscle contraction
What happens at the synaptic terminal1) Arrival of action potential at synaptic terminal.
2)release of ACH.
3)Ach binds at the motor end plate.
4) Appearance of action potential in the sarcolemma.
5)return to normal state.
What happens when an action potential occurs in the muscle fiberGenerated by increase in sodium ions in sarcolemma. Travels along T tubules, leads to excitation-contraction coupling. Ca2+ released triggering contraction.
Outline the contraction cycle1) The exposure of the active site following the binding of Ca2+ to troponin.
2) Attachment of the myosin cross-bridge to the exposed active site on the thin filaments.
3)Pivoting of the attached myosin head and the release of ADP and a phosphate.
4)Detachment of the cross-bridges when the myosin head binds to another ATP molecule.
5) Reactivation of the detached myosin head as it splits the ATP and captures the released energy