Exam 3 short answer Flashcards
Know the 8 functions of muscles.
- Movement of bones
- Maintaining posture and body position
- Stabilizing joints
- Heat generation
- Supports soft tissues
- Protects organs
- forms valves
- controls pupil size
Define origin and insertion.
Insertion – movable bone
Origin – immovable (less movable) bone
Define sarcolemma, myofibrils and sarcoplasmic reticulum
Sarcolemma = plasma membrane on skeletal muscle fiber
Myofibrils: basic rod-like organelle of a muscle cell
sarcoplasm reticulum: Network of smooth endoplasmic reticulum surrounding each myofibril
Define sarcomere, T tubules, triad
Sarcomere: region between two successive Z discs
t-tubules: Continuations of sarcolemma
triad:
Define tropomyosin and troponin.
two proteins that are present on the thin filaments of the muscle cells and help in the contraction of muscles.
troponin promotes muscle contraction, tropomyosin blocks muscle contraction.
What is the function of the sarcoplasmic reticulum?
Stores and releases Ca2+
What structure increases the surface area of the muscle fiber?
T-Tubules
Understand the sliding filament model of contraction.
- calcium ions are released by the sarcoplasmic reticulum in the actin filament.
- Calcium ions cause cross bridges (bond) to form
- Myosin head slides
- skeletal muscle contraction has occurred
- Cross bridge breaks
- troponin resets the actin to its original position
What occurs during a cross bridge cycle? Be able to recognize the steps.
- the cross bridge is formed by energized myosin heads that attach to actin myofilaments
- power working stroke: myosin head pivots and pulls thin filament towards M line
- cross bridge detaches- ATP attaches to myosin head and cross bridge detaches.
- Cocking of myosin head: energy from hydrolosis of ATP cocks myosin head into high energy state.
What is excitation contraction coupling?
- Action potential propagated along sarcolemma
- Intracellular Ca2+ levels must rise briefly
Know the components of a neuromuscular junction:
a. Axon terminal (presynaptic axon)
b. Synaptic cleft: gap between the pre- and postsynaptic cells
c. Sarcolemma (postsynaptic membrane; junctional folds)
Understand the steps which occur at the NMJ during a nerve stimulus:
ACh is broken down by acetylcholinesterase. AChE
Describe the cross bridge cycle and its components
a. Why is calcium important?
b. What is the function of ATP on the myosin head? .
a. Continues as long as Ca2+ signal and adequate ATP present
b. Cross bridge detachment—ATP attaches to myosin
head and cross bridge detaches
List the 4 patterns of fascicles. Provide an example for each.
– Circular: orbicularis oris
– Convergent: pectoralis major
– Parallel: sartorius
– Pennate: rectus femoris
What is the most common type of “lever” in the body; provide an example.
third class level.
example: forceps and most skeletal muscles
