intro to Skeletal Muscle Structure, Function & Metabolism Flashcards
what are the three types of muscle tissue
- skeletal
- cardiac
- smooth
what are 4 features of skeletal muscle
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think:
- locomotion,
- body weight,
- multinucleate cells and what they have
- willingness of contraction
- attach to and move skeleton
- 40% of body weight
- there are multinucleate cells with ovbious striations
- contraction of this musle is voluntary
what are 2 features of cardiac muscle other than being only found in the heart
Think about visibility of the cells and willingness of contraction
- cells are striated
- contractions are involuntary
what are 2 features of smooth muscles other than them being in the walls of hollow organs
- lack striations
- contractions are involuntary
skeletal muscle tissue
what are the 3 functions of skeletal muscle
Think shivering, storage and mobility
- heat generation (shivering and involuntary contractions)
- nitrogen store/metabolism (CHO/PRO)
- locomotion/external movement
skeletal muscle
what attaches skeletal muscle to the skeleton
tendons
skeletal muscle
what is the site at which skeletal muscle is attached to an immobile bone at one end called?
the origin
skeeletal muscle
what is the site at which skeletal muscle attaches to a bone and moves it called?
the insertion
what needs to occur before tension at the muscle attachement sites occur?
stretch of the elastic/non-contractile parts of the muscle
skeletal muscle ultrastructure
what are 2 features of myofibres (muscle cells)
- elongated cells
- arranged parallel to one another and bundled by connnective tissue into fascicles
skeletal muscle ultrastructure
what is the sarcolemma
muscle cells’ cell membrane
SKM connective tissue
what is:
- superficial fascia
- deep fascia
superficial fascia:
- loose connective tissue underlying skin
Deep fascia:
- dense connective tissue around muscle
SKM connective tissue
what are the 3 components of connective tissue and where are they found
Epimysium: surrounds whole muscle
Perimysium: surrounds bundles (fascicles) of muscle cells
Endomysium: separates individual muscle cells
myofibrils
what are myofibrils
long bundles of protein made up of thick and thin filaments
myofibrils
how are myofilaments arranged
- arranged in sarcomeres from one Z-disc to the next
the proteins of muscle
what 3 types of protein make up myofibrils and give 2 examples of each
- contractile proteins:
- myosin and actin
- Regulatory proteins that turn contraction on and off
- troponin and tropomyosin
- structural proteins which provide proper alignment, elasticty and extensibility:
- titin, myomesin, nebulin and dystrophin
Protein in muscles - Myosin
what are the thick filaments of myofibrils composed of
myosin
what do M line proteins do?
hold myosin filaments in place
proteins of the muscles - actin
what 3 things are the thin filaments of myofibrils made out of
- actin
- troponin
- tropomyosin
what holds thin filaments together
Z-lines
Does the length of filaments change?
No
nerve muscle anatomy
what specialized nerve cells are associated with muscles
motor neurons
excitation-contraction coupling
outline excitation contraction coupling
- action potential propagates down sarcolemma
- Transverse tubules conduct AP to cell’s interior
- Ca2+ release channels open in Sarcoplasmic reticulum, allowing for Ca2+ to enter the sarcoplasm
activation of muscle contraction by action potentials: OUTLINE the 3 steps
- action potenital induce release of Ca2+ into sarcoplasm
- Ca2+ binds to troponin C on thin filament, changing the troponin
- this shifts tropomyosin off myosin binding sites, enabling myosin to bind to actin
outline the 7 steps of cross-bridge cycling
this occurs after excitation-contraction coupling
- myosin head binds to actin forming cross bridge
- Pi is released from myosin head, causing conformational change in myosin
- power stroke occurs, where myosin head bends towards centre of sarcomere, sliding thin filaments towards the centre too.
- ADP is released
- New ATP molecule binds to myosin head, allowing for the head to release from actin
- ATP is hydrolysed, causing the myosin head to return to its original orientation
- this repeats, however the sarcomere’s length has shortened
contractile properties
what is “Twitch”
- single contraction and relaxation of a muscle in response to a single brief stimulus
contractile properties
what is henneman’s size principle
motor units are generally recruited in order of smallest to largest (or Fewest to most fibres) as contraction increases
what is the importance of normal resting length for skeletal muscles?
- it is the optimal resting length for generation of max tension
Sarcomere length at muscle’s optimal resting length?
~2.0 µm
if length of skeletal muscle is increased, why is tension reduced
- because overlap between thick and thin filaments decreases
if skeletal muscle length decreases, why does tension decrease?
because fluid pressure builds and thin filaments from either end of the sacromere collide.
types of mucles contraction
what is summation
when a muscle is stimulated multiple times in rapid succession so strength of contraction increases
types of muscle contraction
what is incomplete tetanus
muscles stimulated at high enough rate so that muscle does not fully relax between contractions
types of muscle contraction
what is complete tetanus
muscle stimulated at high frequency so that NO relaxation occurs (steady state of tension)
types of muscle contraction
give 1 in vitro example of complete tetanus and 1 in vivo example
In vitro:
- high rate of stimulation prevents muscle fibres from relaxing
In vivo:
- different motor units acitvated in rapid succession to generate sustained contraction
