Muscle Flashcards
What are the types of muscle
Skeletal
Cardiac
Smooth
What is the function of muscle?
To allow movement by contraction
What do antagonist muscle pairs consist of?
Flexors and extensors
What are the two types of contraction and how do they differ?
Isometric - same size, tension develops
Isotonic - same tension, lengthens
How is muscle arranged?
Sarcomere - Myofibril - Bundles to form MYOFIBRE
Then muscle
What is excitation-contraction coupling?
The process by which an action potential causes contraction of muscle by letting Ca2+ be released
How does ec coupling work?
AP propagates along sarcolemma and T-tubules - membrane inv aginations contacting EF
Depolarisation cauess dihydropyridine receptors (DHPR) to change - conformation
This change is transmitted to RyR on the SR
RyR open, Ca2+ then release from IC store
What forms the sarcomere?
Actin - thin, 2 alpha helices
Myosin - thick motor, globular heads
Titin - spring filaments - anchor myosin to sarcomere
Nebulin - large filaments assoc. w actin
Tropomysoin - bound to actin - covers and prevets crossbridge formation
CapZ and Tropomodulin - assoc w + and - ends of actin
Descirbe the process of contraction
Ca2+ released, troponin moves from tropomyosin
Myosin binding site on actin now exposed
Charged myosin head binds to said site
This binding and discharge of ADP causes head to pivot - power stroke and actin comes to sarcomere centre
ATP binds, causing mysoin head to release
ATP hydrolysis provides energy for head to go back to normal
How does contraction work in isometric muscles
Firstly, isotonic, the tension > force by load so it shorten
Isometric, load = tension so it doesnt shorten but myosin still binds, atp is used for it to be recharged
What are the types of cell in the heart?
Cardiomyocytes - muscle
Pacemaker cells
- SA and AVN - spindle shaped
Conducting fibres
- conducting cells - bundle of His and Purkinje
Where is cardiac muscle located and how does structure compare?
Walls
Has intercalated disks
- Special regions connectring cells
- Has many gap junctions for AP propagation
Same sarcomeres
Describe E-C coupling in cardiomyocytes
Same as skeletal but instead of DHPR, there are VGCCs
The Ca2+ released causes RyR to release Ca2+ from internal SR - Ca induced Ca release
Also, intiate contraction by binding to troponin
And depolarise further
How do smooth muscle differ to straited muscle?
No regular actin myosin arrangement
Smooth
Describe E-C in smooth muscle
Depolarisation opens VGSSc
Ca-CaM complex activates myosin light chain kinase
MLCK phosphorylates light chains
These light chains of myosin interact w actin - contract
