Muscle Contraction Flashcards
Give 3 advantages of the cell signalling mechanism
Transfers signal from inside to outside cell
Converts signal into something cell can understand
Amplifies signal
Allows diversification of response
Modulate signals
What can pass through gap junctions?
Electrical currents
Chemical signals work__________________
Via second messengers
An exception to the chemical signals rule is? Why?
Steroid hormones
Hydrophobic so can pass through the plasma membrane
Cells next door to each other with the signal coming from one and the receptor in the other
Juxtacrine transmission
Very slow, specific, local effect
Endocrine transmission
Secrete hormones to blood
Travel to target receptor
Widespread
Slow but can be fast (eg adrenaline)
Nitric oxide is an example of a
Signalling molecule that uses paracrine transmission
Secreted into extracellular fluid
Local effects
Autocrine transmission
Cell secrets signalling molecule and these bind to receptors in the outside of the same cell
Transverse tubules
Invaginations of the plasma membrane
Describe the troponin-tropomyosin complex
Troponin I: inhibitory subunit
Troponin C: calcium binding site
Troponin T: tropomyosin binding site
During contraction there is a ________ is sarcomere length by reduction of the _____ and ____ bands. There is no change in the width of the ______ band.
Decrease
H
I
A
Myasthenia gravis
Autoimmune disorder in which the body produces antibodies against the nicotinic receptor
The nicotinic receptor is a _______ protein. It has ________ with a _____ binding site, _______, _______, ________ subunits. All subunits have _____ transmembrane domains.
____ helices are ________ and form the wall. Other helices mainly_______. The ends of the channels have rings of __________________. ___________ and _________ form a selectivity filter against ______ ions.
Pentomeric 2 alpha subunits Ach Beta Gamma Delta 4 M2 Amphipathic Hydrophobic Negatively charged amino acids Glutamate Aspartate Negative
Ach binding causes rapid ________. At the centre of the receptor is a ring of _________________ keeping it closed. Ach induces _________ moving ____________ away, replacing them with __________ and opening the channel.
Influx of sodium Bulky hydrophobic leucine residues Rotation in the M2 subunits Leucine residues Polar residues
Calcium release in contraction
Every second RyR linked to cytoplasmic loop of DHPR, forming a bridge between the T tubules and terminal cisternae of SR.
DHPRs detect plasma membrane depolarisation and transmit conformational change to RyR causing the channel to open and release Ca2+ from the stores
Excitation contraction coupling
