Muscle Excitation and Contraction Flashcards
(36 cards)
What type of movement and contraction is associated with skeletal muscle?
- Rapid contractions
- Voluntary movement, facial expressions and manipulation of environments
What type of movement and contraction is associated with cardiac muscle?
- Medium speed contractions
- Involuntary
- As it contracts it propels blood into the circulation.
What type of movement and contraction is associated with smooth muscle?
- Slow wave like contractions
- Propels substances along internal passageways
- Involuntary
How are ions distributed across the membrane?
- There is uneven distribution of major ions in the intracellular and extracellular components.
- The body is in a state of electrical disequilibrium because active transport of ions across the cell membrane creates an electrical gradient.
What does an electrical gradient give us?
Excitability
What creates an electrical gradient?
The input of energy to transport ions across a membrane creates an electrical gradient.
What creates a chemical gradient?
The active transport positive ions out of the cell creates a chemical gradient.
What is an electrochemical gradient?
The combination of an electrical and chemical gradient is an electrochemical gradient
What is the resting membrane potential?
The resting membrane potential is the electrical gradient across the cell membrane.
What helps maintain the electrical gradient?
The Na/k pump
What is the significance of motor units?
They allow all muscle cells of an area to be controlled by one nerve cell.
eg 1:100 back muscles
1:10 finger muscle
1:1 eye muscle
What are myofibrils separated into?
Sacromeres
What structures are present in a sacromere?
- Thin actin filament
- Thick myosin filament
- Elastin (Titin)
- Z discs
What zones can a sacromere be separated into?
- I band (with no myosin)
- A band (myosin filament)
- H zone (part with no actin)
Which part of the sacromere structure facilitates for muscle shortening?
Elastin (titin filament), they are bound to the Z discs
How do myosin molecules get energy to act?
Head region has enzyme that uses ATP hydrolysis, this will confer the energy to movement.
How are myosin heads spread on the filament?
All around 360 degrees and they dont need to work in unison
What are tropomyosin and the trponin molecules used for?
- Tropomyosin blocks/inhibits myosin and actin reacting
- Troponin C is a calcium binding site.
- Troponin T takes shape change and amplifies it
- Troponin I pulls tropomyosin molecule away from groove, stopping inhibition.
When is the sacromere relaxed and what occurs in it at this point?
- When there is low levels of Ca
- Means Z lines are far apart
- Actin and myosin are not interacting
When is the sacromere partially contracted and what occurs in it at this point?
- When there is a bit of Ca
- Z lines are pulled toward centre of sacromere
- Actin and myosin not changing in length
When is the sacromere fully contracted and what occurs in it at this point?
- When there is more/alot of Ca
- Z lines hit off end of myosin molecules
- Actin can start to overlap in centre of sacromere
When a muscle length is shortened, which of the following sarcomere features would not shorten?
A zone (myosin filament)
What is the sarcolemma?
The sarcolemma is the plasma membrane of the muscle cell
What is the t-tubule?
The t-tubules are extensions of the sarcolemma and invaginate into the muscle fibre so that release of Ca from the SR reaches all myofibrils.
. Propagates action potentials into the interior of the muscle fibre
