Muscles Flashcards
Types of muscles, control of heart rate, contraction, neuromuscular junction, muscle fibres etc.
What are the three types of muscle tissue in mammals?
skeletal muscle, cardiac muscle and involuntary/smooth muscle
What are skeletal muscles attached to the skeleton by?
tendons
What is skeletal muscle used for?
used in conscious or voluntary movement
What does skeletal muscle consist of?
fibres
What are the fibres in skeletal muscle shaped like?
long tubes
What does each fibre in skeletal muscle contain?
a number of nuclei
What is the appearance of skeletal muscle fibres?
the fibres have a striped or striated appearance and are arranged in a regular pattern
During contraction what happens to skeletal muscle fibres?
all the fibres contract in the same direction
Can skeletal muscle fibres contract rapidly?
Yes
Do skeletal muscle fibres stay contracted for a long period of time?
No
Where is cardiac muscle found?
found only in the heart
Is cardiac muscle under voluntary or involuntary control?
involuntary control
What type of muscle cells are branched?
cardiac muscle cells
What feature allows cardiac muscle cells to contract together?
cardiac muscle cells are connected to each other at the ends
Usually, how many nuclei does each cardiac muscle cell have?
only one nucleus
Cardiac muscle cell form fibres with a what appearance?
striped or striated appearance
What is the difference between the striations in cardiac muscle than in skeletal muscle?
cardiac muscle fibres’ striations are fainter than in skeletal muscles
Cardiac muscle cells contract without the need for a what? And what is this called?
without a nervous signal and scientists say that they are myogenic
Where is involuntary/smooth muscle found?
all over the body
What is peristalsis?
Where involuntary muscle in the walls of the intestines contracts to move digested material along the digestive system
What type of muscle is found in the walls of blood vessels?
involuntary/smooth muscle
Is involuntary muscle striated?
No
Is involuntary muscle under voluntary control?
no
How many nuclei do involuntary muscle cells usually have?
a single nucleus per cell
Is smooth/involuntary muscle arranged regularly?
No - not as regular as cardiac or skeletal muscle
Do involuntary muscle cells contract in the same direction?
involuntary muscle cells do not all contract in the same direction
Does involuntary muscle contract rapidly or slowly? And does involuntary muscle contract for a long or short period of time?
unlike skeletal and cardiac muscle, involuntary muscle contracts slowly but can contract for a relatively long time
What is the sarcoplasm?
the cytoplasm of the muscle cell is called the sarcoplasm
What is the sarcolemma?
the cell membrane of the muscle cell is called the sarcolemma. The sarcolemma folds up on itself to form transverse tubules - these help to transmit electrical impulses very quickly through the whole muscle fibre.
What is the sarcoplasmic reticulum?
The endoplasmic reticulum of the muscle cell is called the sarcoplasmic reticulum. It forms a network of internal membranes that store calcium ions to aid muscle contraction.
Muscle contraction works via what model?
the sliding filament model
What are the two proteins called that skeletal muscle fibres contain?
actin and myosin
What kind of filaments does myosin form?
thick filaments
What kind of filaments does actin form?
actin forms thin filaments
What happens when an action potential arrives at the motor neurone?
acetylcholine is released from the presynaptic knob
What does the acetylcholine trigger in a neuromuscular junction?
the acetylcholine triggers the sarcolemma of the muscle fibre to depolarise
What happens when the sarcolemma of the muscle fibre has depolarised?
this depolarisation triggers Ca2+ to be released from the sarcoplasmic reticulum
What does an increased concentration of Ca2+ released from the sarcoplasmic reticulum cause?
triggers the actin and myosin filaments to slide together
What is the structure of myosin?
Firstly, myosin has a long fibrous tail structure. These myosin tails are clustered together, forming the filament. Secondly, each myosin molecule has a globular head group. The myosin head groups point outwards. Each myosin head group has a binding site for actin and a binding site for ATP.
What is the structure of an actin filament?
Actin forms two strands wrapped together into a helical structure. Running along the actin filament we have binding sites for myosin. These are called actin-myosin binding sites. However, in an uncontracted muscle, these actin-myosin binding sites are blocked by a threadlike protein called tropomyosin. Tropomyosin is held in position by troponin.
How is muscle contraction triggered?
when Ca2+ are released from the sarcoplasmic reticulum
Where does the Ca2+ ions bind to trigger muscle contraction?
the Ca2+ bind to the troponin molecules
Ca2+ binding to the troponin molecules causes what to happen?
the troponin molecules to change shape, moving the tropomyosin away from the actin-myosin binding sites
Once the actin-myosin binding sites are exposed, what happens?
the myosin head groups can now bind to the actin-myosin binding sites (this is called an actin-myosin cross-bridge)
Once an actin-myosin cross-bridge has been formed, what happens?
the myosin head flexes (changes its angle) which pulls the actin filament along
What happens at the same time as the actin filament being pulled along be the myosin head?
the ADP molecule is released from the myosin head
After the ADP molecules has been released from the myosin head, what happens?
a molecule of ATP attaches to the myosin head
A molecule of ATP attaching to the myosin head causes what to happen?
the myosin head to detach from the actin-myosin binding site. Now the myosin head acts as an ATPase hydrolysing the ATP molecule to ADP and phosphate
What is the ATPase activity activated by?
the high concentration of Ca2+ in the sarcoplasm
What happens to the energy from ATP hydrolysis?
it is used to return the myosin head to its original angle
