Skeletal Muscle Flashcards
What is fasciculations?
These are small involuntary muscle movements from muscle contraction and relaxation which are visible under the skin.
Describe the structure of a circular muscle.
These have concentric fibres and act as sphincters, to adjust the size of an opening.
What are the different types of parallel muscle?
Fan shaped: close together at one end and a wider spread at the other
Strap: shaped like a strap
Fusiform: wider and cylindrical in the middle and taper off at the ends.
What are the different types of muscle?
Circular, parallel and penate.
What are the different types of penate muscle?
Unipennate: fasicles attach to same side of tendon
Bipennate: fasicles attach to both sides of a central tendon
Multi penate: central tendon branches and fasicles attach to this
What is a pennate muscle?
This is a muscle which has one or more aponeurosis running through the tissue from the tendon, leading to fasicles being present.
How are origin and insertion defined in muscles?
The origin is the area with the larger mass and the insertion is on the structure which is moved by the muscle.
What is compartment syndrome?
In the limbs, the muscles are split into compartments which are surrounded by tough fascia. If there is bleeding in a compartment then this leads to a build up of pressure which causes pain on rest.
What is the treatment for compartment syndrome?
Fasciotomy
In terms of muscle movements, what is an agonist?
This is the prime mover of a muscle
What is an antagonist in terms of muscle movement?
These oppose the agonists (prime movers) but are necessary for fine motor control to be possible.
What is a synergist?
This is a muscle which assists the agonist in the movement, however alone is unable to perform the movement.
What is the role of neutralisers in muscle movements?
These remove unwanted affects caused by the agonist.
What function of muscle movement do fixators have?
These hold a body part still whilst another is moving.
What is isotonic muscle contraction?
This is where tension in the muscle remains constant but length varies.
What is the difference between concentric and eccentric muscle contraction?
Concentric is where the muscle shortens whilst eccentric is where the muscle is exerting a force whilst extended
Give an example of eccentric muscle contraction
Walking downhill
Give an example of isometric muscle contraction
Hand grip
What is isometric muscle contraction?
This is where tension varies in a muscle but muscle length remains constant.
What is the distribution on a first class level?
In this case, the fulcrum is central with load and effort at opposite ends.
Where is load found in a second class lever?
Load is in the middle of the lever and the fulcrum is at one end.
What is the class of lever in which effort is acting in the middle with load at one end and the fulcrum at the other?
Third class lever
What is a motor unit?
This is a motor neurone and the muscle fibres it innervates
What can be said about all the muscle fibres in a motor unit?
They will all have the same contractile type (fast/slow)
What is a muscle spindle?
This is a structure innervated by two sensory and one motor neurone. The motor neurone keeps the muscle taught whilst the sensory fibres relay rate of change of muscle length.
Where on the muscle is the muscle spindle found?
It is walled off from the rest of the muscle by a collagen sheath.
What condition can cause platings to struggle to perform accurate movement in the absence of vision?
Large-fibre sensory neuropathy
State two things which control muscle contraction force:
Size principle: small motor neurones will be recruited first and this means it starts with the slow type fibres and progresses to the faster fibres
Rate code: multiple action potentials sum up to increase force of contraction.
What is the limit of summation of action potentials in skeletal muscle called?
Tetanus
What is muscle tone?
This is stiffness and tension retained by muscle and controlled by motor control centres in the brain.
What is hypotonia?
This is lack of muscular tone.
Describe the process which occurs at a Neuromuscular junction
The action potential causes voltage gated calcium channels to open and calcium influx. This causes release of acetylcholine containing vesicles which cross the synaptic cleft and hint to nicotinic acetylcholine receptors. This opens sodium channels and this depolarises membrane and so calcium channels open. Calcium flows into the cell and binds to troponin, causing conformational change and allowing myosin heads to bind to actin molecule.
What facilitates muscle relaxation?
Calcium is pumped back into the sarcoplasmic recticulum by SERCA.
What enzyme is responsible for the breakdown of acetylcholine in the synaptic cleft?
Acetylcholineesterase
What ion channel is important for repolarisation after the action potential?
Cl-
What is myotonia?
This is a condition where you cannot relax muscles at your own will due to ion channelopathies.
What ion channel mutation is common for causing myotonia congenita?
Cl-
What is the difference between most excitable cells and skeletal muscle?
Most return to their resting membrane potential by the action of K+ however in skeletal muscle Cl- has a major role in repolarisation.
