Muscles Flashcards
How can muscles be classified depending on their action?
- *Agonists** = muscles that contract to perform a certain action
- *Antagonist** = Muscles which oppose prime movers = relax and lengthen progressively allowing agonists to move. Therefore the movement is controlled but not impeded. (Gluteus maximus is antagonist for iliopsoas)
Fixator = Muscle that acts as a stabilizer of one part of the body during movement of another part (rotator cuff muscles)
Synergist = Synergists are muscles that work together in close cooperation as they either contract or relax to modify the action of the agonist (provides stabilisation for the joint that moves)
What are agonists split into?
- *Prime movers** = major contribution in any contraction
e. g iliopsoasas in hip flexion movement - *Secondary movers** = Muscles which cross the same joint but make less contribution in the movement
e. g sartorius in hip flexion
What is the prime mover and secondary mover in hip flexion?
Prime Mover = Muscles which make major contribution
- Iliopsoas (made up of psoas major and iliacus)
Secondary Mover= Make less contribution in movement, can act as prime when more force is required or paralysis
- Sartorius
List the ways in which muscles be classified depending on their morphology?
- Unipennate
- Bipennate
- Multipennate
- Strap
- Fusiform
- Circular
- Convergent
- Parallel
Explain unipennate muscles and give an example
Muscles have their fibres aranged to insert in a diagonal direction (obliquely) onto the tendon = allows greater strength
example: Extensor digitorum longus
Extension of the toes and dorsiflexion
Explain bipennate muscles and give an example
BIPENNATE: muscles consist of two rows of oblique muscle fibres, facing in opposite diagonal directions, converging on a central tendon.
Bipennate muscle are stronger than both unipennate muscle and fusiform muscle, due to a larger physiological cross-sectional area
An example is rectus femoris (straight femur) and makes up the quadriceps
Explain multipennate muscles and give an example
a muscle with several central tendons toward which the muscle fibers converge like the barbs of feathers.
Example: deltoid muscle, assists with glenohumeral elevation
Explain fusiform muscles and give an example
- These muscles are more spindle shaped, with the muscle belly being wider than the origin and insertion.
- Sometimes included in the parallel muscle group,
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Examples
- Biceps Brachii (flexes and supinates the forearm)
- Psoas major (flexion and rotation of the hip joint) forms iliopsoas
Explain circular muscles and give an example
These muscles appear circular in shape and are normally sphincter muscles which surround an opening such as the mouth,
- Obicularis Oris (mouth)
- Obicularis Oculi (eyes)
Explain convergent muscles and give an example
- These are muscles where the origin (the attachment to a fixed bone, usually the proximal attachment) is wider than the point of insertion.
- This fibre arrangement allows for maximum force production.
- Convergent muscles are also sometimes known as triangular muscles.
An example is Pectoralis Major. flexion, adduction and internal rotation of the humerus
Explain what strap muscles are and give their function
(also known as parallel muscle)
- Have fibres which run parallel to each other.
- They are normally long muscles which cause large movements, are not very strong but have good endurance.
Example:
Sartorius (rotation and flexion of the hip and knee)
Sternocleidomastoid (rotation of head and flexion of the neck, innervated by accesory nerve)
What is the definition of a muscle?
Body tissue consisting of long cells which contract when stimulated and produce motion
Tendon
a tough cord or band of dense white fibrous connective tissue that unites a muscle with some other part (such as a bone) and transmits the force which the muscle exerts.
Aponeurosis
Broad flat sheet of connective tissue which replaces tendons in flat muscles
What is the smallest muscle in the body?
What is its function?
Recap identify the ossicles
Stapedius
Function is to staballise the stapes (the smallest bone in the body)
Ossicles are 1) Incus, 2) Malleus 3) Stapes (pushes against oval window)
What does origin and insertion mean?
Origin = proximal end which remains fixed during contraction
Insertion = the distal end of the muscle that is moveable
Identify the muscle and which joints move when it contracts
Tibialis Anterior
- Arises from the lateral condyle
- Most medial muscle in the anterior compartment of the leg
Involved in
- dorsal flexion of the ankle,
- inversion of the foot,
- adduction of the foot,
- contributor of maintaining the medial arch of the foot
Identify the muscle and which joint moves when it contracts
Rectus Femoris
- One of the four quadriceps
- Others are vastus medialis, the vastus intermedius, and the vastus lateralis
- All four quadricep muscles attach to the patella (sesamoid bone) via the quadriceps tendon
Joint Movements
- Hip flexion with iliopsoas
- Knee extension with other quadricep femoris muscles
Identify this muscle and joint movements
What tendon is associated with this muscle?
Gastrocnemius (calf muscle)
- located with the soleus in the posterior (back) compartment of the leg.
- The lateral head originates from the lateral condyle of the femur, while the medial head originates from the medial condyle of the femur.
- Its other end forms a common tendon with the soleus muscle; this tendon is known as the calcaneal tendon or Achilles tendon and inserts onto the posterior surface of the calcaneus, or heel bone.
Joint Movements
- plantar flexing the foot at the ankle joint
- flexing the leg at the knee joint.
Identify this muscle and its function
Biceps Brachii
- flexes the forearm
- supinates the forearm.
Identify the muscle and its joint movement
Bicep Femoris (two heads)
- is a muscle of the thigh located to the posterior, or back.
- Has a long head and a short head
- arises from the posterior part of the tuberosity of the ischium
- Forms part of the hamstrings muscle group
Joint movement
- Both heads of the biceps femoris perform knee flexion.
- Since the long head originates in the pelvis it is also involved in hip extension
Identify this muscle and its joint movement
Triceps Brachii
- It helps in extension of the elbow joint and also act as an antagonist of the biceps and brachialis.
- The triceps brachii also helps to stabilize the shoulder by keeping the head of the humerus in its correct position in the shoulder joint.
Identify the overall muscle and the individual muscles and identify its function
Quadriceps Femoris
- RECTUS FEMORIS
- VASTUS MEDIALIS
- VASTUS INTERMEDIUS (Under rectus femoris)
- VASTUS LATERALIS
- All four quadriceps are powerful extensors of the knee joint.
- They are crucial in walking, running, jumping and squatting.
- Because the rectus femoris attaches to the ilium, it is also a flexor of the hip.
Identify these muscles
What is the main nerve in this region?
- Gluteus maximus, Gluteus medius, Gluteus minimus
- Main extensor muscle of the hip
- Sciatic nerve
From what regions does the spinal nerve arise from?
What does it contain divisions from?
- Derived from spinal nerves L4-S3
- Contains fibers from both the anterior and posterior divisions of the lumbosacral plexus.
What is sciatica?
Occurs when the sciatic nerve becomes irritated or impinged
Results in
- Tingling in lower limb
- Stabbing shooting pain
- Numbness
Describe muscle compartments
- Muscle compartments are surrounded by a sleeve of deep fascia;
- Each compartment usually has its own nerve and blood supply;
- venous return is aided by the pressure from the connective tissue sleeve when the muscles contract.
- Muscles in a compartment usually work together to produce movement.
What is compartment syndrome?
Trauma to the leg can produce haemorrhage or inflammation
Because the fascia surrounding the compartment is strong, swelling causes an increase in pressure within the compartment
- This can cause compression
- Distal structures can become ischaemic
Identify these muscles
Frontalis and Temporalis
What bony structure do the hamstring muscles originate from?
Where do the hamstrings insert?
- Ischial tuberosity
- Head of fibula
What are the muscles of the hamstrings?
- Bicep Femoris
- Semimembranosus
- Semitendinosus
What does flexion and extension mean?
Flexion: A movement by which the angle of a joint is decreased
Extension: A movement by which the angle of a joint is increased
What does adduction and abduction mean?
Abduction = movement of limb away from the midline
Adduction = movement of limb towards the midline
- e.g moving little toe outward (abduction) moving it back (adduction)
- e.g moving finger away from the plane of the hand, adduction is adding the finger back to the plane of the hand
