CH11: The Muscular System Flashcards
Describe an insertion and origin point, and how they move
Origin: The attachment to the stationary bone. Can be seen as the start point of the muscle fibers
Insertion: The attachment to the moveable bone. Can be seen as where the muscle fibers 3
As a good rule of thumb, the origin is usually proximal, and the insertion is distal. The insertion is usually pulled toward the origin
Describe the components of a lever system
A lever is a rigid structure that can move around a fixed point called a fulcrum, F. A lever is acted on at two different points by two different forces, the effort, causing the movement, and the load, or resistance, which opposes movement.
Describe three different lever systems and give examples of them:
First class lever: First class levers have the fulcrum between the force and the load (EFL). A seesaw is an example of this. Mechanical advantage depends on whether the effort or load is closer to the fulcrum. The neck and jaw muscles are one examples
Second class lever: Load is between the effort (force) and the fulcrum (ELF). A wheelbarrow is an example of this. These produce the greatest amount of force, but sacrifice ROM. The heel and calf is one example
Third class lever: Levers in which the fulcrum is at one end and the force is applied in the middle and the weight is on the other end (FEL). These operate like a pair forceps, and are the most common levers in the body. They always have a mechanical disadvantage, but they favor speed and range of motion . The biceps and forearm are one example4
What are the different arrangements of fasculi with relation to the tendons?
Parallel: Muscle fascicles are arranged parallel to the longitudinal axis of muscle, ending parallel with tendon. Gives ROM
Pennate: Feather shaped fasculi that attach to tendons all over, as tendon extends nearly entire length of muscle. Can be unipennate, bipennate or multipennate. Gives good strength
Circular: Muscles fascicles arranged in concentric circles to form sphincter muscle that encloses an orifice (opening). Gives openings lol.
Fusiform: Muscle fascicles nearly parallel to longitudinal axis but taper off near tendons. Gives good ROM
Triangular: Muscle fibers are arranged in several directions with respect to one another and then converge onto the tendon. Gives good directionality
Differentiate between antagonist and prime mover
Agonist/prime mover contracts to cause action
Antagonist stretches/relaxes to act opposite to the muscle brining about action
What is the difference between a synergist and a fixator
A synergist is a muscle which aids in preventing unwanted movement in intermediate joints of a prime mover, to stabilize intermediate joints and aid the movement of the prime mover, while the fixator is more focused on efficiency, and acts to stabilize the origin of the
prime mover so that the prime mover can act more efficiently.
What makes muscles that control facial expression different
When these muscles contract, they move the skin rather than a joint
Give the function of the following muscles:
Zygomaticus major and minor:
Depresor anguli oris and depressor labii inferioris
Buccinator:
Orbicularis oris:
Mentallis
Zygomaticus major: Pulls mouth superolaterally, smiling
Zygomaticus minor: Exposes teeth
Depressor anguli oris: Opens mouth
Depressor labii inferioris: Lowers lower lips
Buccinator: Presses cheeks against teeth
Orbicularis Oris: Closes mouth
Mentalis: Pulls chin skin upwards
What pairs of muscles control eye movement and what two muscles open and close eyes
Three pairs of extraocular (meaning to originate outside the eyeball and insert into the sclera) control the movements of the eye
Superior recti: Elevation, medial movement and medial rotation
Inferior recti: Depression, medial movement and lateral rotation
Medial recti: Medial movement
Lateral recti: Lateral movement
Superior oblique: Depression, lateral movement and medial rotation
Inferior oblique: Elevation, lateral movement, lateral rotation
The levator palpebrae superioris opens the eye, and the orbicularis oculi closes the eyelids.
Which muscles close and open the eyelids
The levator palpebrae superioris moves the eyelids upwards to open the eyes and its antagonist, obicularis oculi, closes them (lowers eyelids).
Describe the muscles that are responsible for movement of the neck during swallowing and speech
The suprahyoid muscles elevate the hyoid bone, floor of the oral cavity, and tongue during swallowing (deglutition), this includes the digastric muscle, the stylohyoid and the geniohyoid muscle muscle
The digastric muscle elevates the hyoid bone and voice box during swallowing and speech
The stylohyoid muscle elevates and draws the hyoid bond posteriorly, thus elongating the oral cavity during swallowing
The geniohyoid muscle elevates and draws the hyoid bone anteriorly to shorten the floor of the oral cavity and to widen the throat to receive food bring swallowed
Most of the infrahyoid muscles depress the hyoid bone and some move the larynx during swallowing and speech. This includes the omohyoid, sternohyoid, sternothyroid and thyrohyoid muscles.
The omohyoid muscle depresses the hyoid bone
The sternohyoid depresses the hyoid bone
The sternothyroid depresses thyroid cartilage of larynx
The thyrohyoid elevates thyroid cartilage (Adam’s apple) of larynx and depresses the hyoid bone
Muscles of the neck that move the head
Contraction of two sternocleidomastoid (SCM) muscles act bilaterally to flex the cervical portion of the vertebral column and flex the head
Acting singly (unilaterally), each scm muscle laterally flexes and rotates the head to the opposite side of the contracting muscle
Bilateral contraction of the spinalis capitis, semispinalis capitis, splenius capitis and longissimus capitis muscles extend the head and vertebral column but their unilateral actions are quite different, involving primarily rotation of the head. Unilaterally:
The spinalis capitis extends the head and vertebra column unilaterally lol
The semispinalis capitis rotates head to side opposite of contracting muscle
The splenius capitis extends the head
The longissimus capitis laterally flexes and rotates head to same side as contracting muscle
Anterolateral abdominal wall muscles and their group functions
The anterolateral abdominal wall is composed skin, fascia, and four pairs of muscles ; internal oblique and external oblique, transversus abdominis and the rectus abdominis.
As a group, the muscles of the anterolateral abdominal wall help contain and protect the abdominal viscera; flex, laterally flex, and rotate the vertebral column (backbone) at the intervertebral joints; compress the abdomen during forced exhalation; and produce the force required for defecation, urination, and childbirth.
Anterolateral muscles acting singly
The external abdominal oblique is the superficial muscle which laterally flexes the vertebral column, especially the lumbar portion, and rotates the vertebral column
The internal abdominal oblique is the intermediate flat muscle which also laterally flexes the vertebral column, especially the lumbar portion, and rotates the vertebral column
The transversus abdominis is the deep muscle with mst of its muscle fascicles directed transversely around the abdominal wall. It compresses the abdomen
The rectus abdominis is a long muscle extending the entire length of the anterior abdominal wall, originating at the pubic crest. Flexes pelvis on vertebral column
Which are the muscles that move the pectoral girdle
The muscles of the thorax that move the pectoral girdle are divided into two groups:
Anterior thoracic muscles: which include pectoralis, subclavius and pectoralis minor
Posterior thoracic muscles: include trapezius, rhomboid major and minor and levator scapulae
