Muscular System Flashcards
What are muscle cells?
They are specialised contractile cells organised into tissues
What are the four functions of muscles?
To move body parts
To temporarily alter the shape of internal organs
To provide static support, which means that they are involved in keeping our bodies upright
To produce heat
What are the three types of muscles?
Skeletal
Cardiac
Smooth
What is skeletal muscle?
Muscle attached to the skeleton
What is the function of skeletal muscle?
To move bones and other structures, such as the eyes
What type of movement does skeletal muscle control - voluntary or involuntary?
Voluntary
Describe the structure of skeletal muscle
They have a fleshy contractile portion, which is composed of skeletal striated muscle
They have a non-contractile portion, which is mainly composed of collagen bundles
What are the two ways in which the collagen bundles in skeletal muscle can be arranged?
Rounded - tendon
Flat sheets - aponeuroses
What is the role of the collagen bundles in skeletal muscle?
To directly or indirectly attach muscles to bones, cartilages, ligaments, etc
What are tendons?
Flexible structures formed from a cord of strong fibrous collagen tissue
Why are tendons very strong structures that can resist tension?
They are formed from collagen tissue, which is very dense.
What are the two roles of tendons?
To connect muscle to bone
They are also involved in altering force direction
Can muscles share the same tendon?
Yes
What is the difference between ligaments and tendons?
Ligament’s bind bone to bone
Tendons bind muscle to bone
What is the epimysium?
This is a sheath of fibrous elastic tissue which surrounds the muscle, i.e. all the fascicles
What is the endomysium?
This is a thin layer of connective tissue that ensheaths each individual myocyte
What two things are contained within the endomysium?
Capillaries
Nerves
What is a fascicle?
This is a bundle of muscle fibres. There are multiple fascicles that make up skeletal muscle
What is the perimysium?
This is the sheath of connective tissue surrounding a fascicle
What are pennate muscles?
They are feather-in like arrangement of their fascicles
What are the three types of pennate muscles?
Unipennate
Bipennate
Multipennate
What are unipennate muscles?
Muscles that have a central tendon and muscle fibres connecting at an angle, but only on one side
What are bipennate muscles?
Muscles that have a central tendon and have muscle fibres connecting at an angle at both sides
What are multipennate muscles?
Muscles that have a central tendon have muscle fibres branching off
What are fusiform muscles?
They are spindle-shaped in their arrangement.
This means that there is a central belly of muscle fibres and two tendons attached to either side of this. The muscle belly fibres are arranged parallel to one another.
What are parallel muscles?
In parallel muscles, the fascicles run parallel to one another
What are convergent muscles?
They have a broad attachment from which the fascicles converge to a simple tendon
What are circular/sphincter muscles?
They surround a body orifice, constricting it when contracted
What are the two muscle types which are able to form sphincter muscles?
Smooth
Skeletal
What is the role of sphincter muscles?
To control the flow of fluids
Where are smooth, sphincter muscles found?
Within the body
Where are skeletal, sphincter muscles found?
Outside the body
What are the two types of skeletal, sphincter muscles?
External anal sphincter
External urethral sphincter
What are digastric muscles?
They feature two bellies in a series, sharing a common intermediate tendon
What are axial muscles?
Axial muscles are attached to the axial skeleton
What is the axial skeleton?
It is comprised of the bones situated in the long axis of the body in the anatomical position
What muscles generally make up the axial skeleton?
Muscles attaching only to the trunk
What are appendicular muscles?
Muscles which are attached to the appendicular skeleton
What is the appendicular skeleton?
It is comprised of bones that are appended to the axial skeleton
These muscles are also referred to as limbs
What muscles generally make up the appendicular skeleton?
Muscles attaching from the trunk to limb bones
Muscles attaching from limb to limb bones
What is the difference between axial and appendicular muscles, apart from which skeleton that they attach to?
Nerve supply
How are axial muscles supplied with nerves?
Segmentally by separate nerves, which have not mixed with others
How are appendicular muscles supplied with nerves?
Nerve plexuses, which are branching networks of intersecting nerves
What law do innervation of both axial and appendicular muscles follow?
Hilton’s Law
What does Hilton’s Law state?
The nerve supplying the muscles acting across a given joint, will also innervate the joint and the overlying skin
Where in the bone do tendons specifically attach to? Why?
The periosteum
This anchors the tendon strongly and spreads the force of contraction, so that the tendon won’t tear away easily
What two terms do we use to describe the attachment of a tendon to a bone?
Origin
Insertion
What other names are used to refer to the origin attachment?
Superior
Proximal
Medial
What is the origin attachment?
The attachment site which is closer to the body compared to the insertion attachment
What other names are used to refer to the insertion attachment?
Inferior
Distal
Lateral
What is the insertion attachment?
The attachment site which is further away from the body, compared to the origin attachment
Which attachment remains fixed during contraction?
Origin
Which attachment is movable during contraction?
Insertion
What is the shape of the anterior tendons in the abdomen?
Flat
Thin
Broad
What is the name given to the anterior tendons in the abdomen?
Aponeurosis
Why are anterior tendons in the abdomen flat, thin and broad?
To protect organs
To allow greater movement and compression
What is the structural unit of a muscle?
A muscle fibre
What is the other name for the functional unit of a muscle?
Motor unit
What is a motor unit?
It consists of a motor neurone and the muscle fibre it controls
What happens when a motor neurone in the spinal cord is stimulated?
It initiates an impulse that cause all the muscle fibres supplied by the motor neurone to contract simultaneously
What are large motor units?
When one neurone supplies several hundred muscle fibres
Which two places are large motor units found?
Large trunk
Thigh muscles
What are small motor units?
When one neurone supplies a few muscle fibres
Which two places are small motor units found?
Eye
Hand
What is the role of small motor units?
To allow precise movements to be made
What do skeletal muscles cross? What does this allow them to do?
Joints
Exert action onto that joint
How many bones is the biceps brachii attached to? What are they?
Three
The scapula, the radius and the ulnar
What is the origin attachment of the biceps brachii?
Scapula
What is the insertion attachment of the biceps brachii?
Radius
Ulnar
How many joints does the biceps brachii cross? What are they?
Three
The shoulder joint, the elbow joint, the superior radio-ulnar joint
What is the superior radio-ulnar joint?
This is the joint between the radius and the ulnar bone
How many bones is the pectoralis major attached to? What are they?
Three bones
The humerus, the sternum and the clavicle
What is the origin attachment of the pectoralis major?
The clavicle
The sternum
What is the insertion attachment of the pectoralis major?
The humerus
How many joints does the pectoralis major cross? What are they?
One joint
The shoulder joint
How many bones is the brachioradialis attached to? What are they?
Two bones
What is the origin attachment of the brachioradialis?
The humerus
What is the insertion attachment of the brachioradialis?
The radius
How many joints does the brachioradialis cross? What are they?
One
The elbow joint
How many heads make up the triceps brachii?
Three
What are the three heads of the triceps brachii called?
Long
Lateral
Medial
What is the origin attachment of the long head of the triceps brachii?
Scapula
What is the insertion attachment of the long head of the triceps brachii?
Ulna
What is the origin attachment of the lateral head of the triceps brachii?
Humerus
What is the insertion attachment of the lateral head of the triceps brachii?
Ulna
What is the origin attachment of the medial head of the triceps brachii?
Humerus
What is the insertion attachment of the medial head of the triceps brachii?
Ulna
How many bones is the triceps brachii attached to? What are they?
Three
The scapula, the humerus and the ulna
How many joints does the triceps brachii cross? What are they?
Two
The shoulder joint, the elbow joint
What is the primary action of the triceps brachii?
Extension of the elbow
How do muscles pull bones together? What is this also referred to as? How do muscles do this?
By shortening the joint
Flexion of the joint
By lengthening themselves
How do muscles pull bones apart? What is this also referred to as? How do muscles do this?
By extending the joint
Extension of the joint
By contracting
Do muscles that cross two joints perform the same action at both joints?
No
What muscle allows flexion, extension and abduction of a joint? Why is this unusual?
Deltoid
Most muscles are involved in either flexion or extension of a bone, not both
Why is the deltoid muscle able to carry out flexion, extension and abduction of the shoulder joint?
Its convergent shape, as this means it has anterior, middle and posterior fibres that perform different actions on the shoulder
What movement does anterior fibres of the deltoid muscle carry out?
Flexion
What movement does posterior fibres of the deltoid muscle carry out?
Extension
What movement does middle fibres of the deltoid muscle carry out?
Abduction
What are diaphragms?
Skeletal muscles which attach to bones on either side of the midline of the body
Where is the tendon of a diaphragm situated?
In the centre
How many diaphragms are there in the body?
Four
What is the largest diaphragm in the body?
The thoracic diaphragm
What does the thoracic diaphragm separate?
The thorax from the abdomen
What is the role of the thoracic diaphragm?
To increase the volume of the thoracic cavity during inspiration and decreasing it during expiration
What movement occurs in the thoracic diaphragm during contraction?
Descending
What movement occurs in the thoracic diaphragm during relaxation?
Ascending
Which skeletal muscles have a function of static support, rather than moving bones?
Erector spinae muscles
What is an antagonistic pair of muscles?
A pair of muscles, which are situated around a joint which combine in an antagonistic way
What happens to the antagonist when the agonist contracts?
It relaxes, creating a smooth movement
What is another name for an agonist?
Prime mover
What is an agonist?
The main muscle responsible for producing a specific movement of the body
What is an antagonist?
A muscle that opposes the action of an agonist
What is a synergist?
They help perform the same set of joint motion as the agonist
How does a synergist work?
They stabilise muscle movements
They control movement t so that it falls within a range of motion which is safe and desired
What is a fixator?
A muscle which stabilises the joint to which they are attached so that the joint can move efficiently without risk of dislocation
How does a fixator work?
Steadying the proximal parts of a limb while movements are occurring in the distal parts
Where are the majority of fixators found within the body?
Hip joints
Shoulder joints
Name a fixator muscle within the body
Rotator cuff muscles
What joint does the rotator cuff muscles stabilise?
Shoulder
Why are the rotator cuff muscles needed in the shoulder?
The shoulder joint is the least stable and the most frequently dislocated
How are the tendons in the rotator cuff muscles arranged?
They surround the shoulder joint, thus forming a tendinous cuff
What membrane separates muscles into compartments?
The deep fascial intermuscular septa
Where does the deep fascial intermuscular septum extend from in the arm? Where does it extend into?
The periosteum of the bone
The deep fascia of muscle
What are the two muscle compartments in the arm?
Anterior (flexor)
Posterior (extensor)
What are the two muscle compartments in the forearm?
Anterior (flexor-pronator)
Posterior (extensor-supinator)
What are the three muscle compartment of the lower limbs?
Anterior
Posterior
Medial
What is compartment syndrome?
Inflammation within a muscle compartment
What are the two causes of compartment syndrome?
Injury
Surgery
How are muscles in the arm and forearm supplied with nerves?
Individual nerves from the brachial plexus
How are muscles in the thigh and leg supplied with nerves?
Individual nerves from the lumbosacral plexus
Where does the brachial plexus originate?
In the cervical region, specifically spinal roots C5-T1
What happens to the upper limb muscles, if there are injuries to nerves arising from the brachial plexus?
Paralysis
Distinctive positional deformities of the wrist and hand
Where does the lumbosacral plexus originate?
In the posterior section of the abdomen and pelvis, specifically spinal nerve roots L1-S4
What happens to the lower limb muscles, if there are injuries to nerves arising from the lumbosacral plexus?
Paralysis
Distinctive positional deformities of the ankle and foot
What are the six factors which muscle names can be based?
Direction of muscle fibres
Attachments
Size
Number of heads
Shape
Function
What does rectus mean?
Parallel
What does transverse mean?
Perpendicular
What does oblique mean?
At a 45 degree angle
What muscles are named based upon the direction of their muscle fibres?
Abdominal
What bones does the sternocleidomastoid muscle attach to inferiorly? Which bones does it attach to superiorly?
Sternum and the clavicle
Mastoid
What does maximus mean?
Largest
What does longus mean?
Longest
What does brevus mean?
Shortest
What does major mean?
Larger of a pair
What does minor mean?
Smaller of a pair
What does biceps mean?
Two heads
What does triceps mean?
Three heads
What does quadriceps mean?
Four heads
What does deltoid mean?
Triangular
What does trapezius mean?
Trapezium
What does teres mean?
Triangular
What does serratus mean?
Saw-tooth edge
What does orbicularis mean?
Circular
What does extensor mean?
Extension
What does abductor mean?
Abduction
What does flexor mean?
Flexion
What does adductor mean?
Adduction
What does pronator mean?
Pronation
What does supinator mean?
Supination
What cross-sectional imaging technique the best for muscles? Why?
MRI
The imaging of soft-tissue structures of the body, such as muscles, are often clearer and more detailed when compared to other imaging methods
What colour do muscles appear on scans?
Grey
What two muscles are attached to the sternum on a scan?
Pectoralis major
Pectoralis minor
Which muscle lies anteriorly and is attached to the sternum on a CT scan?
Pectoralis major
Which muscle lies posteriorly and is attached to the sternum on a CT scan?
Pectoralis minor
Where is cardiac muscle found?
Muscular wall of the heart, which is the myocardium
Walls of the aorta, pulmonary vein and superior vena cava
What is the function of cardiac muscle?
To allow contraction fo the heart and great vessels, allowing blood circualtion
What type of movement does cardiac muscle control - voluntary or involuntary?
Involuntary
What stimulates contraction of cardiac muscle?
Pacemaker nodes composed of specialised cardiac muscle fibres
What controls the contraction rate of cardiac muscle?
The ANS
How is contractile stimuli propagated through cardiac muscle?
Myogenically, which means from muscle fibre to muscle fibre.
Where is smooth muscle found?
The tunica media layer of the walls of most blood vessels
The muscular part of the wall of the digestive tracts and ducts
Skin
What is smooth muscle in the skin referred to as?
Arrector muscles
What are arrector muscles associated with?
Hair follicles
What is the role of smooth muscle?
To move substances and restrict flow
What type of movement does smooth muscle control - voluntary or involuntary?
Involuntary
What generates contraction of smooth muscle?
The ANS
How does smooth muscle regulate the size of the lumen of tubular structures?
It can undergo partial contractions for long periods of time
What type of contractions does smooth muscle undergo in the walls of digestive tract, uterine tubes and ureters?
Peristaltic waves
What are peristaltic waves?
Synchronised rhythmic contractions
What is the process of peristaltic waves called?
Peristalsis
What is the function of peristalsis?
To propel contents along these tubular structures
What nervous system controls peristalsis?
Enteric
What happens to muscles if the nerve they are innervated by becomes damaged?
They will cease to function
What happens if there is loss of nerves innervating muscles of the posterior forearm?
Wrist drop
What happens if there is loss of nerves innervating muscles of the anterior foot?
Foot drop
What is muscular atrophy?
Wasting of muscular tissue in a limb
What are the three causes of muscular atrophy?
Disorder of a nerve
Lesion of a nerve
Prolonged immobilisation of a limb, such as with a sling or cast
What is the purpose of muscle testing?
To diagnose nerve and muscle injuries
How do we test muscles?
Assessing power of movement
In bilateral pairs for comparison
What are the two common methods of testing muscles?
The person performs movement that resist those produced by the examiner
The examiner performs movements against resistance produced by that person
