Muscular System Flashcards
Name the 3 types of muscle and where they’re found
Smooth muscle:
- Usually located in walls of organs, bronchi, vessels
Cardiac muscle:
- Wall of the heart
Skeletal muscle:
- Locomotion, found everywhere
Describe the different functions that skeletal muscle could have
moving organs - e.g. moving the eyeball
Postural - around the spine (low level over a long time)
Limb muscles - movement and power
FUNCTION of skeletal muscle
Locomotion: requires contraction of muscle fibres.
these muscle fibres are made of contractile myofibrils
Describe the microstructure of skeletal muscles.
- Elongated, multinucleated cells
- Peripheral nuclei
- Grouped into bundles called fascicles
- Surrounded by connective tissue:
Epimysium - muscle
Perimysium - fascicle
Endomysium - fibre
Define the following structures:
- Basement membrane
- Sarcolemma
- Sarcoplasm
- Sacromeres
- Satellite cells
Basement membrane is continuous with Endomysium
Sarcolemma is the muscle fiber’s cell membrane
Sarcoplasm is the fiber’s cytoplasm
Sacromeres make up the myofibril
Note the Satellite cells – allow skeletal muscle to regenerate
Describe the microorganisation of a myofibril
Arrangement of sarcomeres.
Two types of filament; Actin filament and myosin filament
contraction occurs as myosin moves along the actin (sliding filament model)
Function of Skeletal Muscle
- The end result is the shortening of a sarcomere
- Shortening occurs between origin and insertion =
- Movement of bone/joint
What are the four components used to describe skeletal muscles?
- Origin
- Insertion
- Action
- Innervation or nerve supply
Characteristics of Pectoralis Major
Origin - Clavicle, sternum and costal cartilages
Insertion - Humerus
Action - Flexion, adduction and Internal rotation of the shoulder joint
Nerve supply - Lateral and Medial Pectoral nerve
Characteristics of Pectoralis Minor
Origin - Ribs 3, 4 and 5
Insertion - Corocoid process of the scapula
Action - Draws scapula anteriorly, inferiorly and medially
- Elevates the ribs
Nerve supply - Medial Pectoral nerve
Biceps brachii
Origin -
- Long head: Supraglenoid tubercle of the scapula
- Short head: Corocoid process of the scapula
Insertion - Radius
Action -
- Flexion of the shoulder joint
- Flexion of the elbow joint
- Supination of the radio-ulnar joints
Nerve supply - Musculocutaneous nerve
Deltoid
Origin - Clavicle, acromion and Spine of the scapula
Insertion - Deltoid tuberosity of the humerus
Action - Abduction of the shoulder joint
Nerve supply - Axillary nerve
Serratus anterior
Origin - Upper 8/9 Ribs
Insertion - Scapula
Action -
- Protraction of the scapula
- Holds scapula flat against the thoracic cage
Nerve supply - Long Thoracic nerve
Different Arrangements of Muscle fibres
- Flat - parellel fibres within an apernosis
- Pennate - feather like may be unipennate, bipennate or mutilpennate
- Fusiform - spindle shaped with round bellie and tappered at tendons
- Quadrate - four sides - quadratus femoris
- Circular - orbicularis oculi
- Multiheaded - biceps
How is contraction controlled?
clue: from start from CNS
Motor nerves insert into the muscle at motor end-plates where there are the neuromuscular junctions
ACh neurotransmitter passes the nerve impulse across the gaps from the motor end plate to the muscle fiber = the neuromuscular junction
Impulse spreads into the sarcolemma (cell membrane) and into T tubules, perpendicular extensions
Sarcoplasmic reticulum is a smooth endoplasmic reticulum in muscle whose function is to store and release Ca when needed
