Unit 3: Muscular System Flashcards
Properties of muscular tissue
Electrical excitability, contractile, extensible, and elastic.
Electrical excitability
Electrical excitability refers to the ability of a muscle to respond to stimuli, such as neurotransmitters, by eliciting an electrical signal called an action potential.
Contractile
Contractility refers to the ability of a muscle to shorten in response to an action potential.
Elastic
Elasticity refers to the ability of a muscle to recover its original shape after contraction or extension.
Extensible
Extensibility refers to the ability of a muscle to stretch (without injury).
3 different types of muscles in the body
Skeletal, cardiac, and smooth.
Skeletal
Attached to the skeleton; Under voluntary control, not always conscious though, and can tire quickly.
How do skeletal muscles attach to the skeleton?
Directly via tendons or indirectly through connective tissue sheets (aponeurosis).
Cardiac Muscle
Found in the walls of the heart; has the ability to contract without external stimulation; involuntary control; does not tire and continuously pumps blood.
Smooth Muscle
Found in the walls of the internal organs (digestive system, walls of blood vessels, and intrinsic muscles of the eye); has the ability to contract without external stimulation but rather modified by the autonomic NS and hormonal stimulation. Involuntary, does not tire.
Functions of the muscular system
Body movements, stabilize joints, maintain body position, storage of substances, movement of substances, thermogenesis (contracting muscles as a byproduct of heat/maintain temp), and communication.
Successive levels of skeletal muscles from smallest to largest
Myofilaments –> myofilaments –>muscle fibers –> fascicles –>skeletal muscle
Fascicles
Bundles of muscle fascicles that make up the skeletal muscle
Muscle fibers
Muscle cells; bundles of these make up fascicles.
Myofibrils
Tubes composed of protein filaments; bundles of these make up muscle fiber.
Myofilaments
The protein responsible for muscle contraction; bundles of these make up myofibril.
Anatomy of skeletal fiber: 3 levels of organization
Endomysium, perimysium, and epimysium
Endomysium
A thin layer of connective tissue that surrounds each muscle fiber (cell). Lies deep to the fascia.
Perimysium
Thick layer of connective tissue that surrounds organized bundles of muscle fibers (fascicles).
Epimysium
Connective tissue that covers individual muscle fibers.
Sarcolemma
The plasma membrane of a muscle fiber.
Sarcoplasma
Cytoplasm in of a muscle
Sarcomere
the basic functional unit of a myofibril, consisting of a complex
arrangement of contractile proteins (myofilaments)
Contractile protein
actin and myosin are the main myofilaments that form the sarcomere.
Actin
forms the thin myofilaments in the of the sacromere.
Myosin
Forms the thick myofilaments of the sarcomere.
Sliding filament mechanism
Muscle contraction occurs because thick filaments
bind onto the thin filaments by forming chemical bonds called “crossbridges”
It involves the movement of thick and thin filaments, relative to one another, to cause active shortening of a muscle fiber.
What 3 periods do twitch contractions occur in?
Latent period, contraction period, and relaxation period.
Latent period
time between the stimulation of a muscle fiber and contraction of that muscle.
Contraction period
period of crossbridge formation.
Relaxation period
occurs once peak tension has been developed and stimulation is removed.
Slow twitch fibers
generate ATP slower than their counterpart fast-twitch fibers.
Aerobic respiration which is slow.
Lots of mitochondria and myoglobin giving a red pigmentation.
ex. large muscles, gluteals
Fast twitch fibers
generate ATP at a faster pace. Quicker because of anaerobic respiration.
Ex. small muscles, intrinsic muscles of the eye
Skeletal muscle metabolism
use adenosine tri-phosphate (ATP) directly for
contractile activities
Muscles regenerate ATP in 3 ways
creatine phosphate, anaerobic respiration,
and aerobic respiration
Creatine phosphate
high energy molecule. first port of call when muscles are in need of more ATP.
Yield: one ATP molecule for every creatine phosphate; 15 secs
Anaerobic respiration
When oxygen supply is insufficient in muscles, myofiber can produce energy without oxygen.
Yield: 2 ATP molecules per glucose molecule
Aerobic respiration
When oxygen amounts are insufficient, however, slower than anaerobic respiration.
Yield: 36 ATP
Muscle are grouped into 5 categories
fusiform, parallel, pennate, orbicular, and convergent muscles
Fusiform
formed by a central muscle belly that converges at one (or both) ends into a tendon.
Fusiform Muscles
formed by a central muscle belly that converges at one (or both) ends into a tendon.
Examples of fusiform muscles
One-headed: extensor carpi radialis longus.
Two-headed: biceps brachii.
Three-headed: triceps brachii.
Parallel Muscles
formed by muscle fibers that lie parallel to each other. They form flat, straight, quadrate, and 2-bellied muscles.
Examples of parallel muscles
Flat: transversus abdominis
Straight: rectus abdominis
Quadrate: pronator quadratus.
2-bellied: omohyoid
Pennate muscles
formed when muscle fibers are attached obliquely to a central tendon, much like the barbs of a feather.
Examples of pennate muscles
Unipennate: flexor pollicis longus.
Bipennate: rectus femoris
Multipennate: deltoid
Orbicular muscles
A sphincter-like sheet of muscle that encircles an orifice, such as the mouth or the palpebral fissures.
E.g., orbicularis oculi.
Convergent muscles
Triangular muscles; Fibers that originate from a large area but converge onto one attachment point.
Ex. temporalis, pectoralis major
Co-ordination of movement
Primer mover (agonist): primarily responsible for moving (ex. triceps extending elbow)
Antagonist: acts to oppose the action of the muscle (ex. bicep brachii to the tricep; flexes elbow)
Synergists: assists prime mover; stabilize and promotes (ex. brachialis helps biceps flex elbow)
Fixator: holds muscle in place to allow for efficiency (ex. rotator cuff fixes the shoulder joint)
Muscles of facial expression
Muscles of the scalp and forehead, the ocular, nasal, and oral region.
Occipitofrontalis
This muscle has two parts, one on the forehead and one on the back of the head, both of which are joined by an aponeurosis.
Frontal belly- Raises the eyebrows and wrinkles the forehead.
Occipital belly- Retracts the scalp.
Corrugator Supercilii
A small muscle of the eyebrow. Wrinkles the skin between the eyebrows.
Orbicularis oculi
A circular muscle surrounding the eye.
Closes the eye.
Levator palpebrae superioris
A thin muscle within the upper eyelid.
Raises the upper eyelid.
Procerus
A small muscle of the bridge of the nose.
Wrinkles the skin over the nose.
Nasalis
A small muscle of the side of the nose.
Dilates the nostrils.
Orbicularis oris
A circular muscle surrounding the mouth and lips.
Closes and purses the lips.
Levator labii superioris
A small, flat muscle attached to the upper lip.
Raises the upper lip.
Levator anguli oris
A small, flat muscle attached to the upper lip.
Raises the corner of the mouth.
Zygomaticus major
A long, thin muscle of the cheek.
Pulls the corners of the mouth upwards and outwards.
Zygomaticus minor
A long, thin muscle of the cheek.
Raises the upper lip.
Depressor anguli oris
A triangular muscle located at the side of the chin.
Pulls the corners of the mouth downwards.
Depressor labii inferioris
A flat muscle of the chin.
Depresses the lower lip.
Risorius
A thin muscle of the cheek.
Pulls the corner of the mouth laterally.
Mentalis
A short muscle of the chin.
Raises and protrudes the lower lip.
Buccinator
A sheet of muscle within the cheek.
Compresses the cheek.
Platysma
A thin, superficial muscle of the anterior neck.
Wrinkles the skin of the neck.
MUSCLES OF MASTICATION
strong muscles involved in chewing. They forcibly open and close the mandible and move it forwards and backwards and from side to side.
(chew and talk: temporalis, masseter, medial pterygoid,
lateral pterygoid)
Temporalis
A large, fan-shaped muscle on the lateral surface of the head.
Elevates and retracts the mandible.
Masseter
A powerful, oblong muscle located on the side of the face.
Elevates the mandible.
Medial pterygoid
A rectangular muscle located deep to the mandible.
Opens and closes the jaw. Moves the jaw from side to side and forwards and backwards.
Lateral pterygoid
A muscle with two heads located deep to the mandible.
Opens, protrudes, and laterally moves the mandible.
Muscles of the neck
flexors (sternocleidomastoid, scalenes)
extensors (splenius capitis, splenius cervicis, semispinalis capitis)
