Chapter 7: Muscular System Flashcards by Abbie Maisie Baler

What are the functions of the muscular system?

Movement
Maintenance of posture
Respiration
Production of body heat
Communication
Constriction of organs and vessels
Contraction of heart

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What are the general properties of muscle tissues?

Contractility
Excitability
Extensibility
Elasticity

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Skeletal muscle - causes attached structures to move
Smooth muscle - increase pressure inside hollow organs
Cardiac muscle - increase pressure inside the heart

Contractility

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Opposing contraction cause muscle to _______

Lengthen

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Ability of muscle to shorten forcefully

Contractility

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Capacity of muscles to respond to a stimulus

Excitability

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Skeletal muscle - stimulus to contract from nerves (controllable)
Smooth and Cardiac muscle - stimulus to contract involuntarily from neural and hormonal signals (spontaneous)

Excitability

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Ability to stretch beyond normal resting length and still be able to contract

Extensibility

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Ability of muscles to recoil to its original resting length

Elasticity

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what are the 3 types of muscle?

Skeletal muscle
Smooth muscle
Cardiac muscle

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attached to bones
long, cylindrical
multiple, peripherally located nucleus
no cell-to-cell attachments
has striations
rhythmic
voluntary and involuntary (reflexes)
body movements

Skeletal muscle

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walls of hollow organs, blood vessels, and glands
spindle shaped
single, centrally located nucleus
gap junctions
doesn’t have striations
autorhythmic (some)
involuntary
moving food through the digestive tract, empties urinary bladder, regulates blood vessel diameter, contracts many gland ducts

Smooth muscle

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heart
branche, cylindrical
single, centrally located nucleus
intercolated disks
has striations
autorhythmic
involuntary
pumping blood

Cardiac muscle

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Skeletal muscle is also called?

Striated muscle

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What are muscle cells also called?

Muscle fibers

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what is the skeletal muscle composed of?

Skeletal muscle tissue, nervous tissue, connective tissue, and adipose tissue

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What are the 3 layers of connective tissue?

Epimysium
Perimysium
Endomysium

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also called as muscular fascia
connective tissue sheath surrounding each skeletal muscle

Epimysium

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numerous visible bundles of muscle fibers that subdivides a whole muscle

Fascicles

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loose connective tissue serving as a passageway for blood vessels and nerves that supply fascicles
separates muscle fascicle from each other

Perimysium

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passageway for blood vessels and nerves that supply each and separate muscle fiber
separate each muscle fiber within each fascicles

Endomysium

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enormous cells that has several hundreds of nuclei under the cell membrane
Most: 1mm to 4cm in length
Some: 30cm to 1ft in length

Muscle fiber

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what are the 3 muscle fiber components that respond and transmit electrical signals

Sarcolemma
Transverse tubules (T tubules)
Sarcoplasmic reticulum

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cell membrane of muscle fiber
multiple nuclei of the muscle fiber are located just deep to it

Sarcolemma

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- inward folds of the sarcolemma - carry electrical impulses into the center of the muscle fiber

Transverse tubules or T tubules

- stores high levels of calcium - its release of calcium is the "switch" for muscle contraction

Sarcoplasmic reticulum

the enlarged portions of the sarcoplasmic reticulum is called?

Terminal cisternae

Cytoplasm of a musle fiber

Sarcoplasm

What are the 2 main structures of muscle fibers?

1. Myofibrils 2. Myofilaments

- bundles of protein filaments - interact to shorten the muscle fiber during contraction - long thread-like structures that extends the length of muscle fibers

Myofibrils

What are the 2 types of myofilament?

1. Actin 2. Myosin

- thin filaments - attachment site for the myosin myofilament

Actin myofilaments

2 components of actin myofilaments which dictates when the skeletal muscle will contract?

1. Tropomyosin 2. Troponin

- covers the active attachment sites - long, fibrous protein lying along the groove of actin strand

Tropomyosin

- consists of 3 subunits - anchors troponin to actin - prevents tropomyosin from uncovering the actin myofilament attachment sites in a relaxed muscle - binds calcium

Troponin

- structural and functional units of skeletal muscles - forms myofibrils - as it shortens, myofibrils shorten too, causing muscle fiber contraction

Sarcomeres

- forms stationary anchor for actin myofilaments - network of protein fibers forming an attachment site for actin myofilaments - separate one sarcomere from the next

Z discs

- light-staining bands - consists only of actin myofilaments - spans each Z disk and ends at the myosin myofilaments

I band

- dark-staining band - center of the sarcomere - contains both actin and myosin myofilaments overlapping

A band

- center of the A band - contains myosin filaments

H zone

- dark line in the middle of the H zone - consist of delicate protein filaments that holds myosin filaments in place

M line

- composed of elongated myosin molecules (tiny golf clubs) - thick myofilaments

Myosin myofilaments

what are myosin filaments consist of?

1. Rod portion 2. Two myosin heads

Lying parallel to the myosin myofilaments

Rod portion

3 properties of myosin heads

- bind attachment sites on the actin myofilaments to form cross-bridges - can bend and straighten during contraction - break down ATP to release energy

- point of contact of motor neuro axon branches with the muscle fiber - consist of enlarged axon terminals that rest in a portion of sarcolemma

Neuromuscular junction or synapse

axon terminal is called

Presynaptic terminal

Space between the presynaptic terminal and muscle fiber membrane

Synaptic cleft

Muscle cell membrane in the area of the junction

Motor end-plate or postsynaptic membrane

- Each presynaptic terminal has numerous mitochondria and many small spherical sacs called - Contains the neurotransmitter acetylcholine

synaptic vesicles

- a molecule that allows a neuron to communicate - can stimulate or inhibit the production of an action potential in the motor-end plate (sarcolemma) by binding it to ligand-gated ion channels - action potential = release of acetylcholine

Neurotransmitter

- specialized membrane transport proteins - when opened, it allows ions to cross the cell membrane

ligand-gated ion channels

The parallel attachment of myofilaments in a sarcomere allows them to interact which causes muscle contraction

Sliding filament model

when a muscle contracts, the actin and myosin myofilaments in the sarcomere _______ each other and ______ the sarcomere

Slides past each other, and shorten the sarcomere

Groups of muscle fibers makes up

Muscle fascicle

shortening the sarcomeres causes _________, _________, __________, and _________ to shorten to produce muscle contraction

myofibrils, muscle fibers, muscle fascicles, and muscles

Sarcomeres lengthen during

Muscle relaxation

2 major types of cell membrane channels

Leak ion channels Gated ion channels

- allows slow leak of ions down their concentration gradient in resting cells

Leak ion channels

- allows slow leak of ions down their concentration gradient in resting cells

Leak ion channels

- most important in stimulated cells - governs the production of action potentials

Gated ion channels

- electrical charge difference across the cell membrane of an unstimulated cell - ready to respond at a moment's notice inside the cell membrane: negatively charged outside the cell membrane: positively charged

Resting membrane potential

Exists because: 1. K+ concentration is higher inside than outside 2. Na+ concentration is higher outside than inside 3. more permeable to K+ than Na+

Resting membrane potential

a device used to measure the resting membrane potential

Oscilloscope

- occurs when excitable cell is stimulated - ion channels in open when cell is stimulated - depolarization and repolarization

Action potentials

Na+ opens and diffuses = positive

Depolarization

K+ opens and diffuses = negative - return to the resting value

Repolarization

autoimmune disorder - antibodies are formed against acetylcholine receptors, reducing the number of receptors in the neuromuscular junction

Myasthenia gravis

After a person dies, Ca+ diffuses causing the body to become very stiff and rigid

Rigor mortis

- acetylcholine is no longer released at the neuromuscular junction - Ca+ concentration decreases until it diffuses away from the troponin molecules and tropomyosin blocks attachment sites on the actin molecules

Muscle relaxation

Response of a muscle fiber to a single action potential along its motor neuron is called

Muscle twitch

What are the 3 phases of muscle twitch?

1. Lag phase 2. Contraction phase 3. Relaxation phase

gap between the time of stimulus application to the motor neuron and the beginning of contraction

Lag or latent phase

Once the Ca+ is released from the sarcoplasmic reticulum initiates cross-bridge formation and cycling

Contraction phase

concentration of Ca+ decreases slowly due to active transport into the sarcoplasmic reticulum

Relaxation phase

What are the 2 types of muscle contractions?

1. Isometric contractions 2. Isotonic contractions

- muscle does not shorten - increases tension in the muscle, but its length stays the same - bones held in place

Isometric contraction

- muscle shortens - increases the tension in the muscles and decreases its length

Isotonic contraction

- amount of force in an individual muscle fiber - increasing the force of contraction of the muscle fibers

Summation

- amount of force in a whole muscle - increasing the number of muscle fibers contracting

Recruitment

- constitute a single muscle - the fewer fibers there are, the greater control you have over the muscle

muscle units

wave summation - incomplete tetanus - complete tetanus

Frequency of stimulation

- do not allow complete relaxation between stimuli

incomplete tetanus

- allows no relaxation between stimuli

Complete tetanus

muscles stay contracted too long (constant tension)

Muscle tone

Types of isotonic and isometric contractions

1. Concentric 2. Eccentric

- overcome the opposing resistance - muscle shortens

Concentric

- tension is maintained, but opposing resistance is great enough to cause the muscle to increase in length

eccentric contractions

- contract more slowly - better developed blood supply, have more mitochondria, more fatigue-resistant - contain large amounts of myoglobin (binds and reserves O2) - type I myosin - works aerobically - large production of ATP with O2

Slow-twitch muscle fibers

- type IIa (with or without O2) or IIb (without O2) myosin heads - works anaerobically - contracts quickly, fatigues quickly - less-well developed blood supply, fewer and smaller mitochondria, very little myoglobin - produce small amount of ATP quickly without O2

Fast-twitch muscle fiber

muscle increase in size or number of muscle fibers - increase in strength and endurance

hypotrophies

Muscle is not used - decrease in size or number of muscle fibers

Atrophies

- occurs in elderly people who cannot readily move their limbs - decrease in size or number of muscle fibers, leads to paralysis

Sever atrophy

- conversion of two ADP to one ATP and one AMP during heavy exercise - conversion of a molecule called creatine phosphate to ATP - Anaerobic production of ATP during intensive short-term work - Aerobic production of ATP during most exercise and normal conditions

ATP production processes

transfers one phosphate from one ADP to a second ADP, resulting in one ATP and one AMP

adenylate kinase or myokinase

- bank for high energy phosphate - transfer a phosphate from creatine phosphate to ADP to produce ATP

creatine phosphate creatine kinase

- does not require O2 , breaks down glucose to produce ATP and lactate - High-intensity, short-duration exercise, such as sprinting or carrying something very heavy, is supported through partially anaerobic pathways - produces far less ATP than aerobic respiration, but can produce ATP in a matter of a few seconds instead of a few minutes like aerobic respiration

Anaerobic respiration

- occurs mostly in mitochondria, requires O2 and breaks down glucose to produce ATP, CO2 , and H2O - can also process lipids or amino acids to make ATP - Low-intensity, long-duration exercise is supported

Aerobic respiration

Temporary state of reduced work capacity - without this, muscle fibers would be worked to the point of structural damage to them and their supportive tissues

Fatigue

What are the mechanisms included in fatigue?

1. Acidosis and ATP depletion 2. Oxidative stress 3. Inflammation

- Anaerobic respiration results in breakdown of glucose to lactate and protons, accounting for lowered ph - Lowered pH = decreased effectiveness of Ca2+ on actin and overall less Ca2+ release from the sarcoplasmic reticulum - can also result when liver dysfunction results in reduced clearance of lactate

Acidosis and ATP Depletion

- Increase in Reactive Oxygen Species (ROS)= breakdown of proteins, lipids, or nucleic acids - trigger an immune system chemical called interleukin (IL)-6 a mediator of inflammation (may cause muscle soreness)

Oxidative stress

type of white blood cell, migrate into heavily worked muscles

T lymphocyte - Inflammation

- occurs when there is too little ATP to bind to myosin myofilaments - muscle become incapable of either contracting or relaxing

Psychological contracture

- most common type of fatigue - involves the central nervous system rather than the muscles themselves - muscles are still capable of contracting, but the individual “perceives” that continued muscle contraction is impossible - overall benefit is that it prevents complete exhaustion of ATP reserves, which could lead to severe damage of the muscle fibers

psychological fatigue

- muscle pain that lasts for several days - injury has increased the permeability of plasma membrane, connective tissue, or muscle fibers has ruptured them

Muscle soreness

- lag time between when a person begins to execise and when they begin to breath more heavily - insufficient oxygen consumption - must be repaid during and after exercise

Oxygen deficit

- lag time before breathing returns to its preexercise rate once exercise stops -reflects muscles' need for oxygen - elevated oxygen consumption - used to repay the oxygen deficit to restore homeostasis

Excess postexercise oxygen consumption

functions as a unit and contract at the same time

Smooth muscle

functions as a unit and contract at the same time

Smooth muscle cells

resulting periodic spontaneous contraction of smooth muscle

Autorhythmicity

- exhibits limited anaerobic respiration - continues to contract at a level that can be sustained by aerobic respiration and consequently does not fatigue

Cardiac muscle

- specialized structures that include tight junctions and gap junctions - facilitate action potential conduction between cells - allows cardiac muscle cells to function as a unit

Intercalated disk

The muscle that is connected to the bone at both ends

Tendon

broad, sheetlike tendons

Aponeuroses

painful, apastic contractions of a muscle, usually due to build up of lactic acid

cramps

- a band of connective tissue that holds down the tendons at each wrist and ankle

Retinaculum

- causes most body movements by pulling one of the bones toward the other across the movable joint

Muscle contraction

- the head - two points of attachment of each muscle - most stationary end of the muscle - usually proximal or medial to the insertion of a given muscle

Origin

- end of the muscle attached to the bone undergoing the greatest movement

Insertion

- part of the muscle between the origin and the insertion

Belly

non life threatening, chronic, widespread pain in muscles with no known cure; also known as chronic muscle pain syndrome

fribromyalgia

muscle that accomplishes a certain movement, such as flexion

Agonist

muscle acting in opposition to an agonist

Antagonist

group of genetic disorders in which all types of muscle degenerate and atrophy

muscle dystrophy

members of a group of muscles working together to produce a movement

Synergist

- among a group of synergist - one muscle that plays the major role in accomplishing the desired movement - the brachialis is the prime mover in flexing the elbow

Prime mover

muscles that hold one bone in place relative to the body while a usually more distal bone is moved

fixators

- most muscles have descriptive names - location: pectoralis (chest), gluteus (buttock), brachial (arm) - size: maximus (large), minimus (small), longus (long), brevis (short) - shape: deltoid (triangular), quadratus (quadrate/rectangular), teres (round) - orientation of fascicles: straight,parallel, oblique - origin and insertion - number of heads - function: body movement

Muscle names/nomenclature

What are the 8 fascicle arrangement?

1. Circular 2. Convergent 3. Parallel 4. Pennate 5. Unipennate 6. Bipennate 7. Multipennate 8. Fusiform

- orbicularis oris - orbicularis oculi - act as sphincters to close the opening

Circular

- pectoralis major - pectoralis minor - broadly distributed fascicles at a single tendon

Convergent

muscles are weak and fail to relax following forceful contractions; affects the hands most severely; dominnt trait in 1/20,000 births

myotonic muscular dystrophy

- trapezium: trapezius - rhomboidal: rhomboideus - quadrate: rectus abdominis

Parallel

fascicles originate from a tendon that runs the length of the entire muscle

Pennate

- fascicles on only one side of the tendon - palmar inerosseus - semimembanosus

Unipennate

- fascicles on both sides of the tendon - rectus femoris

Bipennate

inflammation of a tendon or its attachment point, due to overuse of the muscle

tendinitis

- fascicles arranged at many places around the central tendon - spread out at angles to many smaller tendons - deltoid

Multipennate

- fascicles lie parallel along the long axis of muscle - belly of muscle is larger in diameter than ends - biceps brachii (two-headed;shown) - triceps brachii (three-headed)

fusiform

include those involved in forming facial expressions, chewing, moving the tongue, swallowing, producing sounds, moving the eyes, and moving the head and neck

Muscle of the head and neck

[FACIAL EXPRESSION] raises the eyebrows

Occipitofrontalis

[FACIAL EXPRESSION] Connects the occipital and frontal portions of the muscle

Epicranial aponeurosis

[FACIAL EXPRESSION] encircles the eyes, tightly close the eyelids, and cause "crow's feet" wrinkles in the skin at the lateral corners of the eyes

Orbicularis oculi

[FACIAL EXPRESSION] encircles the mouth

Orbicularis oris

[FACIAL EXPRESSION] sometimes called the kissing muscles or trumpeter's mucle because they pucker the mouth

Buccinators

[FACIAL EXPRESSION] Accomplishes smiling

Zygomaticus

[FACIAL EXPRESSION] Accomplishes sneering

Levator labii superioris

[FACIAL EXPRESSION] Performs frowning and pouting Depresses the corner of the mouth

Depressor anguli oris

- four pairs of muscles for chewing, or mastication - some of the strongest muscles in the body

Mastication

[MASTICATION] can be easily seen and felt on the side of the head during mastication

Temporalis and masseter

[MASTICATION] consisting of two pairs, are deep to the mandible

Pterygoid

- Moves food around in the mouth and, with the buccinator muscle, holds the food in place while the teeth grind the food - pushes food up to the palete and back toward the pharynx to initiate swallowing

Tongue

[TONGUE AND SWALLOWING MUSCLES] located entirely within the tongue and changes its shape

Intrinsic muscles

[TONGUE AND SWALLOWING MUSCLES] located outside the tongue but are attached to and move the tongue

Extrinsic muscles

[TONGUE AND SWALLOWING MUSCLES] - divided into a suprahyoid group and infrahyoid group - when the suprahyoid muscles hold the hyoid bone in place from above, the infrahyoid muscles can elevate the larynx

Hyoid muscles

[TONGUE AND SWALLOWING MUSCLES] Elevates the pharynx

Pharyngeal elevators

[TONGUE AND SWALLOWING MUSCLES] Constrict the pharynx from superior to inferior, forcing the food into the esophagus

Pharyngeal constrictors

[TONGUE AND SWALLOWING MUSCLES] - opens the auditory tube, which connects the middle ear to the pharynx - opening the auditory tube equalizes the pressure between the middle ear and the atmosphere

Pharyngeal muscles

[NECK MUSCLES] - include neck flexors, located along the anterior surfaces of the vertebral bodies, and neck extensors, located posteriorly - rotation and lateral flexion of the head are accomplished by lateral and posterior neck muscles

Deep neck muscles

[NECK MUSCLES] - prime mover of the lateral muscle group, is easily seen on the anterior and lateral sides of the neck - contraction of only one rotates the head

Sternocleidomastoid

- or wry neck - may result from injury to one of the sternocleidomastoid muscles - sometimes caused by damage to a baby's neck muscles during a difficult birth and usually can be corrected by exercising the muscle

Torticollis

[MUSCLES MOVING THE VERTEBRAL COLUMN] group of muscles on each side of the back are primarily responsible for keeping the body straight and the body erect

Erector spinae

[MUSCLES MOVING THE VERTEBRAL COLUMN] - located between the spinous and transverse processes of adjacent vertebrae - are responsible for several movements of the vertebral column, including extension, lateral flexion, and rotation - when the deep back muscles are stretched abnormally, muscle strains and sprains of lumbar vertebral ligaments can occur; low back pain

Deep back muscles

involved almost entirely in the process of breathing

Thoracic muscles

[THORACIC MUSCLES] Elevate the ribs during inspiration

External intercostals

[THORACIC MUSCLES] Contract during forced expiration, depressing the ribs

Internal intercostals

[THORACIC MUSCLES] - accomplishes the major movement produced in the thorax during quiet breathing - when it contracts, the dome flattened, causing the volume of the thoracic cavity to increase, resulting in inspiration

Diaphragm

[ABDOMINAL WALL MUSCLES] - flex and rotate the vertebral column - compress the abdominal cavity - hold in and protect the abdominal organs

Muscles of the anterior abdominal wall

[ABDOMINAL WALL MUSCLES] tendinous area of the abdominal wall - consists of white connective tissue rather than muscle

Linea alba

each side of the linea alba

Rectus abdominis

- cross the rectus abdominis at 3 or more locations, causing the abdominal wall of a lean, well-muscled person to appear well segmented

tendinous intersections

three layers of muscles lateral to the rectus abdominis:

1. External abdominal oblique 2. Internal abdominal oblique 3. Transversus abdominis

[PELVIC FLOOR AND PERINEAL MUSCLES] a ring of bone with an inferior opening that is closed by a muscular floor through which the anus and the openings of the urinary tract and reproductive tract penetrate

Pelvis

[PELVIC FLOOR AND PERINEAL MUSCLES] - also called pelvic diaphragm - formed by the levator ani muscle

Pelvic floor

[PELVIC FLOOR AND PERINEAL MUSCLES] area inferior to the pelvic floor - contains a number of muscles associated with the male or female reproductive structures

Perineum

Include those that attach the limb and pectoral girdle to the body and those in the arm, forearm, and hand

Upper limb muscles

the muscles that attach the scapula to the thorax and move the scapula include:

Trapezius Levator scapulae Rhomboids Serratus anterior Pectoralis minor

[SCAPULAR MOVEMENTS] move the scapula into different positions, thereby increasing the range of movement of the upper limb

Scapular muscles

[SCAPULAR MOVEMENTS] forms the upper line from each shoulder to the neck

trapezius

[ARM MOVEMENTS] - adducts the arm and flexes the shoulder - extend the shoulder from a flexed position

Pectoralis major

[SCAPULAR MOVEMENTS] medially rotates and adducts the arm and powerfully extends the shoulder; "swimmer's muscle"

Latissimus dorsi

[SCAPULAR MOVEMENTS] attached the humerus to the scapula and forms a cuff or a cap over the proximal humerus

Rotator cuff muscles

[SCAPULAR MOVEMENTS] - muscle attaches the humerus to the scapula and clavicle - major abductor - common site for injections

Deltoid

[FOREARM MOVEMENTS] - primary extensor of the elbow, occupies the posterior compartment

triceps brachii

[FOREARM MOVEMENTS] occupies anterior compartment

biceps brachii

[FOREARM MOVEMENTS] Primary flexors of the elbow

Brachialis

[FOREARM MOVEMENTS] A posterior muscles that helps flex the elbow

Brachioradialis

[WRIST AND FINGER MOVEMENTS] responsible for flexion of the wrist and fingers, whereas most of the posterior forearm muscles cause extension

Anterior forearm muscles

[WRIST AND FINGER MOVEMENTS] flex the wrist

Flexor carpi muscles

[WRIST AND FINGER MOVEMENTS] extends the wrist

Extensor carpi muscles

[WRIST AND FINGER MOVEMENTS] serves as a landmark for locating the radial pulse

Tendon of the flexor carpi radialis

[WRIST AND FINGER MOVEMENTS] Visible on the posterior surface of the forearm

Tendons of the wrist extensors

- forceful, repeated contraction of the wrist extensor muscles - may result in inflammation and pain

Tennis elbow

[WRIST AND FINGER MOVEMENTS] flexion of the fingers

Flexor digitorum

[WRIST AND FINGER MOVEMENTS] Extension of the fingers

extensor digitorum

[WRIST AND FINGER MOVEMENTS] - 19 muscles - located within the hand

Intrinsic hand muscles

[WRIST AND FINGER MOVEMENTS] - located between the metacarpal bones - abduction and adduction of the fingers

Interossei muscles

[THIGH MOVEMENTS] anterior muscle

Iliopsoas

[THIGH MOVEMENTS] Posterior muscle

Gluteal muscle

[THIGH MOVEMENTS] Tenses a thick band of fascia on the lateral side of the thigh called iliotibical tract

Tensor fasciae latae

[THIGH MOVEMENTS] Extends the hip and abducts and laterally rotates the thigh - sciatic nerve lies deep and could be damaged during an injection

Gluteus maximus

[THIGH MOVEMENTS] Abducts and medially rotates the thigh - common sites for injections in the buttocks

Gluteus medius

[LEG MOVEMENTS] - anterior muscles - primary extensors of the knee

Quadriceps femoris muscles

[LEG MOVEMENTS] - longest muscle in the body - tailor's muscle - flexes the hip and knee and rotates the thigh laterally for sitting cross-legged

Sartorius

[LEG MOVEMENTS] - extensions of the patellar tendon onto the tibial tuberosity - tapped with a rubber hammer when testing the knee-jerk reflex in a physical examination

Patellar ligament

[LEG MOVEMENTS] - posterior thigh muscles - flexing the knee - tendons are easily felt and seen on the medial and lateral posterior aspect of a slightly bent knee - tendons in hogs or pigs

Hamstring muscles

[LEG MOVEMENTS] Medial thigh muscles - adducting the thigh

Adductor muscles

- 13 muscles in the leg, with tendons extending into the foot

Ankle and toe movements

[ANKLE AND TOE MOVEMENTS] - forms the buldge of the calf - join to form the common calcaneal tenon, or Achilles tendon - flexors and are involved in plantar flexion of the foot

Gastrocnemius and the soleus

[ANKLE AND TOE MOVEMENTS] - lateral muscles of the leg - everters of the foor, but also aid in plantar flexion

Fibularis muscles

[ANKLE AND TOE MOVEMENTS] - 20 muscles located within the foot - flex, extend, abduct, and adduct the toes

Instrinsic foot muscles

- reduction in muscle mass, slower response time for contraction, reduction in stamina, and increased recovery time - loss of muscle fibers (fast-twitch) (25 yrs old) 80 yrs old: 50% - fewer action potentials are produced - decrease in density of capillaries

Effects of aging

- children aged 3 - muscle weakness; waddling gait - muscle atrophy; slow motor development and muscle wasting - contractures - abnormal genes from X chromosome - its gene produces dystrophin (attachment of myofibrils to other proteins in the cell membrane and regulating their activity)

Duchene Muscular Dystrophy (DMD)

Chapter 7: Muscular System Flashcards

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