muscular system

connective tissue surrounding a fascicle

perimysium

connective tissue covering the entire muscle

epimysium

contractile unit of muscle

myofibril

a muscle cell

fiber

thin connective tissue enclosing each muscle cell

endomysium

plasma membrane of the muscle cell

sarcolemma

a long, filamentous organelle found within muscle cells that has a banded appearance

myofilament

actin or myosin containing structure

sarcomere

a discrete bundle of muscle cells

fascicle

a motor neuron and all of the skeletal muscle cells it stimulates is called—

a motor unit

the axon of each motor neuron has numerous endings called—

axon terminals

the actual gap between an axonal ending and the muscle cell is called—

a synaptic cleft

within the axonal endings are many small vesicles containing a neurotransmitter substances called—

acetylcholine

when the ___ reaches the ends of the axon, the neurotransmitter is released, and it diffuses to the muscle cell membrane.

action potential

1st step of muscular contraction

ACh is released into the neuromuscular junction by the axon terminal

2nd step of muscular contraction

ACh diffuses across the neuromuscular junction and binds to receptors on the sarcolemma

3rd step of muscular contraction

depolarization occurs, and the action potential is generated

4th step of muscular contraction

the action potential, carried deep into the cell, causes the sarcoplasmic reticulum to release calcium ions.

5th step of muscular contraction

the calcium ions concentration at the myofilaments increases; the myofilaments slide past one another, and the cell shortens.

6th step of muscular contraction

as calcium is actively reabsorbed into the sarcoplasmic reticulum, its concentration at the myofilaments decreases

7th step of muscular contraction

the muscle cell relaxes and lengthens

___ is a continuous contraction that shows no evidence of relaxation

fused tetanus

an ___ is a contraction in which the muscle shortens and work is done

isotonic

to accomplish a strong contraction, ___ are stimulated at a rapid rate

many motor units

when a weak but smooth muscle contraction is desired, ___ are stimulated at a rapid rate

few moto units

when a muscle is being stimulated but is not able to respond because of “oxygen deficit”

Muscle fatigue

an ___ is a contraction in which the muscle does not shorten, but tension in the muscle keeps increasing

isometric contraction

creatine phosphate

• used during short, powerful movements (sprinting, lifting

• supplies energy 10-15 seconds

Anaerobic glycolysis

• requires no oxygen

• the slowest ATP regeneration process

• fast; doesn’t last forever

• has a burning sensation (Latic acid)

aerobic respiration

• powers muscles during rest or light/moderate exercise

• requires oxygen

• uses glucose and fatty acid

• produces a lot of ATP

muscle tone

“resting” muscle tension, though muscles are never completely.

what occurs within a muscle cell during oxygen deficit

• decreased ATP

• decreased carbon dioxide

• increased lactic acid

• decreased oxygen

Buccinator

muscle in the cheek that runs horizontally.

Actions:

• flattens cheek (whistling, blowing)

• holds food between teeth while chewing.

Frontalis

frontal bone → eyebrows

action:

• raises eyebrows

• wrinkles forehead

blank

blank

occipitalis

posterior skull

pulls scalp

orbicularis oculi

circular muscle around the eye

actions:

• blinking

• squinting

• winking

• closing eyes

orbicularis oris

circular muscle around the mouth

the kissing muscle

actions:

• closes mouth

• protrudes lips

zygomaticus

runs from cheekbone to corner of mouth

action:

• raises corners of the mouth

platysma

in neck

pulls corners of mouth downward

Sternocleidomastoid (SCM)

sternum & clavicle

• flexes the neck

• rotate face

• tilt the head

intercostals

between the ribs

• lifts and lowers the ribs to asset breathing

diaphragm

floor of thoracic cavity

• primary muscle of normal breathing

• unique muscle that is controlled by both voluntary and involuntary tissue

deltoid

prime mover for shoulder abduction

external intercostal

an unpaired muscle; acts with the internal intercostal to accomplish inspiration.

external oblique

part of the abdominal gridle; forms the external lateral walls of the abdomen.

internal intercostal

deep muscles of the thorax that promote the inspiratory phase of breathing

internal oblique

two muscle pairs that help form the natural abdominal girdle

rectus abdominis

straight muscle of the abdomen

erector spinae

prime mover of back extension; a deep composite muscle consisting of three columns

quadratus lumborum

fleshy muscle forming part of the posterior abdominal wall that helps maintain upright posture.

Adductors

muscle group that allows you to draw your legs to the midline of your body, as when standing at attention.

fibularis muscles

muscle group of the lateral leg; plantar flex and evert the foot.

Gastrocnemius

“toe dancers”

a two-bellied muscle of the calf

Gluteus Medius

smaller hip muscle, commonly used as an injection site

hamstrings

muscle group that extends the thigh and flexes the knee.

• bicep femoris

• semimembranosus

• semitendinosus

iliopsoas

hip flexor, deep in pelvis; a composite of two muscle

quadriceps

muscle group that extends the knee

sartorius

straplike muscle that is a weak thigh flexor

“tailors muscle”

soleus

plantar flexor

lays beneath gastrocnemius

tibialis anterior

inverts and dorsiflexes the foot

extensor digitorum

muscle that extends the fingers

flexor digitorum superficialis

muscle that flexes the fingers

flexor capri ulnaris

wrist flexor that follows the ulna

extensor carpi radialis

extends the wrist and follows the radius