NASM Ch5 Muscular System

muscular system

links the nervous and skeletal systems and is responsible for generating the forces that move the human body

muscle

contract to create internal tension that, under the control of the nervous system, manipulates the bones to produce movements around the joints

cardiac muscle

what makes up the heart

smooth muscle

primarily makes up the tissues of internal organs

skeletal muscle

holds the most importance for the fitness professional’s base of knowledge

skeletal muscle

The type of muscle tissue that connects to bones and generates the forces that create movement.

fascia

Connective tissue that surrounds muscles and bones.

epimysium

Inner layer of fascia that directly surrounds an entire muscle, commonly referred to as the “deep fascia.”

fascicles

Largest bundles of fibers within a muscle and surrounded by perimysium.

perimysium

Connective tissue surrounding a muscle fascicle.

endomysium

Connective tissue that wraps around individual muscle fibers within a fascicle

connective tissue

They allow the forces generated by the muscle to be transmitted from the contractile components of the muscle to the bones, creating motion

bone

red

tendon

dark blue

epimysium

orange

muscle fiber

light blue

fascicle

pink

blood vessels

green

endomysium

black

perimysium

yellow

sarcolemma

Within the endomysium of the fascicles, individual muscle fibers are themselves encased by a plasma membrane known as

glycogen

Glucose that is deposited and stored in bodily tissues, such as the liver and muscle cells; the storage form of carbohydrate.

myoglobin

Protein-based molecule that carries oxygen molecules into the muscles.

myofibrils

The contractile components of a muscle cell; the myofilaments (actin and myosin) are contained within

myofilaments

The filaments of a myofibril; include actin and myosin.

actin

The thin, stringlike, myofilament that acts along with myosin to produce muscular contraction.

myosin

The thick myofilament that acts along with actin to produce muscular contraction.

sarcomere

The structural unit of a myofibril composed of actin and myosin filaments between two Z-lines.

z-line

The meeting point of each sarcomere.

skeletal muscle fiber

black

nucleus

green

sarcolemma

pink

myofibril

orange

mitochondrion

red

sarcoplasm

yellow

z-line

pink

thin filaments

green

sarcomere

purple

thick filaments

orange

myofibril

red

tropomyosin

located on the actin filament and blocks myosin-binding sites located on the actin filament, keeping myosin from attaching to actin when the muscle is in a relaxed state

troponin

located on the actin filament, plays a role in muscle contraction by providing binding sites for both calcium and tropomyosin when a muscle needs to contract

neural activation

The nervous system’s signal that tells a muscle to contract.

neuromuscular junction

The specialized site where the nervous system communicates directly with muscle fibers.

synapse

A junction or small gap between the motor neuron and muscle cells.

motor unit

A motor neuron and all of the muscle fibers that it innervates.

neuromuscular junction

red

axon of motor neurons

purple

skeletal muscle fibers

orange

action potential

Nerve impulse that is relayed from the central nervous system, through the peripheral nervous system, and into the muscle across the neuromuscular junction.

neurotransmitters

Chemical messengers that cross the synapse between neuron and muscle and assist with nerve transmission.

acetylcholine

A neurotransmitter that helps the action potential cross the synapse into the muscle, which initiates the steps in a muscle contraction.

sliding filament theory

The series of steps in muscle contraction involving how myosin (thick) and actin (thin) filaments slide past one another to produce a muscle contraction, shortening the entire length of the sarcomere.

excitation-contraction coupling

The physiological process of converting an electrical stimulus to a muscle contraction.

muscle contraction

shortening of the sarcomeres, which contain actin and myosin myofilament

Once the action potential from the CNS stops

the muscle becomes relaxed and resets itself in preparation for the next impulse from the CNS

calcium

helps stimulate actin and myosin activity inside the muscle

sodium and potassium

help transmit the motor signal down the nerve axon

water

electrically conductive, can be considered the main electrolyte of the body because it is involved in most scenarios of bodily function

electrolyte or water imbalance

may lead to exercise-associated muscle cramps

power stroke

The myosin heads bind to actin and pull them toward the sarcomere center, which slides the filaments past each other, shortening the muscle.

adenosine triphosphate (ATP)

A high-energy molecule that serves as the main form of energy in the human body; known as the energy currency of the body.

resting length

The length of a muscle when it is not actively contracting or being stretched.

type 1 muscle fibers

Muscle fibers that are small in size, generate lower amounts of force, and are more resistant to fatigue.

type 2 muscle fibers

Muscle fibers that are larger in size, generate higher amounts of force, and are faster to fatigue.

all-or-nothing principle

Motor units cannot vary the amount of force they generate; they either contract maximally or not at all.

capillaries

The smallest blood vessels and the site of exchange of elements between the blood and the tissues.

Type IIx

have a lower oxidative capacity and fatigue very quickly

type IIa fibers

commonly known as “intermediate fast-twitch fibers.” They can use both aerobic and anaerobic metabolism almost equally to create energy

action potential

green

neurotransmitter molecule

orange

synaptic gap

red

receptor site

purple

myosin

pink

actin

green

shortened

blue

lengthened

gray

muscle cell

red

relaxed

purple

contracted

orange

axon terminal

black

synaptic cleft

orange

ACh

gray

calcium

yellow

T tubule

light green

plasma membrane

pink

sarcoplasmic reticulum

light blue

stage 1 of ECC

ACh released

stage 2 of ECC

action potential releases t tubules

stage 3 of ECC

sarcoplasmic reticulum reaches calcium ions

stage 4 of ECC

myosin head binds to actin

stage 5 of ECC

contraction begins