A&P: Chapter 6

The muscular system

how much of the body mass is muscle tissue?

1/2

whats the function of muscle tissue?

contraction

what are the tree main types of muscle tissue?

skeletal, cardiac, and smooth

The cytoplasm of a muscle fiber is called

sarcoplasm

The ability of a muscle to contract depends on what 2 types of microfilaments?

myosin and actin

what do skeletal muscles form?

striated muscle, voluntary muscle, "smooth" contours of body

Individual muscle fibers are wrapped in connective tissue

endomysium

what kind of muscle is directly attached to the skeleton?

skeletal muscle

individual muscle fibers are wrapped in

connective tissue

coarser fibrous membrane

perimysium

many sheathed muscle fibers are wrapped with perimysium form a

fascicle

connect muscle indirectly to bone, cartilage, etc

tendons

epimysia bland together into strong, cord-like \_________ on sheet-like

tendons; aponeuroses

what are the 3 functions of tendons?

anchor muscle. provide durability, and conserve space

describe smooth muscle fibers

spindle shaped, uninucleated, surrounded by small amount of endomysium, 2 layers (circle and longitudinal), and contractions are long and sustainable

describe smooth (visceral) muscle

NOT striated, involuntary, found on wall of hollow organs (stomach; urinary bladder), and propels substances along a tract

describe cardiac muscle

striated, involuntary, fibers are cushioned by small amounts of endomysium (spiral), fibers are branching and joined by special junctions (intercalated discs), steady contractions, can be stimulated for short amount of time

characteristics of producing movements with skeletal muscle

muscle contractions, locomotion and manipulation movements (responds to stimuli), and are distinct from the motions of the smooth and cardiac muscle

types of skeletal muscle functions

produce movement, maintaining posture and body position/stabilizing joints, and generating heat/additional functions

additional skeletal muscle functions are:

protecting internal organs, valves regulating passage, dilate and constrict pupils in the eyes, and activate arrector pili (make hair stand)

plasma membrane of fiber

sarcolemma

the nuclei in a fiber are pushed aside by special organelles called \______________

myofibrils

I bands are called \_______ and A bands are called \_______

light; dark

dark, midline interruption of the I band

Z disc

a tiny contractile unit - makes up myofibrils

sarcomeres

smaller structures within sarcomeres that actually provide the banding pattern

myofilaments

lighter central area of A band

H zone

middle of h zone that contains tiny protein rods that hold adjacent thick filaments together

M line

thin filaments are made of \__________ and thick filaments are made of \____________

actin filament; myosin filament

interconnecting tubules and sacs surrounding every myofibril; stores calcium and releases it when stimulated

sarcoplasmic reticulum (SR)

receive and respond to stimulus

excitability

ability to be stretched

extensibility

How does a muscle contract?

a motor neuron may stimulate muscle fibers depending on the type and function of muscle

what is a motor

one neuron and all muscle fibers it stimulates

long thread-like extension of neuron

axon

when axon reaches muscle it branches into

axon terminals

what happens when axon reaches axon terminals

it forms junctions with the sarcolemma of each muscle fiber it stimulates

at the ends of axon terminals are vessels containing

neurotransmitters (ACH) that stimulate muscles

step 1 of action potential

nerve impulse reaches the axon terminal

step 2 of action potential

calcium channels in axon terminal open and calcium ions enter

step 3 of action potential

entry of calcium leads some synaptic vesticles in axon terminal to release Ach

step 4 of action potential

Ach diffuses across synaptic cleft and attaches to receptors located in the sarcolemma

step 5 of action potential

If enough ACh is released, the sarcolemma becomes TEMPORARILY more permeable to Na+ and K+

step 6 of action potential

Depolarization causes an electrical current (action potential) then, muscle contracts

what happens when action potential occurs?

Ach is broken down by AChE into the acetic acid and chlorine

how many contractions can a single nerve impulse produce?

1

what do the breakdown of Ach prevent?

a continuous contraction in the absenor of additional nerve impulses

steps for a to return to rest

1. diffusion of k out of the cell 2. operation of the sodium being pumped out of the cell and potassium into the cell

sliding filament theory

theory that actin filaments slide toward each other during muscle contraction, while the myosin filaments are still

what does the attachment of myosin heads to actin filaments require

ca2+

what does action potential stimulate

the sarcoplasmic recticulum to release Ca2+ and trigger the binding of myosin to actin

How can graded responses be produced?

muscle stimulation changing frequently or a change in the number of fibers being stimulated at a time

graded response

muscles reacting with different degrees of shortening or contractions

muscle response to increasingly rapid stimulation

muscle twitches and nerve impulses are delivered which produce strong and smooth contractions

what happens when the tetanus are complete

there is no sign of reactions and contractions are smooth and sustained

when the muscle is stimulated but not fused tetanus

incomplete tetanus

since the muscle store little ATP what has to happen?

Hydrogen must be regenerated continuously to continue contracting

what are the 3 pathways to create ATP

direct phosphorylation of ADP by creatine phosphate, aerobic respiration, anaerobic glycolysis and lactic acid formation

aerobic respiration occurs in

mitochondria and involves a series of metabolic pathways that use oxygen

what is the process of aerobic respiration

gluclose is broken down into ca+ and water, energy is released when gluclose is captured by atp. 1 glucose creates 32 ATP molecules

Glycolysis

first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid

lactic acid formation

Occurs when not enough oxygen is available to send pyruvic acid into aerobic respiration

what's good about anaerobic glycolysis

2 1/2 times faster than aerobic respiration and can provide most of the ATP needed for 30-40 seconds of strenous muscle activity

negative aspects of anaerobic glycolysis

lactic build up promotes muscle soreness and produces only 5% of ATP per glucose molecules

muscle fatigue

inability of a muscle to contract even when stimilated

What causes muscle fatigue?

when oxygen deficit during long prolongued muscle activity and not receiving enough oxygen to supply the muscle

Paying back oxygen deficit...

taking quick and long breaths after workout allowing muscles to gain enough oxygen to create ATP

A muscle contraction that pulls on the bones and produces movement of body parts.

isotonic contraction

Muscle contracts but there is no movement, muscle stays the same length

isometric contraction

when motion is not visable but becomes firm, healthy, and ready for motion

motion tone

flaccid

flabby

atrophy

to waste away

produces more flexible, stronger muscles with a greater resistance to fatigue, no increase in size

aerobic exercise

using muscles against an immovable or almost immovable object leading to an increase in muscle size and strength

isometric exercise

Five Golden Rules of Skeletal Muscle Activity

1. With a few exceptions, all skeletal muscles cross at least one joint
2. Typically, the bulk of a skeletal muscle lies proximal to the joint crossed
3. All skeletal muscles have at least two attachments: the origin and the insertion
4. Skeletal muscles can only pull; they never push
5. During contraction, a skeletal muscle insertion moves toward the origin

the immovable or less movable end

origin

The attachment of a muscle tendon to a moveable bone or the end opposite the origin

insertion

decreases the angle of the joint and brings two bones closer together

flexion

increases angle of joint moving 2 bones farther apart

extension

movement of a bone around its longitudinal axis

rotation

moving a limb away from the midline of the body

abduction

Movement of the body toward the midline

adduction

combination of flexion, extension, abduction, and adduction

circumduction

superior portion of the foot moves closer to the shin (standing on your heel)

dorsiflexion

what does dorsiflexion correspond to

the extension of the hand at the wrist

pointing the toes

plantar flexion

what does plantar flexion correspond to

flexion of the hand

turning sole medially

inversion

turning the sole of the foot laterally

eversion

forearm rotates laterally so palm faces anteriorly

supination

forearm rotates medially so palm faces posteriorly

pronation

Movement of the thumb to touch the fingertips, allows grasping and manipulation

opposition

muscle that has the major responsibility for causing any movement

prime mover

oppose or reverse a movement

antagonists

Direction of muscle fibers

rectus, transverse, oblique

relative size of muscles

maximus (largest), minimus (smallest), longus (long), brevis (short)

location of muscle

bone or body region associated with the muscle

number of origins

biceps, triceps, quadriceps

Location of the muscle's origin and insertion

sternocleidomastoid

shape of muscle

deltoid, trapezius