MUSCULAR SYSTEM

600

The muscular system consists of over ____ muscles

muscles

produce all voluntary movements

Tendon

when the muscles attach to the bones

• Movement

• Maintenance of Posture

• Respiration

• Heat Generation

• Communication

• Constriction of Organs and Blood Vessels

• Pumping Blood/Contraction of the Heart

• Other Functions

Functions of the Muscular System

Movement

Contraction of skeletal muscles, responsible for the overall movement of the body

Maintenance of Posture

Skeletal muscles constantly maintain tone (sitting or standing erect).

Respiration

Drives air movement in and out of the body

Respiration

Contraction of the skeletal muscles of the thoracic cage, diaphragm (helps us breathe).

Heat Generation

Movement enables heat into the body.

Communication

Muscle tissues allow us to talk, gesture, write, and convey our emotional state.

Constriction of Organs and Blood Vessels

Contraction of smooth muscle within the walls of internal organs causing it to constrict. (Digestive, Respiratory, Urinary System (smooth muscle))

Pumping Blood/Contraction of the Heart

Blood moves through the blood vessels and our heart receives blood.

Pumping Blood/Contraction of the Heart

The muscles help move blood throughout the body.

Other Functions

Protects fragile internal organs, maintains integrity of body cavities.

• Excitability

• Contractility

• Extensibility

• Elasticity

Characteristics of the Muscle

Excitability

Ability to respond to stimulus by producing electrical signals. (action potentials - AP).

Contractility

Movement of the muscle, capable of contracting or shortening (after receiving stimulation)

Extensibility

Ability to stretch without being damaged.

Elasticity

Ability to return to original length and shape after contraction.

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Types of Muscle Tissue

Skeletal Muscle

• voluntary, striated

• opening of internal tract

Cardiac Muscle

• involuntary, striated

• heart

Smooth Muscle

• involuntary, not striated

• esophagus, stomach, intestine and blood vessels

Skeletal Muscle

Found at the openings of internal tracts to control movement

Skeletal Muscle

• Abundant, bones connect to muscles

• Most skeletal muscle runs from one bone to another.

• One bone will move while the other bone will remain fixed

• Origin

• Insertion

• Fleshy Attachments

• Indirect Attachments

• Bone Markings

Parts of the Skeletal Muscle

Origin

less movable attachment.

Insertion

more movable attachment

Fleshy Attachments

• connective tissue fibers that are usually short

• EX: Belly’s muscle

Indirect Attachments

• when its layers of connective tissue

• EX: merge to form a cord-like tendon or a broad, flat sheet called an aponeurosis

Aponeurosis

connects the muscle to a bone or to another muscle, no origin and insertion

Bone Markings

• present where tendons meet the bones.

• EX: Tubercles, Trochanter, Crests, Subscapularis

• Muscle

• Fascicles

• Muscle Fiber/Cells

• Myofibrils

• Thick and Thin Filaments

structure of the muscles

Fascia

General Covering

Fascicle

bundles of muscle fibers

Skeletal Muscle

located throughout the body at the openings of internal tracts to control the movement of various substances. (tear ducts, urethral orifice, anal opening)

Tendon

fibrous connective tissue, muscle to bone

Fascia

fibrous connective tissue, provide support and shape, movement

Aponeurosis

Layers of delicate thin sheets, can act as fascia

Epimysium

Perimysium

Endomysium

LAYERS OF CONNECTIVE TISSUE

Epimysium

fibrous, thin sheet surrounding the skeletal muscle

Epimysium

Separates the muscle from the surrounding tissues, contract & maintain structure

Perimysium

• Groups muscle fibers (cells) into bundles (fascicles)

• passageway for blood vessels & nerves

Endomysium

• Within the muscles surrounding the fascicles

• gliding in contraction is highly deformable tissue

• separates muscle fibers

Fascicle

• Arteries, Veins, and Motor Neuron

• Group of bundled muscle fibers covered by perimysium

• Every muscle fiber is supplied by the axon branch of a somatic motor neuron (signals the fiber to contract)

Motor Neuron

originated from the spine, neuromuscular Junction

Somatic Motor Neuron

type of motor neuron: skeletal muscle

Sensory Neuron

type of motor neuron: attach, skin, eyes, nose, ears

Neuromuscular junction (NMJ)

Site for the transmission of action potential from venue to muscle.

Muscle Fiber

• Specialized Cells

• Each muscle cell consists of muscle fibers.

• The predominant function is contractibility.

• Sarcolemma (Plasma Membrane)

• Sarcoplasmic Reticulum

• Myofibrils

• Muscle Proteins

Inside the Muscle Cells

Sarcolemma (Plasma Membrane)

• Surrounds the muscle fibers

• Contains Sarcoplasm

• Conducts electrical Ca2+ions (calcium + ions)

Sarcoplasm

The cytoplasm of the muscle cells

Sarcoplasmic Reticulum

• Series of close saclike membranes

• stores calcium (needed for muscle movement)

• Cufflike structure

Myofibrils

• Made up of myosin (thick) & actin (thin)

• Help give the muscle its striped appearance

• Long chain of sacromeres (contractile units of cells)

1. Tropomyosin

2. Troponin

Muscle Proteins

How do Muscles Contract

1. brain sends message

2. signal reaches musclel

3. protein filaments slide (actin & myosin)

• relax: lengthy

• contract: short

4. energy powers the action (ATP)

5. relaxation

• signal stops: calcium goes back to storage or normal length

• myosin lets go of actin

Muscle Weakness

Muscle loses its ability to contract

Muscle Cramps

happens due to lactic acid build-up

• Vigorous activity

• Dehydration

• Holding position for a long time

500ml

the urinary can only hold a total of ___ ml and when it fills, you feel the urge to pee.

urinary sphincter

helps us hold our pee

anal sphincter

helps us hold our poop whenever you want to take a shit

water, proteins, minerals, organic compounds

Chemical Composition of Muscles

Types of Movements of the Muscles

• Flexion

• Extension

• Abduction

• Adduction

• Rotation

• Circumduction

• Pronation

• Supination

• Dorsiflexion

• Plantarflexion

• Inversion

• Eversion

Flexion

decreases angle

Extension

increase angle

Abduction

moving away from the midline

Adduction

towards the midline

Rotation

around a longitudinal axis

Circumduction

combination of flexion, extension

Pronation

rotates medially

Supination

rotates laterally

Dorsiflexion

lifting superior

Plantarflexion

depressing the foot

Inversion

sole medially

Eversion

sole laterally

Synergists

helper muscles

Antagonists

opposing muscles

• Isotonic Contractions

• Isometric Contractions

• Isokinetic Contractions

MUSCLE CONTRACTIONS

Isotonic Contractions

Muscle tension stays constant as the muscle length changes

Concentric

The muscle shortens

• Lifting a dumbbell during a bicep curl

Eccentric

The muscle lengthens while under tension

• Lowering a dumbbell back down during a bicep cur

Isometric Contractions

The muscle generates force, but its length does not change.

• Holding a plank, pushing against a wall, or holding a heavy object steady in one place.

Isokinetic Contractions

The muscle length changes at a constant speed.

• This requires specialized equipment (a dynamometer) that adjusts resistance to maintain a fixed speed.

• used in physical therapy and athletic training for precise rehabilitation and strength testing.