Chapter 8 & 15 muscular

Muscular Tissue & Muscular

System

Biological ScienceDr. Fedeliz Sandil-Tuy 1

To Contrast the structure and function of skeletal, smooth, and cardiac muscle tissue

To Identify morphological differences in smooth muscle across tissues

To Explain the structure and function of the intercalated disc

To Identify some key pathological examples related to muscle


Muscle cells are highly specialized for contraction.

Such contraction may result in the movement of the whole body or a portion of it if the muscles are attached to a movable part of the skeleton.

If the muscle is located in the wall of a hollow organ, its contraction may cause the contents of the organ to move, e.g. peristaltic movement of material through the digestive tract. Biological ScienceDr. Fedeliz Sandil-Tuy 3

Biological Science

Dr. Fedeliz Sandil-Tuy

4

Identifying Features Striations caused by overlapping actin and myosin filaments.

Multinucleated Functions

Major body muscle contractions involved in locomotion and facial expressions

Protection Heat production

Location All major body muscles

Biological Science Dr. Fedeliz Sandil-Tuy 5

Several specific terms are used exclusively for muscle tissue. Muscle cells are called fibres; their cytoplasm is termed sarcoplasm, and their cell membrane is referred to as sarcolemma.


Identifying Features Long thin cells with

tapering ends Single nucleus No striations

Function Involuntary Muscle contraction

Locations Walls of digestive tract, respiratory tract, blood vessels.


Identifying Features ◦ Striated appearance ◦ Branched fibres ◦ Intercalated discs (these

appear as occasional dark lines)

◦ Single nucleus per cell Function

◦ Heart muscle contraction. Propels blood into circulation (involuntary contractions)

Location◦ Walls of heart.


SkeletalSkeletal VisceralVisceral CardiacCardiac

MovementMovement voluntaryvoluntary involuntaryinvoluntary involuntaryinvoluntary

Rate of Rate of actionaction

fastfast Very slowVery slow moderatemoderate

StriationStriation presentpresent absentabsent presentpresent

Location Location of nucleusof nucleus

peripheryperiphery centercenter centercenter

Number of Number of nucleusnucleus

severalseveral oneone oneone

ShapeShape filamentousfilamentous Fusiform/Fusiform/Spindle-likeSpindle-like

Net-likeNet-like


Voluntary muscle – movement is controlled by the will.

Skeletal muscle Involuntary muscle –movement

is not controlled by the will. Cardiac and visceral

muscles


An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering.

Each muscle is surrounded by a connective tissue sheath called the epimysium.

Fascia, connective tissue outside the epimysium, surrounds and separates the muscles.

Portions of the epimysium project inward to divide the muscle into compartments.


Each compartment contains a bundle of muscle fibers.

Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium.

Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.


Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis.

The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles.

Typically a muscle spans a joint and is attached to bones by tendons at both ends.

One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction


Each myofibril is made up of arrays of parallel filaments.

The thick filaments have a diameter of about 15 nm. They are composed of the protein myosin.

The thin filaments have a diameter of about 5 nm. They are composed chiefly of the protein actin along with smaller amounts of two other proteins: troponin and ropomyosin


Actin & MyosinActin & Myosin

The thick filaments produce the dark A band. The thin filaments extend in each direction

from the Z line. Where they do not overlap the thick filaments, they create the light I band.

The H zone is that portion of the A band where the thick and thin filaments do not overlap.

These fibrils contain the proteins that do the actual force production.

The entire array of thick and thin filaments between the Z lines is called a sarcomere.


Shivers are reflexes which are things your body does automatically to keep you safe and healthy.

Your body needs to stay at 37° Celsius for you to be safe and comfortable. The nerves send signals that we are cold and we need to warm up.

The signals go to your brain and to your spinal cord, which sends a message to other nerves all over your body. Your muscles tighten and loosen really fast.


. Goosebumps happen because

your skin is covered with hair. When the muscles that are attached to each hair get tight, they pull the hair and your skin up into the air.



Skeletons can bend at joints when muscles pull on skeletal elements.

Since muscles act by contracting and shortening, they come in opposing pairs.

One flexes an appendage at a joint, the other extends it and each muscle of the pair relaxes when its partner contracts.

Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short).

Shape: deltoid (triangular); rhomboid (like a rhombus with equal and parallel sides); latissimus (wide); teres (round); trapezius (like a trapezoid, a four-sided figure with two sides parallel).


Direction of fibers: rectus (straight); transverse (across); oblique (diagonally); orbicularis (circular).

Location: pectoralis (chest); gluteus (buttock or rump); brachii (arm); supra- (above); infra- (below); sub- (under or beneath); lateralis (lateral).

Number of origins: biceps (two heads); triceps (three heads); quadriceps (four heads).Biological ScienceDr. Fedeliz Sandil-Tuy 30

Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle, insertion on the mastoid process); brachioradialis (origin on the brachium or arm, insertion on the radius).

Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to flex a structure); extensor (to extend a structure); levator (to lift or elevate a structure); masseter (a chewer).


One of the most predominant characteristics of skeletal muscle tissue is its contractility and nearly all movement in the body is the result of muscle contraction.

Four functions of muscle contraction are movement, posture, joint stability, and heat production.

Three types of muscle are skeletal, smooth, and cardiac. Each muscle fiber is surrounded by endomysium. The fibers are collected into bundles covered by

perimysium. Many bundles, or fasciculi, are wrapped together by the

epimysium to form a whole muscle. Muscles are attached to bones by tendons.



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Chapter 8 & 15 muscular

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