Chapter 24: The Muscular System

Muscle of facial expressions

Frontalis- muscle that raises the eyebrows Orbicularis oris- muscle that allows the lips to pucker Orbicularis oculi- muscle that allows the eyes to close Zygomatic- muscle pulls the corners of the mouth up

The pectoral girdle is known as the

shoulder

What is the only neurotransmitter that causes skeletal muscle to contract?

Acetylcholine

Aging and the Musculoskeletal System

Aging of the skeletal system causes more obvious difficulties for those with diseases and conditions such as arthritis, fractures, and osteoporosis, muscualr decline often goes hand-in-hand with these changes. Aging causes a decline in the speed and strength of muscle contractions, even though the actual endurance of muscle fibers changes very little. The elderly often have increasing difficulty with dexterity and gripping ability. Mobility may decrease related to the combined decline of the musculoskeletal system. The patient's diet and exercise history, as well as family history, also has a direct impact on the patient's mobility and activity level as they age.

acetylcholinesterase

An enzyme within the nervous system that hydrolyzes acetylcholine to acetate and choline.

Structues of Skeletal Muscles

Are the major organs that make up the muscular system. A skeletal muscle consists of connective tissue, skeletal muscle tissue, blood vessels, and nerves. When you see marbling in a steak, you are actually viewing the connective tissue. The red portion of a steak is the muscle tissue.

Production of Energy for Muscle

Because a lot of adenosine triphosphate (ATP)-a type of chemical energy- is needed for sustained or repeated muscle contractions, a muscle cell must have multiple ways to store or make this substance. Muscle cells make this energy in three ways: 1. Creatine phosphate production. Creatine phosphate production is a rapid way for a muscle to produce energy. When ATP is used during muscle contraction, it loses phosphate and, therefore energy. Imagine a desk toy that has five ball bearings suspended by strings. You create potential energy by lifting one of the ball bearings away from the others. When you release the ball bearing- breaking the bond between your fingers and the ball- the potential energy is released. 2. Aerobic respiration- an energy-forming biochemical process that requires oxygen-uses the body's store of glucose to make ATP. A cell breaks down glucose into pyruvic acid using oxygen. The pyruvic acid is further converted into acetyl coenzyme A, which begins a series of reactions known as the Krebs cycle, or citric acid cycle. The oxygen needed for this method is stored in the muscle pigment called myoglobin, which also gives muscles its pinkish color. 3. Lactic acid production occurs when a cell is low in oxygen and must convert pyruvic acid to lactic acid. This conversion produces a small amount of ATP for the cell, but because lactic acid is a waste product, it must be released from the cell.

Muscle that moves the forearm:

Biceps brachii- muscle flexes the arm at the elbow Brachioradialis- this muscle flexes the forearm at the albow Triceps brachii-muscle extends the arm at the elbow supinator- Muscle rotates the forearm laterally Pronator teres- this muscle rotates the forearm medially

Which of the following is a rapid way for muscles to produce energy?

Creatine phosphate production

Match the methods for producing muscle energy with their descriptions.

Creatine phosphate production - ATP loses a phosphate Aerobic respiration- the process uses glucose and oxygen Lactic acid production- Pyruvic acid is converted to lactic acid

Respiratory Sytem

Diaphragm- this muscle seperates the thoracic cavity from the abdominal cavity; its contraction causes inspiration (breathing in) External and internal intercostals- the contrations of these muscles expand and then lower the ribs during breathing

Which of the following is a thin covering that is just deep to the fascia of a muscle and surrounds the entire muscle?

Epimysium

Muscles of the abdominal wall

External and internal obliques which compress the abdominal wall Transverse abdominis also compresses the abdominal wall Rectus abdominis acts to flex the vertebral column and compresses the abdominal wall Transverse abdominis Obliques

Tissue covering associated with skeletal muscles

Fascia-connective tissue loacted just below the skin that helps support and hold together muscles, bones, nerves, and blood vessels. Tendon- Tough, cord-like structure made of fibrous connective tissue that connects mescles to bones. Aponeurosis-tough, sheet-like structure made of fibrous connective tissue that typically attaches muscles to other muscles Epimysium- A thin covering that is just deep to the fascia of a muscle. It surrounds the entire muscle Perimysium- a sheath of connective tissue surrounding a group of 10 to 100 muscle fibers. This grouping of muscle fibers is called a fasicle Endomysium is the connective tissue that surrounds the individual muscle cells

Cardiac Muscle

Groups of cardiac muscle are connected to each other though intercalated discs- discs with tunnels that physically connect the cardiac muscle cells. These discs allow the fibers in each group to contract and relax toogether- a design that allows the heart to work as a pump. First, the atria (holding chambers) contract and relax together; then the ventricles (pumping chambers) contract to send blood to the lungs and body, after which they relax and the cycle starts again. Cardiac muscle is also self-exciting, which means that it does not need nerve stimulation to contract. Nerves obly speed up or slow down contraction of the heart. Like smooth muscle, cardiac muscle responds to two neurotransmitters-acetylcholine and norepinephrine. Acetylcholine slows the heart rate and norepinephrine speeds it up.

Control of Body Openings and Passages

In addition to providing important structural support for your bones and joints, muscles also form valve-like strucuture called sphincters around various body opening and passages. These spincters control the movement of substances into and out of these passages.

Attachments and Actions of Skeletal Muscles

In order for skeletal muscle to produce movement, it must cross a joint and have at least two attachmemts ton bone- one to the bone proximal to the joint and the second distal to the joint, Typically, one of the bones is more movable than the other when the muscle contracts. These attachments are known as the origin and insertion, An origin is an attachment sire for the less movable bone during muscle contraction. An insertion is an attachment site for the more movable bone during muscle contration.

Which of the following accumulates during muscle fatigue?

Lactic acid

Attachment and Actions of Skeletal Muscles

Most of the time, body movement is not produced by only one muscle but by a group of muscles. However, one muscle is responsible for most of the movement; this muscle is called the prime mover or agonist. Other muscels help the prime mover by stabilizing joints; these muscles are called synergists. An antagonist is a muscle that produces a movement oppostie to the prime mover. When the prime mover contracts, the antagonist must relax in order to produce a smooth body movement. The synergist muscles are the brachialis and brachioradialis. The antagonist is the triceps brachii because its action is to extend the arm at the elbow. When the prime mover and synergists contact, the agonist relaxes; when the antagonist contracts, the prime mover and synergists relax.

What structures hold bones tightly together with the purpose of providing joint stability?

Muscles

Stability

Muscles are holding your bones tightly together so that your joints remain stable. There are also very small muscles holding your vertebrae together to stabilize your spinal cord.

Muscles of the Pectoral Girdle

Muscles that move the pectoral girdle (shoulder): Trapezius- muscle that raises the arms and pulls the shoudlers downward Pectoralis minor- muscle that pulls the scapula downward and raises the ribs

Which neurotransmitters affect cardiac muscle?

Norepinephrine Acetylcholine

Muscles of the Wrist, Hand, and Fingers

Palmaris longus-flexes the wrist Extensor carpi ulnaris-extends the wrist Extensor digitorum-extends the fingers but not the thumb

Arm Muscles

Pectoralis major- muscle pulls the arm across the chest; also rotates and adducts the arms Latissimus dorsi- muscle acts to extend, adduct, and rotate the arm inwardly Deltoid- muscle acts to abduct and extend the arm at the shoulder Subscapularis- muscle rotates the arm medially Infraspinatus- rotates the arm laterally

Skeletal Muscle

Skeletal muscle fibers respond only to the neurotransmitter acetylcholine, which causes skeletal muscles to contract. Once contraction has occurred, skeletal muscles release an enzyme called acetylcholinesterase, which breaks down acetylcholine, This allows the muscle to relax. These muscles are also responsible for body movement, posture, and heat generation through shivering.

Movement

Skeletal muscles are attached to bones by tendons. Because skeletal muscles cross joints, when these muscles contract, the bones they attach move. This allows for various body motions, such as walking or waving your hand. Facial muscles are attached to the skin of the face; when they contact, different facial expressions are produced, such as smiling or frowning. Smooth muscles is found in the walls of

Muscles in the Head

Sternocleidomastoid is a muscle that pulls the head to one side and pulls the head to the chest Splenius captits is a muscle that rotates the head and allows it to bend to the side

Muscle Cells and Tissue

There are three types of muscles of tissue: skeletal, smooth, and cardiac. Muscle tissue is made of muscle cells, Muscle cells, or myocytes, which are called muscle fibers because of their long lengths. The cell membrane of a muscle fiber is called a sarcolemma. The cytoplasm of this cell type is called sarcoplasm, and the endoplasmic reticulum is called sarcoplasmic reticulum. Most of the sarcoplasm is filled with ling structures called myofibrils. It is the arrangement of the actin and myosin filaments in myofibrils that produces the striations, or stripes, observed in skeletal and cardiac muscle cells. Muscle fibers are controlled by motor neurons that release chemical substances called neurotransmitters, such as acetylcholine, dopamine, and epinephrine, onto the fibers.

Smooth Muscle

There are two types of smooth muscles: multi-unit and visceral. Multi-unit smooth muscle is found in the iris of the eye and walls of blood vessels. This muscle type contracts in response to neurotransmitters and hormones. Visceral smooth muscle contains sheets of muscle cells that closely contact each other. It is found in the walls of hollow organs such as the stomach, intestines, bladder, and uterus. Muscle fibers in visceral smooth muscle respond to neurotransmitters, but they also stimulate each other to contract, so the muscle fibers tend to contract and relax together. This type of muscle produces an action called peristalsis. Peristalsis is a rhythmic contraction that pushes substances through tubes of the body. For example, peristalsis in the lower two-thirds of the esophagus moves the bolus of food through the stomach; peristaltic muscle movements in the fallopian tubes propel the ovum (egg) through tubes toward the uterus.

Muscles of the Ankle, Foot, and Toes

Tibialis anterior- inverts the foot and points the foot up (doriflexion) Extensor digitorum longus-this muscle extends the toes and points the foot up

Heat Production

When muscles contract, heat is realeased, which helps the body maintain a normal temperature.

acetylcholine

a neurotransmitter released by the parasympathetic nerves onto organs and glands for resting and digesting.

striations

bands produced from the arrangements of filaments in myofibrils in skeletal and cardiac muscle cells

The ______ separates the thoracic cavity from the abdominal cavity.

diaphram

A(n) ______ disc connects groups of cardiac muscles. This disc allows the fibers in that group to contract and relax together.

intercalated

Muscle Fatigue

is a condition in which a muscle has lost its ability to contract. It usually develops because of an accumulation of lactic acid. It also can occur if the blood supply to a muscle is interrupted or if a motor neuron loses its ability to release acetylcholine onto muscle fibers. Cramps-painful, involuntary contractions of muscles- can accompany muscle fatigue. For this reason, if you have just finished an intense workout, it is important to replenish your electrolytes by drinking and eating foods that are good sources of sodium, potassium, and calcium.

myofibrils

long structures that fill the sarcoplasm of a muscle fiber

Oxygen Debt

occurs when skeletal muscle is used strenously for several minutes. When pyruvic acid is converted to lactic acid for energy production, the lactic acid builds yp and causes mescle fatigue and soreness. The lactic acid is taken to the liver via the bloodstream to be converted back into glucose, which requires more energy. The amount of oxygen the liver cells need to make enough ATP for this conversion results in the oxygen debt. This process explains why your body still burns energy even after you are done exercising.

The rhythmic muscular contractions that move a substance through a tract, such as food through the digestive tract and an ovum through a fallopian tube, is known as ______.

peristalsis

sarcolemma

the cell membrane of a muscle fiber

sarcoplasm

the cytoplasm of a muscle fiber

sarcoplasmic reticulum

the endoplasmic reticulum of a muscle fiber