2nd Semester - Muscular System Flashcards
_ consists of all the muscles of the body. The largest percentage of muscles in the muscular system consists of skeletal muscles, which are attached to bones and enable voluntary body movements.
muscular system
The largest percentage of muscles in the muscular system consists of _, which are attached to bones and enable voluntary body movements.
skeletal muscles
There are almost _ skeletal muscles in the human body.
650
Besides skeletal muscles, the muscular system also includes _ — which makes up the walls of the heart — and _, which control movement in other internal organs and structures.
cardiac muscle; smooth muscles
What are the organs, muscles, mainly composed of?
• muscle cells | muscle fibers (mainly in skeletal and cardiac muscle)
• myocytes (mainly in smooth muscle)
_ are long and thin cells that are specialized for the function of contracting.
Muscle cells
They contain _ that slide over one another using energy in ATP. The sliding filaments increase the tension in — or shorten the length of — muscle cells, causing a contraction.
protein filaments
_ are responsible for virtually all the movements of the body, both inside and out.
Muscle contractions
_ are attached to the bones of the skeleton. When these muscles contract, they move the body. They allow us to use our limbs in a variety of ways, from walking to turning cartwheels. Skeletal muscles also maintain posture and help keep balance.
Skeletal muscles
Smooth muscles in the walls of blood vessels contract to cause _, which may help conserve body heat.
vasoconstriction
Relaxation of these muscles causes _, which may help the body lose heat.
vasodilation
In the organs of the digestive system, smooth muscles squeeze food through the gastrointestinal tract by contracting in sequence to form a wave of muscle contractions called _. _ of smooth muscles also moves urine through the urinary tract.
peristalsis
_ is found only in the walls of the heart. When cardiac muscle contracts, it makes the heartbeat. The pumping action of the beating heart keeps blood flowing through the cardiovascular system.
Cardiac muscle tissue
Muscles can grow larger, or _. This generally occurs through increased use, although hormonal or other influences can also play a role.
hypertrophy
The increase in _ during puberty, for example, causes a significant increase in muscle size. Physical exercise that involves weight-bearing or resistance training can increase the size of skeletal muscles in virtually everyone. Exercises (such as running) that increase the heart rate may also increase the size and strength of cardiac muscle.
testosterone
The _, in turn, is the main determinant of muscle strength, which may be measured by the amount of force a muscle can exert.
size of a muscle
Muscles can also grow smaller, or _, which can occur through lack of physical activity or from starvation. People who are immobilized for any length of time — for example, because of a broken bone or surgery — lose muscle mass relatively quickly.
People in concentration or famine camps may be so malnourished that they lose much of their muscle mass, becoming almost literally just “skin and bones.” Astronauts on the International Space Station may also lose significant muscle mass because of weightlessness in space
atrophy
Many diseases, including cancer and _, are often associated with muscle atrophy.
AIDS
As people grow older, there is a gradual decrease in the ability to maintain skeletal muscle mass, known as _. The exact cause of _ is not known, but one possible cause is a decrease in sensitivity to growth factors that are needed to maintain muscle mass. Because muscle size determines the strength, muscle atrophy causes a corresponding decline in muscle strength.
sarcopenia
In both hypertrophy and atrophy, the number of muscle fibers does not change. What changes the size of the muscle fibers?
When muscle hypertrophy happens, the individual fibers become wider.
When muscle atrophy happens, the fibers become narrower.
Muscles cannot contract on their own. Skeletal muscles need stimulation from _ in order to contract.
motor neurons
The point where a motor neuron attaches to a muscle is called a _.
neuromuscular junction
Involuntary contractions of smooth and cardiac muscles are also controlled by _, but in the case of these muscles, the impulses come from the autonomic nervous system (smooth muscle) or specialized cells in the heart (cardiac muscle).
Hormones and some other factors also influence involuntary contractions of cardiac and smooth muscles. For example, the fight-or-flight hormone adrenaline increases the rate at which cardiac muscle contracts, thereby speeding up the heartbeat.
electrical impulses
Muscles cannot move the body on their own. They need the skeletal system to act upon. The two systems together are often referred to as the _.
musculoskeletal system
Skeletal muscles are attached to the skeleton by tough connective tissues called _. Many skeletal muscles are attached to the ends of bones that meet at a joint. The muscles span the joint and connect the bones.
When the muscles contract, they pull on the bones, causing them to move. The skeletal system provides a system of levers that allow body movement. The muscular system provides the force that moves the levers.
tendons
Muscles play a part in every function of the body. The muscular system is made up of over 600 muscles. These include three muscle types: ___.
smooth, skeletal, and cardiac
Only skeletal muscles are _, meaning you can control them consciously. Smooth and cardiac muscles act _.
voluntary; involuntarily
Your skeletal muscles are responsible for the movements you make. Skeletal muscles are attached to your bones and partly controlled by the central nervous system (CNS).
Mobility
_ cause short bursts of speed and strength.
Fast-twitch skeletal muscles
_ function better for longer movements.
Slow-twitch muscles
The involuntary cardiac and smooth muscles help your heart beat and blood flow through your body by producing electrical impulses. The cardiac muscle (myocardium) is found in the walls of the heart. It’s controlled by the autonomic nervous system responsible for most bodily functions.
Circulation
Your _ are made up of smooth muscles, and also controlled by the autonomic nervous system.
blood vessels
Your diaphragm is the main muscle at work during quiet breathing. Heavier breathing, like what you experience during exercise, may require accessory muscles to help the diaphragm. These can include the abdominal, neck, and back muscles.
Respiration
_ is controlled by smooth muscles found in your gastrointestinal tract.
Digestion
The digestive tract comprises the:
➢ Mouth
➢ Esophagus
➢ Stomach
➢ small and large intestines
➢ rectum
➢ anus
The digestive system also includes the liver, pancreas, and gallbladder.
Smooth and skeletal muscles make up the urinary system.
Urination
The urinary system includes the:
➢ kidneys
➢ bladder
➢ ureters
➢ urethra
➢ penis or vagina
➢ prostate
Smooth muscles are found in the uterus. During pregnancy, these muscles grow and stretch as the baby grows. When a woman goes into labor, the smooth muscles of the uterus contract and relax to help push the baby through the vagina.
Childbirth
Your eye sockets are made up of six skeletal muscles that help you move your eyes. And the internal muscles of your eyes are made up of smooth muscles. All these muscles work together to help you see. If you damage these muscles, you may impair your vision.
Vision
The skeletal muscles in your core help protect your spine and help with stability. Your core muscle group includes the abdominal, back, and pelvic muscles. This group is also known as the trunk. The stronger your core, the better you can stabilize your body. The muscles in your legs also help steady you.
Stability
Your skeletal muscles also control posture. Flexibility and strength are keys to maintaining proper posture. Stiff neck muscles, weak back muscles, or tight hip muscles can throw off your alignment. Poor posture can affect parts of your body and lead to joint pain and weaker muscles.
Posture
Posture includes these parts:
➢ shoulders
➢ spine
➢ hips
➢ knees
What are the main functions of the muscular system?
- Mobility
- Circulation
- Respiration
- Digestion
- Urination
- Childbirth
- Vision
- Stability
- Posture
The following conditions can affect your muscular system:
➢ myopathy (muscle disease)
➢ muscular dystrophy
➢ multiple sclerosis (MS)
➢ Parkinson’s disease
➢ fibromyalgia
