The Muscular System Flashcards
What are the functions of muscles?
-Movement
-Stability
-Control of body openings and passages
-Production of heat
What are sphincters?
They are valve-like muscular structures that control the passage of substances into and out of organs such as the stomach and bladder.
How are skeletal striated muscles attached to bones?
They are attached to bones through tendons
What happens when skeletal muscles contract?
They cause movement
What happens when smooth muscle contracts?
It causes movement of the contents in the organs eg food material moves through the intestinal tract
What happens when cardiac muscle contracts?
The contraction causes blood to pump blood into blood vessels
How do muscles provide stability to the body?
Skeletal muscles hold bones very tightly and hold the vertebrae together to stabilize it.
How do muscles produce heat in the body?
They produce heat by releasing heat when muscle contraction occurs. This helps keep the body at a healthy temperature.
What are the three types of muscle tissue?
- skeletal striated muscle
- smooth muscle tissue
- cardiac striated muscle
What is muscle tissue made of?
Muscle cells called myocytes
What are the muscle cells of skeletal striated tissue called?
They are called muscle fibers
Why are the cells of skeletal striated muscle called muscle fibers?
It is because they are long in length
What is the cell membrane of a muscle cell called?
It is called a sarcolemma
What is the cytoplasm of a muscle cell called?
It is called a sarcoplasm
What is the endoplasmic reticulum of a muscle cell called?
It is called a sarcoplasmic reticulum
What is most of the sarcoplasm in skeletal striated cells filled with?
It is filled with long structures called myofibrils
What produces striations in the muscle tissue?
It is the arrangement of actin and myosin filaments in myofibrils that produces striations
What substances control muscle cells?
Motor neurons that release Chemical substances known as neurotransmitters
What is the only neurotransmitter that muscle fibers respond to?
Acetylcholine
Describe the action of acetylcholine on muscle contraction
Acetylcholine causes skeletal muscle to contract.
Describe the action of acetylcholinesterase on muscle relaxation
When contraction occurs, an enzyme called acetylcholinesterase in the muscles breaks down the acetylcholine which allows the muscles to relax
What are the characteristics of the contractions in skeletal striated muscles?
They are fast to contract and relax
What are the characteristics of contractions in smooth muscle tissue?
They are slow to contract and relax
What are the characteristics of cardiac striated muscle?
They are groups of muscle cells that contract as a unit
What are the two types of smooth muscle tissue?
Multi-unit and visceral
Where is multi-unit smooth muscle found in the body?
It is found in the iris of the eye and the walls of the blood vessels
How does multi-unit smooth muscle contract?
It contracts in response to neurotransmitter and hormones
What is visceral smooth muscle?
Visceral smooth muscle is sheets of muscle cells that closely contact with each other
What is the shape of smooth muscle?
It has a fusiform shape like a football or a spindle
What connective tissue surrounds smooth tissue?
Endomysium
What is the shape skeletal muscle?
It has a long cylindrical shape
What is the shape of cardiac muscle?
It is irregularly branched
What is the shape of cardiac muscle?
It is irregularly branched
What do visceral smooth muscle cells respond to?
They respond to neurotransmitters
Is smooth muscle tissue voluntarily or involuntarily controlled?
It is involuntarily controlled, we do not consciously control it, it is controlled via the autonomic nervous system.
What is different about the structure of smooth muscle compared to skeletal and cardiac muscle?
Smooth muscle does not have sarcomeres and myofibrils, because of this is lacks the striations of cardiac and skeletal muscle.
What filaments exist in all three muscle types?
Myosin and Actin filaments
What are the dot like structures that connect the net like structure running through out the muscle fiber?
They are called dense bodies
What do the dense bodies attach to in the cell?
They attach to the sarcolemma(cell membrane surrounding a muscle cell)
What is another role played by the dense fibers?
They allow for attachment of intermediate filaments such as desmin and vimentin.
What two neurotransmitters are involved in smooth muscle contraction?
Acetylcholine and norepinephrine
What is the model used to describe muscle contraction called?
It is called the sliding filament model of muscle contraction.
How many nuclei do smooth muscle tissue have?
They only have one nucleus
What are tendons?
Connective tissues that attach to the periosteum of bones.
What are aponeuroses?
Aponeuroses are flat, sheet like tendons that attach muscles to the periosteum of bones or to the skin.
Why are a woman’s muscles smaller than a man’s?
Women have fewer muscle fibers and less ability to store glycogen and convert it into energy.
What are the three types of filaments that a sarcomere contains?
- Thick myosin filaments
- Thin Actin filaments
- Elastic titin (connectin) filaments
Describe the structure of thick (myosin) filaments in sarcomeres.
Myosin filaments are shaped like two golf clubs twisted together:
-the handles or the golf clubs form the tails of the molecules and point towards the sarcomere
-the heads of the clubs for the heads of the molecules and are called myosin heads or cross-bridges. They extend towards the thin filaments.
-The molecules lie parallel to each other
What three proteins do thin filaments contain?
- Actin
- Tropomyosin
- Troponin
Describe the structure of thin filaments in sarcomeres.
-The molecules are irregularly shaped but appear together as a chain of twisted molecules
-Each molecule has a myosin-binding site where myosin heads bring about contraction
What happens to the myosin-binding site when a muscle is relaxed?
The site is blocked by a tropomyosin-troponin complex so that myosin cannot bind to them.
What protein do elastic filaments contain?
They contain the protein titin(connectin)
What is the purpose of the protein titin(connectin) in elastic filaments?
It helps to stabilize the position of the thick filaments
What are the two regions that sarcomeres are made up of?
- A-band
- I-band
What is the purpose of the two regions of sarcomeres?
They give striated muscles their striated appearance
Describe the appearance of A-band region of sarcomeres.
-It is darker
-composed mainly of thick filaments with only a few thin filaments
-In the center of the A-band is a narrow H-zone that contains thick filaments only
-the H-Zone is divided by an M-Line of protein molecules that hold the thick filaments together
Describe the I-band of sarcomeres.
-it is a lighter zone composed of thin filaments only.
How are sarcomeres separated from each other?
They are separated from each other by Z-discs which are narrow regions of dense material.
Describe the role of ATP in muscle contraction.
ATP is attached to ATP binding sites in myosin heads.
ATP is split into ADP and P meaning energy has been transferred from ATP to the myosin heads.
Myosin heads are in an excited state and ready to bind to the actin molecules when space becomes available
Describe the role of nerve impulses from the central nervous system in muscle contraction.
Nerve impulses trigger acetylcholine release which then triggers a muscle action potential that travels along the sarcolemma and caused the release of calcium which is stored in the sarcoplasmic reticulum.
What role does calcium play in muscle contraction?
Calcium binds with troponin on the myosin-binding site and causes the tropomyosin-troponin complex to move away to other sites. This frees up space for the myosin on the thick filaments to bind with the actin filaments binding site.
What is a a power stroke in muscle contraction?
A power stroke occurs when the myosin heads bind to the myosin-binding site on the actin and change their shape by swiveling their heads towards the center of the sarcomere.
What is the effect of the power stroke in muscle contraction?
It causes the thin filaments to draw past the thick filaments. The thin filaments slide inward toward the H-zone , the thick filaments remain in place. The inward sliding causes the Z-discs to come towards each other and the entire sarcomere shortens.
Do the lengths of the thin and thick filaments change during contraction?
No, they do not
What happens after the power stroke?
ATP binds to the myosin heads at the ATP binding site causing the heads to detach themselves from the actin
Where does the calcium needed for muscle contraction come from?
It comes from the sarcoplasmic reticulum
What two processes need to happen for muscles to relax?
- Acetylcholine is broken down
- Calcium levels drop
What causes the breakdown of acetylcholine in the muscles?
An enzyme called acetylcholinesterase breaks down the acetylcholine
What happens when acetylcholine is broken down?
The breakdown of acetylcholine by acetylcholinesterase stops any further muscle action potential. Calcium is no longer released
What happens when the calcium levels drop to cause muscle relaxation?
There is no longer enough calcium to bind with the troponin. The tropomyosin-troponin complex moves back over the myosin binding sites in the actin of the thin filaments, preventing the myosin heads from the thick filaments from binding with the actin.
What is atony?
Atony is a lack of muscle tone
What is atrophy?
Atrophy is the wasting away of muscles; muscles decrease in size
What is hypotonia?
A loss of muscle tone; muscles appear loose and flattened and are described as hypotonic
What is hypertonia?
An increase in muscle tone; muscles appear stiff or rigid, and are described as hypertonic
What are the two types of physical contractions that most physical activity fall into?
Isotonic and isometric contractions
What are isotonic contractions?
Isotonic contractions are regular contractions in which muscles shorten and create movements, while the tension in the muscle remains constant.
What are the two types of isotonic contractions ?
- Concentric contractions
- Eccentric contractions
What are concentric contractions?
Concentric contractions occurs when the muscle shortens and generates a movement that decreases the angle on the joint. Example curling a bicep towards you
What are eccentric contractions?
Eccentric contractions are contractions which lengthen the muscles and increase the angle of the joint. Eg stretching a bicep away from you
What are isometric contractions?
In isometric contractions, the muscle contracts but it does not shorten and no movement is generated. A plank is an example as you are not shortening ing or lengthening muscles
From where do muscles obtain the energy needed to contract?
From ATP
What are the three ways that muscles obtain ATP?
- The phosphates system
- Glycolysis
- Aerobic respiration
What is the phosphagen system?
Muscles store a small amount of ATP in their fibers and are able to convert it into energy.
What is a downside of the phosphagen system?
It only provides enough energy for around 15 seconds of maximal muscular activity.
What is glycolysis?
Glycolysis is the breakdown of glucose in the muscles without the presence of oxygen.
What is another name for glycolysis?
Anaerobic respiration
What is glucose broken down into through glycolysis?
It is broken down into pyruvic acid and ATP.
What happens to the pyruvic acid and ATP broken down by glycolysis?
The ATP is used by the muscles and the pyruvic acid enters mitochondria of the the muscle fiber and is further broken down complete in the presence of oxygen
What happens if there is not enough oxygen to completely break down the pyruvic acid?
It is converted into lactic acid
What happens to the lactic acid that is produced by the muscles?
It diffuses into the blood and can be used by the heart muscle fibers, kidneys and liver to produce ATP.
What happens when lactic acid accumulates in the muscle tissues and blood?
It causes muscle soreness and fatigue
What is aerobic respiration?
Aerobic respiration occurs in the presence of oxygen. Pyruvic acid is completely broken down into carbon dioxide, water, ATP and heat
What is another name for aerobic respiration?
Cellular respiration or biological oxidation
What are the benefits of aerobic respiration?
It provides energy for activities longer than ten minutes as long as there is enough oxygen and nutrients
Where do muscles get their glucose from?
Carbohydrates which are broken down into glucose and stored in the body as glycogen.
Where is glycogen stored in the body?
It is stored in the liver and the muscles
Where do the muscles get their oxygen from?
- It is stored in the muscles as myoglobin
- It is stored in the blood in the form of hemoglobin
Why do muscles experience fatigue?
- An insufficient supply of oxygen or glycogen
- A build up of lactic acid
- A failure of action potentials to release adequate acetylcholine
What are the three different types of muscle fibers?
- Fast oxidative
- Slow oxidative
- Fast glycolytic
Why do runners or other athletes breathe fast and heavy after a race?
They do something knows as recovery oxygen consumption. The heavy breathing:
- restores ATP reserves,
- repairs tissues,
- removes accumulated lactic acid and 4. cools the body down.
How does the color of muscles indicate the amount of myoglobin in them?
Red muscle fibers have more myoglobin and white muscle fibers have a low myoglobin content
What is the appearance of slow oxidative muscle fibers?
They are red in color and small in appearance
What is the oxygen supply like for slow oxidative muscle fibers?
It contains large amounts of myoglobin, many mitochondria and many blood capillaries. The oxygen supply is high.
What is the ATP production like in slow oxidative muscle fibers?
They generate ATP by aerobic processes
What is the contraction velocity of slow oxidative muscle fibers?
They split ATP slowly and therefore have a slow contraction velocity
What is the fatigue resistance of slow oxidative muscle fibers?
They are very resistant to fatigue
What type of activities do slow oxidative muscles perform?
They are good for maintaining posture and endurance activities
What is the appearance of fast oxidative muscle fibers?
Their color is red to pink and they are medium in size
What is the oxygen supply like in fast oxidative muscle fibers?
They contain large amounts of myoglobin, many mitochondria, and many blood capillaries. Good oxygen supply
What is the ATP production in fast oxidative muscle fibers?
They generate ATP by aerobic processes
What is the contraction velocity of fast oxidative muscle fibers?
They split ATP quickly and therefore have a fast contraction velocity
What is the fatigue resistance of fast oxidative muscle fibers?
They are resistant to fatigue but not as much as slow oxidative muscle fibers
What type of activities do fast oxidative muscle fibers perform?
Walking and running
What is the appearance of fast glycolytic muscle fibers?
They are white in color and are the largest muscle fibers
What is the oxygen supply of fast glycolytic muscle fibers?
They have a low myoglobin content,
Few mitochondria
Few blood capillaries
Oxygen supply is low
How do fast glycolytic muscle fibers generate ATP?
They generate ATP by anaerobic processes (glycolysis);
cannot supply muscle with ATP continuously
What is the Contraction velocity of fast glycolytic muscle fibers?
Due to their large diameter they split ATP very quickly and therefore have a strong contraction velocity.
What is the fatigue resistance of fast glycolytic muscle fibers?
They fatigue easily
What activities do fast glycolytic muscle fibers perform?
Fast movements, such as throwing a ball
How do muscles produce movement?
A muscle attaches itself to two bones that for a joint, when the muscle contracts, it pulls the movable bone towards the stationary bone.
How many attachment points do muscles usually have?
All muscles have at least two attachment points
What is the origin attachment point?
It is the point where a muscle attaches to the stationary bone
What is the insertion point?
It is the point where a muscle attaches to the moving bone. During contraction the insertion usually moves towards the origin
What is a unique point about the movement of muscles?
Muscles only shorten when they contract, therefore they can only pull and never push.
How is movement in the body defined by the contraction of muscles?
Movement is the action of two muscles acting together or against each other, one muscles contracts to bend the elbow another contracts to make the elbow straight again.
What are the pairs that muscles at the joints are usually arranged in?
They are usually arranged in pairs of flexors-extensors and abductors- adductors
What is the muscle responsible for causing a particular movement called?
It is called the prime mover or agonist.
What is the muscle that opposes the movement of the prime mover or agonist called?
The antagonist, it relaxes and lengthens in a way that ensures that the movement performed by the prime mover is smooth.
What are the additional muscles at the joint that ensure a steady movement and help the prime mover function effectively called?
They are called synergists and they are usually found alongside the prime mover
What are the specialized synergistic muscles that stabilize the bone of the prime mover’s origin so that it can act efficiently?
They are called fixators or stabilizers
What is flexion?
Flexion is bending a body part e.g bending the palm inward
What is extension?
Extension is straightening a body part eg holding the palm out straight
What is hyperextension?
Extending a body part past the healthy anatomical position eg bending the palm backward
What is dorsiflexion?
Moving the ankle to raise the top of the foot towards the leg
What is plantar flexion?
Moving the ankle to raise the heel and stand on the tips of your toes
What is abduction?
Moving a body part away from the midline of the body eg taking a step to the left or right
What is addiction?
Moving a body part to the midline of the body eg moving leg back to the center after taking a step to the left or right
What is rotation?
Rotation is twisting the a body part eg turning head side to side
What is pronation?
Turning the palm so the palm is facing downward and the back of the hand of facing forward
What is supination?
Turning the palm so that the palm of the hand is facing upward.
What is inversion?
Turning the sole of the foot inward
What is eversion?
Turning the sole of the foot outward
What is retraction?
Moving a body part back eg moving chin towards chest
What is protraction?
Moving a body part outward eg sticking chin out
What is elevation?
Vertically lifting a body part eg lifting shoulders up
What is depression?
Vertically lowering a body part eg lowering shoulders
What are the two types of fascia available?
- Deep fascia
- Superficial fascia
Where in the body is deep fascia found?
It is found between the muscles
Where in the body is superficial fascia found?
It is found under the skin
What is another name for superficial fascia?
Hypodermis
What are the two ways that skeletal muscle attaches to a bone?
- Direct attachment
- Indirect attachment
What is direct attachment of muscles to bone?
Muscle fibers merge with the periosteum of the bone, forming a strong bone.
What is indirect attachment of muscles to bone?
The epimysium extends past the muscle as a tendon(a strong fibrous cord). The tendon merges with the periosteum of the bone.
Can muscle attach to other muscle?
Yes. The muscle epimysium extends as an aponeurosis and fuses with the covering of the other muscle or attaches to bone.
