LO 7 Flashcards
Movement is caused by the ability of the muscle cells, called fibers, to _________
Shorten and contract - all muscle cells specialize in contraction (shortening)
Muscle cells shortened by converting ______ into _______
- Chemical energy obtained from food
- Mechanical energy
What are the three types of muscle tissue that exist in the body?
- Skeletal
- Cardiac
- Smooth
Describe skeletal muscle
- Also called striated or voluntary muscle
- Represents 40% - 50% of body weight
- Attached to bones
- Microscopic striations
- Voluntary contractions
- Multi-nucleated cell/fiber (arranged around periphery of cell)
Describe cardiac muscle
- Composes the bulk of the heart
- Cells branch frequently and are joined to each other by unique dark bands called intercalated discs - discs enable interconnected nature of cardiac muscle cells, allowing heart to contract efficiently as a unit
- Involuntary control
- Many nuclei that are centrally located
Describe smooth muscle
- Also called non striated, involuntary, or visceral muscle
- Appears smooth under the microscope
- Found in walls of hollow, visceral structures - e.g.digestive tract, blood vessels, and uterus
- Involuntary control
- Long, narrow spindle shaped cells
- Single, centrally located nucleus
Describe the structure and attachment of skeletal muscle
- Composed mainly of striated / skeletal muscle cells ‘fibers’ and connective tissue
- They extend from one bone across a movable joint to another bone
- One bone is typically more stationary than the other in any given moment of movement
______ is the attachment point of the muscle to the bone that remains relatively fixed when movement at the joint occurs
Origin
______ is the point of attachment to the bone that moves when a muscle contracts
Insertion
The main part of skeletal muscle is called the ______
Body
Describe tendons
- Attach muscle to bones
- Strong, dense chords of fibrous connective tissue
- Some enclosed in synovial lined tubes called tendon sheaths
- Lubricated by synovial fluid
What are bursae?
- Small, synovial-lined sacs containing a small amount of synovial fluid
- Located between tendons and underlying bone
- Decrease friction at the joint
Describe the microscopic structure of skeletal muscle
- Each tissue consists of specialized contractile cells called fibers
- Each fiber contains two kinds of very fine, thread like structures - thick myofilaments made of myosin, thin myofilaments made of actin
Thick myofilaments are made of ______
Myosin
Thin myofilaments are made of ______
Actin
What is the basic, functional, contractile unit of skeletal muscle?
Sarcomere
Describe sarcomeres
- Basic functional unit of skeletal muscle
- Contains numerous actin and myosin myofilaments - the arrangement gives the appearance of dark and light stripes under a microscope
- They are separated by dark bands called z lines or discs
Explain the sliding filament model
- During contraction, thick and thin myofilaments (myosin and actin) attach to one another by forming ‘cross bridges’
- Cross bridges act as levers to pull the myofilaments past each other
- As muscle contracts, myofilaments slide past each other
- Contraction requires calcium (for crossbridge formation) and ATP (for energy)
What are the three primary functions of skeletal muscle?
- Movement
- Posture / muscle tone
- Heat production
Describe how skeletal muscles produce movement
- Muscles produce movement by ‘pulling’ on bones
- As a muscle contracts, it pulls the insertion bone closer to the origin bone
- Movement occurs at the joint between the origin and the insertion
- Groups of muscles usually contract / relax in a coordinated way to produce a single, smooth, coordinated movement - muscles contained in the group include the prime mover, synergist, and antagonist
This muscles contraction is mainly responsible for producing movement
Prime mover (e.g. if the biceps are prime movers the brachialis act as synergist and the triceps act as antagonists)
This muscles contraction helps the prime mover produce a movement
Synergist (e.g. the brachialis is a synergist for the biceps)
This muscles actions oppose the action of the prime mover in a movement (e.g.produces a movement opposite to the prime mover and synergist)
Antagonist (e.g. the triceps are antagonists for the biceps)
Describe skeletal muscles role in posture
- Maintaining posture is made possible thanks to a specialized contraction called a tonic contraction
- Only a few muscles fibers shortened/contract at one time - the muscle as a whole doesn’t shorten and contract
- For purposes of posture, movement is not produced
- The muscles do hold in position, maintaining muscle tone, which is referred to as posture
- Good posture balances the distribution of weight and counteracts gravity - reduces strain on muscles, tendons, ligaments, Bones and keeps our head from flopping forward
- Poor posture causes fatigue and may lead to deformity
Describe skeletal muscle’s role in heat production
- Survival depends on the ability to maintain constant body temperature - fever is an elevated body temperature often a sign of illness, hypothermia is a reduced body temperature
- Contraction of muscle fibers produces most of the heat required to maintain normal body temperature
- Energy for contraction comes from breaking ATP bonds. Most energy is used for contraction but some is lost as heat which equals body temperature
Describe muscle fatigue
- Caused by repeated muscle stimulation without adequate rest
- Leads to reduced strength of muscle contraction (can eventually lead to loss of muscles ability to contract)
- Repeated muscular contraction deplete cellular ATP stores and outstrips the ability of the blood supply to replenish oxygen and nutrients to make more ATP
Contraction in the absence of adequate oxygen produces ______, which contributes to muscle soreness
Lactic acid
Heavy / labored breathing after exercise occurs to make up for the ______
Oxygen debt
** This is part of the continued malletabolic effort required to remove excess lactic acid that can accumulate during prolonged periods of exercise, and is the body trying to bring the cell’s energy and oxygen reserves back to normal levels
Muscle functioning depends on the functioning of many other parts of the body, including:
- Bones and joints (most muscles cause movement by pulling on Bones across movable joints)
- Respiratory, circulatory, nervous, and skeletal systems play an essential role in producing normal movements
- Certain diseases can negatively affect our ability to move, even if our muscles are healthy - MS, stroke, spinal cord injury, arthritis
Describe the motor unit
- Stimulation of a muscle by a nerve impulse is required for the muscle to contract and produce movement. The stimulation involves the following structures
- Motor neuron - specialized nerve fiber that transmits an impulse to a muscle, causing contraction
- Neuromuscular junction - specialized point of contact between a nerve ending and the muscle fiber it innervates
- Motor unit - is the combination of a motor neuron with the muscle cells it innervates
What happens at the neuromuscular junction?
- Neurotransmitters are released by the motor neuron in response to a nerve impulse
- Neurotransmitters kick off a Cascade of actions inside the muscle fibers that initiate a contraction
What does it mean that muscles have a threshold stimulus?
- There is a minimal level of stimulation required to cause a muscle fiber to contract (does not contract until this level of intensity is reached)
- Once stimulated by a threshold stimulus, a muscle fiber will contract completely, a response called all-or-none
- Different muscle fibers in a muscle are controlled by different motor units with different thresholds, so while individual muscle fibers always respond all or none to a threshold stimulus, the muscle as a whole doesn’t. This allows the muscle to perform contractions that are specific to different weight loads
In addition to tonic contractions, there are four other types, what are they?
- Twitch
- Tetanic
- Isotonic
- Isometric
Describe twitch contractions
- Quick, jerky response to stimulus
- Considered a lab phenomena and not related to normal muscle activity
- Seen in isolated muscle fibers
- Single contraction of muscle fibers caused by a single threshold stimulus
Describe tetanic contractions
- Sustained, study muscular contractions
- Caused by a series of stimuli bombarding a muscle in rapid succession
- This series of stimuli join forces to produce a sustained / prolonged contraction referred to as tetanus (Greek for ‘taut’, e.g. lockjaw)
Describe isotonic contractions
- Produces movement at a joint
- Muscle changes length, but tension stays the same - concentric contraction, eccentric contraction
- Most types of body movements are isotonic contractions
- “Iso” mean same and “tonic” means tone or tension
_______ is when the muscle shortens - insertion end of muscle moves towards the point of origin
Concentric contraction
_______is when the muscle lengthens and produces tension so insertion moves away from the point of origin
Eccentric contraction
Describe isometric contractions
- Tension within muscle increases but muscles don’t shorten and there is no movement (e.g.pushing against the wall)
- Muscle length is relatively the same regardless of whether the muscle is contracted or relaxed
- Repeated isometric contractions make muscle stronger
- “Iso” means the same and “metric” means length or measure
Describe the effects of exercise on skeletal muscle
- Regular, properly practiced exercise improves muscle tone and posture
- Results in more efficient heart and lung functioning
- Reduces fatigue
- Helps muscle tissue develop
- Helps maintain a healthy weight (muscles have a higher metabolic rate than fat)
Prolonged inactivity causes disuse, also known as ______
Atrophy
Regular exercise increases muscle size, called ______
Hypertrophy
What does exercise involving contractions of muscles against heavy resistance (i.e. strength training) result in?
- Increases number of myofilaments in each muscle fiber
- Increases the total mass of the muscle
- Does not increase the number of muscle fibers
Describe the effects of endurance training
- Endurance training is exercise that increases the muscle’s ability to sustain moderate exercise over long periods of time - also called aerobic training
- Allows more efficient delivery of oxygen and nutrients to a muscle via increased blood flow
- Increases the number of mitochondria and blood vessels in a muscle
- Does not usually result in muscle hypertrophy
Name the types of movements produced by skeletal muscle contractions
- Flexion
- Extension
- Abduction
- Adduction
- Rotation
- Circumduction
- Supination and pronation
- Dorsiflexion and plantar flexion
- Inversion and eversion
_____ is movement that decreases the angle between two bones at their joint (i.e. bending)
Flexion
______ is movement that increases the angle between two bones that their joint (i.e. straightening)
Extension
______ is movement of a part away from the midline of the body
Abduction
______ is movement of a part toward the midline of the body
Adduction
______ is movement around a longitudinal axis (e.g. shaking your head no)
Rotation
________ moves apart so that it’s distal end moves in a circle
Circumduction
_______ is the movement of the Palm turning up to the anterior position (rotation from the forearm)
Supination (anterior position)
______ is movement of the Palm to face down (rotation at the forearm)
Pronation (posterior position)
______ is the elevation of the dorsum, also known as the top of the foot
Dorsiflexion
______ is when the bottom of the foot is directed downward
Plantar flexion
______ is when the bottom of the foot faces toward the midline of the body
Inversion
______ is when the bottom of the foot faces toward the side of the body
Eversion
The trapezius can be found _____
In the head and neck
The pectoralis major can be found in the ______
Chest
The latissimus dorsi (lats) can be found in the
Upper arm/back
Where is the deltoid muscle found?
Upper arm / shoulder cap
The biceps brachii can be found in the ______
Upper arm at the front
The triceps brachii can be found in the _____
Upper arm at the back
The iliopsoas can be found in the ______
Thighs
The gluteus maximus is also known as the _______
Buttocks
The adductor muscles are found in the _______
Thighs
The hamstring muscles are found in the _______
Back of the upper leg
The quadriceps are found in the ______
Front of the upper leg
The gastrocnemius is also known as the ______
Calf
The abdominal obliques can be found in the _______
Abdomen/waste
What does the trapezius do?
- Extends and rotates the head and neck
- Shrugs the shoulders (scapula) up and down
- Squeezes the shoulder blades together
What does the pectoralis major do?
- Adducts the arm in the medial direction (think of the pec machine at gym)
- Extends the arm in the anterior direction at the shoulder from a flexed position
What does the latissimus dorsi do?
- Extends the upper arm posteriorly from the shoulder
What does the deltoid do?
Abducts the upper arm
What does the biceps brachii do?
- Flexes the forearm
What does the triceps brachii do?
- Extends the forearm at the elbow
What does the iliopsoas do?
- Flex’s thigh forward towards the trunk
What does the gluteus maximus do?
Extends thigh posteriorly
What do the adductor muscles do?
Adduct the thighs
What do the hamstring muscles do?
Flexes the lower leg
Which of the quadriceps do?
Extends the lower leg
What does the gastrocnemius do?
- Largest muscle of the calf
- Plantar flexes ankle
What do the abdominal obliques (internal and external) do?
- Compresses abdomen
- Other movements around the waist - twists, side bends, sit-ups
