Chapter 8: Muscle Tissue Flashcards
What are the 4 major functional characteristics of muscles?
- Excitability
- Contractility
- Extensibility
- Elasticity
What is Excitability?
Muscle tissue has the capacity to respond to the stimulation of nervous impulses or hormones.
What is Contractility?
Muscle tissue has the capacity to shorten or contract with force.
What is Extensibility?
Muscle tissue can stretch beyond (within reason) resting length.
What is Elasticity?
Muscle tissue returns to resting length after being stretched.
What are the 3 types of muscle tissue?
- Skeletal muscle
- Smooth muscle
- Cardiac muscle
What are the major structural and functional differences among the 3 types of muscle tissue?
- Skeletal
- primarily attached to bones
- striated
- voluntary - Cardiac Muscle
- forms wall of heart
- striated
- involuntary - Smooth (visceral) Muscle
- located in viscera
- nonstriated (smooth)
- involuntary
What are the 5 key function of muscle?
- produces body movements
- stabilizes body positions
- regulates organ volume
- moves substances within the body
- generates heat
What separated muscle from skin?
Superficial fascia
or subcutaneous layer
What are the function of superficial fascia?
- separates muscle from skin
- provide a pathway for nerves and blood vessels
- stores fat
- insulates
- protects muscles from trauma
What is the function of deep fascia?
- holds muscles with similar functions together
- allows for free movement of muscles
- carries nerves, blood vessels, and lymph vessels
- fills spaces between muscles
What attached muscle to bone or muscle to other muscles?
Tendons and aponeuroses
What conveys impulses for muscular contractions?
Nerves (containing motor neurons)
What provides nutrients and oxygen for contraction?
Blood
Epimysium
covers the entire muscle
Perimysium
Covers the fasciculi
Endomysium
Covers individual muscle fibres.
What is a muscle fiber?
thousands of elongated, cylindrical cells arranged parallel to one another.
Each muscle fiber is covered by a plasma membrane called ________.
Sarcolemma
What is muscle fibers cytoplasm called?
Sarcoplasm
What does sarcoplasm contain?
Many mitochondria that produce large amounts of ATP during muscle contractions.
What is sacroplasmic reticulum and what dose it store?
- encircles each myofibril
- a network of fluid-filled membrane-enclosed tubules
stores calcium ions.
What are myofibrils composed of?
thick and thin filaments arranged in units called sarcomeres.
What are sarcomeres?
the basic functional units of a myofibril and show distinct dark (A band) and light (I band) areas.
Where does the Z discs pass through?
center of an I band
Where will you find an H zone?
center of a A band
What is a myofibril?
Cylindrical structures that extend along the entire length of muscle fiber.
When do contractile proteins generate force?
During contraction
What is myosin and what does it function as?
- the main component of thick filaments
- functions as a motor protein.
What do motor proteins do?
push and pull their cargo to achieve movement by converting energy from ATP into mechanical energy of motion or force.
What is actin?
the main component of thin filaments,
- has myosin binding sites where myosin ‘heads’ attach to produce the sliding together of the filaments.
The regulatory proteins tropomyosin and troponin are a part of _______.
the thin filament
What does troponin do?
holds tropomyosin in place.
What happens in a relaxed muscle?
tropomyosin blocks the myosin-binding sites on actin to prevent myosin from binding to actin.
What happens during a contraction?
myosin heads pull on the actin and shorten the muscle cell (during contraction)
What is the process called when myosin heads pull on the actin and shorten the muscle cell?
the sliding-filament mechanism
Before a skeletal muscle fiber can contract, it must be stimulated by an electric signal called?
a muscle action potential
Where do muscle action potentials arise from?
neuromuscular function (NMJ)
What is the neuromuscular junction (NMJ)?
the synapse between a somatic motor neuron and a skeletal muscle fiber
What is a motor unit?
a nerve and the muscle fibers in stimulates.
What is a synapse?
a region of communication between 2 neurons or a neuron and target cell.
What do neurotransmitters do?
bridge the gap between 2 neurons or
a neuron and a target cell, or
a synaptic cleft.
What is the neurotransmitter at a NMJ?
acetylcholine (ACh)
What happens during muscle contraction?
- myosin-cross-bridges pull on thin filaments, causing them to slide inward toward the H zone
- Z discs come toward each other and sacromeres shorten
What is the sliding-filament mechanism?
the sliding of filaments and shortening of sacromeres causes the shortening of whole muscle fiber and entire muscle.
How are calcium ions returned to the sacroplasmic reticulum?
Active transport pumps
What starts a muscle contraction?
an increase of calcium ion concentration in the cytosol.
What stops a muscle contraction?
the decrease of calcium ion concentration in the cytosol.
What are the 4 steps of the contraction cycle?
- Splitting ATP
- Forming cross-bridges
- Power stroke
- Binding ATP and detaching
What is the contraction cycle?
a repeating sequence of events that cause the filaments to slide.
At any given moment, a few muscle fibers within a muscle are contracted, while most are relaxed. Why is this important?
this small amount of contraction is essential for maintaining posture.
What is muscle tone?
a sustained partial contraction of portions of a relaxed skeletal muscle.
When goes muscle fatigue occur?
When a muscle cannot produce enough ATP to meet its needs.
What is muscle fatigue?
the inability of a muscle to maintain its strength of contraction or tension.
What are the 2 sources of oxygen for muscle tissue?
- Diffusion from blood
2. Release by myoglobin inside muscle fibers.
What can aerobic cellular respiration (reactions requiring oxygen) provide?
- completes the oxidation of glucore via cellular respiration
- and provides energy from prolonged activity.
What can anaerobic cellular respiration (glycolysis) provide?
enough energy for about 30-40 seconds.
What can creative phosphate provide?
can power maximal muscle contraction for about 15 seconds
—-used for maximal short bursts of energy.
What are the 3 sources for ATP production in muscle cells?
- Creatine Phosphate
- Anarobic cellular respiration (glycolysis)
- Aerobic cellular respiration (reactions requiring oxygen)
What are the 3 periods of a twitch contraction?
- Latent
- Contraction
- Relaxation
What is a twitch?
a brief contraction of all the muscle fibers in a motor unit in response to a single action potential.
What is a complete (fused) tetanus?
sustained contraction that lacks even partial relaxation between stimuli.
What is a incomplete (unfused) tetanus?
A sustained muscle contraction that permits partial relaxation between stimuli.
What is wave summation?
The increased strength of a contraction.
—- result of the application of a second stimulus before muscle has completely relaxed after a previous stimulus.
What are the 3 main types of skeletal muscles based on structure and function?
- slow oxidative
- fast oxidative-glycolytic
- fast glycolytic fibers.
What is isometric contraction?
give example
a contraction that occurs when tension is applied to muscle but it doesn’t shorten.
ex. carrying a box of book.
What is isotonic contraction?
give example
a contraction that occurs when tension in muscle remains the same but muscle shortens.
ex. when you lift a textbook from a table.
When do cardiac muscles contract?
When stimulated by their own autohythmic fibers.
Where can you find cardiac muscle?
Only in the heart walls.
How do cardiac muscle fibers connect to adjacent fibers?
by intercalacted discs that contain desmosomes and gap junctions.
What is the stress-relaxation response?
Smooth muscle fibers can stretch considerably without developing tension.
What happens when calmodulin activates the enzyme myosin light chain kinase?
it facilitates myosin-actin binding and allows contraction to occur at a relatively slow rate.
In smooth muscle, what is the regulator protein that binds calcium ions in the cytosol?
Calmodulin (in striated muscle, the regulator protein is troponin)
What takes longer in smooth muscle that is skeletal muscle?
Duration of contraction and relaxation.
Where is multi-unit smooth muscle found?
In large blood vessels, large airways, arrector pili muscle and the iris of the eye.
Where is visceral smooth muscle found?
In the walls of hollow viscera and small blood vessels.
What are the 2 types of smooth muscle?
- Visceral (single unit) smooth muscle
2. Multi-unit smooth muscle
