Skeletal Muscle and Nerve Flashcards
What is muscle tissue made up of?
Muscle tissue is made up of elongated cells called muscle fibres, which are long and narrow when relaxed.
What does the prefix “sarco-“ mean
“Sarco-“ is Greek for flesh
Sarcomere definition
Sarcomere: Basic functional (contractile) unit of muscle fibre.
sarcoplasm definition
Sarcoplasm: Cytoplasm of a muscle fibre.
sacrolemma definition
Sarcolemma: Cell membrane of a muscle fibre.
What is the function of muscle tissue?
Muscle tissue moves body parts or changes the shape of internal organs by contraction.
What are the 3 classifications of muscle tissue based on control and structure?
Voluntary vs. Involuntary
Striated vs. Non-striated (viewed under a microscope)
Somatic (body wall and limbs) vs. Visceral (organs)
what does skeletal muscle diagram look like
what does cardiac muscle diagram look like
what does smooth muscle diagram look like
What type of muscle is skeletal muscle?
Skeletal muscle is voluntary somatic muscle.
What is the shape and structure of skeletal muscle fibers?
Long and slender.
Contain peripherally located nuclei.
What unique feature is visible in skeletal muscle under a microscope?
Cross-striations formed by actin and myosin filaments.
Where is cardiac muscle tissue located?
In the walls and septa of the heart and the walls of large vessels.
How is cardiac muscle tissue similar to skeletal muscle?
Both show cross-striations due to myofilaments
What are three differences between cardiac and skeletal muscle?
where is nuclei located on skeletal muscle
peripherally located nuclei
where is nuclei located in cardiac muscles
centrally
Where is smooth muscle tissue found?
In the hollow viscera (e.g., digestive organs) and the walls of blood vessels.
What are the 3 key features of smooth muscle tissue?
Non-striated appearance.
Spindle-shaped, small fibers.
Single, elongated central nucleus.
How do smooth muscle cells appear in longitudinal and cross-section views?
Longitudinal view: Linear bundles of cells.
Cross-section view: Polygonal profiles.
How does smooth muscle differ from skeletal and cardiac muscle?
Smooth muscle is non-striated, with spindle-shaped fibers and a single central nucleus, while skeletal and cardiac muscle have striations.
What is the primary function of tendons?
Tendons provide attachment sites for muscles, both proximal and distal.
What do tendons typically attach to?
Tendons usually attach muscles to bones, but they can also attach to skin, fascia, or even other muscles (e.g., raphae or intermediate tendons).
What is an aponeurosis?
An aponeurosis is a broad, flat, compressed tendon, commonly found on the scalp or abdominal wall.
What is the characteristic of bipennate muscles? Name an example.
Bipennate muscles have fibers attaching to both sides of a central tendon. Example: Rectus femoris.
What defines unipennate muscles? Provide an example
Unipennate muscles have fibers attaching obliquely to one side of a tendon. Example: Extensor digitorum longus.
Describe multipennate muscles. Name an example.
Multipennate muscles have multiple tendons with fibers attaching obliquely. This is the most powerful arrangement. Example: Deltoid.
whats similar about bipennate, unipennate, and multipennate muscle structure?
Typically have long tendons which the muscle fibres attaching obliquely.
A multipennate muscle is the most power arrangement
What shape is a fusiform muscle? Provide an example.
Fusiform muscles are spindle-shaped with a central belly tapering towards the tendons. Example: Biceps brachii.
What are parallel muscles? Give an example.
Parallel muscles have fibers arranged along the long axis of the muscle, often with tendinous intersections. Example: Rectus abdominis.
What is a convergent muscle? Provide an example.
Convergent muscles have a broad origin converging into a single tendon. Example: Pectoralis major.
What is unique about circular muscles? Name an example.
Circular muscles surround openings and control their diameter. Example: Orbicularis oculi.
How is muscle function used in naming? Provide an example.
Function indicates the action of the muscle. Example: Abductor digiti minimi abducts the little finger
How does muscle attachment help in naming? Give an example.
What role does position play in naming muscles? Provide an example.
How is shape used to name muscles? Provide an example.
How is length incorporated in muscle names? Provide examples.
How does size affect muscle naming? Provide examples.
What covers individual muscle fibers (skeletal muscle cells)?
Endomysium covers individual muscle fibers.
What surrounds clusters of muscle fibers (fascicles)?
Perimysium surrounds clusters of muscle fibers (fascicles).
What encloses multiple fascicles to form skeletal muscles?
Epimysium encloses multiple fascicles to form skeletal muscles.
What is actin, and where is it anchored?
Actin is a thin filament anchored to the Z line.
What is myosin, and where is it anchored?
Myosin is a thick filament anchored to the M line
How are actin and myosin filaments arranged in a sarcomere?
Each thick filament (myosin) is surrounded by 6 thin filaments (actin) in a regular arrangement.
What happens during muscle contraction?
Actin filaments slide along myosin filaments as myosin molecules bind and release actin, “walking” along the filament.
What defines the boundaries of a sarcomere?
The boundaries of a sarcomere are defined by two adjacent Z lines.
What are the light-staining and dark-staining bands in a sarcomere?
Light-staining I bands: Associated with thin filaments (actin).
Dark-staining A bands: Associated with thick filaments (myosin).
What is the H zone?
The H zone is the pale central area of the A band where no thin filaments overlap with thick filaments.
What is the I band?
The I band is the light band that contains thin filaments only and does not overlap with thick filaments.
What causes the appearance of the dark and light bands in a sarcomere?
Dark bands (A bands): Alter polarized light in two planes; they are anisotropic.
Light bands (I bands): Do not alter the plane of polarized light; they are isotropic.
What happens to the sarcomere during muscle contraction?
The sarcomere shortens, but the myofilaments (actin and myosin) remain the same length.
What happens to the H band during contraction?
The H band narrows as thin filaments slide into the H band, increasing the overlap with thick filaments.
What happens to the I band and A band during muscle contraction?
I band: Shortens.
A band: Remains the same length.
How do skeletal muscles move bones?
By crossing joints and stabilizing joints.
What is the fulcrum in skeletal muscle movement?
The joint where movement occurs. - Example: Flexion at the elbow joint.
What are the two main components of skeletal muscle movement?
Joint (fulcrum): Where the movement occurs.
Region moved distal to the joint: The part of the body that changes position.
What is reflexive contraction?
A type of muscle contraction regulated by the autonomic nervous system and is not voluntary.
Example: Diaphragm contraction during breathing.
What is tonic contraction?
A slight muscle contraction that occurs even when relaxed, maintaining joint stability and posture.
What is phasic contraction?
Active muscle contraction that produces movement or active resistance.
What are the two types of phasic contraction?
Isotonic
Isometric
What is Isotonic contraction
Muscle changes length during movement (concentric or eccentric).
what is Isometric contraction
Muscle length stays the same, but tension increases to resist gravity or other forces.
Example: Deltoid maintains steady contraction while holding an arm in abduction.
what are the 2 types of isotonic contraction
concentric
eccentric
What is concentric contraction?
Muscle shortens as it generates force, producing movement.
Example: Deltoid shortens to raise the arm in abduction.
What is eccentric contraction?
Muscle lengthens while resisting a force (controlled relaxation).
Example: Deltoid lengthens to lower the arm as gravity pulls it down.
What are prime movers (agonists)?
Muscles that contract actively to produce a desired movement.
What is the role of antagonists?
Antagonists oppose the action of prime movers and relax while the prime mover contracts to produce smooth movement.
How do agonists and antagonists act together during movement?
simultaneously - one concentric, other eccentric
What is the role of synergist muscles?
Synergist muscles assist the prime mover by:
Increasing efficiency of the movement.
Cancelling unwanted movements.
How do synergists help during finger flexion?
Synergists prevent unwanted wrist flexion by extending the wrist, making finger flexion stronger.
What are the two principal types of cells in nerve tissue?
Neurones (nerve cells)
Supporting cells (neuroglial cells/glia)
What is the function of a neurone (nerve cell)?
Neurones are:
The structural and functional units of the nervous system.
Specialised to receive and integrate information from sensory receptors and transmit it to other neurones or effector organs.
What are supporting cells (neuroglial cells/glia) and their types?
Supporting cells are non-conducting cells located close to neurones.
Central neuroglia:
Oligodendrocytes, astrocytes, microglia, ependymal cells.
Peripheral neuroglia:
Schwann cells, satellite cells.
What is the cell body of a neurone?
The cell body contains the nucleus and other organelles.
What are dendrites?
Dendrites are processes branching from the cell body that transmit impulses toward the cell body.
What is the axon (nerve fibre)?
The axon is a long process extending from the cell body that carries information away toward synapses.
What are multipolar neurones?
Multipolar neurones have one axon and multiple dendrites extending from the cell body. They are the most common type of neurone.
What is a bipolar neurone?
A bipolar neurone has a centrally placed cell body with one dendrite and one axon extending from it. This type is rare.
Describe pseudounipolar (unipolar) neurones.
Pseudounipolar neurones have a single process emerging from the cell body that divides into dendritic and axonal branches.
What are multipolar neurones, and what is their function?
Multipolar neurones are motor neurones and interneurons, primarily involved in efferent signals (motor output).
Where are bipolar neurones found, and what is their role?
Bipolar neurones are sensory neurones associated with special senses, like the retina of the eye, and transmit afferent signals.
What are pseudounipolar (unipolar) neurones, and where are they located?
seudounipolar neurones are sensory neurones. They are the primary afferents of spinal and cranial nerves, with cell bodies located in the dorsal root ganglia and cranial nerve ganglia.
What are upper motor neurones (UMNs), and where do they originate?
UMNs originate in the motor cortex or brainstem. They influence the excitability and output of lower motor neurones (LMNs).
What are lower motor neurones (LMNs), and where are they located?
LMNs are located in the ventral horn of the spinal cord or the cranial nerve nuclei of the brainstem and cranial nerves.
What is the role of lower motor neurones (LMNs)?
LMNs leave the central nervous system and bring motor signals to the muscles for movement.
What happens at the synapse between UMNs and LMNs?
Upper motor neurones synapse with lower motor neurones to transmit motor signals, enabling motor control.
Give an example of a condition involving motor neurone syndrome.
stroke and facial palsy.
What are the two sensory organs for proprioception?
Muscle spindles (located in muscles) and Golgi tendon organs (located in tendons).
How does tapping the patellar tendon activate motor neurones?
Tapping activates the Golgi tendon organ and muscle spindles in the quadriceps, stimulating motor neurones to extend the knee.
