muscular and skeleton - יערה לסיים Flashcards
define glycogen
Glycogen is the stored form of glucose in the body, particularly in the liver and muscles. Glucose, a simple sugar, is the main source of energy for the cells. When the body doesn’t immediately need the glucose from your food, it gets converted and stored as glycogen for later use.
define cardiac muscle
Cardiac muscle is also known as heart muscle or myocardium.
It forms the thick middle layer of the heart wall and is responsible for the powerful, rhythmic contractions that pump blood throughout the body. it is not possible to consciously control cardiac muscle. It contracts automatically in a coordinated rhythm dictated by the heart’s natural pacemaker.
cardiac muscle cells have a striped appearance under a microscope due to the organized arrangement of contractile proteins within them. typically have one nucleus, although some may have two. This is different from skeletal muscle which is multinucleated (many nuclei).
define skeletal muscle
Skeletal muscles are the muscles that you can control voluntarily. They are responsible for all the movements of the body parts, from blinking your eyes to running a marathon. They are also known as striated muscles because of their microscopic striped appearance.
Skeletal muscle cells have a striated appearance under a microscope. This is due to the orderly arrangement of proteins within the cells. single skeletal muscle cell contains many nuclei rather than just one, located by the edge of the cell.
define smooth muscle
Found in the walls of hollow organs throughout the body, including the stomach, intestines, bladder, uterus, and blood vessels.
Plays a crucial role in involuntary actions like digestion, waste elimination, blood flow regulation, and maintaining organ shape.
Unlike skeletal muscle (controlled consciously) and cardiac muscle (automatic heart function), smooth muscle contracts and relaxes involuntarily. The nervous system or hormones trigger these actions.
Smooth muscle cells are elongated and spindle-shaped, with a single centrally located nucleus. smooth muscle lacks the striped pattern of skeletal and cardiac muscle. This is because the contractile proteins (actin and myosin) are not arranged in a highly organized way within the cells.
define excitability
excitability refers to the property of a cell or tissue to respond to a stimulus. This is particularly important in the context of neurons and muscle cells.
define contractility
Contractility is the ability of a cell or tissue to contract and shorten in response to a stimulus.
Contractility is an essential property of muscles, allowing them to generate force and movement (actively).
define tendon
where in the muscle does it connect?
A tendon is a tough, fibrous cord made of dense connective tissue. It acts as a bridge between muscles and bones, transmitting the force generated by muscle contractions to the bones, which allows for movement.
Tendons are primarily composed of collagen fibers, which are strong and flexible, allowing them to withstand significant tension.
origin - proximal side
insertion - distal side
define extensibility
t’s a measure of how easily a muscles can be extended
define elasticity
Elasticity refers to the ability of a muscle object to resist a distorting influence and return to its original size and shape
define epimysium
Epimysium is the outermost connective tissue sheath that surrounds a skeletal muscle. It’s a tough layer protecting the muscle and separating it from neighboring muscles and bones.
define perimysium
Perimysium is a layer of connective tissue that groups muscle fibers together within a skeletal muscle.
It surrounds individual bundles of muscle fibers, called fascicles (each containing 10-100+ fibers). Perimysium separates these fascicles from each other provides structural support.
define endomysium
Endomysium is the innermost layer of connective tissue that surrounds and supports individual muscle fibers within a skeletal muscle. It’s a delicate sheath that provides a microenvironment for each fiber
define fascicle
A fascicle refers to a bundle of muscle fibers within a skeletal muscle. These muscle fibers are grouped together by connective tissue called the perimysium. Fascicles work together to generate a stronger overall force compared to individual muscle fibers contracting alone.
define sarcolemma
The sarcolemma is the cell membrane surrounding a skeletal muscle fiber or a cardiomyocyte (heart muscle cell).
define myofibril
A myofibril is the basic unit of contraction within a skeletal muscle fiber. These myofibrils are responsible for the striated (striped) appearance of skeletal muscles seen under a microscope.
define sarcomere
what is its size? (relaxed and contracted)
what is its structure?
A sarcomere is the fundamental unit of contraction within a skeletal muscle fiber (rows of sarcomeres make up myofibrils). It’s the smallest functional unit that can shorten to generate force.
The length of a relaxed sarcomere is typically around 2.0 to 2.2 micrometers (µm). When a muscle contracts, the sarcomere shortens. The extent of shortening depends on the intensity of the contraction, but generally a sarcomere can shorten by about 20-30%, bringing its length to around 1.6 to 1.8 micrometers (µm).
The sarcomere is a highly organized structure composed of two main types of protein filaments:
Thick filaments (myosin): These are located in the center of the sarcomere and appear dark under a microscope. Myosin has projections called myosin heads that can bind to actin and generate force.
Thin filaments (actin): Thinner filaments flanking the myosin filaments. Actin plays a crucial role in the muscle contraction process by interacting with myosin heads.
define sarcoplasm and sarcoplasmic reticulum
Sarcoplasm is the cytoplasm, or the fluid-filled interior, of a muscle cell.
The sarcoplasmic reticulum (SR) is a specialized membrane network within the sarcoplasm of a muscle cell. The primary function of the SR is to store and release calcium ions (Ca²⁺). Calcium plays a critical role in initiating muscle contraction. When a signal arrives from the nervous system, the SR releases calcium into the sarcoplasm. This increase in calcium concentration triggers a chain reaction that leads to the interaction between actin and myosin filaments within the myofibrils, ultimately causing muscle contraction.
define filaments
filaments are generally long, thin, thread-like structures found within cells. They play various crucial roles in cell structure, movement, and function. Filaments are primarily composed of proteins, but the specific protein type can vary depending on the filament’s function.
can be seen in electrons microscope.
define I band
lighter bands on either side of the sarcomere where only thin actin filaments are present (no overlap with myosin). These bands also narrow during contraction.
define H band/zone
The lighter region in the center of the sarcomere where only thick filaments are present (no actin). This zone gets narrower during contraction as the filaments slide past each other.
define A band
The A band is the darker, more prominent region in the center of the sarcomere. It appears dark because it contains both thick and thin filaments overlapping to a significant degree.
define thick filaments
thick filaments are protein structures composed primarily of the protein myosin.
Thick filaments are elongated, rod-shaped structures with a tail and two globular heads at opposite ends.
define thin filaments
thin filaments are thread-like structures composed primarily of the protein actin.
Thin filaments are long, double-stranded polymers made up of actin subunits that twist together to form a helical structure. Along the length of the thin filament, regulatory proteins called troponin and tropomyosin are bound.
define tropomyosin
a protein twisted around actin chains.
in relaxed muscle, it hides myosin binding sites on the actin chains.
define troponin
a protein linked to the actin chain at constant distances and has binding sites for Ca+2.
gives “order” to the tropomyosin to move
define cross striations
Cross-striations refer to the alternating dark and light bands visible under a microscope when looking at skeletal muscle tissue. This striated appearance is a defining characteristic of skeletal muscle and reflects the highly organized arrangement of proteins within the muscle cells.
what is the difference between light and dark areas?
Dark areas (A bands): These appear darker because they contain a dense overlap of both thick filaments (myosin) and thin filaments (actin). This dense overlap allows for a greater number of potential interactions between myosin heads and actin binding sites, which is crucial for force generation during muscle contraction.
Light areas:
I bands (light): These flank the A band on either side and appear lighter because they contain only thin actin filaments. There’s no overlap with the thick filaments in this region.
H zone (lighter within A band): This is a faint, lighter zone in the middle of the A band. It appears lighter because it contains only thick filaments, with no overlap of thin filaments in this specific region within the A band.
define M line
A lighter line in the middle of the sarcomere that holds the thick myosin filaments together.
what is Z line?
another name for the Z line
Dark lines that mark the boundaries of the sarcomere. They anchor the thin actin filaments.
aka disc.
define cross bridge cycle
(Steps)
The cross-bridge cycle, also known as the actomyosin cycle, is the fundamental process that drives muscle contraction in skeletal muscle [National Institutes of Health, Muscle Contraction]. It involves the intricate interaction between thick filaments (myosin) and thin filaments (actin) within the sarcomere.
Steps in the Cycle:
1. Attachment: When a signal triggers muscle contraction, calcium ions (Ca²⁺) flood the sarcoplasm (cell interior). Calcium binding to troponin on the thin filament causes a conformational change that removes tropomyosin from the actin binding sites. With the binding sites exposed, a myosin head with high affinity for actin can attach to a specific site on the thin filament.
2. Power Stroke: Once attached, the myosin head undergoes a conformational change using the energy from ATP hydrolysis (breaking down ATP into ADP and phosphate). This conformational change is like a power stroke, pulling the thin filament towards the center of the sarcomere.
3. Detachment and Reattachment: After the power stroke, the myosin head detaches from the actin binding site.
The myosin head then binds a new ATP molecule, which resets it to a high-affinity state ready to attach to another actin binding site further down the thin filament.
4. Recycling: The cycle of attachment, power stroke, detachment, and reattachment continues as long as calcium levels remain high and sufficient ATP is available.
This repetitive cycle leads to the sliding filament mechanism: the thin filaments appear to slide past the thick filaments within the sarcomere, even though the filaments themselves are stationary.
define motor unit
consists of nerve fiber and the muscle fiber/s it innervates.
one neuron can innervate several muscle fibers in parallel.
define neoromuscular junction
NMJ / motor end plate
a chemical synapse between nerce ending of motor neuron and muscle fiber.
the neurotransmitter is acetylcholine.
……
define end plate action potential
generated and then propaghated in the muscle fiber.
define sarcoplasmic reticulum
The sarcoplasmic reticulum (SR), often abbreviated as SR, is a specialized organelle found within skeletal and cardiac muscle cells. It’s essentially a network of interconnected membranes that acts as a storage tank for calcium ions (Ca2+).
The primary function of the SR is to store and release calcium ions.
Calcium plays a crucial role in muscle contraction. When a muscle needs to contract, the SR rapidly releases calcium ions into the surrounding sarcoplasm (the fluid inside the muscle cell).
This surge in calcium triggers a series of events within the myofibrils, ultimately leading to muscle fiber shortening and contraction.
define triad
a triad is a tiny but critical structure found in skeletal muscle. It’s like a microscopic communication hub that coordinates the process of muscle contraction.
The triad acts as a bridge between the nervous system’s signal and the muscle’s response. When a nerve impulse arrives, it travels through the T-tubule. This triggers the release of calcium from the terminal cisternae of the SR.
T-tubule: A tiny invagination (inward fold) of the muscle cell membrane.
Terminal cisternae: Two sac-like structures from the sarcoplasmic reticulum (SR), a network that stores calcium within the muscle cell.
define terminal cisternae
Terminal cisternae are specialized regions within muscle cells that play a vital role in muscle contraction. They are like tiny calcium storage tanks located next to specialized channels called T-tubules.
Terminal cisternae, along with T-tubules, form a crucial part of the excitation-contraction coupling (ECC) mechanism in muscles. This mechanism translates the electrical signal from the nervous system into the mechanical response of muscle contraction. By storing and releasing calcium in a controlled manner, terminal cisternae ensure precise and efficient muscle function.
define agonist muscle
An agonist muscle, also sometimes called the prime mover, is the main muscle responsible for producing a specific movement at a joint.
define antagonist muscle
An antagonist muscle, also sometimes called the opposing muscle, is the counterpart to the agonist muscle. It works in opposition to the agonist, relaxing and lengthening to allow for the agonist’s contraction and movement at a joint.
define synergists
In the world of muscles, synergists are teammates! They work together with another muscle, the agonist, to produce a specific movement at a joint.
define endurance
fast type 1a
low ATP, long periods
slow type 1
define explosive
fast type 2b
high ATP, short periods
define intermediate
type 2a
define creatine phosphate
stores of phosphocreatine in sarcoplasm
define myoglobin in muscels
איפה ממוקם?
למה מתפקד?
located in the sarcoplasm of striated muscle
function as mobile carrier of O2 and oxygen storage in muscles
define hydroxyapatite
Hydroxyapatite (HA) is a naturally occurring mineral found in the human body. It’s the main inorganic component that gives bones and teeth their hardness and structure.
Ca5(PO4)3(OH)
define osteon
An osteon, also known as a Haversian system, is the fundamental functional unit of mature compact bone. They are cylindrical structures, typically between 0.25 and 0.35 millimeters in diameter and several millimeters to a centimeter long .
Each osteon consists of several key components:
Haversian canal: A central canal that runs along the long axis of the osteon. This canal contains blood vessels and nerves that supply nutrients and remove waste products from the bone tissue.
Lamellae: Concentric rings of hard, calcified bone matrix that surround the Haversian canal. These lamellae are made up of collagen fibers and hydroxyapatite, a calcium phosphate mineral that gives bones their strength and rigidity. The lamellae are arranged in layers, with the newest bone tissue located closest to the Haversian canal and the older bone tissue located further away.
Lacunae: Tiny cavities within the lamellae that house osteocytes, mature bone cells. Osteocytes are responsible for maintaining bone tissue.
Canaliculi: Microscopic channels that radiate outward from the lacunae. These channels connect the osteocytes to each other and to the Haversian canal, allowing nutrients and waste products to pass through.
Cement line: A thin layer of mineralized material that separates each osteon from its neighbors.
Osteons are formed through a process called bone remodeling. In this process, old bone tissue is continuously removed by osteoclasts (bone-resorbing cells) and replaced with new bone tissue formed by osteoblasts (bone-forming cells). The new bone tissue is deposited in concentric layers around a blood vessel, eventually forming an osteon.
define central canal
The central canal, also known as the spinal foramen or ependymal canal, is a fluid-filled channel that runs longitudinally through the entire length of the spinal cord .
The central canal has two main functions:
Transport of cerebrospinal fluid (CSF): The CSF acts as a protective cushion for the brain and spinal cord, removes waste products, and delivers nutrients. The central canal plays a vital role in transporting CSF throughout the spinal cord.
Potential nutrient delivery: While the exact role is still being explored, the central canal might also play a part in delivering nutrients to the spinal cord tissues.
define lamellae
lamellae are the concentric rings of hard, calcified bone tissue that surround the Haversian canal (central canal) in compact bone. These layers are made of collagen fibers and hydroxyapatite, a mineral that gives bones their strength. The arrangement of lamellae, with newer layers closer to the canal and older ones further away, contributes to the overall strength and structure of the bone.
define lacunae
lacunae are small spaces within the lamellae (layers) of compact bone. These cavities house osteocytes, mature bone cells responsible for maintaining bone tissue. Osteocytes reside in lacunae and send out tiny channels called canaliculi to connect with each other and the blood vessels in the central canal.
define canaliculi
Canaliculi are microscopic channels in bone that radiate outward from the lacunae (tiny cavities). They play a crucial role in keeping bone tissue healthy.
define medullary cavity
The medullary cavity, also known as the marrow cavity, is the hollow space found in the center of long bones and some flat bones. It’s essentially the inner core where important processes happen.
Function:
Holds bone marrow: The medullary cavity acts as a housing unit for bone marrow, which is a soft, connective tissue responsible for two critical functions:
Blood cell production: Red bone marrow in the cavity manufactures red blood cells, white blood cells, and platelets.
Fat storage: Yellow bone marrow, also found in the cavity, primarily stores fat but can convert back to red bone marrow when the body needs to increase blood cell production.
define spongy bone
