Biology Chapter 41

Muscle

A tissue composed of cells capable of contracting and moving the body

Joint

the physcial connection between two or more bones in the body, primarly functioning to allow movement and provide mechanical support.

Contracting

shortening of an entire muscle caused by interactions of actin and myosine filaments, none of those are actually shortening. Often referred to as “grip and slide” mechanism.

Skeletal Muscle

Also known as striated muscle; moves the skeleton and is nearly all under voluntary control.

Tendons

attach muscles to bone, made up of connective tissue

The skeleton composition

made of cartilage, ligaments, and bone

Muscle fibers

individual muscle cells grouped into bundles encased in connective tissue

Multiple nuclei

found in skeletal muscle cells, direct transcription

Myofibrilis

Cylindrical subunits found inside muscle fibers

Sarcoplasmic Reticulum

A specialized endoplasmic reticulum filled with fluid containg a high concentration of calcium ions necessary for muscle contraction

T Tubules

tiny tubes formed by the plasma membrane that tunnel deep into the muscle fiber

Mitochondria

organelles found in a lot of eukaryotic cells, however skeletal and cardiac muscles certain elevated quantity, allow to generate ATP for muscle contraction

ATP hydrolysis

a reaction of breaking up ATP into Adenosine diphosphate and a free phosphate, required for energizing the head of myosin

Sarcomeres

Repeating subunits alighned to end to end along a myofibril, connected by Z discs

Thin Filament

formed from stings of actin proteins; anchored to a Z disc. Made up of 2 strings of spherical protein twisted around each other.

Thick filament

formed from bundels of myosin proteins suspended between thin filaments. Made up of bundles of hockey sticks

Cardiac Muscle

Muscle found only in the heart; it is straited and fibers are branched. Contain just one nucleus per cell, made up of sarcomers like skeletal muscles, have a mitochondria, use cullular respiration and oxygen for majority of contraction use glycolysis very little or none.

Emergency Response in cardiac muscle

When oxygen is low, the cardiac muscle in the heart rapidly increases its rate of glycolysis to compensate for the loss of aerobic energy production. This helps maintain cell viability, even if it cannot sustain full contractile power for long. When the heart cannot provide enough oxygen to tissues, the body shifts from aerobic metabolism to anaerobic glycolysis, which produces lactate as a byproduct.

Smooth muscle

produces slow, involuntary contractions; surrounds blood vessels and hollow organs. They do have actin and myosin, but scattered. Cells have single nucleus, still able to contract in sychrony producing slow and wavelike or slow and sustained contraction of hollow organ

Skeleton

the structure that supports the body and provides a framework for muscels to exert force

Antagonistic Muscles

Pairs of muscles with opposing actions

Protagonistic

group of muscles having similar action

Hydrostatic Skeleton

a sac or tube filled with liquid found in worms and cnidarians

Exoskeletons

rigid outer coverings that encase the bodies of arthropods like insects

Endoskeletons

internal skeletons found in echinoderms and chordates

Axial skeleton

bones of the head, vertebral column, and rib cage

Appendicular skeleton

the pectoral/pelvic girdles and the appendages

Pectoral girdle

connects the arms to the torso

pelvic girdle

connects the legs to the spine

movement

any physical motion of a body part. the organism stays in the same spot

locomotion

movement that results in the entire organism moving from one place to another

lactate

a byproduct of anaerobic ATP generation process, can accumulate in cardiac muscles, also it can accumulate in skeletal muscles due to strenouous workout

striated appearance

the “striped” look of muscle caused by the precise arrangement of thin and thick filaments. found in cardiac and skeletal muscles

accessory proteins

troponin and tropomysin, which regulate the interaction between filaments

myosin head

a hinged part of the the myosin protein that can swivel back and forth to grip actin. The head is attached to shaft, forming a “hockey stick” structure

sliding filament mechanism

the process where thin filaments slide past thick and skeletal muscles contract as a part of single motor units, the whole muscle shortens and moves two bones closer, or contracts the cardiac muscle chambers. in smooth muscles actin and myosin also slide past each other, but no sarcomers are found.

endergonic reaction

muscle contraction is a reaction that uses ATP energy

slow-twitch fibers

contract with less power but can keep contracting for a longer time; specialized for endurance. energy ATP for contraction is provided by cellular respiration with O2, aerobic

fast-twitch fibers

have a larger diameter and contract with greater force, but fatigue rapidly. energy ATP is provided by glycolysis in cell cytoplasm

myoglobin

a red-colored protein that stores oxygen in slow-twitch and cardiac fibers

neurromusclar junctions

specialized synapses where motor neurons release acetylcholine to excite muscle fibers

motor unit

a motor neuron and all the muscle fibers it synapses with; they vary tremendously in size: small units with precise movement and large with powerful movement

intercalated discs

junctions that connect cardiac fibers, allowing action potentials to spread rapidly

pacemaker

specialized cardiac fibers that initiate their own contractions wihtout nervous system input

flexor & extensor

a flexor bends a joint; and extensor straightens it

ligaments

attach bone to bone. act like “straps” to hold bones together at a joint, providing stability and preventing dislocations.

chondrocytes

living cells of cartilage that secrete glycoproteins and collagen

osteons

subunits of compact bone formed of concentric layers surrounding a central canal

bone remodeling

process of replacement of bone tissue, happens continously through life, managed by osteocytes

power stroke

the step where the myosin head expends energy to pull the actin filament toward the middle of the sarcomere

energy sources

muscles use glycolysis for brief high-intensity exercise and cellular respiration for prolonged exercise

glycolysis

generation of ATP using NO oxygen by splitting glucose into two molecules of pyruvaate, and subsequently making latic acid allowint muscles to contract with no oxygen during extreme circumstances. generally unsustaniable, only generates 2 ATP molecules per glucose

cellular respiration

generation of ATP using glucose, requires constant supply of O2

Excitation-Contraction Coupling

an action potential moves down T tubules to the SR, causingCa2+ to be released into the cytosol

C2+ Binding

calcium binds to troponin, pulling tropomyosin off the actin binding sites so myosin can attach

Calcium ions role

acts as the switch released from the SR, it binds to troponin to move tropomyosin, finally uncovering the actin binding sites so contraction can begin.

ATP role

it provides the energy for the power stroke, binds to the myosin head to make it release the actin, and powers the pumps that return calcium to the SR so the muscle can relax

excitatory postsynaptic potential

a local, variable change in voltage at the muscle fiber’s membrane; when the neurotransmitter acetylocholine triggers a large enough EPSP to reach the threshold, it leads to the generatio of a full action potential

inhibitory postsynaptic potential

a local, variable change in voltage that makes the membrane more negative; this moves the neuron farther from the threshold, making it less likely to generate an action potential and effectively “silencing” the signal

visible twitch

created by the release and re-pumping of C2+ following a single action potential

force control

the nervous system controls force by varying the number of motor units and the rate of action potentials

hydrostatic movement

animals use circular muscles to become thinner/longer and longitudinal muscles to become shorter/fatter

cartilage matrix

contains glycoproteins and elastic fibers; lacks blood vessels, so it repairs itself slowly

bone matrix

a scaffold of collagen strands for crystals of mineral

spongy and compact bone

spongy bone is porous and lightweight; compact bone is dense and provides attachement sites for muscles

Bone marrow types

red bone marrow forms blood cells; fatty yellow marrow fills cavities in adults

bone cells

osteoblasts, osteocytes, and osteoclasts

molting

shedding of the exoskeleton by animals like insects etc, allows growth

osteoporosis

failure of the bone remodeling with age, increased fragility of the bone, lack of exercise plus genetic factors play a big role

hinge joint

a type of synovial joint that allows motion in only one plane, similar to the opening and closing of a door

origin

the end of a muscle attached to a bone that stays still during movement.

insertion

the end of a muscle attached to the bone that actually moves

ball-and-socket joint

a joint where the rounded end of one bone fits into the hollow space of another, allowing for rotation and movement in many directions.