muscular and skeletal systems Flashcards
function of animmal skeletal systms
physical support and locomotion
muscular systm main dunction
generaters force
endoskleton
serves as framwork within all vertebrate organisms
muscles are attached to bones, permitting movement
th endoskeleton also provides protection by surrounding delicate internal organs with bone
the rib cage protects thoracic organs (heat and lungs), skull and vertebral column protect brain and spinal cord
2 major components of skeleton are cartilage and bone
cartilage
a type of connective tissue that is softer and more flexible than bone
retained in adults where firmness and flexibility is needed
ex: ear, nose, walls of larynx and trachea, skletal joints contain cartilage
chrondrocytes
cells responsible for synthesizing cartilage
bone
mineralized connective tissue that has ability to withstand physical stress
adapted for body support, bone tissue is hard, and also elastic and lightweight
2 basic types: compact bone and spongy bone
compact bone
dense bone that does not appear to have an cavities when observed with naked eye
the bony matrix id deposited in structural units called osteons
each osteon has a central microscopic channel called Haversian canal surrounded by a number of concntric circles of bony matrix (calcium phosphate) called lamellae
osteon
the bony matrix is deposited in structural units called osteons (Haversian systems)
each osteon has a central microscopic channel called a Haversian canal, surrounded by cencentric circles of bony matrix (calcium phosphat) called lamellae
spongy bone
much less dense than compact bone, and consists of an interconnecting lattice of bony spicules (hard body)
the cavities between the spicules are filled with yellow or red bone marroe
yellow bone marrow
inactive and infiltrated by adipose tissue
fills the cavities between spicules of spongy bone
red bone marrow
involved in blood cell formation
fills the cavities between spicules of spongy bone
the 2 types of cells found in bone tissue
osteoblasts and osteoclasts
osteoblasts
1 of 2 type of cells found in bone tissue
synthesize and secrete the organic constituents of the bone matrix
once they have become surrounded by their matrix they mature into osteocytes
osteocytes
made of mature osteoblasts
osteoclasts
1 of 2 types of cells in bone tissue
are large, multinucleated cells involved in bone reabsorption when bone is broken down and minerals are released into blood
axial skeleton
is the basic framework of the body
consisting of the skull, vertebral column and rib cage
it is the point of attachment of the appendicular skeleton (includes bones of the appendages (limbs) anf the pectoral girdles (connect to arm) and pelvic girdles
appendicular skeleton
includes the bones of the appendages (limbs) and the pectoral and pelvic girdles
how are these bones held together:
- sbones of the skull
- bones that move relative to one another
sutures or immovable joints hold the bones of the skull together
bones that move relative to one another are held together by movable joints and are supported and strengthened by ligaments
ligaments
serve as bone-to-bone connectors
tendons
attach skeletal muscle to bones and bend the skeleton at the movable joints
origin
point of attachment of a muscle to a stationary bone
(proximal end) in limb muscles
insertion
attachment of a muscle to the bone that moves (distal end in limb muscles) is called the insertion
extension and flexion
indicates a straightening of a joint, whereas flexion refers to a bending of a joint
the 3 types of muscle
skeletal muscle
smooth muscle
cardiac muscle
pyramidal system
nervous control of the muscular system involves axons of the pyramidal cells of the motor cortex
they descnd from the brain to synapse on lower motor neurons in the brain stem and spinal cord
because hthere are no intervening synapses, the pyramidal system is able to provide rapid commands the the skeletal muscles and various other organs
extrapyramidal system
centers that can issue somatic motor commands as a result of processing performed at the unconscious, involuntary level
these centers and their associated tracts comprise the extrapyramidal system
the red nucleus located in the mesencephalon is he component of the extrapyramidal system that is primarily in control of skeletal muscle tone (contraction of muscles)
skeletal muscle function and structure
responsible for voluntary movements
is innervated by somatic nervous system
each fiber is a multinucleated cell created by the fusion of several mononucleated embryonic cells
embeded in the fibers are filaments called myofibrils, which are further divided into contractile units called scaromeres
the myofibrils are enveloped by a modified endoplasmic reticulum that stores calcium ions and is called the sarcoplasmic reticulum
myofibrils sacromeres sacroplasmic reticulum sarcoplsm sarcolemma mitochondria
myofibrils are filaments embeded in muscle fibers
they are further divided into contractile (capable of producing a contraction) units called sacromeres
the myofibrils are enveloped by a modified endoplasmic reticulum that stores calcium ions and is called the sacroplasmic reticulum
the cytoplasm of a muscle fiber is called the carcoplasm
cell membrane of a muscle fiber is called a sarcolemma
because of the high energy requirements of a contraction, mitocondria are very abundant in misicle cells and are distributed along the myofibrils
sarcolema
cell membrane of a muscle fiber
it is capable of propagating an action potential and is connected to a system of transverse tubules (the T system) oriented perpendicularly to the myofibrils (filaments embeded in muscle fiber)
sarcoplasmic reticulum
myofibrils (filaments embeded in muscle fibers) are enveloped by a modified endoplasmic reticulum that stores calcium ions and is called the sarcoplasmic recticulum
T system
a system of transverse tubules, oriented perpendicularly to the myofibrils
T system provides the channels for ion flow throughout the muscle fibers and can also propagate action potentials
striated muscle
skeletal muscle has striations of light and dark bands and is therefore referred to as striated muscle
sacromere structure
Z lines, M line, I band, H zone, A band
muscle contraction
myofibrils are filaments embeded in muscle fibers
they are further divided into contractile (capable of producing a contraction) units called sacromeres
sacromeres are made of thin and thick filaments
the thin filaments are chains of actin molecules
the thick filaments are composed of organized bundles of myosin molcules
organization of a sacromere:
Z lines: define the boundaries of a single sacromere and anchor the thin filaments
M line: runs down the center of the sacromere
I band: is the region containing thin filaments only
H zone: the region containing thick filaments only
A band: spands the entire length of the thick filaments and any overlapping portions of th thin filaments
when muscles contract, the Z lines move toward each other. during contractiong the A band is not reduced in size, but the H and I bands are
how arw muscle contrations stimulated
by a message from the somatic nervous system sent via a motor neuron
neruomuscular junction
the link between the nerve terminal (synaptic bouton) (bringing the stimualtion from the somatic nervous system) and the sacrolema of the muscle fiber
synapse
the space between the nerve terminal and the sarcolema (cell membrane of muscle fiber) is called the synapse or synaptiic cleft
how is an action potential generated in the muscle, and the direction it travels
depolarization of motor neuron results in the release of neruotransmitters from the nerve terminal
the neurotransmitter diffueses across the synaptic cleft and binds to special receptor sites on the sarcolema (cell membrane)
if enough of these recetors are stimulated, the permeability of the sarcolema is altered and an action potential is made
once the action potential is made, it is conducted along the sarcolema and the T system and into the interior of the muscle fiber
muscle (sacromere) contraction mechanism
once an action potential is made, it goes along the sarcolema (cell membrane) and the T system and into the interior of the muscle fiber
this causes the sarcoplamsic reticulum to release Ca2+ ions into the sacroplsm
the Ca2+ ions initiate the contracition of the sarcomere by binding to troponin C on the actin filaments
allosteric changes occur in the proteins that allow myosin heads to bind to these sites on the actin
use of energy allows a power stroke to occur, pulling the Z bands closer together
actin and myosin slide past each other, and the sacromere contracts
rigor mortis
several hours after death all the muscles in the body go into a state of rigor mortis
the muscles contract and become rigid, even without action potentials
the rigidity is caused by an absense of ATP which is required for myoisn heads to be released from the actin filaments
muscles remain rigid for 12 to 24 hours until the muscle proteins degrade
5 major types of muscle contractions
isotonic isometric dynamic concentric eccentric
isotonic muscle contraction
occurs when a miscle shortens against a fixed load while the tension in that muscle remains constant
ex: lifting weights
dynamic muscle contraction
includes both conntric and eccentric types of contraction
results in a change in length if a muscle with a corresponding change in tension on that muscle
concentric contraction
a type of dynamic contraction
muscle fibers shorten and the tension on the muscle increases
eccentric contraction
type of dynamic contraction
muscle fiber lengthens anf the tension on the muscle increases
isometric contraction
occurs when both ends of the muscle are fixed and no change in length occurs during the contraction, but the tension increases
threshold and muscle coontaction
individ muscle fibers exhibit and all-or-none response
only a stimulus above a minimal value called the threshold value can illicit a contraction
strength of muscle fiber contraction versus strength of entire muscle contraction
the strength of the contraction of a single muscle fiber can’t be increased regardless of strength of stimulus
BUT the strengh of contraction of the entire muscle can be increased by recruiting more muscle fibers
simple twitch
the response of a single muscle fiber to a brief stimulus at or above the threshold stimulus and consists of latent period, a contraction period and a relaxation period
latent period: the time between stimulation and the onset of contraction
during this time lag, the action potential spreads along the sarcolemma and Ca2+ ions are released
after the contraction period, there is a brief relaxation period during which the muscle is unresponsive to a stimulus - known as absolute refractory period
tetanus contraction
when fibers of a muscle are exposed to very frequen stimuli, the uscle cannot fully relax
the contractions begin to combine, becoming stronger and more prolonged-known as temporal stimulation
the contractions become continuous when the stimuli are so frequent that the muscle cannot relax
known as a tetanus contraction, and is stronger than a simple twitch of a single fiber
if tetanus is maintained, the muscle will fatigue and the contraction will weaken
tonus
is a state of partial contraction
muscles are never completely relaxed and maintain a partially contracted state at all times
the different types of muscle responses
simple twitch
tetanus
tonus
energy generation in muscles during strenuous activity
during periods of strenous activity:
-skeletal muscles convert glucose to pyruvic acid through glycolysis
this allows skeletal muscles to continue contracting even in absense of oxygen
-lactic acid is generated when pyruvic acid reacts with the enzyme lactate dehydrogenase- this process is allows pyruvate to enter the citric acid cycle
cori cycle
during periods of strenous activity, it conerts lactic acid in the liver to glucose for discharge in the bloodstream
once glucose is in the blood, the muscles are able to use the glucose as an imtrmediate source of energy or to rebuild their glycogen reserves
- conversion of glucose into pyruvate in the muscle cells is necessary for making ATP during periods of activity and doesn’t involve the Cori cycle
- during periods of intense exercise, the production of lactic acid is increased and glycogen is broken down into glucose; however it is not by means of the Cori cycle
smooth muscle
responsible for involuntary actions and is innervated by the autonomic nervous system
found in digestive tract, bladder, uterus, blood vessel walls etc
smooth muscle cells possess one centrally located nucleus and lack the striations of skeletal muscle
caridac muscle
muscle tissue of heart is made of cardiac muscle fibers
these fibers have charactristics of both skeletal and smooth muscle fibers
as in the skeletal muscle, actin and mysin filaments are arranged in sacromeres, giving cardiac muscles a striated apprearence
hoever, cardiac muscle cells generally have only one or 2 centrally located nuclei.
summary of smooth muscle
- nonstriated
- one nucleus per cell
- involuntary/autonomic nervous system
- smooth continuous contractions
cardiac muscle summary
- striated
- one or two nuclei per cell
- involuntary/autonomic nervous system
- strong, forceful contractions
skeletal muscle summary
- striated
- multinucleated cells
- voluntary/somatic nervous system
- strong, forceful contractions
energy used in muscles
ATP is primary source of energy for muscle contraction
very little ATP is actually stored in the muscles so other forms of energy must be stores and rapidly converted to ATP
Creatine phosphate
in vertebrates, energy can be temporarily stored in high-energy compound called creatine phosphate
myoglobin
is a hemoglobin-like protein found in muscle tissue
myoglobin has high oxygen affinity and maintains oxygen supply in muscles by tightly binding to oxygen
