Capter 7: Muscular System (Muscle Notes) Flashcards
Functions of skeletal muscle
Produce movement Maintain posture and body position support soft tissues guard entrance/ exits maintain body temperature
Gross anatomy of a Muscle
3 layers of connective tissue - Epimysium -perimysium - Endomysium All layers come together to form tendon
Epimysium
separates muscle organ from surrounding tissues and organs
Perimysium
divides bundles of muscle fibers into fascicles
- contains blood vessels and nerves that supply fasicles
Endomysium
surrounds muscle fibers and ties them together
tendons are what type of tissue
connective
Microanatomy
cell membrane= sarcolemma
cytoplasm= sarcoplasm
transverse tubules- network of tunnels that coordinate contraction
myofibrils
- 1-2 um diameter/ run length of muscle
- 000’s contained in 1 muscle fiber
- made up of thick (myosin) and thin (actin) filaments
sarcoplasmic reticulum
- surrounds each myofibril
- contains calcium ions, used for contraction
- release of calcium initiates muscle contraction
Sarcomeres
- smallest functional unit of the muscle fiber
- produces striated appearance
- thick and thin filaments line up next to each other
- neither filament spans the entire sarcomere
Thick and thin filaments
-actin molecules have an active site that interacts with myosin
=tropomyosin covers these sites when “resting”
- Myosin has a globular head and tail
- Calcium is the key that unlocks active sites and begins a contraction
= bond to tropomyosin, causes change in shape
how do muscles control contraction?
Control of Muscle Contractions
- neuromuscular junctions link nervous and muscular systems
- release of acetylcholine triggers release of Calcium ions
sacolemma
cell membrane
sarcoplasm
cytoplasm
transverse tubules
network of tunnels that coordinate contraction
resting sarcomere
the unit of the muscle that contracts to allow movement
once calcium leaves, it causes
shape change, blocking actin from bonding with myosin
tropomyosin acts as
the lid to the cookie jar
rigor mortis
-circulation ceases upon death
- run out of ATP which leaves SR unable to remove Calcium
- What happens?
= causes a sustained contraction bc no ATP available to detach cross bridges
= lasts for 15-25 hours (enzymes break down everything)
Muscle Mechanics
-muscles pull, causing tension
=must overcome resistance
-cannot push away from an object (compression)
= because muscle cells can only contract, sarcomeres can not widen
twitch
single stimulation sequence of a fiber
muscle fiber
twitch 3 phases: - latent: calcium removed -contraction: sliding filament - relaxation: actively takes out calcium from the SR
Tetanus
- summation
- incomplete tetanus
- complete tetanus
Summation
addition of one twitch to another
incomplete tetanus
produces almost peak tension
complete tetanus
occurs when relaxation phase completely eliminated
tetanus
lock jaw
- caused by a bacterium (clostridium tetani)
- thrives in low oxygen, like deep tissue
- releases toxin affecting motor neurons, yielding contraction of muscles
- 40-60% mortality rate
- no after effect, after 2-4 weeks
motor units, muscle fibers are controlled by what?
a single motor neuron
- size of unit determines how fine level of control is
- fewer fibers= greater control
what occurs when all motor units of a muscle are activated?
peak tension
sustained contractions
motor units will activate on rotating basis
the resting tension in muscle causes
no movement is caused
- stabilizes position of muscles and bones
atrophy
regular stimulation by a motor neuron is NOT achieved- becomes weak ex: broken arm or leg
types of contractions
isometric
isotonic
isometric
no joint movement (plank, wall squats, static lunges, yoga)
- muscle remains same in length
- tension never exceeds resistance
ex: pushing against a wall/ holding
isotonic
joint moves
- muscle holds same tension
- contracts up to a point where resistance is over come (moves)
ex: lifting an object, walking, running
where does each muscle begin?
at an origin (stationary)
where does each muscle end?
at an insertion (moves)
What do muscles produce?
a specific action, like flexion or extension
agonist
(prime mover)
contraction primarily responsible for movement
antagonist
muscles oppose
action produced by another muscle
- can also be a prime mover (ex: triceps)
what are functional opposites
agonist and antagonist
synergist
helps prime agonist work efficiently
aerobic
requires oxygen to generate energy
- energy is produced by cellular respiration in mitochondria
ex: distance running and swimming
anaerobic
does not require oxygen
- energy is produced by glycolysis in cytoplasm
ex: weight lifting/ sprinting
sufficient oxygen means
ATP needs are met by mitochondria
insufficient oxygen means
glycolysis begins
and lactic acid builds up
muscle performance is determined by
- types of muscle fibers
- Physical conditioning
slow twitch
- loaded with mitochondria(cellular respiration)
- fatty acids are the major source of energy source
- resistant to fatigue
- rich in myoglobin which is red in color
fast twitch
- few mitochondria
- glycogen is the major source of energy
- fatigue easily= produces lactic acid
- low in myoglobin which is white in color
functions of skeletal system
- supporting weight of body, provided by bones
- storing energy reserves such as lipids in areas filled with yellow marrow
- blood cell production; red, and white blood cells produced, filling internal bone cavity
- protection; ribs protect the heart and lungs; skull/ brain
- leverage; bones function as levers, changing the magnitude and direction of forces generated by muscles
how do bones work together with muscle
to maintain body position, and produce controlled, precise movements
macroscopic features of bone
long bone
short bone
flat bone
irregular bone
long bone
longer than they are wide (humerus, femur)
short bone
dimensions equal to long bones, just shorter (carpal bones, tarsal bones)
flat bones
thin, relatively broad, (parietal bones, scapulae)
irregular bones
have complex shapes that do not fit easily into any other category (vertebrae/ spinal column)
diaphysis
surrounds the central marrow cavity, which contains bone marrow
formed by compact bone
done marrow
a loose connective tissue
epiphyses
expanded portions at each end
- articulates with an adjacent bone at a joint
filled by spongy bone
compact bone
relatively solid
spongy bone
resembles a network of bony rods or struts created by the spaces
peritoseum
covers the outer surface of the bone
endosteum
lines the marrow cavity and other inner surfaces
endochondrial ossification process
- chondrocytes at the enter of the growing model enlarge then die as the matrix calcifies
- newly derived osteobloasts cover the shaft of the cartilage in a thin layer of bone
- blood vessels penetrate the cartilage. new osteoblasts from a primary ossification center
- the bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone
- blood vessels invade the epiphyses and osteoblasts form secondary centers of ossification
epiphyseal cartliage
continue to enlarge, increasing the length of the developing bone
articular cartiliage
original cartilage, exposed to the joint cavity
difference between axial and appendicular skeleton
axial makes up our central axis and consists of skull, vertebrae, rubs, and sternum.
- appendicular consists of limbs and girdles
number on bones in newborns/ adults
newborns: 305, made up of mainly cartilage, which turns into bone as the person ages
adult: 206 bones
what are haversian canals/ what travels trough them?
Verious canals in compact bone through which blood vessels, nerve fibers, and lymphatics pass
how do bones repair and remodel?
osteoclasts break down old bone, so that osteoblasts can replace it. Chondroblast forms new cartilage
difference between spongy and compact bone
compact bone makes up the firmer outer layer of bone tissue, spongy bone is the softer, more porous inner bone
cells that make up bones?
osteoblasts, osteoclasts, osteocytes, and osteogenic cells. osteoclast breaks down
osteoblast creates
types of joints
fibrous (immoveable), cartilaginous (partially moveable), and synovial (freely moveable)
ball and socket joint
spherical head of bone fits into a socket-like bone ex: shoulder/ hips
condyloid joint
difference to ball and socket: they are not as spherical, more oval
ex: finger, toes, wrist
hinge joint
similar to door hinge, allow flexion and extension
ex: ankle, knee
saddle joint
bone moves or glides in 2 directions, range of motion is similar to condyloid
ex: thumb base
gliding joint
“plane joint” one bone glides over another, joint capsule limits movement of the joint
ex: wrist, ankle
pivot joint
rotate or pivot around another bone.
ex: base of skull, enables head to move from one side to the other
tendons vs ligaments
tendons attach muscles to structures like the eyeball, moves the bone or structure
- ligament is a fibrous connective tissue that attaches bone to bone, holds structures together and keeps them stable
fontanels
the soft spot on a baby where ossification is not complete
foramina
an opening/ passageway in the bone
what occurs around freely moveable joints
layer of hyaline cartilage at the adjourning ends, there is a high degree of mobility and flexibility, place where bones connect. classified as immovable, slighlt moveable, and freely moveable
functions of muscular system
movement, Produce movement Maintain posture and body position support soft tissues guard entrance/ exits maintain body temperature
similarities and differences of muscle fibers between people
slow twitch- slow to contract, sustain contractions for extended time
fast twitch- ability to rapidly transmit action, fatigue faster but used in powerful bursts of movements
origin
end of a muscle which is nearer to the midline of the body, more proximal, less movable
insertion
end of muscle furthest from the dorsal midline, more distal, more movable
agonist/ agonist differences
work in the opposite direction to complete an action
- agonist react in response to stimulus and create the movement necessary to complete a task
- antagonist act against the agonist muscle and help to move the body part back in place after the action is completed.
ex: biceps and triceps (tricep relaxes while bicep contracts to lift arm)
what makes up the myofibrils
think and thin myofilaments, give striated appearance
what are the interactions between muscles and nerves called?
neuromuscular junctions link nervous and muscular systems, receptors in muscles provide the brain with info about body position and movement. brain controls the contraction of skeletal muscle. the nervous system regulates the speed at which food moves through digestive tract
motor unit
made up of a motor neuron and skeletal muscle fibers innervated by that motor neurons axonal terminals
- number of muscle fibers vary within particular muscle
=smaller muscles contain fewer muscle fibers in each motor unit
term tetanus refers to
sustained muscle tension due to very frequent stimuli
isometric
muscle does not change its length
do not involve movement
- ex: plank, side plank
isotonic
muscles changes its length without increasing tension
- ex: pushups, squats, lunges
skeletal muscle
skeletal
- very large, multinucleate cells pushed off to the side of the cell, packed with protein
=up to 10 inches long
- muscle cells= muscle fibers
- muscle fibers are incapable of dividing
=stem cells present to partially repair injury
-marked by striations
- under voluntary nervous control
smooth
smooth muscle
- found in organs
- small in size, single nucleus
- since actin is scattered throughout cell, no striations
- smooth muscle cells can divide, therefore can regenerate after injury
- involuntary muscle control
cardiac
cardiac muscle
- found only in the heart
- striated
- typically smaller, can be branched, usually one nucleus
- INTERCONNECTED THROUGH INTERCALATED DISCS
- no stem cells, limited and incomplete rapirs
- do not rely on nervous system- but pacemakers cells
- involuntary control
