Muscles Flashcards
smooth muscles (6)
- long and tapered
- one nucleus
- found in parallel lines
- the walls of internal (hollow?) organs
- they contract and help to regulate blood pressure and direct blood flow. can be found in the iris of the eye. the smooth muscle controls the size of the eyes opening to light
- slower to contract than skeletal muscle but it can sustain prolonged contractions and does not fatigue easily.
cardiac muscles (5)
- tubular and striated (long and dark bands)
- long
- one nucleus
- branched
- found on the heart
skeletal muscles (5)
- tubular and striated
- long
- have many nuclei
- called fibres
- found in between the bones, like arms
can be referred to as striped or striated muscle
which of the three muscles are involuntarily controlled? what are they controlled by?
- smooth and cardiac
- controlled by autonomic system
which of the three muscles are voluntarily controlled? what are they controlled by
- SKELETAL muscles
- controlled by somatic nervous system
function of skeletal muscles (5)
- support the body
- make bones move
- maintain a constant body temp
- protect internal organs
- stabilize joints
do skeletal muscles pull or push and why
they pull because when contracted, they shrink
which muscles usually occur in pairs? how does this work
skeletal muscles usually occur in pairs
- when one muscle is contracted, the other is relaxed
- for ex, when the elbow is bent, the biceps are contracted while the triceps are relaxed (extended). when the elbow is straightened, the triceps are contracted while the biceps are relaxed.
what is the structure of the muscles? largest to smallest (5)
- muscle
- muscle fibre bundle
- muscle fibre
- myofibrils
- myofilaments
what runs between the bundles of muscle fibres
blood vessels and nerves
myogoblin
- desc. oxygen binding pigment in a skeletal muscle fibre
- func. stores oxygen
sarcolemma
- desc. membrane of muscle fibre
- func. similar to cell membrane
sacroplasm
- desc. cytoplasm of muscle fibre
- func. site of processes
myofibrils
- desc. bundle of myofilaments
- func. stores calcium ions
thick filament
- desc. myosin
- func. binds to actin
thin filament
- desc. actin
- func. binds to myosin
deeper phys desc of thin filaments
the thin actin myofilaments (5nm in diameter) consist of 2 strands of protein (actin) molecules that are wrapped around each other
deeper phys desc of thick filaments
the thick myosin myofilaments (11nm in diameter) consist of two strands of protein twisted around each other, but it is about 10x longer than an actin filament and has different shape.
- one end of the myosin myofilament consists of a long rod while the other end consists of a double-headed globular region
sliding filament theory explaination
- this occurs when myosin myofilaments contract. during this process, the head of the myosin myofilament moves first in a backward and inward manner. like flexing hand at the wrist
- this moves them a few nanometers in the direction of the flex and pulls the attached actin myofilament along w it.
- the myosin head relaxes, letting go of the actin and unflexes (powered by ATP)
—– relaxing muscles require ATP, not contracting them though. This is why rigor mortis after you die. muscles contract and stiffen because there is no ATP present - the process repeats and the actin slides past the myosin. this is the basis of the sliding filament model
- shows how contraction occurs (when the z lines are nearest myosin core)
where is each actin myofilament anchored
each one is anchored at one end in a position called the Z line. (the edge of each sarcomere)
- because the actin is anchored down like this, as actin moves past the myosin, the z line gets closer to the myosin
- w/ one actin myofilament being pulled inward in one direction and the other actin myofilament on the other side of the myosin myofilament (or the m line) being pulled in the opposite direction, the z lines move toward each other as they slide past the myosin core (m line?)
what role does calcium play in muscle contraction
- when myosin heads are raised and ready to attach to the actin, they cant because the attachment sites are blocked by protein (tropomyosin)
- ca2+ comes in and binds to another protein on the actin called troponin. this bonding repositions the tropomyosin proteins
- the reposition of these proteins exposes the myosin’s binding sites of the actin and then contraction occurs
where are calcium ions stored when muscles are at rest
sarcoplasmic reticulum
how does food move through the intestines
because of the contraction of the smooth muscle
how does the heart accomplish its unceasing movement
because of the cardiac muscle
how is the body able to mvoe
because the skeletal muscle pulls on the bones of the skeleton
tendon
a tough, heavy band of tissue. attaches each end of a muscle to a different bone. made up of connective tissue
connective tissue
a layer of connective tissue wraps around each muscle fibre. another layer wraps around each bundle of fibres. Another wraps around the whole muscle itself.
blood vessels and nerves
run between the bundles of muscle fibres. the rich blood supply provides muscle fibres with nutrients and oxygen to power contractions, and it removes cellular wastes.
- the nerves trigger and control muscle contractions
T/F each muscle fibre is considered a single cell
T
myofibrils
- most of the volume of a muscle fibre consists of hundreds of thousands of cylindrical subunits called myofibrils
- each myofibril is made of even finer myofilaments
myofilaments
contain protein structures that are responsible for muscle contractions. the rest of the volume of a muscle fibre consists of numerous mitochondria (300 per muscle fibre)
how is atp used in muscle contraction
to break the myosin-actin cross-bridge, freeing the myosin for the next contraction. atp is used quickly.
- one atp molecule is split by each cross bridge in each cycle
how are calcium ions returned back to the sarcoplasmic reticulum
active transport. when the nerve impulses (initiate muscle contraction stop) and the muscles stop contracting, the calcium ions are returned to the sarcoplasmic reticulum through active transport.
musclles acquire atp in three different ways
depends on the availability of oxygen
1. the breakdown of a moleculre called creatine phosphate
2. aerobic cellular respiration
3. fermentation (anaerobic respiration)
how does creatine phosphate build up
when muscle is resting
is creatine phosphate breakdown aerobic or anaerobic
anaerobic.
aerobic
require oxygen– in the presence of o2
- in mitochondria of muscle fibres
- provides atp from breakdown of glucose
- requires the presence of o2 to break down food energy (sually glucose and fat) to generate atp for muscle contractions
anaerobic
no o2
fermentation
anaerobic
- if exercise is so vigorous that oxygen cannot be delivered fast enough to be working the muscles, fermentation occurs.
- causes an oxygen deficit (aka oxygen debt)
- glucose broken down without presence of o2
- produces lactic acid, can cause cramping, fatigue
athletes have more mitochondria, use anaerobic respiration less
creatine phosphate
- a high-energy compound that builds up when a muscle is resting
- the compound cannot participate directly in muscle contraction, instead, it generates atp
creatine phosphate > creatine
adp > atp
- reaction occurs in the midst of sliding filaments
- speediest way to make atp available to muscles
- creatine phosphate provides enough energy for only about eight seconds of intense aactivity. then it is spent
- it is rebuilt when a muscle is resting, through the transfer of a phosphate group from atp to creatine
- can rebuild adp, quickly forming atp
where does aerobic cellular respiration take place
mitochondria
atp molecules and cross bridges
- one atp molecule is split by each cross bridge in each cycle
- only takes a few milliseconds
- during a contraction, there are 1000s of cross bridges in each sarcomere going thru this cycle
- however, the cross bridges are all out of synch, so there are always many cross bridges attaches at any time to maintain force
what happens if energy demand exceeds atp storage
lactic acid is produced
how do creatine and atp relate
creatine phosphate is found in all muscle cells and help to keep atp supplies high
how much atp can a muscle store
only a small amount
atrophy
- from lack of use of muscles
- reduction in size, tone, and power of muscles
hypertrophy
- muscles enlarge due to exercise
muscular dystrophy
- skeletal muscles degenerate, lose strength
botulism
- from bacteria, causes paralysis
cramps
- muscle spasms (cold, exercise, dehydration)
contracture
- muscle shortening (burns)
fibromyalgia
- chronic muscular pain and tenderness
crush syndrome
- shock-like state after muscles have been crushed
muscle soreness
- pain, stiffness, tenderness after exercise
myositis
- muscle inflammation and weakness due to infection or autoimmune
muscle twitch
- a single contraction that lasts less than a second
- 3 sections
-all or none contraction, if there are multiple, they dont relax – summation
3 sections of muscle twitch
- latent period
- contraction
- relaxation
summation muscle twitch
- a 2nd twitch, usually greater contractio and from stimulating the muscle before it has the chance to fully relax
tetanus muscle twitcj
- maximal sustained contraction
incomplete tetanus vs complete tetanus
- v short relaxation periods
- stimulus freq so high that relaxtation period disappears completely
importance of exersice
- endurance– improves aerobic capacity
- muscle enlargment– frewuent periods of high-intensity training
- homeostasis– moving helps maintain body temp
- involved in digestion, respiratory, excretory, and circulatory systems
slow twitch fibres
- type 1
- contract slowly but resist fatigue
- slow twitch, good for distance
- many mitochondria
- dark within capillary beds
- aerobic
- high blood supply
- high # of capullaries
- red in color
- marathon runners
(smaller muscles)
fast twitch fibres
- type 2a (IIa) or 2b (Iix)
- fast twitch
- break down atp quickly but less efficiently
- light in color
- fewer mitochondria
- accumulate lactate
- fatigue rapidly
- anaerobic
- low # of capillaries
- low blood supply
- sprinters
(bigger muscles)
what is the downside to fermentation producing atp
it forms atp quickly but results in an oxygen deficit because oxygen is needed to complete the metabolism fof the lactate that is produced and accumulates
why does aerobic respiration take longer for a muscle fibre to acquire atp
takes longer cus o2 must be transported to the mitochondria in the muscle fibres
