biol ch. 37

isometric force

musle contracts but cannot shorten, muscle still generates force even though it stays the same length and does not shorten

what is a twich

single action potential

is sarcomere length variable in invertebrates?

yes they can have longer sarcomeres, but vertebrates can just shorten to produce movements more quickly bc the sarcomeres are shorter

Can muscles shorten quickly?

yes, they can produce large forces for their weight -insects super fast, compared to vertebrates, then clams are slower but there muscles can do that without getting tired

what are fibers made up of?

long rodlike structures that contain parallel arrays of the actin and myosin filaments that cause a muscle to contract (this is not a sarcomere but these can be further broken down into sarcomeres)

what do skeletal tissues consist of?

mainly an extracellular matrix: secreted by specialized cells, forming a connective tissue external to the cells -bone, tooth enamel, cartilage

What are individual muscle contractions the result of? (so the bigger picture)

many successive cycles of cb formation and detachment -During which chemical energy released by atp hydrolysis is converted into mechanical work

osteoclasts

removal, that secrete digestive enzymes and acid to dissolve the calcium mineral and collagen

What are skeletal muscle fibers organized into?

repeating contractile units called sarcomeres (they make up myofibrils)

endoskeletons

rigid bones are jointed for motion and can be repaired if damaged -first evolved in cambrian explosion, lies internal to most animal tissues -they can grow extensively and when broken be repaired -provide protection from internal organs like brain, lungs and heart

What kind of muscle fibers do skeletal muscles have?

slow twitch and fast twitch

how do muscles interact with hydroskeleton?

-muscles exert pressure against the fluid to produce movement -circular muscles reduce diameter -longitudinal reduce length

What are myosin made up of?

-2 long polypeptide chains coiled together, each ending with a globular head- but it looks like a double headed golf club, and they are arranged in parallel to form thick filaments with numerous myosin heads extending out from their flexible necks along the myosin filament

how do the different types of muscle fiber affect the speed of predators and prey?

-Inheritance of genetic fiber types -High aerobic animals like dogs and antelope have a lot of slow twitch fibers and specialized fast twitch muscle fibers that also have a high oxidative capacity in addition to using glycolysis for rapid atp production -Cats are more fast twitch -Animals with high body temp. and high metabolic rates have larger numbers of oxidative (fast twitch) fibers compared with animals that have lower body temperatures and lower metabolic rates (Reptiles) -Most fish have red slow twitch

What does it mean that they are multinucleated?

-This means gene expression must be coordinated among all nuclei in the muscle fiber -This is necessary when endurance training increases the cells rate of atp production, so that the entire cell contracts uniformly

what do muscles do?

-generate force, produce movement - some are obvious: running, climbing -some aren't muscles in digestive tract

what are the 2 layers?

-thin outer waxy layer minimizes water loss -thicker inner layer tough, making it hard to break

hinge

1 axis of rotation ex. elbow, ankle - can be controlled by 2 antagonist groups

Cross bridge cycle (the how of muscle contraction)

1. Myosin head binds to atp, allows myosin head to detach from actin 2. Myosin head hydrolyzes atp to adp and inorganic phosphate. This results in conformational change so myosin head is cocked back 3. Myosin head binds actin forming a cross bridge 4. Once bound, the myosin head release adp and pi, result is another conformational change in the myosin head called the power stroke. During this myosin head pivots forward and generates a force, causing myosin and actin filaments to slide relative to each other over a distance of approx. 7nm. Power stroke pulls actin filaments toward sarcomere midline 5. Then step 1 again and the cycle repeats

What are the 2 types of muscles?

1. striated 2. smooth

what happens along the myosin?

2 heads of myosin molecules bind to actin at specific sites to form cross bridges between the myosin and actin filaments -myosin filaments pull the actin filaments toward each other by eans of the cross bridges btwn myosin and actin filaments

ball and socket

3 axis of rotation ex. shoulder

when were fibers first seen?

600 million years ago (these are the actual muscle fibers, not the whole bundles)

when do muscles contract?

Calcium regulates actin-myosin interaction through excitation -contraction coupling

what kind of length generates the most force?

INTERMEDIATE- because most overlap

what affects the muscles and why?

Muscle length affects actin-myosin overlap and generation of force -Amount of overlap determines number of cross bridges that can form- so the more overlap the more force that can be produced- except when lengthened then relaxed it is weaker bc less overlap

sliding filament model

Muscles produce force and change length by the sliding of actin filaments relative to myosin filaments

Do the lengths of myosin and actin change?

NO-they never vary, the change is from the sliding of actin with respect to myosin filaments within individual sarcomeres -So the sum of the fractions by which each sarcomere shortens along the fibers length

So what is in the middle then?

NOT directly touching the Z discs are myosin thick filaments- this forms 2 regions of overlap within the sarcomere

removal is _____ then growth

SLOWER

What does muscles ability to generate force depend on?

a combination of electrically excitable cells and contractile proteins within these cells that can be activated by the nervous system

bone marrow

a fatty tissue found btw trabeculae and also within the bones central cavity, contains important cell populations: stem cells, blood forming cells

striated muscles

appear striped under a light microscope -include skeletal (pulls on bones) and cardiac (contract heart muscles to pump blood)

smooth muscles- what are they and where are they found

appear uniform under the light microscope -Found in the walls of arteries to regulate blood flow, in the respiratory system to control airflow and in the digestive and excretory systems to help transport food and waste products

tendons

attach muscles to bones, made of collagen -they transmit muscle forces, allowing the forces to be redirected and transmitted, store and recover elastic energy

why is bone hard to break?

bone absorbs energy before it fractures so that is why it is hard to break -bone becomes more mineralized and brittle as a normal process of aging -sharks evolved unusual skeletons of calcified cartilage rather than mineralized bone tissue to achieve rigid mechanical support

osteoblasts

bone tissue forming cells synthesize and secrete calcium phosphate as hydroxyapatite mineral crystals in close association with the protein collagen

appendicular

bones of the limbs, shoulder and pelvis - was fins in fish that evolved to mammals

how is muscle force summed?

by an increase in stimulation frequency and the recruitment of motor units

how are skeletal muscles stimulated

by motor nerves which conduct action potentials to the neuromuscular junction

What is the difference when a muscle is contracted vs. relaxed?

c: sarcomeres had more actin myosin overlap r: less overlap

spongy bone

consists of small plates and rods known as trabeculae with space btw them- mainly in ends of limb bones and within the vertebrae

insect cuticle

cover their entire body, composed of chitin, a nitrogen containing polysaccharide -originally soft for insects to grow, then hardens but stays soft at joints

What happens when myosin runs into Z disc?

disrupts cross bridge system- this would occur when contraction is in small lengths

characteristics of the fibers

each muscle fiber is an elongated single cell that can be up to 20cm long -they have several nuclei so they are multinucleated

muscle cells are________. specifically skeletal muscles

electrically exitable -Skeletal muscle fibers activated by impulses transmitted by motor nerves to synaptic junctions -In this case neurotransmitter binds with receptors on the muscle opening of Na+ channels, the influx of na initiates wave of depolarization that passes along the length of the muscle fiber

do all vertebrate animals have these?

even vertebrate animals with rigid endoskeletons have hydrostatic elements for flexibility and cushioning of loads transmitted by the skeleton -intervertebral discs: have walls that surround fluid, enable backbone to twist and bend -cartilage: forms joint surfaces between adjacent bones

skull and ribs

form when precursor cells differentiate into osteoblasts that immediately begin producing bone as a skeletal sheet or membrane

other bones

formed as cartilage first called chondroblasts but cartilage is pliable so it grows with the expansion of the skeleton -then cartilage is invaded by blood vessels→ cartilage into mineralized bone

thin filament

formed by 2 helically arranged actin filaments twisted together

compact bone

forms the walls of the bones shaft, mainly dense mineralized bone tissue containing bone cells called osteocytes and the network of blood vessels supplying them with oxygen and nutrients

red slow twitch fibers

found in muscles that contract slowly and consume less atp ex. posture - get energy through oxidative phosphorylation -Greater resistance to fatigue in response to repetitive stimulation -Because they can get mitochondria to supply atp to muscle fibers by aerobic resp. -Contain an abundance of myoglobin and oxygen binding protein related to hemoglobin that facilitates oxygen delivery to the mitochondria -They are red because of iron in them -Long distance runners, weight lifters (this increases size of already existing muscle fiber by synthesis of myosin and actin)

sarcomere

from 1 Z disc to another- this is the basic contractile muscle of a unit of muscle

How do actin thin filaments extend?

from both sides of the Z disc toward the midline of the sarcomere

white fast twitch fibers

generate force quickly, tail movement, but they consume more atp -Energy through glycolysis -Express a fast form of myosin with a high rate of atp hydrolysis, favoring rapid force development and movement -Fatigue quickly because of the drop in pH caused by the accumulation of lactic acid -Larger then red fibers- so generate more force

growth in length occurs at _________

growth plate, region of cartilage btwn middle region called diaphysis and end called epiphysis -adds cartilage toward diaphysis enabling bone length to continue to increase after birth, at maturity plates fuse -bone is added to ends and removed from middle, expanding marrow cavit

3 types of animal skeletons

hydrostatic, endoskeletons, exoskeletons

where is depolarization initiated?

in the plasma membrane-is conducted to the sr through a specialized transmission system, formed from invaginations of the plasma membrane, known as T tubule system- this is in contact with SR and muscle cells plasma membrane

force summation

increasing stimulation -> muscle force increases - it will reach a plateau and continue as stead as stimulation continues

what are finger joints?

intermediate they allow you to flex and extend your fingers as well as spread them laterally or move them together when making a fist

how are myosin and actin organized?

into thin threads called filaments that interact with each other and cause muscles to shorten (this is what happens when you lift weights etc.) -striated: they are in repeating pattern to produce the striated pattern -smooth: they are in irregular pattern, giving these muscles a smooth appearance when viewed

how do vertebrate bones form

intramembranous and endochondral ossification

what is advantage of doing bone growth this way

it can be repaired if damaged, but women usually lose more after menopause

what are the functions of these interactions?

jet propulsions, allows clams to burry etc.

flexion

joint motion in which bone segments rotate closer together

articular cartilage

located at joint surfaces of a bone forms a gel like matrix that resists fluid being squeezed out when forces press on the cartilage during movement -reinforced by type 2 collagen fibers

difference between mollusks/ clams and insects

mollusks, clams have an outer shell made of calcium reinforced by proteins- so it is less brittle and harder to break then if it had been made of 1 thing -insects have more complex

motor unit

motor neuron and the population of muscle fibers that it innervates, they can be relatively few to a 100 -Number of fibers innervated by a given motor unit determines force and how much control a muscle has -Ex. Finger are very small motor units, legs large

fibers

muscle cells, they produce force within an animals body as well as exert forces on the environment

What are inversely related?

muscle force and shortening velocity -muscles shorten quickest when producing low forces -ex. Your arm moves faster when you throw a light ball instead of a heavy one

lengthen contraction

muscle generates much more force than when it remains isometric or shortens ex. every stride you take while running- a brief phase of streth at the begining of contraction is normal because it allows muscles to generate more force then if they remained isometric -this lengthening also reduced the muscles energy consumption because fewer fibers are recruited to generate a given level of force -injury is usually caused by rapid and repetitive stretching

skeletal muscle fibers

produce movement by shortening, thus pulling on bones of the skeleton

What is on both ends and towards middle of sarcomere?

non overlap regions and these are lighter in color then regions of overlap

What is the next step and result?

power stroke - this results in excitation, contraction coupling, producing force and movement - muscle relaxation follows the end of neural signal- ca goes back into SR

antagonistic muscles

produce reciprocal motions at a joint - this is because muscles can only generate force by pulling NOT pushing, occurs in cnidarians and roundworms as well

What are thin filaments attached to?

protein backbones called Z discs that are regularly spaced along the length of the myofibril

exoskeletons

provide hard external support and protection - first ones came with sponges - protection, support, and place for muscles to attach but they limit growth

what does joint shape determine?

range of motion and skeletal muscle organizaton

what is most mobile joint?

shoulder- but most often dislocated or injured

What do all muscles have?

similar force generating properties b/c actin and myosin are preserved

how do muscles exert forces to produce joint motion?

skeletal lever -so skeleton enables muscles to transmit forces that cause joint rotation -muscles that attach father produce slower but stronger movements

What systems activate each type of muscle?

skeletal: somatic nervous system smooth and cardica: autonomic nervous system

axial

skull and jaws of head, spinal column, ribs -formed first so it is the main component of fish

how do muscles contract?

sliding of myosin and actin filaments

what were they key for?

speciation in insects

hydrostatic

support animals by muscles that act on a fluid filled cavity

sarcoplasmic reticulum

surrounds myofibrils- it is a modified form of endoplasmic reticulum

what is strength of rotational movement determined by?

the product of a muscles force and perpendicular lever -muscles produce longer force by being farther or exerting larger force -chek 37-18 on this

What about at resting?

the binding sites are blocked by tropomyosin -BUT Depolarization causes conformation change in troponin which in turn moves tropomyosin away from these binding sites, allowing cross bridges between actin and myosin to form and the muscle to contract (myosin and actin need to be exposed to form cross bridges)

what does force exerted on the muscle depend on?

the frequency of stimulation by the motor nerve because more frequent stimulation increases the amount of calcium that is released to activate cross bridge formation in the muscle fibers

extension

the motion when bones move apart

tetanus

the muscle contraction of a sustained force, this is normal response but can induce by tetani

when did they evolve?

these evolved early, found in almost all multicellular animals as well as in many vascular plants

What is similar between striated and smooth muscles?

they both use the same sets of muscle proteins: myosin and actin to contract and generate force

What do smooth muscles use?

they do not have troponin- tropomyosin mechanism so instead they use the binding of a protein called calmodulin -calmodulin-CA complex activates enzyme myosin kinase that phosphorylates the smooth muscle myosin heads, causing them to bind actin and begin the cross bridge cycle - a second enzyme dephosphorylates-> relaxation - these muscles usually have longer periods of contraction because calcium is returned more gradually

What is different in insects?

they have higher rates to produce more atp- SO myosin can be an enzyme and a protien

what links the myosin filaments to the z discs at the ends of the sarcomere?

titin- it helps with muscle elasticity

what also applies to the way muscles pull on the skeleton to cause joint movement?

trade off of force versus velocity that we saw earlier -muscles that transmit large forces typically have large leverage for strong joint rotation

what runs in the grooves formed by actin helices in thin filament?

tropomyosin- it is a protein that blocks myosin binding sites when needed (so when muscle isnt contracting)

molting

when arthropods shed their cuticle at intervals

When is muscular contraction initiated?

when depolarization of the t tubules causes the SR to release ca, this diffuses into myofibrils and binds to troponin causing change shape, causes tropomyosin to move exposing the myosin binding site along the actin filament

agonists

when muscles combine to produce similar motions

when are animals vulnerable?

when shell sheds but new one hasn't formed, also hard to repair