chapter 11a,b and c - exam 2

What are the four steps of the cross bridge cycle?

1- myosin attaches to actin

2- myosin pivots forward and pulls thin filament

3- ATP attaches to myosin causing it to detach

4-hydrolysis of ATP “cocks” myosin head back into ready position

sliding filament model of contraction

• states the during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more

• neither think nor thin filaments change length, just overlap more

How do think and thin filaments make striations?

the striations come from the repeating side to side arrangement created from 2 different types of filaments inside each sarcomere.—— the two types are actin (thin) and myosin (thick)

sarcomere

smallest unit of muscle fiber and aligns end to end along myofibrils

Myofilaments

orderly arrangement of actin and myosin myofilaments within sarcomere

what happens during contraction?

myosin binds to actin, forming “cross bridges”

dystrophin

links thin filaments to proteins of sacolemma

sarcoplasmic reticulum

network of smooth endoplasmic reticulum tubules surrounding each myofibril

• stores calcium

T tubules and what happens when electrical nerve reaches muscle

allow electrical nerve transmissions to reach deep into interior of each muscle fiber

• when electrical impulse passes by. T tubules proteins change shape, causing SR proteins to change shape, causing release of calcium into cytoplasm

How Does an Electrical Impulse Cause Calcium to Be Released?

An electrical signal travels into the muscle through the T-tubules, causing the sarcoplasmic reticulum (SR) to release calcium. This calcium helps the muscle contract.

explanation for how electrical impulse cause calcium to be released

1. Electrical impulse: An electrical signal travels along the muscle cell membrane and down the T-tubules.

1. T-tubules: Proteins in the T-tubule membrane change shape when they detect the electrical signal.

2. Sarcoplasmic reticulum (SR): This shape change activates proteins in the SR membrane, causing calcium channels to open.

3. Calcium release: The SR releases stored calcium ions (Ca²⁺) into the muscle cell's cytoplasm (sarcoplasm).

4. Muscle contraction: Calcium allows actin and myosin to interact, which leads to muscle contraction.

what are the three main pathways that provide ATP? how does it work? how much atp? speed and duration?

1. direct phosphorylation on ADP by creatine phosphate

   • creatine phosphate transfers a phosphate to ADP.

   • 1 ATP per creatine phosphate.

   • fastest: supports the first few seconds of intense activity

2. anaerobic pathway (glycolysis)

   • glucose is broken down without oxygen

   • 2 ATPs per glucose

   • relatively fast but less efficient than aerobic respiration, supports short intense activity

   • lactic acid is a by product of anaerobic pathway

3. aerobic respiration

   • glucose and other nutrient fuels are broken down using oxygen

   • about 32 ATPs per glucose

   • slower but much more efficient, supports prolonged activity.

what are the two types of energy systems?

1. aerobic endurance - light to moderate activity, which can continue for hours

2. anaerobic threshold - point at which muscle metabolism converts to anaerobic pathway. once you shift to heavier exercise and you’re not producing ATP fast enough you switch to this pathway.

what are the two main differences between anaerobic and aerobic pathways? When does one switch to the other?

anaerobic = no oxygen

aerobic = uses oxygen

anaerobic = lactic acid

aerobic = no lactic acid

anaerobic = produces less ATP per glucose but makes ATP faster

aerobic= more ATP

what does the muscle need in order to return to its pre exercise state? and what do all

oxygen reserves are replenished

lactic acid is reconverted to pyruvic acid

glycogen is replaced

ATP and creatine phosphate reserves are resynthesized.

all of these steps require extra oxygen, this is also referred to as “excess postexercise oxygen consumption”

isometric contraction

no shortening, muscle tension increases but does not exceed load. (muscles are contracting but not actually shortening

isotonic contraction

muscle shortens because muscle tendon exceeds load

the muscle twitch

when your body sends signals to muscles they will contract fast and take more time to fully relax than it does contract

what is muscle “recruitment”?

“recruitment” is a stimulus sent to more muscle fibers, leading to more precise control and increases your force

what is muscle tone?

the idea that muscles are always in a constant state of contracting

what do spinal reflexes do?

these are motor units that are activated in response to input from stretch receptors in muscles.

why do we have stretch receptors?

because it has the function of telling the nervous system when our muscles are getting to stretched… this is why our body cramps up, its the way our body prevents us from over stretching.

muscle fiber types are classified by what 2 characteristics and what is their purpose?

1- speed of contraction (slow or fast fibers)

2- How ATP is produced. AKA what metabolic pathway used for ATP synthesis (Oxidative fibers use aerobic pathways and O2, Glycolytic fibers use anaerobic glycolysis and no O2)

• its purpose is to contract and produce movement

Muscle fibers can be classified into what three types?

Slow oxidative fibers, fast oxidative fibers or fast glycolytic fibers

describe Slow oxidative fibers

best for endurance, use oxygen, can work for lonf periods of time without getting tired fast

• ex: turkeys use their legs frequently for standing and walking, thats why they contain oxidative fibers

describe fast glycolytic fibers

does not require oxygen, useful for short intense, powerful movements, get fatigued faster than oxidative fibers

• ex: turkeys dont use their flight muscles for sustained flying, so their breast muscles contain more fast glycolytic fibers.

brief description of muscle type: Slow oxidative fibers

low intensity, endurance activities, contracts slowly, very resistant to fatigue

brief description of muscle type: fast oxidative fibers

medium intensity activities, contracts quickly, moderate to high resistance to fatigue

brief description of muscle type: fast glycolytic fibers

short term intense or powerful movements, contracts very quickly and powerfully, fatigue relatively quickly

muscle hypertrophy

increase in muscle fiber size, commonly from resistance exercise

muscle atrophy

decrease in muscle size and strength due to disuse

what about smooth muscle

• found in walls of organs

• function is to move stuff in body

• have the same components as skeletal muscle

what are the two layers of sheets with fibers that most organs contain?

Longitudinal layer and circular layer

what does the body do depending om the sorts of activities your’re doing?

• your body can switch from using one type of fiber to another type of fiber that is better for the job and produce things needed for that certain type of exercise

  • ex: when doing lots of high intense exercise your body produces more capillaries, more myoglobin and some fast glycolytic fibers will turn to fast oxidative fibers.

• this is also called “muscle fiber adaption”

what are the three different types of muscle? where would you find each type in our bodies?

skeletal - found in skeleton and attached to bones

smooth - found around organs

cardiac - found in heart walls

skeletal muscle and what are they made up of and the three features?

• attached to bones and skin

• held together with connective tissue

• skeletal muscle fibers are longest of all muscles and have striations

• voluntary muscle

• skeletal muscles organs are made up of tissues and the main features of the tissues are nerve and blood supply, connective tissue sheaths and attachments

cardiac muscle

• fibers are shorter

• striated

• involentary

smooth muscle

• involuntary

• non-striated - allows muscle to be more stretchy

nerve and blood supply to the muscle

• each muscle receive a nerve, artery, and veins

• all muscles have nerves which tells them to contract or not

• contracting muscle fibers require huge amounts of oxygen and nutrients

muscle attachments

• muscles span joints and attach to bones

briefly describe the sliding filament theory? What filaments get shorter during muscle contraction?

the theory states that during muscle contraction, thin filaments (actin) slide past think filaments (myosin) pulling the ends of the sarcomeres closer together and shortening the muscle.

myofibrils

are densely packed, rod like elements, they make up most of the volume in a muscle cell.

how are thick and thin filaments making striations?

the striations come from the repeating side to side arrangement created from the 2 different types of protein filaments inside each sacromere. The two types is thin filaments=actin and the thick filaments=myosin

what is a sarcomere

smallest contractile unit of each muscle fiber. sarcomeres align end to end along myofibrils

what is dystrophin?

protects and strengthens muscle fibers during contraction and relaxation