U4 Quiz - Muscular System

the muscular system functions

1. produces movement

2. maintians posture

3. stabilizes joints

4. generates heat

All muscle tissues have these 4 characteristics

1. excitability

2. contractibility

3. extensibility

4. elasticity

excitability

ability to respond to a stimulus

contractibilty

ability to shorten when stimulated

elasticity

abillity to recoil or bounce back to original shape

extensibility

ability to lengthen or stretch, even past original shape

Skeletal muscle tissue

• connected to bones

• straited

• voluntarily controlled

• contracts slowly or quickly

cardiac muscle tissue

• found in heart

• straiated

• involuntarily controlled

• mostly slow and steady contractions except during short periods of activity

smooth muscle tissue

• found in walls of internal organs (ex: stomach)

• non-straited

• involuntarily controlled

• slow contracts sustained for a long period of time

fasicle

bundles within muscles

muscle fiber

• aka cells

• long, thin muscle cells

• covered in sarcoplasmic reticulum that transmits impulse to muscle fiber

myofilaments

• two types: actin + myosin

• responsible for contracting activity of muscle fibers

myofibril

• theard-like orgaelles of muscle fibers

• structured in long, straiated units called sacometers

epimysium

covers WHOLE muscle

perimysium

covers a FASICLE

endomysium

covers individual MUSCLE FIBER

what do actin and myosin do?

work together to produce a muscle contraction

What does Myosin look like?

nerds gummy rope

What is the M-Line?

the line in the Middle or myofilaments - MEDIAL

How do muscle fibers contract?

myosin heads attach to twised actin filaments and pull on them. Z-lines get coler together and carcomere gets shorter. This repeats until muscle contracts completely

What is the name for how muscle fibers contract?

sliding filament theory

Where does the energy for the sliding filament theory come from?

ATP

Step 1 of sliding filament theory

Contraction cycle begins

• ATP energizes a myosin head and is converted into ADP + P (think of ATP g u n)

Step 2 of sliding filament theory

Active site exposed, cross-bridge formation

• calcium ions bond to tropinin, removing the blocking actin of the tropimysium + exposes the active site

• myosin head attatches to the actin filament, creating a cross-bridge

Step 3 of sliding filament theory

Myosin head Pivots (energy stroke)

• energy stored in the myosin head (from step 1) is used to pull the actin filaments toward the M-line

• ADP + P released

Step 4 of sliding filament theory

Detatchment

• as new ATP attaches to myosin head, cross-bridge detatches

Step 5 of sliding filament theory

Myosin Resets (return stroke)

• freed myosin head splits ATP into ADP + P

• released energy recocks myosin head to prepare for next stroke

What specific neruotransmitter is released during neuromuscular junction?

Acetylcholine (ACh)

neuromuscular junction

the location at whcih the end of the motor neuron meets the plasma membrane of the muscle fiber (the sarcolemma)

motor unit

the group of fibers that is collectively controlled by one neuron

action potential

the stimulus your brain sends for your muscles to move

What does the motor neuron not do?

directly touch the muscle fiber, creats a gap called the synaptic celft

What can an action potential not do?

Jump the gap from the motor neuron to the muscle fiber

What molecule is relesed to jump the synaptic cleft?

neurotransmitters

Voltage-gated channels

open in response to an action potential

Chemically-gated channels

open when a particular molecule attaches to them