11.1 HY The Muscular System Flashcards
What does the musculoskeletal system help with? (x6)
- Venous and Lymph drainage return
- Body movement
- Thermoregulation, shivering
- Digestive system (smooth muscle)
- Blood pressure regulation
- Cardiac blood flow (heart)
What are sarcomeres?
It is the arrangement of actin and myosin, and appeared striated or striped under the microscope.
They are also multinucleated
What’s the difference between red fibers and white fibers?
Red fibers (AKA Slow twitch)- high myoglobin content, derive energy aerobically. Also have a lot of mitochondria.
White Fibers (AKA Fast Twitch)- contain less myoglobin, these are muscles that contract quickly but loose energy and fatigue rapidly as well.
What is myoglobin?
It is an oxygen carrier that uses iron in a heme group to bind oxygen, and gives red color.
How is smooth muscle different than skeletal muscle?
- It is not well organized, so striations cannot be seen.
- Capable of mores sustained contractions, called tonus
- Can contract without nervous system input, known as myogenic activity
Same: both have actin and myosin.
How is cardiac muscle similar and different from smooth and skeletal muscle?
Nuclei: can have 1-2 nuclei
Contractions: can contract without nervous system input, called myogenic activity (like Smooth muscle)
Appearance: they appear striated, like skeletal muscle
How are cardiac muscles connected?
Connected by intercalated discs, which contain many gap junctions, allowing for the flow of ions directly through the cell.
What drives the heart to speed up and slow down?
Speed up: norepinephrine from sympathetic system
Slow down: vagus nerve, from parasympathetic system.
What drives the heart to speed up and slow down?
Speed up: norepinerphrine from sympathetic system
Slow down: vagus nerve, from parasympathetic system.
Draw out the table of skeletal, cardiac muscle, and smooth muscle. Also name:
1. Appearance
2. Innervation and voluntary vs involuntary control
3. Number of nuclei
What do the thick and thin filaments of the sarcomere contain?
Thick: myosin
Thin: actin, including troponin and tropomyosin
What does titin do?
It acts as a spring and anchors the actin and myosin filaments together.
What is the:
Z-line
M-line
I-band
H-zone
A-band
Z-line- defines the boundaries between each sarcomere
M-line- runs down the center of the sarcomere, through the middle of the myosin filaments
I-band- region containing exclusively thin filaments
H-zone- contains only thick filaments
A-band- contains the thick filaments in their entirety, including any overlap with thin filaments.
What happens during contraction to the:
Z-line
M-line
I-band
H-zone
A-band
This distance between H-Zone, I band, and Z-lines, and M-lines become smaller
A-band size remain constant.
What is the sarcoplasmic reticulum?
It is a modified endoplasmic reticulum that contains a high concentration of calcium ions.
What are myofibrils?
They are sarcomeres that are attached end-to-end to form myofibrils.
What is a muscle fiber?
These contain many myofibrils arranged in parallel
What’s the mnemonic for the parts of the sarcomere?
Z- Z is in the end of the alphabet, and end of sarcomere.
M-Middle of the Myosin filaments
I-I is a thin letter, (thin filaments only)
H- H is a tick letter (thick filaments only)
A-All of the thick filament, whether or not it is overlapping.
What does depolarization cause in the myocyte?
- Spreads down the sarcolemma to the t-tubules
- Travels down the T-tubules into the muscle tissues to the sarcoplasmic reticulum.
- In the sarcoplasmic reticulum, calcium is released.
- The calcium ions bind to a regulatory subunit in troponin, triggering a change in the confirmation of tropomyosin, to which troponin is bound
- This exposes the myosin binding site.
- Free globular heads of the myosin move toward and bind with exposed sites on actin.
- The newly formed actin-myosin cross bridges allow myosin to pull on actin, which draws the thin filaments towards the M-line, resulting in shortening of the sarcomere.
Walk me through the Actin-Myosin Cross-bridge Cycle.
- Myosin carrying hydrolyzed ATP (ADP and inorganic phosphate) is able to bind with the myosin-binding site.
- The release of the inorganic phosphate and ADP in rapid succession provides the energy for the power stroke, resulting in the sliding of the actin filament over the myosin filament.
3.** ATP binds to the myosin head**, releasing it from actin. - ATP is hydrolyzed to ADP and Pi, which re-cocks the myosin head so that is in position to initiate another cross-bridge cycle.
- This causes sequential shortening of the sarcomere
What is a simple twitch?
What does it consist of ?
What is the latent period?
It is a response of a single muscle fiber to a brief stimulus at or above the threshold.
It consists of a latent period, contraction period, and relaxation period.
The action potential spreads along the muscle and allows for calcium to be released from the sarcoplasmic reticulum
What is frequency summation & tetanus?
This happens when the muscle fiber is exposed to frequent and prolonged stimulation, not allowing for sufficient time to relax.
If it is unable to relax at all, it is called tetanus.
What is creatine phosphate?
It is a supplemental energy reserve.
It is created by transferring a phosphate group from ATP to creatine during times of rest.
