Chapter 7 Flashcards
What are the functions of Muscles
1) Movement
2) Stability –> Prevent unwanted movement (posture and holding bones in place)
3) Control of body openings and passages –> Sphincter muscles around the eyelids (control admission of light to eyes) and regulating waste elimination
4) Heat Generation
5) Glycemic Control
How much of Body heat is generated by muscles at rest?
20-30%
What are the 3 types of muscular tissue?
Skeletal, Cardiac and Smooth
What is a skeletal muscle?
- A voluntary striated muscle that is usually attached to one or more bones. It is called voluntary because it is usually subject to conscious control and striated because it has alternating light and dark transverse bands that reflect the overlapping arrangement of the internal proteins that enable it to contract.
- Considered the most internally complex, tightly organized of all human cells.
What are skeletal muscle cells called?
Muscle Fibers –> Called this because of long slender shape
What are Myofibrils?
Thick Bundles of contractile proteins in the deeper part of the cell
What is packed between the Myofibrills?
- Mitochondria, Smooth ER, Carbohydrate Glycogen, Myoglobin (red oxygen-storing pigment)
What is the plasma membrane in Skeletal Muscle Fiber?
Sarcolemma
What are Transverse Tubules?
Tunnel-like infoldings that penetrate through the fiber and emerge on the other side.
What is the Function of the Transverse (T) Tubules?
Carry an electrical current from the surface of the cell to the interior when the cell is stimulated.
What is the Smooth ER of a muscle Fiber called?
Sarcoplasmic reticulum
- Forms web around myofibrils
- releases calcium into cytosol when muscle fiber is stimulated
- Has dilated sacs around T Tubules called “terminal cisternae”
What are the 2 types of Myofilaments?
Thick - Made of several hundred myosin proteins; has shaft-like tail and double globular head; heads directed outward around bundle
Thin - half as wide as the thick filaments and are composed mainly of 2 intertwined strands of actin like a bead necklace. Has 50 molecules of regulatory protein tropomyosin which has a small calcium-binding protein called troponin attached to it.
What is Titin?
protein which makes up the springy elastic filaments with hold thick and thin filaments in line.
What are A bands?
Regions in which thick and thin filaments overlap. Middle part composed of myosin only
What are I Bands?
Consists only of thin filaments
What is the Z-Disc?
- Bisects the I-Band
- Plaque of protein that provides anchorage for the thin filaments
What is the Sarcomere?
- Each segment of a myofibril from one Z-Disc to the next
- Function unit of the muscle fiber
A typical Sarcomere 3 cm long has about how many sarcromeres?
10,000
What is dystrophin?
Huge protein which links the thin filaments to the inner surface of the sarcolemma. It shortens cell when sarcomeres shorten.
What are Motor Neurons?
Nerve Cells that stimulate skeletal muscles. Their bodies are located in brainstem and spinal cord
What are Motor Nerve Fibers?
- Axons of Motor Neurons leading to muscles
- Branch to multiple fibers. Each fiber with only 1 nerve fiber.
What is a Motor Unit?
- One Motor and all muscle fibers supplied by it
- All contract at once
What is the difference between the very small and very large motor units?
The very large motor units such as ones in the thigh produce power, not fine motor control, whereas the very small motor units are not strong, but with fine motor control for such purposes as eye and hand movements
What are some advantages of having multiple motor units in a muscle?
- nervous system can generate variable muscle contractions by activating a variable number of motor units - more motor units for a stronger contraction.
- They can work in shifts to prevent fatigue
What is the Neuromuscluar Junction (NMJ)?
Where nerve meets muscle fiber; AKA the Motor end plate
What is the synapse?
When nerve fiber meets any cell type