Chapter 9: Review Questions
What are the sources of energy used to regenerate ATP?
-Direct phosphorylation of ADP by creatine phosphate (CP) -Anaerobic pathway (glycolysis) -Aerobic respiration (during rest and light exercise)
Explain how the filaments of a myofibril interact during muscle contraction
-calcium moves tropomyosin out of the way of the actin filament -mysosin head grabs onto actin and pulls it toward the center of the sarcomere until the actin and myosin filaments are overlapped. -The H zone becomes smaller due to the increasing overlap of actin and myosin filaments, and the muscle shortens/contracts -ATP allows myosin to let go -ATP is then broken down into ADP and phosphate. -Energy is released and stored in the myosin head to use for later movement. -The myosin heads now return to their upright relaxed position. -If calcium is present, the process is repeated.
Describe the two major types of smooth muscle
1. multiunit- separated fibers; make up eyes and walls of blood vessels 2. visceral- organized spindle shape, sheets; can stimulate and have rhythmic contractions; found in the intestines
How is smooth muscle contraction similar to skeletal muscle contraction?
Both the smooth muscles and skeletal muscles have the same contractile elements, i.e. the actin and myosin. In both the muscles, the contraction is initiated by an impulse, both needs calcium and ATP for the muscle contraction.
How is cardiac muscle similar to skeletal muscle?
Cardiac muscle is composed of striated cells joined end to end, forming fibers. These fibers interconnect in branching, three-dimensional networks. Each cell contains many filaments of actin and myosin, similar to those in skeletal muscle.
Describe how connective tissue is associated with a skeletal muscle
Each muscle is surrounded by connective tissue called the epimysium. Each fasicle is surrounded by connective tissue called the perimysium. Each muscle fiber is surrounded by connective tissue called the endomysium
Explain the physical relationship between the sarcoplasmic reticulum and the transverse tubules
Each transverse tubule lies between enlarged portions of the sarcoplasmic reticulum, called cisternae Transverse tubules conduct impulses from the sarcolemma (on the surface of the cell) down into the sarcoplasmic reticulum The sarcoplasmic reticulum responds to the t-tubules sending the action potential, to change the permeability of the membrane
Describe the general structure of a skeletal muscle fiber
Muscle fibers are wrapped in sarcolemmas endomysium in between each muscle fiber made up of myofribrils surrounded by sarcoplasmic reticulum has a nuclues muscle fiber = muscle cell
Explain how a motor neuron action potential can trigger a skeletal muscle fiber contraction
The motor end plate (the neuromuscular junction) is the junction of the motor neurons axon and the muscle fibers it stimulates. When an impulse reaches the muscle fibers of a motor unit, it stimulates a reaction in each sarcomere between the actin and myosin filaments to cause the muscle to contract skeletal muscle fibers contract only when stimulated by a motor neuron
Define muscle tone
The partial contraction of resting muscles some motor units are always active
Explain why skeletal muscle fibers appear striated
The striated appearance of skeletal muscle tissue is a result of the organization of the myofilaments actin and myosin that are present along the length of myofibrils produces alternating light and dark striations, or bands, of a skeletal muscle fiber.
What special characteristics of visceral smooth muscle make peristalsis possible?
Transmission of impulses and repeated contractions make peristalsis possible
List four proteins associated with myofibrils and explain their structural and functional relationships
actin, nebulin, myosin, titin actin makes up thin filaments, coiled with nebulin filaments. myosin makes up thick filaments, held in place by titin filaments. Actin filaments form "ladder" that myosin filaments "climb to generate motion
What is the relationship between cellular respiration and heat production?
all active cells generate heat as a by-product of cellular respiration
Distinguish between fast-twitch and slow-twitch muscle fibers
fast-twitch- fatiques faster but are used in powerful bursts of movement. slow-twitch- don't fatique as quickly used for long-endurance
Explain the differences between isometric and isotonic contractions
isotonic- tension developed by the muscle remains almost constant while the muscle changes length isometric- the tension generated is not enough to exceed the resistance of the object to be moved, and the muscle does not change its length
How does cardiac muscle differ from skeletal muscle?
skeletal are striated voluntary muscles around the body cardiac are involuntary muscles found along the heart wall
How do the contraction mechanisms of smooth and skeletal muscles differ?
skeletal is voluntary smooth is involuntary
What is the function of an antagonist?
•Antagonist—muscle that opposes or reverses a prime mover (agonist)
Define agonist
•Prime mover—muscle with the major responsibility for a certain movement
What are the sources of oxygen required for the aerobic reactions of cellular respiration?
•Produces 95% of ATP during rest and light to moderate exercise Requires oxygen and Energy source: glucose; pyruvic acid; free fatty acids from adipose tissue; amino acids from protein catabolism
Describe a neuromuscular junction
•Situated midway along the length of a muscle fiber The synapse where a motor neuron axon and a muscle fiber meet It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. includes the end of a motor neuron and the motor end plate of a muscle fiber
What is the function of a synergist?
•muscle that aids a prime mover in a movement and helps prevent rotation
