Question

DQ. 1. Name and describe the four special functional abilities of muscle that are the basis for muscle response.

DQ2. (a) Describe the structure of as sarcomere and indicate the relationship of the sarcomere to myofilaments .

(b)explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and contracted sarcomere.

DQ3. What is the importance of acetylcholinesterase in muscle cell contraction?

Course Home * + ure.com/courses/27627/discussion_topics/175595 This is a graded discussion: 5 points possible due Mar 30 Chapter 9 Muscular System Suhall Butt DQ. 1. Name and describe the four special functional abilities of muscle that are the basis for muscle response. DQ2. (a) Describe the structure of as sarcomere and indicate the relationship of the sarcomere to myofilaments (b)explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and contracted sarcomere. DQ3. What is the importance of acetylcholinesterase in muscle cell contraction? Search antries or author Unread Subscribe Reply Danes Lebron

Answer 1

Ans.1:- Following are the four basic functionalities of muscle :

1. Contractility is the ability of muscle cells to forcefully shorten. For instance, in order to flex (decrease the angle of a joint) your elbow you need to contract (shorten) the biceps brachii and other elbow flexor muscles in the anterior arm. Notice that in order to extend your elbow, the posterior arm extensor muscles need to contract. Thus, muscles can only pull, never push.
2. Excitability is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone.
3. Extensibility is the ability of a muscle to be stretched. For instance, let's reconsider our elbow flexing motion we discussed earlier. In order to be able to flex the elbow, the elbow extensor muscles must extend in order to allow flexion to occur. Lack of extensibility is known as spasticity.
4. Elasticity is the ability to recoil or bounce back to the muscle's original length after being stretched.

Ans.2:- (a) Sarcomere, which is the basic unit of striated muscles, is a complex multicomponent biological system controllably transforming the chemical energy released upon ATP hydrolysis into mechanical work.Each sarcomere is composed of two main protein filaments—actin and myosin—which are the active structures responsible for muscular contraction.The thick myosin filament contains numerous heads, which when attached to the thinner actin filaments create actin-myosin cross bridges. In essence, a myosin head is similar to a cocked spring, which on binding with an actin filament flexes and produces a power stroke.Because sarcomeres are joined end to end throughout an entire muscle fiber, their simultaneous contraction shortens the entire muscle.

Relationship with Myofilaments: Each sarcomere contains two types of myofilaments: thick filaments, composed primarily of the contractile protein myosin, and thin filaments, composed primarily of the contractile protein actin.

(b). Following is the Diagram of a Relaxed/Contracted Sarcomere:

Actin filament Myosin filament Sacromere is relaxed Z line A band I band Myosin filament- Actin filament Sacromere scontracted > Cross-bridges H zone Z line A bond Iband

According to the sliding filament theory, the myosin (thick) filaments of muscle fibers slide past the actin (thin) filaments during muscle contraction, while the two groups of filaments remain at relatively constant length.active force is generated as actin filaments slide past the myosin filaments, resulting in contraction of an individual sarcomere.The A band contains thick filaments of myosin, which suggested that the myosin filaments remained central and constant in length while other regions of the sarcomere shortened. The investigators noted that the "I band," rich in thinner filaments made of actin, changed its length along with the sarcomere. These observations led them to propose the sliding filament theory, which states that the sliding of actin past myosin generates muscle tension. Because actin is tethered to structures located at the lateral ends of each sarcomere called z discs or "z bands," any shortening of the actin filament length would result in a shortening of the sarcomere and thus the muscle.

Ans.3:- Acetylcholine is a neurotransmitter that transmits signals to muscle cell contraction of the body. The acetylcholine is released in the synapses between the muscle cell and neuron. For every time, muscle contraction needs new acetylcholine molecules. It means that It needs old neurotransmitter is to be cleared from the synapse to allow new signals to the muscle for initiating new contractions. For that, acetylcholinesterase is a enzyme needed, because it it breaks the acetylcholine into acetic acid and choline, thus inactivates the old neurotransmitter and allowing neurotransmitters. If the acetylcholinesterase is functioning properly, the acetylcholine is not destroyed; it accumulates in the synapse and results in muscle paralysis. So that acetylcholinesterase is needed for muscle contraction