Central Nervous System

The fibers in both cells are striated, and the fibers are long and each muscle cell is fused to one another. This is why so many nuclei are included. Also, the fibers are almost threadlike, with dark and light colored striations.

The components of the nervous system involved in the skeletal muscle movement is the motor division. The motor impulse moves through the body by traveling through efferent fibers. A motor unit is a neuron and also that is where all the other muscle fibers are connected.

How is contraction ended? Ach is released and binds to receptors on the motor end plate, then an action potential is produced which releases Ca+. The Ca+ binds to troponin, then myosin binds to actin to form crossbridges. The myosin pulls the actin then releases from actin and ADP is bound to the myosin.

Actin and myosin filaments can be found in skeletal muscle and are the smallest units that form a sarcomere, which is the smallest contractile unit in muscle (Baechle, 2008). The Sliding Filament Theory states that the actin filaments slide inward on the myosin filaments, pulling on the boundaries of the sarcomere, causing it to shorten the muscle fiber, also known as a concentric muscular contraction (Baechle, 2008). The Sliding Filament Theory is composed of five steps: the “Resting Phase”, the “Excitation-Contraction Coupling Phase”, the “Contraction Phase”, the “Recharge Phase”, and the “Relaxation Phase” (Baechle, 2008). During the Resting Phase, the actin and myosin filaments are lined up with no cross-bridge binding of the two filaments. During the Excitation-Contraction Coupling Phase, Calcium is released from the sarcoplasmic reticulum and binds to troponin, causing a shift in tropomyosin where the binding cites are exposed (Baechle, 2008). When the binding cites are exposed, the myosin cross-bridge head attaches to actin. During the Contraction Phase, ATP bonds break, releasing energy that is used to allow the myosin head to flex, causing the actin filaments to move toward the M-bridge. During the Recharge Phase, there is a continuous repetition of the Excitation-Contraction Coupling Phase and the Contraction Phase in order to produce muscular

Skeletal Muscle Structure.The cells of skeletal muscles are long fiber-like structures. They contain many nuclei and are subdivided into smaller structures called myofibrils. Myofibrils are composed of 2 kinds of myofilaments. The thin filaments are made of 2 strands of the protein actin and one strand of a regulatory protein coiled together. The thick filaments are staggered arrays of myosin molecules.

As the message arrives at the end of the nerves, the message is transmitted to the muscles. Before the message is transmitted to the muscles it has to pass the space between the end of the nerve and the muscle, and that space is called neuromuscular junction. The message is transmitted from the brain to the end of the nerve and from the nerve to the neuromuscular junction, and when the message arrives the chemical called neurotransmitters are released.

Since nerves are critical pathways that carry information from the brain to the extremities they are likely to be distributed throughout the entire body. The two types of nerves, motor and sensory perform different functions. Motor nerves perform the function of carrying information from the brain to the organs, muscles, and heart. Whereas the sensory nerves do the work of sending information from the body back to the brain for processing, including pain, touch, taste, temperature and other sensations.

Activation of a motor neuron: The motor neuron now transmits nerve impulse to an effector.

The CNS contains the brain and spinal cord. Its main functions include: processing, integrating, and coordinating sensory information and motor instructions. The sensory data conducts information that is being processed from internal and external conditions the body is experiencing. Motor commands regulate and control peripheral organs (skeletal muscles). The brain functions under memory, emotions, learning, and intelligence. The PNS consist of the neural tissue found outside of the CNS. It functions in sending data to the CNS which motor commands are than carried out to the peripheral tissues/systems. Multiple nerve fibers send sensory data and motor commands in the PNS. The nerves that assist with transmitting data include the cranial nerves and spinal nerve. However, the PNS can be divided into afferent (to bring in) and efferent (to bring out) divisions of transferring data. The afferent division functions in bringing in sensory data to the CNS. Sensory structures are receptors that detect internal/external environmental change and adjusting accordingly. The efferent division functions in carrying out motor commands from the CNS to glands, muscles, and adipose tissue. The efferent division contains somatic

The binding Ach causes depolarization of the sarcolemma by opening ion channels and allowing Na+ ions into the muscle cell..

The peripheral nervous system (PNS) is connected directly to the central nervous system, and consists of neurons and nerves that send information back and forth the CNS. Furthermore, the peripheral nervous system can be divided into two sections, the sensory nervous system and the motor nervous system. The Sensory The sensory nervous system is in charge of transmitting data from a variety of internal organs or from external stimuli to the central nervous system using sensory nervous cells. On the other hand, the cells of the motor nervous system (motor neurons), take the impulse from the CNS to effectors, which include glands and muscles. In addition, the motor nervous system can be further divided into the somatic nervous system, controls voluntary actions of the skeletal muscle and external sensory organs, whilst the autonomic nervous system operates

To fully understand the events taking place and the data collected, a brief but thorough review of muscles on a physiological level is needed. Muscles are responsible for producing force and motion in the both the external world and within the body. Locomotion of the body and its organs is achieved via the contraction of three types of muscles: skeletal muscle, cardiac muscle, and smooth muscle. Our lab focuses on the effects of stimulation of skeletal muscle and more specifically, the relationship between a motor neuron and muscle contraction.

“Actin and Mysoin are responsible for the contraction of a muscle” ( McArdle, Katch and Katch 2001). Actin thin filaments and Myosin thick filaments are connected via cross bridges when sarcomeres contract, this is known as the sliding filament theory. When this occurs ATP is hydrolysed and energy is produced. Cytoskeletal proteins such as titin, nebulin and desmin also have roles in stabilizing the structure of the sarcomere by maintaining muscle integrity and transmitting force throughout the cell (Allen 2001) These proteins become damaged and lost following unaccustomed exercise in both human

With the myosin binding site exposed, the myosin head binds to the actin filament forming a cross bridge (cross bridge formation) (4). ADP is released and the myosin head cocks its neck region and pulls the actin filament towards the sarcomere’s M-Line. A shortening of the sarcomere (power stroke) is happening (ref sarcomere illustration): the distance between the Z-lines shortens, the I-band and the H-zone shortens whilst the A-band do not change length (2).

The central nervous system and the peripheral nervous system work together to collect information from within the body and from the environment outside it. The systems process all the collected information and send instructions to the body; to obtain an appropriate response. Once the data arrives, the brain will sort and file it before sending out any commands on what to do. The central system is the main command center of the body that contains the brain as well as the spinal cord. The peripheral nervous system contains a network of nerves that connect the rest of the body to the central nervous system.