Exercise Physiology

Muscle fiber type and performance
The body majorly has two types of muscles, the slow-twitch and fast-twitch muscle fibers. Most people have, on estimation, 50% slow-twitch fibers and 50% fast-twitch ones. This however can significantly change depending on the type of training an athlete goes through. The slow-twitch muscles come into play for the endurance athletes hence they will develop more of this type over time with training. Fast-twitch muscle fibers are way better for activities that need short periods of intense activity such as among sprinters hence such athletes will develop more of this over time (Rivera H., 2018).
Breakdown of glycogen
Glycogen Phosphorylase catalyzes breakdown of glycogen into Glucose-1-Phosphate (G1P). The reaction that produces G1P from the glycogen in the body is referred to as phosphorolysis. Phosphorolysis reaction use phosphate to breakdown bigger molecules into smaller ones. The process of breaking down of the glycogen into glucose is referred to as glycogenolysis. This process takes place in the cells of the muscles and in the liver tissues as a response to neural and hormonal signals. Glycogenolysis plays a significant role in the flight-or-fight responses that are adrenaline induced as well as the regulation of glucose in the blood. Essentially the breakdown of glycogen to glucose will require four enzymes; one to degrade glycogen, two to remodel glycogen so that it remains a substrate for degradation, and one to convert the product of glycogen breakdown into a form suitable for further metabolism (National Center for Biotechnology Information, 2018).
How a nerve impulse is transmitted along its axon
Electrical impulses are transmitted from neuron to neuron through nerve impulse, referred to as an action potential, when the axon membrane rapidly depolarises and repolarises. The action potential taks place or is experienced when a neurone relays information down an axon. This process involves an explosion of electrical activity, where the nerve and muscle cells resting membrane potential changes, the axon gets polarized when the inside is negatively charged and the outside is positively charged. When a stimulus is applied, the Sodium ions channels in the axon membrane open, causing sodium ions to move into the axon and a rise of the p.d, due to the positive charge increase within the axon. If the stimulus reaches a threshold of -40mv, an action potential is generated, which is the nerve impulse. The depolarisation causes the inside of the axon to be positively charged and the outside to be negatively charged (Bazenilla F., 2002).
Advantages of fats over carbohydrates for fuel storage
Ordinarily, the body derives energy from carbohydrates during physical exercises. However, this source of energy to the body can only go for 90-180 minutes. The body then has to switch to fats as a source of energy. This alternative source of energy has several advantages one being that fats yield more than twice as much energy as compared to carbohydrates (4 Kcal for carbohydrates and 9 kcal for fats) and the human body has abundant supply of fats. The other advantage therefore of fats as a source of energy for the body is that it is available in abundance in that as the body carbohydrates storage is estimated at 1500 kcal of glycogen, there is 50,00 to 60,000 kcal of energy stored as fats. There is a huge potential source of energy (Hamilton A., 2018).
The structure of the heart and the functions of blood
The human heart is a muscular organ that bears four chambers whose shape and size is roughly as the clenched fist of a man. Two third of the mass of the heart is to the left of the midline. This organ is enclosed in a pericardial sac that is lined with the parietal layers of a serous membrane (Bendorf K., 2002). The primary function of the heart is to pump blood around the body so as to keep the other body organs efficiently functional. Blood has three major functions in the human body, to transport, to protect and to regulate. Blood helps in the transportation of gases (Oxygen and carbon dioxide) between the lungs and the rest of the body parts, it also transports nutrients from the digestive tract and the storage sites in the body to the rest of the body. Blood also transports waste products that need to be detoxified or excreted by the kidney and liver. It also transports hormones from the production glands to the target cells. Blood helps as well in transportation of heat to the skin in the process of temperature regulation. Blood helps ion protection of the white blood cells, the antibodies and the platelets. It also regulates the pH of the body and the water balance by transferring water to and from tissues (Virtual Medical Centre, 2018).

References
Bazenilla F., (2002). The Nerve Impulse. Retrieved February 25, 2017 from http://nerve.bsd.uchicago.edu/TheNerveImpulse05.pdf
Hamilton A., (2018). Fat as Fuel. February 25, 2017 from https://www.peakendurancesport.com/nutrition-for-endurance-athletes/supplements/fat-as-fuel/
National Center for Biotechnology Information, (2018). Glycogen Breakdown Requires the Interplay of Several Enzymes. February 25, 2017 from https://www.ncbi.nlm.nih.gov/books/NBK22467/
Rivera H., (2018). Muscle Fiber Types and How They Relate To Your Training Program. February 25, 2017 from http://www.hugorivera.net/muscle-fibers-trainin.html
Virtual Medical Centre, (2018). Blood Function and Composition. February 25, 2017 from https://www.myvmc.com/anatomy/blood-function-and-composition/