Muscular System Day 2

Muscle Development Hypertrophy – The growth and increase of the size of muscle cells Example? Bodybuilding

Atrophy – The decrease in the size of skeletal muscle cells. When a muscle atrophies, it necessarily becomes weaker Example? Inactivity, when a cast is put on a limb.

Myostatin Myostatin is a protein that limits muscle tissue growth by slowing down the development of muscle cells, i.e. higher concentrations of myostatin in the body may cause the individual to have less developed muscles What would myostatin inhibitors do?

Muscular Physiology Each muscle is made up of many Muscle Fibers Each muscle fibre is made up of Myofibrils Each myofibril is made up of a series of Sarcomeres The Sarcomere is made of 2 types of proteins, a thin filament (Actin) and a thick filament (Myosin)

Messages from the nervous system travel via nerves into the muscle telling it to contract. A motor nerve connects to a muscle and branches out into nerve endings. It is these endings which stimulate the muscle fibres. How Does a Muscle Know When to Contract?

Muscle Fatigue A muscle requires fuel and oxygen for energy. Muscles that are repeatedly contracted require a high amount oxygen and energy.

If a person continues to exercise without rest, then the muscles in the body run out of oxygen. As a result, there is a build up of lactic acid which causes a burning sensation in the muscles.

This causes the muscles to stop working properly. A consequence of working the muscle hard like this is that you may feel stiffness and soreness in the muscles for a time afterwards.

Why Some Athletes Use Drugs Athletes may have several reasons for using performance-enhancing drugs. An athlete may want to: Build mass and strength of muscles and/or bones Increase delivery of oxygen to exercising tissues Mask pain Stimulate the body Relax Reduce weight Hide use of other drugs

Anabolic steroids are mostly testosterone (male sex hormone) and its derivatives. Examples of anabolic steroids include: Testosterone Dihydrotestosterone Androstenedione (Andro) Dehydroepiandrosterone (DHEA) Clostebol Nandrolone These substances can be injected or taken as pills.

Anabolic steroids have a number of possible and well-known side effects, including: Jaundice and liver damage because these substances are normally broken down in the liver Mood swings, depression and aggression because they act on various centers of the brain

Males The excessive concentrations interfere with normal sexual function and cause: Baldness Infertility Breast development

Females The excessive concentrations cause male characteristics to develop and interfere with normal female functions. The drugs can: Stimulate hair growth on the face and body Suppress or interfere with menstrual cycle, possibly leading to infertility Thicken the vocal cords, which causes the voice to deepen, possibly permanently If pregnant, interfere with the developing fetus

Seatwork Read Pages Answer Questions 1,2,3 & 8 on Page 151. Review for your exam!