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 weakerExample? 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 FatigueA 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:

• 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 137-151

Answer Questions 1,2,3 & 8 on Page 151.

Review for your exam!