Chapter Seven

Question 1

Structure, Function, & Location: Skeletal Muscle

Answer 1

Covers the skeleton, giving the body its shape. Attached to the skeleton by strong, springy tendons or are directly connected to rough patches of bone. Under voluntary control. Almost all body movements caused by skeletal muscle contraction. Generates heat as a by-product of muscle activity. Heat is vital for maintaining the set point of body temperature

Question 2

Describe the structure, function and location of the Cardiac muscle

Answer 2

This type of muscle only exists in the heart. Cardiac muscle never gets tired. It works automatically and constantly without pausing to rest. Cardiac muscle contracts to squeeze blood out of the heart, and relaxes to fill the heart with blood.

Question 3

Describe the structure, function and location of the Smooth muscle

Answer 3

Found in the walls of hollow organs like the intestines and stomach. Smooth muscles are under involuntary control. Muscular walls of the intestines contract to push food through your body. Muscles in the bladder wall contract to expel urine from your body. Smooth muscles in a woman’s uterus help to push babies out of the body during childbirth

Question 4

Identify in a drawing and describe the location of the connective tissue sheaths within a skeletal muscle like the biceps brachia:

Answer 4

SEE IMAGE

i. endomysium
ii. perimysium
iii. epimysium

Question 5

Identify the structures of a skeletal muscle fiber on a model:

Answer 5

Identify sarcolemma, sarcoplasmic reticulum, myofibril, tropomyosin, myosin, troponin, actin, t-tubles

Question 6

Describe the arrangement of actin and myosin within a muscle cell and describe how they are organized to form sarcomeres

Answer 6

Actin and myosin are two important proteins in forming sarcomeres. The enzyme myosin
has a long, fibrous tail and a globular head, which binds to actin through ATP, which is the source of energy for muscle movement. Myosin then releases actin, as ATP goes to ADP plus a phosphate group. This process cocks the myosin protein to high energy shape. At this point, the phosphate group releases from myosin, causing the myosin to push on the actin. This process plays itself out over and over, intertwining within the sarcomeres. When the sarcomeres receive action potential from neurons, the myosin crawl towards the actin and the tension from the process creates a muscle contraction
NOTE: sarco=flesh, myo=muscle
Context: A muscle cell from biceps may contain 100,000 sarcomeres

Question 7

Explain the microscopic evidence that was used to support the sliding filament theory of muscle contraction

Answer 7

Sir Andrew Huxley in 1954 begun to develop the sliding filament theory of muscle contractions, where thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere. He synthesized his findings, and the work of colleagues into a detailed description of muscle structure and how muscle contraction occurs and generates force that he published in 1957. In 1963, Huxley won the 1963 Nobel Prize in Physiology or Medicine

Question 8

Briefly describe the role of the nervous system in muscle contraction

Answer 8

Muscle contraction initiated or “communicated” from somewhere in the central nervous
system, either as voluntary activity from the brain or as reflex activity from the spinal cord.

Question 9

Explain the details of muscle contraction including details of the cross bridge cycle and why and where calcium and ATP are used

Answer 9

Calcium ions flow into the cytoplasm, which is where the actin and myosin filaments are. Calcium ions bind to troponin-tropomyosin molecules located in the grooves of the actin filaments. Normally, the rod-like tropomyosin molecule covers the sites on actin where myosin can form cross bridges. Upon binding calcium ions, troponin changes shape and slides tropomyosin out of the groove, exposing the actin-myosin binding sites. Myosin interacts with actin by cycling cross bridges. The muscle thereby creates force, and shortens. After the action potential has passed, the calcium gates close, and calcium pumps located on the sarcoplasmic reticulum remove calcium from the cytoplasm. As the calcium gets pumped back into the sarcoplasmic reticulum, calcium ions come off the troponin

Question 10

Explain how the following chemicals and diseases interfere with neuromuscular communication: Botulinum Toxin

Answer 10

Botox blocks neuromuscular transmission by impairing the calcium influx that normally accompanies nerve depolarization.

Question 11

Explain how the following chemicals and diseases interfere with neuromuscular communication: Organophosphate Pesticides

Answer 11

Excess acetylcholine (ACh) present at different nerves and receptors in the body
because acetylcholinesterase (how’s that for a fifty cent word) is blocked causes
organophosphate poisoning. Accumulation of ACh at motor nerves causes
overstimulation of nicotinic expression at the neuromuscular junction.

Question 12

Explain how the following chemicals and diseases interfere with neuromuscular communication: Lou Gherig’s disease

Answer 12

Causes damage to the nerve cells controlling voluntary muscle movement (motor neurons). Over time, individuals with ALS will lose movement in muscles throughout the body, including the muscles used in breathing.

Question 13

Explain how these diseases interfere with muscle structure and function: Myotubular Dystrophy

Answer 13

Myotubular Dystrophy is a rare disease that primarily affects infant boys. Myotubular dystrophy causes muscle weakness, problems breathing, and problems swallowing when infants are feeding.

Question 14

Explain how these diseases interfere with muscle structure and function: Duchenne muscular dystrophy

Answer 14

Rapidly progressive form of muscular dystrophy that occurs primarily in boys. It is
caused by an alteration (mutation) in a gene, called the DMD gene that can be inherited in families in an X-linked recessive fashion. Induviduals with DMD have progressive loss of muscle function and weakness, which begins in the lower limbs.!

Question 15

Explain how these diseases interfere with muscle structure and function: Myostatin and Sports doping

Answer 15

Scientists have developed antibodies to myostatin and other molecules that can boost
lean muscle mass in animals by as much as 60 percent. It’s not yet clear how well myostatin inhibitors will work in humans. Clinical studies of two myostatin inhibitors are now under way for muscular dystrophy and other muscle-wasting diseases. They also are potentially the next wave in performance enhancing drugs as a result of their ability to grow muscle at an alarming rate.

Question 16

How are muscles able to generate a small amount of force to pick up something light like a pen and a few seconds later generate a large amount of force to pick up something heavy like a book

Answer 16

Muscle contractions are controlled by your nervous system and motor unit recruitment occurs in an orderly fashion as more force is required. Force increases when you lift a light weight faster, or when you lift a heavier weight. Light weights recruit your smallest/ slowest motor units, and then additional larger/faster motor units are recruited as force escalates.

Question 17

Difference between: Isometric contraction and an isotonic contraction

Answer 17

• Myosin heads pulling on actin generate force to move a load. If the load is greater than the muscle force, contraction is isometric. Myosin heads pulling on actin do not generate a force great enough to lift no, so there is no length change.!
• If the load is less than muscle force, contraction is isotonic. Myosin heads pulling on the actin generate a force greater than load, muscle shorten and moves the load. Isotonic contraction is force generation with length change.!

Question 18

Difference between: Concentric and eccentric contraction

Answer 18

• When a muscle is activated and required to lift a load which is less than the maximum
tetanic tension it can generate, the muscle begins to shorten. Contractions that permit the muscle to shorten are referred to as concentric contractions. An example of a concentric contraction in the raising of a weight during a bicep curl.!
• During normal activity, muscles are often active while they are lengthening. Classic examples of this are walking, when the quadriceps (knee extensors) are active just after heel strike while the knee flexes, or setting an object down gently (the arm flexors must be active to control the fall of the object).

Question 19

Difference between: Fast and Slow muscle

Answer 19

Slow twitch muscle fibres are good for endurance activities like long distance running
or cycling. They can work for a long time without getting tired. Fast twitch muscles are good for rapid movements like jumping to catch a ball or sprinting for the bus. They contract quickly, but get tired fast, as they consume lots of energy.

Question 20

Difference between: Anaerobic fermentation and aerobic respiration in terms of the amount of ATP they produce and where the chemical reactions occur in the cell

Answer 20

Cellular respiration can be aerobic (meaning “with oxygen”) or anaerobic (“without
oxygen”). Which route the cells take to create the ATP depends solely on whether or not there is enough oxygen present to undergo aerobic respiration. If there is not enough oxygen present for aerobic respiration, then the organism will resort to using anaerobic respiration. Like aerobic respiration, anaerobic respiration happens in the mitochondria.

Question 21

Difference between: Physiological and psychological fatigue

Answer 21

The difference between physical and psychological fatigue is that physical fatigue is
the extreme tiredness of the whole body and psychological fatigue is the extreme tiredness CAUSED by your mental state. In other words, one is physically and the other is mentally.

Question 22

Identify 2 muscle properties that can be changed with training.

Answer 22

Resistance training can cause muscle hypertrophy, or bigger cells and increased
mitochondria, number of myofilaments, and glycogen stores.

Question 23

Learn to identify the general location of muscles in the list below on 3-D models, real bodies and in images. Most of these are superficial and prime movers.

Answer 23

SEE IMAGE