Muscle Physiology Case Histories - Case 4

A 17-year-old was working vigorously with a summer construction crew building a new greenhouse. In the intense heat of the day, she began to experience severe pain in the muscles of her limbs and carpopedal spasms. The cramping made her muscles feel like hard knots. The foreman of the crew instructed the young lady to drink some salt water and rest a while.

1. What is the cause of the cramping?

The cramp may have been caused by the fact the she was constantly contracting and relaxing her muscles harshly, causing them to spasm. Also, since it was hot, she probably lost a lot of salt and water, and became dehydrated with hyponatremia (low sodium levels. Dehydration causes electrolyte imbalances in the muscles. Electrolytes include potassium, calcium or magnesium. Electrolytes are minerals in your blood and other body fluids that carry an electric charge

2. Describe carpopedal spasms.

A carpopedal spasm is an involuntary and sudden muscle contraction of the ankles, wrists, hands, feet, thumbs, and great toes. It is often observed in hyperventilation, calcium deprivation, and tetany. The muscle twitches and convulses, and often times may stay in a particular possition for a prolonged amount of time. Carpopedal spasm may be an early sign of hypocalcaemia.

3. Why is the ingestion of salt and water beneficial?

Ingestion of salt and water is beneficial because salt is an important mineral/ electrolyte. Salt is made up of sodium chloride, and helps in regulating body functions, such as digestion and absorption. Salt also helps to remove toxins from the body. Some salts may also contain iodine, which is necessary for normal cell metabolism and thyroid function.

Muscle Physiology Case Histories - Case 5

Prior to intubation for a surgical procedure, the anesthesiologist administered a single dose of the neuromuscular blocking agent, succinylcholine, to a 23-year-old female to provide muscular relaxation during surgery and to facilitate the insertion of the endotracheal tube. Following this, the inhalation anesthetic was administered and the surgical procedure completed.

1. Beginning with depolarization at the neuromuscular junction, describe the normal sequence of events which lead to muscle contraction.

This is how the neuromuscular junction is set up: the sarcolemma of the muscle fiber has many folds and crevices. Within these folds lay the ends of the motor neurons. On the opposite ends, there is an abundance of mitochondria and synaptic vesicles that store neurotransmitters. The space between the neuron and the motor end plate of the muscle fiber is called the synaptic cleft. As a nerve stimulant journeys from the brain to spinal cord, and reaches the ends and releases neurotransmitters, a muscle contracts.

2. What prevents acetylcholine (ACh) from accumulating in the neuromuscular junction and causing a sustained contraction in a normal individual?

Acetylcholine that stimulates the muscle fiber is rapidly decomposed by acetycholinesterase. A nerve impulse can no longer stimulate the muscle fiber because of the presence of the acetylcholinesterase. Once the acetylcholine is completely decomposed, the muscle fiber stimulus stops. The calcium levels of the sarcoplasm are lowered due to the fact that the calcium ions are transported back into the sarcoplasmic reticulum. Actin and myosin filament links break and the muscle relaxes.
Text Book 172-173

3. Succinylcholine acts as a depolarizing agent that prevents repolarization of the nerve. Therefore, no further ACh is released until the drug is cleared. Name another site within the neuromuscular junction that might be affected to prevent muscle contraction. (Hint: curare acts by this mechanism.)

Another site within the neurotransmitter junction that may be affected is the action of the neurotransmitter acetylcholine. It cannot be released and the entire process would be diminished.

Muscle Physiology Case Histories - Case 10

Parents of a 3-year-old noticed that their daughter was walking "on her toes," had a waddling gait, fell frequently and had difficulty getting up again, and was not able to run because of the difficulty in raising her knees. At age five, there was progressive muscular weakness and muscle wasting. Weakness of the trunk muscles led to increased lordosis and a protuberant abdomen. At age nine, she was confined to a wheelchair. Contractures appeared, first in the feet, as the gastrocnemius muscles tightened.

1. This hereditary X-linked recessive disease characterized by progressive muscular weakness is...

Duchene muscular dystrophy.

2. What does dystrophy mean? Why is this term used to describe this case?

Dystrophy means A degenerative disorder in which the muscle weakens caused by inadequate or defective nutrition. In this case, the child’s muscles are in fact becoming weaker and weaker.

3. What muscles would be involved in walking "on the toes"? Which muscles are "weakening"?

Muscles involved with walking on the toes include the fibularis longus, tibialis anterior, extensor digitorum longus, gastrocnemius, soleus, and especially the calcaneal tendon, soleus, and fibularis longus.
Text Book 184 -185

4. Name the trunk muscles that weaken in certain cases of lordosis and abdominal protuberance.

Because lordosis and abdominal protuberance is an increased curvature of the spine with a bulge or projection of the abdomen, the weakened muscles would be theTrapezius, infraspinous, rhomboideus, latissimus dorsi, external oblique, external oblique, and the rectus abdominis.
Text Book 184- 185

I. Scenario a
1) Describe bone physiology and the bone remodeling process. Be sure to emphasize the two types of bone tissue and the roles of osteoblasts and osteoclasts.
Bones are dense and provide support and structure to the body. Bone will be one of two types; compact which is dense and tough, or spongy which is not as dense and more flexible.Bones contain osteocytes, osteoblasts, and osteoclasts. Osteocytes exist in the lacuna. Osteocytes primary goal is bone deposition and resorption. They are secreted by osteobalsts. Osteocytes send messages to other osteocytes when any kind of damage or stress has come to the bone through physical activity. When continuous repairing occurs, the bone will become stronger over time. But on the other hand, if there is no repairing of the bone, they can become weak.
Osteoblasts primary goals are synthesis and mineralization
and are present when bones are formed and during remodeling.
The bone remodeling process involves something called Basic Multicellular Unit (BMU). The BMU are cells the travel around bone structures and find stressed or dameged areas of bone. They then dissolve onto that area an fill it in with now new bone.

2) Explain the relationship between calcium and bone.
Calcium is the most apparent mineral in the body and helps make bones strong and dense. Since calcium is not produced in the body, the body has to pull it from the bones where it is stored. Calcium is then released into the blood stream. When calcium levels are low, bones will give off less calcium in order to maintain even the any kind of amount.

3) Explain how the body controls calcium levels in the bones and blood. Be sure to describe the roles of parathyroid hormone (PTH) and calcitonin in detail.
The body controls calcium levels in the bones and blood through negative feedback. When calcium levels in the blood stream are too low, parathyroid hormone (PTH)
release more and more parathyroid hormone into the blood. This stimulates osteocytes which cause bone to breakdown. This releases calcium into the blood stream. The body also has a way of reacting to too much calcium in the blood stream. When there is too much calcium, calcitonin is released. Calcitonin cease osteocytes from breaking bone down. This keeps more calcium from being released into the blood stream.

4) Explain specifically how osteoporosis affects the bone matrix and the normal bone remodeling cycle.
Osteoporosis is caused when new bone is not being readily produced or the body is reabsorbing too much old bone. When bone becomes damaged, bone remodeling does not take place and it continues to breakdown. Since bone is a network of different cells, it composition depends greatly on all the parts functioning properly, and the breakdown may cause stress and fructures.

5) Discuss what scientists know about the genetics behind osteoporosis.
Scientists know that it is characterized by decrease in bone density and an increase in bone fragility. They know that in people over the age of 60, 60% of women and 30% of men will be diagnosed with osteoporosis. Women are more likely to get it because of their small skeletal frames. 1 in 5 women in America will be diagnosed with osteoporosis. This is largely due to menopause and the sudden change in hormones. Caucasion have the greatest risk, a higher than average risk.

6) List as many risk factors for this disease as you can, both controllable and uncontrollable.

Controllable Risk Factors
  • Body weight
  • Smoking
  • Too little calcium in diet
  • Drink more than 3 alcoholic beverages a day
  • Take certain kinds of medications
  • Little to no exercise
  • Eating disorders
  • Drinking too much soda

Uncontrollable Risk Factors
  • Sex
  • Age
  • Race
  • Family History
  • Lifetime exposure to estrogen
  • Frame Size
  • Thyroid Hormone
  • Depression

7) What are the symptoms or telltale signs of osteoporosis?
Symptoms of osteoporosis can arise when it may be too late. The symptoms are bone pain or tenderness, fractures with little or no trauma, loss of height over time, low back pain, neck pain, stooped posture, and muscle pain.

II. Scenario B

1) Explain why calcium is vital to bone health.
Calcium is vital to bone health because calcium trigers bone remodeling. The amount of parathyroid hormone (PTH) and calcitonin depends on how much calcium is released into the blood stream.

2) What foods are good sources of calcium?
Foods that are good sources of calcium include:
  • Milk
  • Yogurt
  • Cheese
  • Brocili
  • Watercress
  • Curly Kale
  • Okra
  • Red Kidney Beans
  • Chick Peas
  • Green Beans
  • Baked Beans
  • Nuts
  • Fish
  • Breads and Grains
  • Approcots
  • Figs
  • Oranges
  • Currants
  • Tofu
  • Say

3) Discuss the importance of Vitamin D to calcium absorption.
Vitamin D helps calcium from the diet to absorb into the intestines. Vitamin D creates the hormone calcitriol, which helps in absorption which prevents the body from having to take calcium out of the bones.

4) Discuss calcium supplementation and the recommended daily dosages.
Calcium supplements are taken py people who do not believe they are getting enough calcium in their daily diet, or have whose bodies have difficulty absorbing calcium. The regular recommended daily dosages are 800 mg for children, 1,000 mg for men, premenopausal women, and postmenopausal women also taking estrogen, 1,200 mg for teenagers and young adults ages 11 to 24, 1,500 mg for post menopausal women not taking estrogen, 1,200mg to 1500 mg for pregnant and nursing mothers. Too much calcium would be anything over 2,000 mg.

5) Discuss the effects of Discuss the effects of sodium, caffeine, and alcohol on calcium levels in the body. in the body.
Caffeine's effect on calcium is evident, but small. Caffeine can cause an increase in calcium being released into the blood stream, but decrease the amount that is able to be absorbed. Sodium increases the amount of calcium being released into the blood stream and the amount being absorbed. Alcohol reduces both the ability for calcium to be absorbed and the production of vitamin D.

6) Explain what peak bone mass is and its relationship to osteoporosis.
Peak bone mass is the amount of bony tissue present at the end of the skeletal maturation. This is as much bone as you will have for the rest of your life. If you are diagnosed with osteoporosis, your bone mass can only decrease, unless treated, but never exceed the amount at your peak bone mass.

7) Describe the types of exercise that help prevent osteoporosis. Why?
Any type of weight bearing exercise, or exercise that involves stretching, can help prevent osteoporosis. These types of exercise promote constant bone remodeling. Exercises that do this include:
  • Running and jogging
  • Gymnastics
  • Aerobics class -- step, dance and pump aerobics
  • Weight lifting -- dumbbells, barbells, machines, body weight exercises
  • Team sports involving running and throwing -- basketball, football, baseball, softball, volleyball
  • Individual sports involving running -- racket sports
  • Walking (but less effective than running or jogging)

8) What are steroids? What are they used for?
Steroids are any of a large group of fat-soluble organic compounds, as the sterols, bile acids, and sex hormones, most of which have specific physiological action. Steroids are used to gain muscle while exercising. They increase protien production, which in turn increase muscle tissue.

9) Explain how long-term use of steroids may increase risk for osteoporosis.
Steroids make it difficult for calcium to be absorbed into the blood stream. The body thinks that it is being depleted of calcium, and starts to get it from the bone supply. Steroids also trigger osteoclast production and activity. This increases bone breakdown, but steroids also restrict osteoblast activity, and postpones bone remodeling.

III. Scenario C



4) Explain how smoking affects estrogen levels. How does this in turn affect calcium levels?
Smoking lowers the level of estrogen in a woman's body. Lowered estrogen means that menopause will be reached sooner. During Menopause, estrogen is not produced. Because of this, osteoclasts increase bone absorption and limit calcium absorption needed for osteoblasts to build bone. So calcium can no longer be absorbed into the bone and aid in bone remodeling.

What is HRT? Who is it intended for?
HRT stands for hormone replacement therapy and is the administration of estrogen and progestin to women to relieve the symptoms of menopause, prevent osteoporosis, and reduce the risk of heart disease.

Based on medical studies, what are the pros and cons of HRT?

Pros of HRT
  • HRT and ERT reduce the risk of osteoporosis
  • HRT and ERT relieve hot flashes
  • HRT and ERT reduce the risk of heart disease
  • HRT and ERT may improve mood and psychological well-being.

Cons of HRT
  • ERT increases the risk of cancer of the uterus
  • HRT can have unpleasant side effects, such as bloating or irritability.
  • HRT and ERT may increase risk of breast cancer
  • In women with blood clots, HRT and ERT may be dangerous.

III. Scenario C