15: Muscular System - Biology

15: Muscular System - Biology

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This chapter describes the structure and functions of the muscular system. It compares and contrasts the three major types of muscle tissue and explains in detail how muscles contract according to the sliding filament theory. The chapter also relates physical exercise to fitness and health and describes several musculoskeletal and neuromuscular disorders.

  • 15.1: Case Study - Muscles and Movement
    This dog is expressing his interest in something — perhaps a piece of food — by using the neck muscles to tilt its head in an adorable fashion.
  • 15.2: Introduction to the Muscular System
    Does the word muscle make you think of the well-developed muscles of a weightlifter, like the woman in this photo? Her name is Natalia Zabolotnaya, and she’s a Russian Olympian. The muscles that are used to lift weights are easy to feel and see, but they aren’t the only muscles in the human body.
  • 15.3: Types of Muscle Tissue
    He turns his gray-blue eyes in your direction—a very small movement, considering the conspicuously large and strong external eye muscles that control eyeball movements. These muscles have been called the strongest muscles in the human body relative to the work they do. However, the external eye muscles actually do a surprising amount of work.
  • 15.4: Muscle Contraction
    It’s obvious that a sport like arm wrestling depends on muscle contractions. Arm wrestlers must contract muscles in their hands and arms, and keep them contracted in order to resist the opposing force exerted by their opponent. The wrestler whose muscles can contract with greater force wins the match.
  • 15.5: Physical Exercise
    Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. We generally think of physical exercise as activities that are undertaken for the main purpose of improving physical fitness and health. However, physical activities that are undertaken for other purposes may also count as physical exercise. Scrubbing a floor, raking a lawn, or playing active games with young children or a dog are all activities that can have fitness and health b
  • 15.6: Disorders of the Muscular System
    Musculoskeletal disorders are injuries that occur in muscles or associated tissues (such as tendons) because of biomechanical stresses. They may be caused by sudden exertion, over-exertion, repetitive motions, or long periods maintaining awkward positions. Musculoskeletal disorders are often work- or sports-related, and generally just one or a few muscles are affected. They can often be treated successfully, and full recovery can be very likely.
  • 15.7: Case Study Conclusion: Needing to Relax and Chapter Summary
    As you learned in the beginning of this chapter, botulinum toxin — one form of which is sold under the brand name Botox — does much more than smooth out wrinkles. It can be used to treat a number of disorders involving excessive muscle contraction, including cervical dystonia. You also learned that cervical dystonia, which Edward suffers from, causes abnormal, involuntary muscle contractions of the neck. This results in jerky movements of the head and neck, and/or a sustained abnormal tilt to th


Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter—a chemical message released by nerve cells to send signals to other cells, such as neurons, muscle cells and gland cells. [1] Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Substances that increase or decrease the overall activity of the cholinergic system are called cholinergics and anticholinergics, respectively.

Acetylcholine is the neurotransmitter used at the neuromuscular junction—in other words, it is the chemical that motor neurons of the nervous system release in order to activate muscles. This property means that drugs that affect cholinergic systems can have very dangerous effects ranging from paralysis to convulsions. Acetylcholine is also a neurotransmitter in the autonomic nervous system, both as an internal transmitter for the sympathetic nervous system and as the final product released by the parasympathetic nervous system. [1] Acetylcholine is the primary neurotransmitter of the parasympathetic nervous system. [2]

In the brain, acetylcholine functions as a neurotransmitter and as a neuromodulator. The brain contains a number of cholinergic areas, each with distinct functions such as playing an important role in arousal, attention, memory and motivation. [3]

Acetylcholine has also been traced in cells of non-neural origins and microbes. Recently, enzymes related to its synthesis, degradation and cellular uptake have been traced back to early origins of unicellular eukaryotes. [4] The protist pathogen Acanthamoeba spp. has shown the presence of ACh, which provides growth and proliferative signals via a membrane located M1-muscarinic receptor homolog. [5]

Partly because of its muscle-activating function, but also because of its functions in the autonomic nervous system and brain, many important drugs exert their effects by altering cholinergic transmission. Numerous venoms and toxins produced by plants, animals, and bacteria, as well as chemical nerve agents such as Sarin, cause harm by inactivating or hyperactivating muscles through their influences on the neuromuscular junction. Drugs that act on muscarinic acetylcholine receptors, such as atropine, can be poisonous in large quantities, but in smaller doses they are commonly used to treat certain heart conditions and eye problems. Scopolamine, which acts mainly on muscarinic receptors in the brain, can cause delirium hallucinations, and amnesia. The addictive qualities of nicotine are derived from its effects on nicotinic acetylcholine receptors in the brain.

Bioengineering a Miniaturized In Vitro 3D Myotube Contraction Monitoring Chip For Modelization of Muscular Dystrophies

Quantification of skeletal muscle functional strength is essential to assess the outcomes of therapeutic procedures for muscular disorders. Several muscle three-dimensional “Organ-on-chip” models have been developed to measure the generated force. Yet, these technologies require a substantial amount of biological material, which is problematic in the context of limited patient sample.

Here we developed a miniaturized 3D myotube culture chip with contraction monitoring capacity. Combination of light-induced molecular adsorption technology and optimized micropatterned substrate design enabled to obtain high culture yields in tightly controlled physical and chemical microenvironments. Spontaneous twitch contractions in 3D myotubes derived from primary human myoblasts were observed, the generated force was measured and the contraction pattern characterized. In addition, the impact of three-dimensional culture on nuclear morphology was analyzed, confirming the similarity in organization between the obtained 3D myotubes and in vivo myofibers. Our system enabled to model LMNA-related Congenital Muscular Dystrophy (L-CMD) with successful development of mutant 3D myotubes displaying contractile dysfunction.

We anticipate that this technology shall be used to study contraction characteristics and evaluate how specific diseases affect muscle organization and force generation. Our downsized model system might allow to substantially improve drug screening capability for therapeutic oriented research.

Endocrine System

The endocrine system is made up of a group of glands that produce the body's long-distance messengers, or hormones. Hormones are chemicals that control body functions, such as metabolism, growth, and sexual development. The glands , which include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, thymus gland, pineal body, pancreas, ovaries, and testes, release hormones directly into the bloodstream, which transports the hormones to organs and tissues throughout the body.


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Reduced cortico-muscular beta coupling in Parkinson’s disease predicts motor impairment

Long-range communication through the motor system is thought to be facilitated by phase coupling between neural activity in the 15-30 Hz beta range. During periods of sustained muscle contraction (grip), such coupling is manifest between motor cortex and the contralateral forearm muscles – measured as the cortico-muscular coherence (CMC). We examined alterations in CMC in individuals with Parkinson’s disease (PD), while equating grip strength between individuals with PD (off their medication) and healthy control participants. We show a marked reduction in beta CMC in the PD group, even though the grip strength was comparable between the two groups. Moreover, the reduced CMC was related to motor symptoms, so that individuals with lower CMC also displayed worse motor symptoms. These findings highlight the CMC as a simple, effective, and clinically relevant neural marker of PD pathology, with the potential to aid monitoring of disease progression and the efficacy of novel treatments for PD.

15: Muscular System - Biology

An organ is a group of tissues in a living organism that has a specific form and function.

  • Nervous system - The nervous system is responsible for carrying messages from the brain to various parts of the body. It includes the brain, spinal cord, and nerves.
  • Respiratory system - The respiratory system is responsible for breathing. It transfers oxygen into the blood stream and removes carbon dioxide. It includes the lungs, larynx, and airways.
  • Cardiovascular or circulatory system - The cardiovascular system carries blood throughout the body to help bring nutrients to various other organs. It includes the heart, blood, and blood vessels.
  • Digestive system - The digestive system processes food into substances that different parts of the body can use for energy and nutrients. It includes organs such as the stomach, gallbladder, intestines, liver, and pancreas.
  • Endocrine system - The endocrine system uses hormones to regulate many functions throughout the entire body such as growth, mood, metabolism, and reproduction. Major organs in the endocrine system include glands such as the pituitary, thyroid, and adrenal glands.
  • Excretory system - The excretory system helps your body to get rid of food and toxins that it doesn't need. It includes organs such as the kidneys and bladder.
  • Integumentary system - The integumentary system protects the body from the outside world. It includes the skin, hair, and nails.
  • Muscular system - The muscular system is made up of all the muscles in our bodies. It is controlled by the nervous system.
  • Reproductive system - The reproductive system includes all the organs needed for reproduction. Unlike the rest of the organ systems, the reproductive system is different in males versus females.
  • Skeletal system - The skeletal system provides support and protection for the rest of the organ systems. It is made up of bones, ligaments, tendons, and cartilage.

Do plants have organs?

Yes, all complex living organisms have some types of organs. The three major organ systems in plants include roots, stems, and leaves. You can go to this page to learn more about the major structures of plants.

Chapter 15: Study Guide

Original Document: Chapter 15 Study Guide

1. What is peristalsis? __ muscular movements that push food through the alimentary canal __
2. What are papillae and where are they located? _______ taste buds, tongue ________________________
3. What is the roof of the oral cavity called (2 parts): _ soft and hard palate
Where is the uvula? back of the mouth, throat area
4. What are the three salivary glands and where are they located? parotid (ear), submandibular (below jaw), sublingual (below tongue)
5. What are the two types of movements within the alimentary canal? ___ mixing and propulsion ___
6. What are the three main functions of the digestive system?
1) mechanical and chemical break down of food
2) ____ absorption ____________ of nutrients
3) _____ elimination _____________ of wastes

7. What is the name of the opening where the esophagus pass through the diaphragm? _____ esophageal hiatus __________
8. What layer of the alimentary canal carries out absorption? mucosa
What layer contains glands, blood vessels, and nerves? submucosa
What layer contains the muscles? muscular
What layer covers the structures? serosa

9. What valve opens from the esophagus to the stomach? cardiac sphincter
What valve opens from the stomach to the small intestine? pyloric sphincter

10. What structure connects the tongue to the floor of the mouth? frenulum
11. What digestive enzyme is produced by the salivary glands? amylase
12. The part of the stomach that sits slightly above the esophagus is called the fundus
13. What is the hardest substance found in the body? tooth enamel
14. The central cavity of the tooth is made of dentin
The top of the tooth is called the crown
The part of the tooth that extends below the gums is called the root

15. The front teeth are called __ incisors ______. The back teeth are called ___ molars
The pointed teeth after the incisors are the ____ canines or cuspids __

16. What is food called after it has been broken down into a paste? chyme
What are the folds inside the stomach called? rugae

17. What causes jaundice in newborns? liver is not functioning
18. Trace the path of food once it enters the colon (follow through the parts)
ascending colon to transverse colon to descending colon
19. What is the function of the pancreas? digest foods
20. What does the bile duct connect? _ gall bladder _ to the duodenum
21. Where is the hepatic portal vein located? the liver
22. Trace the path of food from the stomach and through all of the parts of the small intestine:
stomach : duodenum >> jejunum >> ileum
* Which section is the longest? ileum
23. What is the function of the gall bladder? store bile
What is the function of bile? digest fats
24. What membrane holds the coils of the small intestine together? __ mesentery _
What membrane covers the organs of the digestive system like a curtain ? _____ greater omentum _______
25. What is the function of the intestinal villi? increase surface area for absorption

26. What part of the colon is located right before the rectum? __ sigmoid colon _________
27. Where is the cecum located? at the junction between the small intestine and the large intestine
What “useless” structure is attached to it? appendix
28. What part of the system stores waste prior to its elimination? rectum
29. What is a mass movement? defecation, elimination of solid waste

30. The “flora” of the large intestine is what? bacteria
31. What is the function of the large intestine? reabsorption of water
if this function does not work, what sickness can result? dysentery or diarrhea
32. If part of the small intestine pokes through the abdominal muscles, a person has a hernia
33. Hepatitis (A,B, or C) affects which organ of the digestive system? liver
34. The majority of a human’s diet should consist of what? grains, vegetables
35. What substance is mainly responsible for breaking down fats? bile
What substance is created in the stomach and breaks down food? pepsin

36. What is lactose intolerance? inability to break down milk (lactose)
37. What is another name for gastroesophageal reflux disease? acid reflux
38. The biliary system refers to the liver, pancreas and gall bladder.
What are the three ducts found in that system? hepatic, cystic, common bile

39. If a person has dysentery , they have a dangerous form of diarrhea

40. Be able to label structures of the digestive system on an image. (This includes a close-up view of the stomach and biliary system)

1. Esophagus
2. Cardiac Sphincter
3. Stomach
4. Pyloric Sphincter
5. Duodenum
6. Transverse Colon
7. Ascending Colon
8. Jejunum
9. Descending Colon
10. Sigmoid Colon
11. Ileum
12. Rectum
13. Appendix

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