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The Nose and its Adjacent Structures
Several bones that help form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal sinus is named for its associated bone:…
Muscles of Facial Expression
Many of the muscles of facial expression insert into the skin surrounding the eyelids, nose and mouth, producing facial expressions by moving the skin rather than bones.
Overview of the Muscular System
On the anterior and posterior views of the muscular system above, superficial muscles (those at the surface) are shown on the right side of the body while deep muscles (those underneath the superficial muscles) are shown on the left half of the body.…
Muscle Shapes and Fiber Alignment
The skeletal muscles of the body typically come in seven different general shapes.
Prime Movers and Synergists
The biceps brachii flex the lower arm. The brachoradialis, in the forearm, and brachialis, located deep to the biceps in the upper arm, are both synergists that aid in this motion.
Motor Units
A series of axon-like swelling, called varicosities or “boutons,” from autonomic neurons form motor units through the smooth muscle.
Muscle Contraction
The dense bodies and intermediate filaments are networked through the sarcoplasm, which cause the muscle fiber to contract.
Smooth Muscle Tissue
Smooth muscle tissue is found around organs in the digestive, respiratory, reproductive tracts and the iris of the eye.
Cardiac Muscle
Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes.
Atrophy
Muscle mass is reduced as muscles atrophy with disuse.
Types of Muscle Contractions
During isotonic contractions, muscle length changes to move a load. During isometric contractions, muscle length does not change because the load exceeds the tension the muscle can generate.
Muscle Metabolism
(a) Some ATP is stored in a resting muscle. As contraction starts, it is used up in seconds. More ATP is generated from creatine phosphate for about 15 seconds. (b) Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can…
Skeletal Muscle Contraction
(a) The active site on actin is exposed as calcium binds to troponin. (b) The myosin head is attracted to actin, and myosin binds actin at its actin-binding site, forming the cross-bridge. (c) During the power stroke, the phosphate generated in the…
The Sliding Filament Model of Muscle Contraction
When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments overlap completely.
Relaxation of a Muscle Fiber
Ca++ ions are pumped back into the SR, which causes the tropomyosin to reshield the binding sites on the actin strands. A muscle may also stop contracting when it runs out of ATP and becomes fatigued.
Contraction of a Muscle Fiber
A cross-bridge forms between actin and the myosin heads triggering contraction. As long as Ca++ ions remain in the sarcoplasm to bind to troponin, and as long as ATP is available, the muscle fiber will continue to shorten.
The T-tubule
Narrow T-tubules permit the conduction of electrical impulses. The SR functions to regulate intracellular levels of calcium. Two terminal cisternae (where enlarged SR connects to the T-tubule) and one T-tubule comprise a triad—a “threesome” of…
Behaviour, Development and Evolution
"The role of parents in shaping the characters of their children, the causes of violence and crime, and the roots of personal unhappiness are central to humanity. Like so many fundamental questions about human existence, these issues all relate to…
General Biology
The word biology means, "the science of life", from the Greek bios, life, and logos, word or knowledge. Therefore, Biology is the science of Living Things. That is why Biology is sometimes known as Life Science.
Radiation In The Environment
In the post-nuclear era the word ‘radiation’, in the popular lexicon, has taken on a specialized and negative meaning. Largely because of media misinterpretation the word now suggests to the non-scientist the malignant effects associated with…
Biostratigraphic And Geological Significance Of Planktonic Foraminifera
Foraminifera are marine, free-living, amoeboid protozoa
(in Greek, proto = first and zoa = animals). They are
single-celled eukaryotes (organisms the cytoplasm of
which is organized into a complex structure with internal
membranes and contains a…
(in Greek, proto = first and zoa = animals). They are
single-celled eukaryotes (organisms the cytoplasm of
which is organized into a complex structure with internal
membranes and contains a…
Microbiology
Microbiology is designed to cover the scope and sequence requirements for the single-semester Microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications of microbiology in healthcare…
Environmental Biology
Environmental Biology enables students to develop a nuanced understanding of today’s most pressing environmental issues. This text helps students grasp the scientific foundation of these issues so that they can better understand the world around…
Organic Chemistry With a Biological Emphasis: Volumes II
A free, open-access organic chemistry textbook (volumes I and II) in which the main focus is on relevance to biology and medicine. This is a PDF version of a wiki project called Chemwiki at the University of California, Davis. There are also…
Organic Chemistry With a Biological Emphasis: Volumes I
Open-access organic chemistry textbook (volumes I and II) in which the main focus is on relevance to biology and medicine. This is a PDF version of a wiki project called Chemwiki at the University of California, Davis. There are also supplementary…
Microbiology
This Microbiology textbook, adapted from the Boundless version, is intended to provide health care professionals with a working knowledge of infectious disease. Much of the book is devoted to the structure/function relationships in pathogenic…
All About Cells
Life. Every single living thing has something in common—do you know what that is? The clue is in the title! In this learning package you will learn all about cells—the parts and the functions of those parts. By learning about the basic building…
Clinical Biochemistry
The pre-analytical phase is defined as the period from the physician’s indication of the test up to the laboratory
analysis of the biological material. In other words, this phase involves an individual’s preparation for collection of the…
analysis of the biological material. In other words, this phase involves an individual’s preparation for collection of the…
Concepts of Biology-1st Canadian Edition
In this survey text, directed at those not majoring in biology, we dispel the assumption that a little learning is a dangerous thing. We hope that by skimming the surface of a very deep subject, biology, we may inspire you to drink more deeply and…
What is DNA
DNA (deoxyribose nucleic acid) is extremely important. All living things have DNA, or in the case of some viruses they have RNA instead.
In eukaryotes, it is found within the nucleus and is arranged into chromosomes.
DNA determines the…
In eukaryotes, it is found within the nucleus and is arranged into chromosomes.
DNA determines the…