Critical Thinking Questions

What materials can easily diffuse through the lipid bilayer, and why?

Only materials that are relatively small and nonpolar can easily diffuse through the lipid bilayer. Large particles cannot fit in between the individual phospholipids that are packed together, and polar molecules are repelled by the hydrophobic/nonpolar lipids that line the inside of the bilayer.This includes gases like oxygen and carbon dioxide, as well as small nonpolar molecules.

Why is receptor-mediated endocytosis said to be more selective than phagocytosis or pinocytosis?

Receptor-mediated endocytosis is more selective because the substances that are brought into the cell are the specific ligands that could bind to the receptors being endocytosed. Phagocytosis or pinocytosis, on the other hand, have no such receptor-ligand specificity, and bring in whatever materials happen to be close to the membrane when it is enveloped.

What do osmosis, diffusion, filtration, and the movement of ions away from like charge all have in common? In what way do they differ?

are similar in the sense that they describe the movement of substances down a particular type of gradient. Osmosis and diffusion involve the movement of water and other substances down their concentration gradients, respectively. Filtration describes the movement of particles down a pressure gradient, and ion movement can be both passive or active, depending on the energy requirement and is down their electrical gradient.

Explain why the structure of the ER, mitochondria, and Golgi apparatus assist their respective functions.

A mitochondrion is a membranous, been-shaped organelle it generates ATP in the cell. The inner membrane is buried in the matrix which increases the surface area for increased gaseous exchange is known as cristae. Enzymes and other molecules are associated with inner membrane which helps in cellular respiration. Cellular respiration results in production of ATP from nutrient molecules like glucose.

The Golgi apparatus is a cell organelle responsible for processing or modification of proteins, sorting out protein and translocation to different locations in the cell. The proteins after processing in the endoplasmic reticulum are transported to Golgi bodies for further modification.

Golgi apparatus and ER work together to synthesise proteins and lipids. Mitochondria are called the power house of the cell. Respiration takes place inside mitochondria which produces ATP.

Compare and contrast lysosomes with peroxisomes: name at least two similarities and one difference.

Peroxisomes and lysosomes are both cellular organelles bound by lipid bilayer membranes, and both contain many enzymes. However, peroxisomes contain enzyme that detoxify substances by transferring hydrogen atoms and producing H2O2, whereas the enzymes in lysosomes function to break down and digest various unwanted materials.

Explain in your own words why DNA replication is said to be “semiconservative”?

DNA replication is termed "semiconservative" because each new double helix contains one original strand and one newly synthesized strand. This method ensures that each daughter DNA molecule preserves half of the parental DNA, thus conserving genetic information.

Why is it important that DNA replication take place before cell division? What would happen if cell division of a body cell took place without DNA replication, or when DNA replication was incomplete?

It is crucial for DNA replication to occur before cell division to ensure that each daughter cell receives an identical set of genetic material. If cell division occurs without complete DNA replication, it could result in cells with incomplete or damaged DNA, leading to genetic abnormalities and dysfunctional cell function.

Briefly explain the similarities between transcription and DNA replication.

Both transcription and DNA replication involve the synthesis of nucleic acid from a DNA template. They share similar processes in unwinding the DNA helix and using complementary base pairing, but while replication synthesizes DNA, transcription produces RNA.

Contrast transcription and translation. Name at least three differences between the two processes.

Transcription is really a "copy" process and translation is an "interpretation" process, because transcription involves copying the DNA message into a very similar RNA message whereas translation involves converting RNA message into the very different amino acid message. Transcription is the process of synthesizing RNA from a DNA template, while translation involves converting RNA sequences into amino acids to form proteins. Key differences include: 1) Transcription occurs in the nucleus while translation takes place in the cytoplasm. 2) Transcription produces RNA, whereas translation produces proteins. 3) Transcription uses RNA polymerase, whereas translation relies on ribosomes.

What would happen if anaphase proceeded even though the sister chromatids were not properly attached to their respective microtubules and lined up at the metaphase plate?

It could result in an unequal distribution of chromosomes to the daughter cells. This would lead to aneuploidy, where one cell may end up with an extra chromosome while the other may lack one, potentially causing severe developmental issues or diseases.

What are cyclins and cyclin-dependent kinases, and how do they interact?

A cyclin is one of the primary classes of cell cycle control molecules, while a cyclin-dependent kinase is one of a group of molecules that work together with cyclins to determine past cell checkpoints. By interacting with many additional molecules, these triggers push the cell cycle forward unless prevented from doing so by "stop" signals, if for some reason the cell isn't ready.

Cyclins are regulatory proteins that control the progression of the cell cycle by activating cyclin-dependent kinases (CDKs). CDKs are enzymes that, when bound to cyclins, phosphorylate target proteins to advance the cell through various checkpoints in the cell cycle.

Explain how a transcription factor ultimately determines whether or not a protein will be present in a given cell?

Transcription factors bind to DNA and either promote or inhibit the transcription of a gene. If they promote the transcription of a particular gene, then that gene will be transcribed and the mRNA subsequently translated into protein. If gene transcription is inhibited, then there will be no way of synthesizing the gene's corresponding protein.

Discuss two reasons why the therapeutic use of embryonic stem cells can present a problem.

One reason is the ethical concerns surrounding the destruction of embryos during the harvesting process. Additionally, there is a risk of immune rejection when the stem cells are transplanted into patients, as they may be perceived as foreign by the patient's immune system.

Identify the four types of tissue in the body, and describe the major functions of each tissue.

The four types of tissue in the body are epithelial, connective, muscle, and nervous. Epithelial tissue is made of layers of cells that cover the surfaces of the body that come into contact with the exterior world, line internal cavities, and form glands. Connective tissue binds the cells and organs of the body together and performs many functions, especially in the protection, support, and integration of the body. Muscle tissue, which responds to stimulation and contracts to provide movement, is divided into three major types: skeletal (voluntary) muscles, smooth muscles, and the cardiac muscle in the heart. Nervous tissue allows the body to receive signals and transmit information as electric impulses from one region of the body to another.

The zygote is described as totipotent because it ultimately gives rise to all the cells in your body including the highly specialized cells of your nervous system. Describe this transition, discussing the steps and processes that lead to these specialized cells.

The zygote divides into many cells. As these cells become specialized, they lose their ability to differentiate into all tissues. At first they form the three primary germ layers. Following the cells of the ectodermal germ layer, they too become more restricted in what they can form. Ultimately, some of these ectodermal cells become further restricted and differentiate in to nerve cells.

What is the function of synovial membranes?

Synovial membranes are a type of connective tissue membrane that supports mobility in joints. The membrane lines the joint cavity and contains fibroblasts that produce hyaluronan, which leads to the production of synovial fluid, a natural lubricant that enables the bones of a joint to move freely against one another.

The structure of a tissue usually is optimized for its function. Describe how the structure of individual cells and tissue arrangement of the intestine lining matches its main function, to absorb nutrients.

Columnar epithelia, which form the lining of the digestive tract, can be either simple or stratified. The cells are long and narrow. The nucleus is elongated and located on the basal side of the cell. Ciliated columnar epithelium is composed of simple columnar epithelial cells that display cilia on their apical surfaces.

One of the main functions of connective tissue is to integrate organs and organ systems in the body. Discuss how blood fulfills this role.

Blood is a fluid connective tissue, a variety of specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins in a liquid extracellular matrix. Blood contains formed elements derived from bone marrow. Erythrocytes, or red blood cells, transport the gases oxygen and carbon dioxide. Leukocytes, or white blood cells, are responsible for the defense of the organism against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some cells have the ability to cross the endothelial layer that lines vessels and enter adjacent tissues. Nutrients, salts, and waste are dissolved in the liquid matrix and transported through the body.

Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture?

A layer of dense irregular connective tissue covers cartilage. No blood vessels supply cartilage tissue. Injuries to cartilage heal very slowly because cells and nutrients needed for repair diffuse slowly to the injury site.

You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at.

The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract. When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony.

Why does skeletal muscle look striated?

Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin.

Which morphological adaptations of neurons make them suitable for the transmission of nerve impulse?

Neurons are well suited for the transmission of nerve impulses because short extensions, dendrites, receive impulses from other neurons, while a long tail extension, an axon, carries electrical impulses away from the cell to other neurons.

What are the functions of astrocytes?

Astrocytes regulate ions and uptake and/or breakdown of some neurotransmitters and contribute to the formation of the blood-brain-barrier.

Why is it important to watch for increased redness, swelling and pain after a cut or abrasion has been cleaned and bandaged?

These symptoms would indicate that infection is present.

Aspirin is a non-steroidal anti-inflammatory drug (NSAID) that inhibits the formation of blood clots and is taken regularly by individuals with a heart condition. Steroids such as cortisol are used to control some autoimmune diseases and severe arthritis by down-regulating the inflammatory response. After reading the role of inflammation in the body's response to infection, can you predict an undesirable consequence of taking anti-inflammatory drugs on a regular basis?

Since NSAIDs or other anti-inflammatory drugs inhibit the formation of blood clots, regular and prolonged use of these drugs may promote internal bleeding, such as bleeding in the stomach. Excessive levels of cortisol would suppress inflammation, which could slow the wound healing process.

As an individual ages, a constellation of symptoms begins the decline to the point where an individual's functioning is compromised. Identify and discuss two factors that have a role in factors leading to the compromised situation.

The genetic makeup and the lifestyle of each individual are factors which determine the degree of decline in cells, tissues, and organs as an individual ages.

Discuss changes that occur in cells as a person ages.

All cells experience changes with aging. They become larger, and many cannot divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products are not as efficient in the elderly. Cells lose their ability to function, or they begin to function abnormally, leading to disease and cancer.

What determines the color of skin, and what is the process that darkens skin when it is exposed to UV light?

The pigment melanin, produced by melanocytes, is primarily responsible for skin color, carotene(yellow/orange), and hemoglobin(red/pink) are also skin pigments. Melanin comes in different shades of brown and black. Individuals with darker skin have darker, more abundant melanin, whereas fair-skinned individuals have a lighter shade of skin and less melanin. Exposure to UV irradiation stimulates the melanocytes to produce and secrete more melanin, thus causing you to get darker.

Cells of the epidermis derive from stem cells of the stratum basale. Describe how the cells change as they become integrated into the different layers of the epidermis.

As the cells move into the stratum spinosum, they begin the synthesis of keratin and extend cell processes, desmosomes, which link the cells. As the stratum basale continues to produce new cells, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. The cells become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin and keratohyalin. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that form the stratum lucidum and the stratum corneum. The keratinocytes in these layers are mostly dead and flattened. Cells in the stratum corneum are periodically shed.

Explain the differences between eccrine and apocrine sweat glands.

Eccrine sweat glands - secrete through pores on the skin and are all over the body, especially forehead and palms of the hand and they release a watery sweat mixed with some metabolic waste antibodies.

Apocrine sweat glands - secrete into the hair follicle. Larger than eccrine and are deeper in the dermis, sometimes reaching the hypodermis and they release a thicker smelly sweat decomposed by bacteria on the skin. Found in the axillary and anogenital regions. Only active after puberty occurs.

Describe the structure and composition of nails.

Nail body is formed on the nail bed at the nail root and composed of densely packed keratinocytes.

Nail folds help anchor nail to the body and meet the proximal end to create the cuticle.Nail bed is rich in blood vessels.

Hyponychium is under the free edge and composed of a thickened layer of stratum coronium

Why do people sweat excessively when exercising outside on a hot day?

Sweating cools the body. When body temp rises, the dermal blood vessels dilate and the sweat glands begin to secrete more sweat. When the sweat evaporates it cools the body by dissipating heat.

Explain your skin’s response to a drop in body core temperature.

The skin responds by constricting blood vessels and forming goosebumps. These reactions help retain heat within the body, preventing further temperature decrease.

Why do teenagers often experience acne?

Acne is a result from a blockage of sebaceous glands by sebum. Teenagers have acne due to puberty which is when the sebaceous glands become active. Hormones that are active during puberty can also stimulate the release of sebum

Why do scars look different from surrounding skin?

Scaring occurs when the skin fails to regenerate to the original skin structure. Fibroblasts generate scar tissue in the form of collagen.

The skeletal system is composed of bone and cartilage and has many functions. Choose three of these functions and discuss what features of the skeletal system allow it to accomplish these functions.

1. It supports the body. The rigid, yet flexible skeleton acts as a framework to support the other organs of the body.

2. It aids in movement. The movable joints allow the skeleton to change shapes and positions.

3. It protects internal organs. Parts of the skeleton enclose or partly enclose various organs of the body including our brain, ears, heart, and lungs. Any trauma to these organs has to be mediated through the skeletal system.

What are the structural and functional differences between a tarsal and a metatarsal?

Structurally, a tarsal is a short bone, meaning its length, width, and thickness are about equal, while a metatarsal is a long bone whose length is greater than its width. Functionally, the tarsal provides limited motion, while the metatarsal acts as a lever.

What are the structural and functional differences between the femur and the patella?

Structurally;
Femur - Long bone.
Patella - Sesamoid

Functional;
The femur acts as a lever, while the patella protects the patellar tendon from compressive forces.

If the articular cartilage at the end of one of your long bones were to degenerate, what symptoms do you think you would experience? Why?

If the articular cartilage at the end of one of your long bones were to deteriorate, which is actually what happens in osteoarthritis, you would experience joint pain at the end of that bone and limitation of motion at that joint because there would be no cartilage to reduce friction between adjacent bones and there would be no cartilage to act as a shock absorber.

In what ways is the structural makeup of compact and spongy bone well suited to their respective functions?

The densely packed concentric rings of matrix in compact bone are ideal for resisting compressive forces, which is the function of compact bone. The open spaces of the trabeculated network of spongy bone allow spongy bone to support shifts in weight distribution, which is the function of spongy bone.

In what ways do intramembranous and endochondral ossification differ?

In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue, but in endochondral ossification, bone develops by replacing hyaline cartilage. Intramembranous ossification is complete by the end of the adolescent growth spurt, while endochondral ossification lasts into young adulthood. The flat bones of the face, most of the cranial bones, and a good deal of the clavicles (collarbones) are formed via intramembranous ossification, while bones at the base of the skull and the long bones form via endochondral ossification.

Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center?

A single primary ossification center is present, during endochondral ossification, deep in the periosteal collar. Like the primary ossification center, secondary ossification centers are present during endochondral ossification, but they form later, and there are two of them, one in each epiphysis.

What is the difference between closed reduction and open reduction? In what type of fracture would closed reduction most likely occur? In what type of fracture would open reduction most likely occur?

In closed reduction, the broken ends of a fractured bone can be reset without surgery. Open reduction requires surgery to return the broken ends of the bone to their correct anatomical position. A partial fracture would likely require closed reduction. A compound fracture would require open reduction

In terms of origin and composition, what are the differences between an internal callus and an external callus?

The internal callus is produced by cells in the endosteum and is composed of a fibrocartilaginous matrix. The external callus is produced by cells in the periosteum and consists of hyaline cartilage and bone.

If you were a dietician who had a young female patient with a family history of osteoporosis, what foods would you suggest she include in her diet? Why?

Since maximum bone mass is achieved by age 30, I would want this patient to have adequate calcium and vitamin D in her diet. To do this, I would recommend ingesting milk and other dairy foods, green leafy vegetables, and intact canned sardines so she receives sufficient calcium. Intact salmon would be a good source for calcium and vitamin D. Other fatty fish would also be a good vitamin D source.

During the early years of space exploration our astronauts, who had been floating in space, would return to earth showing significant bone loss dependent on how long they were in space. Discuss how this might happen and what could be done to alleviate this condition.

Astronauts floating in space were not exerting significant pressure on their bones; they were "weightless." Without the force of gravity exerting pressure on the bones, bone mass was lost. To alleviate this condition, astronauts now do resistive exercise designed to apply forces to the bones and thus help keep them healthy.

An individual with very low levels of vitamin D presents themselves to you complaining of seemingly fragile bones. Explain how these might be connected.

Vitamin D is required for calcium absorption by the gut. Low vitamin D could lead to insufficient levels of calcium in the blood so the calcium is being released from the bones. The reduction of calcium from the bones can make them weak and subject to fracture.

Describe the effects caused when the parathyroid gland fails to respond to calcium bound to its receptors.

Under "normal" conditions, receptors in the parathyroid glands bind blood calcium. When the receptors are full, the parathyroid gland stops secreting PTH. In the condition described, the parathyroid glands are not responding to the signal that there is sufficient calcium in the blood and they keep releasing PTH, which causes the bone to release more calcium into the blood. Ultimately, the bones become fragile and hypercalcemia can result.

Define how joints are classified based on function. Describe and give an example for each functional type of joint.

The functional classification of joints is determined by the amount of mobility found between the adjacent bones. Joints are thus functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, which is a freely moveable joint (arthroun = “to fasten by a joint”). Depending on their location, fibrous joints may be functionally classified as a synarthrosis (immobile joint) or an amphiarthrosis (slightly mobile joint). Cartilaginous joints are also functionally classified as either a synarthrosis or an amphiarthrosis joint. All synovial joints are functionally classified as a diarthrosis joint.

Explain the reasons for why joints differ in their degree of mobility.

the functional needs of joints vary and thus joints differ in their degree of mobility. A synarthrosis, which is an immobile joint, serves to strongly connect bones thus protecting internal organs such as the heart or brain. A slightly movable amphiarthrosis provides for small movements, which in the vertebral column can add together to yield a much larger overall movement. The freedom of movement provided by a diarthrosis can allow for large movements, such as is seen with most joints of the limbs

Distinguish between a narrow and wide fibrous joint and give an example of each.

Narrow fibrous joints are found at a suture, gomphosis, or syndesmosis. A suture is the fibrous joint that joins the bones of the skull to each other (except the mandible). A gomphosis is the fibrous joint that anchors each tooth to its bony socket within the upper or lower jaw. The tooth is connected to the bony jaw by periodontal ligaments. A narrow syndesmosis is found at the distal tibiofibular joint where the bones are united by fibrous connective tissue and ligaments. A syndesmosis can also form a wide fibrous joint where the shafts of two parallel bones are connected by a broad interosseous membrane. The radius and ulna bones of the forearm and the tibia and fibula bones of the leg are united by interosseous membranes.

The periodontal ligaments are made of collagen fibers and are responsible for connecting the roots of the teeth to the jaws. Describe how scurvy, a disease that inhibits collagen production, can affect the teeth.

the teeth are anchored into their sockets within the bony jaws by the periodontal ligaments. This is a gomphosis type of fibrous joint. In scurvy, collagen production in inhibited and the periodontal ligaments become weak. This will cause the teeth to become loose or even to fall out

Describe the two types of cartilaginous joints and give examples of each.

Cartilaginous joints are where the adjacent bones are joined by cartilage. At a synchondrosis, the bones are united by hyaline cartilage. The epiphyseal plate of growing long bones and the first sternocostal joint that unites the first rib to the sternum are examples of synchondroses. At a symphysis, the bones are joined by fibrocartilage, which is strong and flexible. Symphysis joints include the intervertebral symphysis between adjacent vertebrae and the pubic symphysis that joins the pubic portions of the right and left hip bones.

Both functional and structural classifications can be used to describe an individual joint. Define the first sternocostal joint and the pubic symphysis using both functional and structural characteristics.

the first sternocostal joint is a synchondrosis type of cartilagnious joint in which hyaline cartilage unites the first rib to the manubrium of the sternum. This forms an immobile (synarthrosis) type of joint. The pubic symphysis is a slightly mobile (amphiarthrosis) cartilaginous joint, where the pubic portions of the right and left hip bones are united by fibrocartilage, thus forming a symphysis

Describe the characteristic structures found at all synovial joints.

All synovial joints have a joint cavity filled with synovial fluid that is the site at which the bones of the joint articulate with each other. The articulating surfaces of the bones are covered by articular cartilage, a thin layer of hyaline cartilage. The walls of the joint cavity are formed by the connective tissue of the articular capsule. The synovial membrane lines the interior surface of the joint cavity and secretes the synovial fluid. Synovial joints are directly supported by ligaments, which span between the bones of the joint. These may be located outside of the articular capsule (extrinsic ligaments), incorporated or fused to the wall of the articular capsule (intrinsic ligaments), or found inside of the articular capsule (intracapsular ligaments). Ligaments hold the bones together and also serve to resist or prevent excessive or abnormal movements of the joint.

Describe the structures that provide direct and indirect support for a synovial joint.

direct support for a synovial joint is provided by ligaments that strongly unite the bones of the joint and serve to resist excessive or abnormal movements. Some joints, such as the sternoclavcular joint, have an articular disc that is attached to both bones, where it provides direct support by holding the bones together. Indirect joint support is provided by the muscles and their tendons that act across a joint. Muscles will increase their contractile force to help support the joint by resisting forces acting on it

Briefly define the types of joint movements available at a ball-and-socket joint.

Ball-and-socket joints are multiaxial joints that allow for flexion and extension, abduction and adduction, circumduction, and medial and lateral rotation.

Discuss the joints involved and movements required for you to cross your arms together in front of your chest.

to cross your arms, you need to use both your shoulder and elbow joints. At the shoulder, the arm would need to flex and medially rotate. At the elbow, the forearm would need to be flexed

Discuss the structures that contribute to support of the shoulder joint.

The shoulder joint allows for a large range of motion. The primary support for the shoulder joint is provided by the four rotator cuff muscles. These muscles serve as "dynamic ligaments" and thus can modulate their strengths of contraction as needed to hold the head of the humerus in position at the glenoid fossa. Additional but weaker support comes from the coracohumeral ligament, an intrinsic ligament that supports the superior aspect of the shoulder joint, and the glenohumeral ligaments, which are intrinsic ligaments that support the anterior side of the joint.

Describe the sequence of injuries that may occur if the extended, weight-bearing knee receives a very strong blow to the lateral side of the knee.

a strong blow to the lateral side of the extended knee will cause the medial side of the knee joint to open, resulting in a sequence of three injuries. First will be damage to the tibial collateral ligament. Since the medial meniscus is attached to the tibial collateral ligament, the meniscus is also injured. The third structure injured would be the anterior cruciate ligament.

Describe how synovial joints develop within the embryonic limb.

Mesenchyme gives rise to cartilage models of the future limb bones. An area called the joint interzone located between adjacent cartilage models will become a synovial joint. The cells at the center of the interzone die, thus producing the joint cavity. Additional mesenchyme cells at the periphery of the interzone become the articular capsule

Differentiate between endochondral and intramembranous ossification.

Endochondral ossification: the process that replaces hyaline cartilage with bone tissue

Intramembranous ossification: produces the bones of the top and sides of the skull

Why is elasticity an important quality of muscle tissue?

The elasticity of a muscle allows it to stretch and return to its original length over and over again

What would happen to skeletal muscle if the epimysium were destroyed?

Muscles would lose integrity during powerful movements, resulting in damage to the muscle

Describe how tendons facilitate body movement.

when a muscle contracts, the force of the movement is transmitted through the tendon, which pulls on the bone to produce skeletal movement

What are the five primary functions of skeletal muscle?

produce movement, maintain posture, support soft tissues, encircle openings of the digestive urinary and other tracts, and maintain body temperature

What are the opposite roles of voltage-gated sodium channels and voltage-gated potassium channels?

The opening of voltage-gated sodium channels, followed by the influx of Na+, transmits the action potential after the membrane has sufficiently depolarized. The Delayed opening of he potassium channels allows K+ to exit the cell to depolarize the membrane.

How would muscle contractions be affected if skeletal muscle fibers did not have T-tubules?

Without T-tubules, action potential conduction into the interior of the cell would happen much more slowly, causing delays between neural stimulation and muscle contraction, resulting in slower weaker contractions

What causes the striated appearance of skeletal muscle tissue?

Dark A bands and light I bands repeat along myofibrils in the cell and cause the entire cell to appear striated

How would muscle contractions be affected if ATP was completely depleted in a muscle fiber?

Without ATP, Myosin heads cannot detach from the actin-binding sites. All of the "stuck" cross bridges result in muscle stiffness. Example, rigor mortis.

Why does a motor unit of the eye have few muscle fibers compared to a motor unit of the leg?

The eyes require fine movements and a higher degree of control, which is permitted by having fewer muscle fibers associated with a neuron

What factors contribute to the amount of tension produced in an individual muscle fiber?

The length, size, type of muscle fiber, and frequency of neural stimulation contribute to the amount of tension produced in an individual muscle fiber.

Why do muscle cells use creatine phosphate instead of glycolysis to supply ATP for the first few seconds of muscle contraction?

Creatine phosphate is used because creatine phosphate and ADP are converted very quickly into ATP by creatine kinase. Glycolysis cannot generate ATP as quickly as creatine phosphate.

Is aerobic respiration more or less efficient than glycolysis? Explain your answer.

Aerobic respiration is much more efficient that anaerobic glycolysis yielding 36 ATP per molecule of glucose, as opposed to two ATP produced by glycolysis.

What changes occur at the cellular level in response to endurance training?

Endurance training modifies slow fibers to make them more efficient by producing more mitochondria to enable more aerobic metabolism and more ATP production. Endurance exercise can also increase the amount of myoglobin in a cell and formation of more extensive capillary networks around muscle fiber.

What changes occur at the cellular level in response to resistance training?

Resistance exercises affect muscles by causing the formation of more actin and myosin, increasing the structure of the muscle fibers.

What would be the drawback of cardiac contractions being the same duration as skeletal muscle contractions?

An action potential could reach a cardiac muscle before it has entered the relaxation phase , resulting in sustained contractions of tetanus. If this happened, the heart would not beat regularly.

How are cardiac muscle cells similar to and different from skeletal muscle cells?

Cardiac and skeletal muscle cells both contain ordered myofibrils and are striated. Cardiac muscle cells are branched and contain intercalated discs, which skeletal muscle does not contain

Why can smooth muscles contract over a wider range of resting lengths than skeletal and cardiac muscle?

Smooth muscles can contract over a wider range of resting lengths because the actin and myosin filaments in smooth muscle are not as rigidly organized as those in skeletal and cardiac muscle.

Describe the differences between single-unit smooth muscle and multiunit smooth muscle.

Single-unit smooth muscle and multi-unit smooth muscle differ in their organization, innervation, and function. Single-unit smooth muscle cells are electrically coupled via gap junctions, allowing for coordinated contractions, while multi-unit smooth muscle cells are less connected and contract independently.

Why is muscle that has sustained significant damage unable to produce the same amount of power as it could before being damaged?

If the damage exceeds what can be repaired by the satellite cells, the damaged tissue is replaced by scar tissue, which cannot contract

Which muscle type(s) (skeletal, smooth, or cardiac) can regenerate new muscle cells/fibers? Explain your answer.

Smooth muscle can regenerate from stem cells called pericytes, cells found in some small blood vessels. These allow smooth muscle cells to regenerate and repair more readily than skeletal and cardiac muscle tissue.

What effect does fascicle arrangement have on a muscle’s action?

Fascicle arrangements determine what type of movement a muscle can make

Movements of the body occur at joints. Describe how muscles are arranged around the joints of the body.

Muscles work in pairs to facilitate movement of the bones around the joints. Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist the agonists, and fixators stabilize a muscle's origin.

Explain how a synergist assists an agonist by being a fixator.

Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist the agonists, and fixators stabilize a muscle's origin.

Describe the different criteria that contribute to how skeletal muscles are named.

In anatomy and physiology, many word roots are Latin or Greek. Portions, or roots, of the word give us clues about the function, shape, action, or location of a muscle.

Explain the difference between axial and appendicular muscles.

Axial muscles originate on the axial skeleton (the bones in the head, neck, and core of the body), whereas appendicular muscles originate on the bones that make up the body's limbs.

Describe the muscles of the anterior neck.

The muscles of the anterior neck are arranged to facilitate swallowing and speech. They work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down.

Why are the muscles of the face different from typical skeletal muscle?

Most skeletal muscles create movement by actions on the skeleton. Facial muscles are different in that they create facial movements and expressions by pulling on the skin—no bone movements are involved.

Describe the fascicle arrangement in the muscles of the abdominal wall. How do they relate to each other?

Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.

What are some similarities and differences between the diaphragm and the pelvic diaphragm?

Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk.

The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?

Tendons of the infraspinatus, supraspinatus, teres minor, and the subscapularis form the rotator cuff, which forms a foundation on which the arms and shoulders can be stabilized and move.

List the general muscle groups of the shoulders and upper limbs as well as their subgroups.

The muscles that make up the shoulders and upper limbs include the muscles that position the pelvic girdle, the muscles that move the humerus, the muscles that move the forearm, and the muscles that move wrists, hand, and fingers.

Which muscles form the hamstrings? How do they function together?

The biceps femoris, semimembranosus, and semitendinosus form the hamstrings. The hamstrings flex the leg at the knee joint.
responsible for stabilizing the shoulder joint

Which muscles form the quadriceps? How do they function together?

The rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius form the quadriceps. The quadriceps muscles extend the leg at the knee joint.

What responses are generated by the nervous system when you run on a treadmill? Include an example of each type of tissue that is under nervous system control.

Running on a treadmill involves contraction of the skeletal muscles in the legs, increase in contraction of the cardiac muscle of the heart, and the production and secretion of sweat in the skin to stay cool.

When eating food, what anatomical and functional divisions of the nervous system are involved in the perceptual experience?

The sensation of taste associated with eating is sensed by nerves in the periphery that are involved in sensory and somatic functions.

Multiple sclerosis is a demyelinating disease affecting the central nervous system. What type of cell would be the most likely target of this disease? Why?

The disease would target oligodendrocytes. In the CNS, oligodendrocytes provide the myelin for axons.

Which type of neuron, based on its shape, is best suited for relaying information directly from one neuron to another? Explain why.

Bipolar cells, because they have one dendrite that receives input and one axon that provides output, would be a direct relay between two other cells

Sensory fibers, or pathways, are referred to as “afferent.” Motor fibers, or pathways, are referred to as “efferent.” What can you infer about the meaning of these two terms (afferent and efferent) in a structural or anatomical context?

Afferent means "toward," as in sensory information traveling from the periphery into the CNS. Efferent means "away from," as in motor commands that travel from the brain down the spinal cord and out into the periphery.