Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide cold water and chicken wings will satisfy such desires. Trace the path of “the wings” from the mouth to the anus, listing the path in as much detail as possible. Again, be very specific and very detailed including the absorption/elimination of nutrients/wastes.

Digestion starts with the cephalic phase, when the senses of smell, sight, sound, or the thought of food activates neural centers in the brain, which stimulate the facial and glossopharyngeal nerves that in turn stimulate the salivary glands to secret saliva. Also the vagus nerves are activated, which in turn stimulate the gastric glands to secrete gastric juice. This stage prepares the mouth and stomach for eating the food.

The gastric phase of digestion starts in the mouth with ingestion of the food. Here, food is being masticated first with the help of tongue, teeth, mandible, muscles of the mandible, and temporomandibular joints. To help mastication, the salivary glands secret saliva, which helps dissolve the food and start digestion. Saliva lubricates the food, preparing it for its journey down into the esophagus. It also produces an enzyme that digests starch. Mechanical digestion involves grinding of the food by the teeth, mixing the food with the saliva, and maneuvering it by the tongue to be swallowed. During this process, the food is transformed into a bolus which is being forced back of the mouth, by the tongue, into the oropharynx. The next step is the swallowing of the bolus/food, passing it from the mouth into the pharynx. This is a voluntary action, hence the voluntary stage. Immediately after the swallowing, digestion becomes an involuntary action: this is the pharyngeal stage of swallowing. The tongue rises against the palate, nasopharynx closes off by the upward movement of uvula and soft palate, and breathing is temporarily interrupted; larynx rises and epiglottis seals it off, vocal chords come together, and the bolus of food passes through the laryngopharynx into the esophagus when the upper esophageal sphincter relaxes to allow the bolus into the esophagus. The bolus has now reached the esophageal stage where peristalsis occurs and the bolus is moved downward the esophagus, toward the stomach. The esophagus has mucus glands in its wall which also help to further lubricate the food on its journey down to the stomach, and muscular waves which travels from the top to the bottom of the esophagus to get the food down to the stomach. At the end of the esophagus, the lower esophageal sphincter relaxes and allows the bolus to pass into the stomach.

The food lands into the stomach four-five seconds after it has been swallowed. Right next to where the esophagus comes into the stomach is the fundus, where the gas formed inside the stomach builds up and is eliminated through a burp. Now the stomach wall is stretched, no more rugae because this was a big meal. pH of the contents increases because some of the acid in the stomach got buffered by the proteins in the food, which triggers nerve impulses to stimulate the flow of gastric juices made of pepsinogen - pepsin and intrinsic factor, which initiates mixing waves, which macerate the food, mixing it with secretion of the gastric glands. Pepsine breaks up the protein into smaller units. This generates the production of the pasty chyme. The mixing waves generates gastric emptying – passing a little bit of the chyme through the pyloric sphincter, which is partially closed, into the duodenum. During the stomachal chemical digestion, pepsin breaks the peptide bonds between amino acids in proteins, which in turn are fragmented into peptides. When reaching the small intestine, the chyme contains partially digested carbohydrates and proteins. In two to four hours after eating, the stomach has finished emptying the chyme into the small intestine, and the intestinal phase of digestion begins.

The small intestine is the real engine-room of the bowel, as this is where the food is finally broken down into its elementary constituents, and absorbed into the bloodstream. Here the chyme will remain for three to five hours. The mechanical digestion in the small intestine includes segmentation and peristalsis. The chemical digestion is a joint effort of pancreatic juice, bile, and the intestinal juice. The pancreas secrets pancreatic juice to inactivated the pepsin from the stomach and generate an optimal environment for the enzymes in the small intestine, continuing the digestion of proteins begun in the stomach. The pancreatic juice includes pancreatic amylase for digesting starches; trypsin, chymotrypsin and carboxypeptidase to digest proteins; pancreatic lipase to digest triglycerides, and ribonuclease/deoxyribonuclease to digest nucleic acids. Enzymes of the small intestine break down disaccharides into monosaccharides: the sucrase enzyme breaks down sucrose, the maltase enzyme breaks down maltose, and the enzyme lactase digests lactose. The bile salts produced by the liver, stored in the gallbladder, are also secreted to emulsify triglycerides. At the end of this breaking down process, the molecules – the final products of digestion, are ready to be absorbed through the mucosa into the blood and lymphatic streams. Ninety percent of this absorption happens in the small intestine, through simple diffusion, osmosis and active transport. Nutrients broken down during digestion will travel through the bloodstream into the liver, the main metabolic factory of the body, where they will be processed according to the body’s needs. In the liver, glycogen is broken down to glucose, and some amino acids, lactic acids plus other sugars are also converted into glucose. The liver breaks down fatty acids to produce ATP, synthesizes lipoproteins to transport triglycerides and cholesterol, synthesizes cholesterol and uses it to produce bile salts. The liver stores glycogen, vitamins A, D, E and K, iron, copper, and participates in the synthesis of vitamin D.

The rest of ten percent of absorption occurs during the stomachal stage of digestion and in the large intestine. The material left over after absorption occurs in the small intestine, passes through the ileocecal sphincter into the large intestine. This is a slow passage, as the ileocecal sphincter is slightly contracted. Here the chyme will remain for three to ten hours. In the large intestine, completion of absorption occurs, some vitamins are synthesized, and feces are formed and eliminated. Peristalsis occurs slower. Bacteria ferment the remaining carbohydrates, releasing gases that contribute to the flatus. Other components that are broken down here by bacteria are the remaining proteins, and some vitamins. Bilirubin is being decomposed into pigments, one of them being stercobilin which gives the brown color to feces – the solidified chyme. This material is pushed into the rectum through mass peristaltic movements. Defecation reflex is initiated and the rectum is being emptied through the anus. This is the end of the journey of digestion, from the tongue to the anus.

Resources:

Coleman, D. (Director). (2005). Anatomy for beginners: Lesson 3, Digestion. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Fraternal twins ...

A. develop from a single fertilized ovum.
B. are the same age but genetically different.
C. are genetically identical.
D. are always the same sex.
E. are fertilized by one sperm cell.

The first line of defense against pathogens is ...

 A. phagocytosis.
 B. production of antibodies.
 C. inflammation.
 D. the intact skin.
 E. immunity.

Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide cold water and chicken wings will satisfy such desires. Specify the movements, muscles, bones and joints involved in opening your mouth and chewing the wings. Explain any and all movements individually across each joint involved specifying the actions involved (i.e. flexion, extension, etc.), the muscles causing such actions, the bones being pulled on by said muscles, the types of joints involved.

Mechanical digestion in the mouth results from mastication. Food is manipulated by the tongue, ground by the teeth, and mixed with saliva. Mastication is accomplished by a coordinated activity of the tongue, mandible, muscles of the mandible, and temporomandibular joints. Innervated by the fifth cranial nerve, the trigeminal nerve, the muscles involved in mastication – masseter, temporalis and pterygoid open and close the mouth. The lateral pterygoid muscles depress the mandible, opening the mouth, while the medial pterygoid, temporalis, and masseter elevate the jaw, closing the mouth. The jawbone itself, controlled by the temporomandibular joint (TMJ) - one of the only synovial joints with an articular disc, makes a rotational movement of opening and closing of the mouth. During jaw movements, only the mandible moves in excursions. Other muscles helping in the process of mastication are the cheeks, lips and tongue. Both intrinsic and extrinsic muscles of the tongue participate in mastication. The tongue maneuvers and crushes some of the food by pressing it against the hard palate, and forming it into a bolus, forcing it back of the mouth for swallowing. The cheeks and lips keep the food between the upper and lower teeth. Teeth participate as follows: Incisors cut into food; cuspids tear and shred; premolars and molars crush and grind.

Resources:

Coleman, D. (Director). (2005). Anatomy for beginners: Lesson 3, Digestion. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Each gram of a carbohydrate produces about ... kilocalories.

   

A. 2.0
B. 4.0
C. 6.0
D. 8.0
E. 10.0

All of the following are pregnancy induced changes EXCEPT:

A.increased cardiac output
B.decreased gastrointestinal tract motility
C.increased tidal volume
D.decrease in respiratory reserve volumes
E.All of the above are pregnancy induced changes. 

Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide a cold water and chicken wings will satisfy such desires. You need to reach for your frosty beverage on the counter directly in front of you. Your starting point should be anatomical position. Specify the movements, muscles, bones, and joints involved in reaching for the glass and bringing it to your mouth.

The upper arm is moved by the muscles of the shoulder girdle; the lower arm is moved by muscles of the upper arm; and the fingers are moved by muscles of the lower arm. Raising the arm from the anatomic position to reach a glass on the table is a gliding movement at the synovial shoulder joint. This is extension and abduction. The bone of the upper arm – the humerus, articulates with the scapula at the shoulder joint. Muscles of the thorax and shoulder move the humerus: the deltoid contracts and pulls the deltoid tuberosity of the humerus, then the trapezius muscle further lifts the arm; teres major and latissimus dorsi contract pulling the intertubercular groove of the humerus. The shoulder ball-and-socket joint extends. Humerus articulates with radius and ulna at elbow joint. To extend the arm at the elbow joint, triceps brachii contracts, biceps brachii relaxes, to pull the tuberosity of the radius, and supinator muscle pulls the surface of the radius: This supinates the hinge synovial elbow joint. To reach the glass on the table in front, pronator teres and quadratus contract, and the hand executes a pronation movement: the palm moves from anterior to posterior facing position. Extensor digitorum contracts to extend the phalanges of the fingers. To grab the glass, thenar and hypothenar muscles contract to pull the metacarpals and phalanges that flex at the carpometacarpal ellipsoidal joints, which work quite similar to a ball-and-socket joint, allowing angular motion in two planes – along or across the length of an oval. The thumb moves in opposition to grasp the glass. To bring the glass to the mouth, while the metacarpals and phalanges remained flexed to hold the glass, to flex the arm at the elbow joint, biceps brachii contract and triceps brachii relax, while muscles of the thorax and shoulder move the humerus.

Resources:

Coleman, D. (Director). (2005). Anatomy for beginners: Lesson 3, Digestion. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

The meninges layer which is closest to the bone is called the ...

A. dura mater 
B. subarachnoid space
C. pia mater
D. paranoid mater

Match the following body system with its function

Match	Term	Definition
	integumentary system	A) supports and protects the body
	urinary system	B) protects the body, detects sensations, and helps regulate body temperature
	respiratory system	C) functions in body movement, posture, and heat production
	reproductive system	D) produces gametes that unite to form a new organism, releases hormones that regulate associated body processes, and produces milk
	digestive system	E) regulates body activities through hormones
	muscular system	F) transports oxygen, nutrients, and carbon dioxide
	nervous system	G) returns proteins and fluid to blood, carries lipids from the gastrointestinal tract to blood, and protects against disease-causing organisms
	lymphatic and immune system	H) transfers oxygen from inhaled air to blood and carbon dioxide from blood to expired air
	skeletal system	I) eliminates wastes and regulates the chemical composition and volume of blood
	endocrine system	J) regulates body activities through nerve impulses
	cardiovascular system	K) breaks down and absorbs food

Which of the following areas deals with emotions?

A. reticular activating system
B. thalamus
C. brain stem
D. limbic system 
E. cerebrum

All of the following are functions of the liver EXCEPT:

A. red blood cell production
B. storage of vitamins
C. synthesis of bile salts
D. excretion of bilirubin
E. activation of vitamin D 

You need to step up on a step to reach an object on a high shelf over your head. Your starting point should be anatomical position and your finishing point should be the position you are in once your hand has reached the object overhead. Specify the movements, muscles, bones, and joints involved in reaching up above your head to the object on the shelf. Explain any and all movements individually across each joint involved specifying the actions involved (i.e. flexion, extension, etc.), the muscles causing such actions, the bones being pulled on by said muscles, the types of joints involved, and how these movements collectively relate to the overall scenario/movements in this application.

The upper arm is moved by the muscles of the shoulder girdle; the lower arm is moved by muscles of the upper arm; the fingers are moved by muscles of the lower arm. Raising the arm above your head is gliding movement at the synovial shoulder joint. This is extension and abduction movement. The bone of the upper arm – the humerus, articulates with the scapula at the shoulder joint. Muscles of the thorax and shoulder move the humerus: the deltoid contracts and pulls the deltoid tuberosity of the humerus, then the trapezius muscle further lifts the arm; teres major and latissimus dorsi contract pulling the intertubercular groove of the humerus. The shoulder ball-and-socket joint extends. Humerus articulates with radius and ulna at elbow joint. To extend the arm at the elbow joint, triceps brachii contracts, biceps brachii relaxes, to pull the tuberosity of the radius, and supinator muscle pulls the surface of the radius: This supinates the hinge synovial elbow joint. Finally, to reach the object on the shelf, pronator teres and quadratus contract, and the hand executes a pronation movement: the palm moves from anterior to posterior facing position. Extensor digitorum contracts to extend the phalanges of the fingers.

Resources:

Coleman, D. (Director). (2005). Anatomy for beginners: The anatomy of movement. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc.

Match the following blood vessels with their function

Match	Term	Definition
	inferior vena cava	A) carries deoxygenated blood to the lungs
	pulmonary trunk	B) carries deoxygenated blood to the heart from the lower limbs
	coronary circulation	C) carries oxygenated blood to all systemic arteries
	aorta	D) carries oxygenated blood to the heart
	pulmonary vein	E) supplies blood to the cardiac muscle
	superior vena cava	F) carries deoxygenated blood to the heart from the head and upper body

You need to step up on a step to reach an object on a high shelf over your head. Your starting point should be anatomical position and your finishing point should be the position you are in once your hand has reached the object overhead. Specify the movements, muscles, bones, and joints involved in stepping up on the step. Explain any and all movements individually across each joint involved specifying the actions involved (i.e. flexion, extension, etc.), the muscles causing such actions, the bones being pulled on by said muscles, the types of joints involved, and how these movements collectively relate to the overall scenario/movements in this application.

Stepping up involves first flexing the leg at the hip and at the knee. The upper leg muscles are moved by muscles of the hip, buttock and abdominal cavity; the lower leg muscles are moved by muscles of upper leg; the foot muscles are moved by muscles of lower leg. The iliacus, fascia latae, and psoas major contract to flex the thigh at the hip joint, pulling the femur. The femur articulates with the acetabulum of the hip bone at the hip synovial ball-and-socket joint. This action conducts movement power to the sartorius that flexes the hip and knee, and hamstrings (extend the hip and flex the knee), which contract (while the antagonist quadriceps femoris relaxes) to flex the leg at the patella, which serves to move the power across the synovial knee joint to the lower leg, pulling the tibia and fibula. At this point, the patella tendon contracts to flex the tibia and fibula at the patella. Tibialis anterior executes dorsiflexion of the foot, and gastrocnemius contract to execute plantar flexion of the foot and flexion of knee. To place the foot on the step and lift the body weight onto the step, gluteus maximus extends and steadies the femur, while the hip ball-and-socket joint extends. To lift leg up onto the step flexion of hip, flexion at the knee, and dorsiflexion of the foot occur. To push up onto the step, extension of femur, extension at the knee, and plantar flexion of foot occur. To stabilize the femur into final position, gluteus maximus contracts.

Resources:

Coleman, D. (Director). (2005). Anatomy for beginners: The anatomy of movement. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Heart Beat

You need to step up on a step to reach an object on a high shelf over your head. Your starting point should be anatomical position and your finishing point should be the position you are in once your hand has reached the object overhead. What are the steps involved in the actual muscle fiber contraction – a.k.a. the Sliding filament theory.

Muscle contraction cannot occur without calcium ions and the ATP that provides energy. When the nerve impulse reaches the neuromuscular junction, it travels through the sarcolemma into the transverse tubule system, triggering the channels for calcium ions release to open: CA2+ enters into the sarcoplasm, binding the troponin molecules in the thin filaments of the muscle fiber. The troponim changes shape and moves tropomyosin away from the myosin-binding sites on actin, leaving them uncovered. The myosin heads also contain ATPase that splits ATP into ADP and P. This splitting process generates mechanical energy of motion to the myosin heads which in turn start acting like crossbridges, rotating, then detaching from actin and getting ready to bind again, acting like springs. This is the sliding process. In other words, when the level of calcium ions is high enough and there is enough ATP, the myosin heads of the thick filaments pull on the thin filaments inside the muscle fiber, and the thin filaments slide toward the center of a sarcomere, narrowing the I bands and H zones until they disappear. This is the moment of maximum contraction. The contraction goes on as long as there is enough calcium and ATP.

Resource:

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Botox has become a household name over the last few years. What are the medical and cosmetic uses of this pharmaceutical and how does it works

Botox is the commercial name given to injections with botulinum toxin type A, a toxin produced by a bacterium that causes the food poisoning botulism. However, when injected in small doses, botulinum toxin type A acts as muscle relaxant (Mayo Clinic, 2010). Botox is injected a very thin needle, in tiny amounts into the skin or muscles. The Botulinum toxins block the release of acetylcholine and cause chemical denervation of the muscles. With the acetylcholine receptors blocked, when a nerve signal comes for contraction, the muscle does not know it has to contract. The effect of the Botox injections can be noticed in five to ten days and it lasts two to six months, until the muscle develops new receptors and is able to contract again (eMedicine, 2009)

Botox comes in two forms: medical and cosmetic. The medical type was approved by the Food and Drug Administration (FDA) as treatment for cervical dystonia, strabismus, blepharospasm, upper limb spasticity, hyperhidrosis, and chronic migraine. The cosmetic type is used to reduce facial wrinkles by relaxing the muscles of the face. FDA has also approved the use of cosmetic Botox for temporarily treating frown lines between the eyebrows. However, Botox does not cure or reverse wrinkling, it is a temporary solution (Mayo Clinic, 2010, para. 2). The injections with Botox are relatively safe, but there are side effects, such as pain, itching and redness of the injected site, but also headache, nausea, temporary muscle weakness, an increase of body sweat, allergic reactions, and even botulism symptoms if the toxin spreads in other parts of the body (Mayo Clinic, 2010). 

Sources:
eMedicine (2009). Botox injections. Electronically retrieved from http://emedicine.medscape.com/article/1271380-overview
Mayo Clinic Staff (2010). Botox injections. Electronically retrieved from http://www.mayoclinic.com/health/botox/MY00078

Anatomy for Beginners, Lesson 1: The Anatomy of Movement, with Gunther von Hagens & John A. Lee

You need to step up on a step to reach an object on a high shelf over your head. Your starting point should be anatomical position and your finishing point should be the position you are in once your hand has reached the object overhead. Include the steps involved in transmitting the impulse “microscopically” through an individual neuron, from one neuron to another, and then from the neuron to the muscle fiber. Include the steps involved in transmitting the impulse “microscopically” through an individual neuron, from one neuron to another, and then from the neuron to the muscle fiber.

An action potential in a neuron is initialized in its axon hillock, along the axon and its terminals. The impulse is conducted through propagation. An action potential occurs when there is a stimulus, in this case the conscious thought of voluntary muscle movement. When the stimulus - conscious thought of the movement reaches threshold, the neuron’s membrane depolarizes: the gate for NA allowing the sodium to flow outside the cell, causing the membrane to reach a voltage of 30mV. At this point, an impulse is conducted through the axon plasma membrane. Then, the K gate opens, allowing the potassium inside the cell, repolarizing the cell: this is the end of the impulse, the neuron returns to its resting state.

The communication between two neurons occurs through the nerve action potential. The axon will conduct the impulse to the next neuron through releasing a neurotransmitter at its terminals, to the receiving dendrites of the neighboring neuron: This is where the synapse occurs. When the transmission occurred, the presynaptic neuron returns to its polarized state, and the postsynaptic one depolarizes to further conduct the impulse. The axon of the postsynaptic neuron conducts the action potential further through its terminals to the following cell, and so on. These axons are myelinated in order to coordinate fast, voluntary movements; therefore a saltatory conduction takes place: Impulses are saltatory conducted from the level of the nodes of Ranvier.

The plasma membranes of two neurons do not touch, as they are separated by the synaptic cleft. Because nerve impulses do not transmit through the synaptic cleft, the synapse between the two neurons happens when the depolarization opens the voltage-gated Ca2+ channels, allowing the calcium to flow into the synaptic end bulbs of the presynaptic neuron’s axon. As the calcium level increases, synaptic vesicles release neurotransmitter molecules into the synaptic cleft. These molecules diffuse and bind to the neurotransmitter receptors in the plasma membrane of the postsynaptic neuron. The process opens ion channels; when ions start flowing, voltage changes to create depolarization. When depolarization occurs, threshold is reached; the postsynaptic neuron generates a nerve impulse.

The final neuron in the row reaches the muscle. Since this is the last neuron, there is no postsynaptic neuron that follows it, so the synapse happens with the muscle fiber: this is the neuromuscular junction. Here, the neuron excites the muscle fiber that will contract. When the nerve impulse reaches the synaptic end bulbs, ACh is released and diffused into the synaptic cleft between the axon terminals of the neuron and the motor end plate of the muscle fiber. Sodium flows into the cell and generates a muscle action potential.

Resource:

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Circulatory System and the Heart

Spinal Nerve Function

Source: http://www.fletcherheights-chiro.com/spinal_nerve_function.html

Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide a cold water and chicken wings will satisfy such desires. You need to reach for your frosty beverage on the counter directly in front of you. Your starting point should be anatomical position. Trace the path of the water from the mouth to the urethra, listing the path in as much detail as possible. Be very specific and very detailed. Your answer should include both the digestive and renal systems.

The first step in the pathway of the water from the mouth to the urethra is the ingestion of the water, which happens in the mouth. After swallowing, the water goes down the pharynx and esophagus, to reach the stomach where it is mixed with the food and gastric juices. It then passes into the small intestine where it is absorbed. Diffusion of the water through the cell membrane occurs through osmosis. The water will diffuse into capillary blood, reaching the blood stream, traveling to the kidneys through the renal arteries. Here the optimal amount of water will be determined, and the excess will be discharged into urine. In the kidneys, nephrons will first perform glomerular filtration, during which blood pressure forces the water and solutes in the blood plasma through the wall of the glomerular capillaries, forming glomerular filtrate. As the filtered fluid flows through the renal tubules and collecting ducts, tubular reabsorption occurs. During this process, most of the filtered water returns into the blood stream. Tubular secretion also occurs, helping to eliminate waste and the excess of water, that is removed from the blood and transported into the fluid in the renal tubules and collecting ducts into the renal pelvis This water is now part of urine and will drain into ureters, travel into the urinary bladder to be stored in there until its volume exceeds 200 to 400mL. When this happens, pressure increases and micturition reflex is triggered, which will relax the urethral sphincter. Urine is expelled into the urethra through the process of micturition, or urination. 

What are the effects of tanning beds and natural sunlight on the skin. What factors contribute to the development of skin cancer? How can we protect ourselves from UV lights' harmful rays? How does "sunblock" work and does it pose any risks?

Exposure to sunlight is important in the synthesis of vitamin D. However, UV overdose has damaging effects on human skin, whether the source of UV is the sunlight or tanning beds. Ultraviolet rays speed up the skin’s aging process, affect the immune system, contribute to the development of infectious disease, and can lead to skin cancer, including melanoma (Gibson, 2010, para.1). Excessive UV radiation results in sunburn; damage to the epidermis can occur in two hours of sun exposure, resulting in erythema (eMedicine, 2010, para. 3). 


The most common type of cancer in the United States, the skin cancer, has as the most frequent cause the UV rays exposure, but also high X-rays levels exposure, contact with specific chemicals such as arsenic or hydrocarbons, or immunosuppression-impairment of the immune system. Heredity and environment also play a major role. The risk of skin cancer increases for people with fair skin (eMedicine, 2010). 

The best way to protect the body from UV rays is to stay out of the sun, especially during hot, summer days: reduce sun exposure, stay in shade as much as possible, cover the body, avoid tanning beds, check the skin regularly for moles, and use sunscreen with a high sun protection factor.

Sunscreen blocks the sun’s harmful UV rays, and it is therefore essential in reinforcing the skin’s protection. Recent studies indicate sunscreens with 1 to 6 percent oxybenzone do not presents any risks of skin irritation. The mineral-based sunscreens with ingredients of zinc oxide and titanium dioxide seem to also be safe and effective (Mayo Clinic, 2010, para 12-13). However, a Food and Drug Administration (FDA) report from 2007 shows there is no proof sunblock prevents skin cancer, recommending appropriate clothing as the best solution of avoiding UV rays exposure. The same FDA report suggest there is however sufficient evidence that sunblock might increase the risks of melanoma (Breyer, 2010, para. 5-6).


Sources:

Ambrose Video (2005). Body Atlas: Skin.

Breyer, M. (2010). Risks of sunscreen. Electronically retrieved from http://www.care2.com/greenliving/the-dangers-of-sunscreen-new-report.html#

eMedicine (2010). Skin cancer causes. Electronically retrieved from http://www.emedicinehealth.com/skin_cancer/page2_em.htm#Skin Cancer Causes

eMedicine (2010). Sunburn. Electronically retrieved from http://emedicine.medscape.com/article/773203-overview

Gibson, L. E. (2010). Are tanning beds safer than natural sunlight? Electronically retrieved from http://anna-hall.com/are-tanning-beds-safer-than-natural-sunlight-1-of-3/

Mayo Clinic Staff (2010). Best sunscreen: Understand sunscreen options. Electronically retrieved from http://www.mayoclinic.com/health/best-sunscreen/MY01350

You need to step up on a step to reach an object on a high shelf over your head. Your starting point should be anatomical position and your finishing point should be the position you are in once your hand has reached the object overhead. Trace the nerve impulse, listing the “macroscopic” structures and steps in as much detail as possible, from which your brain sends the message to the appropriate muscles to step up one step.

Stepping up one step is a conscious, voluntary muscular movement. Most of the command of such movement takes place in the CNS, with the exception of the final impulse from the spinal nerves to the muscle, which happens in the PNS. The conscious thought of the movement happens in the primary motor area, frontal lobe of the cerebral cortex, the part of the brain that allows conscious control of skeletal muscles. I am going to assume that the step up movement happens with the right leg, hence the motor cortex on the left side of the brain controls the muscles in case (right leg). When the movement decision occurs, the cerebellum takes charge and coordinates the movement ordered by the cortex. The thalamus transmits information from the cerebellum to the motor area of the cerebral cortex. At this point axons from the cerebellum and the cerebral cortex form synapses with the red nuclei in the midbrain of the brain stem to coordinate the muscular movement. The impulse passes through the cerebral peduncles of the midbrain, where axons of motor neurons further conduct the nerve impulse to the pons, then to the medulla oblongata’s white matter where the motor tracts extend into the spinal cord. The pathway of the impulse passes through the motor tract synapses with the large alpha motor neurons, located at the appropriate levels of the spinal cord, in the anterior horns of the spinal grey matter, which send impulses through the spinal nerves (we are now in the PNS) of the ventral root, where axons of somatic motor neurons conduct nerve impulses of contraction to the iliacus, fascia latae, and psoas major, which contract to flex the thigh/femur at the hip joint. Other muscles involved in stepping up a step are: sartorius (flexes the hip and the knee), the hamstrings (extend the hip and flex the knee), tibialis anterior (executes the dorsiflexion of the foot), gastrocnemius (executes plantar flexion of the foot and flexion of the knee), and gluteus maximus (extends and steadies the femur).

Resource:

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

Levels of structural organization in the human body as compared to the written language tools

1. The chemical level and letters – atoms and molecules can be compared to letters of the alphabet.

2. The cellular level and words – cells, the smallest living units in the human body can be compared with words, the smallest elements of language.

3. The tissue level and sentences – cells join together to form tissues similar to the way words are put together to form sentences.

4. The organ level and paragraphs – tissues join together to form organs similar to the way sentences are put together to form paragraphs.

5. The system level and chapters – organs join together to form systems similar to the way paragraphs are put together to form chapters.

6. The organism level and books – systems join together to form an organism similar to the way chapters are put together to form a book.

Tortora, G.J. and Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8^th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc.