Wednesday, April 8 Lecture

Wednesday’s lecture covered several topics of the cardiovascular system. We covered arteries (which carry blood away from the heart) and veins (which carry blood towards heart). Capillaries exchange carbon dioxide and oxygen and wastes and nutrients. Portal systems are two capillary networks, in which the first exchanges substances and the second exchanges wastes and gases. We also discussed the layers of blood vessels such as the tunica externa, tunica media, and tunica interna. The remainder of the class comprised of learning the locations of various important blood vessels. We covered such topics as the blood flow to and from the brain, the coronary circuit, the pulmonary circuit, the blood vessels of the thorax, the branches of the abdominal aorta, and the blood flow to the lower extremities.

The topic of anatomical redundancy explains how there are multiple blood routes to major organs. This allows for blood to remain flowing to the specific organ in case there is a blockage in one of the routes. For example blood to the brain is delivered via the vertebral arteries through the subclavian arteries as well as the internal carotid artery from the common carotid arteries. I wondered if, because of this dual-pathway of blood to the brain, if a slight blockage could occur in one of the pathways and a person could continue living as normal. Also, if a slight blockage would occur, could the other path have more blood pumped through it to make up the difference? With the help of Ms. Peterson and a few web sources I found that this in fact could happen. As we know there are two routes leading into the Circle of Willis. In fact, “as long as the Circle of Willis can maintain blood pressure at fifty percent of normal, no infarction or death of tissue will occur in an area where a blockage exists.” “Sometimes, an adjustment time is required before collateral circulation can reach a level that supports normal functioning; the communicating arteries will enlarge as blood flow through them increases. In such cases, a transient ischemic attack may occur, meaning that parts of the brain are temporarily deprived of oxygen.” I found it quite interesting that the body can make such adjustments, even in such a critical area such as the brain.

Wednesday, March 25, 2009 Lecture

Wednesday’s lecture covered the cardiovascular system. We discussed the elements that blood is comprised of, covering the structure of an erythrocyte (red blood cell) and the various leukocytes (white blood cells) (i.e. neutrophil, eosinophil, basophil, lymphocytes, and monocytes). We also covered how to identify different leukocytes from one another and the functions of several of them. Red Blood Cells and White Blood Cells are both formed in the red bone marrow of the proximal epiphysis of long bones in adults. The structure of a RBC and the recycling of its parts were also covered. The process of blood clotting was overviewed, including the importance of clotting factor X and fibrinogen, which turns into solid fibrin and makes a web-like mesh to trap elements that form a clot. We covered the various blood types, the compatibility of blood types, and the anti-bodies each blood type has. The Rh factor was discussed as well as the importance of Rhogam shots for pregnant women. Finally, we studied heart models to determine the flow of blood in and out of the human heart.

Blood, a liquid connective tissue, is not only the most critical fluid in our body, but can also reveal disorders our body may have. The study and counting of different blood elements can indicate several disorders. A hematocrit shows the percentage of red blood cells in the blood, a low hematocrit can indicate anemia, while a high hematocrit can indicate dehydration or polycthemia (a bone marrow disorder). A high white blood cell count could indicate infection, inflammation, allergy, or stress. A low white blood cell count (leucopenia) could indicate infection or even cancer. A CBC, or complete blood count, performed by a medical specialist can evaluate both your white blood count (WBC) and red blood count (RBC) to determine and bodily disorders.

Wednesday, March 11, 2009

Wednesday’s class covered the material that will be on our next quiz—information over the endocrine system and autonomic nervous systems. We discussed the Adrenal glands, the medulla and cortex, as well as the hormones each releases and the location from which they’re released. We also covered the thyroid glands and how follicular, parafollicular, and colloid cells come into play. The follicular cells produce T3 and T4 (Thyroxine) from molecules of “DIT” and “MIT.” Thyroxine affects our BMR, or, basal metabolic rate. We also discussed the different tracts that luteinizing hormone takes in males versus females, starting from the hypothalamus. Our discussion also covered the parasympathetic and sympathetic nervous systems. We talked about the cranial nerves that have parasympathetic fibers and also discussed the pre/post-ganglionic fibers of the sympathetic nervous system and the different neurotransmitters that can be released. Lastly, we discussed the pathway of the cAMP/PKA secondary messenger system pathway.

Thyroxine, which is released by the thyroid gland, plays a major role in the regulation of your metabolism. Too much thyroxine (hyperthyroidism) can result in weight loss, nervousness, and/or anxiety and too little thyroxine (hypothyroidism) can result in sluggishness and weight gain. In order to treat both disorders doctors use prescribed medication. In the case of hyperthyroidism, too much T3/T4 is being produced, thus, a medication called an anti-thyroid drug is taken, which blocks the release of some thyroxine. Smaller amounts of thyroxine are still produced, but in much smaller quantities than before. In hypothyroidism, individuals are prescribed synthetic, man-made thyroxine, which mimics the effects of the natural hormone. In both cases it is common for the individual to be on these medications for life (in some hypothyroidism cases, however, individuals can regain thyroid function).

Wednesday, March 4, 2009

During Wednesday’s class we learnt about the endocrine system. We discussed the endocrine glands that release hormones into our blood streams, alter bodily functions and maintain homeostasis. The glands that create hormones include the pineal, hypothalamus, anterior pituitary, thyroid gland, parathyroid glands, thymus, and pancreas. We learnt about the anterior and posterior pituitary and how releasing hormones from the hypothalamus allow the release of anterior pituitary hormones through the hypothalamo-hypophyseal portal system. Oxytocin and Anti-Diuretic Hormone are two hormones made in nuclei in the hypothalamus and are transported into the posterior pituitary for storage via the hypothamo-hypophyseal tract. The two major types of hormones are protein hormones and steroid hormones. Although steroid hormones are slower to affect their target organs they have longer-lasting effects. Protein steroids, however, are more easily maneuvered.

As can be imagined, hormones play a critical role in the development of our bodies. Growth hormone, released by the anterior pituitary, is a hormone that allows our bodies to grow—especially during puberty. In class we discussed how dwarfism can be caused by a growth hormone deficiency. However, aside from synthetic growth hormone, what other methods can be performed to aid in the lives of dwarfs? The child of one of my parent’s relatives is a dwarf and is about 18 years old now. A year or so after I met him (which was about 5 years ago) he was to undergo surgery on his spine to increase his height and prevent scoliosis or kyphosis (abnormal curvatures of the spine). I researched the surgery and found that many dwarfs have problems with their spines that can become crippling. In order to prevent this from happening doctors fuse certain vertebrae of the spine together and place metal rods along the spine for stability. This straightens the spine during the healing process. After the vertebrae are fused the spine can no longer bend (or is limited in its bending ability). This prevents scoliosis or kyphosis from developing. During the healing process they must also wear a “halo” around their heads to prevent their necks from moving before the spine is healed. Not only does the surgery prevent the crippling of the spine, but it can also add a few inches to the individual’s height, as it did with the person I know.

Wednesday, February 25, 2009 Lecture

The lecture focused mainly on the autonomic nervous system and touched upon other topics such as secondary messenger systems and the major anatomical landmarks of the eye and ear. All impulses of the autonomic nervous system are efferent impulses. The two major divisions of the autonomic nervous system are the parasympathetic (cranio-sacral) and the sympathetic (thoraco-lumbar) systems. The parasympathetic system is responsible for the “Rest and Digest” reflex and is the restorer of homeostasis. The sympathetic nervous system is responsible for the “Fight or Flight” response. Both systems target smooth muscle, cardiac muscle, and glands. There are two neurons involved in the parasympathetic and sympathetic nervous systems: the pre-ganglionic neuron and post-ganglionic neuron. They are named this because they are before or after a ganglion, or bundle or nerve fibers. The pre-ganglionic neuron always releases Ach and excites the second neuron. The receptors that lie in the post-ganglionic neuron and target cell are cholinergic receptors. Cholinergic receptors include muscarinic (excitatory or inhibitory) and nicotinic (excitatory) and bind to acetylcholine. Another type of receptors is Adrenergic Receptors, which include Alpha 1, Alpha 2, Beta 1, and Beta 2 receptors, each affecting their target organs in different ways. Adrenergic receptors bind to epinephrine and norepinephrine. Secondary Messenger pathways utilize G-proteins to “carry” their message from the receptor to the channels located elsewhere in the cell. There are two different pathways in secondary messenger systems: pKA and pKC.

We also studied the major landmarks of the external, middle, and inner ear.

I’m sure all of us have either had an ear infection or known someone who has had one. If you’ve experienced one yourself you know that it causes a dull pain and can last several days or weeks. I researched exactly what causes an ear infection and found out that it is typically an infection of the middle ear (where the malleus, incus, stapes, pharyngotympanic tube, and the tympanic membrane are located). Middle ear infections are caused by the swelling of the pharyngotympanic tube (which connects the pharynx and the middle ear). This swelling can lead to a blockage of the tube, which traps fluid inside your middle ear where germs and bacteria cause an infection. Ear infections are more typical amongst children because their Eustachian tube is smaller and more easily blocked. Antibiotics can treat the infection.

Wednesday, February 11, 2009 Lecture

After our test over the CNS, the lecture consisted of learning about the remaining cranial nerves and then an introduction into the peripheral nervous system. 3 important terms that pertain to our senses include: smell=olfaction, hearing=auditory, taste=gustation. The cranial nerves are ordered by roman numerals from the anterior to the posterior part of the base of the brain. They include: I olfactory, II optic, III oculomotor, IV trochlear, V Trigeminal, VI Abducens, VII Facial, VIII Vestibulocochlear, IX Glossopharyngeal, X Vagus, XI Accessory, XII Hypoglossal. We learnt the entry and exit points of each nerve through the skull, as well as the function of the nerve. It is important to note that sensory nerves are afferent nerves (toward the brain) and motor nerves are efferent (away from the brain). There are also mixed cranial nerves that have sensory, motor, and/or autonomic functions. If cranial nerves are mixed and have autonomic fibers, they are always parasympathetic axons. Our brief introduction to the Autonomic Nervous System described the parts of the neuron that lead from the CNS to the target. (Nerves from the ventral horns of the spinal cord deal with motor impulses.) Between the CNS and the target there are always TWO NEURONS. There is a ganglion (bundle of fibers) that stretches to the target cell. The first neuron is the preganglionic neuron and the second is the postganglionic neuron. The parasympathetic system has 3 types of targets: smooth muscle, cardiac muscle, and glands. There are also two types of receptors on the dendrites of the neurons. 1) nicotinic receptors: which increase the level of activity, cause target to be excited, and 2)muscarinic: cause an inhibatory effect on target. The first neuron from the CNS always releases the excitatory neurotransmitter acetylcholine ACh, therefore the dendrites on the postganglionic must be nicotinic. The action potential from the postganglionic neuron will then determine the effect on the target.
The majority of people today have to get their wisdom teeth (third molars) extracted to avoid their teeth from becoming impacted. If you have had your wisdom teeth taken out you know that your jaw and lips are numb for quite some time following the procedure. I researched the nerves involved in the extraction of wisdom teeth and found that they numb the lingual nerve, which branches off of the mandibular nerve of the trigeminal nerve (cranial nerve V3). This nerve provides sensation for the lower lip, teeth and gums. The maxillary branch (V2) of the Trigeminal (V) nerve provides sensation to the superior lip, teeth, and gums. To quote a site which explained the procedure of numbing nerves, "In regional anesthesia, a numbing medication is injected around the nerves that transmit pain signals from the area involved in the surgery. The procedure “blocks” the nerves, ensuring that you will not feel pain during or immediately after surgery."

Wednesday, February 4, 2009 Lecture

During Wednesday's class we focused mainly on the Central Nervous System. We discussed the Meninges (coverings) on the brain, which include 3 distinct layers: the dura, arachnoid, and pia mater. We also learnt about the production of cerebrospinal fluid (CSF) and the flow of CSF throughout the ventricles of the brian and the spinal cord. In addition to CSF, we also discussed the flow of blood to and from the brain, and key facts about the blood flow, such as the anatomical redundancy (that creates a "back-up" flow blood to the brain in case of injury, trauma, etc. The major areas of the brain, the lobes, and their functions were also learnt. Lastly, we discussed seven of the twelve cranial nerves, including the three sensory nerves: I olfactory, II optic, and VIII vestibulocochlear; and four of the motor nerves: III oculomotor, IV trochlear, VI abducens, and XI accessory. We discussed the functions of these 7 cranial nerves, as well as their exit points through the skull.
One disorder that has always been confusing to me is that of blindness. If I were to pick one sense or function to keep over anything else, it would be vision. After our discussion of the optic nerve, one of the twelve cranial nerves, I researched what exactly causes blindness. Although blindness may be caused by such diseases as diabetes or malfunctioning of the retina, one reason it may occur is because of damage to, or the malfuncitoning of, the optic nerve. If the nerve does not develop correctly, blindness may develop from birth, however, one may also become blind if the optic nerve is damaged through trauma.