Major Concepts in Anatomy and Physiology - Assignment Example

? ANATOMY AND PHYSIOLOGY - CONCEPTS goes here] [Your goes here] [Due the paper] Answer Part a The menstrual cycle occurs every month in women from the age of puberty till menopause. An ovarian cycle refers to the process in which a mature oocyte erupts from the ovary and moves down to the uterus. When fertilization occurs, the egg comes to the uterus where the development of embryo begins. The response of the ovarian cycle in case of fertilization is that the uterine lining becomes thick in anticipation of implantation of a fertilized egg. The uterine lining becomes thick because of progesterone secreted by corpus luteum that forms in the ovary. In case of fertilization, the egg is implanted in the uterine lining which consequently stops the menstruation cycle to occur again during the term of pregnancy. The ovarian cycle does not repeat if the oocyte becomes fertilized. After fertilization and conception, the process of embryo development starts which causes an end to the ovarian cycle all through the term of pregnancy. Part b On the other hand, a new oocyte matures during the next ovarian cycle if fertilization does not occur. The uterine lining also becomes thin and breaks down which causes menstruation to occur again. The egg which is released from the ovary needs approximately 12 to 48 hours to be fertilized. If fertilization does not occur, the egg disintegrates. After almost two weeks of this process, menstruation begins again upon shedding of the thick uterus lining. The lining of the uterus is there to support the pregnancy. However, when there is no fertilization, the lining breaks down and sheds in response of which the next cycle of menstruation begins. To state it all in more academic medical terms, one can say that after a couple of weeks approximately, the corpus luteum involutes if fertilization does not occur. This causes a significant drop in the level of progesterone which consequently causes bleeding from the endometrium. Answer 2 Part a The processes of primary spermatocytes and spermatogonium development mainly refer to spermatogenesis which is the process of sperm production from primordial germ cells (Shaw 2005, p. 209). A spermatogonium belongs to the cell family of male reproductive system. In lumen, the production of this type of cells take place in the process of which they pass through three main stages; the formation of Type A (p) spermatocytes, Type A (d) spermatocytes, and type B spermatocytes. The stem cells, known as Type A spermatogonia, divide to from A1 spematogonium and A2 spematogonium. The A1 spermatogonium divides itself, whereas the A2 spematogonium divides further to form A3 spematogonium which continues to form A4 spematogonia. The A4 spematogonia can form the intermediate spematogonium which can further divide mitotically to produce Type B spematogonia. The Type B spermatogonia undergo the last stage of mitotic cell division to form primary spermatocytes. Part b The production of primary spermatocytes does not stop; rather through meiotic cell division, it continues to produce the secondary spermatocytes (Tortora and Derrickson 2008, p. 99). The formation of secondary spematocytes is done as the first stage of meiosis division as the mitotic division ends with the formation of primary spermatocytes. Here, one point to be mentioned is that the first stage of meiosis does not transform the primary spermatocytes into a single spermatocyte, rather each primary spermaticyte yields a pair of secondary spermatocytes while completing the meiosis I division. The meiosis I division refers to reduction division as the homologous pairs of chromosomes are separated to produce haploid secondary spermatocytes. Part c The formation of two spermatids is the further division of each secondary spermatocyte (Tortora and Derrickson 2008, p. 99). When sister chromatids are separated in meiosis II process, a pair of spermatids are formed as a result. The spermatids are also known as haploid male gametids. An important point regarding spermatids is that through cytoplasmic bridges, the spermatids are connected to each other. Spermatids are formed in link with sertoli cells that play the role of nourishing the spermatids when they are in the process of turning into spermatozoa. As far as the presence of genetic material in spermatids is concerned, each of the spermatids consists of only fifty percent of primary spermatocyte’s genetic material. Part d The primordial germ cells staying at the cortical cords differentiate into oognia from sixth to eighth week of the process of embryonic development. The formation of oognia cells is also a process that involves mitosis division. The location of oognia cells is within primary follicles. Oognia pass through the phase of mitotic proliferation during ninth to twenty-second week of the process of embryonic development. The number of oognia cells keeps on multiplying throughout embryonic development and reaches millions by the fifth and sixth week. The mitotic division comes to an end when oognia start passing through the phase of meiosis and become oocytes. Part e As the result of meiosis I division, a secondary oocyte, as well as a primary oocyte are formed that consist of cytoplasm. Meiosis II starts only if fertilization occurs. When the secondary oocyte passes through the process of meiosis II, a second polar body and an ovum are formed and ejected from the ovary. During the second meiosis phase, a secondary oocyte is formed within a Graafian follicle as it has to wait for ovulation to occur. The Graafian follicle and the secondary oocyte are arrested in the second metaphase after which the development of corpus luteum occurs during menstruation’s luteal phase. Answer 3 Part a Neurons play a critical role in learning a behavior and storing memories. The formation or links neurons they make with each other to do these tasks are known as neural pathways (Tortora and Derrickson 2008). Also known as neural track, a neural pathway consists of neurons that connect one part of the nervous system to another. A monosynaptic or reflex pathway is one of the main and simplest types of neural pathways (Freudenrich n.d.). Neural pathways help in making body motion and reflexes possible. They are stored in the memory of a person and work accordingly to the set of stored instructions in every incident. Part b Being a part of sensory neurons, the sensory receptors receive information and connect it with the nervous system. Sensory receptors adapt quickly or slowly based on the need of humans to focus on some situation. For example, if the need is to eat something because of extreme hunger, the focus will be on the dish instead of light or environment. Therefore, the person will not care about whether it is low light or bright light. Whatever it will be, the sensory receptors of the person will adapt to it within no time. On the other hand, when a person does something rarely, the sensory receptors are not used to it, so they adapt a little slower. Part c The referred pain is the pain which is experienced at some place other than one where the injury or some other disease has occurred. For example, when the pain occurs in head or upper side of the face because of illness, it is known as referred pain. Referred pain plays a vital role in determining any particular disease or internal organ disorder. For example, high blood pressure has some particular symptoms which can help in diagnosing that a person is suffering from high blood pressure. Similarly, the referred pain experienced in the left side of the chest means that the actual problem is there in the cardiac area. Therefore, it can be said that the role of referred pain is critical in diagnosing diseases. Part d The long-lasting enhancement of synapses between neurons or nerve cells is referred as long-term potentiation. Long-term potentiation is used to understand and establish long-term memories, as well as in understanding the mechanisms of synaptic plasticity. The long-term potentiation causes the strength of memories to increase by strengthening the connections between nerve cells which consequently increases the time of memory retention in brain. This is why psychologists link long-term memories with the concept of long-term potentiation. However, along with its use in understanding memories, diseases, and synaptic plasticity, impairments and alterations in long-term potentiation also causes a number of diseases, such as, Alzheimer’s disease, Parkinson’s disease, and depression. Answer 4 Part a To sense a smell, the nose of a human contains millions of receptors within olfactory epithelium. The three main kinds of cells included in the olfactory epithelium include supporting cells, olfactory receptors, and basal cells. Olfactory receptors contain olfactory hairs that are used to respond to the chemicals inhaled through nose. To start olfactory response, olfactory receptors produce a generator potential to respond to a molecule’s chemical stimulation. As sensory receptors react to stimuli, olfactory receptors also respond to the molecules to continue the process of olfaction. When an olfactory receptor binds an odorant molecule with it, cyclic AMP is produced. The conscious awareness of smell starts in the primary olfactory area. Olfactory nerves are formed by the axons from the olfactory receptors. Within the olfactory bulb area, second-order neurons are present to form the olfactory tract. When the tract synapses on temporal lobe’s olfactory area, the smell’s awareness occurs. When other paths join the frontal lobe area, the chemicals in the orbi-frontal area identify the molecule linked with the olfactory hair as the result of which a nerve impulse arrives in the orbi-frontal area. Part b The axons of first-order gustatory neurons contained in the cranial nerves develop the taste buds (Clark 2005, p. 221). The mechanism is such that the dissolved substance establishes link with the gustatory hairs, whereas receptor potential releases neurotransmitter. To serve the taste buds, the facial nerve plays its role in the anterior two-third portion of tongue, whereas the glossopharyngeal nerve plays its role in the posterior one-third portion of tongue. Similarly, the vagus nerve plays its role in epiglottis and palate. The pathway is such that nerve impulses transmit themselves along the line with cranial nerves right upon to the gustatory nucleus that is present in the area known as medulla oblongata (Arnould-Taylor 1998, P. 53). Now what happens is that when impulses reach the gustatory nucleus, some of the taste signal axons find their way towards the thalamus and limbic system, whereas remaining axons move towards the hypothalamus. Here the pathway ends when the thalamus based taste signals present in the cerebral cortex’s parietal lobe make identification of taste possible. Part c The fibers from the nasal half of the retinas move in a way that they cross in optic chiasm. From the right side of objects, the left occipital lobe receives the images using impulses that come from temporal half of the left eye and nasal half of the right eye. The pathway for visual images is such that images come to the optic nerve through the retina. Then, the images travel to the optic chiasm from where they travel to the optic tract. Next, they arrive at the thalamus from where they reach the primary visual area of the cortex (Clark 2005, p. 200). The axons of the nasal half that belong to the retina make a cross at the optic chiasm where they continue travelling towards the other portion of the thalamus. After this, they move to the primary visual area of the cortex. This is the pathway through which nerve impulses reach the cortex. Part d The pathway for auditory impulses from the cochlea to the cerebral cortex is such that the cochlear branch of the region CN VIII transmits the received auditory signals to superior olivary nuclie and cochlear nuclie that reside in the medulla oblongata area (Clark 2005). Here an important point to mention is that there are some differences in the arrival of auditory impulses that play their role in identifying the original source of the incoming sound. After arrival of impulses to the cochlear and olibary nuclie, the fibers mount to the medulla oblongata where a large portion of impulses cross each other and move to opposite sides to continue travelling towards the midbrain region. From there, the impulses continue moving towards the thalamus region from where they make a shift towards the temporal lobe’s auditory area or cerebral cortex region. This is the pathway using which auditory impulses from cochlea reach the cerebral cortex. Answer 5 Mechanism and Function of a Stretch Reflex When a muscle is stretched, the stretching within the muscle causes the large skeletal muscle fibers to contract. The stretch reflex plays a vital role in regulating the length of the skeletal muscle. In every muscle, there are a group of cells known as spindle muscles that awake whenever a muscle is stretched. They start functioning in a way that when a muscle is stretched, spindles also begin to stretch in response causing the muscles to contract. The length of the intrafusal muscles gets short upon contraction of skeletal muscles which results in decreasing the pressure on muscle spindles. The main function of a stretch reflex is that it sends a signal to the central nervous system of the spinal cord about changes in the length of muscle spindle to maintain the structure and posture of the body. The stretch reflex also plays a considerable role in protecting the posture of the body when the muscles of the skeletal system are being stretched (Thies and Barron 1995, p. 49). Mechanism and Function of a Tendon Reflex Tendon reflex works in a way that relaxations are brought to muscles before the strength of muscle force becomes strong enough to pose a risk for tendons (Thies and Barron 1995, p. 49). Medical science has proved that strong muscle force or exertion of muscles causes more risk of damage for tendons. Tendon reflexes provide relaxation to muscle fibers so that the tendons do not break due to high exertions that often occur in sports and field jobs. The main functions of a tendon reflex are to avoid strong contractions of muscles, to diagnose the neuromuscular disease, to test the condition of the spinal cord, to protect the tendon that may damage due to contractions, and to spread workload evenly on muscles. The stretching of muscles has deep association with tendon reflex. Quick movements cause quick stretching of muscles which put the tendon at risk. The tendon reflex helps in protecting the tendons in quick movements, as well as in case of strong muscle contractions. Mechanism and Function of a Flexor Reflex Also known as withdrawal reflex, a flexor reflex is activated by a cutaneous sensory stimulus that results in withdrawal of a limb by activating the flexor muscles . In muscles, tendons and tissues are present which help in functioning of the muscles in a proper manner (Thies and Barron 1995, p. 49). Flexor muscles protect the tendons and tissues from damaging in case of exertions and high muscle work. The cutaneous sensory muscles cause contraction in the limb’s flexor muscles which causes the limb’s withdrawal from the stimulating object. For example, a painful stimulus to hand usually causes contraction in the upper arm’s flexor muscles causing withdrawal of painful stimulus from the hand. Stimulations of pain endings and touch receptors elicit flexor reflex. Wounds usually cause prolonged flexor reflexes, whereas touch receptors cause less prolonged reflexes. The main functions of a flexor reflex include providing protection from damaging stimuli, causing stimulation of motor and sensory neurons, and activating the flexor muscles. Mechanism and Function of a Crossed Extensor Reflex A crossed extensor reflex is also a withdrawal reflex and relates to flexor reflex in that when a danger stimulus results in activating a flexor reflex on one leg to withdraw the contract in some stressful situation, the crossed extensor reflex activates an extension reflex on the opposite leg in order to maintain the balance of the body. This reflex is also known as a contralateral reflex because with every flexor reflex, it occurs on the opposite side of the body to maintain the balance. This happens when afferent nerves’ branches shift towards the contralateral side of the spinal cord from the stimulated side to transfer alpha motor neurons to the contralateral side’s muscles by synapsing with interneurons. The main functions of crossed extensor reflex are to maintain the balance of the body when reflex occurs, to distribute weight to the opposite side, and to maintain body weight when withdrawing an affected body part from stimulus. References Arnould-Taylor, W 1998, A Textbook of Anatomy and Physiology, 3rd edn, Stanley Thornes Publishers, London. Clark, R 2005, Anatomy and Physiology: Understanding the Human Body, Jones and Bartlett Publishers, Sudbury. Freudenrich, C n.d., How Nerves Work, viewed 2nd October 2013, http://science.howstuffworks.com/life/human-biology/nerve2.htm Shaw, L 2005, Anatomy and Physiology, Nelson Thornes Ltd., Cheltenham. Thies, R & Barron, K 1995, Physiology, 4th edn, Springer-Verlag, New York. Tortora, G & Derrickson, B 2008, Principles of Anatomy and Physiology, 12 edn, John Wiley and Sons, New York. Read More