Human Biological Science - Coursework Example

Human Biological Science (Coordination and Control) By 19 February Human Biological Science (Coordination and Control) TAQ1: Differentiate the parts of the nervous system Brain and Spinal cord. The brain is the central organ of the nervous system and it is divided into several parts each with distinct functions (Farabee, 2010). The cerebrum controls thought and it is the centre of intelligence. Selected regions of the cerebrum control speech, hearing, and memory, learning motor and sensory areas. The cerebral cortex controls reasoning, language and language processes. Other parts of the brain such as cerebellum and medulla control movement and involuntary processes (heart rate, breathing and swallowing) respectively (Farabee, 2010). The spinal cord extends from the medulla running down to the second lumbar. The spinal cord is a pathway of nerves that connects the brain to the rest of the body. While afferent neurons join the spinal cord from other parts of the body, efferent neurons branch off from it to their target areas. Autonomic nervous system This component of the nervous system comprises of sensory and motor neurons that control the automatic functions of the body. These functions include heart rate, contraction and relaxation of smooth muscles and glands. Automatic functions can be further subdivided into “fight-or-flight” and the “resting and digesting system” responses. The fight-or-flight responses are responsible for reflex responses, some of which are coordinated by the reflex arc of the spinal cord. Somatic nervous system (Farabee, 2010) This is the component of the nervous system that controls contraction and relaxation of voluntary skeletal muscles and responses. Neurons of the somatic nervous system, therefore, control and coordinate movement of the limbs and other appendages such as eye lids. The somatic nervous system can be divided into twelve cranial nerves that innervate the head and thirty one spinal nerves that control impulses to rest body parts (Farabee, 2010). TAQ 2: Describe and Outline the function of each types of neurone Motor neuron Source: (Biologymad 2004). The motor neuron has multiple short dendrites and a characteristic long axon extending from the cell body to the effector cells. The axon is covered by a layer of myelin sheath along its length except at the axon terminals and nodes of Ranvier. The dendrites connect the motor neuron to other neurons and act as the entry point of nerve impulses. Motor neurons conduct electrical impulses from other neurons to effector cells. Depending on the nature of the target cell, nerve impulses at axon terminals of motor neuron can cause muscle contraction or glandular secretion (Biologymad 2004). Sensory neuron Source: (Biologymad 2004). The sensory neuron has an axon that branches after leaving the cell body into the peripheral branch and central branch. The peripheral branch conducts nerve impulse from a receptor cell to the cell body, while the central branch transmits the impulse to the spinal cord and brain. Relay neuron (Interneuron) Source: (Biologymad 2004). The interneuron or relay neurons are short nerve fibres characterised profusely branched dendrites and a single long axon that branches laterally at its terminus. The dendrites interconnect dendrites of several hundred other neurons forming a network of fibres (Biologymad 2004). TAQ 3: Explain the process of nerve impulse initiation and transmission Neurons have a cell membrane which is polarized when the cell is in a resting state. The cell is a resting state when there is no action potential across its membrane. In this state, the net charge inside its membrane is negative and positive on the outside (Lodish, Berk, & Zipursky et al., 2000). The difference in ionic charge is caused by high potassium ion concentration inside the cell and an equal concentration of sodium ions on the outer membrane. The resting potential is the difference across the cell membrane of a neuron when it is in a resting state. This potential difference is maintained by active pumping of sodium ions and potassium ions cross the membrane by the sodium/potassium pumps. A stimulus on the dendrite of a neuron triggers an inside diffusion of sodium ions as a result of sudden opening of the gated ion channels. Consequently the neuron becomes depolarized as more sodium ions enter the membrane till a threshold level is reached. Depolarization beyond the threshold level causes further opening of more sodium channels along the axon of a neuron leading to generation and transmission of a nerve impulse (Lodish, Berk, & Zipursky et al., 2000). Outward movement of potassium ions after a depolarization state causes a temporary repolarisation as the electrical charge is balanced. The diffusion of potassium ions outside the membrane occurs when potassium channels (inside the membrane) open and sodium channels (outside the membrane close) (Lodish, Berk, & Zipursky et al., 2000). Excess potassium ions on the outer membrane causes a hyperpolarisation state as the membrane potential slightly drops lower than the resting potential. After the hyperpolarisation state, the neurone enters the refractory phase where sodium ions are pumped out while potassium ions are pumped back into the cell by sodium/potassium channels. During this period, the neuron becomes inert and does not respond to any stimulus until the resting potential is restored. Synapse A synapse is the junction connecting two or more neurons and allows successive transmission of a nerve impulse to other neurons or the target cell. Synapse is the means by which neurons form networks of fibres that allow rapid transmission of nerve signals cross different nerve networks. Synapse connecting two dendrites of neurons are referred to as electric impulses while those connecting an axon terminal of a neurone to a dendrite of another neuron or target cell are referred as chemical synapse (Lodish, Berk, & Zipursky et al., 2000). Chemical synaptic junctions have synaptic knobs filled with mitochondrion organelles and vesicles containing the neurotransmitter substances. The pre-synaptic membrane and postsynaptic membrane are separated by a synaptic cleft. When an action potential along an axon reaches a chemical synapse, it triggers the release of a neurotransmitter substance (Lodish, Berk, & Zipursky et al., 2000). The release of the neurotransmitter is mediated by the activation of voltage gated calcium channels. Rapid inflow of calcium ions triggers a fusion of the synaptic vesicles to the synaptic membrane leading to the release of neurotransmitter substance. The released chemical substance diffuses across the synaptic cleft into the post-synaptic membrane of another neuron or target cell (Lodish, Berk, & Zipursky et al., 2000). The neurotransmitter binds to receptors located on the post-synaptic membrane and either initiate an electrical response or activate a messenger pathway in the postsynaptic neuron. Diagram showing the components of a synapse Source: (RSC n.d.). The electrical synapse on the other hand, is a junction that allows the transmission of electrical impulses from one neuron to the other. The pre-synaptic membrane is connected to the post-synaptic membrane by special gap junction channels. These channels can pass electric current that alters the potential difference in the pre-synaptic and post synaptic plasma membranes. Electrical synapse, due to their simplicity conduct signals rapidly compared to chemical synapse junctions, which have complex signal transduction mechanisms (Lodish, Berk, & Zipursky et al., 2000). TAQ 4 Diagram showing components of a Reflex Arc Source: (Anonymous n.d.) The reflex arc is a simple circuit of inter-connected nerves. The arc is characterised by interneurons connecting one or several motor and sensory nerves. These circuits allow the input from one sensory neuron to be transmitted into several motor neurons needed for a particular response (Anonymous n.d). In a reflex arc the sensory neuron carries the impulse from a receptor to the central nervous system. The impulse is the transferred to the motor neuron which transmits it to the target cell. The sensory neuron enters the spinal cord through the dorsal ganglion and connects to a relay neuron through dendrites. The cell body of the motor neuron is located in the spinal cord where the dendrites connect to other neurons. The interneurons ensure correct integration of sensory and motor neurons in such a way that a message is only transmitted to the affected organs (Anonymous n.d). TAQ 5: Locate the major endocrine organs and outline some of their functions Name of endocrine gland Location Hormones released Function(s) of Hormones released Pituitary Base of the Brain -Follicle-stimulating hormone (FSH) -Luteinizing hormone(LH) The hormones released in the gland are out of command by the hypothalamus. The hormones released control vital endocrine functions. The FSH leads to growth and maturation of follicle in the woman ovaries (Carter 2014). On the other hand, the LH enhances the breakdown of the follicle and development of the corpus luteum (Carter 2014) Thyroid In front of the neck -Thyroxine hormones -Triiodothyronine The hormone plays a significant role in body metabolism they regulate metabolism and thus body temperature and weight (Carter 2014). Parathyroids Posterior to thyroid Parathyroid hormone The hormone is responsible for regulating the amount of calcium in the blood (Carter 2014). Thymus Upper Chest region Thymosin The hormone helps the body in resisting some of the infections (Carter 2014). Adrenal On top of kidney - Epinephrine - corticosteroids Epinephrine helps the body to respond to stressors (Carter 2014). The stressor may be fright, anger, caffeine, or reduced amount of sugar in the body. On the other hand, corticosteroids help in the immune process such as responding to inflammation (Carter 2014). Pancreas The Upper abdomen Insulin and Glucagon The two hormones play a significant role in homeostasis. In the body, the hormones help in regulating the blood sugar level. As a result, there is maintenance of normal environment in the body. The hormones raise or lower blood sugar level to maintain a stable internal environment (Carter 2014). Ovaries Lower abdomen Oestrogen and Progesterone The hormones control the fertilization process and maintenance of female characteristics (Carter 2014). Testis The Scrotal sac Androgens The hormone Plays a role in determining male characteristics (Carter 2014). TAQ 6 Explain the effects of specific hormones on metabolism Metabolism is a biological process that maintains proper functioning of all body organs and systems. Metabolic processes are regulated by several mechanisms such as hormone and enzymes in order to achieve efficiency (UNIT V, n.d). Insulin and glucagon are essential hormones in the body that regulate the catabolism and anabolism of glucose, a vital source of energy (UNIT V n.d.). The hormones are released by the pancreas, an endocrine gland located in the abdomen under the regulation of catecholamine, epinephrine and nor-epinephrine hormones. Dietary carbohydrates are digested in the intestine into glucose and other monosaccharide that are absorbed in the blood stream. Increase in blood glucose level triggers the secretion of insulin which enhances the uptake of glucose by the liver and body tissues. Glucose inside the cells is catabolised to release energy in the form of Adenosine Tri-phosphate (ATP) (UNIT V, n.d). Excess of glucose is converted by the liver into glycogen, a storage form of glucose, which is converted back to glucose during starvation. The action of insulin is thus to regulate blood glucose levels and an abnormality with the production or utilization of insulin leads to a medical condition called diabetes. Glucagon is a counter hormone and down-regulates the effects of insulin on glucose and glycogen. Glucagon is produced by the same endocrine organ as insulin and is secreted when blood glucose level are below a certain threshold. Glucagon stimulates the liver to initiate a catabolic process of glycogenolysis and a subsequent anabolic process of gluconeogenesis. The overall effect is the restoration of blood glucose levels to normal (UNIT V, n.d). Thyroid hormones T3 and T4 also play a significant role in general body metabolism (Bowen 2010). The two hormones are secreted by the thyroid gland and carry out a myriad of metabolic function in most tissues that result in an increase in the basal metabolic rate, protein synthesis and bone growth. The effects of increased metabolic rate include a rise in body temperature and level of alertness. The two hormones also increase and promote cellular differentiation and development. The hormones also regulate the metabolism of carbohydrates, lipid and proteins (Bowen 2010). The hormones through their effect on fat play a vital role in reducing the amount of cholesterol in the body. Apart from increasing lipid metabolism they enhance glucose metabolism by having an insulin-like effect on the absorption of glucose in some tissues (Bowen 2010). The hormones also lead to increased gluconeogenesis and glycogenolysis. The metabolic regulatory role played by these hormones partly explains their effect on proper development and growth seen in individual to normal thyroid glands. Their regulatory role extends to vitamin metabolism, where it affects their absorption and utilization in the body (Bowen 2010). TAQ 7 Describe and explain the structure and functions of sensory organs The sensory organs are well developed and complex in higher animals than in other organisms (Leavingbio n.d.). These senses are mediated through sensory organs that are still integral parts of the nervous system. These sensory organs are receptors that convert external stimuli into nerve impulses that are transmitted to the brain and spinal cord for processing and interpretation. This essay will highlight the structure and function of two sensory organs (eye and ear) responsible for sight and hearing senses. The eye is big and complex sensory organ with different parts each contributing significantly to the overall function. The first principal component is the sclera, which is a tough outer layer that offers protection to delicate parts and also provides supports of the eye (Leavingbio n.d.). The shape of the eye is maintained in collaboration with the internal fluid pressure of a fluid chamber called humour. The conjunctiva is thin, clear layer that covers the frontal area of the eye continuously with inner eyelids (Leavingbio n.d.). The conjunctiva is lubricated with mucus that also aids eye movement by easing out friction. The layer of conjunctiva also acts as a barrier layer, for microbes and other pathogens thus serving an immune function. Cornea is the transparent region in the eye has a fundamental role focusing light towards the retina, which is at the rare of the eye (Leavingbio n.d.). The transparency in this area is maintained by lack of blood vessels in the region. Thus, cornea is nourished by the movement of tears. Posterior to the cornea is the iris, which is on the anterior end of the lens (Leavingbio n.d.). The fundamental role of the iris is to regulate the aperture of the pupil. This is achieved by a series of contraction and expansion of its muscle fibres. This regulation is controlled by the amount of light entering the eye, with more and bright light triggering a contraction than dim light. Pigmentation in this area confers the colour of the eye, which varies among races and individuals. The pupil is another fundamental part of the eye, which is an aperture that allows light to pass through to the retina. (Leavingbio n.d.). Smooth muscles in this area help in controlling the size of the pupil, which may vary among individuals. The ciliary body is a muscle that helps in controlling the shape of the lens thus aid in light focusing (Leavingbio n.d.). These muscles are also attached to ligaments and helps in transferring the pull of the ciliary body to the lens (Leavingbio n.d.). The retina is the light receptor of the eye and generates nerve impulses when light falls on its sensory bulbs (Leavingbio n.d.). On the other hand, the fovea helps in detailed coloured vision while choroid prevent internal reflection of light (Leavingbio n.d.). The eye is narrated by optic nerve located on the posterior end of the eye (Leavingbio n.d.). The other pertinent portion is the blind spot. The region acts as an exit point for the optic nerves and lacks the light sensors. The ear has the same level of complexity as the eye and serves the essential functions of hearing and attaining body balance (Leavingbio n.d.). The hearing response is processed through vibrations, their pitch and loudness, which are transformed into nerve impulses and carried to the brain (Leavingbio n.d.). The ear is subdivided into three parts, which are the outer, middle, and inner ear each with various parts that serve different functions (Leavingbio n.d.). The outer ear mainly comprises the pinna, whose main function is to collect sound waves and transmit them into the external auditory canal (Leavingbio n.d.). The auditory canal is a hollow tube that helps in carrying sound vibrations to the eardrum on the middle ear (Leavingbio n.d.). Sound waves transmitted by the ear drum are amplified by the ossicles, which are tiny bones whose function is to amplify the vibrations of the eardrum to the inner ear (Leavingbio n.d.). The Eustachian tube extends from the ear to the throat and helps in equalizing air pressure on both sides of the eardrum (Leavingbio n.d.). The oval window section allows transfer of vibration from middle to the inner ear while the round window minimizes pressure changes in the ear (Leavingbio n.d.). The cochlea acts as the sound wave sensor and helps in conversion of sound waves into electric impulses that are transmitted to the CNS. (Leavingbio n.d.). The semicircular canals maintain body balance by detecting orientation of gravitational force. These canals are filled with a fluid whose flow as a result of change in position tilts the orientation of a cone. The movement of the cone stimulates sensory nerve endings that initiate nerve impulses. In conclusion, the nervous system is responsible for the coordination of all life processes some of which are critical such as heartbeat. The eye and the ear are among the sense organs that provide vision, hearing and body balance. These organs have various parts all of which function to contribute to the overall function of the organ. For instance, the amount of light passing through the eye is regulated by the pupil and hence affects the quality of vision achieved. At night, the pupil diameter increases to optimize the amount of light and enhance vision even in the dim environment. Similarly, the ear has a pinna that collects and directs sound waves into the ear that are processed and translated into nerve impulses. References Anonymous n.d., Reflexes, [online] Available at, < http://csmbio.csm.jmu.edu/biology/danie2jc/reflex.htm>. [Accessed] 28 Feb. 14 Biologymad 2004, The Human Nervous System, [online] Available at, < http://www.biologymad.com/nervoussystem/nervoussystemintro.htm>. [Accessed] 28 Feb. 14 Bowen, R 2010, Mechanism of Action and Physiologic Effects of Thyroid Hormones, [online] available, < http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/physio.html>. [Accessed] 29 Feb. 14 Carter, S 2014, Endocrine System, [online] Available at, < http://biology.clc.uc.edu/courses/bio105/endocrin.htm>. [Accessed] 28 Feb. 14 Farabee, M.J. 2010, The Nervous System, [online] Available at, < http://www2.estrellamountain.edu/faculty/farabee/biobk/biobooknerv.html>. [Accessed] 28 Feb. 14 Leavingbio n.d., The Senses, [online] Available at, < http://leavingbio.net/the%20senses_files/the%20senses.htm>. [Accessed] 28 Feb. 14 Lodish H, Berk A, & Zipursky SL, et al., 2000. Overview of Neuron Structure and Function in Molecular Cell Biology. 4th edition. New York: W. H. Freeman. RSC n.d., Nerves and hormones, [online] Available at, < http://www.rsc.org/Education/Teachers/Resources/cfb/nerves.htm>. [Accessed] 28 Feb. 14 UNIT V n.d. Metabolic Effects of Insulin and Glucagon, [online] Available at: < http://www.cnupharm.ac.kr/board/file_mini_4_daesok/2005%2023%20Insulin%203_30_04.pdf>. [Accessed] 28 Feb. 14 Read More