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Liver abnormalities such as hepatitis generic 40mg protonix overnight delivery, cirrhosis purchase protonix 20mg with visa, alcohol damage order 40mg protonix otc, and drug toxicities result in decreased levels of plasma proteins, which decrease blood viscosity. While leukocytes and platelets are normally a small component of the formed elements, there are some rare conditions in which severe overproduction can impact viscosity as well. Vessel Length and Diameter The length of a vessel is directly proportional to its resistance: the longer the vessel, the greater the resistance and the lower the flow. As with blood volume, this makes intuitive sense, since the increased surface area of the vessel will impede the flow of blood. The length of our blood vessels increases throughout childhood as we grow, of course, but is unchanging in adults under normal physiological circumstances. One pound of adipose tissue contains approximately 200 miles of vessels, whereas skeletal muscle contains more than twice that. Gaining about 10 pounds adds from 2000 to 4000 miles of vessels, depending upon the nature of the gained tissue. One of the great benefits of weight reduction is the reduced stress to the heart, which does not have to overcome the resistance of as many miles of vessels. In contrast to length, the diameter of blood vessels changes throughout the body, according to the type of vessel, as we discussed earlier. The diameter of any given vessel may also change frequently throughout the day in response to neural and chemical signals that trigger vasodilation and vasoconstriction. The vascular tone of the vessel is the contractile state of the smooth muscle and the primary determinant of diameter, and thus of resistance and flow. The effect of vessel diameter on resistance is inverse: Given the same volume of blood, an increased diameter means there is less blood contacting the vessel wall, thus lower friction and lower resistance, subsequently increasing flow. A decreased diameter means more of the blood contacts the vessel wall, and resistance increases, subsequently decreasing flow. The influence of lumen diameter on resistance is dramatic: A slight increase or decrease in diameter causes a huge decrease or increase in resistance. This is because resistance is inversely proportional to the radius of the blood vessel (one-half of 4 the vessel’s diameter) raised to the fourth power (R = 1/r ). This means, for example, that if an artery or arteriole constricts to one-half of its original radius, the resistance to flow will increase 16 times. And if an artery or arteriole dilates to twice its initial radius, then resistance in the vessel will decrease to 1/16 of its original value and flow will increase 16 times. The Roles of Vessel Diameter and Total Area in Blood Flow and Blood Pressure Recall that we classified arterioles as resistance vessels, because given their small lumen, they dramatically slow the flow of blood from arteries. Notice in parts (a) and (b) that the total cross-sectional area of the body’s capillary beds is far greater than any other type of vessel. Although the diameter of an individual capillary is significantly smaller than the diameter of an arteriole, there are vastly more capillaries in the body than there are other types of blood vessels. Part (c) shows that blood pressure drops unevenly as blood travels from arteries to arterioles, capillaries, venules, and veins, and encounters greater resistance. However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels. Part (d) shows that the velocity (speed) of blood flow decreases dramatically as the blood moves from arteries to arterioles to capillaries. This is a leading cause of hypertension and coronary heart disease, as it causes the heart to work harder to generate a pressure great enough to overcome the resistance. Arteriosclerosis begins with injury to the endothelium of an artery, which may be caused by irritation from high blood glucose, infection, tobacco use, excessive blood lipids, and other factors. Artery walls that are constantly stressed by blood flowing at high pressure are also more likely to be injured—which means that hypertension can promote arteriosclerosis, as well as result from it. Moreover, circulating triglycerides and cholesterol can seep between the damaged lining cells and become trapped within the artery wall, where they are frequently joined by leukocytes, calcium, and cellular debris. The term for this condition, atherosclerosis (athero- = “porridge”) describes the mealy deposits (Figure 20.

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For an adult under certain conditions he would be right buy protonix 40 mg online, but it is quite wrong to adopt 120/80 mmHg as the normal standard for a resting child discount protonix 40mg without a prescription, a pregnant woman in midterm or an elderly man purchase protonix 40mg without prescription. It is not equal to the average of systolic and diastolic pressure because the pressure remains nearer to the diastolic pressure than to the systolic pressure during the greater part of the cardiac cycle. If heart rate increases, the relative amount of time the heart spends in diastole decreases. The increase in pulse pressure is especially striking and iscaused by reduced arterial compliance. Reduced compliance is due to arteriosclerosis (hardeningof the arterioles by fibrosis and calcinosis), and is universal accompaniment to ageing. Conversely, pressure is reduced in the arteries above the heart level and is only 60mmHg or so in human brain during standing. Indirect effect Upon moving from lying to standing, arterial pressure changes at heart level due to changes in cardiac output and peripheral resistance. A transient fall in aortic pressure (which can produce a passing dizziness) is followed by a small but sustained reflex rise. Compared with the relaxed states, while attending a meeting often raise it by 20mmHg. The pressor effect of stress is particularly harmful to patients with ischemic heart disease. Valsalva maneuver: Valsalva maneuver, a forced expiration against a closed or narrowed glottis, causes a complex sequence of pressure changes. Pregnancy: In pregnancy blood pressure gradually falls and reaches a minimum at approximately 6 months. Veins don’t show distensibility are filled; they contain 3- times blood volume than in that of arteries. Veins have more capacity arteries expand and recoil, store pressure during systole of the heart and release it during cardiac diastole -the pressure stores. Capacitance vessels: act as blood reservoirs - veins & venules Regulation of flow through blood vessels Blood vessel caliber, an important factor in the determination of resistance and capacitance, is actively regulated by neural and humoral mechanisms and passively affected by the pressure within it. Vasomotor refers to rhythmic oscillating changes in the caliber of the arterioles, metarterioles, and precapillary sphincters resulting from vasoconstriction or vasodilatation and venomotion. Neural control of vasomotor tone Vasomotor tone is the continuous, low-level activity of vascular smooth muscle fibers that maintain the tension of the vascular walls. It varies in different tissues, and is mainly dependent upon the rate of impulses from the sympathetic nerve fibers to the muscle cells. This tone is higher in skeletal muscles and splanchnic area blood vessels and 193 least in the heart, brain, and kidney. Vasomotor tone is the tension basically to maintain arterial blood pressure; increase in tone increases blood pressure; decrease in tone lowers blood pressure. In order to maintain an adequate coronary and cerebral blood flow while supplying extra blood to the muscles during heavy exercise, blood pressure must be maintained or increased and blood shifted from the splanchnic and renal areas to the active muscles by changes in the resistance of these vascular beds. Sympathetic regulation of vasomotor & venomotor tone Postganglionic sympathetic fibers from the thoracolumbar sympathetic ganglia provide innervation to all blood vessels, though the density of innervations varies in different tissues. Sympathetic fibers innervate smooth muscles in the principal arteries, small arteries, and terminal arterioles in to tissues. Precapillary arterioles and metarterioles in skeletal muscles are also well innervated by sympathetic nerves. Vasoconstriction allows movement of large amount of blood towards the heart in emergencies, such as hemorrhage. Only very few blood vessels are innervated by the parasympathetic, hence this system is less potent.

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Lower limb muscles Muscle Origin Insertion Action Muscles that move the thigh Iliopsoas Ilium and Trochanter of Flexes thigh vertebrae femur Tensor fascia Anterior superior Lateral condyle Abducts thigh latae iliac of tibia spine Gluteus Ilium quality protonix 40 mg, sacrum order protonix 20mg online, Lateral side of Extends and abducts maximus and coccyx femur thigh Gluteus Ilium Trochanter of Abducts thigh medius femur Adducter Pubis Femur Adduct thigh muscles of thigh Muscles that move the leg Quadriceps Anterior superior Tibial tuberosity Extends leg and flexes femoris Rectus iliac thigh femoris spine Vastus lateralis Femur Tibial tuberosity Extends leg Vastus Femur Tibial tuberosity Extends leg medialis 128 Human Anatomy and Physiology Vastus Femur Tibial tuberosity Extends leg intermedius (not shown in illustration) Sartorius Anterior superior Tibia Flexes leg and thigh iliac spine Hamstring Ischium and Fibula Flexes leg and muscles femur extends thigh Biceps femoris Semimembran Ischium Tibia Flexes leg and osus extends thigh Semitendinosu Ischium Tibia Flexes leg and s extends thigh Muscles that move the ankle and toes Tibialis anterior Tibia Tarsal and first Dorsiflexes foot metatarsal Deep anterior Tibia or fibula Phalanges generic protonix 20mg on line, Extend toes leg muscles metatarsals, tarsals Gastrocnemius Medial and Calcaneus Plantar flexes foot lateral epicondyle of femur Soleus Tibia and fibula Calcaneus Plantar flexes foot Deep posterior Tibia of fibula Phalanges, Evert foot leg muscles metatarsals, tarsals Peroneus Fibula and tibia Tarsals and Evert foot Abduct, muscle Intrinsic Tarsals or metatarsals adduct, flex, and foot muscles metatarsals Phalanges extend toes 129 Human Anatomy and Physiology Figure 6-6 Superficial muscles, anterior (front view) (Source: Carola, R. Name and describe the major actions and innervations of the principal muscles of the head and neck, upper extremities, trunk, and lower extremities. Selected Key Terms The following terms are defined in the glossary: Accommodation Midbrain Acetylcholine Nerve Action potential Nerve impulse Afferent Neucleus Autonomic nervous system Neuron Axon Neurotransmitter Brain stem Ossicle Cerebellum Plexus 134 Human Anatomy and Physiology Cerebral cortex Pons Cerebrum Proprioceptor Choroid Receptor Cochlea Reflex Conjunctiva Refraction Cornea Retina Dendrite Sclera Diencephalons Semicircular canal Effector Spinal cord Efferent Stimulus Epinephrine Synapse Ganglion Thalamus Gray matter Tract Hypothalamus Tympanic membrane Lacrimal Ventricle Medulla oblongata Vestibule Meninges White matter General Function None of the body system is capable of functioning alone. All are interdependent and work together as one unit so that normal conditions within the body may prevail. Control of the body’s billions of cells is accomplished mainly by two communication systems: the nervous system and the endocrine system. Both systems transmit information from 135 Human Anatomy and Physiology one part of the body to another, but they do it in different ways. The nervous system transmits information very rapidly by nerve impulses conducted from one body area to another. The endocrine system transmits information more slowly by chemicals secreted by ductless glands into blood steam and circulated from glands to other parts of the body. Conditions both within and outside the body are constantly changing; the purpose of the nervous system is to respond to these internal and external changes (known as stimuli) and so cause the body to adapt to new conditions. The nervous system has been compared to a telephone exchange, in that the brain and the spinal cord act as switching centres and the nerve trunks act as cables for carrying messages to and from these centres. Cells of nervous system and their functions The two types of cells found in the nervous system are called neurons or nerve cells and neuroglia, which are specialized connective tissue cells. Dendrites are the processes or projections that transmit impulses to the neuron cell bodies, and axons are the processes that transmit impulses away from the neuron cell bodies. The three types of functional classification of neurons are according to the direction in which they transmit impulses. They do not conduct impulses to all parts of the body but only to two kinds of tissue-muscle and glandular epithelial tissue. Sensory neurons are also called afferent neurons; motor neurons are called efferent neurons, and interneurons are called central or connecting neurons. Myelin sheath is a white, fatty substance formed by Schwann cells that wrap around some axons outside the central nervous system. The fact that axons in the brain and cord have no neurilemma is clinically significant because it plays an essential part in the regeneration of cut and injured axons. Therefore the potential for regeneration in the brain and spinal cord is far less than it is in the peripheral nervous system. Impulse Generation and Conduction The Nerve Impulse The cell membrane of an unstimulated (resting) neuron carries an electric charge. Because of positive and negative ions concentrated on either side of the membrane, the inside of the membrane at rest is negative as compared with the outside. A nerve impulse is a local reversal in the charge on the nerve cell membrane that then spreads along the membrane like an electric current. The reversal occurs very rapidly (in less than one thousandth of a second) and is followed by a rapid return of the membrane to its original state so that it can be stimulated again. In other words, how does the axon of one neuron make functional contact with the membrane of another neuron? Within the branching endings of the axon are small bubbles (vesicles) containing a type of chemical known as a neurotransmitter. When stimulated, the axon releases its neurotransmitter in to the narrow gap, the synaptic cleft, between the cells. The neurotransmitter then acts as a chemical signal to stimulate the next cell, described as the postsynaptic cell. On the receiving membrane, usually that of a dendrite, sometimes another part of the cell, there are special sites, or receptors, ready to pick up and respond to specific neurotransmitters. Receptors in the cell membrane influence how or if that cell will respond to a given neurotransmitter. Acetylcholine (Ach) is the neurotransmitter released at the neuromuscular junction, the synapse between a neuron and a muscle cell.

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