Category: Nervous System

There is no use denying the fact that the current age could be called the era of technology and scientific progress. The thing is that in the last several decade humanity has managed to achieve the progress that seemed impossible for the previous generations. Due to this very fact, a coherent society obtains new features every year. New inventions, discoveries, and technologies have a great impact on the everyday life of people making it easier and more productive. Thus, technologies that could help reduced people to increase the quality of their life and perform various functions and activities with a great level of efficiency become especially vital. Besides, it is possible to say that the shift of the priorities of society towards humanistic ones also influences how society develops That is why biotechnology also obtained a great stimulus for its development. Now, it is taken as the science that could help people with reduced abilities or some missing parts of the body to obtain the possibility to feel feelings connected with the functioning of these limbs. It is also obvious that it is closely connected with the functioning of the nervous system. That is why, it is possible to state the fact that nowadays, people with various defects can restore their limbs and perform various kinds of activity.

Resting on these facts, it is possible to say that nowadays, the sphere of biotechnology could be described as rather perspective. It could be taken as the science that is comprised of the main aspects of biology and basic principles of functioning of various technologies (“What is Biotechnology?”.para. 2). Thus, the combination of such powerful and important sciences leads to the appearance of a great number of various opportunities for people. Nevertheless, according to Phillips and Ilcan, this very sector could provide hope for people with various disabilities because of a great number of researches and successes connected with the reattaching of lost limbs (106). The most important thing is that biotechnology does not simply aim at creating some complicated artificial limbs. However, the idea to restore the feelings connected with the functioning of some lost parts of the body is quite topical now.

Besides, it should also be said that the modern level achieved by biotechnologists and biologists could be taken as quite acceptable for the accomplishment of tasks like that. According to the latest research in the given sphere, scientists managed to restore the lost art of the finger with the help of gene engineering (Singer para. 5). The restored part of the body responded to all stimuli and obviously could be taken as the part of the whole body and its nervous system. Though, it is possible to state the fact that the most important task is achieved. The thing is, that is it not enough to connect the missing limb to the body. However, for a patient to be able to move it, to perform various actions, and to feel it, it should be connected to the central nervous system of a person for it to manage this very limb (Walker 34). Thus, taking into account the level of biotechnologies, it becomes obvious that nowadays the main problem is not to create the artificial limb, that should look like a real one, however, to restore its sensation and join it to the nervous system.

However, it should be said that the importance of this direction of development of biotechnology lies in the fact that many people have various defects. Additionally, these people could be divided into two groups: those, who have inborn defects and those who have lost their limbs in consequence of some accident. The thing is that approaches to these categories should be different. People who belong to the second group have the experience of manipulating their limbs and feelings connected with it. That is why they should not be taught how to control the regained limb and how to feel it. However, the first group of people has some worse conditions. The thing is, that being born with undeveloped limbs, they do not have the needed experience and are not able even to imagine it (Singer para. 6). Additionally, their nervous system also does not have the needed mechanisms as they were not developed in the process of growth of a fetus. That is why the problem to provide the needed experience for disabled people appears.

However, it is possible to say that nowadays, there is the tendency to assume that transplantation of the nervous system could be taken as one of the possible solutions to the existing problem. The thing is that transplantation of the neural system “has been proposed as a promising therapeutic strategy in almost all neurological disorders characterized by the failure of central nervous system endogenous repair mechanisms in restoring the tissue damage and rescuing the lost function” (De Feo, Merlini, Laterza and Martino 322). Thus, it is possible to assume that the same procedure could be created for people with various defects. Thus, the given practice will have some limits and peculiarities.

First of all, it is obvious that a person, who has lost his/her limb, could be suggested an artificial one based on his/her nervous system. He/she could be the donor and the needed neural system could be created based on his/her cells. Having the experience of living with all limbs, this person will be able to restore his/her functionality in comparatively short terms. However, speaking about people with inborn defects, it should be said that there is the idea that the nervous system of a person who has the experience of manipulating the limb should be chosen as the basis for the further creation of some artificial bionic limb (Ellman et al. 1883). The thing is, that these experiences could be found on the cellular level and might be helpful for these people while trying to master the basic skills of manipulating the limb. That is why it should be said that modern science has a great number of tasks connected with the transplantation of the nervous system to solve.

With this in mind, resting on these facts, it is possible to make a certain conclusion. It should be said that due to the blistering development of science and various technologies, a great number of people living with different disabilities could obtain some hope for recovery. Besides, biotechnology suggests a certain variant for people with absent limbs which lies in the creation of artificial ones, however, their functioning could be controlled with the help of a nervous system transplanted to a person. However, the difference between people who lost their limbs and those, who have inborn problems should be taken into account and serve as the basis for designing various approaches towards the whole process.

Works Cited

De Feo, Daniel, Arman Merlini, Capri Laterza and Gio Martino. “Neural stem cell transplantation in central nervous system disorders: from cell replacement to neuroprotection”. Current opinion in Neurology. 25.3(2012): 322-333. Web.

Ellman, Michael, Cristopher LaPrade, Sean Smith, Matthew Rasmussen, Lars Engebretsen, Coen Wijdicks and Robert LaPrade. “Structural Properties of the Meniscal Roots”. Amercian Journal of Sport medicine. 42.8 (2014): 1881-1887. Web.

Phillips, Lynne and Suzan Ilcan. Responsible Expertise Governing the Uncertain Subjects of Biotechnology. Critique of Anthropology. 27.1 (2007):103-126. Web.

Singer, Emily. Prosthetic Limbs That Can Feel. 2007. Web.

Walker, Sharon. Biotechnology Demystified. New York: McGraw-Hill Education. 2006. Print.

What is Biotechnology?. n.d. Web.

The nervous system is a part of an organism that coordinates its activity and sensory information by transmitting signals to and from different parts of the body. It works in coordination with the endocrine system, which is a chemical messenger system that comprises a number of glands that make hormones (Tortora & Derrickson, 2016). The nervous and endocrine systems work together to initiate and control movement, coordinate body functions, and react to changes in the internal and external environment.

The nervous system consists of two main parts, the central nervous system (CNS), which comprises the brain and the spinal cord, and the peripheral nervous system, which consists of nerves. Nerves transmit information to and from different organs, and the CNS integrates information and coordinates the activity of all parts of the body (Moini, 2019). The endocrine system consists of a number of glands, the major of which are the thyroid gland and the adrenal gland. Glands produce hormones, which are signaling molecules that regulate physiology and behavior (Tortora & Derrickson, 2016). The neural control center for all endocrine activity in the human body is the hypothalamus, which is a part of the brain that connects the nervous system with the endocrine system.

Nervous system problems are common and include several types of disorders: infections, vascular, structural, functional, and degenerative disorders. The most common neurological disorders are stroke, epilepsy, multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease (“Overview of nervous system disorders,” n.d.). The diseases of the endocrine system are primarily caused by misregulated hormone release, inappropriate response to signaling, lack of a gland, or structural enlargement of a gland. They include diabetes, thyroid disorders, osteoporosis, and polycystic ovary syndrome.

References

Moini, J. (2019). Anatomy and physiology for health professionals. Jones & Bartlett Learning.

Overview of nervous system disorders.(n.d.). Johns Hopkins Medicine. Web.

Tortora, G. J., & Derrickson, B. (2016). Principles of anatomy and physiology (15^th ed.). J. Wiley.

Human nervous system is a system that transports stimuli from sensory receptors to the brain and spinal cord, as well as transmitting impulses to other regions of the body. It regulates other body’s systems and connects the brain with the surrounding environment. The environment of Proxima c. sets conditions which are impossible to live for a human being. This is because of its very low temperature, radiation, and high solar wind pressure. Under such conditions, human nervous system would not function as impulses will not be transmitted through body parts.

To adapt to such harsh conditions, neurons have to be protected with more fatty layers and be more resistant to external factors. Adaptation should be done at a cellular level to ensure that the system has been altered from its core. Neurons are responsible for transmission of information in the system, thereby to make human beings adaptive to Proxima c., it is crucial to change the structure of neurons. Kohn and Ritzmann (2018) found that human neurons learnt to adapt to changes in gravity, and this can further be applied to other factors, such as pressure and low temperature. Such cellular level adaptation would benefit humanoid more as it provides further changes in the systems. For example, the process of transmission of impulses will be slow down, allowing other systems to adapt to changing circumstances. Moreover, neurons will change the brain structure that would benefit the overall adaptation of a body, making it ready for the new conditions.

Neurons are the building blocks of the nervous system, thereby if they alter their structure, they may help the body to stay alive in the environment of Proxima c. Clément et al. (2020) through their investigation of the challenges to the central nervous system during spaceflight missions, found that neurons are sensitive to changes in temperature more than in pressure. Therefore, if neurons are resistant to low temperature, they would ensure that body will be alive under the conditions of Proxima c. More fatty acid layers on neurons would provide more protection to them, meaning that they can transmit impulses even in harsh situations like extremely high pressure. However, such layers may slow down the transmission and the normal body processes will also be slower than on Earth. D’Angelo et al. (2018) state that metabolism correlates to neuronal maturation, suggesting that changes in the structure of neurons would lead to the slow metabolic processes. Such the situation allows a body to preserve internal temperature.

As it can be seen, neuronal transformation regarding the conditions of the environment of Proxima c. cannot provide better function of the nervous system on Earth. Due to the additional fatty layers, metabolism will not work at its normal rate, and it may hinder the flow of impulses needed to interact with the environment of Earth. A human being will not obtain as well as response to the coming information, such as light, pressure or temperature. Moreover, neurons with more fatty layers can obtain other functions, such as transmitting different information. For example, neurons that were responsible to light detection would also deliver information regarding smell or vision. This would not be working on Earth as neurons have been already adapted to the conditions there. Yet, such neuronal changes will be perfect for the environment of Proxima c.

References

Clément, G. R., Boyle, R. D., George, K. A., Nelson, G. A., Reschke, M. F., Williams, T. J., & Paloski, W. H. (2020). Challenges to the central nervous system during human spaceflight missions to Mars. Journal of neurophysiology, 123(5), 2037-2063.

D’Angelo, M., Antonosante, A., Castelli, V., Catanesi, M., Moorthy, N., Iannotta, D.,… & Benedetti, E. (2018). PPARs and energy metabolism adaptation during neurogenesis and neuronal maturation. International Journal of Molecular Sciences, 19(7), 1869.

Kohn, F. P., & Ritzmann, R. (2018). Gravity and neuronal adaptation, in vitro and in vivo—from neuronal cells up to neuromuscular responses: a first model. European Biophysics Journal, 47(2), 97-107.

Structure of a Nerve

The peripheral nervous system is a part of the nervous system that contains all nerves not included in the CNS. A nerve consists of a bundle of neuron fibers surrounded by protective connective tissue. Each fiber is wrapped in a fine tissue called the endoneurium. Fibers are arranged in bundles called fascicles, which are covered by a coarser tissue sheath – the perineurium. All fascicles are wrapped together by a tough tissue covering referred to as the epineurium.

Nerves are classified depending on the direction of transmitting signals. Mixed nerves, which include all spinal nerves, conduct both incoming sensory impulses and outgoing motor signals. Sensory or afferent nerves carry sensory information toward the CNS. In contrast, motor or efferent nerves conduct only impulses from the CNS to muscles and glands.

Cranial Nerves

There are 12 pairs of cranial nerves, most of which serve neck and head. Only the vagus nerve extends to the thorax and abdomen. All pairs of cranial nerves are numbered, and their names reflect their functions. For example, oculomotor cranial nerves control the movement of eyeballs and eyelids, the lens shape, and pupil size. Most cranial nerves belong to the mixed group; the three exceptions are olfactory, optic, and vestibulocochlear nerves, which are sensory nerves.

Spinal Nerves

The human body has 31 pairs of spinal nerves. Each spinal nerve is formed by a combination of ventral and dorsal roots of the spinal cord. Right after being formed, each nerve divides into ventral and dorsal rami. As a result, every single spinal nerve has a length of only about ½ inch. Spinal nerves and rami contain both motor and sensory fibers. Therefore, if a spinal nerve or its ramus is damaged, it leads to flaccid paralysis and lost sensation in the respective area.

Spinal Nerve Plexuses

Dorsal rami of spinal nerves serve the muscles and skin of the human back. The ventral rami of most spinal nerves form networks called plexuses. There are four nerve plexuses: cervical, brachial, lumbar, and sacral. The cervical plexus contains nerves C1-C5 and serves the diaphragm and skin and muscles of the neck and shoulders. The brachial plexus includes nerves C5-C8 and T1 and serves the deltoid muscle and skin of shoulder and muscles and skin of forearms, wrists, and hands. Nerves L1-L4 belong to the lumbar plexus, responsible for the lower abdomen, and muscles and skin of hips and thigs. The sacral plexus contains nerves L4-L5 and S1-S4 and serves the lower trunk, legs, and feet. Nerves T1-T12 do not form a plexus. They are called intercostal nerves and supply the muscles and skin of the lateral and anterior trunk and muscles between the ribs.

Autonomic Nervous System

The autonomic or involuntary nervous system (ANS) is part of the PNS that works automatically and controls certain body activities, such as blood pressure, pupil size, heart and breathing rate, stomach secretions, and other unconscious processes. It consists of neurons regulating glands, smooth muscles, and the cardiac muscle. The structure of the ANS differs from that of the somatic nervous system, controlling skeletal muscles. In the somatic system, cell bodies of motor neurons are located in the CNS, and their axons extend to the respective skeletal muscles. In the ANS, there are two motor neurons rather than one. The first motor neuron is located in the CNS, and its axon, called the preganglionic axon, extends to a ganglion outside of the CNS, where it synapses with the second motor neuron. The axon of this second neuron, called the postganglionic axon, extends right to the organ that it supplies. The ANS consists of two divisions: sympathetic and parasympathetic, which serve the same organs but result in opposite effects.

Sympathetic Division

The preganglionic neurons are located in the gray matter of the spinal cord in nerves T1-L2. Their axons exit the cord through the ventral root. Then, they enter the spinal nerve and go through a small communicating branch called ramus communicans. After that, they enter a sympathetic chain ganglion located on both sides of the vertebral column. In the ganglion, axons either synapse with the second neuron or go further to form the splanchnic nerves. These nerves travel to a collateral ganglion where they synapse with ganglionic neurons. Then, the postganglionic axon exits the collateral ganglion and extends to a visceral organ.

The sympathetic division is often called a “fight-or-flight” system because its function is to help the body quickly cope with situations that threaten homeostasis. The effects of this system are short-term and can be manifested in an increased heart rate, sweating, the dilation of vessels in skeletal muscles, etc. The sympathetic system also controls most blood vessels.

Parasympathetic Division

In the parasympathetic division, preganglionic neurons are located in cranial nerves III, VII, IX, and X and spinal nerves S2-S4. Preganglionic axons pass through cranial nerves and enter a terminal ganglion, where they synapse with the motor neuron. From there, postganglionic neurons extend to the organs they serve. In the sacral region, axons leaving the spinal cord form pelvic nerves that extend to the pelvic cavity and synapse with motor neurons in the terminal ganglia. Then, postganglionic axons extend to their organs.

The parasympathetic division works when the body is not threatened and rests. It is sometimes called a “resting-and-digesting system” because it ensures normal digestion, urination and defecation, and the conservation of body energy.

Developmental Aspects of the Nervous System

The nervous system is formed during early fetal development. Therefore, various adversities during pregnancy, such as maternal infections, smoking, radiation, and drugs, may lead to congenital impairments. The hypothalamus, responsible for temperature regulation, matures at later stages of fetal development. Thus, premature babies often cannot control their body heat loss. The nervous system matures during childhood by means of myelination. It reaches its developmental peak in young adulthood when the brain weight is at its maximum. As people age, their neurons become damaged and die, and their brain weight declines. The sympathetic system’s functioning also declines with age, which is manifested in orthostatic hypotension, arteriosclerosis, and hypertension.

Reference

Marieb, E. N. (2008). Essentials of human anatomy and physiology (9^th ed.). Benjamin Cummings.

Introduction

In this course, I studied the most important concepts related to the structure and function of the human nervous system. The first significant ideas we were introduced to in the lectures were the theses about the importance of this part of the body. It was revealed that the nervous system is responsible for basic processes, including regulation of all organ activities, cognitive activity, as well as human interaction with the environment. Further, the structure of this structure in the organism was considered in detail. In this part of the course, I encountered a particularly large amount of new information.

Discussion

I had not anticipated that all nerve activity could be divided into two sections, including the central and peripheral. The former includes the spinal cord and brain, which contain a large network of vessels that transport necessary substances. The peripheral system includes all the endings that run from the above organs to the tissues of the entire body. An important insight that has changed my perception of all human nervous activity is the division of the system into somatic and autonomic. All human actions and internal and external reactions can always be attributed to one of these functions. Somatic implies innervation and provision of all processes under control, while autonomic implies excitation and maintenance of metabolic processes.

Conclusion

Any mental changes in a person are due to a shift in the balance toward one of these spheres, hence a healthy state is considered to be a balanced operation. I used to think that the nervous system has one general function and is not subdivided into levels depending on interrelation with the consciousness. The information I studied allowed me to reconsider my ideas about what processes ensure the nervous activity of people.

Comparison between Somatic and Autonomic Nervous Systems

The autonomic nervous system (ANS) is a division of the peripheral nervous system (PNS) that regulates the functioning of visceral organs and plays a role in homeostatic control[1]. The ANS together with the somatic nervous system (SNS) make up the PNS. Autonomic neurons control hormone and enzyme secretion from glands and the contraction of smooth and heart muscles.

The somatic division differs from the autonomic division with regard to effectors, efferent pathways, and neurotransmitter effects. The skeletal and heart muscles are the major target organs (effectors) of the impulses relayed by the somatic fibers and autonomic neurons respectively[2]. The two systems also differ in relation to their efferent pathways. In the SNS, a motor neuron (efferent pathway) extends from the CNS to the peripheral effectors. In comparison, the pre- and post-ganglionic nerves constitute the efferent pathway of the autonomic system. Thus, the SNS has only one neuron while the ANS has two. The position of the cell bodies is also varies between the two systems. The cell body of the preganglionic neuron of the ANS is located within the CNS while its axon (myelinated) joins the postganglionic motor neuron, which lies outside the CNS, through its synapse. The postganglionic axon (unmyelinated) transmits signals to the peripheral effectors. The cell bodies of somatic neurons lie within the brain or spinal cord. The ANS also contains ganglia, which are absent in the SNS. The two nervous systems also differ with regard to their neurotransmitter effects. For the SNS, the neurotransmitter released at the synaptic cleft is acetylcholine. In comparison, the autonomic impulse transmission involves acetylcholine and norepinephrine[3].The ANS plays an important role in homeostasis and thermoregulation.

Control and Integration of ANS

The functions of ANS are regulated by various brain centers. The medulla and spinal cord centers (higher centers) control the reflex activity function of the ANS. In particular, the reticular formation of the medulla plays a big role in autonomic regulation. The medulla motor centers stimulate various reflex activities, including vessel dilation (vasomotor), heart rate (cardiac), gut activity (peristalsis), and breathing (respiratory). Respiratory centers are also located in the ‘Pons’, i.e., nerve fibers that link the medulla with the midbrain. Oculomotor nuclei located in the midbrain are the centers that control pupil dilation.

Hypothalamic integration centers (lower centers) control autonomic responses through the lower and higher brain centers[4]. Parasympathetic activity (localized effects) is controlled by the anterior and medial brain regions, while sympathetic function (widespread response) is regulated by the posterior part. Sensory impulses from these centers are conveyed via the reticular formation to the ANS motor nerves (preganglionic) located in the brain and spinal cord. Body process such as heart rate, hormone secretion, peristalsis, and blood pressure/sugar levels, among others are regulated by hypothalamic centers. The centers also control emotions and biological feelings of hunger or thirst.

The limbic lobe (cerebrum), in stress situations, sends impulses to the hypothalamus, which stimulates the sympathetic division of the ANS to effect a ‘fight or flight response’[5]. Cortical centers in the ‘higher’ brain link with the limbic system to bring about conscious regulation of the ANS functioning.

The Divisions of the ANS

The ANS consists of two parts, the parasympathetic division, which controls involuntary organ function when the body is in a resting phase and the sympathetic division that is activated in a ‘fight or flight’ situation. The parasympathetic or craniosacral part consists of the cranial and sacral outflows. It controls the digestive system and is normally active when the body is resting. It maintains organ functioning at the lowest level. In contrast, the sympathetic or thoracolumbar ANS plays a role in the activation of the body systems under stressful situations or ‘flight-or-fight’ conditions[6]. It stimulates pupil dilation, sweating, high respiratory and breathing rates, and elevated blood sugar and pressure. It diverts blood to the “brain and heart and skeletal muscles” during heavy exercises or danger[7].

The functioning of the parasympathetic and sympathetic divisions involves two neurotransmitters, which include acetylcholine (cholinergic) and norepinephrine (adrenergic). Cholinergic nerves include all ANS preganglionic pathways and postganglionic fibers of the parasympathetic nerve that terminate in peripheral effectors[8]. In comparison, all adrenergic fibers are sympathetic in function.

Both divisions of the ANS serve the visceral organs in the body. Their interaction involves a mechanism of dynamic antagonism to facilitate the balance of homeostasis in the body. Either the parasympathetic or the sympathetic division exerts its effects under certain conditions only. Antagonistic interactions occur in the organs of the digestive, respiratory (lungs), and circulatory (heart) systems. The sympathetic division usually elevates respiratory activity and heart rate and slows down peristalsis in the gut[9]. In contrast, the parasympathetic activity overrides all these processes.

Sympathetic activity is prevalent in the blood vessels where they maintain vascular contraction at its basal rate. Parasympathetic fibers regulate muscular contraction (heart and smooth muscles) and hormone and enzyme secretion from glands. When frightened or under stress, the sympathetic fibers stimulate vessel constriction to increase blood flow to the organs and muscles. In contrast, the parasympathetic nerve suppresses an elevated heart rate and maintains basal levels of contraction in the urinary and digestive systems. The sympathetic nerve can counteract these effects when the body is under stress. The parasympathetic fiber stimulates all glandular organs except sweat glands and adrenal medulla[10].

Cooperative effects of the two divisions occur in the genital region. The vasodilation of arteries, which increases blood flow to the genitalia leading to penile or clitoral erection during intercourse, is a function of the parasympathetic division[11]. On the other hand, the sympathetic nerve controls ejaculation and vaginal peristalsis. The unique functions of the sympathetic nerve include the effect on the kidneys and the adrenal and sweat glands.

The Relationship between Structure and Function of the Two Divisions

The parasympathetic division consists of the cranial and sacral flows. The cranial outflow encompasses the midbrain’s oculomotor nuclei whose preganglionic neurons terminate in the ciliary muscles of the eye. It is involved in pupil constriction and the adjustment of the eye lens. The cranial outflow also contains the facial nerve whose preganglionic fibers end in the lacrimal glands. It plays a role in tearing and lubrication of the eye lens. The preganglionic fibers of facial nerve also stimulate the sub-mandibular and sublingual regions, which causes the salivary glands to release enzymes and saliva.

The sympathetic division consists of the thoracolumbar outflow that terminates at various visceral organs in the body. Its unique roles encompass metabolic control, stimulation of blood flow, and regulation of blood pressure. Sympathetic nerves occur in glandular areas, such as adrenal and sweat glands as well as in organs like the kidneys[12]. This explains why, during thermoregulation, the sympathetic nerves stimulate widespread effects (vasodilation), which allow blood to flow to the skin and cool the body through direct heat loss. When the temperature in the external environment is low, the sympathetic nerve stimulates vasoconstriction, which delivers warm blood to vital body organs. It also activates the kidneys to secrete ‘renin’ enzyme that elevates blood pressure through angiotensin activity[13].

The sympathetic nerve also has long-lasting metabolic effects. The effects are long-lived because the parasympathetic nerve cannot override them. They include elevated cellular metabolism, enhanced sugar levels in the blood, utilization of fats as metabolic substrates, and improved consciousness through the stimulation of the brain’s reticular activating system (RAS)[14].

The ANS Neurotransmitters

Impulse transmission across the synapses involves two neurotransmitters, that is, acetylcholine and norepinephrine. Acetylcholine transmits impulses between most SNS and ANS fibers. On the other hand, all sympathetic postganglionic fibers release norepinephrine apart from those innervating the genitalia, the sweat glands, and the skeletal muscle arteries and veins[15]. These neurons release acetylcholine.

Adrenaline is secreted during stressful situations. Fright causes the sympathetic nerve to stimulate the adrenal glands, which secrete adrenaline that elevates the blood pressure. This results in enhanced blood flow to the muscles leading to a prolonged ‘fight-or-flight’ response. Adrenaline also elevates cellular metabolism to produce energy for flight or fight. Enhanced mental alertness allows one to overcome stressful situations. Thus, sympathetic stimulation leads to widespread and long-lasting effects on target organs. In contrast, parasympathetic activity is often localized and temporal.

Bibliography

Janig, Wilfrid. Integrative Action of the Autonomic Nervous System: Neurobiology of Homeostasis. Cambridge: Cambridge University Press, 2008.

Marieb, Elain. Essentials of human Anatomy and Physiology. Upper Saddle River, NJ: Pearson, 2011.

Tortora, Gerald and Bryan Derrickson. Principles of Anatomy and Physiology. New York: Wiley, 2011.