Central And Peripheral Nervous System Functions

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Central And Peripheral Nervous System Functions – The peripheral nervous system (PNS) is the connection between the central nervous system and the rest of the body. The CNS is like the power plant of the nervous system. It produces signals that control body functions. The PNS is like the wires going to each house. Without these “wires,” signals from the central nervous system cannot control the body (nor can the central nervous system receive sensory information from the body).

The PNS can be divided into the autonomic nervous system and the sensory somatic nervous system. The autonomic nervous system controls body functions and is not controlled by consciousness; the sensory somatic nervous system transmits sensory information from the skin, muscles and sensory organs to the CNS, and sends motor commands from the CNS to muscle.

Central And Peripheral Nervous System Functions

Central And Peripheral Nervous System Functions

Figure 16.26. In the autonomic nervous system, preganglionic neurons of the CNS form synapses with postganglionic neurons of the PNS. On the other hand, postganglionic neurons act on target organs. Autonomic responses are mediated by the sympathetic and parasympathetic nervous systems, which antagonize each other. The sympathetic nervous system activates the “fight or flight” response, while the parasympathetic nervous system activates the “rest and digest” response.

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The autonomic nervous system acts as a relay between the central nervous system and the internal organs. It controls the lungs, heart, smooth muscle, and exocrine and endocrine glands. The autonomic nervous system controls these organs largely without conscious control; the condition of these various systems can be continuously monitored and changes implemented when necessary. Signaling to a target tissue typically involves two synapses: a preganglionic neuron (originating in the central nervous system) that synapses with a neuron in the ganglion, which in turn synapses with the target organ, as shown in 16.26. The autonomic nervous system has two parts that often have opposing roles: the sympathetic nervous system and the parasympathetic nervous system.

The sympathetic nervous system is responsible for the “fight or flight” response that occurs when animals are in a dangerous situation. One way to remember this is to think of one’s surprise when encountering a snake (“snake” and “cute” both start with an “s”). Examples of functions controlled by the sympathetic nervous system include increasing heart rate and inhibiting digestion. These functions help prepare an organism’s body for the physical strength needed to escape a potentially dangerous situation or fend off a predator.

Most preganglionic neurons in the sympathetic nervous system originate in the spinal cord, as shown in Figure 16.27. The axons of these neurons release acetylcholine onto postganglionic neurons within the sympathetic ganglion (which forms a chain that runs along the spinal cord). Acetylcholine activates postganglionic neurons. Postganglionic neurons then release norepinephrine to target organs. As anyone who feels rushed before a big exam, presentation or sporting event can attest, the influence of the sympathetic nervous system is everywhere. This is both because a preganglionic neuron synapses with multiple postganglionic neurons, amplifying the effect of the original synapse, and because the adrenal gland also releases norepinephrine (and the closely related hormone epinephrine) into the blood . The physiological effects of this release of norepinephrine include dilation of the trachea and bronchi (making it easier for the animal to breathe), increased heart rate, and blood flow from the skin to the heart, muscles, and brain (so the animal can think and run). The strength and speed of the sympathetic response helps organisms avoid danger, and scientists have found evidence that it can also increase LTP — allowing animals to remember a dangerous situation and avoid it in the future.

While the sympathetic nervous system is activated in stressful situations, the parasympathetic nervous system allows animals to “rest and digest.” One way to remember this is to think that in a relaxing situation like a picnic, the parasympathetic nervous system is in control (“picnic” and “parasympathetic” both start with a “p”). The cell bodies of parasympathetic preganglionic neurons are located in the brainstem and sacral (downward) spinal cord, as shown in Figure 16.27. Axons of preganglionic neurons release acetylcholine onto postganglionic neurons, which are often in close proximity to target organs. Most postganglionic neurons release acetylcholine into target organs, although some release nitric oxide.

What Is The Peripheral Nervous System

After the sympathetic nervous system is activated, the parasympathetic nervous system resets organ function (the adrenaline rush you often feel after a “fight or flight” event). The effects of acetylcholine release on target organs include slowing the heart rate, lowering blood pressure, and stimulating digestion.

The sensory somatic nervous system consists of cranial and spinal nerves and contains sensory and motor neurons. Sensory neurons transmit sensory information from the skin, skeletal muscles, and sensory organs to the central nervous system. Motor neurons carry information about desired movement from the central nervous system to muscles to stimulate them to contract. Without a sensory somatic nervous system, an animal cannot process any information about its environment (what it sees, feels, hears, etc.), nor can it control movement. Unlike the autonomic nervous system, which has two synapses between the CNS and target organs, sensory and motor neurons have only one synapse—one neuron terminal in the organ and the other in direct contact with the CNS neuron. Acetylcholine is the main neurotransmitter released at these synapses.

Humans have 12 cranial nerves, the nerves that go in and out of the skull (skull) as opposed to the spinal nerves that go out in the spine. Each cranial nerve has a name, see Figure 16.28 for details. Some cranial nerves carry sensory information only. For example, the olfactory nerves carry information about smells from the nose to the brainstem. Other cranial nerves carry almost exclusively motor information. For example, the oculomotor nerve controls the opening and closing of the eyelids and some eye movements. Other cranial nerves contain a mixture of sensory and motor fibers. For example, the glossopharyngeal nerve is involved in both taste (sensation) and swallowing (motor).

Central And Peripheral Nervous System Functions

Figure 16.28. The human brain contains 12 cranial nerves that receive sensory input and control motor output in the head and neck.

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Spinal nerves carry sensory and motor information between the spinal cord and the rest of the body. Each of the 31 spinal nerves (in humans) contains both sensory and motor axons. The cell bodies of sensory neurons are grouped into structures called dorsal root ganglia, as shown in Figure 16.29. Each sensory neuron has a projection — a sensory receptor on the end of the skin, muscle, or sensory organ — and another projection that forms a synapse with a neuron on the dorsal side of the spinal cord. Motor neurons have cell bodies in the ventral gray matter of the spinal cord and project through the ventral root into the muscles. These neurons are usually stimulated by interneurons within the spinal cord, but sometimes they are directly stimulated by sensory neurons.

Figure 16.29. Spinal nerves contain sensory and motor axons. The cell bodies of sensory neurons are located in the dorsal root ganglia. The cell bodies of motor neurons are located in the ventral part of the gray matter of the spinal cord.

The peripheral nervous system includes the autonomic nervous system and the sensory somatic nervous system. The autonomic nervous system provides involuntary control of visceral function and is divided into two parts: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is activated during stressful situations, preparing the animal for the “fight or flight” response. The parasympathetic nervous system is active during periods of rest. The sensory somatic nervous system consists of cranial and spinal nerves that carry sensory information from the skin and muscles to the central nervous system, and motor commands from the central nervous system to the muscles.

Unless otherwise stated, Biological Concepts by Charles Molnar and Jane Gair – 1st Edition Canadian Edition is licensed under the Creative Commons Attribution 4.0 International License. The nervous system is divided into central nervous system and peripheral nervous system. The central nervous system (CNS) consists of the brain and spinal cord, while everything else remains in the peripheral nervous system (PNS).

Peripheral Neuropathy: What It Is, Symptoms & Treatment

The peripheral nervous system itself is divided into two systems: the somatic nervous system and the autonomic nervous system. Each system consists of 2 components:

The somatic nervous system of the PNS is responsible for the voluntary, conscious control of skeletal muscles (effectors). Its afferent arm connects sensory receptors on the body surface or deep within the body to associated processing circuits, while the efferent arm directly controls skeletal muscles via motor nerves.

The autonomic (visceral) nervous system controls the body’s internal functions and operates largely unconsciously. These visceral functions include heart rate regulation, digestion, salivation, urination, digestion, and more. The afferent (sensory) arm of the system includes receptors that monitor arterial pressure, levels of carbon dioxide and oxygen in the blood, or the chemical composition of the contents of the gastrointestinal tract. The efferent arm of the system can be further divided into parasympathetic (PSNS) and sympathetic (SNS) components, which control many smooth muscles and glands.

Central And Peripheral Nervous System Functions

The enteric nervous system is classified as a separate component of the autonomic nervous system, and is sometimes even considered a third separate branch of the PNS.

Which System Is Composed Of The Spinal Cord And Peripheral Nerves?

The SNS and PSNS are branches of the autonomic nervous system. This

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