Somatic motor efferents

Lateral efferents of the MPOA innervate septum, amygdala, other hypothalamic regions, ventral tegmental area (VTA) of the midbrain, and midbrain central gray matter (Numan, 1986). Studies have shown that the MPOA-VTA-basal ganglia (BG) circuit is believed to be of importance in maternal behavior because the BG is a major component of the extrapyramidal system (EPS) (Numan, 1986). Perhaps MPOA neurons relevant to maternal behavior via the BG to EPS promote the somatic-motor processes underlying maternal responsiveness (Numan, 1986). 

The nervous system is conventionally divided into the central nervous system (CNS the brain and spinal cord) and the peripheral nervous system (PNS neuronal tissues outside the CNS). The motor (efferent) portion of the nervous system can be divided into two major subdivisions autonomic and somatic. The autonomic nervous system (ANS) is largely independent (autonomous) in that its activities are not under direct conscious control. It is concerned primarily with visceral functions such as cardiac output, blood flow to various organs, and digestion, which are necessary for life. The somatic subdivision is largely concerned with consciously controlled functions such as movement, respiration, and posture. Both systems have important afferent (sensory) inputs that provide information regarding the internal and external environments and modify motor output through reflex arcs of varying size and complexity. 

The somatic nervous system is composed of sensory afferents and motor efferents and serves to perceive external states and to modulate appropriate body responses. The autonomic nervous system (ANS), together with the endocrine system, controls the milieu interieur. It adjusts internal organ functions to the changing needs of the organism. The ANS operates largely autonomously, beyond voluntary control, at the subconscious level. Its central components reside in the hypothalamus, brain stem, and spinal cord. The ANS has sympathetic and parasympathetic branches. Both are made up of afferent, mainly in the vagus nerve, and efferent fibers. 

The efferent portion of the peripheral nervous system can be further divided into two major functional subdivisions, the somatic and autonomic systems (see Figure 3.1). The somatic efferents are involved in voluntarily controlled functions such as contraction of the skeletal muscles in locomotion. The autonomic system functions involuntarily to regulate the everyday needs and requirements of the body without the conscious participation of the mind. It is composed primarily of visceral motor (efferent) neurons that innervate smooth muscle of the viscera, cardiac muscle, vasculature and the exocrine glands. 

The peripheral nervous system (those nerves outside the central nervous system or CNS) of vertebrates is made up of both sensory (afferent) and motor (efferent) nerves (figure). Each of these includes a bundle of nerve cells that connect to different sensors and actuators in the body. Motor nerves can be either somatic (mostly voluntary) or autonomic (mostly involuntary). 

The afferent division carries sensory information toward the CNS and the efferent division carries motor information away from the CNS toward the effector tissues (muscles and glands). The efferent division is further divided into two components (1) the somatic nervous system, which consists of motor neurons that innervate skeletal muscle and (2) the autonomic nervous system that innervates cardiac muscle, smooth muscle, and glands. 

Transmission of impulses to somatic efferent motor neurons in spinal cord to initiate voluntary contraction of skeletal muscle... 

The nervous system is divided into two parts the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all afferent (sensory) neurons, which carry nerve impulses into the CNS from sensory end organs in peripheral tissues, and all efferent (motor) neurons, which carry nerve impulses from the CNS to effector cells in peripheral tissues. The peripheral efferent system is further divided into the somatic nervous system and the autonomic nervous system. The effector cells innervated by the somatic nervous system are skeletal muscle cells. The autonomic nervous system innervates three types of effector cells (1) smooth muscle, (2) cardiac muscle, and (3) exocrine glands. While the somatic nervous system can function on a reflex basis, voluntary control of skeletal muscle is of primary importance. In contrast, in the autonomic nervous system voluntary control can be exerted, but reflex control is paramount. 

The efferent somatic nervous system differs from the autonomic system in that a single myelinated motor neuron, originating in the CNS, travels directly to skeletal muscle without the mediation of ganglia. As noted earlier, the somatic nervous system is under voluntary control, whereas the autonomic is an involuntary system. 

Directional Afferent system by sensory neurons, which carry impulses from a somatic receptor to the CNS. Efferent system by motor neurons, which carry impulses from the CNS to an effector. Relay system by interneurons (also called relay neurons ), which transmit impulses between the sensory and motor neurons (in both the CNS and the PNS). 

The nervous system (Fig. 1) consists of the central nervous system (CNS with brain and spinal cord) and the peripheral system (with afferent sensory and efferent motor nerves), which regulate all aspects of bodily function and is staggering in its complexicity. Another distinction is between the somatic (sensoric system, innervation of skeletal muscles) and the autonomic nervous system (heart and blood circulation respiration motility of the gastrointestinal tract, smooth muscles of gall and urinary bladder, ureter, uterus, secretion of glands). The autonomic nervous system is further divided into a sympathetic and... 

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