Chapter 11Functions of Nervous System • Nervous system is master controlling and communicating system of body • Cells communicate via electrical and chemical signals • Rapid and specific• Usually cause almost immediate responses 11.1 Functions of Nervous System (2 of 2) • Nervous system has three overlapping functions 1. Sensory input- taking in information2. Integration- control center3. Motor output – effector (muscles/glands)Organization of the Nervous System
Figure 11.3 Organization of the nervous system. The somatic nervous systemis composed of somatic motor nerve fibercs that conduct impulses from the CNS to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.The autonomic nervous system (ANS)is also called the involuntary nervous system.The ANSconsists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. Autonomic means “a law untoitself,” and because we generally cannot control such activities as the pumping of our heart or the movement of food through our digestive tract, the ANS is also called the involuntary nervous system.The sensory, or afferent, division (“carrying toward”) of the PNS consists of sensory nerve fibers (axons) that convey impulses to the central nervous system from sensory receptors located throughout the body.Somatic sensory fibers convey impulses from the skin, skeletal muscles, and joints (soma, body)
Visceral sensory fibers transmit impulses from the visceral organs (organs within the ventral body cavity)The motor, or efferent, division (“carrying away”) of the PNS consists of motor nerve fibers that transmit impulses from the CNS to effector organs.11.2 Neuroglia Somatic motor fibers carry information from the CNS to skeletal muscles. • Nervous tissue histology• Nervous tissue consists of two principal cell types Neuroglia (glial cells): support cells of the nervous systemNeurons (nerve cells): cells that conduct the nerve impulses The peripheral nervous system (PNS), the part of the nervous system outside the CNS, consists of cranial and spinal nerves carrying impulses to and from the brain and spinal cord.Neuroglia of the CNS (1 of 5) • Four main neuroglia support CNS neurons • Astrocytes • Microglial cells• Ependymal cells• Oligodendrocytes Neuroglia of the CNS (2 of 5) • Astrocytes• Most abundant, versatile, and highly branched of glial cells Cling to neurons, synaptic endings, and capillaries Brace neuronsGuide young neurons to intend location Control chemical environment (help establish blood brain barrier)Astrocytes play a role in making exchanges between capillaries and neurons, helping determine capillary permeability.