Chapter 16- Nervous Tissue .docx - Chapter 16 Nervous...

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Chapter 16: Nervous Tissue Introduction The nervous system and the endocrine system are the body’s major control and integrating centers Neurology is the study of the normal functioning and disorders of the nervous system Organization of the Nervous System The nervous system consists of two major divisions o Central Nervous System (CNS) Brain and spinal cord Processes many different kinds of incoming sensory information Source of thoughts, emotions, and memories Most nerve impulses that stimulate muscles to contract and glands to secrete originate in the CNS Contains motor (efferent) neurons- reaction o Peripheral Nervous System (PNS) Cranial nerves that emerge from the brain, and spinal nerves that emerge from the spinal cord Also, ganglia, enteric plexuses and sensory receptors These structures link all parts of the body to the CNS Contains sensory (afferent) neurons - information coming in
Introduction The nervous system includes: o Brain Enclosed and protected by the skull in the cranial cavity and contains about 100 billion neurons o Spinal cord Enclosed and protected by the bones of the vertebral column in the vertebral canal and contains about 100 million neurons Brain and spinal cord are continuous through foramen magnum o Cranial nerves (and their branches) Emerge from the base of the brain Consists of twelve parts (right and left) o Spinal nerves (and their branches) Emerge from the spinal cord, each serving a specific region on the right or left side of the body o Ganglia Small masses of nervous tissue, consisting primarily of neuron cell bodies Located outside the brain and spinal cord Associated closely with cranial and spinal nerves o Enteric plexuses Located in the walls of organs of the gastrointestinal tract, extensive network of neurons Help regulate the digestive system o Sensory receptors Monitor changes in the internal and external environment
Ex: skin detects touch sensations Functional Organization of the Nervous System Sensory (input) function- sensory receptors o Detect stimuli either externally or internally Internally- increase of blood pressure Externally- raindrops on arm o Sensory (afferent) neurons carry this sensory information into the brain and spinal cord through cranial and spinal nerves o Then send it to the integrating system Integrative (control) function- interneurons o Processes sensory information by analyzing and storing some of it and by making decisions for appropriate responses Interpreting the information o Perception occurs in the brain and is the conscious awareness of sensory stimuli o Interneurons which interconnect with other neurons and make up the majority of the CNS Motor (output) function- motor or efferent neurons o How we move or respond to integrated sensory information Reaction Blinking of the eye, the way we talk/walk o Motor (efferent) neurons carry information from the brain toward the spinal cord o Out of the brain and spinal cord to effectors (muscles and glands) through cranial and spinal nerves

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