Biod 103 Medterm Mod4 Notes

• : Nervous System In this module, we will discuss the nervous system and the five special senses. In addition, we will be covering the endocrine system. The nervous system, as discussed in Module 2, is our command center. Its primary function is to coordinate the systems to maintain homeostasis. The nervous system can be divided by location as well as function. Anatomically speaking, this system can be divided into the central nervous system (made up of the brain and the spinal cord) and the peripheral nervous system (made up of 12 cranial nerves and 31 pairs of spinal nerves.) The functional divisions are the somatic nervous system (innervates skeletal muscle) and the autonomic nervous system (innervates visceral, smooth, and cardiac muscles). Within the autonomic system there is the sympathetic system (fight or flight) and parasympathetic system (rest and digest). The Brain The brain is the control center for all body functions. It is housed within the skull and weighs between 2.5-4 lb. The cerebrum makes up the majority of the brain’s body and is divided into right and left hemispheres. Each hemisphere controls the contralateral (or opposite) side of the body (i.e. the right side of the brain controls the left side of the body). The outer surface of the brain, or the cerebral cortex, is made up of gray matter. This is the command center for our special senses as well as movement and thought processes. Under the gray matter lies the inner brain, or the white matter. The gray matter can be divided into four lobes: 1. frontal lobe – the control center for voluntary movement, judgement, reasoning, and impulse inhibition 2. occipital lobe – the control center for visual perception, association, and visual memory 3. parietal lobe – collects and organizes sensations of pain, touch, movement, and position 4. temporal lobe – control center for auditory and visual memory as well as language development In the very center of the cerebrum are spaces called ventricles. These spaces carry cerebrospinal fluid (CSF). This fluid flows around the brain and spinal cord and acts as a protective barrier. CSF can be withdrawn for neurologic testing and to relieve pressure on the brain. The cerebellum (a.k.a. the hindbrain) is located posterior and inferior to the cerebrum. Its function is to coordinate voluntary movement and maintain normal body balance. The brainstem connects the brain to the spinal cord. The Spinal Cord The spinal cord is the relay station between the brain and the rest of the body. It runs from the brain stem to the second lumbar vertebra. The spinal cord’s primary function is to carry impulses between the brain and the body. Meninges are three layers of connective tissue that surround the brain and spinal cord for protection. They are listed below. 1. dura mater – outermost, thick connective tissue containing channels to allow blood flow to the brain 2. arachnoid membrane - middle layer of the meninges 3. pia mater – delicate connective tissue with a rich supply of blood vessels. Between the dura mater and the arachnoid membrane is the subdural space, which contains more blood vessels. Between the arachnoid membrane and the pia mater is the subarachnoid space, which contains CSF. The peripheral nervous system is comprised of the cranial nerves located around the brain stem and the spinal nerves, which are named by the direction of their impulse. Afferent nerves (or sensory nerves) carry information from the body to the brain to be interpreted for further action. These nerves carry information from receptors in the skin, eyes, ears, and nose. Efferent (or motor nerves) carry information from the central nervous system to the body to produce a response. The following tables represent root words and common pathologies that relate to the nervous system. Please note that many of these root words are review from Module 1; however, you should also be familiar with new words specific to this system. Table 4.1: Common Root Words Related to the Nervous System and Their Meanings Root Word Meaning Cerebell (o) Cerebellum Cerebr (o) Cerebrum Encephal (o) Brain Kinesi (o) Movement Mening (o) Meningi (o) Meninges Myel (o) Spinal cord Neur (o) Nerve Thalam (o) Thalamus Ventricul (o) Ventricles