Introduction to Physiology: Nervous System PDF

The Introduction of PHYSIOLOGY Nervous system  Brain Structure and Chemistry 1. Communication in the nervous system. To truly understand brain structure and chemistry, it is a good idea to understand how communication occurs within the nervous system. See Figure 2.1 below. S...

The Introduction of PHYSIOLOGY Nervous system  Brain Structure and Chemistry 1. Communication in the nervous system. To truly understand brain structure and chemistry, it is a good idea to understand how communication occurs within the nervous system. See Figure 2.1 below. Simply: 1.Receptor cells in each of the five sensory systems detect energy. 2.This information is passed to the nervous system due to the process of transduction and through sensory or afferent neurons, which are part of the peripheral nervous system. 7 3. The information is received by brain structures (central nervous system) and perception occurs. 4. Once the information has been interpreted, commands are sent out, telling the body how to respond (Step E), also via the peripheral nervous system. 8  9 Figure Communication in the Nervous System  Please note that we will not cover this process in full, but just the parts relevant to our topic of psychopathology. 2.2.1.2. The nervous system. The nervous system consists of two main parts – the central and peripheral nervous systems. The central nervous system (CNS) is the control center for the nervous system, which receives, processes, interprets, and stores incoming sensory information. It consists of the brain and spinal cord. The peripheral nervous system consists of everything outside the brain and spinal cord. It handles the CNS’s input and output and divides into the somatic and autonomic nervous systems. The somatic nervous system allows for voluntary movement by controlling the skeletal muscles and carries sensory information to the CNS. The autonomic nervous system regulates the functioning of blood vessels, glands, and internal organs such as the bladder, stomach, and heart. It consists of sympathetic and parasympathetic nervous systems. The sympathetic nervous system is involved when a person is intensely aroused. It provides the strength to fight back or to flee 10 11  The neuron. The fundamental unit of the nervous system is the neuron, or nerve cell (See Figure 2.3). It has several structures in common with all cells in the body. The nucleus is the control center of the body and the soma is the cell body. In terms of distinctive structures, these focus on the ability of a neuron to send and receive information. The axon sends signals/information to neighboring neurons while the dendrites, which resemble little trees, receive information from neighboring neurons. 12  Note the plural form of dendrite and the singular form of axon; there are many dendrites but only one axon. Also of importance to the neuron is the myelin sheath or the white, fatty covering which: 1) provides insulation so that signals from adjacent neurons do not affect one another and, 2) increases the speed at which signals are transmitted. The axon terminals are the end of the axon where the electrical impulse becomes a chemical message and passes to an adjacent neuron. 13  Though not neurons, glial cells play an important part in helping the nervous system to be the efficient machine that it is. Glial cells are support cells in the nervous system that serve five main functions: 1.They act as a glue and hold the neuron in place. 2.They form the myelin sheath. 3.They provide nourishment for the cell. 4.They remove waste products. 5.They protect the neuron from harmful substances. 14 Figure 2 The Structure of the Neuron 15. Neurotransmitters. What exactly are some of the neurotransmitters which are so critical for neural transmission, and are essential to our discussion of psychopathology? 16  Dopamine – controls voluntary movements and is associated with the reward mechanism in the brain  Serotonin – regulates pain, sleep cycle, and digestion; leads to a stable mood, so low levels leads to depression  Endorphins – involved in reducing pain and making the person calm and happy  Norepinephrine – increases the heart rate and blood pressure and regulates mood  GABA – blocks the signals of excitatory neurotransmitters responsible for anxiety and panic  Glutamate – associated with learning and memory 17  2.2.1.6. The brain. The central nervous system consists of the brain and spinal cord; the former we will discuss briefly and in terms of key structures which include:  Medulla – regulates breathing, heart rate, and blood pressure  Pons – acts as a bridge connecting the cerebellum and medulla and helps to transfer messages between different parts of the brain and spinal cord  Reticular formation – responsible for alertness and attention  Cerebellum – involved in our sense of balance and for coordinating the body’s muscles so that movement is smooth and precise. Involved in the learning of certain kinds of simple responses and acquired reflexes.  Thalamus – the major sensory relay center for all senses except smell 18  Hypothalamus – involved in drives associated with the survival of both the individual and the species. It regulates temperature by triggering sweating or shivering and controls the complex operations of the autonomic nervous system  Amygdala – responsible for evaluating sensory information and quickly determining its emotional importance  Hippocampus – our “gateway” to memory. Allows us to form spatial memories so that we can accurately navigate through our environment and helps us to form new memories about facts and events 19