Module 3: The Nervous System PDF

Republic of the Philippines **EULOGIO "AMANG" RODRIGUEZ** **INSTITUTE OF SCIENCE AND TECHNOLOGY** **C a v i t e C a m p u s** General Mariano Alvarez, Cavite **LESSON 3: *NERVOUS SYSTEM*** **Introduction:** Man is a biological, social and psychological being. His behavior is governed not only...

Republic of the Philippines **EULOGIO "AMANG" RODRIGUEZ** **INSTITUTE OF SCIENCE AND TECHNOLOGY** **C a v i t e C a m p u s** General Mariano Alvarez, Cavite **LESSON 3: *NERVOUS SYSTEM*** **Introduction:** Man is a biological, social and psychological being. His behavior is governed not only by psychological factors but also biological determinants. When man is confronted by a stressful stimulus, or by an emotion-provoking event, his heart beats faster, his blood pressure rises, he may blush or may manifest fine but continuous spasmodic contractions. These involuntary responses elicited by the stressful stimulus are controlled by the nervous system. **Objectives:** At the end of this chapter the students will be able: - Know the importance of the nervous system in understanding human behavior - Distinguish the division of the nervous system - Discuss the different parts of the brain and its function - Consider the biological approach as a major contributor to explain behavior **Neuron** - ***Basic functioning unit/structural unit of the nervous system*** - Only neurons have the specialized ability to transmit nerve impulses - Each neuron is a living cell. **Parts of the Neuron** **AXON** -- conducts neural impulses away from the cell body towards other neurons **DENDRITES** -- received impulses and carry them towards the cell body **CELL BODY OR SOMA** -- it is regarded as the tropic center, the cell body serves as the center of nourishment **MYELIN SHEATH** -- A white fatty layers of cell which serve as an insulator and aids in the conduction of impulses \*At the peripheral endings of the axon is a branch terminal portion which is called the end-brush. The end brush terminates the knob-like structure known as **synaptic knobs** or **synaptic terminal**. Within the synaptic knobs are synaptic vesicles which contains **neurotransmitters.** ***Neurotransmitters*** are chemical substances which plays a significant role in the transmission of the nerve impulses from one neuron to the next neuron at the junction called **synapses.** +-----------------------------------+-----------------------------------+ | **NEUROTRANSMITTER** | **EFFECTS ON BEHAVIOR** | +===================================+===================================+ | Acetylcholine | - Facilitate in learning and | | | memory | |   | | | | - Deficiency in Ach disrupt in | | | learning and memory | +-----------------------------------+-----------------------------------+ | Norepinephrine | - Too little of norepinephrine | | | will lead to depression | | | | | | - Too much cause hyperactivity | +-----------------------------------+-----------------------------------+ | Dopamine | - Oversupply of dopamine may | | | lead to schizophrenic | | | reaction | | | | | | - Undersupply causes | | | Parkinson's disease | +-----------------------------------+-----------------------------------+ | Serotonin | - Lack of serotonin produces | | | insomnia | | | | | | - Prevent dreaming in waking | | | state | +-----------------------------------+-----------------------------------+ | GABA (Gamma Aminobutyric acid) | - Decrease activity of nerves | | | and may decrease level of | | | anxiety | +-----------------------------------+-----------------------------------+ **Types of Neurons** - It is classified according to their function a. Sensory b. Motor c. Interneuron 1. **Sensory (afferent)** "Incoming neuron" - Neurons sends neural impulses from the brain to the effectors located in the peripheral organ such as muscles and glands - Receives stimuli and carry them to the brain for sensation, interpretation and perception 2. **Motor (efferent)** "Carrying out" - Sends efferent signals for muscular contractions and glandular organ secretion - It relays message from the brain to the muscles or glands. - A motor neuron is directly responsible for each movement and responses we make. 3. **Interneurons (association neurons)** - Located at the brain and spinal cord. - They connect the impulses from the axon fibers of the sensory neuron to the dendrite fibers of the motor neuron. - It conducts nerve/neural impulses from a sensory neuron to a motor nerve cell **DIVISION OF NERVOUS SYSTEM** The nervous system is divided into two main divisions: - **CNS** -- made of the brain and spinal cord - **PNS** -- further subdivided into somatic and autonomic 1. Consisting of nerve fibers or bundle of axons found outside the brain and spinal cord 2. It connects the central nervous system to the rest of the body parts 3. **Somatic** -- composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves 4. **Autonomic** -- It is made up of **[sympathetic]** and **[parasympathetic]** **THE CENTRAL NERVOUS SYSTEM (CNS)** **CNS** - The CNS is composed of the **brain** and **spinal cord** **Spinal Cord** - A tube of nerve tissue located inside our backbone. - It serves as a pathway of nerve impulses going or coming from brain. - A series of interconnected neurons (nerve cells) extending from the brain down through the center of the back. 8 pairs of cervical nerves 12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nerve [Functions of spinal cord] 1. It serves as a pathway through which nerve impulses from sensory organs(affectors) pass to the brain (effector) return to the muscles and glands 2. It governs certain type of reflex movement. It processes sensory impulses and send impulses to the effectors without the assistance of the brain **Reflex** -- These are automatic response to a stimulus by some part of the body. **Brain** - The master organ of the body. It is the coordinator and the director of conscious and unconscious activity. The brain has different centers responsible for the different act. - The largest part of the nervous system that is protected by the skull. - Weighs 3 pounds and contains 90%of body neurons [The function of the brain is to:] - Identify - Organize - Interpret - Respond To the experience of sensory stimulation **Structures of the Brain** The brain is composed of 3 concentric layers. Neuroanatomists prefer to divide into: - **Hindbrain** - **Midbrain** - **Forebrain** A. **[Hindbrain]** - Most rearward portion of the brain - ***Medulla*** 5. Located just above the spinal cord 6. Controls respiration, digestion, and circulation 7. It controls involuntary muscles that are associated with the basic physical rhythm, e.g. breathing and heartbeat, swallowing, sneezing, coughing, vomiting - ***Pons*** 8. Just above the medulla and in front of the cerebellum 9. Act as a transmitter of motor information permitting the coordination of muscles and the integration of movement and between the right and left part of the body 10. Contains nerve fibers from both side of cerebellum as well as the tracts of sensory and motor nerve fibers that connect the upper brain to the spinal cord (relay station for signal passing from one part of the brain) - ***Cerebellum*** 11. Found above the medulla and behind the pons 12. Governs body balance, posture and muscular coordination (it is due to the cerebellum that one can walk in a straight line) 13. Damage will result to different/jerky movement and halting/slurring speech B. **[Midbrain]** - The smallest and least differentiated structure of the brain stem - Tracts between the cerebrum and spinal cord and functions as part of overall conduction system. - It also plays a special role of processing nerve impulses which are involved in vision and audition. C. **[Forebrain]** - The largest of the 3 division of the brain and occupies the entire upper portion of the skull (1/2 of the cavity of the skull) - Responsible for the highest functions of thought, voluntary action and consciousness. *The 3 major structure of the forebrain* ***Cerebrum*** - The largest and the most important part of human brain - It focused on the biological structures of the body that are mostly involved in understanding human behavior. - The main area of the forebrain governs emotion, learning and thinking and remembering, a sense of perception - *Cerebral cortex* -The outer layer of the cerebrum - ***Thalamus*** - Interprets and sorts the sensory and motor impulses that travel to and from cerebrum - Acts primarily as a relay station, mostly messages concerning sensory information - ***Hypothalamus*** - Collection of nerve cells that control body temperature, metabolism, hunger and thirst - Plays 2 important roles: - Homeostasis/Equilibrium -- internal biological balance - Produce and regulates behavior, which is important for survival - Hypothalamus is connected to a diffuse system of highly interrelated structure nerves called **LIMBIC SYSTEM** - ***LIMBIC SYSTEM*** - From the Latin word " border" - Lies between the control core of the brain and the cortex. - Allows us to control our instinctive drives; Plays an important role in our motivation and emotional needs [3 structure of the limbic system ] 14. Hippocampus -- particularly involved with memory, especially the formation of long-term memory. 15. Amygdala -- the main area involved with emotion such as anger, aggression and fear. 16. Septum/Septal area -- a partition or division in the brain. - ***Reticular Activating System (RAS)*** - A group of neurons that occupy a portion of hindbrain and midbrain - It serves as an arousal system - It arouses the body to prepare it for appropriate action and screens out background information **Hemisphere of the brain** The cerebrum consist of two halves/hemispheres (left and right) - The **right hemisphere** of the cerebrum controls the sensory and motor activities in the left side of the body(vice versa) - The **left hemisphere** exercises control over the functions of the right side of the body - Connects the two brain hemisphere - This is a broad bundle of nerve fibers that coordinated the activities of the two hemisphere  **The 4 lobes of the brain** - Different surface areas of the cerebral cortex are responsible for specific experience or sensation 1. **Frontal lobe** - Responsible for primary motor function - They control the voluntary movement of the muscle of the skeleton 2. **Parietal lobe** - "Somatosensory area" - Body sense area, cortical center for the body senses 3. **Occipital lobe** - Important center of vision - Recognize form, movement, and distinguish hues and color 4. **Temporal lobe** - The principal area for translating auditory stimulation - Enables one to recognize volume, pitch, and quality of sound **AUTONOMIC NERVOUS SYSEM** **SYMPATHETIC NERVOUS SYSTEM (SNS)** -is one of major parts of the autonomic nervous system. Its general action is to mobilize the body\'s nervous system "**fight-or-flight"** response. It is, however, **constantly active at a basic level to maintain homeostasis.** **PARASYMPATHETIC NERVOUS SYSTEM (PNS)** is another division of the autonomic nervous system (ANS), The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously. To be specific, the parasympathetic system is responsible for stimulation of **\"rest-and-digest**\" **or \"feed and breed\"** activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation.