L9. Nervous System.ppt
- 1. • The majority of the nervous system is tissue made up of two classes of cells: neurons and neuroglia. • Neurons: communicate within the body by transmitting electrochemical signals. • The cell body is the roughly round part of a neuron that contains the nucleus, mitochondria, and most of the cellular organelles. • Small tree-like structures called dendrites extend from the cell body to pick up stimuli from the environment. • Long transmitting processes called axons extend from the cell body to send signals onward to other neurons or effector cells in the body. 1
- 2. There are 3 basic classes of neurons: • Afferent neurons. Also known as sensory neurons, transmit sensory signals to the central nervous system from receptors in the body. • Efferent neurons. Also known as motor neurons, transmit signals from the central nervous system to effectors in the body such as muscles and glands. • Interneurons. form complex networks within the central nervous system-- integrate information received from afferent neurons and to direct the function of the body through efferent neurons. 2
- 3. • Neuroglia. Neuroglia, also known as glial cells, act as the “helper” cells of the nervous system. • Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and insulate the neuron. 3
- 4. 5 Organization of Your Body Organization Structure Diagram Smallest Level Largest Level
- 5. Organization of Your Body 3. Organs: are combinations of different tissues that form a structural and functional UNIT. Any organ that is essential to life is called a vital organ. Examples: • Heart - Pumps blood throughout the body. • Liver - Removes toxins from the blood, produces chemicals that help in digestion. • Lungs - Supplies oxygen to the blood and removes CO2 from blood. • Brain - The control center of the body.
- 6. Organization of Your Body Organ systems: are groups of organs that cooperate to perform the major activities of the body. -The vertebrate body contains 11 principal organ systems. 6
- 7. The 11 Human Body Systems The 11 human body systems are as follows: -- nervous system -- integumentary system -- respiratory system -- digestive system -- excretory system -- skeletal system -- muscular system -- circulatory system -- endocrine system -- reproductive system -- lymphatic (immune) system .
- 8. THE NERVOUS SYSTEM • Consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. • Together, these organs are responsible for the control of the body and communication among its parts. 8
- 9. CNS- Central Nervous System: where information is evaluated and decisions made: • Brain • Spinal Cord PNS- Peripheral Nervous System : Monitors conditions inside and outside of the body and send this information to the CNS. • Nerves • Sense Organs
- 10. • Peripheral Nervous System • Somatic Nervous System: The somatic nervous system (SNS) is a division of the PNS that includes all of the voluntary efferent neurons. • Eg: stimulating skeletal muscles in the body. • Autonomic Nervous System: The autonomic nervous system (ANS) is a division of the PNS that includes all of the involuntary efferent neurons. • Eg: cardiac muscle tissue, and glandular tissue. • There are 2 divisions of the autonomic nervous system in the body: the sympathetic and parasympathetic divisions. • Sympathetic. forms body’s “fight or flight” response to stress, danger, excitement, exercise, emotions, and embarrassment. The sympathetic division increases respiration and heart rate, releases adrenaline and other stress hormones, and decreases digestion to cope with these situations. • Parasympathetic. forms body’s “rest and digest” response when the body is relaxed, resting, or feeding. The parasympathetic works to undo the work of the sympathetic division after a stressful situation. Among other functions, the parasympathetic division works to decrease respiration and heart rate, increase digestion, and permit the elimination of wastes. 10
- 11. Brain • It is one of the largest organs in the body and coordinates most body activities. • It is the center for all thought, memory, judgment, and emotion. • Each part of the brain is responsible for controlling different body functions, such as temperature regulation and breathing. • Approximately 100 billion neurons of the brain form the main control centre.
- 12. Cerebrum • It is the largest section of the brain • It is located in the upper portion of the brain and is the area that processes thoughts, judgment, memory, problem solving, and language. • The outer layer of the cerebrum is the cerebral cortex, which is composed of folds of gray matter. • The cerebrum is subdivided into the left and right halves called cerebral hemispheres. • Each hemisphere has 4 lobes.
- 13. Lobes of Cerebrum • 1. Frontal lobe: controls motor function, personality, and speech • 2. Parietal lobe: receives and interprets nerve impulses from sensory receptors and interprets language. • 3. Occipital lobe: controls vision. • 4. Temporal lobe: controls hearing and smell
- 14. Cerebellum • Second largest portion of the brain • Located beneath the cerebrum • Aids in coordinating voluntary body movements and maintaining balance and equilibrium • Refines the muscular movement that is initiated in the cerebrum
- 15. Brain Stem • Medulla oblongata—most inferior positioned portion of the brain; it connects the brain to the spinal cord. • process involuntary body functions related to homeostasis. • The cardiovascular centre of the medulla monitors blood pressure and oxygen levels and regulates heart rate to provide sufficient oxygen supplies to the body’s tissues
- 16. • Spinal Cord • is a long, thin mass of bundled neurons. • carries information through the vertebral cavity of the spine from the medulla oblongata to the lumbar region of the spine. • In the lumbar region, the spinal cord separates into a bundle of individual nerves called the cauda equina. • 16
- 17. Nerves • Nerves are bundles of axons in the peripheral nervous system (PNS) that act as information highways to carry signals between the brain and spinal cord and the rest of the body. • Afferent, Efferent, and Mixed Nerves.. • Nerves that carry information from sensory receptors to the central nervous system only are called afferent nerves. • Efferent nerves, carry signals only from the central nervous system to effectors such as muscles and glands. • Finally, some nerves are mixed nerves that contain both afferent and efferent axons. 17
- 18. • Cranial Nerves. Extending from the inferior side of the brain are 12 pairs of cranial nerves. • The cranial nerves provide a direct connection to the brain for the special sense organs, muscles of the head, neck, and shoulders, the heart, and the GI tract. • Spinal Nerves. Extending from the left and right sides of the spinal cord are 31 pairs of spinal nerves. • The spinal nerves are mixed nerves that carry both sensory and motor signals between the spinal cord and specific regions of the body. 18
- 19. Meninges: The meninges are the protective coverings of the central nervous system (CNS). • Dura mater: is the thickest, toughest, and most superficial layer of meninges. Dura mater protects the CNS from external damage, contains the cerebrospinal fluid that surrounds the CNS, and provides blood to the nervous tissue of the CNS. • Arachnoid mater. is much thinner and more delicate than the dura mater. It lines the inside of the dura mater and contains many thin fibers that connect it to the underlying pia mater. • Pia mater: is a thin and delicate layer of tissue that rests on the outside of the brain and spinal cord. Containing many blood vessels that feed the nervous tissue of the CNS, the pia mater penetrates the brain as it covers the entire surface of the CNS. • Cerebrospinal Fluid: • The space surrounding the organs of the CNS is filled with a clear fluid known as cerebrospinal fluid (CSF). • Newly created CSF flows through the inside of the brain in hollow spaces called ventricles and through a small cavity in the middle of the spinal cord called the central canal. • • CSF absorbs shocks between the brain and skull and between the spinal cord and vertebrae. 19
- 20. • Sense Organs: • All of the bodies’ many sense organs are components of the nervous system. • What are known as the special senses—vision, taste, smell, hearing, and balance—are all detected by specialized organs such as the eyes, taste buds, and olfactory epithelium. • Sensory receptors for the general senses like touch, temperature, and pain are found throughout most of the body. • All of the sensory receptors of the body are connected to afferent neurons that carry their sensory information to the CNS to be processed and integrated. 20
- 21. FUNCTIONS • The nervous system has 3 main functions: sensory, integration, and motor. • Sensory. The sensory function of the nervous system involves collecting information from sensory receptors that monitor the body’s internal and external conditions. • These signals are then passed on to the central nervous system (CNS) for further processing. • Integration. The process of integration is the processing of the many sensory signals that are passed into the CNS at any given time. • These signals are evaluated, compared, used for decision making, discarded or committed to memory as deemed appropriate. • Integration takes place in the gray matter of the brain and spinal cord and is performed by interneurons. • Motor. Once the networks of interneurons in the CNS evaluate sensory information and decide on an action, they stimulate efferent neurons. • Efferent neurons carry signals from the gray matter of the CNS through the nerves of the peripheral nervous system to effector cells. • The effector may be smooth, cardiac, or skeletal muscle tissue or glandular tissue. • The effector then releases a hormone or moves a part of the body to respond to the stimulus. 21