Human Nervous System PDF

Central and Peripheral Nervous System Neal Whelan Regions of the Central Nervous System Brain - Brain Stem Spinal Cord How many neuron’s do human have? The nervous system consists of two kinds of cells: Neurons Glia. Neurons recieve information and transmit...

Central and Peripheral Nervous System Neal Whelan Regions of the Central Nervous System Brain - Brain Stem Spinal Cord How many neuron’s do human have? The nervous system consists of two kinds of cells: Neurons Glia. Neurons recieve information and transmit it to other cells. The adult human brain contains on average approximately 86 Billion neuron’s. There are slight variations between humans.  Tissue in the central nervous: Is divided into either white matter or grey matter. White matter regions are comprised of axons. It appears white due to the myelin sheath on the axons. Grey matter regions are comprised of cell bodies and dendrites. Grey matter is the location of most synapses. The Brain It is the largest structure in the human body to be almost entirely encased in a hard, bony structure - the skull. Indicating how critical it is to protect from injury Weighs roughly 1.5kg of pink beige substance with a jelly like consistency and with a folded appearance. Observations resulted in a number of fissures or sulci (sigular sulcus) that result from the folding. The Cerebral Cortex could subdivided into regions based on their location relative to these sulci. The brain is broken down into 4 Parts, or Lobes: Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe Cerebral Hemisphere Neuroscientists use common neuroanatomical terms to denote location, organisation, and function. Below are a standard set of anatomical directional terms used to describe the location of different regions. Anterior: In front of Posterior: Behind Superior: Above Inferior: Below Directional Terms Anterior: In front of; toward the face Posterior: Behind; toward the back Superior: Above; toward the head Inferior: Below; toward the feet Medial: Toward the middle Lateral: Toward the edge Dorsal: Toward the top of the brain or the back of the spinal cord Ventral: Toward the bottom of the brain or the front of the spinal cord Rostral: Toward the front of the brain or the top of the spinal cord Caudal: Toward the back of the brain or the bottom of the spinal cord Anatomical Planes Sagittal Plane: The sagittal plane is a vertical plane which passes through the body longitudinally. It divides the body into a left section and a right section. A specific sagittal plane is the median sagittal plane – which passes down the midline of the body, separating it into equal halves. Coronal Plane: The coronal plane is a vertical plane which also passes through the body longitudinally – but perpendicular (at a right angle) to the sagittal plane.It divides the body into a front (anterior) section and back (posterior) section. Transverse Plane: The transverse plane is a horizontal plane. It is perpendicular to both the sagittal and coronal planes, and parallel to the ground.It divides the body into an upper Structural differences: Your brain and spinal cord make up your Central Nervous System. Your brain uses your nerves to send messages to the rest of your body. Each nerve has a protective outer layer called myelin. Myelin insulates the nerve and helps the messages get through. Peripheral nervous system: Your peripheral nervous system consists of many nerves that branch out from your CNS all over your body. This system relays information from your brain and spinal cord to your organs, arms, legs, fingers and toes. Your peripheral nervous system contains your: Somatic nervous system - conveys messages from the sense organs to the CNS and to muscles Autonomic nervous system - controls heart, intestines and other organs. Sympathetic and Parasympathethic Nervous System The Sympathetic Nervous System: A network of nerves that prepares the organs for rigorous activity Increases heart rate, blood pressure, respiration, and so on. (“fight or flight” response) Composed of ganglia on the left and right of the spinal cord.Ganglia is the plural of the word ganglion. Ganglia are clusters of nerve cell bodies found throughout the body. They are part of the peripheral nervous system and carry nerve signals to and from the central nervous system. Imagine two trucks suddenly appearing in front of you as you round a curve on a two-lane road. One is passing the other and you only have time enough to slam on the brakes and quickly pull over onto the side of the road. The two trucks roar by, your heart is beating fast, you feel ill, maybe you vomit. Your sympathetic nervous system just kicked in globally preparing you for emergency.  The Parasympathetic Nervous System: Facilitates vegetative and nonemergency responses - relaxed state. Decreases functions increased by the sympathetic nervous system Composed of long preganglion axons extending from the spinal cord and short postganglionic fibers that attach to the organs themselves Dominant during our relaxed states Digestion is good example Information Transfer The central nervous system (CNS) is comprised of the brain and the spinal cord. The peripheral nervous system (PNS) is comprised of the cranial and spinal nerves. When information flow is described in the nervous system, it can either be afferent communication, meaning it is moving from the periphery to the brain, or efferent communication, meaning it is moving from the brain to the periphery.