THE STRUCTURE OF THE NERVOUS SYSTEM By: Andrea Tremper Annabelle Afra Yarshar Kermue 1

Central Nervous System (CNS) The central nervous system is the part of the nervous system that consists of the brain and spinal cord. It is one of the two major divisions of the nervous system. 2

The brain is protected by the skull, while the spinal cord is protected by the vertebrae. The CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity. 3

The CNS is responsible for integrating, processing, and coordinating sensory data and motor commands. Sensory data convey information about conditions inside or outside the body. Motor commands control or adjust the activities of peripheral organs, such as skeletal muscles. The CNS- specifically the brain- is also the seat of higher functions, such as intelligence, memory, learning , and emotion 4

5

Peripheral Nervous System (PNS) The peripheral nerves include the 12 cranial nerves, the spinal nerves and roots. The Cranial Nerves are connected to the brain, while the spinal nerves are connected to the spinal cord. 6

The nerves in the peripheral nervous system connect the central nervous system to sensory organs, other organs of the body, muscles, blood vessels and glands. 7

The PNS is divided into afferent and efferent divisions. It delivers sensory information to the CNS and carries motor commands to peripheral tissues and systems. Bundles of axons, or nerve fibers, carry sensory information and motor commands in the PNS. The PNS is divided into afferent and efferent divisions. It is also divided into two major parts, the somatic nervous system and the automatic nervous system. 8

Peripheral Nerves 9

Afferent vs. Efferent 10

Afferent Neurons The afferent nerves bring sensory information to the CNS from receptors in peripheral tissues and organs. Receptors are sensory structures that detect changes in the internal environment or respond to the presence of a specific stimuli. 11

A touch or painful stimulus, for example, creates a sensation in the brain only after information about the stimulus travels there via afferent nerve pathways. Just outside the spinal cord, thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the dorsal root ganglion. Afferent neurons have a single long dendrite and a short axon, and a smooth and rounded cell body. 12

Efferent Nerves Also known as motor neurons, they carry nerve impulses away from the central nervous system to effectors such as muscles and glands. These target organs, which respond by performing an action, are called effectors. 13

The cell body of the motor neuron is satellite-shaped. The cell body of the efferent neuron is connected to a single, long axon and several shorter dendrites projecting out of the cell body itself. The cell body of the motor neuron is satellite-shaped. The motor neuron forms an electrochemical pathway to the effectors' organ or muscle. The Efferent division has both automatic and somatic components. 14

Somatic Nervous System (SNS) Controls skeletal muscle contractions which include both voluntary and involuntary contractions. Voluntary contractions are under conscious control, while involuntary actions are controlled at the subconscious level. 15

Automatic Nervous System (ANS) Also known as visceral motor system, it provides automatic regulation of smooth muscle, cardiac muscle, and glandular secretions at the subconscious level. The ANS includes a sympathetic division and a parasympathetic division, which commonly have antagonistic effects. 16

Somatic vs. Automatic 17

Sympathetic vs. Parasympathetic It increases the heart rate and blood pressure and also activates the body's mechanisms to provide immediate energy to face the stressful state. This system utilizes the body's energy resources just to prepare it for some upcoming stressful state. The parasympathetic system is rest and digest system. It increases the blood supply to gut and increases the digestion. It tries to restore the body's energy sources. 18

19

Bibliography Martini, H. Fredrick, Garrison, W, Claire, Welch, Kathleen, Hutchings, T. Ralph. (2006). Fundamentals of Anatomy & Physiology. The Spinal Cord, Spinal Nerves, and Spinal Reflexes. San Francisco, CA: Pearson Education, Inc. http://www.templejc.edu/dept/biology/RHicks/biol2404Int/cavities.gi http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html http://www.medterms.com/script/main/art.asp?articlekey=2667 20

Next Presentation

Marissa, Matt, Katelyn Period 4/5 Neurons Marissa, Matt, Katelyn Period 4/5

What is a Neuron? Cells in nervous system Transmit information Communicate chemically and electrically

Types of Neurons Sensory- Carry information from receptor cells to brain Motor- transmit information from brain to muscles Inter- communicates between neurons

Structure Dendrites- nerve impulses that are generated in short branch fibers Soma/cell body- signals from dendrites are joined and passed on Axon- central nervous system conduct impulses on hair like cytoplasmic extensions

Structure continued Initial segment- point of cell body emergence to point of myelin initiation Axon Hillock- the conical area of origin of the axon from the nerve cell body Telodendria- structures at the terminal branches of axon that contain neurotransmitters Synaptic terminal- a bulb at the end of the axon in which the neurotransmitter molecules are stored and released

Function Sensory Neurons Motor Neurons Delivers the information from the Sensory Receptors to the CNS. Motor Neurons Carry instructions from the CNS to the Peripheral Effectors in the Peripheral tissue, Organ, or Organ System.

Functions Continued. Neurons conduct impulses along the Nerve Fibers or Axons.

References Boeree, C. G., Dr. (2003). The Neuron. Retrieved February 4, 2010, from http://webspace.ship.edu/ cgboer/theneuron.html Initial segment. (2010). Retrieved February 3, 2010, from Farlex website: http://medical-dictionary.thefreedictionary.com/initial+segment Lefers, M. (2004, July 26). Synaptic Terminal. Retrieved February 3, 2010, from North Western University website: http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-S/ synaptic_terminal.html Neurons. (2009, December 27). Retrieved February 3, 2010, from http://users.rcn.com/ jkimball.ma.ultranet/BiologyPages/N/Neurons.html Telodendria . (2010). Retrieved February 4, 2010, from Farlex, Inc. website: http://www.definition-of.com/telodendria Van Wagner, K. (2010). What Is a Neuron? Retrieved February 4, 2010, from http://psychology.about.com/od/biopsychology/f/neuron01.htm

Next Presentation

The Classification of Neurons By Adam, Carly and Evan

Anaxonic The anaxonic neurons are located in the brain and in other special sense organs in the body. These neurons are small and it is hard to tell the difference between dendrites and axons.

Bipolar Neurons The small neurons have two distinct processes one is the dendritic process the other is the axon extending from the cell body. Are found only in sensory neurons. (ex. retina, olfactory, and auditory systems)

Unipolar Neuron These are the large neurons that have the cell body lying to one side of the continuous dendritic process and axon This makes it appear that the cytoplasmic process splits the axon into two portions A peripheral process takes the action potential to the cell body

Multipolar neurons Neurons that have more than three processes on their cell bodies are classified as a multipolar The processes contained extend from the soma. Multipolar neurons have one axon and multiple dendrites.

Sensory neurons Send information about the stimuli collected by sensory receptors (eyes, ears, nose, skin, tongue) to the central nervous system (brain)

Sensory Neurons (cont’d.) The cell bodies of sensory neurons are located in peripheral sensory ganglia. [A ganglion is a collection of neuron cell bodies in the PNS. (The PNS is the Peripheral Nervous System)] Somatic sensory neurons monitor external conditions and our position in it. Visceral sensory neurons monitor internal conditions and the status of other organs in it.

Motor Neurons There are 3 categories: 1. Somatic motoneurons- involved in contraction of muscles. 2. Special visceral motoneurons- involved in the motion of neck and facial muscles. 3. Visceral motoneurons- involved in contraction of heart, muscles of arteries, and viscera not consciously controlled.

Links

References McGraw Hill. (2010, February 2). Nerve Cells. In Neurons [Nervous System]. Retrieved February 4, 2010, from McGraw Hill website: http://www.getbodysmart.com/‌index.htm Prentice Hall Inc., & Pearson Co. (1999-2000). Neuron Classification. In Neural Tissue [Neurons]. Retrieved February 3, 2010, from Prentice Hall Inc. website: http://cwx.prenhall.com National Institute of Aging, US National Institute of Health, & ADEAR. (2008, November 25). Neurons. Retrieved February 4, 2010, from US National Institute of Health website: http://www.nia.nih.gov/‌Alzheimers/‌Publications/‌Unraveling/‌Part2/‌hallmarks.htm PSYweb.com. (n.d.). Psyweb [Bipolar Neurons]. Retrieved February 4, 2010, from PSYweb website: http://psyweb.com/‌Physiological/‌Neurons/‌bineuron.jsp