Structures and Functions of the Nervous System

Functional unit of the nervous system 9.1 Introduction Functional unit of the nervous system neuron Specialized to respond to react to physical and chemical changes in their surroundings Neurons carry information in the form of electrochemical changes called impulses to other neurons and other cells

Structures of a neuron- 1) Cell Body- contains the nucleus and organelles 2) Dendrites- receive info from other neurons 3) Axons- send impulses away from the cell body

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Neuroglia: carry out a variety of functions to aid and protect components of the nervous system Includes: 1. physical support 2. insulation 3. nutrients During development before birth, neuroglia release and relay signals that guide differentiation of neurons from progenitor cells

4 types of neuroglia found in the central nervous system…to be discussed later

Synapse: space between neurons Neurotransmitters: chemical messenger

Nervous System Anatomy Physiology Organs are divided into two groups: Central Nervous System (CNS) a. Brain b. Spinal Cord Peripheral Nervous System (PNS) a. Nerves A B C

2 Subsystems of the Nervous System 9.2 General functions of Nervous System 2 Subsystems of the Nervous System Function: Function: Process info Carries messages to and from CNS

Nervous System Anatomy Physiology Together, these systems provide 3 main functions Sensory monitor internal and external environment (peripheral nerves) Integration information from the sensory nerves is integrated into the CNS by neurons Motor Output stimulation of EFFECTORS (muscles or glands) to move or secrete substances

Overview of a vertebrate nervous system

Division of Peripheral Nervous System

9. 3 Neuroglial cells- 1. Specialize to support the neuron 2 9.3 Neuroglial cells- 1. Specialize to support the neuron 2. MORE NEUROGLIA THAN NEURONS 3. VARIOUS FUNCTIONS: a. fill in the spaces between neurons b. provide structure c. produce components to insulate d. phagocytic 4. Non-excitable-do not send impulses 5. Four types in the CNS

1) Astrocytes– form connections between blood vessels and neurons -PROVIDE STRUCTURAL SUPPORT -REGULATE CONCENTRATIONS OF NUTRIENTS -FORM SCAR TISSUE WITH INJURY TO CNS A tissue sample from the brain. The area where the astrocyte connects to the blood vessel is called a foot process.

2) Oligodendrocytes-insulate neurons, form the myelin sheath Electron micrograph showing branched oligodendrocytes with processes extending to several underlying axons

3. Microglial cells- engulf microbes and remove cellular debris, form scars in damaged areas Activated microglial cells in a rat brain. When activated, these cells are phagocytic helping to removing damaged or dying cells.

4. Ependymal cells- help circulate cerebrospinal fluid- in ventricles and central canal of spinal cord Ependymal cells found in the 3rd ventricle of the brain of a 32 week old fetus.

2 types in the PNS 1) Satellite cells- surround and control the chemical environment of the neuron 2) Schwann- insulate the neuron, form the myelin sheath What is the name of the similar cell in the CNS?

Fun Fact: For every nerve cell in your body there are 50 glial cells. If a person looses brain cells every day, how does a child's brain increase in mass from 400 g to 1400g in adulthood? 1. The number of glia cells increases tremendously. More synapses are formed. *When glia cells reproduce uncontrollably, a person has cancer.