Biology: Nervous System
Nervous System
● It is important in helping to maintain the homeostasis(balance) of the human
body
● It is a series of sensory receptors work with the nervous system to provide
information about changes in both the internal and external environments
● The human nervous system is a complex of interconnected systems in which
larger systems are comprised of smaller subsystems each of which have specific
structures with specific functions.
Structure and Function
● Neurons – They are also called nerve cells. These are the basic elements of the
nervous system.
○ Cell Body: The main processing center of the cell.
○ Dendrites: Thin branching extensions of the cell body that conduct nerve
impulses toward the cell body
○ Axon: A single branch which conducts nerve impulses away from the cell
body. Myelin sheath and neurilemmal are coverings.
Impulse Transmission
● Terminal end fibers are located at the ends of the axon and they transmit
impulses leaving the neuron across a synapse to the next neuron.
Three Types of Neurons
● Efferent(Motor) – Conveys information from the CNS to muscles and glands.
● Afferent (Sensory) – Carry information from the sensory receptors to the CNS.
● Interneuron – Carry and process sensory information.
Neuroglia – Support, protect, connect, and remove debris from the nervous system.
Types of Neuroglial Cells
● Astrocytes
● Oligodendroglia
, ● Microglia
Two Major Components
● Central Nervous System (CNS)
○ Made up of the brain and the spinal cord
● Peripheral Nervous System (PNS)
○ Made up of all the nerves that lead into and out of the CNS.
Central Nervous System
● The central nervous system is composed of two major interconnected organs:
The brain and the spinal cord
● These organs work together to integrate and coordinate sensory and motor
information for the purpose of controlling the various tissues, organs, and organ
systems of the body.
● It is responsible for higher neural functions such as memory, learning, and
emotion.
Brain: it weighs 3 pounds in adults. It is 75% water and 20% oxygen. It contains over 100
billion neurons. It controls bodily functions and interactions with the outside world
Brain Stem****: Made up of the midbrain; Pons and the medulla oblongata.
● Midbrain****: Involved with the visual reflexes.
● Pons: Located between the midbrain and the medulla oblongata. It controls
certain respiratory functions.
● Medulla Oblongata****: Contains centers that regulate heart and lung
functioning, swallowing, coughing, vomiting, and sneezing.
Cerebellum
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