How Nerve Signals Maintain Homeostasis

 

 

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The Importance of the Nervous System

 

-         Neuron: nerve cell that conducts nerve impulses

-         Sensory neuron (afferent neuron): carries impulses to the central nervous system

-         Interneuron: carries impulses within the central nervous system

-         Motor neuron (efferent neuron): carries impulses from the central nervous system to effectors

-         Dendrite: projection of cytoplasm that carries impulses toward the cell body

-         Axon: extension of cytoplasm that carries nerve impulses away from the cell body

-         Myelin sheath: insulated covering over the axon of a nerve cell; composed of Schwann cells

-         Nodes of Ranvier: regularly occurring gaps between sections of myelin sheath along the axon where nerve cells are transmitted

-         Neurilemma: delicate membrane that surrounds the axon of some nerve cells

-         Reflex arc: neural circuit that travels through the spinal cord; provides a framework for a reflex action

 

Electrochemical Impulse

 

-         Nerves conduct electrochemical impulses from the dendrites along the axon to the end plates of the neuron.

-         Active transport and diffusion of sodium and potassium ions establish a polarized membrane.

-         An action potential is caused by the inflow of sodium ions.

-         Nerve cells exhibit an all-or-none response.

-         Neurotransmitters allow the nerve message to move across synapses.

 

The Central Nervous System

 

-         Meninges: protective membranes that surround the brain and spinal cord

-         Cerebrospinal fluid: circulates between the innermost and middles membranes of the brain and spinal cord; acts as a transport medium and shock absorber

-         Olfactory lobes: areas of the brain that detect smell

-         Cerebrum: the largest and most highly developed part of the human brain; stores sensory information and initiates voluntary motor activities

-         Cerebral cortex: the outer lining of the cerebral hemispheres

-         Corpus callosum: a nerve tract that joins the two cerebral hemispheres

-         Cerebellum: the region of the brain that acts as a relay station by sending nerve messages between the cerebellum and the medulla

-         Medulla oblongata: the region of the hindbrain that joins the spinal cord to the cerebellum; the site of autonomic nerve control

 

Homeostasis and the Autonomic Nervous System

 

-         The autonomic nervous system is a motor system.

-         The sympathetic nervous system prepares the body for stress; the parasympathetic system returns the body to a resting states.

-         The neurotransmitters released from the sympathetic system are acetylcholine and norepinephrine; the parasympathetic system releases only acetylcholine.

-         Endorphins and enkephalins are natural painkillers produced by the body.

 

 

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