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Transcript
Introduction to Nerves and the
Nervous System
Chapter 19
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Role of the Nervous System
• Controlling the functions of the human body
• Analyzing incoming stimuli
• Integrating internal and external responses
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Make Up of the Nervous System
• Central Nervous System (CNS)
– Composed of the brain and spinal cord
• Peripheral Nervous System (PNS)
– Sensory receptors bring information into the CNS
– Motor nerves carry information away from the CNS
• Autonomic Nervous System (ANS)
– Uses components of the CNS and PNS to regulate
automatic or unconscious responses to stimuli
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Function of the Cells that Make Up the Nervous
System
• Allow movement
• Allow realization of various sensations
• Provide response to internal and external stimuli
• Stimulate learning, thinking, and emotions
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Neuron
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Types of Axons
• Afferent Fibers
– Nerve axons that run from peripheral receptors into
the CNS
• Efferent Fibers
– Nerve axons that carry nerve impulses from the CNS
to the periphery to stimulate muscles or glands
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Action Potential
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Electrolytes Involved in Nerve Cell Action
• Sodium
• Potassium
• Calcium
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Movement of Electrolytes with Action
• Rest/Repolarization
– Membrane is impermeable to sodium
– Permeable to potassium
• Action/Depolarization
– Sodium goes into the cell
– Potassium leaves the cell
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Formation of Myelin Sheath
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nerve Synapse
• Presynaptic Nerve
• Synaptic Cleft
• Postsynaptic Effector Cell
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
What nerve axons carry nerve impulses from the central
nervous system to the peripheral nervous system?
a. Somatic axons
b. Efferent fibers
c. Afferent fibers
d. Sensory axons
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
b. Efferent fibers
Rationale: Efferent fibers: Nerve axons that carry nerve
impulses from the CNS to the periphery to stimulate
muscles or glands
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Neurotransmitters
• Acetylcholine
– Communicates between nerves and muscles
• Norepinephrine and Epinephrine
– Catecholamines released by nerves in the
sympathetic branch of the ANS
• Dopamine
– Involved in the coordination of impulses and
responses
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Neurotransmitters (cont.)
• Gamma-aminobutyric Acid (GABA)
– Inhibits nerve activity and is important in preventing
over-excitability or stimulation such as seizure
activity
• Serotonin
– Important in arousal and sleep and in preventing
depression and promoting motivation
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Central Nervous System
• Made up of brain and spinal cord
• Structures are covered by meninges
• Blood brain barrier
• Blood supply to the brain
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anatomy of the Brain
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Hindbrain
• Runs from the top of the spinal cord into the midbrain
• Most primitive part of the brain - contains the brainstem
• Controls basic vital functions:
– Breathing
– Blood pressure
– Swallowing
– RAS
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Midbrain
• Contains the thalamus, the hypothalamus, and the limbic
system
• The thalamus sends direct information into the cerebrum to
transfer sensations
• Hypothalamus acts as major sensor activity in the body
– Temperature regulation
– Water balance
– Appetite
– Endocrine function
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Limbic System
• Contain high levels of the neurotransmitters
– Epinephrine
– Norepinephrine
– Serotonin
• Controls expression of emotions
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Forebrain
• Made up of two cerebral hemispheres joined together by
the corpus callosum
• Receives and sends nerve impulses, coordinates speech
and communication, and facilitates learning
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Spinal Cord
• Made up of 31 pairs of spinal nerves
• Each spinal nerve has two components or roots
– Sensory fiber (dorsal root)
• Brings information into the CNS from the periphery
– Motor fiber (ventral root)
• Causes movement or reaction
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Function of Central Nervous System
• Sensory Functions
• Motor Functions
• Intellectual and Emotional Functions
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Intellectual and Emotional Function
• Two hemispheres of the brain process information
differently
• Right Side
– Artistic
• Left Side
– Analytical
• When learning takes place and actual change occurs in a
neuron
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Intellectual and Emotional Function (cont.)
• Some degree of stress helps facilitate learning
• Increased stress inhibits learning
• The limbic system plays a role in learning
• Emotions associated with memory as well as the present
have an impact on stimulus response.
• The placebo effect is a documented effect of the mind on
drug therapy: If a person perceives that a drug will be
effective, it is much more likely to actually be effective.
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
What is a documented phenomenon of the mind affecting
drug therapy?
a. Action potential
b. Placebo effect
c. Expectation effect
d. Learning
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
b. Placebo effect
Rationale: The placebo effect is a documented effect of the
mind on drug therapy: If a person perceives that a drug
will be effective, it is much more likely to actually be
effective.
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins