Download Intro Nervous System and Neurons

3 Functions of the Nervous System
(SIM)
1. Sensory input—gathering information
– monitor changes inside and outside the body
– changes = stimuli
– sensory receptors responsible for input
2. Integration
– decide if and what action is needed
3. Motor Output
– a response
– activates muscles or glands (effectors)
Functions of the Nervous System
Figure 7.1
Organization of the Nervous System
Structural Classification
of the Nervous System
2 Main Divisions
1. Central nervous system
(CNS)
– Brain
– Spinal cord
2. Peripheral nervous system
(PNS)
•
•
Spinal nerves (to and from
spinal cord)
Cranial nerves (to and
from brain)
Functional Classification of
the Peripheral Nervous System
• Sensory (afferent) division
– carry information to the central nervous system
– Keep the body informed of internal and external
environment
• Motor (efferent) division
– carry impulses away from the central nervous
system
– Cause some sort of effect
Functional Classification of
the Peripheral Nervous System
– Two subdivisions of the Motor (efferent)
division
1. Somatic nervous system = voluntary
Skeletal muscles (except reflexes)
2. Autonomic nervous system = involuntary
smooth muscle, cardiac muscle, glands
Functional Classification of
the Peripheral Nervous System
Two subdivisions of the Autonomic nervous system
1. Sympathetic
 Concerned with processes involving expending energy.
 Active during times of extreme stress, emotion, and
exercise.
2. Parasympathetic
 Concerned with conservation of energy
 Can dominate sympathetic system.
Books says antagonistic, but they are more complimentary
Nervous Tissue:
2 Main Types of Cells
1. Neurons
carry messages (impulses)
2. Supporting cells or neuroglia
Nervous Tissue: Neurons
specialized to transmit messages
– structures may differ, but all neurons have:
PARTS:
1. Cell body
–contains transparent nucleus
–large conspicuous nucleolus
–metabolic center of the cell
Nervous Tissue: Neurons
2 Types of Processes
• fibers that extend from the cell body
– Dendrites—conduct impulses toward the cell body
– Axons—conduct impulses away from the cell body
Nervous Tissue: Neurons
Figure 7.4
Axon Terminals- axon ends
• contain vesicles with neurotransmitters
• do not touch dendrite of next neuron OR
muscle
– Synaptic cleft—gap between adjacent neurons
– Synapse—junction between nerves
Nervous Tissue: Neurons
• Myelin sheath—whitish, fatty
material covering axons
• Schwann cells—produce
myelin sheaths in jelly roll–like
fashion
• Nodes of Ranvier—gaps in
myelin sheath along the axon
Neurons
Figure 7.4
Functional Classification of Neurons
• Sensory (afferent) neurons
– Carry impulses from the sensory receptors to the
CNS
• Cutaneous sense organs
– Heat, cold, pressure, pain
• Proprioceptors—detect stretch or tension (found in
muscles, tendons and joints)
• Motor (efferent) neurons
– Carry impulses from the central nervous system to
viscera, muscles, or glands
Functional Classification of Neurons
• Interneurons (association neurons)
– Found in neural pathways in the central nervous
system
– Connect sensory and motor neurons
• Receptors
– Specialized dendritic endings
• Simple: cutaneous receptors (pain, touch)
• Complex: special sense organs (eye, nose)
Figure 7.6
6 Types of Support Cells
1. Astrocytes (CNS)
– star-shaped cells
– Most abundant of the glial cells
Mainly function between neurons and capillaries
• Bridging the two
• Communication between the two
• Barrier between the two
– Control the chemical environment of
the brain (taking in extra K+ or neurotransmitters)
Nervous Tissue: Support Cells
2. Microglia (CNS)
–Spiderlike phagocytes (phago- eat)
–Dispose of debris
(dead brain cells and bacteria)
Nervous Tissue: Support Cells
3. Ependymal cells (CNS)
–Line cavities of the brain and spinal cord
–Ciliated cuboidal epithelial cells
–Circulate cerebrospinal fluid
–Help in production of cerebrospinal fluid
Nervous Tissue: Support Cells
4. Oligodendrocytes (CNS)
– Wrap around nerve fibers in the central nervous system
– Produce myelin sheaths in CNS
5. Schwann cells (PNS)
– Form myelin sheath in the PNS
Nervous Tissue: Support Cells
6. Satellite cells (PNS)
–Protect neuron cell bodies by providing cushion
Regions of a Typical Neuron
Vocabulary
Tract- bundles of nerve fibers running through the CNS.
Nerves-bundles of nerve fibers running through the
PNS
White matter- Consists of dense collections of
myelinated fibers
Gray matter- Consists of mostly unmyelinated fibers
and cell bodies