Transcript 9.1-9.4 Notes

9.1-9.4 Notes
Nervous System Functions
• Coordinate body functions
• Maintain homeostasis
• Respond to changing conditions internally
and externally
• Made of 2 parts
– Neurons
– Neuroglial cells
Neurons (nerve cells)
• Transmit information in the form of a nerve
impulse
• Different parts of a neuron
– Cell body-round area/has nucleolus
– Dendrites-branches that receive the signal
– Axon-sends the single to the next neuron
• Nerves-bundles of axons
Neuroglial Cells
• Provide physical support, insulation, and
nutrients for the neurons
• Protection devices
Organs of nervous system are in
2 groups.
• Central Nervous
System (CNS)
– Made of brain and
spinal cord
• Peripheral Nervous
System (PNS)
– Made of neurons that
connect to CNS
Have 3 general functions:
Sensory
Motor
Integrative
3 general functions
• Sensory-sensory receptors are at the end of
peripheral neurons
– Gather information about changes in and out of
the body
• Example: temperature, light, sound, oxygen levels
• Integrative-bring all the information
together to create perceptions from
sensations
3 general functions (cont.)
• Motor
– Effectors-responsive structures that receive
impulses
• Are found outside the nervous system
• Example: muscle, glands
– 2 categories
• Somatic-conscious control (skeletal muscles)
• Autonomic-unconscious control (heart and smooth
muscle)
Neuroglial cells
• Produce myelin (fat
that surrounds the
axon)
• Fills space
• Framework
• There are different
types of neuroglial
cells.
Types of neuroglial in CNS
• Microglial-support neurons
– Phagocytosis of bacteria and cell debris
• Oligodendrocytes-found along nerve fibers
– Provide myelin for myelin sheath (around axon within
brain and spinal cord)
• Astrocytes-between neurons and blood vessels
– Support, join parts, help regulate ion and nutrient
levels, form scar tissue when injury occurs to the CNS
• Ependymal cells-cover special brain parts and
close spaces between the brain and CNS
Neuroglial in the PNS
• Schwann cells-create myelin for neurons in
the PNS
• Too many neuroglial cells-cause brain
tumors (fast growing gliomas)
Neuron Structure
• Cell body
– Cytoplasm, organelles, cell membrane
– Neurofibrils-fine threads
– Chromatophilic substance (Nissl bodies)-like
rough ER
– Nucleolus
• Dendrites
– Short, highly branched, receptors
Neuron structure (cont)
• Axons
– Axon hillock-elevated portion leading into the axon
from the cell body
– May have side branches
– PNS axons-made of Schwann cells that make myelin
– Neurilemma-covering that surrounds myelin sheath
– Nodes of Ranvier-gaps in between myelin sheath of
axon
• Myelinated in CNS are called white matter
• Unmyelinated in CNS are called gray matter
– Axons can regenerate in PNS because of neurilemma
– CNS are myelinated by oligodendrocytes-no
neurilemma so can’t regenerate
Label the picture on your notes.
Groupings-Structural
trigger point-sensitive region of axon;where nerve
impulse begins to be sent down axon
• Multipolar-one axon and
many dendrites (brain and
sc)
• Bipolar-1 axon, 1 dendrite
(eyes, nose, ears)
Structural Differences (cont)
• Unipolar neuron-one
axon, no dendrites
– Dendrite near
peripheral body
– Other part connected to
brain or spinal cord
– Cell bodies of these are
bunched to form
ganglia
• Outside the brain or
spinal cord
Functional Groupings
• Sensory (afferent)-carry impulse from peripheral
into CNS
– Specialized receptor ends on dendrite tips
– Dendrites are closely associated with receptor cells in
skin or in sensory organs
– Unipolar, some bipolar
• Interneurons-in brain and spinal cord
– Transmit impulses from 1 to another by forming links
with other neurons
– multipolar
Functional groupings (cont)
• Motor neurons-efferent
– Multipolar
– Carry impulse out of CNS to the effectors
– Stimulate muscle and glands to respond