Ch. 8
Nervous System
8-1 Anatomical divisions
Two major groups
Central nervous system= brain & spinal cord
Peripheral nervous system= nerves that extend from the brain and spinal cord
Functions
Sensory Input Function
Sensory receptors- detect changes
Integrative Function
Integration occurs in inter neurons
Motor Function
Effectors- muscles and glands
8-2 Distinguish between neurons and neuroglia
Neuron- the structural & functional unit of the nervous system
Neuron structure
Cell body= central portion of neuron
Neuron processes/ nerve fibers
Dendrites
Axons
Axons in PNS
Myelin sheaths and schwann cells
Axons in CNS
oligodendrocyte
White matter
PNS= nerve
CNS= Tract/down
Grey matter
PNS= ganglia
CNS= nucleus
Neuroglial Cells
PNS= Schwann cells
Satellite cells
CNS
Oligodendrocytes
Astrocyte
Microglia
Ependymal cells
Classification of Neurons
Sensory Neurons
Afferent neurons
Somatic receptors
Visceral receptors
Interneurons (Association)
Motor Neurons
Efferent neurons
Multipolar Neurons= most common type
Bipolar Neurons= rare, smell and hearing
Unipolar Neurons (most PNS sensory neurons)
8-3 Describe events in the generation and propagation of an action potential.
Resting Nerve Cells
Cell membrane is polarized
Potential Difference = the difference in electrical charge between 2 points
Distribution of ions across the cell membrane
K; high inside
Na+; high outside
Cl; high outside
Negatively charged proteins or Anions; high inside
Normal = -70mv
Membrane Potentials
more negative= "hyperpolarization"
less negative = depolarization
Action potentials
-55mv threshold potential is reached
Nerve impulse= the propagation of action potentials
Synapse= the junction between two neurons where a nerve impulse is transmitted
Most typical NT is Acetylcholine
8-4 Synaptic transmission
Refractory period= the period following a NI when a threshold stimulus cannot produce another NI
All or nothing response= if nerve cells respond at all it responds completely
Summation= many subthreshold stimuli received one after another may allow threshold potential to be reached
Conduction = the manner in which the NI runs down the neuron/ nerve
8-5 3 meningal layers
Meninges
Dura mater = outermost
Arachnoid = middle layer
Pia mater = innermost layer
Spinal cord
epidural space
Ventricles and cerebrospinal fluid
Chroid plexis secretes
8-6 Roles of gray matter and white matter
Gross structure
contains 31 segments
Cauda equina nerves travel downward
Gray matter
bundles of cell bodies
white matter
myelanted axons
Important features
Ventral root
Dorsal root