Chapter 11 Flashcards
Functions of Nervous System
- sensory input
- integration
- motor output
Motor Output
activation of effector organs (muscles and glands) produces a response
Sensory (afferent) division
somatic and visceral sensory fibers
Somatic sensory fibers
convey impulses from skin, skeletal muscles, and joints to CNS
Visceral sensory fibers
convey impulses from visceral organs to CNS
PNS
sensory and motor
Motor (efferent)
transmits impulses from CNS to effector organs
-muscles and glands
Neuroglia (glial cells)
small cells that surround and wrap delicate neurons
Neurons (nerve cells)
excitable cells that transmit electrical signals
Astrocytes
most abundant, versatile, and highly branched of glial cell
Astrocytes function
support and brace neurons
Microglial cells
can transform to phagocytize microorganisms and neuronal debris
Ependymal cells
line the CSF-filled ventricles in the brain and the central canal of the spinal cord
Oligodendrocytes
processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
Schwann cells
similar function as oligodendrocytes but in PNS
Where are most neuron cell bodies located?
CNS
nuclei
cluster of neuron cell bodies in CNS
ganglia
clusters of neuron cell bodies in PNS
Myelination in the PNS
formed by Schwann cells
Schwann cells
wraps around axon in jelly roll fashion and one cell forms one segment of myelin sheath
Myelin sheaths in the CNS
formed by processes of oligodendrocytes
Functional classification of neurons
sensory, motor, interneurons
Na+ channel inactivation gates close
membrane permeability to Na+ declines to resting state and AP spike stops rising
Repolarization
membrane returns to resting membrane potential
Hyperpolarization
some K+ channels remain open, and Na+ channels reset
Saltatory conduction
occurs only in myelinated axons and is about 30 times faster
Myelinated axons
- myelin sheaths insulate and prevent leakage of charge
- voltage-gated Na+ channels are located at myelin sheath gaps
- APs generated only at gaps
- electrical signal appears to jump rapidly from gap to gap
