Lecture 7c Flashcards
Nervous tissue composition:
Neurons true conducting cells
Neuroglial (supporting) cells
Examples of neuroglial cells:
Astrocytes Oligodendrocytes Microglia Ependymal Schwann cells Satellite cells
Properties of Neurons:
Excitability
Conductivity
Secretion
Functional classification of neurons:
Based on the direction of conduction
Sensory
Motor
Interneuron
Specialized to detect stimuli and transmit information to CNS
Sensory (afferent) neuron
Receive signals from many different neurons and perform an integrative function “decision making” to respond to the different stimuli
Interneuron (association neurons)
Transmit the appropriate response from the interneuron to an end organ to carry out body’s response to the stimuli
Motor (efferent) neurons
Parts of a Neuron
Nucleus (with nucleolus) Neuroglial cells Cell body Axon Dendrites
Conducts impulses towards the cell body
Numerous, short, branched, and unmyelinated
Contain neurofibrils
Dendrites
Conduct impulses away from the cell body
Single, long, thin cylindrical, and may be myelinated
Axons
Axons ariaes at
Axon hillock
Impulses arise from
Initial segment (trigger zone)
Axons end in fine processes called
Axon terminals
Swollen tips of axons
Synaptic end bulbs
Synaptic end bulbs contain
Vesicles with neurotransmitters
Location for most protein synthesis
Cell body
Moves substances
Axonal transport system
Two types of axonal transport system
Slow axonal
Fast axonal
Move in one direction only - away from the cell body = anterograde
Movement at 1-5 mm per day
Slow axonal
Moves organelles and materials along surface of microtubules
Movement at 200-400mm per day
Transport in either direction
For use or recycling in cell body
Fast axonal
Structural classification of neurons:
Multipolar
Bipolar
Unipolar
Most (99%) neurons in the body are
Multipolar
Rare and occur in special sense organs of ear, nose, and eye
Bipolar neurons
Begin as bipolar but processes fuse into one
They are primarily sensor neurons
Unipolar neurons
Found in CNS and PNS
Perform a supporting function for neurons
Neuroglia cells
Neuroglia cells in the CNS:
Oligodendroglialcytes
Astrocytes
Ependymal cells
Microglia
Neuroglia cells in PNS:
Schwann cells
Satellite cells
Half of the volume of the CNS
Smaller cells than neutrons
50% more numerous
Neuroglial cells
Surround neuron cell bodies within ganglia
Satellite cells - PNS
Cells encircling PNS axons
Each cell produces part of the myelin sheath surrounding an axon (only 1) in the PNS
Schwann cell - PNS
Separate each Schwann cell
Node of Ranvier
Schwann cells myelinate axons in the PNS during fetal development
Myelination in PNS
Form epithelial membrane lining cerebral cavities and central canal
Ependymal cells in CNS
Ependymal cells produce
Cerebrospinal Fluid (CSF)
Small cells found near blood vessels
Phagocytic role
Derived from cells that also gave rise to macrophages and monocytes
Microglia in CNS
Star-shaped cells
Most common glial cells
Their processes extend into the basement membrane of capillaries and pia mater
Astrocytes in CNS
Functions of the Astrocytes in CNS:
Form blood-brain barrier
Metabolize neurotransmitters
Regulate K+ balance
Procude nutrients and structural support
Form myelin sheath in CNS
Fewer branches than astrocytes
Oligodendrogliocytes - CNS
Insulating layer around a nerve
Formed by oligodendrocytes in CNS and Schwann cells in PNS
Myelin
Myelin is compose of:
Lipoprotein
Phospholipids
Glycolipids
Cholesterol
Process of myelin formation
Myelination
