Chapter 12: The Nervous System Flashcards
Afferent or Sensory Signals
are perceived by sensory receptors in PNS
Somatic Sensory
General-skin and body walls, touch, pain, pressure, vibration, temperature and proprioception
Special-hearing, equilibrium, vision, smell
Visceral Sensory
General-stretch, pain, temperature, chemical changes, nausea and hunger
Special-taste
Efferent or Motor Signals
are carried away from CNS by PNS nerve fibers to muscles and glands
Somatic Motor or Voluntary Motor
General: motor innervation of all skeletal muscles
Visceral Motor or Involuntary Motor
General: motor innervation of smooth and cardiac muscle and glands
Autonomic Nervous System (aka. Automatic Nervous System because it automatically happens)
Nervous Tissue
Neurons or nerve Cells
- basic structural unit of nervous system
- conduct electrical signals
- extreme longevity and non-mitogenic
- high metabolic rate needs high glucose and oxygen
Supporting Cells
- 4 types in CNS: neuroglia cells
- 2 types in PNS- glial cells
Cell Body
nucleus surrounded by cytoplasm
- most neurons are located within CNS
- clusters found in PNS-ganglia or ganglion
Neuron Processes
extensions of cell body
- Dendrites: function as receptive sites conducting electrical signals toward cell body (receives)
- Axons: transmits nerve impulses away from cell body (carries away)
Synapses
cell junction mediates transfer of information
- presynaptic to postsynaptic neuron
- most common: Axon-dendritic synapses
Neuronal Zones
Signal Reception Zone
Signal Integration Zone
Signal Conduction Zone
Signal Transmission Zone
Signal Reception Zone
Dendrites and Cell Body
Receives incoming signals
Signal Integration Zone
If there is a large enough stimulus, the stimulus is converted to an electrical signal (change in membrane potential) that is sent down the axon
Signal Conduction Zone
Axon
neurons wrapped in a myelin sheath transmit the electrical signal
Signal Transmission Zone
Tegration Zone. Axon Hillock
where the cell body meets the collaterals. Swelling at axon terminus where comes in close contact with the target cell; does not touch
-Electrical signal is converted to a chemical signal (neurotransmitter)
Supporting Cells in CNS
Astrocytes
Microglia
Ependymal Cells
Oligodendrocytes
Astrocytes
most abundant; controls ionic environment around neurons
Microglia
smallest and least abundant; macrophages of CNS engulfing microbes, injured or dead neurons
Ependymal Cells
form epithelium lining central cavity of spinal cord and brain; circulate cerebrospinal fluid with cilia
Oligiodendrocytes
produces myelin sheaths that insulate neurons
Myelin
lipoprotein that surrounds thicker axons
Structure of Myelin Sheaths
Layers consist of concentric layers of plasma membrane of supporting cell
Function of Myelin Sheaths
insulation layers that prevents leakage of electrical current from axon to increase speed of impulse conduction along axon; energy efficient
Nodes of Ranvier
gaps in myelin sheath
Nerve impulses do not travel along myelin covered regions but jump from node to nodes
