Chp 11: Fundamentals of Nervous System and Nervous Tissue Flashcards
Basic fxns of the nervous system
Complex network for communication btwn external environment and body homeostasis mechanisms & btwn internal environments and homeostasis mechanisms
5 basic components of nervous system fxns
- sensor
- sensory neuron pathway (sensory input)
- integration center
- motor neuron pathway (motor output)
- effector
Structural divisions of nervous system
CNS: brain and spinal cord
PNS: mostly cranial and spinal nerves
Functional divisions of nervous system
Sensory/Afferent division of PNS: conveys impulses to CNS
Motor/efferent division of PNS: conveys impulses from CNS; efferent division includes somatic (voluntary) and autonomic (involuntary) systems
Neuron
functional cell of the nervous system cell body/soma 5-140 µm specialized, slender processes: dendrites: input region axon: conducting component secretor/output region: axon terminal
Structural classes of neurons: multipolar
many dendrites, one axon most common class of neuron
Structural classes of neurons: bipolar
one dendrite, one axon
in special sensory organs
Structural classes of neurons: unipolar
one short, single process
dendrite, axon continuous
afferent neurons
Functional classes of neurons: sensory/afferent
conduct action potential from PNS toward CNS
Functional classes of neurons: motor/efferent
conduct action potential away from CNS to PNS
Neuroglia: Satellite cells
PNS
Surround neuron cell bodies in ganglia
Regulate 02, CO2, nutrient,and neurotransmitter levels around neurons in ganglia
Neuroglia: Schwann cells
PNS
Surround axons in PNS
Are responsible for myelination of peripheral axons
Participate in repair process after injury
Neuroglia: Oligodendrocytes
CNS
Myelinate CNS axons
Provide structural framework
Neuroglia:astrocytes
CNS Maintain blood-brain barrier Provide structural support Regulate ion, nutrient, and dissolved gas concentrations Absorb and recycle neurotransmitters Form scar tissue after injury
Neuroglia: microglia
CNS
remove cell debris, wastes, and pathogens by phagocytosis
Neuroglia: ependymal cells
CNS
line ventricles (brain) and central canal (spinal cord)
Assist in producing, circulating and monitoring of cerebrospinal fluid
Myelin sheath: PNS
Formed by Schwann cells
Neurilemma: outermost layer of Schwann cell, bulge of Schwann cell’s nucleus and most of the cytoplasm
Nodes of Ranvier: myelin sheath gaps (adjacent Schwann cells do not touch each other)
Myelin sheath: CNS
Formed by oligodendrocytes that have multiple flat processes and can coil around 60 axons at same time
Lacks neurilemma
Myelination
Whitish, fatty sheath along length of axon
Electrically insulates axon
Increases speed of nerve impulse transmission
Helps neural regeneration in PNS
Amount of myelination increases from birth to maturity
Destruction of myelin sheath (demyelination)
multiple sclerosis
Tracts
Bundles of neuron processes in CNS
Nerves
Bundles of neuron processes in PNS
Nuclei/Nucleus
Clusters of cell bodies in CNS
Ganglia/Ganglion
Clusters of cell bodies in PNS
Resting membrane potential
Potential difference in resting neuron cytoplasmic charge (inside) of the membrane is negatively charged (-70 mV)
Graded potentials
short-lived, localized changes in membrane potential that cause current flows
Either hyperopolarizations or depolarizations
Magnitude varies directly with stimulus strength
Triggered by stimulus in neuron’s environment that opens gated ion channels
Action potential
Brief reversal of membrane potential with total amplitude of about 100 mV (-70 to +30 mV)
Only generated by cells with excitable membranes (neurons and muscle cells)
Synapse
site of communication between 2 neurons or a neuron and an effector
Presynaptic neuron
nerve conducting impulses toward the synapse (sends info)
Postsynaptic neuron
Neuron transmitting electrical signal away from synapse (receives info)
Outside CNS, postsynaptic cell may be neuron or effector cell (muscle cell or gland cell)
Neurotransmitters
Signaling chemicals usually stored in vesicles that are released into extracellular space (synapse)
Can either excite or inhibit neurons (or effector cells)
Direction of nerve signal travel
Can only go in one direction
Dendrite –> cell body –> axon –> axon bulbs –> next neuron/effector
