Lecture 2: Nervous System 1 cont, 2, and 3 Flashcards
Two major efferent systems:
Somatic Nervous System
Autonomic Nervous System
The SNS innervates _____ _____, which is under ______ control.
skeletal muscle
voluntary
Cell bodies of the SNS lie in
the CNS
SNS axons extend
into the periphery to innervate one or more neuromuscular junctions
The ANS is under ______ control and innervates
involuntary
all peripheral effectors that is not skeletal muscle
Axons of ANS motor neurons inside the CNS synapse where?
On neurons in the peripheral autonomic (motor) ganglia
Ganglionic neurons of the ANS control
peripheral effectors
Preganglionic fibers
Part of the ANS
Axons that extend from the CNS to a ganglion
Postganglionic fibers
Part of ANS
Axons connecting ganglionic cells with the peripheral effectors
The basic structural unit of the nervous system is the
Neuron
Three parts of a neuron
- Cell body
- Dendrites
- Axon
Cell bodies
- Contains the nucleus and other organelles
- Serves as the nutritional center of the neuron
Dendrites
Cytoplasmic extensions that receive stimuli and conduct impulses to the cell body
Axon (nerve fiber)
Conducts impulses away from the cell body
Axon arises from
a thickened region of the cell body called the axon hillock
Action potentials first appear
at the initial segment of the axon
Collaterals
Branches along the length of the axon
Collaterals enable a single neuron to
communicate with several other cells
The main axon trunk and collaterals end in
fine extensions called telodendria
Synaptic knobs (terminal button)
Located at the tips of the telodendria, they form synaptic connections with other cells
Communication between cells at synapse most often involves the release of ______ by the ______ _____
neurotransmitters
Synaptic knob
Motor end plate
specialized portion of the muscle cell membrane immediately under the synaptic knob
Four functional segments of the neuron
- Receptive segment
- Initial segment
- Conduction segment
- Transmissive (Effector) segment
Receptive segment of neuron
- Receives and processes synaptic inputs from numerous other neurons.
- Resolutions of these processes will be passed on to the next segment only if it is sufficiently stimulated