Lecture 2: CNS Organization Flashcards by Kaley Canova-Gaitros

What are the 3 main division of the nervous system?

CNS, PNS, ANS

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What are the subdivisions of the CNS?

Brain, Spinal cord

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What are the subdivisions of the PNS?

Cranial nerves, Spinal nerves

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What are the subdivisions of the ANS?

Sympathetic, Parasympathetic

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Nucleus

Aggregation of dendrites/cell bodies in CNS

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Ganglion

Aggregation of dendrites/cell bodies in PNS

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Nerve

Bundle of fibers/axons in PNS

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Tract

Bundle of fibers/axons in CNS

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Which part of the neuron has receptors for neurotransmitters and conducts local potentials?

A. Cell body
B. Axons
C. Dendrites
D. Schwann cell

C. Dendrites

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Which part of the neuron releases neurotransmitters and conducts action potentials?

A. Cell body
B. Axons
C. Dendrites
D. Schwann cell

B. Axons

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White ramus communicans

Carries myelinated preganglionic fibers

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Gray ramus communicans

Carries unmyelinated postganglionic fibers back to spinal nerve

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Paravertebral ganglia

Long chain, site of cell bodies of postganglionic sympathetic nerves

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Prevertebral ganglia

Anterior to abdominal aorta, site of synapses for preganglionic myelinated sympathetic neurons and postganglionic non-myelinated neurons

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Reflex Arc

Pathway that leaves from and returns to the CNS; minimally consists of afferent and efferent pathway

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Monosynaptic pathways

Consist of only afferent and efferent neurons; has a single synapse

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Polysynaptic pathways

Include interneurons in addition to afferent and efferent neurons; has multiple synapses

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Excitatory Postsynatic Potentials

Many synapses must simultaneously be firing in order to summate to produce an action potential

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Somatosensory axis

Sequence of structures involved in transmission of sensory signal from peripheral receptors to higher brain centers

Primary afferent neurons

Synapse in posterior horns of spinal cord or sensory nuclei in the brain

Secondary afferent neurons

Synapse in the thalamus

Tertiary afferent neurons

Synapse in the somesthetic areas of cerebral cortex

Skeletal Motor Nerve axis

Sequence of structures involved in transmission of an action potential from higher brain centers to skeletal muscles

Acetylcholine

Secreted by: pyramidal cells, neurons in basal nuclei, alpha motor neurons, preganglionic and postganglionic neurons; usually excitatory

Norepinephrine

Secreted by: neurons in brain stem, hypothalamus, pons, postganglionic neurons of sympathetic system; can be excitatory or inhibitory

Dopamine

Secreted by: neurons in substantia nigra; usually inhibitory

Glycine

Secreted by: synapses in spinal cord; always inhibitory

GABA

Secreted by: many areas in the spinal cord and cerebral cortex; always inhibitory

Glutamate

Secreted by: many sensory pathways entering CNS and areas of cerebral cortex; always excitatory

Electrotonic conduction

Direct spread of electrical current by ion conduction in dendritic fluids without generating an action potential

Decremental conduction

Gradual loss of potential as depolarization spreads from initiation site

Excitatory state (of neuron)

The summated degree of excitatory drive to the neuron; occurs when there is a higher degree of excitation compared to inhibition

What factors determine neuronal firing rate?

Excitatory state must be above the threshold for excitation; changes in excitatory rate due to superimposition of additonal excitatory/inhibitory signals can affect firing rate

Fatigue of synaptic transmission

Rate of synaptic firing decreases over time; exhaustion of transmitter substance in presynaptic terminals leads to progressive inactivation of postsynaptic receptors

What effects does alkalosis have on synaptic transmission?

Increases neuronal excitability; ex: epileptic seizures

What effects does acidosis have on synaptic transmission?

Depresses neuronal activity; ex: comatose state

What effects does hypoxia have on synaptic transmission?

Depresses neuronal activity; ex. loss of consciousness

What effects do caffeine, theophylline, and theobromine have on synaptic transmission?

Increases neuronal excitability by decreasing threshold for excitation

What effects does strychnine have on synaptic transmission?

Increases neuronal activity by inhibiting inhibitory transmitters

What effects do anesthetics have on synaptic transmission?

Decrease excitability by increasing threshold for excitation

Synaptic delay

Time it takes to transmit a signal from a presynaptic neuron to a postsynaptic neuron

What factors contribute to synaptic delay

Time it takes to release neurotransmitter from presynaptic neuron, time it takes for neurotransmitters to diffuse across synaptic cleft, how neurotransmitter acts on postsynaptic membrane, etc

What are the two main sources of blood supply to the brain?

Vertebral arteries and Internal carotid arteries

What is the Circle of Willis and why is it significant?

Pentagonal-shaped anastomosis of arteries uniting the two vertebral and two internal carotid arteries; provides collateral circulation to the brain

Which neurotransmitter is always excitatory, and is secreted by CNS sensory pathways and cerebral cortex? A. Glycine B. GABA C. Glutamate D. Norepinephrine

C. Glutamate