Lecture 1B: CNS Organization Flashcards
What is a nucleus in terms of nerves?
Group of dendrites and nerve cell bodies in CNS
How many pairs of spinal and cranial nerves are there in the PNS?
Spinal-31
Cranial-12
What is a ganglion in terms of nerves?
Groups of dendrites and nerve cell bodies in the PNS
What is a commissure?
Tract in the CNS that crosses f rom one side to another
What is the difference between white and gray matter?
White is myelinated
What does the splanchnic nerve supply?
Viscera
What is a reflex arc?
Pathway that leaves from and returns to the CNS
What is the difference between somatic and visceral pathways?
Somatic carries signals to skeletal muscle
Visceral carries signals to smooth or cardiac muscle
What is the excitation of a neuron typically due to?
Influx of Na+ ions
What is the inhibition of a neuron typically due to?
Influx of Cl- ion or efflux of K+ ion
T/F: An action potential is reached no matter how many synapses fire simultaneously.
False, the action potential is determined by how many synapses fire simultaneously
What is the somatosensory axis?
Pathway that carries sensory signal from peripheral receptors to higher brain centers
Where do the 3 series’ of afferent neurons (of the somatosensory axis) each lead to?
Primary- From peripheral receptors to CNS
Secondary- Primary neurons to thalamus
Tertiary- Secondary neurons to cerebral cortex
What is the skeletal motor nerve axis?
Pathway of transmission of action potential from higher brain cetners to skeletal muscles
What is acetylcholine secreted by and is it excitatory or inhibitory?
Pyramidal cells, alpha motor neurons, preganglionic neurons of ANS, postganglionic neurons of parasympathetic system, some postganglionic neurons of sympathetic system
Excitatory
What is norepinephrine secreted by and is it excitatory or inhibitory?
Brain stem and hypothalamus neurons, neurons in pons, postganglionic neurons of sympathetic system
Excitatory or Inhibitory
What is dopamine secreted by and is it excitatory or inhibitory?
Neurons originating in substantia nigra
Inhibitory
What is glycine secreted by and is it excitatory or inhibitory?
Synapses in spinal cord
Inhibitory
What is GABA secreted by and is it excitatory or inhibitory?
Spinal cord and cerebral cortex
Inhibitory
What is glutamate secreted by and is it excitatory or inhibitory?
Sensory pathways entering CNS, cerebral cortex
Excitatory
What form of transmission do dendrites use; action potentials or electronic conduction?
Electrotonic conduction
Why do dendrites exhibit decremental conduction of electrical potential?
They are long with thin membranes which causes the gradual loss
What is electrotronic conduction?
Direct spread of electrical current in dendrite without generating action potential
Why do dendrites not have action potentials?
The threshold is too high for it to be reached
What is the synaptic delay and what is the minimum time of delay?
Time it takes to transmit a signal from presynaptic to postsynaptic neuron.
Takes minimum of 0.5 seconds
What are the two blood sources to the brain?
Vertebral and Internal carotid arteries
What are the components of the Circle of Willis?
Posterior cerebral arteries Posterior communicating arteries Internal carotid arteries Anterior cerebral arteries Anterior communicating arteries
