Chapter 12 Flashcards by Susan Heritage

what are Nissl bodies

neuronal rough ER

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how many spinal nerves are there

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what is lipofuscin

product of lysosomes

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what is a ganglion

cluster of neuronal cell bodies in PNS

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what is the trigger zone

where nerve impulses arise (axon hillock and initial segment)

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what is the axolemma

neural cell membrane

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what are varicosities

contain synaptic vesicles

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what is the difference between slow and fast axonal transport

fast–200-400mm a day, moves both directions
slow–1-5mm a day, only in anterograde direction, contains axoplasm

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where are multipolar neurons found

CNS, motor neurons

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where are bipolar neurons found

eye, ear, olfactory area

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where are unipolar (pseudo bipolar) neurons found

ganglia of spinal and cranial nerves

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what is the difference between protoplasmic astrocytes and fibrous astrocytes

protoplasmic in grey matter with short processes, fibrous in white with long branched processes

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what is the function of astrocytes

strength, secrete chemicals to maintain selective permeability of endothelial cells in BBB, growth and development of embryo, help regulate ion concentration and nerve transmission, help form synapses

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what are ependymal cells

cuboidal/columnar cells possessing microvilli and cilia, produce and assist in circulation of CSF

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what are satellite cells

regulate exchange of materials between cells and interstitial fluid

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what is a nucleus (vs ganglion)

cluster of cell bodies in CNS

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nerve vs tract

nerve is PNS, tract is CNS

what are the 3 factors that lead to resting potential

unequal distribution of ions, inability of most anions to leave the cell,Na/K pumps electrogeneicity

what is decremental conduction

graded potentials diminish as they spread along the membrane through leak channels

what is threshold for AP

-55mV

what is the sequence of events during AP

depolarization, VG Na channels open (voltage to 30mV)
Depolarization, Na gates close, K+ channels open, and K+ leaves cell
Hyperpolarization, outflow of K+ causes membrane potential to drop to -90mV

What causes the refractory period?

Inactivated Na+ channels, smaller diameter axons have longer refractory periods

What is saltatory conduction?

In myelinated neurons, current “leaps” from node to node due to channels primarily occurring at nodes

What are the factors that affect propagation speed?

amount of myelin. axon diameter, temperature

What are A fibres?

large diameter, myelinated, brief refractory period and fast transmission. Occur in somatic sensory neurons and motor neurons

What are B fibres

medium diameter neurons, myelinated, medium speeds (15m/s), autonomic motor neurons and sensory neurons from viscera to brain

What are C fibres

smallest diameter (0.5-1.5um), slowest transmission and longest refractory periods, unmyelinated. Pain impulses from viscera, some somatic sensory signals, heart, smooth muscle, glands, and other motor functions for autonomic movement.

What are the main advantages of electrical synapses (gap junctions)

faster, synchrony

What is the synaptic delay?

0.5 miliS, for chemical signal to transmit across synapse

How are NTs removed from synapse

1. diffusion 2. enzymes 3. reuptake

What are neurosecretory cells

secrete hormones

What AA is used to synthesis catecholamines?

tyrosine

What is the role of NO

excitatory, vasodilation

what are some examples of neuropeptides?

enkephalins, endorphins, dynorphins

What is substance P

transmit pain signals

What is a reverberating circuit

neurons further in the cycle stimulate neurons earlier in the cycle (ie breathing, coordination of muscles, arousal, short term memory

what is parallel after discharge circuit?

single presynaptic cell stimulate a group of nuerons which converges on a single postsynaptic cell. used for precise activities

what is epidermal growth factor?

stimulates cells in hippocampus

What factors affect neurogenesis in brain and spinal cord?

1. oligodendrocytes 2. absence of growth factors

What happens after axonal injury in PNS

1. Chromatolysis (Nissl bodies break up) 2. Distal part of axon to injury breaks up 3. Wallerian degeneration (degeneration of distal portion of axon and myelin sheath 4. proteins and RNA synthesis, Schwann cells divide and form regeneration tube Prevented by scar tissue or large area