Nervous system Flashcards

Question

What are the components of Ependymal Cells?

Answer 1

*Form simple epithelium that lines hollow portions of brain and spinal cord - Ventricles of brain - Central canal of spinal cord *Have cilia that help circulate cerebrospinal fluid in CNS

Answer 2

*Myelin sheaths are formed by oligodendrocytes in the CNS *Oligodendrocytes have many processes that wrap around many different axons *Result of myelination is increased speed of conduction of action potential

Answer 3

*In PNS *Surround cell bodies *Prevent “crossover” when many cell bodies are crowded together - Ganglia are full of cell bodies

Answer 4

*Surround axon, form myelin sheaths in PNS - Increase speed of action potential

Answer 5

*Myelin sheaths increase speed of action potential down axon - Myelin sheaths are made of Schwann cell’s compacted plasma membranes (made o phospholipids) →white in color *Also insulate axons from each other (prevents action potential “cross talk”)

Answer 6

*Schwann cell wraps around an axon *One axon will have numerous Schwann cells - Schwann cells do not touch each other - Gaps are left = nodes of Ranvier

Answer 7

*Action potentials jump over the myelin, jumping from node of Ranvier to node of Ranvier = Saltatory Conduction

Answer 8

*Only thick, fast conducting axons are myelinated - Thin, slower are not *Unmyelinated axons have a Schwann cell partly enclose 15 or more unmyelinated axons - Axons are separated *Slower conduction

Answer 9

*Autoimmune disease where myelin is attacked in CNS - Oligodendrocytes are destroyed - Plaques develop when myelin is destroyed - Inflammation develops and can damage axons *Overall: action potentials are disrupted causing motor and sensory issues

Answer 10

*In general, neurons have limited ability to regenerate or undergo mitosis - As a result, most brain tumors are derived from glial cells = glioma

Answer 11

Nerve *In PNS, axons of sensory and motor neurons *Example - Nerves off of spinal cord Nerve Tract *In CNS, axons of interneurons *Example - Corpus callosum of brain

Answer 12

*Most nerves contain both sensory and motor neurons - “Mixed” nerves are typical (ex. Spinal nerves)

Answer 13

*There are exceptions - Ex. Some cranial nerves are sensory (optic nerve) or motor (hypoglossal nerve) only

Answer 14

A nerve is an organ * Cells (axons of neurons, Schwann cells) * Connective tissue - Epineurium (dense irregular CT) - Perineurium (fibrous CT) - Endoneurium (over myelin, thin reticular) * Blood vessels

Answer 15

*Synapse = site where neurons communicate with each other or with other cell types

Answer 16

Nerve impulse: from presynaptic axon terminal to postsynaptic dendrite

Answer 17

*Presynaptic axons end at axon terminals *Within axon terminals are synaptic vesicles containing neurotransmitters * Neurotransmitters are chemical messengers * Ex. Acetylcholine, Norepinephrine *Neurotransmitters are released into a synaptic cleft (space between synapsing neurons) *Receptors on postsynaptic cell (dendrite or cell body) bind the neurotransmitters * This initiates an impulse or response

Answer 18

There are different types of neuron to neuron synapses * Axodendritic - Presynaptic axon to postsynaptic dendrite - Most common * Axosomatic - Presynaptic axon to postsynaptic cell body

Answer 19

*Some synapses are gap junctions between neurons (referred to as electrical synapse) *Not as common as chemical synapse (more common in invertebrates)

Answer 20

Higher than normal concentrations of some neurotransmitters can be toxic and these toxic levels have been shown to play a role in the degeneration of neurons associated with conditions such as: * Multiple sclerosis * Alzheimer's disease * Amyotrophic lateral sclerosis (ALS) * Parkinson's disease

Answer 21

*Means: “painful twitching” *Also called Trigeminal Neuralgia *Extremely painful chronic condition - A blood vessel compresses the trigeminal nerve causing loss of myelination of sensory nerve fibers - The lack of insulation allows touch and pain nerve fibers to cross-talk - Touch is perceived pain by brain

Answer 22

In the PNS * If only axon is destroyed (not cell body), Schwann cells help axon sprout through a regeneration tube * There can be partial recovery

Answer 23

In the CNS - Historically, there has been the “no-new-neuron doctrine” -- Once neurons die, they are not replaced by new neurons - HOWEVER...recently, neural stem cells have been discovered in the brain -- In the hippocampus (memory center) and olfactory bulb (smell) * The implication have profound potential for brain and spinal cord injuries *And, that you actually can teach an old dog new tricks!