Oct2 M1-General Organization of the Nervous System

Question 1

PNS components

Answer 1

• afferent fibers (sensory)
• efferent fibers (motor)
• autonomic fibers (to enteric NS, heart, etc.)

Question 2

4 types of cells in NS

Answer 2

• neurons
• astrocytes (metabolic and structural support)
• oligodendrocytes (CNS) and Schwann cells (PNS): form the myelin sheath surrounding axons and speed conduction of action potentials (APs)
• microglia (immune cells of NS)

Question 3

charact of all neurons

Answer 3

• dendrites receiving excitatory or inhibitory synaptic input
• cell body (soma) (millimeter to meters long)
• axon (initial segment + rest of it)

Question 4

neuron output name

Answer 4

electrical spike called ACTION POTENTIAL

Question 5

axons function

Answer 5

• initiate and propagate APs
• APs are all or none events initiated when the membrane potential of the axon initial segment (part closest to cell body (soma)) depolarizes (-70 mV initially for example) to a an AP threshold (-50 mV for ex)

Question 6

how intensity of a stimulus is transferred (from skin surface fo rex)

Answer 6

• by FREQUENCY of APs

- not voltage of APs

Question 7

imp proteins for electrical properties of neurons

Answer 7

ion channels

-abnormal expression or fct = disorders

Question 8

myelin def

Answer 8

wrapping surrounding axons formed by oligodendrocytes in CNS or Schwann cells in PNS

• speeds conduction of APs (propagation)
• gives tissue a whitish appearance

Question 9

white matter content

Answer 9

bundles of myelinated axons

Question 10

grey matter content

Answer 10

cell somata, dendrites and synapses

Question 11

multiple sclerosis def

Answer 11

autoimmune disorder resulting in degradation of myelin in the CNS

Question 12

how neurons communicate

Answer 12

junctions called synapses

• most synapses are on dendrites
• 1. AP invades presynaptic terminal of presynaptic neuron
• 2. terminal releases a ntr that binds to a R on post synaptic cell, modulating its fct

Question 13

how ntrs are released from presynaptic terminal

Answer 13

• packaged in synaptic vesicles
• upon AP arrival to terminal, Ca channels of terminal open
• Ca enters terminal
• Ca allows vesicles fusion to cell membrane and dumping of ntr in synaptic cleft

Question 14

botulinum toxin (botox), tetanus toxin and black widow spider venom do what in common

Answer 14

interfere with complex molecular machinery responsible for vesicle fusion

Question 15

most synapses are on dendrites but where exactly

Answer 15

on specialized dendritic structures called dendritic spines (most synapses are on dendritic spines)

Question 16

3 types of synapses

Answer 16

• excitatory (most excit. use ntr glutamate)
• inhibitory (most inhib. use ntr GABA)
• neuromodulatory (use ntrs like serotonin (5HT), NE, dopamine, neuropeptides)

Question 17

how neuron determines when to fire an AP

Answer 17

with summation of excitatory and inhibitory synapses coming in (at dendrites, soma and initial segment)

Question 18

what is epilepsy

Answer 18

disorder of neuronal excitability, imbalance of excitation and inhibition is abnormal: too much excitation and or not enough inhibition. gives excessive neuronal activity

Question 19

what is synaptic plasticity

Answer 19

a process that plays a critical role in brain development and that is the cellular basis for learning and memory

Question 20

what is long term potentiation

Answer 20

experimental model of synaptic plasticity