Neuron

Question 0

what are the four components of the neuron?

Answer 0

• cell body
• axon
• dendrites
• synaptic terminal

Question 1

What is a neuron?

Answer 1

basic functional unit of the nervous system
nerve cells that form the conducting system that carries information throughout the peripherial and central nervous system

Question 2

Cell body

Answer 2

soma; place where incoming signals from dendrites are summed (which determines whether the neuron will fire or not fire)
- contains nucleus and organelles that are surrounded by the cytoplasm = perikaryon

Question 3

Dendrite

Answer 3

receive incoming afferent info (many dendrites for a neuron)

Question 4

Axon

Answer 4

usually single axon, although it can synapse on more than one cell
efferent
conductive unit of neuron, can be up to a meter long

Question 5

Synaptic terminal

Answer 5

at end of axon; high concentration of synaptic vessicles containing neurotransmitters

Question 6

What are the three common structures of axons?

Answer 6

1. multipolar
2. bipolar
3. unipolar

Question 7

multipolar axons

Answer 7

multiple dendrites, single axon in opposite direction to dendrites

Question 8

Bipolar neuron

Answer 8

single dendrite, single axon in different directions

Question 9

psuedounipolar neuron

Answer 9

axon that extends in two directions, one to spinal cord, other to peripheral nervous system

Question 10

Axon hillock

Answer 10

conical elevation of cell body from which single axon extends

Question 11

Nissl bodies

Answer 11

equivalent to RER in neuron, found only in soma and dendrites, axon has no organelles (stain dark)

Question 12

Neurofibrils

Answer 12

contain microfibrils and neurofilaments that extend from soma into dendrites and mediate slow and fast axon transport

Question 13

Nerve fiber

Answer 13

axon and myelin sheath

Question 14

What are the two different cells that form the myelin sheath ?

Answer 14

Schwann cells in the PNS (each Schwann cell associates with one neurons)
oligodendrites in the CNS (an oligodendrite can associate with many neurons)

Question 15

Myelin sheath

Answer 15

electrical insulator that prevents current from diffusing across the cell membrane as it travels down the axon; interupted at pts by nodes of ranvier that contain Na channels where AP can be generated (saltitory conduction, much faster than movement in unmyelinated cells)

Question 16

What are the other structures surrounding the nerve fiber in the peripheral nervous system

Answer 16

endoneurim: delicate connective tissue covering of a single nerve fiber
perineurim : more extensive layer of connective tissue surrounding a bundle of nerve fibers
epineurium : connective tissue sheath that surrounds entire peripheral trunk

Question 17

Types of sensory nerve receptors

Answer 17

carry information to the spinal cord, afferent

1. Exteroreceptors (pain, temp, touch pressure) in skin and connective tissue
2. Proprioceptors : position and stretch in muscles, tendons and joints
3. Visceroceptors : stimuli from visceral organs and circulatory system

Question 18

What type of nerve are sensory neurons

Answer 18

pseudounipolar

Question 19

Ependyma

Answer 19

epithelial cells that surround the spinal cord (line the central spinal canal) and produce cerebrospinal fluid

Question 20

Satellite cells

Answer 20

provide metabolic and structure support to sensory neurons

Question 21

What is white matter made up of?

Answer 21

myelinated axons

Question 22

What is gray matter made up of?

Answer 22

cell bodies, dendrites, and synapses (butterfly part of spinal cord)

Question 23

What propagates signal faster, large axons or small axons?

Answer 23

large axons

Question 24

What is the cytoskeleton in axons made of?

Answer 24

spectrin (microfilament and neurofilaments transport organelles and other substances up and down axons)

Question 25

What and how do substances (organelles, proteins, etc) move up and down axons

Answer 25

anterograde ( kinesins and slow anterograde movement that consists of the axon squeezing proteins slowly down its length (squeezing is how the axon transports cytosolic proteins)
retrograde (dyenin)
- kinesin transport is 100*s faster than simple diffusion
- different types of kinesin and dyenin are active in different cells

Question 26

How do axons regrow and where?

Answer 26

process of axon regeneration is active in the peripheral nervous system (blocked in the CNS by oligodendrites);
if axon gets severed peripheral part degenerates and then glial cells release trophic factors that induce growth at the split (slow process because it requires new materials)
- all areas of the body have the potential to regerate axons, but blocked in CNS by oligos

Question 27

What are the types of glial cells?

Answer 27

Astrocytes (ectodermal origin)
Radial glia
Microglia (mesoderm)
Oligodendrocytes (ectoderm)

Question 28

Function of astrocytes

Answer 28

structural support, physical isolation of neurons; buffer extracellular ions (K+ sink); uptake and clearance of neurotransmitters; metabolic support; secretion of growth factors; injury response; component of blood brain barrier

Question 29

Radial glia cell function

Answer 29

provide tracts for neuronal migration during brain development
mutations results in dramatic brain malformations that can cause death or severe mental retardation
youngest cells are closest to the pial surface

Question 30

Microglia function

Answer 30

macrophages of the brain (injury response)

Question 31

Where are the white and gray matter in the brain?

Answer 31

reverse of spinal cord (white inside, gray outside)

Question 32

What are the classic cells of the gray matter cerebral cortex?

Answer 32

pyramid cells (shaped like a triangle) ; thick branching dendrite at apex and then an axon that extends into white matter

Question 33

How many layers does the gray matter of the cerebral cortex have?

Answer 33

6

Question 34

Three layers of the cerebellar cortex

Answer 34

outer molecular layer
Purkinje cells
inner granular layer