Purdue BIOL 436 Quiz 1

Neurons, glial cells

Main cell types in nervous system

10^11

How many neurons are in the adult human brain?

Post-mitotic

Mature neurons cannot divide meaning they are ___ and highly specialized for intracellular communication

Polarized

Neurons have structurally and functionally distinct compartments meaning they are highly ___ cells

Cell body

Nucleus stores genetic information

ER and Golgi complete protein synthesis

Dendrites

Receive information from other neurons

Axons

Conducts information to send to other neurons

Presynaptic terminal

Where an electrical signal is converted to a chemical signal

Presynaptic terminal, synaptic cleft, postsynaptic membrane

Parts of the synapse

10^-6 grams

Mass of a large sensory neuron

Single cells, syncytium

Ramon Cajal used Golgi’s silver staining technique to show neurons are ____ and do not form a ___(not fused together). Silver staining only labels 1% of all neurons

Single unit is a distinct cell

Cajal’s neuron doctrine

Signal travels in one direction

Cajal’s Principle of polarization

Nerve cells form orderly networks with layers

Cajal’s Principle of connectional specificity

Growth cones were discovered, synapses exist

Cajal’s rule of distinct shapes

Unipolar cell

The image above is an example of a _____

Bipolar Cell

The image above is an example of a _____

Pseudo-unipolar cell

The image above is an example of a _______

Motor neuron of spinal chord, pyramidal cell of hippocampus, purkinje cell of cerebellum

What are the three types of multipolar cells

Multipolar cells

What type of cells are shown?

1. Golgi silver staining

2. Fluorescent markers

3. GFP expression

4. Labeling with immunocytochemistry

What are the 4 techniques for identifying neurons and connections?

Sensory neurons

Receive information from periphery

Motor neurons

Send information to periphery

Interneurons

Projection neurons (long) and local interneurons (short)

1. Input component (dendrites/cell body)

2. Trigger component (axon hillock)

3. Conductive component (axon)

4. Output component (presynaptic terminal)

What are the 4 signaling components of neurons

Frequency

The stimulus intensity determines the _____ of the action potentials. (Something very intense happens the AP marks would be very close together)

Stimulus duration

The ________ determines the number of action potentials

Electrical signals

_____ (potentials) are used for long distances (along the neuron)

Chemical signals

_____ (transmitters) are used for short distances (between neurons)

Membrane potential

Electrical signals are changes in the _____ that travel along the neuron and are a result of unequal ion distribution and permeability

Passive propagation

Local graded potentials are a result of _____ meaning they are not actively regenerated and do not last a long time

Action potentials

____ have large amplitude changes that are all or none and can travel long distances

Rudolf Virchow

Where does the glial cell name come from?

80% of brain neurons

The cerebellum is only 10% of brain mass but contains ____

81.8% of brain mass

The cerebral cortex only contains 19% of brain neurons but makes up

Provide support/fills gaps

Guides migrating axons and neurons during development

Maintenance

Structural support

Providing nutrients to neurons

Immune function

Myelination insulation

Production of growth cells

Secretion of CSF

What are the functions of glial cells?

Radial glial cell

Type of glial cell that guides migrating axons and neurons during development

Astrocytes

Type of glial cell that manages structural support, chemical environment, supply neurons with nutrients, production of growth factors in ECM

Schwann cells (PNS)

Type of glial cell that provides nutrients to neurons and myelination insulation of an axon. One of these wraps one axon.

Microglia

Type of glial cell that manages immune function and removes debris

Oligodendrocyte

Type of glial cell that provides myelination insulation of an axon

Ependymal cell

Type of glial cell that determines secretion of cerebrospinal fluid

Microglia and macroglia (astrocytes, oligodendrocytes, ependymal cells, radial glia, and Schwann cells)

Types of glial cells

Immunological cells of the nervous system

Microglia function as the ____

GFAP

Astrocytes are the most abundant glial cell in the CNS and ____ is one of their marker proteins

1. Take up potassium ion after neuronal firing

2. Transmitter (glutamate) uptake from synaptic cleft by Astrocytes

What are the two ways Astrocytes can control the chemical environment of neurons?

Glutamate, glutamine, presynaptic neuron

In the glutamate-glutamine cycle, _____ is taken up by glial cells, converted to _____ and released be the glial cell and then taken up by the _______

Astrocytes glial end feet

Regulate the development of the BBB which is made up of endothelial cells

Direct connections, gap junctions

Astrocytes control exchange of metabolites between capillary and neurons but do not have ____ with neurons. They also form ____ among themselves

Myelin

Compact arrangement of plasma membrane with special proteins and lips. Composition is different in CNS as compared to PNS

Radial glia

Postmitotic neurons migrate to the appropriate layer along ____ during development

Nodes of Ranvier

Non-myelinated spaces in Schwann cells where sodium-channels are highly concentrated

Membrane potential

-75

Action potentials

Polarized

Glial cells have ion channels, ion pumps, transmitter receptors, produce neurotransmitters and have a 1.____ ____ that is slightly more negative than a neuron (2.____mV) but do not form 3.__ and are not 4.____

Fast and directional signaling

Main function of neurons

Electrical excitability, polarization

Two key features of neuron signaling

Leading process, trailing process

Axonal-dendrite polarity is initiated during the neuronal migration in the developing mammalian brain where the ___ develops into dendrites and the _____ develops into the axon

1. Selective delivery of protein

2. Selective fusion of membranes

3. Selective retention of proteins

How neuronal polarity is established and maintained

Early maintenance

Microtubule based organelle delivery

Lateral diffusion

Endocytosis

Retention in lipid rafts

Are all forms of what type of neuronal polarity

Late maintenance

Membrane protein-cytoskeletal interactions at hillock prevent lateral mixing of membrane proteins between axons and dendrites. What type of neuronal polarity is this?

Axon, dendrite

____ can be myelinated, but ____ is not myelinated

Axon, dendrites

Voltage gated Na+/K+ channels are associated with the ____ while neurotransmitter receptors are _____

Plasma membrane

• asymmetric lipid bilayer

• Maintains intra and extracellular concentration of ions, metabolite, and transmitters

Cytosol

Contains soluble proteins: enzymes with metabolic functions: signaling proteins are often at the cytoskeletal-membrane interface

Cytoskeleton

Functions include cell division, shape determination, motility, and organelle transport. Made up of microtubules, actin filaments, and neurofilaments.

25%, Tubulin

Cytoskeletal plus associated proteins account for ___ of the neuronal protein. ____ makes up 10% of the total brain protein

Microtubules, beta

__ are made of 13 pro filaments made from alpha and beta dimers. Plus end is on the ___ subunit

Dimer, GTP cap, MAPs, tau, MAP2

Microtubule dynamics:

Rapid changes of growing and shrinking is regulated by free _____ concentration, rate of GTP hydrolysis, and MT-associated proteins.

__ ___ favors Microtubule growth

___ can stabilize microtubules.

MAPs as marker proteins: _____ is an axonal marker, ____ is specific to dendrites.

Grows

When the rate of subunit addition exceeds the rate of GTP hydrolysis the Microtubule ___

Shrinks

When the rate of GTP hydrolysis exceeds the rate of subunit addition the Microtubule _____

Long-range

Microtubules provide tracks for ____ protein and organelle transport between the neuronal cell body and the nerve terminal

Kinesin motors

Mediate either plus or minus end oriented transport in the Microtubule

Dynein motors

Minus end-oriented transport in microtubules

Axons

All MT plus ends are oriented towards the growth cone

Dendrites

Mixed MT polarity in higher organisms (vertebrates)

F-actin

Conserved abundant protein where the plus end is the growing end. Associated with ATP/ADP binding. Provides structural support and growth cone motility and guidance

Neurofilaments

Stable intermediate filaments. Tetramer where fiber is NOT POLARIZED. Provides STRENGTH to the axons

Nucleus, mitochondria

Genetic information is mainly stored in the ___ and some in the ____

Translation

Most of the ____ occurs in the cell body and dendrites

Cytosolic

____ proteins are translated or free ribosomes

Bound ribosomes

Secretory and membrane proteins are synthesized by ____ attached to the RER

C-terminal KDEL

Classical ER retention signal is the ___ _____ sequence

Glycosylation

Molecular recognition in ER or golgi: N-linked/C-linked

Phosphorylation/Dephosphorylation

Signaling molecules and protein function. TYR kinases in the SRC and SER/THR kinases in the PKC/PKA

N-acylation

Membrane association. Miristoylation in SRC

Isoprenylation

Membrane association. Ras GTPase.

Ubiquitination

Protein degradation. Ubiquitin: 76 AA

1. Modification of proteins

2. Sorting and targeting of proteins into different vesicles

Two major functions of golgi complex

1. Recycling of synaptic vesicles

2. Keeping the neuron the same size

3. Regulation of number of receptors in plasma membrane

What are 3 reasons endocytosis is important in neurons?