Neuro Exam 1 Help Sessions

Neurons vs Epithelial Cells - common features

Both = POLARIZED, with structurally and functionally distinct compartments

Golgi Stain - how does it reveal the anatomy of the NERVOUS SYSTEM, which SCIENTISTS used it for the first time?

→ Golgi SILVER staining: labels a small fraction of neurons → allows for the individual neuronal anatomy to be seen

→ Ramon y Cajal used it to show neurons are DISTINCT cells

GLIAL cells - where does “Glia” come from?

“Glia” means GLUE, introduced by Rudolf Virchow

Does “Glia” (glue) accurately describe the function of GLIAL CELLS?

NO → performs many functions beyond just structural support.

-Homeostasis

-Myelination

-Immune Defense

-Developmental guidance

-Nutrient support

-BBB regulation

-Growth-factor production

Glial cell - which type plays a role for DEVELOPMENT of the nervous system

RADIAL GLIA - guide postmiotic neurons migrating to the appropriate layer during development

OLIGODENDROCYTES - main function?

Insulate axons with myelin in the CNA, one of them can wrap SEVERAL axons

LOCAL GRADED vs ACTION potentials - functions

Local graded = local electrical signals in response to synaptic or sensory stimuli

Action: all-or-none signals for long-range transmission along axons

LOCAL GRADED vs. ACTION potentials - stimulus intensity

Local graded: stronger stimulus = larger potential (amplitude) - bigger

Action: stronger stimulus = more frequent action potentials (higher frequency) -faster

T/F: Protein Kinases remove phosphate groups

FALSE - Kinases ADD phosphate groups, phosphatases are the ones that REMOVE phosphate groups

T/F: Ubiquitination is important for protein degration?

TRUE: ubiquitin acts as a “destroy this protein” TAG

→ marks proteins to be sent for degradation, commonly by a proteasome

T/F: All mitochondrial proteins are encoded by the nuclear genome

FALSE - most mitochondrial proteins are encoded by nuclear DNA, but mitochondria have their own DNA that encodes some mitochondrial proteins, tRNAs and rRNAs (not all are nuclear)

T/F: Secretory and membrane proteins are synthesized by ribosomes attached to the ER?

TRUE: proteins are made by ribosomes attached to the rough ER, the rough ER starts them on the pathway toward the GOLGI → final destination

→ protein leaving the cell or going into membrane = rough ER

T/F: Intermediate filament proteins are HIGHLY DYNAMIC cytoskeletal structures?

FALSE: they are highly STABLE, not highly dynamic

→ their main job is to provide structural strength to the neuron, especially the axon

T/F: MAP2c is a frequently used dendritic marker?

TRUE: MAP2c are associated with microtubules in DENDRITES

→ it therefore can be used to identify dendrites

MAP2=dendrites

T/F: All MT (microtubules) in axons have their PLUS ends oriented toward the terminal

TRUE: axonal MT have their + ends pointing toward the axon terminal/growth cone

→ this helps direct transport along the axon

→ this is why kinesin, which generally travels toward the + end, moves cargo toward the axon terminal

T/F: Dendrites are typically THICKER than axons?

TRUE: dendrites are generally thicker and more branched

→axons are thinner and longer

Slow Axonal Transport

→ involves LARGE cytoskeletal and cytoskeleton associated proteins as cargo

-Tubulin, neurofilaments, actin, and actin-associated proteins

-These are mainly used to build and maintain the neuron‘s cytoskeleton

SLOW=STRUCTURE

Intermediate Filaments - main functions

Mainly provide strength and structural support

Microtubules - main function

Provide the tracks for organelle transport

Microtubule Dynamics depend on…

GTP

-Tubulin binds GTP → GTP cap helps the MT grow and stay stable → los of the GTP cap promotes shrinking

ATP vs ADP bound actin

ATP-actin → more likely to ASSEMBLE

ADP-actin → more likely to DISASSEMBLE

ER - main function

Making proteins and lipids

Mitochondria - main functions

Responsible for most energy / ATP production

GOLGI and protein MODIFICATION

→ important for Glycosylation & targeting proteins to the appropriate subcellular compartment

*Think of it like a post office

1. Modify proteins, including glycosylation

2. Sorts proteins

3. Sends them to the correct destination

Different types of neurons = different compositions of membrane proteins like ion channels

• Neurons all use electrical signaling, but different neurons can have different ion channels, receptors, and other membrane proteins

→ these differences help neurons perform different functions

Protein Glycosylation

→ important for molecular recognition (sugar tags)

→ adding sugars to proteins

→ act as ID tags that help cells/proteins recognize and interact with each other

Neurons - protein synthesis

Can occur in DIFFERENT parts of the cell

→ most protein synthesis happens in the cell body and dendrites

→ but neurons can also make proteins locally in axons, nerve terminals, and growth cones

*Neurons can be extremely long, so making a protein LOCALLY is much faster than always waiting for it to come to the cell body

Axonal transport - ANTEROGRADE and RETROGRADE

• Can be directed in either direction

• Anterograde = cell body → axon terminal — kinesin

• Retrograde = axon terminal → cell body — dynein

A for anterograde → AWAY from cell body

R for retrograde → RETURN to cell body

Lengths of human axon

0.1mm to >1 meter

CNS Anatomy - 7 major portions and their function

• Spinal Cord: sensory transmission

• Cerebellum: fine movement control

• Medulla: respiration / BP (M for must live)

• Pons: cortex - cerebellum relay (bridge over the PONd)

• Midbrain: motor - system connections

• Diencephalon: sensory relay (thalamus, directs sensory info)

• Telencephalon: cognition / memory (T for TOP level thinking)

CNS order going upward Mneumonic

Spinal → Medulla → Pons → Midbrain → Diencephalon → Telencephalon

Smart Med People Memorize Difficult Things

Hippocampus - function and location

• Memory formation

• Medial temporal lobe of the Telencephalon

Why is Neuroscience an important discipline in life sciences?

1) Brain development / anatomy / physiology are major scientific challenges

2) Neurological disorders - major health problems

3) Neuroscience can aid to improve computers, sensors, and robotic devices

2 major distinct cell types - mediate many functions of the nervous system

Neurons and Glial cells

Main functions of neurons and glial cells

Neurons = signaling

Glial cells = maintenance/support or another specific glial function

Neuron vs Glial cells - common features

Both have ion channels, pumps, transmitter receptors, membrane potential, transmitters

Neuron vs Glial cells - distinct features

Glial cells - NOT polarized, do not form APs, and can divide

Local Graded vs Action Potentials

Local graded: small, proportional to stimulus, short-distance

Action: large, constant amplitude/frequency codes intensity, long-distance

Neuron Cell Polarity - why are they described as polar?

Neurons have morphologically and functionally distinct compartments

Two major COMPARTMENTS in neurons

1) Axonal compartment

2) Somatodendritic compartment

What is another polarized cell types that has been compared with neurons with respect to cell POLARITY?

Epithelial cells

• apical region vs base lateral region → one part of the cell is structurally & functionally different from another part

3 different types of Glial cells

1) Schwann - myelination, Oligodendrocyte - myelination

2) Astrocyte - homeostasis/nutrition/support

3) Microglia - immune

4) Radial Glia - neuronal migration

Role of Axonal Transport - How is it accomplished?

• Most protein synthesis occurs in the soma/cell body

• Proteins and organelles must travel along long axons using motor proteins on MTs.

What motor protein moves toward the PLUS end of MTs?

Kinesin

What motor protein moves toward the MINUS end of MTs?

Dynein

How did researchers figure out that the HIPPOCAMPUS is important for memory formation?

Patients with medial temporal lobes surgically removed had problems with memory formation afterwards.

3 Electrophysiological Recording Methods & their benefits

1) Extracellular: longer recording

2) Intracellular: control intracellular condition

3) Patch clamp: single ion-channel recording

T/F: the FURTHER away from the neuron of interest an electrode is placed, the LARGER the signal?

FALSE

Farther away = smaller signal, the neuron produces an electrical signal and that signal decreases with distance so an electrode closer to the neuron records a stronger/larger signal

Conductance Equation

I = Q/T

Current = charge flowing per time or charge/time

Conductance Equation

g = I/V

How easily a current can flow → current/voltage

Resistance Equation

R = V/I

How much something resists current flow

Resistance and Conductance

THEY ARE OPPOSITES

Capacitance Equation

C = Q / V

How much charge can be stored for a given voltage or charge / voltage

Nernst Equation

Ex = 58 mV/z *log out/in at RT