Cellular Neuro exam 1

Rough ER

Synthesize proteins

Smooth ER

post-translational modifications

What does yawning help your body do?

It is a behavior intended to increase the supply of oxygen in the body, to help fuel your cells. The same occurs when you eat a snack, you’re replenishing your body’s sugar.

Mirro neurons

imitate behavior

reservoir for calcium

• mitochondria

• endoplasmic reticulum

What is calcium calmodulin-kinase? What transcription factor does it act on?

It’s a signaling molecule. It acts on CREB to affect gene transcription.

What regulatory roles does internal calcium play in the neuron?

1. 2nd messenger signaling

2. Voltage-gated channels

3. Ligand-gated channels

4. Gene expression

Explain how the cytoskeleton moves cargo.

There are motor proteins (kinesin and dynein) that “walk” the cargo down the axon, either anterogradely or retrogradely.

What is fast anterograde transport vs slow anterograde transport?

• Fast ( 40 cm/day): kinesin-dependent and mostly vesicle transport

• Slow ( 0.5 cm/day): kinesin-independent and mostly non-vesicle transport

Why would we want to move cargo from the nucleus to the axon terminus? What are we moving?

Enzymes are made in the nucleus, which are used to synthesize NTs at the axon terminus.

classical neurotransmitters

made at all times, key for neuron’s normal function, stored in reserves -> slow anterograde transport.

non-classical neurotransmitters

not made all the time, made on demand for the moment -> fast anterograde transport.

The receptors on neurons are to most water-soluble molecules.

Impermeable

Do the “anchor” receptor proteins move or stay stationary? What is their function?

hese proteins are free to move about on the surface of the membranes. They function as receptors for EXTRAcellular signals -> signaling, amplification, relay/signal transduction.

CAN pass phospholipid bilayer

Gasses (o2) and small POLAR molecules (H2O, ethanol)

Aquaporins

Proteins that move H2O across cell membranes.

What are ionotropic gated ion channels?

Allow an opening for ions to move into the cell.

ion channels are located on

• dendrites

• cell bodies

• axon

• axon hillock

• axon terminals

Primary Erythromelalgia

A mutation in SCN9A (encoding a sodium channel alpha subunit). Originally thought to be psychological. Rare, autosomal-dominant painful condition -> burning of feet and hands, increased skin temp.

How is the signal transmitted from one point to another within a neuron?

By a transient change in the electric field and its associated voltage (potential).

amino acids

• Glutamate

• Acetylcholine (ACh)

• GABA

• Glycine

Catecholamines

• epinephrine

• norepinephrine

• dopamine

• serotoni

• histamine

Briefly describe the knee-jerk reflex. What causes contraction vs. flattening?

ACh release onto the extensor muscle -> contract. GABA is released by the inhibitory interneurons onto flexor motor neuron, inhibiting it, thus reducing ACh release onto the muscle -> flattens.

What NT is released onto the motor neuron (flexor) when the interneuron is activated?

GABA

Are we recording APs from the neuron or the synapse?

Synapse

What are the 3 types of local APs?

1. Receptor potentials

2. Synaptic potentials

3. Graded potentials

What determines whether a neuron fires?

summation of local potentials

What is an MRI? What does it allow us to see?

Brain imaging technique. Trace brain activity & visualize the brain. Allow clinicians to observe abnormal growth, tumors, strokes. Ex: fibromyalgia decreases cortical thickness in discrete brain regions

fibromyalgia

Neuropathological condition causing pain, decreased cortical thickness in discrete brain regions. Imaging technique: MRI

excitable cells

• neurons

• muscle cells

• cardiac cells

What is equilibrium potential voltage for K+ and when is it reached?

-85 mV

What is resting potential voltage for the entire neuron and when is it reached?

• -70 mV

• Reached when the neuron is not being stimulated

If you have high K+ concentration inside the cell, where does it move?

Outside via passive diffusion

Neurons have a stable resting membrane potential (RMP), known as an ____ property of the cell.

intrinsic

The RMP is due to what 2 factors?

• The ionic separation is due to the presence of various pumps such as theNa+/K+ pump.

• The permeability of the membrane to those ions

Can ions simply just cross the cell membrane? Why or why not? Explain how they cross.

Because they are charged, must cross via ion transporters or ion channels

For any given ion, its distribution across the membrane is determined by what 3 factors?

• chemical gradient

• electrical gradient

• permeability

Equilibrium potential = ____ potential

Nernst

Maintaining the RMP is an active or inactive process? 

Active. Na+/K+ pump -> use ATP

Is the RMP the same as an equilibrium potential? Why or why not?

No, because it relies on the constant expenditure of ATP by ion pumps for its maintenance. The permeability of the channel is higher for K+ than Na+.

Why is the K+ current 0 when the voltage is at around -100mV in an IV plot?

Current for K+ at -100mV at 0 because it matches the equilibrium potential for K+ (-85mV +/-10mV).

Why is the K+ current NOT = 0 when the voltage is LESS than -100mV in an IV plot

Because K+ wants to flow BACK into the cell to match the K+ equilibrium potential again and make the cell more positive to reach -85mV.

Why is the K+ current NOT = 0 when the voltage is GREATER than -100mV in an IV plot (aka, the voltage is WAY more positive?

Because K+ wants to flow OUT into the cell to match the K+ equilibrium potential again and make the cell more negative to reach -85mV.

What is the GHK equation used for?

Used to calculate the overall resting membrane potential of a cell by accounting for multiple ions at once (typically Na+, K+, and Cl-), rather than just one ion like the Nernst equation does.

What is produced in the nucleolus?

rRNA

Unstable, half-life of 10 minutes in a nondividing cell unless stabilized by GTP?

microtubules

Golgi apparatus cis face from which molecules are discharged in secretory vessicles

receiving end

Golgi apparatus back end from which molecules are discharged in secretory vessicles.

trans face

Based on Sherrington’s 1897 observations which was evidence AGAINST purely synaptic transmission?

Transmission showed delay even in one-synpase reflex

which cell type arises from progenitors of blood cells outside the CNS, similar to macriophages?

Microglia

Knee-jerk reflex

• The sensory neuron directly excites the motor neuron to the extensor muscle

• A spinal interneuron inhibits the motor neuron to the flexor muscles

Based on the NERNST equation calculations shown for the squid giant axon at room temp, approximately what is ENa+?

+54.8 mV

Why isn’t the resting membrane potential simply the average of the Nernst equilibrium potentials for Na+, K+, and Cl-?

• The membranes permeability differs for each ion

• K+ dominates

which ion is the resting membrane potential dominated by

K+ equillibrium potential

For a positively charged ion the membrane potential is more ___ than the quillibrium potential, the direction of flux is _____

more positive; out of the cell.

For a positively-charged ion, if the membran potential is ___ than the equillibrium potential, the direction of flux is _____

more negative; into the cell.

Ernst equation

V= equillibrium potential

C= concentration of ion

z= charge of ion

Goldman-Hodgkin-Katz Equation (Vm)

modification of the Nernst equation to include the relative permeabilities (P) of each ion

K+ (40)

Na+ (1)

Julius Bernstein predicted the peak of the action potential would be approximately

• 0 mV

• believed AP was due to a breakdown in membrane resistance

• thought membrane would be permeable to all ions.

early inward current

• carried primarily by Na+

• In a Na+ free solution, the early current becomes outward rather than inward

• reverses at potentials more depolarized than ENa+

delayed recifer

the delayed, slow-to-activate K+ conductance during the action potential

Sodium channels inactive during sustained depolarization, but potassium channels do not

if the cell is depolarized they are open

According to the phases of the action potential, threshold (-50mV) is defined as the membrane potential at which

All volatge-gated Na+ channels begin to open, an all or none event

which membrane protein type transports molecules across the membrane against a gradient via a series of conformational changes

channels

Which of the following are components of the “epithelial blueprint” of neurons ?

• Cell membrane

• cytosol

• membranous organelles

Approximately how many of the 20k human genes are expressed in the developing or adult brain?

14k

Which step of translationis descrived as the rate-limiting step

initiation

Which ER-associated calcium store is activated by elevation of cytosolic Ca2+ itself, and is also modulated by caffeine?

The ryanodine-sensitive store

cell body where metabolic processes occur

soma

biogenic aine

seratonin and histamine

myelin increase the speed of action potential conduction along an axon primarly by

increasing membrane resistance and decreasing capacitance

At 37 degrees C for a monovalent cation, the Nernst equaion reduces to which simplifies version

V = 61.5log10(Co/Ci)

According ot the mammalian neuron values given 37C what is the Ek+

-92.9 mV

Ek+ for the squid giant axon at 20C

-75.5mV

Kenneth Cole and Howard Curtis were first to demonstrate which phenomenon during an action potential?

An increase in membrane conductance (decreased resistance)

The generator potential depolarizes the cell by _______ cation channels

opening ligand-gates

What is the term for the phenomeon in which Na+ and K+ conductance both increase as the membrane depolarized

Rectification

Electrical synpass are very

fast and BIDIRECTIONAL

classic neurotransmitters

small and clear vessicles

neuropeptides

large and dense vessicles

EPPS are multiples of

MEPPS

increases probability of neurotransmitter release

Calcium

An EPSP has a reversal potential more ________ than the AP threshold

Positive

IPSP has a reversal potential more _________

Negative