Neurobiology Exam 1 (Real)

What are the primary cells of the nervous system?

glial cells & neurons.

What are Neurons?

excitable cells that transmit electrical signals.

what are Glial cells?

small cells that surround & wrap delicate neurons (support cells).

How does the nervous system produce outputs from inputs?

by receiving, integrating, and responding to info.

What are the primary functions of the nervous system?

To receive, Integrate, respond to Information.

Receiving ( Input );

(sensory ) sensory receptors detect changes in the external internal environment.

How does communication occur in the nervous system?

Through chemical & electrical signals.

integrating (processing )

(Interneuron) The information is sent to the CNS to be analyzed Is integrated to make decisions.

Responding ( output ) ;

( motor ) The CNS sends information back through motor components of the PNS through “effectors” (Cardiac, Skeletal muscles or glands) triggering a response.

What are the distinct systems of the NS?

The central nervous system & The peripheral nervous system.

How does species differ from individuals based on experience?

This Is so as differences arise from evolutionary adaptation to different environments.

How do individuals differ from species based on experience?

Experiences; The Nervous system is shaped by unique experiences; which can alter the way a circuit processes information.

What are the anatomical features of the neuron?

cell body (soma), dendrites, axon, axon hillock, axon terminal, Myelin sheath, & Nodes of Ranvier.

What are the structural units of the nervous system?

Neurons.

Neurons are …..

large, highly specialized cells that conduct impulses.

What are some special characteristics of neurons?

Extreme longevity, Amitotic & high metabolic demand.

Where does secretion of NT’s occur?

at the axon terminal.

What are the 3 main glial cells in The CNS?

astrocytes, microglia, oligodendrocytes.

Astrocytes are …

The most abundant versatile and branched cell in the CNS.

Function of astrocytes ;

Structural support, developmental guidance, chemical maintenance, metabolic regulation.

Structural support

asstrocytes cling to neurons, synaptic endings, and capillaries to provide branching

developmental guidance

astrocytes guide the migration of young neurons

metabolic regulation

astrocytes play a critical role in the exchange of materials between neurons and capillaries.

chemical maintenance

astrocytes control the chemical environment by cleaning up leaked K+ and by recycling/recapturing NTs.

What are microglia?

Small, ovoid cells with thorny processes that monitor & touch neurons. microglia are the defensive cells of the CNS.

What are the defensive mechanisms of microglia?

Monitoring, migrating & phagocytosis.

What are ependymal cells?

glial cells with epithelial characteristics, that line the brain's ventricles & spinal canal, and help circulate CSF.

What do ependymal cells form?

A permeable barrier between the CSF & CNS tissue fluid.

What are oligodendrocytes?

Branched CNS glial cells that form myelin sheaths around CNS axons.

how many axons can one Oligodendroalle myelinate?

up to 60 axons.

Do CNS myelin sheaths have gaps?

Yes.

What are Schwann cells?

PNS glial cells that form myelin sheaths around PNS nerve fibers (axon).

How many axons can a schwann cell myelinate?

Exactly one.

What is the schwann le myelination pattern called?

Jelly roll.

Why are Schwann cell membranes good insulators?

its membrane has low protein, leak channel & carrier content, making them excellent electrical insulators.

What is the cell/ plasma membrane?

a phospholipid bilayer with proteins embedded in It.

What is the phospholipid bilayer made up of?

polar, hydrophilic heads & non-polar hydrophobic tails.

What are the functions of a cell's plasma membrane?

Separate cell contents; Hydrophobic interior prevents ions from crossing; Allows different intra/extracellular ion concentrations.

What are ions?

an element or compound that carries charge, due to differing numbers in protons & electrons.

What is membrane Potential (Vm)?

The electrical potential inside the cell compared to outside.

What is resting membrane potential ( Vrest)?

between -70 & - 65 mV

simple diffusion;

passive, transport of molecules down their conc. gradient (small, non-polar molecules).

Facilitated diffusion;

passive movement across membrane with transport proteins.

Equilibrium potential;

The membrane potential at which a specific ion has zero net movement across the membrane.

Nernst equation;

Ex = 58 mv log ([x]out / [x]in).

What are the primary cells of the nervous system?

Glial cells & neurons.

When is equilibrium reached?

when both the electrical & chemical gradients are equal & opposite.

What are graded potentials

A small localized change in a neuron's membrane potential voltage whose size varies with strength.

What is electrophysiology

The study of electrical properties in cells (such as neurons).

What do you use to measure electrical activity

Electrodes.

What does the Nernst equation calculate

The equilibrium potential of a specific ion.

What is current clamp?

A current clamp controls current and measures membrane potential.

What does the current clamp also tell us

How voltage changes in response to current.

What does the current clamp not tell us

Which ion currents underlie voltage changes.

What does the voltage clamp measure

It controls voltage and measures current.

How does a voltage clamp determine ionic currents

The feedback current equals and opposes the membrane current, allowing calculation of ion flow.

What does positive current mean

Positive ions leaving the cell.

What does negative current mean

Positive ions entering the cell.

What is conductance

The degree to which the membrane allows an ion to flow.

What is passive conductance

Movement without voltage‑gated ion channels (typically dendrites).

When is the membrane more permeable to Na⁺

During depolarization.

What does Ohm’s law measure

The relationship between current, voltage, and resistance/conductance.

What is active conductance

Movement with voltage‑gated ion channels (typically axons).

Does passive conductance decay over distance

Yes.

Is active conductance constant over time

Yes — voltage‑gated Na⁺ and K⁺ channels regenerate the AP along the axon, so voltage doesn’t decay.

What is the concerning membrane permeability during the course of an AP

Membrane permeability to different ions changes during the course of an AP.

When is the membrane more permeable to K⁺

At rest, repolarization, and hyperpolarization.

Why is the membrane more permeable to K⁺ ions at rest

Because of K⁺ leak channels that maintain the resting Vm.

What does the Goldman equation measure

A cell’s membrane potential based on ion concentrations and relative permeabilities (Ca²⁺, Na⁺, K⁺, Cl⁻).

What is important to identify the amount of current flow at any given Vm

Conductance.

Goldman Equation

Ohm’s Law and Current Equation V = IA; Iion = gion(Vm − Eion)

V = IA; Iion = gion(Vm − Eion)

Conductance vs Resistance

Conductance is the inverse of resistance → g = 1/R

Nernst Equation (Body Temp)

Ex = 61.5 mV/z log ([X]out/[X]in)

What is reversal potential

The membrane potential where ionic current reverses direction (from inward to outward).

Are Na⁺ and K⁺ currents through different channels?

Yes.

Downward deflection represents what?

Inward current (negative current; positive ions entering the cell).

Upward deflection represents what?

Outward current (positive current; positive ions leaving the cell).

What toxin blocks the Na⁺ current?

TTX (tetrodotoxin); binds voltage‑gated Na⁺ channels and prevents Na⁺ influx.

What compound blocks the K⁺ current?

TEA (tetraethylammonium) ; blocks voltage‑gated K⁺ channels, preventing K⁺ efflux.

What happens to current when TTX is added?

Early inward Na⁺ current disappears, leaving only delayed outward K⁺ current.

What happens to current when TEA is added?

Late outward current is blocked, isolating early Na⁺ current.

Typical time course of Na⁺ current?

Early, transient, inward.

Typical time course of K⁺ current?

Late, sustained, outward.

What is the structure and function of axon terminals?

Axon terminals are small, branching endings of an axon that store and release neurotransmitters to communicate with the next cell across a synapse.

What causes the early inward current during depolarization?

Na⁺ entering through voltage‑gated Na⁺ channels.

What causes the late outward current?

K⁺ leaving through voltage‑gated K⁺ channels.

What experimental method holds membrane voltage constant while measuring current?

Voltage clamp.

What is the reversal potential?

The membrane voltage where net current switches direction (I = 0).

What is the reversal potential for Na⁺?

Approximately +52 mV.

What is the reversal potential for K⁺?

Approximately –68 mV.

Which toxin blocks Na⁺ channels?

Tetrodotoxin (TTX).

Which compound blocks K⁺ channels?

Tetraethylammonium (TEA).

What part of the membrane acts as the capacitor?

The phospholipid bilayer (insulator between conductive fluids).

Why does voltage change slowly when current is injected?

The membrane capacitance must charge.

What prevents action potentials from traveling backward (back propagation)?

Na⁺ channel inactivation (absolute refractory period).

How does myelin affect membrane resistance?

It increases membrane resistance (rm ↑).

How does myelin affect capacitance?

It decreases capacitance (C ↓).

What is saltatory conduction?

AP propagation jumping from node to node along myelinated axons.