Exam 1

What are Neurons + their anatomy

What are Neurons + their anatomy

nerve cells — basic cellular units of the nervous system
dendrites, soma, axon (with myelin), terminal

What are Dendrites?

fibers with synaptic receptors: receive information from neurons

What is the Soma + its function

cell body — neuron’s metabolism occurs here, tells neuron which neurotransmitter to release; may have synapse

What is an Axon + its function

long fiber that conveys an impulse

What are Axon Collaterals + what they do

axons branching out of a main axon — one neuron can talk to multiple neurons

What are Presynaptic Terminals?

point where axon releases chemicals — synaptic transmissions

What are Neurites + properties

outgrowths from a soma — dendrites and axons
chemosensation — sample the environment by sensing chemicals

What is the Synapse + Synaptic Cleft?

point of functional connection between two neurons & separates two neurons

What are Neurotransmitters + their activity

chemical signals released by presynaptic neuron
diffuse across synapse
received by postsynaptic neuron
→ converted from chemical to metabolic/electrical

What are the neuron’s Electrical and Chemical properties?

electrical activity: action potential
chemical signaling: neurotransmitter release

Neurons are __, __, and __ active

electrically, chemically, and metabolically

What are Glial Cells

glial = glue
physical support — brain firmness and structure

Main types of Glia

oligodendrocytes: myelin for CNS
Schwann cells: myelin for PNS
astrocytes: nutrition, synapse formation and maintenance, remove dead cells & K+

Main functions of Glia

nutrition, ionic balance, removing neurotransmitters from synapse

What are functions of Microglia?

mobilized after neural injury/death — fights infection and disease

Glia Pathology

malignant tumors — often growth of astrocytes
multiple sclerosis — loss of oligodendrocytes
Type 1 Charcot-Marie-Tooth disease — demyelination of Schwann cells

Efferent vs. Afferent

efferent — carries information out
afferent — brings information in

Motor Neuron + location

efferent — carries information to muscle
ventral horn of spinal cord

Sensory Neuron + location

afferent — brings information to brain
dorsal horn of spinal cord

T/F: A single neuron can span both CNS and PNS

TRUE

T/F: Glial cells can sometimes be electroactive

TRUE

T/F: Blood is neurotoxic

TRUE

Important ions for Electrophysiology

Na+, K+, Cl-, Ca++

Which channels are mostly closed?

Na+ and Ca++

Which channels are mostly open?

K+ and Cl-

Which ions are mostly extracellular?

Na+, Cl-, Ca++

Which ion is mostly intracellular?

K+

Why is the resting membrane potential negative?

neurons have machinery to keep it negative.
- Na+ (cation) actively pumped out
- energy spent to pump out Na+

Most important ions for action potential generation

Na+ and K+

What causes ions to move in and out of cell membranes?

electrochemical gradient forces

___ changes membrane potential

ionic movement

Ions no longer move when ___

equilibrium is reached

Concentration Gradient

Molecules will diffuse from areas of high to low concentration

Electrical Gradient

Ions attracted to opposite electrical charges and repelled by similar electrical charge

Equilibrium potential

voltage at which concentration and electrical gradient of ion are balanced

Cl- equilibrium potential

-70 mV

K+ equilibrium potential

-90 mV

Na+ equilibrium potential

+60 mV

T/F: Na+, Ca++ and K will move in the direction of their concentration gradient

TRUE

How does the neuron become excited?

Permeability/influx of Na+ → inside voltage moves in positive direction

T/F: Chemical gradient is stronger than electrical gradient

TRUE

Excitatory Post Synaptic Potential (EPSP)

influx of cations / efflux of anions (change of voltage in positive direction)
DEPOLARIZATION

Inhibitory Post Synaptic Potential (IPSP)

influx of anions / efflux of cations (change of voltage in negative direction)
HYPERPOLARIZATION

Primary inhibitory & excitatory neurotransmitters in CNS

inhibitory: GABA
excitatory: glutamate

Primary neurotransmitters in PNS

norepinephrine & acetylcholine

When Glutamate released…

Depolarization

When GABA released…

Hyperpolarization

T/F: Post-Synaptic Potentials are graded (small sub-threshold events)

TRUE

T/F: Post-Synaptic Potentials decay over time

TRUE

Glutamate-Mediated Excitation

POSITIVE — Na+ ions move into cell

GABA-Mediated Inhibition

NEGATIVE — Cl- ions move into cell

T/F: Action Potentials will always be the same size

TRUE — ALL OR NONE

Where is the action potential initiated?

Axon Hillock (start of the axon — where axon leaves the soma)

When does an action potential occur?

Depolarization

Spatial & Temporal summation of EPSP

Spatial — happen at the same time
Temporal — happen frequently

Phases of action potential

EPSP → threshold reached → Na+ channels open → Na+ influx into cell → depolarization → Na+ channels inactivated → K+ channels open → K+ efflux out of cell → hyperpolarization (K+ channels are slow) → resting membrane potential

T/F: Na+/K+ pump is still working throughout this

TRUE

Refractory Period

period when neuron cannot fire an action potential

Absolute Refractory Period

voltage-gated Na+ channels inactivated after opening

Relative Refractory Period

action potential threshold harder to reach during undershoot

Action Potential Threshold

-50 mV

What are the two benefits of myelin?

- increase in speed of conduction
- decrease ability of ions to leak out

Saltatory Conduction

regeneration of action potentials along the axon — myelinated regions & nodes of Ranvier — allows fast diffusion

Nodes of Ranvier function

have Na+ channels — regenerate action potentials so they don’t weaken

Why can’t action potentials go in reverse?

the region behind is in the refractory period

Which ion is important for neurotransmitter release?

Ca++ → calcium channels open when action potential reaches presynaptic terminal

What is Neural Representation?

pattern of neural activity from an internal/external stimulus

Rate Coding

firing rate of one neuron

Population Coding

firing of many neurons

Temporal Coding

precise timing of firing of neuron

What does Optogenetic Stimulation involve?

control brain activity with light:
- insert light-sensitive proteins (inhibitory/excitatory)
- channels respond to light with high spatial/temporal fidelity
→ external control of behavior/mood!

T/F: Single Unit (neuron) recording is of high spatial and temporal resolution

TRUE

Prosthetics

pattern of activity in the patient’s motor cortex is used to control a robotic arm

EEG

electroencephalography
→ measures neuronal activity on the surface of the scalp

MEG

magnetoencephalography
→ measures magnetic fields generated by brain activity

ECOG

electrocorticography
→ electrodes placed directly on the brain (used in brain surgery)

T/F: EEG and MEG have good temporal & bad spatial resolution

TRUE

T/F: iEEG and ECOG have good temporal & spatial resolution, but require surgery

TRUE

TMS

transcranial magnetic stimulation
→ magnetic stimulation to scalp to activate/inactivate neurons below the magnet
→ excite or inhibit

Limitations of TMS

superficial/surface-level — difficult to target deep areas
uncomfortable
transient cognitive changes

Deep Brain Stimulation

electrical stimulation of brain (requires surgery)
neurostimulator implanted under the skin, sends electrical impulses to the brain

T/F: Brain stimulation is used when medication doesn’t work for Parkinson’s, Depression, OCD, etc.

TRUE

MRI

brain structure/anatomy using magnetic fields through water molecules in brain

fMRI

brain function to measure oxygen content of the blood in the brain using magnetic properties of atoms

Resting-state fMRI

study of brain connectivity while person is not performing a specific task

PET

Positron Emission Tomography
measure brain activity by radioactive molecule (glucose) — neurotransmitter receptor activation; 3D scan of brain