Neuroscience Exam 1

What is so remarkable about prehistoric skulls?

They show evidence of skull surgeries over 7000 years ago, which occurred while the individual was living and they show evidence that the person survived.

What is the process of prehistoric skull surgery called?

trepanation

Why was there so much emphasis on the heart over the brain?

location (center of body vs top), heart appears more impressive since it physically beats and provides blood, and the network of blood vessels allow communication with the rest of the body

Who was Hippocrates, and what did he believe regarding the brain?

“father of western medicine”; believed in ethical doctor-patient relationships (Hippocratic oath); believed brain was source of sensation and intelligence

What did Aristotle say the brain did?

secondary organ designed to cool the heart

Who was Galen?

physician to gladiators, follower of Hippocrates, “finger poke” test of neurophysiology, founder of experimental physiology

What did Galen believe regarding the brain?

brain held soul, was responsible for sensation, intelligence

What was the Fluids Hypothesis and how did it supposedly work?

says that the brain receives sensation and moves limbs through neuronal transduction, which is done by the movement of fluids; neurons are long, thin, hollow tubes that run throughout the body; brain has fluid filled cavities

What is dualism and who is responsible for this idea? What brain structure was believed to be especially important?

Descartes believed the mind and body are separate and the mind interacts with the body through the pineal gland

What ultimately replaced the fluids hypothesis and who was responsible for this discovery? Who inspired him?

bioelectricity, Luigi Galvani was inspired by Ben Franklin and found that frog legs twitched when attached to wires as if stimulated by electricity

What is phrenology and is it supported by science today?

bumps and shapes on skull are responsible for personality, character, and intellect; not supported by modern science

What is localization and how did work by Gall and Broca influence it?

theory that certain parts of the brain have specific functions; Broca’s “Patient Tan” could understand language but not speak, had a lesion on left frontal lobe

What was the debate between Golgi and Cajal about and who won?

Reticular theory: nervous tissue forms continuous network (like blood circulatory system)

Neuron theory: neurons are discrete, independent cells

Winner: Neuron theory

What does a molecular neuroscientist study?

the roles of molecules in the brain

What does a cellular neuroscientist study?

how nerve cells operate and how they transmit information

What does a systems neuroscientist study?

how the visual system represents surroundings, how motor system keeps us in balance, moves eyes, makes us walk

What does a behavioral neuroscientist study?

what makes us alert/sleepy, effects of drugs on behavior

What does a cognitive neuroscientist study?

What happens in brain when we remember something, what brain does to create consciousness

What are the two main types of brain cells?

neurons (communicate) and glia (support/nourish neurons)

What are the pros and cons of the Nissl stain?

Pros: stains nuclei & Nissl bodies (rough ER) & allows visualization of arrangement of neurons

Cons: only shows cell bodies, not axons/dendrites

What are the pros & cons of Golgi stain?

Pros: more complete visual of neuron

Cons: only stains small % of neurons

What is the reticular theory and who supported it?

nerve cells form continuous network, supported by Golgi

What is the neuron theory and who supported it?

supported by Cajal, nerve cells are discrete, independent cells (“winner”)

What are the major parts of a neuron/what makes neurons unique?

soma & neurites (axons and dendrites)

What are axons?

send nerve impulses away from soma

What are dendrites?

receive synaptic inputs from other cells

What are the common glial cells we discussed and what are their functions?

astrocytes, oligodendrocytes, microglia, ependymal cells, schwann cells

What is a synapse?

where neurons come in contact with one another

what is the difference between a bipolar cell and a multipolar cell

bipolar have one axon and one dendrite (common in eyes and nose); multipolar have one axon and multiple dendrites (primary motor & interneurons in CNS)

What is the relationship between Alzheimer’s disease and microtubules?

the essential neuronal transport network of microtubules collapses due to the malfunction of tau protein, which normally stabilizes these structures

What disease is linked to the breakdown of myelin?

multiple sclerosis - myelin damage leads to nerve signals slowing or stopping

What ingredients go into the membrane?

salty fluids: inside & outside of the cell (water & ions)

lipids: make up the plasma membrane

proteins: span the membrane (ion channels & pumps)

Is there more K+ inside or outside of the cell?

inside

Is there more Na+ inside or outside of the cell?

outside

How are concentration gradients maintained?

protein pumps

What are the 2 forces that act on an ion and how do they work?

diffusion: ion movement from high → low concentrations

electrical force: charge differences across membranes (opposites attract, likes repel)

What is the term for the membrane potential at which the 2 forces are in equilibrium?

equilibrium potential (Nernst potential)

What is current?

current: flow of electrons in a circuit (measured in amperes (A))

What is conductance?

(opposite = resistance) ease with which charged neurons cross membrane through ion channels

What is voltage?

difference in charge across membrane

How do current, conductance, and voltage relate to the movement of ions at the membrane?

they determine how ion channels open, close, and change membrane potential

What is the resting membrane potential for a typical healthy neuron?

-65mV

What is the Nernst equation?

equilibrium potential for a single ion

Eion = (58/2) log([ion]out/[ion]in)

What is the Goldman equation?

equilibrium potential for more than one ion

V = 58 log((Pk[K+]out + PNa[Na+]out + PCl[Cl-]) in /( Pk[K+]out + PNa[Na+]out + PCl[Cl-]) out

What is the difference between Nernst equation and Goldman equation?

Nernst is for one ion, Goldman for multiple

What ion is the membrane most permeable to at rest? How do we know?

K+, high number of leak channels

What is the relationship between the driving force and Eion?

driving force for an ion increases the farther away from Eion

What is meant by the “all-or-none” property of an action potential?

if a neuron's stimulus reaches a specific threshold, the action potential fires at full amplitude, but if it fails to hit that threshold, no action potential occurs at all

How is the strength of an action potential “coded”?

frequency of action potential

What does it mean to hyperpolarize?

membrane potential becomes more negative

What does it mean to depolarize?

membrane potential becomes more positive

What are the phases of an action potential? Movement of which ion is responsible for each phase?

Rising phase (depolarization): membrane potential becomes positive; influx of Na+ via voltage-gated Nav channels

Falling phase (repolarization): membrane potential returns to resting level; K+ leaving cell via voltage-gated Kv channels

What is the absolute refractory period?

once an action potential in initiated, it is impossible to trigger another one for one ms

How does the action potential move down the axon? What factors influence how quickly it moves down the axon?

one direction, speed depends on diameter of axon & presence of myelin

What are the characteristics of Nav channels?

open downward, open quickly after stimulus, stay open for short amount of time, opening initiates rising phse

What are the characteristics of Kv channels?

open upward, more delayed opening, stay open longer, opening initiates falling phase

What are the different open/close/inactivated states of Nav?

closed state: activation gate closed, inactivated gate open

open state: both gates open

inactivated state: activation gate open, inactivation gate closed

What are nodes of Ranvier? What purpose do they serve?

gaps in the myelin sheath packed with ion channels; they regenerate action potentials and allow nerve signals to jump between gaps, increasing speed

What is tetrodotoxin, and how is it toxic?

toxin found in pufferfish, interferes with signal transmission from nerves to muscles, eventually affecting ability to control muscles and breathe

How was it discovered that neurons could communicate via chemicals?

Otto Loewi’s experiment: stimulating frog’s vagus nerve released a substance that slowed second heart

What are the two major types of synapses and their features?

electrical: direct channels between neurons via gap junctions, can pass both directions, allow for synchronicity, rare

chemical: use neurotransmitters to bridge the space, common

Where/when do electrical synapses tend to be most common?

where rapid, synchronized activity is required, like cardiac & smooth muscle, certain brain regions (prevalent early in development, less so as you age)

What are the steps involved in synaptic transmission?

1. action potential arrives

2. Ca2+ influx

3. neurotransmitter release

4. binding to receptors

5. postsynaptic potential

6. transmitters removed

What are the major neurotransmitters?

Peptides, Amines, Amino acids

How are the small, classical neurotransmitters synthesized/transported to the axon terminal? how does this differ from the larger neuropeptides?

eznymes convert precursors into neurotransmitters, transporters load neurotransmitter into vesicles; peptides are synthesized in soma and transported down axon

How do vesicles bind to the membrane? What role does Ca2+ play?

Ca2+ acts as trigger, binding to sensors upon influx, forcing fusion pore to open & release cargo

What are ligand-gated ion channels and how do they work?

(ionotropic receptors); activated by ligands, a neurotransmitter

Once a neurotransmitter binds to a receptor, what happens to the postsynaptic neuron? (What is an EPSP & IPSP)

Excitatory Post-Synaptic Potential: ligand channel opens → positively charged ions enter (Na+,Ca2+); depolarizes postsynaptic membrane so it is closer to AP threshold

Inhibitory Post-Synaptic Potential: ligand channel opens → negatively charged ions enter (Cl-); hyperpolarizes postsynaptic membrane so that it is farther away from AP threshold

What is the primary excitatory NT? what channel does it open?

glutamate opens positively charged ion channels

what is the primary inhibitory NT? what channel does it open?

GABA opens Cl- channels

How is excess neurotransmitter removed from the synapse?

diffusion, reuptake, enzymatic breakdown

What is the difference between ligand-gated channels & G-protein coupled receptors (GPCRs)?

Ligand-gated channels open directly upon ligand binding, allowing fast flow; GPCRs use G-proteins to trigger slower, intracellular cascades

What are the major types of neurotransmitters?

Acetylcholine (ACh)

Catecholamines: Dopamine (DA), norepinephrine (NE), epinephrine

Serotonin (5-HT)

What are the functions of ACh?

sleep, movement, learning, memory

What are the functions of dopamine?

motor movement, motivation, reward, reinforcement

What are the functions of norepinephrine and epinephrine?

norepinephrine: (noradrenaline) sleep/wakefulness, arousal, attention, feeding

epinephrine (adrenaline): regulates cardiovascular & respiratory functions

What precursor do all catecholamines start from?

tyrosine

What are the functions of serotonin?

aggression, mood disorders, anxiety, food intake, sexual behaviors, sleep/wakefulness

What was the first neurotransmitter discovered?

Acetylcholine

How do organophosphates such as sarin gas elicit their effects?

preventing neurotransmitters from being broken down, causing buildup at the synapse, leading to receptors becoming desensitized to that neurotransmitter

Dopamine, norepinephrine, & epinephrine all use tyrosine as their precursor, so what determines which neurotransmitter is the end product?

the enzyme

What are transporters?

specialized proteins that move neurotransmitters across membranes,

What is an agonist?

substance that binds to a specific receptor in the brain, mimicking a nt and producing a biological response

What is an antagonist?

substance that reduces or blocks the effects of a nt by binding to its receptors without activating them

What serve as the primary agonists to nicotinic acetylcholine receptors (nAChRs)?

ACh and nicotine

What is excitotoxicity?

when too much of a “good” thing is a “bad” thing; e.g. excess glutamate can be harmful by leading to prolonged EPSPs

How do NMDA receptors differ from AMPA receptors?

AMPA: faster kinetics, permeable to Na+ & K+, needs glutamate

NMDA: slower kinetics, permeable to Ca2+ (& Na+ & K+), needs glutamate & membrane depolarization

Why is taking alcohol & benzodiazepines a potentially lethal combination?

both enhance GABA inhibition, depressing CNS & suppressing respiration and consciousness

What is an ionotropic receptor & how does it differ from a metabotropic receptor?

ionotropic: fast, direct changes in membrane potential by opening ligand-gated ion channels

metabotropic: slower, longer-lasting effects through G-protein-mediated signaling pathways

What are other names for ionotropic and metabotropic receptors?

ionotropic: ligand-gated ion channels

metabotropic: G-protein-coupled receptors

When are ionotropic and metabotropic receptors important?

ionotropic: when immediate response needed

metabotropic: when long-term changes or copmlex modulation is required

What are examples of unconventional nts?

nitric oxide, endocannabinoids

what makes unconventional nts unconventional?

not stored in vesicles, not released from presynaptic terminal, retrograde signaling

What is the function of astrocytes?

regulate chemical content in space around neurons

What is the function of oligodendrocytes?

insulate axons to improve efficiency of signal transfer

What is the function of microglia?

immune cells that scavenge debris & pathogens in brain

What is the function of ependymal cells?

line ventricles of brain and produce cerebrospinal fluid

What is the function of Schwann cells?

produce myelin for peripheral nerves

What direction is dorsal?

towards the back

What direction is anterior?

Towards the head