neuroscience exam 1 flashcards

soma

nucleus & machinery involved in the life process of the cell. **Contains genetic info, maintains neuron’s structure, provides energy**

dendrites

**brings information into the cell** - info transmitted across synapses. Extend away from the cell

axon

tube-like structure that **propagates integrated signal to specialized endings**

axon: axon hillock

 **integrates signals from multiple synapses and if these signals exceed the firing threshold, an action potential occurs.** Initial segment

axon: myelin

fatty substance that **provides insulation for electrical messages** carried along the axon. Acts as an insulator to **minimize dissipation** of electrical signal as it travels down the axon. Also s**peeds up the transmission of neural impulses**

action potential

electrical and chemical events, exactly the **same size and duration always**. It is the **basic message the axon carries**. The intensity of the effect is based on the frequency at which action fires action potential. Rapid depolarization followed by hyperpolarization

synapses (definition + 4 pts)

**places of connection between 2 cells/ 2 neurons/ a cell + a neuron**

* Presynaptic unit: messages are sent form the terminal buttons here
* Terminal Button: When reached by action potential, terminal buttons secrete neurotransmitter which excites / inhibits receiving cell & determines whether action potential occurs in the receiving cells axons
* Synaptic cleft: space between pre and postsynaptic cells where info is released
* Postsynaptic unit:  where messages are received by the postsynaptic cell

unipolar/pseudounipolar

dendrite + axon emerge from a single branch coming out of soma. *Pseudounipolar cells are exclusive to sensory neurons*, have no dendrites & have 2 axon branches that extend from PNS to CNS

bipolar

1 axon & 1 dendrite on opposite sides of soma. Axon can branch out @ end

multipolar (golgi i and ii)

* more than 2 dendrites. Most common neuron


* Golgi I: neurons with long- projecting arena processes (to body from spiral cord)
* Golgi II: neurons with axonal processes that project locally (in brain from area to area)

plasma membrane

double layer of lipid molecules that defines boundary of neuron.

* receptors, channels and transport proteins

plasma membrane: receptors

move information & create changes based on that info. Ligand are neurotransmitters that attach to receptors & allows ions to flow in which changes the membrane potential of neuron and sends an action potential down the neuron

plasma membrane: channels

specific for the transported substance, move ions inside the membrane. When open, they allow ion movement. Specific channels for + or - ions

plasma membrane: transport proteins

proteins involved in facilitated transport. Function as either channels for the materials or carriers and use energy to transport molecules in/ out of the cell

chromosomes

contain recipes for making proteins. Can't leave nucleus

dna

Deoxyribonucleic Acid. Molecular code for genes.

transcription process

**genes contain recipes for individual proteins**. Initiate protein synthesis & produce **mRNA (copies info stored by gene, leaves nucleus with copied info and attaches to ribosomes in soma).**

nucleolus

produces ribosomes which are made out of proteins & take mRNAs make it into a protein

ribosomes

molecules that synthesize polypeptides (folded by golgi apparatus into protein) and proteins

translation process

***Info from DNA is transcribed into mRNA→ takes to ribosome→ ribosome translates and synthesizes proteins.*** **The end product is a protein. Translation occurs in the cytoplasm at the ribosome**

codon

help code for proteins, form unit for genetic code of DNA/RNA

anticodon

forms a unit of genetic code in tRNA corresponding to a codon in mRNA

cytoplasm

semi liquid substance that fills space surrounded by membrane. Contains organelles ( small specialized structures / "little organs")

mitochondria

provide cells with energy. ATP (adenosine triphosphate) is used through the cell as an energy source

endoplasmic reticulum (2)

* parallel layers or membrane found within the cytoplasm of a cell.
* Rough ER: *has ribosomes* it is involved with *production of proteins* secreted by the cell
* Smooth ER: the site of synthesis of lipids and provides channels for segregation of molecules involved in various cellular processes. Makes lipids and breaks down toxins. No ribosomes on the outside

golgi apparatus

proteins are brought here from rough ER. Takes info produced in ER and ships it to different parts of the cell

golgi apparatus: exocytosis

secretion of a substance by cells through vesicles. Neurotransmitters are secreted like this

golgi apparatus: lysosomes

organelle surrounded by membrane. Contains enzymes that break down waste products (*digestive materials*, if infected, lysosomes combine w/  virus creating a phagosome which breaks virus down, *dissolve non-functioning mitochondria*, produced by ribosome, can kill cells)

cytoskeleton

**formed of microtubules and other protein fibers linked to each other & forming a cohesive mass that** ***gives a cell its shape***. ***Separates chromosomes*** **during cell division,** ***cell signaling pathways, allows organelles to migrate***

microtubule (tubulin)

long strand of bundles of  protein filaments arranged around a hollow core. Part of cytoskeleton, *involved in transporting substances within a cell, provides support + tracks for transport*. 10% of  total brain protein. **Polymers of a- and b- tubulin dimers which polymerize end to end in protofilaments→ protofilaments bundle parallel to one another into hollow cylindrical filaments of 25m in diameter.**

microtubule: maps

Microtubule associated proteins. Have high molecular weight and regulate the dynamic turnover of microtubules. Some stabilize to promote polymerization and some inhibit depolymerization

microtubule: tau proteins

proteins that stabilize microtubules

microfilament (actin)

 B- and y- actin. Most abundant in presynaptic terminals, spine and growth cones (edge of terminals)

* Microfilament-associated proteins: work together with other proteins. Change connections and pull away when there’s movement. ***Tracks for movements of mitosis molecules, muscle contraction, cytokinesis, intracellular transport, cell division***

intermediate filaments

form an **elaborate network in the cytoplasm of most cells**, extending from a ring surrounding the nucleus to the plasma membrane

intermediate filaments: neurofilaments

unique to neurons. Fine thread-like structures that form a matrix in the cytoplasm and **provide support for the cell membrane & maintain shape of neuron**

kinesins

motor protein associated with microtubules. ***Kinesin walks cargo/molecules down microtubule to be released at a certain point to the synapse. Moves toward the positive end (aka synaptic terminal)***

kinesin: kinesin-1

* Kinesin-1: moves ***from soma to terminal (forward/ anterograde***). 80 mm length.

Heterotetramer

**2 heavy chains→ head & shaft, legs of molecule, ATP + microtubule binding domains, C -terminus involved in interactions to cargo. 2 light chains→ tail, interaction to cargo & sit on particular vesicles**

dyenins

***move from terminal to soma (backwards/ retrograde)*** 40 nm length, 2 heavy chains, multiple intermediate and light chains. *Fast retrograde transport and slow axonal transport.* **Retrograde transport is needed for recycling, feedback (so that synapses don’t get cut off) and to keep connections alive**

dyenins: slow axonal transport

* *Slow axonal transport: slow so as to not use too much energy. Things not needed asap*
* *Slow component a:* ***moves cytoskeletal (heavy) proteins***. Neurofilaments, microtubules, move as assembled polymers, degrade rapidly when reaching terminals. 0.1-1 mm/day
* *Slow component b: moves heterogeneous (small cytoskeletal polypeptides and soluble enzymes) 2-4 mm/day.* ***rate limiting process for nerve growth.***

myosins

molecular motor. Converts chemical energy (ATP) to mechanical energy. Involved in neural growth and development

fast axonal transport

* *mainly for functional things needed at higher rates. Membrane bound organelles*
* *Anterograde transport:* ***fastest mode, kinesin- 1, mitochondria, membrane-associated receptors and synaptic vesicles*** *(neurotransmitters and neuropeptides). Movement down the axon away from soma*
* *Retrograde transport:* ***½  speed of anterograde***, Biochemically and morphologically distinct (larger). Vesicles carried by ***dynein. Returning cargo and exogenous material→ materials that originated elsewhere*** *(neurotrophins that encourage connections te keep it alive and viral particles)*

neurotrophic growth factors

family of peptides/small proteins that attract/repel axon growth, help prevent cell death, and promote axonal branching

microglia

part of the immune system that becomes active when there is a disease on the brain. Act as phagocytes, eating damaged cells and bacteria

macroglia (+3 types)

large goal cells→ oligodendrocytes and astrocytes (CNS), Schwann cells (PNS)

macroglia: oligodendrocytes

**wrap around neurons, isolate patch on axon so info is transmitted fast,** ***support and produce myelin sheath.*** **In the CNS**

schwann cells

***axons myelinated in segments*** **-> 1 segment= 1 schwann cell wrapped many times around the axon.** ***Digest dead and dying axons, arrange in cylinders that act as guides for regrowth.*** **In the PNS**

astrocytes (8)

***provide support, structure + insulation, removes debris from dead cells in CNS***→ engulf & digest (__phagocytosis__), if there is a lot of debris, they divide, and some fill vacant areas while other create scar tissue, ***promote efficient signaling*** **(make chemicals that neurons need for functioning and reuptake of neurotransmitters),** ***controls chemical composition of fluid surrounding neurons***, sometimes *regulate properties of presynaptic terminal, guide migrating neurons during development and axonal growth, releases growth factors and* __*nourishes neurons*__→ put leg on glucose, chew glucose, make lactate, feed neuron, go into kreb cycle, take ATP and feed to neuron. **They cannot fire or generate an action potentia**l

blood-brain area (+area postrema)

Semipermeable barrier between the blood and the brain produced by cells in the walls of the brain's capillaries. **Larger or water soluble molecules can’t get in, while lipid soluble molecules that are positively charged and have a low molecular weight can**. Astrocytes help make the leg between the barrier to make sure nothing gets in . **Regulation is important for extracellular fluid because if composition changes the transmission of messages is disrupted**

* **Area postrema region al the medulla where the blood brain barrier is weaker and poisons can be detected there and initiate vomiting**

describe what the action potential entails

Originates at the Axon Hillock if signals exceed the firing threshold. Travels down the Axon and eventually reaches the terminal button, which secrete neurotransmitters that either excite/inhibit receiving cells. These neurotransmitters (aka ligand) attach to receiving cell’s receptors and allows ions to flow in, which then change the membrane potential of a neuron and sends action potential down the neuron

*What molecules are able to pass through the membrane?* ***If a molecule cannot pass through the membrane on its own, how does it enter/exit the cell (describe the general process)?***

Small nonpolar molecules and small uncharged polar molecules can pass through the membrane because they are soluble in the lipid bilayer. Large molecules, polar molecules and ions. If a molecule can’t pass through the membrane on its own, it passes with __active transport,__ assisted by enzymes and requiring energy. In ***endocytosis*** cells take in substances by engulfing them in a vesicle derived from the cell membrane. In ***exocytosis*** cells shift materials from inside the cell to the extracellular space by engulfing them in vesicles

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*What are molecular motors used for and what part of the neuron depends on them?*

Molecular motors are used to move cargo/molecules. Axons, dendrites and synapses all depend on them. They are found in the cytoplasm

List characteristics that are unique to neurons.

dendrites, axon, myelin, action potential, synapse, neurofilaments

sensory neuron

unipolar or pseudounipolar. Detect stimuli when dendrites are stimulated. Carry incoming info from the sensory receptors to the brain and spinal cord. Dorsal root ganglion (has cell bodies of sensory neurons) and muscle spindle (sensory receptor located in a muscle that senses its tension)

muscle neuron

neurons that carry info from the brain through the spinal cord to muscles

electrode

conductive medium used to apply electrical stimulation/ record electrical potential

microelectrode

**Fine electrode generally used to record activity of individual neurons. Used in humans**

membrane potential

electrical charge across a cell membrane. The difference in electrical potential is between the inside and outside of the cell

oscilloscope

lab instrument capable of displaying a graph of voltage as a function of time on the face of a cathode ray tube. ***Records changes in membrane potential between 2 points over times***

electrostimulator

primarily a brain-calming technique, which delivers small pulses of electrical current through the brain

force of diffusion

process where molecules distribute themselves evenly throughout the medium in which they're dissolved. Movement of particles towards lower concentration from higher concentration and vice versa. **Potassium out and Chloride and Sodium in.**

electrostatic pressure

force exerted by attraction/ repulsion of cations or anions. **Potassium and Sodium in and Chloride out.**

charges/composition of the outside and inside of a cell

**Outside the cell is + changed much like saltwater (high Cl and Na). Inside is - charged (high A- organs anions-which can’t leave- and K)**. Cl and K are close to equilibrium between forces, Sodium always wants to come in

depolarization

reduction towards zero of membrane potential of a cell from its normal resting potential. Inside at axon is more + than resting potential/ relative to the outside

hyperpolarization

increase in membrane potential of a cell relative to normal resting potential. Inside of the axon is more - relative to outside. *A hyperpolarized cell is less likely to send electrical message*

cable properties

*passive conduction* of electrical current in a decremental fashion down the length of an axon. **Dendrites use it as the main process to move info across axons. Good for small distances because it is fast, efficient & doesn't lose energy.**

threshold of excitation

value of membrane potential that must be reached to produce an action potential. Set point depolarization must reach to trigger action potential.

Ion channel

a specialized protein molecule (ligand) that permits specitie ions to enter or leave the cell.

action potential graph

voltage dependent

**ion channel that opens/closes according to the voltage of the membrane.** ***Sodium channel is time dependent, while Potassium channel is only voltage dependent***

reflactory period

period after an action potential where sodium channels can’t open again because they need a reactivation period

sodium-potassium pump

protein found in the membrane of all cells that extrudes Na ions from and transports K into the cell. 3 Na out for every 2 K in. ***After many action potentials, Na eventually accumulates inside the cell. Without pumps this would lead to no action potentials***

all or none law

**principle that once an action potential is triggered it is propagated without decrement to the end of the fiber.**

saltatory conduction

conduction of action potentials by myelinated axons. **Action potential decrementally gets retriggered at Nodes of Ranvier and the electrical message is conducted along myelinated area to the next node. Very fast and less energy is needed to keep Na balance because only a little Na enters @ the nodes**

rate law

**principle that variations in intensity of a stimulus/ other info being transmitted in the axon are represented by variations in the rate at which an axon fires.** Population is the number of neurons that are firing. ***Rate depends on type of neuron*** (different neurons detect different thresholds, so  type of neuron that gets activity tells us about intensity) ***& action potential frequency***

population code

a method to represent stimuli by using the joint activities of a number of neurons

synaptic vesicles (vamp+syntaxin)

* in the presynaptic membrane, a small, hollow bead-like structure found in terminal buttons that **contains neurotransmitters and releases them into postsynaptic membranes where they are met by proteins to ok signals**. Bind together and allow membranes to come close and merge
* VAMP: vesicle associated membrane proteins. **Align vesicles with release sites on the inner neuronal cell membrane and participate in triggering the release of transmitter**
* Syntaxin: integral membrane protein in the plasma membrane that **binds synaptobrevin and synaptotagmin in a calcium dependent fashion during exocytosis**

release zone

**region on interior of presynaptic membrane to which synaptic vesicles attach and release their neurotransmitters into synaptic cleft. Action potential opens calcium channels which allows calcium ions to enter and bind with proteins embedded in the membrane of synaptic vesicles @ the release sone. Fusion pores open, neurotransmitters are released into the synaptic cleft.**

kiss and leave

**vesicle docks but doesn’t fully fuse into membrane**

kiss and stay

**vesicles stay docked with neurotransmitters still inside**

merge and recycle

**most common. Membranes of vesicles merge with the presynaptic membrane. Little buds of membrane pinch off into cytoplasm and become synaptic vesicles. Appropriate proteins are inserted into membrane of vesicles and vesicles are filled with molecules of neurotransmitters**

inotropic receptor/ ligand gated ion channel

receptor that contains a binding site for neurotransmitters and an **ion channel that opens when a molecule of the neurotransmitter attaches to its binding site. Ligand-gated ion channels can be excitatory or inhibitory and are fastest to polarize/ depolarize.** ***Direct***

metabotropic receptor/ 7 transmembrane g protein linked channel

receptor that contains a binding site for a neurotransmitter. **Activates an enzyme that begins a series of chemical events that opens an ion channel elsewhere in the membrane of the cell when a molecule of the neurotransmitter attaches to the binding site**

metabotropic receptor: g-protein

**protein coupled to metabotropic receptor, conveys messages to other molecules when a ligand binds with and activates the receptor**. Made up of 3 subunits, Alpha, Beta and Gamma. **When there's activity, Alpha subunit sparates**

types of g-proteins (3)

* Gs: stimulatory - ***alpha protein breaks away and excites an enzyme (amylase cyclase, AMP) that makes 2nd messenger (cAMP) which attaches to channels and activates*** 1. molecule binds with receptor 2. G protein is activated 3. The alpha subunit breaks away and activates enzyme which produces second messenger 4. Ions channels open 5. Ions enter cell and produce postsynaptic potential
* Gq: ***excites by releasing calcium which activates Phospholipase C (PLC,) which increases cAMP levels***
* *GI: Inhibitory - I****nhibits enzyme (AMP) & reduces release of cAMP which closes channels***

second messenger

chemical **produced when a G protein activates an enzyme**. Carries a signal that results in the opening of the ion channel/causes other events  to occur in the cell

cyclic amp (cAMP)

second-messenger system **present in the cytoplasm of a variety of cells**. When activated, its **production can ultimately induce gene transcription in the cell nucleus and thus affect the density of membrane receptors at synapse**

Excitatory postsynaptic potential/ (EPSP)

excitatory depolarization of postsynaptic membrane of synapse caused by liberation of neurotransmitter by terminal buttons. ***Sodium channels open = depolarization in postsynaptic area***. Calcium is also involved.

Inhibitory postsynaptic potential (IPSP)

inhibitory hyperpolarization of postsynaptic membrane of a synapse caused by the liberation of a neurotransmitter by terminal buttons. ***Potassium flows out of the cell = hyperpolarization in the postsynaptic area***. Chloride also involved

autoreceptors

a receptor that regulates, via positive or negative feedback processes, the synthesis and/or release of its own ligands. **Regulate the firing patterns of dopamine neurons and control the timing and amount of dopamine released from their terminals in target regions**

neural integration

process by which **inhibitory and excitatory potentials summate  and control the rate of firing of a neuron**

Presynaptic inhibition

action of a presynaptic terminal button in an axoaxonic synapse; **reduces amount of neurotransmitters released by postsynaptic terminal button**

Presynaptic facilitation

action of a presynaptic terminal button in an axoaxonic synapse, **increases the amount of neurotransmitters released by postsynaptic terminal buttons.**

Diffusion

neurotransmitter naturally diffuses after its release and then decays. **Slow, uncontrollable**

Internalization

removal of neurotransmitters from synaptic cleft by terminal button. Receptors go in and out the cell based on need. Can be done by the presynaptic or postsynaptic membrane. Agonists generally cause receptor internalization. **Internalization doesn’t change the total number of receptors, it just changes how many of them are currently in the synaptic cleft**

Re-uptake

**special transporter in presynaptic unit vacuums neurotransmitters back in. Costs energy but is more efficient because it can be reused**. Glial cells can help.

Enzymatic degradation

**Kills neurotransmitters to stop signals by enzymes that destroy molecules of neurotransmitters. Fastest way to stop a signal but not the most efficient because neurotransmitters cannot be used again.** Glial cells can help

What is the importance of the spinal reflex (what does it tell us about how neurons work together to excite or inhibit?)

Spinal reflexes contribute to normal muscle tone and mediate a number of simple motor responses (e.g. withdrawal from a painful stimulus). The spinal cord also contains more complex neural networks. The spinal cord transmits nerve impulses to and from the brain.

Can basic reflexes be overridden?

Yes. Through feedback inhibition (another, inhibitory neuron stops an action)

List other places axons may connect apart from dendrites

Dendritic spine, somatic membrane, postsynaptic terminal button