Biological Psychology - Section 1

what part of the neuron is its cell body/soma and contains the nucleus?

parikaryon

what are the cellular fibers emerging from the cell body?

neurites

what neurite are tree-like extensions off the cell body that RECEIVE signals from other neurons?

dendrites

what neurites are long slender projections off of the cell body that SENDS signals toward other neurons?

axons

axons are surrounded by what to protect and insulate it?

myelin sheath

what is the role of the axon?

it carries an electrical signal to other neurons called an action potential

what are the bulbous endings at the end of the axon?

pre-synaptic terminals

what do pre-synaptic terminals contain?

synaptic vesicles filled with neurochemicals called neurotransmitters

what are neurons?

electrically excitable cells that convey electrical signals between each other using neurochemical messengers

what must happen for neural signaling to occur?

neurons must communicate with each other

what do you call the space between the pre-synaptic terminals of one neuron and the dendrites of another neuron?

a synapse

what is the “pre-synaptic” neuron?

the neuron that sends the electrical signal through its pre-synaptic terminals

what is the “post-synaptic” neuron?

the neuron that receives the electrical signal through its dendrites

what specifically gets released into the synapse by the pre-synaptic neuron?

neurotransmitters

what are small chemical molecules released from neurons?

neurotransmitters

what do neurotransmitters do after being released across the synaptic space?

they bind to neurotransmitter receptors

what are neurotransmitter receptors?

ligand-gated ion channels embedded into the membrane of post-synaptic cells that bind neurotransmitters released into the synapse, forming the communicating link between neurons

what happens when neurotransmitters bind to the neurotransmitter receptors?

they open a channel, allowing electrically charged ions (ex. Na+, K+) to enter or exit the neuron, changing the electrical charge inside the post-synaptic neuron

what are neurotransmitter receptors also called?

ion pores

however, not ALL neurotransmitters bind to neurotransmitter receptors - some are…

recaptured by the pre-synaptic neuron’s neurotransmitter re-uptake pumps

what are neurotransmitter re-uptake pumps?

special proteins embedded in the membrane of the pre-synaptic terminals that bind and transport the neurotransmitter back into the pre-synaptic terminal for breakdown or re-packaging into synaptic vesicles for reuse

how are neurons characterized?

by how many neurites they have originating from the soma/cell body

what is a unipolar neuron (also called pseudo-unipolar)?

a neuron with only one neurite originating from the soma

what is a bipolar neruon?

a neuron with two neurites originating from its soma

what is a multipolar neuron?

a neuron with many neurites originating from its soma

what is the law of dynamic polarization?

explains neuronal function by saying neurons are polarized so they send signals in one direction, with some exceptions

what are axo-dendritic synapses?

a synapse where info flows from the pre-synaptic terminal to the dendrite

what are axo-somatic synapses?

a synapse where info flows from the pre-synaptic terminals to the cell body

what are axo-axonal synapses?

synapses where info flows from the pre-synaptic terminal to the axon

what are axo-synaptic synapses?

synapses where info flows from the pre-synaptic terminal to another pre-synaptic terminal

with all those different ways for information to flow, the law was revised to what?

focus on pre-synaptic vs. post-synaptic function

what is the revised law of dynamic polarization?

says that information flows from the pre-synaptic cell to the post-synaptic cell WITH RESPECT TO A SPECIFIC SYNAPSE

what are sensory neurons?

neurons that bring information from the body into the CNS

what are motor neurons?

neurons that transmit information out of the CNS to the muscles

what are interneurons?

neurons that lie between sensory and motor neurons (can be pre- or post-synaptic depending on the synapse in question)

what separates the inside of the cell (intracellular) from the outside of the cell (extracellular)?

the neuronal membrane

how much of the body is made up of water?

2/3

what does it mean when water is described as “polar"?”

water has two oppositely charged ends - slightly positive on H and slightly negative on O

what types of molecules have an electrical charge?

polar molecules

what contains long chains of carbon and hydrogen, and are nonpolar (having no charge)?

organic molecules (ex. grease, oil, fats/lipids)

what are nonpolar molecules?

molecules that have no electrical charge, so they cannot interact with polar molecules

are nonpolar molecules soluble in water?

no

what can nonpolar molecules acquire?

a charged phosphate group - a phosphate head (-) can attach to a lipid hydrocarbon tail (no charge), producing a phospholipid

charged polar heads of phospholipids can interact with water, meaning they are:

hydrophilic

uncharged nonpolar tails of phospholipids are unable to interact with water, meaning they are:

hydrophobic

phospholipids are amphipathic, meaning they:

have both a hydrophobic and hydrophilic region

uncharged nonpolar tails can’t interact with each other, so when put into water, phospholipids:

form a lipid bilayer, a major component of cell membranes

how is a synaptic vesicle structured?

neurotransmitters are stored inside the vesicle, which is made up of a lipid bilayer of phospholipids

the neuronal membrane is a “fluid mosaic” structure, which means what?

the hydrophobic interior of the lipid bilayer acts as a very effective barrier to electrically charged particles like water and salt trying to get in and out of the cell, so it has different proteins (channels and pumps) that “float” on it to perform these functions

what’s the process of turning DNA into proteins?

genes in DNA are transcribed in mRNA, which are then translated into proteins

what is DNA (deoxyribonucleic acid)?

a genetic sequence comprised of four chemical bases (cytosine, guanine, adenine, thymine) assembled in a specific order with a double-stranded helical structure,

what are genes?

regions of the DNA that encode for proteins

what is mRNA (messenger ribonucleic acid)?

a single-stranded copy of the DNA molecule that is comprised of four bases (cytosine, guanine, adenine, uracil) in a sequence that “codes” for a protein (or more specifically, for amino acids)

what are proteins?

chains of amino acids

which amino acids can also function as neurotransmitters?

glutamate/aspartate (neuronal excitation), glycine (neuronal inhibition), tyrosine/tryptophan (precursors for classical neurotransmitters)

what is translation?

the assembly of amino acids in a specific sequence encoded for by the mRNA - ribosomes in the cytoplasm “read” the mRNA base sequence and insert amino acids in a particular order

what are neurotransmitters?

chemical molecules released into the synapse from the pre-synaptic terminal of neurons that act as chemical messengers or signals between neurons

what are peptide neurotransmitters?

short proteins (ex. endorphins)

what are proteins bound to the cell membrane of neurons that form pores in the membrane that can open to transport electrically charged ions across the cell membrane, maintaining the electrical charge of neurons?

membrane ion channels/pumps

what type of membrane ion channel is passively open?

always open (leaky)

what type of membrane ion channel opens in response to changes in membrane electrical charge?

voltage-gated

what type of membrane ion channel opens in response to membrane pressure?

mechanically-gated

what type of membrane ion channel opens in response to the binding of a ligand?

ligand-gated

what are molecules that bind to neurotransmitter receptors (ex. neurotransmitters)?

ligands

what type of receptor is itself a channel for charged ions and has a site that binds a ligand to open the ion channel?

ionotropic

what type of receptor is linked to a neighboring ion channel by a signaling protein (called a G protein) that is attached to the inside of the cell membrane?

metabotropic

how to metabotropic receptors work?

these receptors have sites that bind a ligand, activating the G-protein attached to it, which then acts to open an ion channel

are ionotropic or metabotropic receptors faster?

ionotropic

neurotransmitters act by a “continuum of efficacy.” what does this mean?

neurotransmitters bind and activate the receptor, and then are released and reactivation the receptor (on-on, off-off)

what term describes how fast and strong a ligand binds to a receptor?

affinity

what term describes how effective (does the ion channel open?) a ligand is once bound to the receptor?

potency

what types of ligands are molecules that bind to a receptor and activate it (opens ion channels and produces a response)?

agonists

what types of ligands are molecules that bind to a receptor but do not activate it (does not open ion channels, producing no response), blocking the receptor from functioning?

antagonists

does the body produced endogenous antagonists?

no, the body only produces several endogenous AGONISTS (all antagonists are exogenous, such as drugs, poisons, and toxins)

which has a higher affinity for receptors, agonists or antagonists?

antagonists - will win if both are present

what decides excitation vs. inhibition?

the receptor (NOT the neurotransmitter)

what types of ligands are molecules that bind to a receptor at a different location than agonists/antagonists, increasing or decreasing the ability of the receptor to bind a neurotransmitter?

(positive/negative) allosteric modifiers

what are often co-transmitters and released with small chemical neurotransmitters such as dopamine and norepinephrine?

peptide transmitters - acts as neuromodulators (like allosteric modifiers!)

what are neuromodulators?

substances that act by binding to a receptor at a different location than the neurotransmitter itself, increasing the affinity of the receptor to bind the neurotransmitter

which neurotransmitters are the endogenous (naturally-occurring) ligands?

acetylcholine, GABA, glutamate, dopamine, norepinephrine, serotonin

how is acetylcholine synthesized?

in the pre-synaptic terminal by enzyme cholineacetyltransferase (ChAT), which fuses acetate and choline together

how is acetylcholine broken down?

once it’s released from the ACh receptor, it diffuses out of the synapse and is broken down (metabolized) in the synapse by enzyme acetylcholinesterase (AChE)

where does acetylcholine act?

at the neuromuscular junction

what is the neuromuscular junction?

the connection between a motor neuron and a skeletal muscle (aka interface between nerve and muscle)

how does Ach act at the neuromuscular junction?

it acts via a nicotinic ACh receptor (nAChR), causing an excitatory effect that produces a skeletal muscle contraction

what is physostigmine?

a natural drug that blocks AChE (enzyme that breaks down ACh)

what are insecticides?

manmade AChE blockers

if AChE, the enzyme that metabolizes ACh, is blocked, what can happen?

skeletal muscle rigor ad smooth muscle flacidity

what is the effect of GABA?

it produces a widespread neural inhibition (often called the control neurotransmitter) → the most commonly employed neurotransmitter in the brain

where is GABA synthesized?

in the pre-synaptic terminal from the amino acid glutamic acid (glutamate) by enzyme glutamic acid decarboxylase (GAD), which removes a carboxyl group from glutamate to convert into GABA

what does the GABA_A receptor do?

it’s an ionotropic receptor for Cl^- ions, increasing the negative charge in the neuron, producing neuronal inhibition

what binding sites does the GABA_A receptor have?

it has at least two allosteric binding sites, one for benzodiazepines, and another for barbiturates → each binding increases the ability of the receptor to bind GABA

what is the effect of glutamate?

it is an amino acid neurotransmitter that produces neuronal excitation (the opposite of GABA)

what are the glutamate receptors?

AMPA receptor, Kainate receptor, NMDA receptor → ionotropic receptors that function as channels for Na⁺ or Na⁺/Ca²⁺ ions, increasing the positive charge in the neuron, exciting it

what is the AMPA receptor?

the most active glutamate receptor that allows Na⁺ to enter the cell, causing neuron excitation

what does the Kainate receptor do?

cause neuron excitation by allowing Na⁺ to enter the cell

what does the NMDA receptor do?

cause neuron excitation by allowing Na⁺/Ca²⁺ to enter the cell

what are the biogenic amines?

a family of neurotransmitters that include the catecholamines (dopamine and norepinephrine) and an indolamine (serotonin)

how are the catecholamines (DA and NE) synthesized?

in the pre-synaptic terminal from amino acid tyrosine by tyrosine hydroxylase (TYR → DOPA) and aromatic amino acid decarboxylase (AADC, DOPA → DA); DA is converted into NE by dopamine beta-hydroxylase (DBH)

how is the indolamine serotonin synthesized?

in the pre-synaptic terminal from amino acid L-Tryptophan by tryptophan hydroxylase (TRPH, TRP → 5-HTP) and AADC (5-HTP → serotonin)