Psych 230 Exam 1

exam 1 review flashcards

What is behavioral neuroscience?

The scientific study of the biological bases of psychological processes and behavior

Independent Variable

The factor being manipulated

Dependent Variable

What is measured in response to change in the independent variable

Three Main Approaches to Study Neuroscience of Behavior: Somatic Intervention

Alteration of a structure or function within the brain, see how behavior is altered (change the brain, check behavior)

Ex;

Administer a hormone → Strength of mating behavior

Stimulate brain region electrically → Movement toward goal object (motivation)

Cut connections between parts of nervous system → Recognition of stimulus

Three Main Approaches to Study Neuroscience of Behavior: Behavioral Intervention

Intervention in a behavior, see how structure or function is altered (change behavior (or experience), check the brain); behavior is then the independent variable, and changes in brain are dependent variables

Ex;

Put male in presence of female → Changes in Hormone Levels

Present a Visual Stimulus → Changes in electrical activity of brain

Give training (how to navigate a maze) → Anatomical changes in nerve cells

Correlation

Examines how much a body measure varies with a behavioral measure

• If one measure goes up and the other goes down, there is a negative correlation

• If both measures increase or decrease together, there is a positive correlation

CORRELATION DOES NOT EQUAL CAUSATION

Three Main Approaches to Study Neuroscience of Behavior: Correlation

No intervention or manipulation of anything. Instead, you simply measure a biological variable and a behavioral variable simultaneously to see how closely they covary (move together)

• Brain size ←correlation→ Learning Scores

• Hormone levels ←correlation→ Strength of mating behavior

• Enlarged cerebral ventricles ←correlation→ Schizophrenic symptomes

Control Group

Identical to the experimental group except they don’t experience any alteration or treatment

Within-Subjects Experiment

The control group is the same set of subjects tested before or after alteration of treatment.

Benefits:

• Control for individual variability

• Can use less subjects

Between-Subjects Experiment

The experimental group is compared to a separate control group that has been treated identically except for the manipulation.

Benefits:

• May be used if treatment is irreversible

• Comparing different groups (alzheimers vs. no alzheimers)

Experiment vs. Non Experimental Research

Experimental: Manipulate the independent variable and then observe changes in behavior to establish cause and effect

• Groups assigned at random

• Treatment (experimental) group compared to control

Non-Experimental: No manipulation of variables; observe and describe

• Cause and effect cannot be established

• Ex; correlational studies, surveys/polls, case studies, longitudinal research, historical/archival, naturalistic observation

Neuroplasticity/ Neural Plasticity

Describes the ability of the brain to be changed by environment and by experience. (Configuration of synapses on dendrites and cell body is constantly changing; Dendritic spines, which increase surface area for synapses, can be rapidly altered, facilitating the continual remodeling of neural connections)

• Occurs during development as well as in adulthood

• Extremely fast, dendritic spines on neurons can change shape in seconds

• Ex; In rats, social isolation can result in brain changes

  • scientists reared male rats in a cage by themselves, or with buddies, then, they examines their brains for differences

• In humans, psychological expectation can affect the magnitude of a response

  • a brain region involved with processing emotion (including pain) in humans, the cingulate cortec, is affected by the expectation of stimulus intensity (subjects led to believe that hot water was very hot)

Neuron Doctrine

States that the brain is composed of independent cells that are distinct structurally, metabolically, and fucntionally; Information is transmitted from cell to cell across synapses

Input Zone

The dendrites and cell body (soma) recieve information via synapses from other neurons

Integration Zone

The axon hillock at the base of the cell body combines (integrates) the information the neuron has received to determine if it will send a signal of its own

Conduction Zone

The axon carries (conducts) the neuron’s own electrical signal away from the cell body to the axon terminals

Output Zone

Axon terminals transmit the neuron’s signals across synapses to other cells

Axons Vs. Dendrites

Axons:

• usually one per neuron, with many terminal branches

• uniform until start of terminal branching

• axon hillock present

• usually covered with myelin

• ranging from practically nonexistent to several meters long

Dendrites

• usually many per neuron

• tapering progressively toward ending

• no hillock-like region

• no myelin sheath

• often much shorter than axons

Neurons can be classified by their functions (3 types)

Motor neurons: stimulate muscles or glands

Sensory neurons: respond to environmental stimuli, such as light, odor, or touch

Interneurons: receive input from and send input to other neurons

Glial Cells

Support and assist neurons; they can communicate with each other and with neurons

• Provide neurons with raw materials

• Alter neural structure and excitability

• There are almost as many glial cells as neurons in brain, and they come in 4 types

Astrocytes

1 type of glial cell:

Star shaped cells with many processes

• Receive neuronal input and monitor neural activity

• Regulate blood flow

• Involved in formation of new synapses and pruning of old ones

Microglia

1 type of glial cell:

Small but super active (and cool!) cells

• Housekeeping: engulf and remove debris from injured or dying cells

• Immune function: they are the primary immune cells in the brain, producing and releasing cytokines in response to sickness

Oligodendrocytes

Provide myelination in the central nervous system (brain & spinal cord)

• all along axons, these glial cells wrap sections of the axon in this fatty insulating substance to increase the speed of transmission of the signal

Schwann Cells

Provide myelination in the peripheral nervous system (everything else)

• all along axons, these glial cells wrap sections of the axon in this fatty insulating substance to increase the speed of transmission of the signal

Nodes of Ranvier

Gaps between sections of myelin where the axon is exposed, and voltage-gated ion channels are located

Gross Neuroanatomy

Features of the central and peripheral nervous system structure visible to the naked eye

Central Nervous System

Consists of the brain and spinal cord; Dominated by two cerebral hemispheres

Peripheral Nervous System

All parts of the nervous system found outside the skull and spinal column

Motor Nerves

Part of the peripheral nervous system, which consists of nerves, or bundles of axons, that carry info into and out of the central nervous system:

Transmit information from the central nervous system to the muscles, organs, and glands (call these efferent projections)

Sensory Nerves

Part of the peripheral nervous system, which consists of nerves, or bundles of axons, that carry info into and out of the central nervous system:

Convey information from the body to the central nervous system (these are afferent projections)

Somatic Nervous System

Part of the peripheral nervous system; nerves that interconnect the brain and the major muscles and sensory systems; includes cranial and spinal nerves

Cranial Nerves

Part of the Somatic Nervous System

12 pairs that serve the sensory and motor systems of the head and neck)

Spinal Nerves/ Somatic Nerves

Part of the Somatic Nervous System

Each spinal nerve is the fusion of two distinct branches or roots:

• Dorsal (back) root → carries sensory information from the body to the spinal cord

• Ventral (front) root → carries motor information from the spinal cord to the muscles

Spinal nerves are named for the segment of spinal cord they are connected to: Cervical (neck), Thoracic (trunk), Lumbar (lower back), Sacral (pelvic), Coccygeal (bottom)

Autonomic Nervous System

Nerves that primarily control the visceral organs (digestive organs, heart, etc.); Has 3 major divisions: Sympathetic nervous system, Parasympathetic nervous system, Enteric nervous system

Sympathetic Nervous System

Prepares the body for action; Drives fight-or-flight response

Parasympathetic Nervous System

Returns body to homeostasis; Drives the rest-and-digest process

Enteric Nervous System

Regulates the functioning of the gut; maintains fluid and nutrient balances

Sympathetic neurons and Parasympathetic neurons use different transmitters

Sympathetic Neurons: produce norepinephrine (or noradrenaline) to accelerate activity

Parasympathetic Neurons: produce acetylcholine

Cerebral Cortex

The thick, outermost layer of the cerebral hemispheres, comprised mostly of neuronal cell bodies, dendrites, and axons; here neurons are organized into cortical columns

• Each column is perpendicular to the cortical layers and serves as a unit to process information

  • The 6 different layers are unique and differentiated based on types of neurons & their functions

• Cortical regions communicate with one another via tracts of axons

Gyrus

Gyri; Raised surface of the brain

Sulcus

Sulci; Furrowed parts of the brain

Gray Matter vs. White Matter

Gray matter: Cell bodies

White matter: Axon tracts

4 Lobes of the Brain

Frontal Lobe: Manages voluntary movement, executive decisions, planning, and emotional control

• Positioned right behind the forehead at the front of the brain

Parietal Lobe: Integrates sensory inputs like touch, temperature, pressure, and pain

• Located behind the frontal lobe and above the temporal lobe

Temporal Lobe: Processes sounds, language comprehension, and long-term memory storage

• Situated on the lower sides of the brain near your ears

Occipital Lobe: Controls visual perception, including the recognition of shapes, colors, and movements

• Positioned at the very back of the brain, right above the brainstem

Bilateral Symmetry

-The brain, with the exception of a few structures, is bilaterally symmetrical

-In general, each side of the brain controls and receives information from the opposite (contralateral) side

Cerebellum

Elaborately convoluted; involved in motor learning and coordination; consists of 3 layers:

• Purkinje Cell Layer: the middle layer; its large cells form a single row

• Granule Cell Layer: composed of small neurons whose axons form the third, innermost layer

• Parallel Fibers: make up the outermost layer (also called molecular layer)

Meninges

The three protective membranes that surround t he brain and spinal cord

• Dura Mater → tough outermost sheet

• Pia Mater → delicate innermost layer

• Arachnoid → substance between the dura mater and pia mater that cushions the brain in cerebrospinal fluid (CSF)

Ventricular System

A series of chambers filled with Cerebrospinal Fluid

Functions of Cerebrospinal Fluid

1.) Acts as a shock absorber

2.) Provides an exchange medium between blood and brain to provide both fluid and nutrients to the brain

Lateral Ventricles

Fluid-filled cavities located inside the brain’s cerebra; hemispheres that produce and circulate cerebrospinal fluid (CSF), one cavity sits in the left hemisphere, and the other in the right hemisphere; lined with choroid plexus

Choroid Plexus

A membrane that produces cerebrospinal fluid

Glymphatic System

A specialized lymphatic system that drains waste from the brain through cerebrospinal fluid

Vascular System

Provides the brain with the oxygen it needs

• The blood-brain barrier is the result of higher resistance in brain capillaries that restricts passage of large molecules

  • Astrocytes are the glial cells that contribute to the blood-brain barrier

Hemorrhagic Stroke vs. Ischemic Stroke

Hemorrhagic Stroke: occurs when a rupture in an artery allows blood to leak into the brain

Ischemic Stroke: clots or other debris prevent blood from reaching a region of the brain, causing it to die

Neural Transmission

The electrochemical process by which a neuron passes an electrical and chemical message down its length and across a tiny gap (synapse) to communicate with neighboring cells

Synapse

A specialized junction or tiny gap where a neuron passes an electrical or chemical message to another cell

Has three principal components:

• Presynaptic membrane of the axon terminal of the presynaptic (transmitting) neuron

• Synaptic cleft, a tiny gap that separates the presynaptic and postsynaptic neurons

• Postsynaptic membrane on the dendrite or cell body of the postsynaptic (receiving) neuron

General Process of what Occurs in Synapse

• Synaptic vesicles in presynaptic axon terminals contain a chemical neurotransmitter

• Neurotransmitters are released in response to electrical activity in the axon

• Receptors in the postsynaptic membrane are specialized proteins that react when a neurotransmitter molecule binds to them

How do Neurons Communicate?

• The neuronal cell body and dendrites receive information across synapses from other neurons

• Dendrites have a branched arborization pattern to facilitate contacts

• Information is processed in the axon hillock

• Information is then transmitted down the axon and from the presynaptic neuron to the postsynaptic neuron

Axonal Transport

The movement of materials within an axon via motor proteins.

• Anterograde: sending supplies to terminals

• Retrograde: bringing messages back to the cell body

Neurophysiology

The study of electrical and chemical processes in neurons.

• Information flows within a neuron using electrical signals (ions), and information flows between neurons using chemical signals (neurotransmitters)

Membrane Potential

Difference in electrical charge between the inside and the outside of a cell’s membrane, created by an unequal distribution of ions.

All living cells have an electrical charge, they are more negative on the inside than the outside

• This means a cell is polarized

A neuron at rest has a membrane potential of -50 to -85mV (typically use -65 as resting membrane potential)

• Negative sign indicates that a neuron’s inside is more negative than the outside because they are more negatively charged particles (anions) inside the cell than outside

Ions are dissolved in fluid

• Fluid inside cell is intracellular fluid, which is separated from extracellular fluid by the phospholipid bilayer cell membrane

Maintaining the Membrane Potential

• A number of things work together to help keep the membrane potential around -65mV such as selectively-permeable ion channels, electrostatic force, diffusion, sodium-potassium pumps

• At rest the extracellular fluid contains high concentrations of Na+ and Cl-, and the intracellular fluid contains high concentrations of K+ and negatively charged proteins/anions

Selectively-Permeable Ion Channels

• ion channels are proteins that span the membrane and allow certain ions to pass

• some ion channels open and close in response to something, like changes in voltage, chemicals, or mechanical action

• some channels are open all the time and allow certain ions to move into and out of the cell (ex; potassium ions, K+)

  • this is called selective permeability, when only certain ions are allowed to cross the membrane while restricting others

Diffusion

The natural tendency of particles of particles to move down their concentration gradient from an area of high concentration to low concentration

• K+ is highly concentrated inside the cell, so diffusion continuously pushes K+ out of the cell through its leak channels

• Na+ is highly concentrated outside the cell, so diffusion wants to push Na+ into the cell (though it’s mostly blocked by closed gates)

Electrostatic Force

Electrostatic pressure operates on the rule that opposite charges attract and like charges repel

• The positive K+ ions leave the cell via diffusion, they leave behind large, negatively charged proteins that cannot escape, this makes the inside of the cell highly negative, this negative interior creates an electrostatic pull that tries to pull positive K+ ions back into the cell

• Eventually, the outward push of diffusion matches the inward pull of electrostatic force for potassium, this balance point is reached right around the negative resting potential

Sodium-Potassium Pump

• Pumps 3 sodium (Na+) ions out for every 2 potassium (K+) ions pumped in

  • this causes a build-up of K+ inside the cell

• K+ reaches equilibrium when the movement of K+ out of the cell is balanced by the K+ movement into the cell (its equilibrium potential)

  • thus at the equilibrium potential, the opposing forces of diffusion pushing K+ out and electrostatic pressure pushing K+ in are EQUAL, hence, net ion movement is zero

    • this corresponds to the resting membrane potential of about -65 mV

• The sodium-potassium pump helps keep all of this in balance

Action Potential

A brief but large change in membrane potential that originate in the axon hillock and travels along the axon of a neuron to the terminals

• All called “firing”

Hyperpolarization

Making the membrane potential of a neuron more negative by increasing the negative charge on the inside

• So, if the resting potential of the neuron is usually -65mV, this takes it further away from zero, so to maybe -70mV

Depolarization

Making the membrane potential of a neuron less negative on the inside

• So, if the resting potential of the neuron is usually -65mV, this brings it closer to zero, like up to -55mV

Local Potential

Spreads passively from the point of stimulation; the response diminishes the further you get from the source

• The response is also graded: the stronger the stimulus, the stronger the response

Action Potential

When enough excitatory stimulation is applied, the threshold of activation (-40mV) is reached and an action potential (AP) occurs

• The AP is not graded; it’s all-or-nothing; it doesn’t vary in size: it fires fully or not at all

• Also it doesn’t diminish (it is full strength all the way down the axon because the signal gets regenerated)

Applying a stronger stimulus does what to the action potential?

It does NOT change the shape of the action potential, it just produces more of them

What events explain the action potential?

Once the threshold for activation (-40mV) is triggered, an action potential begins:

• Voltage-gated Na+ channels open and Na+ ions rush into the cell (driven by both diffusion and electrostatic pressure)

  • This inward movement of Na+ drives the AP upward

  • The voltage-gated Na+ channels automatically close after about a millisecond

• Voltage-gated K+ channels are also triggered to open with the threshold, but they are really slow and don’t fully open until the peak/downward swing of the action potential

  • K+ moves out (because of diffusion and electrostatic force) and the potential comes back down

  • Because K+ channels also close slowly, a lot of K+ ions leave, causing an undershoot (afterpotential)

• Then, the membrane potential returns to resting

• This happens all the way down the axon, as adjacent sections further down the axon are triggered to open by the Na+ coming in the cell

Afterpotential

The brief period of electrical instability that occurs immediately after a neuron fires an action potential, where the membrane potential dips below its normal resting level. (Also known as the undershoot or hyperpolarization phase)

Refractory Period

Time when only some stimuli can produce an action potential.

Absolute refractory phrase: Time when no new action potentials can be produced

Relative refractory phase: Time when only strong stimulation can produce an action potential

How is the action potential propagated along the axon?

• The action potential begins at the axon hillock

• The action potential is a spike of depolarizing electrical activity, so it strongly depolarizes the next adjacent axon segment

• Because the next segment similarly has voltage-gated Na+ channels, the depolarization there causes them to open and produce thus another electrical spike

  • This occurs at the Nodes of Ranvier, all the way down the axon

  • Note that the axon segment it leaves behind is in the refractory phase

Saltatory Conduction

The action potential travels inside the axon and appears to jump from node to node, as the myelin insulation prevents ions from flowing across the membrane

Multiple Sclerosis

A disorder that occurs when body’s immune system produces antibodies that attack myelin, disrupting the conduction of action potentials (saltatory conduction)

• Wide variety of symptoms that affect sensory and/or motor systems, depending on which axons are attacked

What is the point of a neuron generating an action potential?

To transmit information to other cells; does this through release of neurotransmitters from the presynaptic cell into the synapse.

Steps for Transmission at the Synapse

1.) The action potential travels down the axon to the axon terminals

2.) This opens voltage-gated calcium (Ca²⁺) channels at the terminala dn causes influx of Ca²⁺

3.) The Ca2+ causes vesicles filled with neurotransmitters to fuse with the presynaptic membrane and release their contents into the synaptic cleft → exocytosis

4.) The neurotransmitters cross the synaptic cleft and bind to special receptors on the postsynaptic cell, where they cause small changes in the membrane potential of the postsynaptic cell by allowing ions into that cell

5.) The neurotransmitters then diffuse away, are broken down by enzymes, or are taken back up into the presynaptic cell by transports (reuptake)

SNAREs and Synaptotagmin Mediated Exocytosis

SNARE (Soluble NSF Attachment Protein Receptor) proteins act like biological twist-ties, their primary job is to overcome the natural electrostatic repulsion between the negative lipids of the vesicle membrane and the cell membrane

• v-SNARE (Vesicle associated):

  • Synaptobrevin: A single protein helix embedded directly into the membrane of the neurotransmitter vesicle

• t-SNARESs (Target membrane-associated):

  • Syntaxin-1: A protein anchor embedded in the presynaptic terminal membrane

  • SNAP-25: A peripheral membrane protein that contribute two helical segments to the bundle

As a vesicle approaches the active zone, v-SNARE tightly winds together with t-SNAREs. This process is called zippering, and it pulls the vesicle incredibly close to the presynaptic membrane into a “primed” state, ready for immediate release

Synaptotagmin (The Calcium Sensor) is the trigger, the SNARE proteins pull the vesicles close but they can’t finish the fusion process on their own, they are kept in check until the exact millisecond an electrical signal arrives

• Synaptotagmin is a protein embedded in the vesicle membrane alongside synaptobrevin

• When calcium levels inside the neuron are low, synaptotagmin acts as a brake, preventing the zippered SNARE complex from completing full membran fusion

• Calcium binds directly to synaptotagmin and this binding calcium alters synaptotagmin charge, causing it to aggressively insert itself into the presynaptic plasma membrane and interact with the SNARE complex

  • This interaction releases the molecular brake and the SNARE complex finishes zippering completely, forcing the vesicle and plasma membrane to merge and allowing neurotransmitters to spill into the synaptic cleft

Tetrodotoxin (TTX) & Saxitoxin (STX)

Blocks neural transmission by blocking voltage gated Na+ channels

Batrachotoxin

Blocks neural transmission by forcing Na+ channels to stay open

Botulinum toxin (Botox) & Tetanus toxin

Inhibits neural transmission by cutting up SNARE proteins and stopping exocytosis

Graded

• Neurotransmitters cause graded, local changes in the postsynaptic membrane potential

• The stronger the stimulus, the bigger the response

Local

• Neurotransmitters cause graded, local changes in the postsynaptic membrane potential

• The change in membrane potential spreads passively over the neuron an degrades

Postsynaptic Potentials (PSP’s)

Neurotransmitters released into the synaptic cleft bind to receptors on the postsynaptic cell and briefly alter the membrane potential of the postsynaptic cell by allowing certain ions to enter or exit the cell

• Local (graded) potentials

• A neuron receives synapses from hundred of other cells, so is subject to hundreds or thousands of PSP’s

• When integrated, this massive array of local potentials determines whether the postsynaptic neuron will reach the threshold and generate an action potential of its own

• Two types of postsynaptic potentials are Excitatory Postsynaptic Potential (EPSP) and Inhibitory Postsynaptic Potential (IPSP); both work in the same way, but have opposite effects on the postsynaptic cell

Excitatory Postsynaptic Potentials (EPSPs)

Some neurotransmitters (NTs) cause a depolarization: an electrical change that make the membrane potential less negative (so closer to 0 mV)

• This happens when a certain NT binds and lets positively charged ions into cell

• This makes it more likely that the postsynaptic neuron will fire by bringing the membrane potential closer to the threshold of activation

• A common excitatory NT is glutamate, which lets Na+ ions in the cell

Inhibitory Postsynaptic Potentials (IPSPs)

Some neurotransmitters cause a hyperpolarization: an electrical charge that make the membrane potential more negative (so farther away from 0 mV)

• This happens when a certain NT binds and lets negatively charged ions into the cell, like chloride (Cl-), or lets positively charged ions (K+) leave the cell

• This makes it less likely that the neuron will fire by bringing it further from the threshold of activation

• A common inhibitory NT is called GABA which allows Cl- to enter the cell

Glutamate

A common excitatory neurotransmitter that lets Na+ ions in the cell

• An amino acid

• Receptors: AMPA, kainate, NMDA (all are ionotropic); but there are also some metabotropic glutamate receptors (mGLuR’s)

GABA

A common inhibitory NT that allows Cl- to enter the cell

• GABA receptors are divided into classes (ex; GABA_A, GABA_B)

  • Some are ionotropic, some are metabotropic

  • GABA agonists, like Valium, are potent tranquilizers

Spatial Summation & Temporal Summation Integrate Synaptic Inputs

• One EPSP is not enough to get a neuron to “fire”

• Balance between the number of excitatory and inhibitory signals determines whether an action potential is fires

  • Recall, neurons are always receiving lots of EPSP’s and IPSP’s

• Whether the postsynaptic neuron will fire an action potential is determine by whether a depolarization exceeding the threshold of activation reaches the axon hillock

Spatial Summation: Occurs when multiple distinct synapses located at different physical places on the neuron fire simultaneously

Temporal Summation: Occurs when a single synapse fires repeatedly in rapid-fire succession

Endogenous vs. Exogenous Ligands

Ligands fit receptors exactly and activate or block them

• Endogenous Ligands: Neurotransmitters and Hormones

• Exogenous Ligands: Drugs and Toxins from outside the body

Ionotropic Receptors vs. Metabotropic Receptors

Ionotropic Receptors

• Also known as ligand-gated ion channels

• When a neurotransmitter binds to the receptor, it causes the receptor to change shape and allows ions to enter the cell

• IMPORTANT: the neurotransmitter does NOT enter the cell; only ions do

Metabotropic Receptors

• Comprised of 7 different transmembrane subunits

• When the transmitter binds, it activates G-protein molecules that open a nearby channel OR trigger other biochemical reactions in the cell

• Also called G protein-coupled receptors (GPCR’s)

• They utilize a second messenger system

  • If you think of the transmitter binding to the receptor as the 1st messenger, the next chemical signal (activated by the G protein inside the cell) is the 2nd messenger

  • This second messenger amplifies the effect of the first messenger and can initiate a greater change in the membrane potential, or result in different biological effects

Autoreceptors

• Located on the presynaptic membrane

  • Neurotransmitters bind here to: inform the presynaptic cell about how much NT is in the synapse, can regulate future NT release with exocytosis, and can act as a shut off mechanism

4 Types of Synapses

• Axo-dendritic Synapses

  • Most common synapse type in the central nervous system; typically handle standard, localized processing

  • Usually deliver EPSPs

• Axosomatic Synapses

  • These synapses bypass the long travel distances of the dendrites and the signals delivered here suffer very little decremental fade

  • Predominantly inhibitory IPSPs, allows a single axosomatic input to act as a powerful kill-switch, completely overriding hundreds of excitatory inputs coming from the far-away dendrites

• Axo-axonic Synapses

  • Form near axon terminals, allowing the presynaptic neuron to regulate how much neurotransmitter will be released from that terminal

• Dendro-dendritic

  • Contacts allow coordination of activities, allow groups of neighboring neurons to fire completely in sync

  • often utilize bidirectional electrical synapses (gap junctions) rather than chemicals, allowing ions to flow directly between cells

Retrograde Transmission

Uses gas (like carbon monoxide or nitric oxide) to signal from the dendrite of a postsynaptic cell TO the axon terminal of the presynaptic cell to release more neurotransmitter

Electrical Synapses (Gap Junctions)

The membranes of two different neurons get even closer than a traditional chemical synapse and are separated by large channels called connexons

• These allow ions to flow from one neuron directly into the other with almost no delay

Criteria for Neurotransmitters

1.) Substance exists in presynaptic axon terminals

2.) Synthesized in presynaptic cells

3.) Released when action potentials reach axon terminals

4.) Receptors for the substance exist on postsynaptic membrane

5.) When experimental applied, substance produces changes in postsynaptic cells

6.) Blocking substance release prevents changes in postsynaptic cell

Types of Neurotransmitters: Amino Acid Neurotransmitters

GABA; Glutamate

Types of Neurotransmitters: Amine Neurotransmitters

Acetylcholine; Dopamine; Serotonin