psychopharmacology chapter 2

quiz 1

neurotransmission

the process by which neurons communicate

1. anatomical: focuses on neurons and their connections (synapses)

2. chemically: focuses on neurotransmitters and their chemical signaling

3. electrical: focuses on action potentials (action potentials)

neuron

cells of chemical communication in the brain

location in the brain determines its function

malfunction leads to behavior malfunction

main parts of a neuron

1. cell body

2. axon

3. dendrites

4. synapse

5. terminal button

6. myelin sheath

cell body

houses the nucleus and other organelles

responsible for cell maintenance and function

axon

long extension from the cell body

transmits electrical impulses to the next neuron

transmission speeds up with the myelin sheath

dendrites

smaller extensions from the cell body

receives information from other neurons

each neuron can have multiple dendrites

synapse

the junction between one neuron’s axon and the next neuron

contains the synaptic cleft, which is a small gap neurotransmitter must cross

terminal button

located at the end of an axon

stores neurotransmitters in vesicles and releases them into the synaptic cleft

myelin sheath

protective insulation around the axon

makes electrical impulses travel faster

myelination starts before birth and continues until adolescence

synaptic connections in neurotransmission

can form in places other than between axons and dendrites

axosomatic synaptic connection: cell body

axoaxonic axon: axon (affects how the next impulse is transmitted)

communication is asymmetric: signal flows from presynaptic neuron to the postsynaptic neuron

chemical basis of neurotransmission

compliments the anatomical system

focuses on how chemical signals are coded, decoded, and transmitted

1. knowing how psychopharmacological agents work

2. becoming a neurobiologically informed clinician

3. improving diagnosis and treatment of psychiatric disorders

neurotransmitters in chemical neurotransmission

• serotonin

• norepinephrine

• dopamine

• acetylcholine

• glutamate

• GABA

serotonin

regulates mood, sleep appetite

norepinephrine

alertness, stress response

dopamine

motivation, rewards, movements

acetylcholine

learning, memory, muscle activation

glutamate

main excitatory neurotransmitter

GABA

main inhibitory neurotransmitter

God’s pharmacopeia

neurotransmitters that are so similar to drugs

drugs mimic natural neurotransmitters (binding to same receptors and producing same effects)

input to any neuron can involve multiple neurotransmitters, which is why multiple drugs can be used together for treatment

classic neurotransmission

neurons use electrical impulses, communication between them at the synapse is chemical

sequence of classic neurotransmission

1. electrical impulse travels down the first neuron

2. at the synapse, it is converted into a chemical signal

3. that chemical signal affects the receiving neuron

electrical phase of action potential (phase l)

resting potential:

• neuron is negatively charged inside

• potential -40 to -80 MV (avg -70 mV)

• maintained by ion gradients (sodium and potassium)

action potential:

• voltage-depended ion channels open when stimulated

• sodium flows in and the cells become positively charged (depolarization)

• membrane potential rises to +40 mV

refractory period:

• potassium flows out, cell returns to -70 mV

• neuron cannot fire again until reset

excitation-secretion coupling

process by which a neuron converts an electrical action potential into a chemical event (releasing neurotransmitters)

neurotransmission constantly switches between electrical and chemical signals to send information

how excitation-secretion coupling works

1. action potential reaches the presynaptic axon terminal

2. voltage-sensitive sodium and calcium channels open

3. calcium entry triggers neurotransmitter release from vesicles

4. neurotransmitters cross the synaptic cleft, then bind to receptors on the next neuron

membrane potential

difference in charge inside vs outside the neuron

nodes of ranvier

gaps in the myelin sheath that help the action potential jump (saltatory conduction)

all-or-none principle

neuron either fires completely or not at all

resting potential

-70 mV (charge before firing)

ions

sodium (Na*) potassium (K*) chloride (CI*)

refractory period

reset time after firing, when the neuron cannot fire another action potential

chemical neurotransmission

what happens at the synapse

presynaptic

1. action potential arrives at terminal buttons

2. neurotransmitters stored in the vesicles are released into the synaptic cleft

postsynaptic

1. graded potential occurs, causes small changes in membrane potential

2. neurotransmitters bind to receptors on the dendrites of the next neuron

3. cell body integrates the signal, which decides if the next action potential fires

4. signal can be excitatory or inhibitory

retrograde neurotransmission

postsynaptic neuron sends signals back to the presynaptic neuron (bil3aks)

process of retrograde neurotransmission

1. postsynaptic neuron synthesizes and releases neurotransmitters

2. these diffuse backward across the synapse

3. they regulate the presynaptic neuron’s future neurotransmitter release (feedback)

it provides a feedback mechanism to enhance signaling

helps maintain balance in neurotranmission

volume neurotransmission

neurotransmission via diffusion, not limited to the synaptic cleft

explains how some brain chemicals have broad, mood, or arousal related effects rather than specific, targeted ones

also called non-synaptic diffusion neurotransmission

example: dopamine in the prefrontal cortex, spreads and influences many neurons at once

process of volume neurotransmission

• chemical message spills over and can reach distant receptors before it is destroyed

• allows for wider communication beyond a single postsynaptic neuron

• signal persists until the neurotransmitter is broken down or reabsorbed

signal transduction

communication inside neurons

transmission is not just neuron-to-neuron

communication is also from the genome of the presynaptic neuron to the genome of the postsynaptic neuron

how signal transduction works

• triggered by chemical neurotransmission

• involves long chains of chemical messengers (signal transduction cascades)

• final goal is to alter gene expression

• influences long-term changes like synaptogenesis or protein synthesis

DNA

• core genetic material

• found in the nucleus of cells

• made of long chains organized into chromosomes

chromosomes

• structures made of DNA and proteins

• comes in pairs (X and Y)

genome

• your entire set of genes (DNA and RNA)

• referred as genotype

genes

• segments of DNA that code for specific proteins

• controls for protein synthesis, cell function, and life processes

proteins

• made of amino acids

• acts as enzymes, hormones, and structural molecules in the body

signal transduction cascades type 1

activates cellular activity by turning proteins on

1. neurotransmitter actives production of a second messenger

2. second messenger activates a third messenger (kinase)

3. kinase adds phosphate groups to proteins, produces phosphoproteins (protein phosphorylation)

4. important for regulating cell activity, structure, and function

signal transduction cascades type 2

turns off or regulates protein activity, maintains balance

1. neurotransmitter opens ion channels, calcium enters the neuron

2. calcium is the second messenger

3. calcium activates the third messenger (phosphatase)

4. phosphatase removes phosphate groups from proteins, reversing phosphorylation in type 1

5. balance between kinase and phosphatase activity determines whether the fourth messenger is triggered

leads to gene expression and synaptogenesis

four main signal transduction systems

1. G-protein-linked systems

2. ion-channel-linked systems

3. hormone-linked systems

4. neurotrophin-linked systems

key points of the transduction systems

• modifies gene expression

• brain creates long-term changes (learning, memory, adaptation to medication)

• same gene-expression mechanisms underly psychiatric disorders and drug actions

epigenetics

the process that determines whether a gene is turned on or silences

the expression profile

explains why the same drug or disorder can affect two people differently

highlights importance of environment and biology in mental health

key points of epigenetics

• brain function depends on genes you inherit and whether they are expressed at the right time

• abnormal gene expression causes psychiatric or neurological problems

• neurotransmission, drugs, and environmental factors can impact epigenetic processes