Week Three - Neurotransmission & Introduction to Psychopharmacology Flashcards
What do Nerve cells generate?
Electrical signals in order to transmit information
Neurons generate what?
A negative potential called the resting membrane potential
What does an action potential do?
It abolishes the negative resting potential and makes the transmembrane potential positive
What are neurons separated by?
Extracellular fluid which is composed mainly of water
What is the cell membrane made up of?
lipid molecules
What does the cell membrane do?
Regulates the concentration of salts and other chemicals on either side
What are the 3 factors that influence the movements of ions in and out of the cells?
- Concentration Gradient
- Voltage Gradient
- Structure of the membrane
Describe the Concentration Gradient
Describes the relative difference in the concentration of a substance at different locations in space when the substance is not evenly dispersed
Define the Voltage Gradient
A measure of relative concentrations of electrical charge. Ions will move down a voltage gradient from an area of high charge to an area of low charge
What occurs during equilibrium?
One side will be positively charged, while the other will be negatively charged.
What are SALTS?
Molecules that separate into two parts when dissolved in water, with one part carrying a positive charge and the other part carrying a negative charge. These charged particles are collectively called IONS
What 4 ions charge contributes to the negative charge on the inside of the cell membrane?
sodium, chloride, potassium and large protein anions
How do ions flow across the cell membrane?
- Ligand-gated channels
- Mechanically-gated channels
- Voltage-gated channels
- Leakage channels
- The Na+ /K+ Pump
What are ion transporters and ion channels responsible for?
Ionic movements across neuronal membranes
Explain Ligand-gated Channels
Basically a lock and key. Neurotransmitter binds to the channel and opens it, allowing the ions to move in response to gradient
What are mechanically-gated channels?
They open when there is a force that activates.
What direction does sodium and potassium move?
Sodium = in Potassium = out
What are voltage-gated channels?
When there is a change in voltage, it opens an allows ions through
What are leakage channels
Leakage channels randomly open and allows a certain amount of leakage across the concentration gradient
Explain the Sodium & Potassium pump
The process of moving sodium and potassium across the cell membrane
it will pump 3 Na ions outside of the cell for every 2 potassium ions pumped inside of the cell
The equilibrium potential can be predicted by what formula?
The Nernst equation
What is the equilibrium potential?
The voltage at which the ions no longer want to move across the membrane
What does the Nernst equation help do?
Calculate equilibrium potential of one ion
What can the Goldman equation do?
Calculate equilibrium potential of multiple ions
What are postsynaptic potentials?
Graded potentials in the dendrites of a neuron that receives synapses from other cells
Excitatory Postsynaptic Potential (EPSP)?
These are depolarisations and increase the likelihood of a neuron firing.
it causes the membrane potential to move toward threshold.
Inhibitory postsynaptic potential (IPSP)?
These are hyperpolarisation and decrease the likeliness of a neuron firing.
it causes the membrane potential to move away from threshold.
How are EPSP and IPSP transmitted?
decrementally from the site of input, becoming smaller as it stretches across the membrane
Where do changes in voltage that produce an action potential come from?
A large influx of Sodium ions and a efflux of potassium ions
What is an action potential?
a brief (about 1 ms) change from negative to positive in the trans-membrane potential.
AP is said to be all-or-none because?
it occurs fully or not at all.
What is the movement of an AP along an axon called?
A nerve impulse
What is the resting membrane potential of a cell?
-70mV
The mode of conduction is called what?
Saltatory conduction
Why is the nerve impulse produced?
Because each AP propagates another AP on an adjacent part of the axon membrane.
Where are the neurotransmitters stored before the AP?
In vesicles within the terminal buttons
What are neuromodulators?
Like neurotransmitters but do not meet all criteria
What are the properties of a neurotransmitter?
be synthesized and stored in the presynaptic neuron.
be released into the synapse when the neuron fires
cause a post-synaptic effect after it interacts with a receptor
there must be some mechanism for degradation or reuptake
How are neurotransmitters synthesised?
from precursors under the influence of synthesising enzymes
Released NT molecules bind to what?
postsynaptic receptors
What are the 2 major types of postsynaptic receptors?
Ionotropic and metabotropic
What are second messengers?
intracellular signalling molecules released by the cell in response to exposure to extracellular signalling molecules (i.e., the first messengers)
What do agonistic drugs do?
Increases synthesis of NT
Increases no. of NT molecules
Increases release of NT
Binds to autoreceptors and blocks their inhibitory effect
Binds to postsynaptic receptors and either activates or increases effect
What do antagonistic
Blocks, inhibits and reduces the role and function of NT
What do amino acid transmitters do?
Provide both the majority of excitatory and inhibitory NT in the NS
What is the major excitatory NT?
Glutamate
What is the major inhibitory NT?
GABA
Where does GABA uptake occur?
In neurons and glial cells
Define all concepts of Acetylcholine (ACh)
what does it do
what affects it
The first neurotransmitter ever discovered
controlling heart rate, acetylcholine plays an important role in motor movement, as it is the neurotransmitter released from motor neurons onto muscle fibres to make them contract. Role in memory - Alzheimer’s disease involves a degeneration of acetylcholine neurons in the basal forebrain – drugs that increase ACh availability are used for treatment.
Toxins such as botulism, nerve gas, and black widow spider venom interfere with acetylcholine transmission and produce paralysis.
What are Norepinephrine, Epinephrine, Dopamine, Serotonin known as?
Catecholamines
Define all concepts of Norepinephrine
what does it do
what affects it
Norepinephrine is distributed throughout the central and peripheral nervous systems.
The noradrenergic neurons originate in the pons of the brainstem in a region called the locus coeruleus.
They form an excitatory pathway to the cortex known as the reticular activating system (RAS).
This system is primarily responsible for maintaining cortical arousal.
Structures that are innervated by NE include the thalamus, the hypothalamus, and virtually all other limbic structures.
NE is involved in controlling attention, emotion, and eating.
Noradrenergic neurons also play important roles in the peripheral nervous system regulating organs such as the heart.
Deficiencies in norepinephrine activity are linked to depression and to attention deficit disorders.
What 2 pathways is dopamine located?
The nigrostriatal pathway begins in the brainstem area called the substantia nigra. The primary function of these structures involves voluntary movement. Deficiencies in dopamine in the nigrostriatal pathway result in Parkinson’s disease.
The second major dopamine pathway originates in the ventral tegmental area (VTA), with a major involvement in reward and motivation. The mesolimbic system innervates the nucleus accumbens, the septum, the amygdala, and the hippocampus. Other axons from the VTA, the mesocortical system, form the third pathway and project to the frontal cortex.
Define the concepts of Serotonin?
Is distributed throughout the brain and spinal cord and is involved in the control of the sleep/wake cycle, mood, impulsive behaviour, and appetite.
Serotonin neurons originate in the brain stem in a region of cell bodies called the dorsal raphe nucleus and the median raphe nucleus. Axons from these cells travel throughout the cortex and other important areas.
has been implicated in numerous behavioural problems including sleep disorders, aggression, obesity, anorexia, and depression.
