How Neurons Communicate Flashcards
How is information transferred within in the neuron?
Electrically
How is information transferred between neurons?
Chemically
Define Resting Potential
The difference in electrical charge between the inside of the neuron and the outside.
What ions lie outside the the cell? What kind of charge do they have?
Potassium, positively charged.
What ions lie inside the cell? What kind of charge do they have?
Sodium, negatively charged
How do the ions move?
Through the Ion Channel, they move through the cell membrane with the concentration gradient through diffusion to try and reach equilibrium.
What does the sodium-potassium pump do?
It maintains resting potential. This means that the inside of the cell is more negatively charged than the outside, causing an overall electrical charge over the membrane.
What does input from other neurons do to the cell?
It causes an increase in ion concentration and electric charge - making it either more positive or more negative.
At what point does the cell fire?
When the charge is lower than -55mV
Action Potential:
Depolarization – electrical charge reaches peak (-55mV to + 40 mV)– repolarisation – the electrical charge retreats toward baseline resting state – hyperpolarisation – the voltage briefly becomes even more negative than the resting potential - the neuron returns to resting potential
The three properties of action potential:
- The action is self propagating
- The strength does not dissipate over space, it remains consistent.
- It’s an all-or-nothing response, it either fires or it doesn’t.
What is the region of contact between two cells?
Synapse
Explain the steps of contact between two neurons:
The Presynaptic neuron produces action potential in the Axon Hillock - this travels the length of the neuron to the Terminal Bouton (which contains Synaptic Vesticles, filled with neurotransmitters - here it is transferred to a chemical message - the action potential causes the vesticles to burst - the neurotransmitters pour into the Synaptic Cleft - it is transferred to the Postsynaptic neuron - the Dendritic tree of the postsynaptic neuron is configured to receive the neurotransmitters - it changes the chemical transfer back to an electrical one
Excitatory Postsynaptic Potential
It makes the cell’s electrical charge a bit more positive – closer to the threshold at which the cell will fire
Inhibitory Postsynaptic Potential
It makes the inside of the cell a bit more negative than the outside- cell farther away from threshold at which it will fire
What determines the effect that neurotransmitters have?
The receptor type to which it bonds
the 3 characteristics of Postsynaptic Potential
- It’s graded - it’s strength weakens across space
- It’s either excitatory or inhibitory
- It’s small in magniture (in comparison to activation potential_ at 0.5-5mV
5 forms of clearing neurotransmitters from the synaptic cleft
- Reuptake
- Enzyme deactivation
- Glial cell take up
- Diffusion
- Autoreceptors
What is reuptake?
The rapid removal of neurotransmitters back into the terminal bouton by special transporter molecules embedded in the presynaptic membrane.
What is Enzyme Deactivation?
The enzyme separates the neurotransmitter molecules so that they cannot bind to the receptor.
What neurotransmitter is most common in enzyme deactivation? What enzyme is used?
Acetylcholine. Acetylcholinesterase.
What is glial cell up take?
The glial cells take up and destroy neurotransmitters
What is diffusion, in the process of neurotransmitter clearing?
The neurotransmitter floats away, out of range for the receptors.
What do autoreceptors do to clear neurotransmitters?
The autoreceptors are on the presynaptic neuron - they bind to the same neurotransmitters as released by the neuron. When the NT binds to an autoreceptor, it decreases the activity of the presynaptic neuron which prevents the cell from becoming overactive.
2 major classes on neurotransmitters in the CNS
Amino Acids and systematically sorted NTs.
2 Amino Acids and their effects
Glutamate - excitatory
Gamma-aminobutyric acid - inhibitory
4 systemically sorted NT groud in the CNS
- Cholinergic (Acetylcholine)
- Dopaminergic (Dopamine)
- Noradrenergic (Noradrenaline/Norepinephrine)
- Seratonergic (Serotonine)
The difference between Agonists and Antagonists
Agonists - mimic or facilitate the effect of an NT
Antagonist - oppose or diminish the effect of an NT
Origin, projection and effects of the Cholinergic system
Origin: Basal forebrain
Projection site: Diffuse cortical regions
Effects: Overall cortical excitability, attention, memory
3 Subsystems of the Dopaminergic system and it’s effects
- Nigrostriatal (motor activity)
- Mesolimbic (reward related behaviour)
- Mesocortical (working memory, planning)
Effects: working memory, novelty seeking, attention, psychotic symptomatology
Origin, projection and effects of the Noradrenergic system
Origin: Locus coerulus
Projection sites: Hypothalamus, Thalamus and Cortex
Effects: Feeding, sexual behaviour, attention, sleep, working memory
Origin, projection and effects of the Serotonergic system
Origin: Dorsal raphe nucleus and Medial raphe nucleus
Projection sites: DRN - cortex, thalamus. MRN - limbic system
Effects: Sleep, mood, anxiety, sexual behaviour, eating, pain, aggression
What is Myelin?
A fatty sheath around the axon
What effect does a larger myelin sheath have on a neuron?
It makes the electrical signals travel much faster.
What are Nodes of Ranvier and what do they do?
They are gaps between myelin sheaths and they keep the electrical signal constant in size.
What is a Fibretract?
A group of cells sending axons to the same place, generally myelinated.
