PSYC 211 – Lecture 3 January 16 2011
How do Neurons communicate with each other?
Synapse – junction between the terminal buttons of the sending neuron and a portion of the dendritic
neuron of the receiving neuron. Synapse can be on membrane of Soma or on dendrite.
Synaptic Transmission – transmission of messages from one neuron to another through the synapse
through neurotransmitters, which diffuse across the synaptic cleft.
Synaptic vesivles – contain molecules of neurotransmitter. They attatch to the presynaptic membrane
and relase neurotransmitter into the synaptic cleft.
Synaptic Cleft – is the space between the pre and postsynaptic membranes. It is filled with an
Presynaptic membrane – is the membrane of the terminal button (the sending cell). This is where the
neurotransmitter is released. (Calcium channels here)
Postsynaptic membrane: is the membrane of the receiving cell
Neurotransmitters facilitate the opening of channels for ions on the membrane by binding onto the
presynaptic membrane. Movement of ions affect the potential of the postsynaptic membrane.
PostSynaptic Potentials (PSP)
-determined by the type of ion that the receptor opens. Four types of ion channels Na, K, Cl, Ca2+.
Each Ion does a different thing:
-Sodium potassium transporter keeps Na outside the cell. When the channels are open, the influx of
sodium causes a depolarisation. (Excitatory Postsynaptic Potential – EPSP)
-If potassium channels open, K+ leave the cell. Potassium is positively charged, it’s efflux causes a
hyperpolarization. (Inhibitory Postsynaptic Potential – IPSP).
-PSP’s are influenced by other ions depending on the state of the membrane. If the membrane is
resting, Cl ions will not have any effect because diffusion and electrostatic will maintain the healthy
balance. If the membrane has been depolarized, however, the chloride ion channels will permit CL to
enter the cell, causing depolarization, trying to neutralize the EPSP.
-However you can make the membrane very neg, leading to an IPSP.
-Calcium ions affect membrane potential, acting in the same way as Na+ ions. Depolarize membrane,
EPSP. Special role in activating enzymes and organelles which can cause changed to the postsynaptic
The interaction of the excitarory and inhibitory synapses on a particular neuron is called neural
If several excitatory synapses are active at the same time, EPSP will travel toward the axon and the axon
If several inhibitory synapses are active at the same time as the EPSP, the IPSP will diminish the EPSP
and prevent the axon from firing. Travels down the soma to axon hillock, the junction between soma and axon.
Neural inhibition does not always produce behavioural inhibiton. For example. A group of neurons may
prevent me from putting my hand in the fire. If, however, those neurons are inhibitied (prevented from
producing IPSP). Those neurons will NOT suppress my behaviour and I will put my hand in the fire.
-inhibition of inhibitory neurons makes the behaviour more likely to occur.
Neural excitation does not always produce behavioural excitation.
For example, during dreams, a group of inhibitory neurons are activated to prevent us for acting out our
dreams. If activation fails to occur, people will act out dreams.
-excitation of neurons that inhibit a behaviour, suppress that behaviour.
*AUTORECEPTORS – on a neuron, detects neurotransmitters that are released by that neuron. Do not
open and close ion channels, but control regulatory processes, such as synthesis of neurotransmitters.
*axoaxonic synapses – between two terminal buttons. Modulate the amount of neurotransmitters
released by the terminal butons.
PSYCHOPHARMACOLOGY – DRUGS
A chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to
enhance physical or mental well being, (Pharmacological)
A chemical substance that has perceived beneficial effects on perception, consciousness, personality
and behaviour (ex narcotics) some drugs can cause addiction if abused, (Recreational)
An exogenous substance chemical that significantly alters the function of certain cells when taken in
relatively low doses. (anything in high doses alters the general functioning of cells)
Psychopharmacology is the study of the effects of drugs on the nervous system and behaviour.
Routes of Administration:
Drugs have to reach their site of action which is the point where drug molecules interact with molecules
located on or in cells of the body (synapse). Drugs must cross the blood brain barrier.
i) IV (intravenous injection) – into the vien
ii) IP (intraperitoneal Injection) – into the abdominal wall (peritoneal