Physiological Psychology Chapter 2

How did Sherrington discover neurons communicate via a synapse?

He discovered a delay in reflexes that could not be accounted by the time for an action potential to travel along an axon, leading him to conclude the existence of a synapse.

EPSP

Excitatory postsynaptic potential, where sodium ions flow into the neuron, potentially depolarizing it and leading to an action potential.

IPSP

Inhibitory postsynaptic potential, where potassium ions leave or chloride ions enter the neuron, hyperpolarizing it and decreasing the likelihood of an action potential.

What is temporal summation?

The build-up of separate stimuli attacking one neuron to produce a response.

What is spatial summation?

The build-up of separate stimuli from multiple neurons to produce a response.

Major events at a synapse

1. Neurotransmitter synthesis in cell body.

2. Action potential triggers calcium entry releasing neurotransmitters.

3. Released molecules bind to receptors on postsynaptic neuron.

4. Neurotransmitter molecules separate from receptors.

5. Reuptake or diffusion of neurotransmitters.

6. Reverse messages from postsynaptic cells control neurotransmitter release.

Example of behavior relying on metabotropic mechanisms

Smelling, as it relies on less instant information.

Example of behavior relying on ionotropic mechanisms

Vision, which often requires instant responses.

G-protein

A protein that sends messages within the cell to trigger the second messenger

What is the first messenger?

The neurotransmitter that conveys signals from outside the cell.

Common second messenger

Cyclic adenosine monophosphate (cyclic AMP).

Differences between neuropeptides and neurotransmitters

1. Neuropeptides can release from multiple parts of the neuron, not just axon terminals.

2. Neuropeptides require repeated stimulation.

3. Neuropeptides affect a wider area than adjacent cells.

How do drugs like cocaine affect dopamine synapses?

They block reuptake, prolonging neurotransmitter effects but leading to quicker breakdown by COMT, causing withdrawal.

How do hormones differ from neurotransmitters?

Hormones send messages throughout the body via the bloodstream, while neurotransmitters send messages from cell to cell.

Ionotropic synaptic mechanism

mechanisms are faster and simpler, using neurotransmitters that bind to channels

Metabotropic synaptic mechanism

mechanisms are slower, involve metabolic processes, and have lasting effects.

MAO

breaks down excess of neurotransmitters

vesicles

that store neurotransmitters in the presynaptic neuron until they are released into the synaptic cleft.

exocytosis

is the process by which vesicles release neurotransmitters into the synaptic cleft.

activating receptors of the post cell

is the action that occurs when neurotransmitters bind to specific proteins on the surface of the postsynaptic neuron, leading to a response in that cell.

g-proteins

• triggers second messenger

• connected to GTP

• system that mediates cellular responses after receptor activation.

autoreceptors

detect the amount of neurotransmitters released and stop further release

hormones

chemicals secreted by the endocrine gland

• transported by blood

• long lasting change

hypothalamus

a region of the brain responsible for regulating various physiological processes like the release of hormones from the pituitary gland.

anterior pituitary

• composed of glandular tissue

• composes 6 hormones that are not important enough to be named

posterior pituitary

• composed of neural tissue

• releases oxytocin and vasopressin into blood

methylphenodite/ritalin

also blocks reuptake of dopamine but at a much more controlled rate