By: Ryan GovSera Choi

Iris Gonzalez

This is anything that deals with the synapse and the neurons communication with each other

Movement of informationInformation in the nervous system moves to

other locations through action potentialsThese electrical movements are nerve

impulsesChemicals known as neurotransmitters

transfer the information when released. In neuron communication, the synapse may be

at the dendrite, cell body, or the axon. Neuroeffector junctions are synapses

between a neuron and other types of cellsNeuronglandular junctions are where a neuron

controls the activity of a secretory cell.

Structure of a synapse Communication between neurons occur in only

one direction across a synapse.An impulse can travel from the synaptic knob of

the presynaptic neuron to the postsynaptic neuron.

The opposing cell membranes are separated by narrow spaces called a synaptic cleft.

The synaptic terminals have mitochondria, synaptic vesicles, and endoplasmic reticulum.

Synaptic vesicles have thousands of molecules of specific neurotransmitters.

When the vesicles release these neurotransmitters they diffuse across the synaptic cleft, then they bind to the receptors

Functions and neurontransmitters

There are many different neurotransmitters, an example being acetylcholine or ACh.

The cholinergic synapses is where the ACh is released, and these are numerous in and out of the Central Nervous system.

Another common neurotransmitter is norepinephrine (NE), or nonadrenaline.

NE is important to the brain and the autonomic nervous system.

Dopamine is another important neurotransmitter in the central nervous system

Serotonin is a neurotransmitter important to the mood of humans, it is known as the “happy hormone” even though its not a hormone.

Step 1An action potential arrives and depolirizes the

synaptic knob.The binding of ACh to sodium channels causes them

to pen and allows sodium ions to enter.Step 2

Calcium ions enter the cytoplasm of the synaptic knob

ACh release occurs through exocytosis of nuerotransmitter.

The release ends quickly because the calcium ions are removed from the cytoplasm by active transport

The sequence of events for a cholinergic synapse

Step 3ACh binds to receptors and depolarizes the

postsynaptic membraneThe binding of ACh to sodium channels causes

them to open and allows sodium ions to enter If the depolarization of the postsynaptic

membrane reaches threshold, an action potential is produced.

Step 4Then the removal of ACh by AChE occurs The effects on the postsynaptic membrane is

temporary because of AChE The AChE removes ACh by breaking it into

acetate and choline

In the central nervous system, there are 50 other neurotransmitters that are not well understood

There are also gases that are important to neurotransmitters: nitric oxide and carbon monoxide

Neurotransmitters released from the synapse can have either excitatory or inhibitory effects

Excitatory effects means the nerve cells have a higher probably of producing an action potential

Inhibitory effects is when the intensity of the action potential is suppressed

ACh and NE have an excitatory effect Dopamine and serotonin are usually inhibitory

The action potential depends on the balance of depolarization and hyperpolarizing stimuli arriving.

The activity of a neuron depends on the balance between excitation and inhibition.

These interactions between neurons are very complex and somewhat confusing

The synapses at the cell body and dendrites may involve tens of thousands of other neurons.

Some neurons will be releasing excitatory neurotransmitters while others inhibitory.

Neuron pools A human has about 10 million sensory neurons, 20

billion interneurons, and one-half million motor neurons

This is the simplest form of organization in the CNSA neuronal pool is a group of interconnected

interneurons with specific functions. Neuronal pools have limited numbers of input

sources and output destinationsThus the output of one pool may stimulate or

depress the activity of other pools The neuronal pool may also exert direct control

over motor neurons or peripheral effectors.

Neurons and neuronal pools communicate in different patterns called neural circuits

The two simple circuit patterns are divergence and convergence.

This is how information spreads from one neuron or neuronal pool to other neurons or neuronal pools

Divergence occurs when sensory neurons bring sensory information to the CNS

This is due to the distribution of the sensory information through the brain and the spinal column

Ex: The information from your eyes reaches your conscious awareness at the same time its carried to the areas of the brain that control posture and balance at the subconscious level.

Divergence can also be involved with other responses

Ex: when you step on a sharp object The action stimulates sensory neurons that

distribute information to neuronal poolsThere will be several possible reactions:

withdrawing your foot, shifting your weight, moving your arms, feeling the pain, or saying ouch

This all may even happen at the same time  When the neuron fires, the signal is sent to

many other neurons, resulting in a divergence of output.

Convergence Convergence is when several neurons

synapse on a single postsynaptic neuron. This makes both voluntary and involuntary

control of some body processesEx: the movement of your diaphragm now.

The movement is being involuntarily controlled by the brain

These movements can be controlled voluntarily too

When you take a deep breathe and hold it. Two neuron pools are involved, and both

synapse on the same motor neuron.

Quiz time!!!! 1. What are the electrical movements that

help disperse information between neurons?2. Name at least two neurotransmitters and

what their functions are. 3. How is an action potential produced?4. Describe the two effects a neuron can

have.5. Describe the two simple circuits of a

neuron.

1. Nerve impulses2. Serotonin (mood regulator) and Dopamine

(important in the CNS) 3. If the depolarization of the postsynaptic

membrane reaches threshold, an action potential is produced.

4. excitatory and inhibitory 5. divergence or convergence