Neural Communication

1. Neural Communication This is anything that deals with the synapse and the neurons communication with each other By: Ryan Gov Sera Choi Iris Gonzalez

2. Movement of information • Information in the nervous system moves to other locations through action potentials • These electrical movements are nerve impulses • Chemicals 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 cells • Neuronglandular junctions are where a neuron controls the activity of a secretory cell.

3. 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

5. 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.

6. The sequence of events for a cholinergic synapse • Step 1 • An 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

7. Step 3 • ACh binds to receptors and depolarizes the postsynaptic membrane • The 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 4 • Then 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

8. 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

10. 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.

11. 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 CNS • A neuronal pool is a group of interconnected interneurons with specific functions. • Neuronal pools have limited numbers of input sources and output destinations • Thus 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.

12. 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.

13. 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 pools • There 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.

14. Convergence • Convergence is when several neurons synapse on a single postsynaptic neuron. • This makes both voluntary and involuntary control of some body processes • Ex: 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.

15. 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.

16. 1. Nerve impulses • 2. 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