Chemical and Nervous Control in Animals

• Invertebrates have the ganglion, which is a cluster of nerves that serves as the primary brain that processes information.
• Vertebrates have fully developed brains that are capable of processing more complex information.
• synapse- refers to the connection between neurons where nerve signals are transmitted between them
• presynaptic neuron- terminal part of the presynaptic neuron swells and forms a knoblike structure called the axon terminal
• post synaptic neuron- the axon terminal is often attached to the dendrites of the next neuron, which is usually referred to as the postsynaptic neuron
• The terminal part of the presynaptic neuron swells and forms a knoblike structure 
• A microscopic space or gap called the synaptic cleft that is often 0.02 micron wide.
• Synaptic vesicles- Carry the neurotransmitters
• Neurotransmitter- The general class of chemical messengers that trigger the receiving neuron to elicit a response or continue conducting the information
• receptors- The receiving end of the postsynaptic neurons that allow them to recognize the neurotransmitters
• The first step of action potential generation is the detection of environmental stimuli that triggers sensory neurons.
• An action potential occurs when a substantial shift from negative to positive charge occurs in the membrane of the neuron.
• The action potential is often generated in the cell body of the neuron. After being generated, this electrical signal then travels through the axon.
• The action potential opens calcium ion channels that lead to the influx of calcium ions into the presynaptic neuron.
• This calcium ion influx triggers the synaptic vesicles that contain neurotransmitters to release their contents via exocytosis.
• Neurotransmitters may attach to the receptors present on the membrane of the postsynaptic neuron.
•  Acetylcholine- Enables muscle movement making it the predominant neurotransmitter in neuromuscular junctions
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  Dopamine- Influences learning, attention, memory retention, reward, and motivation
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  Serotonin- Regulates mood, hunger, sleep, and arousal (reuptake of which is inhibited by a prescription drug for people experiencing depression and sleep problems)
• • Action potentials refer to the electrical nerve signals that travel along the entire length of axon until it reaches the axon terminal.
• A synapse or neuronal junction is the point where two neurons are closely associated to facilitate transmission of nerve impulses.
• • Five phases are involved in the generation of action potentials, namely, resting phase, depolarization, overshoot, repolarization, and hyperpolarization.
• • Neurotransmitters refer to the general term for chemical messengers that trigger the receiving neuron to elicit a response.
• Action potentials are more easily transmitted through the saltatory conduction in myelinated neurons than through the continuous conduction in unmyelinated neurons.
• parts daw nas neuron

  A) a. dendrite

  B) b. cell body

  C) c. axon

  D) d. nucleus

  E) e. node of ranvier

  F) f. node terminals

  G) g. Schwann cells

  H) h. myline shealth