1.a. Key Parts of the Control Center; The Receptors; The neurons and nerve cells;
Sensory Neuron: transmits nerve impulses from receptors to coordinators.
Relay Neuron: Transmits nerve impulses from Sensory Neurons to Motor Neurones.
Motor Neurones: Transmits nerve impulses from the central nervous system (brain & spinal cord) to effector nerve cells.
c. Reflex Action:
Stimulous >> recept cells >> coordinators (CNS) >> effector cells
A synapse is what happens when chemical signals pass from one cell to another. It occurs in the synaptic cleft, which is the tiny gap between the pre-synaptic neuron and the post-synaptic neuron.
Every pre-synaptic neuron has vesicles inside, near the pre-synaptic membrane. Each vesicle contains thousands of neurotransmitters. When the pre-synaptic neuron gets “excited” by an axon potential it’s vesicles diffuse through the cell membrane and release their content into the synaptic cleft.
Following, the tiny receptors of the post-synaptic neuron interact with the neurotransmitters. These ones bind into the receptors and cause an action as result. Likelihood can be increased and the cell becomes activated firing an action potential or it can be decreased.
Finally, the neurotransmitters molecules left in the synaptic gapdrift away by diffusion, or go back to the vesicles to be reused by a process called re-uptake, or are broken down by enzymes and component parts go back to the pre-synaptic neuron.