Receptors on postsynaptic neurons are connected to ion channels. When the neurotransmitter binds to the receptor, the channel opens, making that neuron more or less likely to have an action potential depending upon which type of ion the channel allows to enter or exit the neuron. The result is either an excitatory postsynaptic potential (EPSP) or an inhibitory postsynaptic potential (IPSP).

The parasympathetic division of the autonomic nervous system promotes the "rest and digest mode." The somatic nervous system controls voluntary skeletal muscles, but the parasympathetic nervous system controls involuntary smooth & cardiac muscles. The neurons of the parasympathetic nervous system release acetylcholine, which is a neurotransmitter that leads to a decrease in heart rate and blood pressure. Results of increased parasympathetic activity include: decreasing blood flow to skeletal muscles, increasing blood flow to the gut, constricting pupils, and glycogenesis. 

The correct answer is ACh (acetylcholine) because it is involved with muscle contraction. It is released at the neuromuscular junction, the site where the neuron and muscle meet.

The brain is often divided into four lobes based on anatomy and physiology: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. Each lobe controls various aspects of cognition and motor skills. The frontal lobe is associated with reasoning, speech, movement, and emotions. The parietal lobe is associated with orientation and recognition. The occipital lobe is associated with visual processing. The temporal lobe is associated with auditory processing and memory.

Broca's area is a small region of the frontal lobe located in the left hemisphere. This region of the brain is responsible for generating speech and articulation. Damage to this region of the frontal lobe could cause speech impairment. In contrast, Wernicke's area is located in the temporal lobe and is associated with comprehension of speech.

Spastic muscle activity is not related to the brain, but results from injury to motor neurons spanning from the spinal cord to the limbs.

Synapses are special regions where a neuron releases a signal to its target cell. Most commonly this signal is chemical (neurotransmitters), but it can also be electrical. The synapse is a gap between the neurons, and does not allow for direct contact. Signals are released from the axon of one neuron and must traverse the synaptic cleft before interfacing with receptors on the target cell.

Neurons do not directly release hormones into the blood stream and synapses do not offer protection to neurons.

Phototaxis is movement (taxis) in response to light (photo). Movement towards a source is positive; movement away from a source is negative. "Positive phototaxis" would be used to describe movement toward a light source.

Glial cells are non-neuronal cells that support neuron activity. Their functions include physical support of neurons, supply oxygen and nutrients, and take up excess neurotransmitters. 

Neurotransmitters and hormones are both chemical signals, but hormones are used in the endocrine system, released from glands into the blood, while neurotransmitters are released from the axon terminals of neurons to signal other neurons. Signals travel across neurons as electrical signals caused by the movement of large numbers of atomic ions across the membrane via protein channels. Charged proteins would be too large to quickly move through the channels in such large numbers.

Schwann cells are responsible for the myelination of axons in the peripheral nervous system.

Oligodendrocytes also myelinate axons, but they are found in the central nervous system. Astrocytes and satellite cells help support neurons, but do not contribute myelin to axons.

The central nervous system houses the brain and spinal cord only. The peripheral nervous system refers to all other nervous structures in the body.

Free nerve endings are usually located just under the skin, and respond to pain and large changes in temperature, making them part of the peripheral nervous system.

Oligodendrocytes, white matter, and gray matter are only found in the central nervous system. Interneurons are most commonly found in the spinal cord, but can be found in either the peripheral or central nervous system.