Biology

Divergent pathways vs. convergent pathways
In divergent pathways, weak signals from one source enter a pool of neurons to excite a larger number of nerve fibers. On the other hand, in convergent pathways, signals originate from multiple sources to stimulate a single neuron.

Spatial summation vs. temporal summation
Both spatial and temporal summations are ways by which neurons are stimulated. In spatial summation, the post-synaptic neuron simultaneously receives stimulations several pre-synaptic neurons. In temporal summation, the post-synaptic neuron receives two or more successive stimulations from one pre-synaptic neuron.

Excitatory action vs. inhibitory action
Synaptic potentials between two neurons can either be excitatory or inhibitory. Excitatory action happens when sodium and potassium ion channels are open, which, in turn, depolarizes the cell membrane. As a result, there are increased chances of generating action potentials. On the other hand, inhibitory action happens when potassium and chloride ions are open. It hyperpolarizes the membrane, which makes the neuron less likely to trigger an action potential.

Afferent vs. efferent axons
Afferent axons carry impulses towards the central nervous system hence, these are sensory in nature.  On the other hand, efferent neurons carry impulses away from the central nervous system, making it motor in nature. Coordination of afferent and efferent neurons is very important in many conditions such as reflex actions,

Results of sympathetic stimulation vs. results of parasympathetic stimulation
Sympathetic stimulation results to fight and flight response while parasympathetic stimulation results to rest and digest response. Usually, sympathetic stimulation results to mass discharge or localized response while parasympathetic stimulation results to specific localized response.

Sensitization vs. Habituation
Sensitization is the process by which an individual develops heightened response to a particular stimulation after being repeatedly exposed to it. On the other hand, habituation is the process by which an individual develops decreased response after being repeatedly exposed to the same stimulus over a period of time.

Anatomy of SNS vs PSNS
The sympathetic and parasympathetic systems are both constituent parts of the autonomic nervous system. However, they differ in the location or origin of the nerve fibers such that the sympathetic nervous system, being the thoracolumbar division of the autonomic system, arises from spinal cord level T1-L23, while the parasympathetic nervous system, being the craniosacral division, arises from cranial nerves III, VII, IX, X (cranial part) and spinal nerves II, III, IV (sacral part).

What is the relationship between the sensation experienced and the location in the CNS of the termination of the impulse
Sensory stimulation from different parts of the body are represented in the post-central gyrus of the brain, also known as Brodmann Areas 3,1,2 or the somatosensory area. Special senses are represented in different areas of the brain (e.g. visual cortex located at Brodmann Area 17, auditory cortex at Brodmann Area 41  42, etc.). This simply means that the last order neurons in the sensory pathways reach different destinations in the brain where different sensations would be interpreted.

What is the purpose of ACh in the adrenergic ANS
Acetylcholine is a neurotransmitter hence it facilitates communication among different nerve fibers. In sympathetic nervous system, the pre-ganglionic neuron secretes acetylcholine and stimulates the nicotinic receptors in the ganglion. Upon stimulation, the post-ganglionic neuron secretes norepinephrine to consequently stimulate the adrenergic receptors in the effector cell. On the other hand, in parasympathetic nervous system, the pre-ganglionic neuron secretes acetylcholine that binds to the nicotinic receptors of the post-synaptic neuron. After being stimulated, this post-synaptic neuron would also secrete acetylcholine  to stimulate the muscarinic receptors of the effector cell.

The structure and function of pain receptors
Receptors for pain can be classified as chemoreceptors, thermoreceptors and mechanoreceptors. There are four types of mechanoreceptors that mediate pain. First, the Meisnner Corpuscles that are basically stimulated by texture changes and slow vibrations. These receptors have encapsulated dendrite. Second, when  pressure and touch are maintained, Merkels Corpuscles are the ones that detect these stimulations. In addition, Ruffinis Corpuscles also detect sustained pressure. In terms of structure, they are larger and with elongated capsules. Lastly, deep pressure and fast vibration are sensed by Pacinian Corpuscles, whose structure resembles an onion with concentric lamellae of connective tissue encapsulating the endings of the dendrites of the sensory neuron.

The purpose of interneurons
Interneurons, which are small multipolar neurons, function to relay impulses between afferent and efferent neurons.  They secrete GABA as their neurotransmitter to hyperpolarize principal cells, thus, inhibiting them.

The function of the limbic system
The limbic system primarily functions in emotional activities that are necessary for self-preservation of individual such as feeding, procreation and care for offspring.

Monosynaptic reflexes, including after spinal cord transaction
Monosynaptic reflex only involves one synapse between the sensory and the motor neuron. Stretch, myotactic and muscle spindle reflexes are all monosynaptic in nature. Since there is only one synapse, there is a very minimal delay in the relay of impulses in the spinal cord, resulting to a rapid response of the effector organ. After a spinal cord transaction, spasticity results as the stretch reflex becomes highly excitable.

All organ system effects of both SNS and PSNS stimulation
Both parasympathetic and sympathetic nervous systems have antagonistic effect on their target organs that have dual innervations. However, there are certain exceptions for some organs. For instance, while salivary glands have both types of innervations, the effects are of different characteristics. The parasympathetic nervous system promotes secretion of large quantity of watery saliva while the sympathetic stimulation promotes concentrated secretion with added enzymes and mucus. In addition, during intercourse, the parasympathetic system is responsible for penile and clitoral erection and vaginal engorgement and secretion while the sympathetic system is responsible for ejaculation and contraction of smooth muscles of the vagina. Moreover, sweat glands, erector pili, release of renin from kidneys only have sympathetic stimulation.

Factors that increase and decrease the rate of nerve impulse transmission
The thickness of the axon affects rate of transmission because a thick axon provides larger surface area by which ion exchange can occur. Also, the more myelinated an axon, the faster is the rate of impulse transmission. Moreover, the rate of nerve impulse transmission is also affected by rate of respiration since reestablishment of resting membrane potential is an ATP-dependent process and ATP is generated by metabolic processes that occur during cellular respiration.