ENDURING UNDERSTANDING: NER-1 General functions of the nervous system
1. Describe the general functions of the nervous system.

The nervous system has three basic functions: gathering sensory input from sensory receptors; processing and interpreting sensory input to decide an appropriate response (integration); and using motor output to activate effector organs, muscles and glands, to cause a response.

ENDURING UNDERSTANDING: NER-2 Organization of the nervous system

Compare and contrast the central nervous system (CNS) and the peripheral nervous system (PNS) with respect to structure and function.
1. The central nervous system (CNS) consists of the brain and spinal cord and is the integrating and control center of the nervous system, while the peripheral nervous system (PNS) is outside the central nervous system.
Describe the nervous system as a control system with the following components: sensory receptors, afferent pathways, control (integrating) center, efferent pathways, and effector (target) organs.
1. The nervous system has three basic functions: gathering sensory input from sensory receptors; processing and interpreting sensory input to decide an appropriate response (integration); and using motor output to activate effector organs, muscles and glands, to cause a response.
Compare and contrast the somatic motor and autonomic motor divisions of the nervous system.
1. The somatic nervous system consists of somatic motor nerve fibers that conduct impulses from the CNS to skeletal muscles and allow conscious (voluntary)
  control of motor activities, while the autonomic nervous system (ANS) is an involuntary system consisting of visceral motor nerve fibers that regulate the activity of smooth muscle, cardiac muscle, and glands.
Compare and contrast the somatic sensory and visceral sensory divisions of the nervous system.
1. The sensory, or afferent, division of the peripheral nervous system carries impulses toward the central nervous system from sensory receptors located throughout the body. Somatic sensory fibers carry impulses from receptors in the skin, skeletal muscles, and joints. Visceral sensory fibers carry impulses from organs within the ventral body cavity.
ENDURING UNDERSTANDING: NER-3 Neurons and Neuroglia

Identify and describe the major components of a typical neuron (e.g., cell body, nucleus, nucleolus, chromatophilic substance [Nissl bodies], axon hillock, dendrites, and axon) and indicate which parts receive input signals and which parts transmit output signals.

Neurons function optimally for a lifetime, are mostly amitotic with a high metabolic rate requiring oxygen and glucose.
The neuron cell body, also called the perikaryon or soma, is the major biosynthetic center containing the usual organelles except for centrioles, but there are also arm-like processes that extend from the cell body, the axons and dendrites.

Compare and contrast the three structural types of neurons (i.e., unipolar [pseudounipolar], bipolar, and multipolar) with respect to their structure, location, and function.

Multipolar neurons are most common with three or more
processes. Bipolar neurons have a single axon and dendrite in the retina of the eye and olfactory mucosa. Unipolar neurons have a single process with sensory receptors at the distal end.

Compare and contrast the three functional types of neurons (i.e., sensory [afferent] neurons, interneurons [association neurons], and motor [efferent] neurons) with respect to their structure, location, and function.

Sensory, or afferent, neurons conduct impulses toward the CNS from receptors. Motor, or efferent, neurons conduct impulses from the CNS to effectors. Interneurons, or association neurons, conduct impulses between sensory and motor neurons, or in CNS integration pathways.

Describe the structure, location, and function of each of the six types of neuroglial (glial) cells.

Neuroglia, or glial cells, are closely associated with neurons, providing a protective and supportive network that include CNS: astrocytes, microglia, ependymal, oligodendrocytes; and PNS: satellite and Schwann cells.

Define myelination and describe its function, including comparing and contrasting how myelination occurs in the CNS and PNS.

Oligodendrocytes in the CNS (multi-projection) and Schwann cells (wrap themselves) in the PNS provide myelination as insulation for nerves.

ENDURING UNDERSTANDING: NER-4 Neurophysiology

List the major ion channels of neurons and describe them as leak (leakage or passive) or voltage-gated channels, mechanically gated channels, or ligand-gated (chemically-gated) channels, and identify where they typically are located on a neuron.

Gated ion channels, each of which is selective to a certain type of ion, play an important role in membrane potentials. Chemically gated (ligand-gated) channels open when the appropriate chemical binds. Voltage-gated channels open in response to a change in membrane potential. Mechanically gated channels open when a membrane receptor is physically deformed. When ion channels are open, ions diffuse across the membrane along their electrochemical gradients, creating electrical currents.

Describe the physiological basis of the resting membrane potential (RMP) in a neuron including the ion channels involved, the relative ion concentrations, and the electrochemical gradient.

The membrane of a resting neuron is polarized, and the potential difference of this polarity (approximately–70 mV) is called the resting membrane potential from differences in ionic makeup of intracellular and extracellular fluids,
and differential membrane permeability to those ions.

Describe the role of the sodium-potassium ATPase pump in maintaining the resting membrane potential.

To reestablish RMP, active transport with the ATP pumps move ions against their concentration.

Define and describe depolarization, repolarization, hyperpolarization, and threshold.

Relative to the resting state, potential changes can be depolarizations, in which the inside of the membrane becomes less negative, or hyperpolarizations, in which the inside of the membrane becomes more negatively charged.
After changes in ion gradients, the membrane can be repolarized, but action potentials will not fire until threshold is reached.

Compare and contrast graded potentials and action potentials, with particular attention to their locations in the neuron and the ions and ion channels involved in each.

Graded potentials are short-lived local changes in membrane potentials, can either be depolarizations or hyperpolarizations, and are critical to the generation of action potentials. Action potentials are all-or-none phenomena: they either happen completely, in the case of a threshold stimulus, or not at all, in the event of a subthreshold stimulus

Label a voltage-versus-time diagram of an action potential with the ions involved in each phase, the direction of their movement across the membrane, and the terms depolarize, repolarize, and hyperpolarize, and the different types of membrane channels involved.

At rest, all gated Na⁺ and K⁺ channels are closed. Local currents depolarize the axon, and voltage-gated Na⁺ channels open, allowing Na⁺ ions to enter the cell. As the depolarization reaches threshold, this behavior becomes self-generating. Repolarization, which restores resting membrane potential, occurs as Na⁺ channels inactivate, and K⁺ channels open. Hyperpolarization occurs when some K⁺ channels remain open, allowing excessive efflux of K⁺ produces a slight dip following the spike.

Explain how axon diameter and myelination affect conduction velocity and saltatory conduction.

Larger diameter neurons have a faster conduction rate than smaller diameter neurons. Myelination speeds the conduction rate.

Distinguish between absolute and relative refractory periods and compare the physiological basis of each for the neuronal activity.

The refractory period of an axon is related to the period of time required so that a
neuron can generate another action potential. During the absolute refractory period, extending from the opening of the Na⁺
channels to their closing, the cell cannot respond to another stimulus, regardless of how strong. During the relative refractory period, the Na⁺ channels are mostly reset, the cell is repolarizing, and an exceptionallystrong stimulus may reopen Na⁺ channels and generate another action potential

ENDURING UNDERSTANDING: NER-5 Neurotransmitters, neuromodulators, and synaptic transmission
Define a synapse, and explain the difference between an electrical synapse and a chemical synapse.

Chemical synapses, the most common type of synapse, are specialized for release and reception of chemical neurotransmitters, while electrical synapses have neurons that are electrically coupled via protein channels and
allow direct exchange of ions from cell to cell.

Describe the structures involved in a typical chemical synapse (e.g., axon terminal [synaptic knob], voltage-gated calcium channels, synaptic vesicles of presynaptic cell, synaptic cleft, neurotransmitter receptors of the postsynaptic cell)

Axon terminals from presynaptic neurons have numerous synaptic vesicles that store and secrete neurotransmitters.
A neurotransmitter receptor region on the postsynaptic neuron’s membrane, usually located on a dendrite or the cell body.

Describe the events of synaptic transmission in proper chronological order from the release of neurotransmitter by synaptic vesicles to the effect of the neurotransmitter on the postsynaptic cell.

An action potential arrives at the axon terminal. Voltage-gated Ca²⁺ channels open and Ca²⁺ enters the axon terminal. Ca²⁺ entry causes synaptic vesicles to release neurotransmitter by exocytosis. Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane. Binding of neurotransmitter opens ion channels, creating graded potentials. Neurotransmitter effects are terminated.

Describe the difference between fast synaptic responses (ion channel [ionotropic] receptors) and slow synaptic responses (second messenger-linked metabotropic receptors).

There are two main types of neurotransmitter receptors: Channel-linked receptors mediate fast synaptic transmission and result in brief, localized changes, and G protein–linked receptors mediate indirect transmitter action resulting in slow synaptic responses.

Define excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP) and interpret graphs showing the voltage-versus-time relationship of an EPSP and an IPSP.
1. At excitatory synapses, neurotransmitters bind to chemically gated ion channels,
  causing depolarization of the membrane, and generation of excitatory postsynaptic
  potentials (EPSPs), that can trigger action potentials at the axon hillock if they are of adequate strength.
2. At inhibitory synapses, neurotransmitters hyperpolarize the membrane, by making it more permeable to K⁺ or Cl- moving membrane potential away from threshold, and making generation of an action potential less likely.
Explain how a single neurotransmitter can elicit different responses at different postsynaptic cells.

Depending on the neurotransmitter, receptor, and strength of signal (neuromodulation), each cell may have a different response.

Explain temporal and spatial summation of postsynaptic potentials.

Temporal summation, which occurs in response to several successive releases of neurotransmitter, and spatial summation, which occurs when the postsynaptic cell is stimulated at the same time by multiple terminals.

Describe the different mechanisms (e.g., reuptake, enzymatic breakdown, diffusion) by which neurotransmitter activity at a synapse can be terminated and changed.

Neuronal activity can be modified based on enzymatic breakdown or enhancement, size of synaptic cleft, and receptor type and quantity.

ENDURING UNDERSTANDING: NER-6 Integration of neural information
Define neural (neuronal) circuit.

Neuronal pools, processing, and circuits allow for complex behaviors to develop and sustain.

Compare and contrast the different types of neural circuits (e.g., converging, diverging).

The patterns of synaptic connections in neuronal pools, called circuits, determine the pool’s functional capabilities.

Define neural plasticity.

As a neuron is used more, the signal will be stronger incoming and outgoing.