The Nervous System Anatomy

The nervous system is the master coordinating system of the body. Every thought, action, and sensation reflext its activity. The structures of the nervous system are described in terms of 2 principal divisions-the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS (brain and spinal cord) interprets incoming sensory information and issues instructions based on past experience. The PNS (cranial and spinal nerves and ganglia) provides the communication lines between the C…
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Terms in this set (...)

Central nervous system
Part of the nervous system that is made up of the brain and spinal cord. It interprets incoming messages and sends messages out to the peripheral nervous system.
Peripheral nervous system
Part of the nervous system that consists of all of the nerves of the body. These nerves receive stimuli and send information to the central nervous system. They also receive directions from the central nervous system and control direct actions.
Motor division
Carries messages from the Central Nervous System to the internal organs, glands, and muscles (afferent- away)
Sensory division
Carries messages from the sense organs (eyes, ears, receptors in skin, etc...) and internal organs to the central nervous system.
Somatic nervous system
Part of the peripheral nervous system that carries messages to muscles under VOLUNTARY control.
Autonomic nervous system
Part of the peripheral nervous system that carries messages to organs and glands. This is AUTOMATIC and INVOLUNTARY.
Sympathetic nervous system
Part of the autonomic nervous system, it prepares the body for emergencies. Responsible for "FIGHT OR FLIGHT."
Parasympathetic nervous system
Part of the autonomic nervous system, it controls the body during non-emergencies and brings things back to a resting state. Responsible for "REST AND DIGEST."
Neurons
Nerve cells. They carry electrical messages from one area of the body to another area.
Dendrite
The branched part of the neuron that receives incoming messages from other neurons. They send electrical messages TOWARD the cell body.
Myelin
An insulating layer (made mainly of fat and protein) along the axon of a nerve cell. It speeds up the message along the axon.
Cell body
The large part of a neuron, where the nucleus is located. It connects the dendrites and axon of the neuron to each other.
Axon
The long part of a nerve cell, it conducts impulses away from the cell body.
Stimulus
A change in the environment that can be perceived by sensory receptors (sound, light, pain, temperature, etc...)
synapse
A gap or space between two neurons. This is where the electrical signal from the axon is converted into a chemical message and passed across the gap to the dendrites of the next neuron.
neurotransmitter
Chemical molecules that transmit a message across the synapse from one neuron to another neuron.
Reflex
An action that is performed as a response to a stimulus without any conscious thought. For example, a bug flies near your eye and you blink without thinking about it.
Reflex arc
A pathway within the spinal cord that controls a reflex.
Association neuron
Also known as an interneuron, these types of neurons work in reflexes by connecting sensory and motor neurons together.
Brain
An organ that is the main processing center of the nervous system.
Brainstem
Connects the brain to the spinal cord. Controls involuntary, life-sustaining activities such as breathing, heart rate, sleeping, and maintaining consciousness.
Spinal cord
Long bundles of neurons that run inside of your vertebral column. It carries impulses from all parts of the body to the brain and from the brain to all parts of your body. Reflex arcs occur here.
Hypothalamus
Regulates processes of the autonomic nervous system such as temperature control, hormone production, thirst, and fatigue (being tired).
Cerebellum
Cauliflower-shaped part of the brain found at the base of the back of the head. It is responsible for the coordination of muscles and is the center of balance.

Shown at the end of the blue arrow in the photo.
Hypothalamus
A neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion.

Structure #3
Cerebrum
The largest part of the brain. Divided into two hemispheres (right and left halves). It is also broken into four different lobes.

Green area with question mark in the diagram.
Frontal lobe
This is the largest and longest lobe in each hemisphere (side of the brain). Located in the upper forward half. This area is involved with higher-order thinking such as planning for the future, problem-solving, personality, decision making, controlling emotions and speech production. Motor control is also found at the back of this lobe.

Colored blue in the diagram.
Temporal lobe
Located on the sides of the brain, near the temples of the head. This is where the processing centers for hearing are located. Visual memories are processed here.

Green in the image.
Occipital lobe
Found in the back of the brain. This is where the processing centers for vision are located.

Red/pink in the image.
Parietal lobe
Where the processing centers for speech, taste and reading are located.

Yellow in the image.
Right hemisphere
The right side of the cerebrum of the brain. It controls the left side of the body.
Left hemisphere
The left side of the cerebrum of the brain. It controls the right side of the body.
Function of the nervous system; 3 overlapping functions
A. Sensory - Sense stimuli by receptors and relay to the central nervous system B. Integration - Process and evaluate sensory information. Formulates response C. Motor - Carry out response by sending impulses to effector organs in the body
Name the five distinguishing characteristics of all neurons.
Excitability, conductivity, secretion, extreme longevity, amitotic
know parts of nerons
Dendrites
receive stimuli from other neurons or cells or external sources.
The dendrites and the cell body is known as the receptive region of the neuron
Normally, sodium and potassium leakage channels differ because
sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell
A resting membrane potential of -70 mV indicates that the
charges lining the inside of the plasma membrane are negative compared to the charges lining the outside
Graded potentials are produced within the _______________________ segment of a neuron.
receptive
Graded potentials result from the opening of ________________.
ligand-gated channels
An inhibitory postsynaptic potential results from the opening of____________________
potassium and/or chloride channels
Indicate the summative effect that brings the initial segment closest to threshold.
Two EPSPs in proximity to each other
_______________ the time between signals sent from the same presynaptic terminal increases the strength of the graded potential. This is an example of ________________ summation.
Reducing; temporal
Substances that cause facilitation of a neuron ____________________________.
cause the neuron to fire that may not under the same circumstances in the absence of the facilitator
Assume in a laboratory you were able to isolate a neuron and remove the Acetylcholine receptors from the postsynaptic membrane. The substance _________________ would no longer cause facilitation of this neuron.
nicotine
When voltage-gated sodium channels are open, sodium flows _____________ the neuron making the inside of the cell more _______________.
into; positive
The following information best describes the _____________ phase of an action potential.

• A membrane potential reading of +10 mV
• Inactivated voltage-gated sodium channels
• Open voltage-gated potassium channels
repolarization
Action potentials occur
in the unmyelinated regions of an axon
Demyelinating diseases cause a(n) ______________ in the conduction velocity of action potentials.
decrease
If demyelination occurs, why don't action potentials occur at regions of the axon that were previously myelinated?
These regions lack the appropriate concentration of voltage-gated sodium channels.
High concentrations of voltage-gated sodium channels are localized within the nodes of Ranvier and are generally lacking within the myelinated regions. This arrangement leads to detrimental consequences in individuals suffering from demyelinating diseases, which include any disorder that causes damage of the myelin sheath. In these diseases, an action potential does not propagate down the axon because the voltage-gated sodium channels are too far apart. Charge will leak across the membrane where the myelin once was, and the nodes of Ranvier containing the voltage-gated sodium channels will not reach threshold.

Multiple sclerosis is the most common demyelinating disease. The immune system of individuals suffering from this disease attacks the myelin sheaths found in the central nervous system. This progressive disease is more common in women and is typically diagnosed between ages 20 and 40.

Guillain-Barré syndrome is a rare condition in which the myelin sheaths in the peripheral nervous system are attacked by the immune system. Symptoms of this disease range from slight tingling and weakness of the legs to fluctuation in heart rate and blood pressure, which can be life-threatening. Death may occur if the nerves leading to the respiratory muscles become damaged and asphyxiation results.
...
At the synaptic knob, voltage-gated ______________ channels open, thereby stimulating the synaptic vesicles to release their neurotransmitters by exocytosis.
calcium
If acetylcholinesterase became mutated and nonfunctional, what would be the immediate result?
Acetylcholine would build up in the synaptic cleft.
If a drug was developed that interfered with the proper functioning of the microtubules found within the axons of neurons, how would you expect this to impact axonal transport processes?
Both anterograde and retrograde transport processes would cease.
The enzyme choline acetyltransferase catalyzes the reaction between acetyl-CoA and choline resulting in the formation of the neurotransmitter acetylcholine. This enzyme is produced within the cell body of neurons, but the synthesis of acetylcholine occurs within the axon terminals. Which statement best describes the axonal transport mechanism associated with this process?
Choline acetyltransferase is transported in the anterograde direction.
Suppose that a new virus is discovered that specifically infects motor neurons. Assume that this virus enters neurons in conjunction with choline molecules. Once inside the cell, the virus enters the nucleus and replicates. Which direction describes the axonal transport route taken by this virus?
Retrograde transport
An inhibitory post synaptic potential (IPSP)
will make the membrane potential of a neuron's inner cell membrane more negative.
An excitatory post synaptic potential (EPSP)
will make the membrane potential of a neuron's inner cell membrane more positive.
An EPSP will cause
both sodium and potassium gates to open, allowing sodium to diffuse into the cell and potassium to diffuse out of the cell.
Depolarization of a cell membrane occurs because
more sodium ions diffuse into the cell than potassium ions diffuse out of it.
Depolarization is initiated by a stimulus that makes the membrane potential
more positive.
Activation gates in the cell membrane for voltage-gated sodium ion channels open into the
extracellular fluid.
The cell membrane immediately adjacent to an action potential depolarizes because of
local currents.
What is produced when depolarization of a cell membrane reaches threshold?
A new action potential is produced.
The absolute refractory period assures that action potential propagation is
only in one direction.
Upon arriving at the node of a myelinated neuron, the excitatory postsynaptic potential (EPSP) causes

As a result...
the neuron's inner cell membrane to become more positively charged.


the sodium channels open and sodium ions pour into the intracellular fluid.