PSYC 2410 Chapter Notes - Chapter 3: Periaqueductal Gray, Silver Nitrate, Cranial Nerves
Chapter 3- Anatomy of the Nervous System
LO 3.1- List and describe the major divisions of the nervous system
The nervous system is a system of cells, tissue and organs that regulates the body’s
responses to internal and external stimuli.
The vertebrate nervous system consists of the Central Nervous System (CNS) and
the Peripheral Nervous System (PNS).
The CNS is divided into two divisions: the brain (in the skull) and the spinal cord (in the
spine)
The PNS is the part of the nervous system that is located outside of the spine and skull.
the PNS is divided into two divisions: the somatic nervous system and the autonomic
nervous system.
Both of these divisions are composed of afferent nerves and efferent nerves.
Afferent nerves carry sensory signals from the PNS to the CNS and efferent nerves
carry motor signals from the CNS to the PNS.
The autonomic nervous system is responsible for regulating the internal environment.
The autonomic nervous system is further divided into the parasympathetic nervous
system and the sympathetic nervous system which are both efferent (carry signals from
the CNS in a two stage neural pathway).
These two systems differ from each other in how they ‘communicate’ with the body.
The sympathetic efferent nerves synapse on neurons that are far away from their
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targets while the parasympathetic efferent nerves synapse with neurons very close to
their target.
Three basic principles:
1) sympathetic nerves mobilize energy resources; parasympathetic nerves conserve
energy
2) each autonomic target receives signals from both systems
3) sympathetic activation indicates arousal while parasympathetic activation indicates
relaxation.
The cranial nerves are a special group of nerves that project directly from the brain
(instead of the spinal cord like most nerves of the PNS) and through the skull.
They have specific sensory and/or motor functions and disruption of these functions is
one neurological assessment tool for accurate determination of the location and size of
tumors and other types of brain pathology.
LO 3.2- Describe the three meninges explain their functional role
the brain and the spinal cord are the most protected organs in the body they are
encased in bone and covered by three protective membranes the meninges
In order from outside to inside the membranes are called: dura mater (tough
mother), arachnoid mater (spidery mother) and pia mater(pious/gentle mother).
The dura meninx is like a bathing cap, tough and tight fitting.
The arachnoid meninx is immediately below the dura and above the subarachnoid
space that contains large blood vessels and cerebrospinal fluid (CSF).
The inner pia meninx adheres directly to the surface of the CNS.
LO 3.3-Explain where cerebrospinal fluid is produced and where it flows
Cerebrospinal fluid fills the subarachnoid space, central canal of the spinal cord and the
cerebral ventricles (lateral, third, fourth and cerebral aqueduct) of the brain (see Figure
3.3).
It is produced by the choroid plexuses (small blood vessels in the pia mater that
protrude into the ventricles).
Excess fluid is absorbed from the subarachnoid space into large sinuses in the dura
mater and drained into the blood stream.
Blockage of the flow of CSF results in hydrocephalus, literally translated (from Greek)
as water head.
the resulting buildup of fluid in the ventricles causes the walls of the ventricles and thus
the entire brain to expand producing a condition called hydrocephalus
LO 3.4- Explain what the blood-brain barrier is and what functional role it serves
The passage of large molecules from the generally circulating blood stream to the brain
is controlled by the blood-brain barrier (BBB).
Cells of the blood vessels in the brain are much more tightly packed thereby impeding
the passage of many large molecules through this protective barrier.
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degree to which therapeutic or recreational drugs can influence brain activity depends
on the ease with which they penetrate the blood-brain barrier
LO 3.5- Draw, label, and Define the major features of a multipolar neuron
Of the hundreds of billions of different cells in the nervous system there are two
types: neurons or glial cells.
Neurons are specialized cells for the reception, conduction and transmission of
electrochemical signals and are found in many sizes and shapes.
Glial cells outnumber neurons 10:1.
External Anatomy of Neurons
cell membrane: a semipermeable membrane that allows chemicals to cross
cell body: the metabolic center of the cell containing the nucleus (cell’s DNA)
dendrites: short processes emanating from the cell body that receive information from
synaptic contacts with other neurons
axon: a single projection from the cell body that can be as long as one meter
axon hillock: the junction between the cell body and axon which is critical for the
conveyance of electrical signals by the neuron
myelin sheaths: these sheaths insulate the axon and assist in conduction of electrical
signals. They are formed by oligodendroglia in the CNS and Schwann cells in the PNS
nodes of Ranvier: small spaces between adjacent myelin sheaths that allow salutatory
conduction (faster transmission of electrical signal along the axon)
buttons: branched endings of the axon that release chemical signals allowing the
neuron to communicate with other cells
synapses: the point of communication between the neuron and other cells
Cells of the Nervous System
Four basic classes of neurons: (based upon the number of processes that emanate from
the cell body)
Unipolar: one process extends from cell body
Bipolar: two processes extend from cell body
Multipolar: more than two processes extending from cell body
Multipolar Interneuron: short or no axon
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Document Summary
Lo 3. 1- list and describe the major divisions of the nervous system. The nervous system is a system of cells, tissue and organs that regulates the body"s responses to internal and external stimuli. The vertebrate nervous system consists of the central nervous system (cns) and the peripheral nervous system (pns). The cns is divided into two divisions: the brain (in the skull) and the spinal cord (in the spine) The pns is the part of the nervous system that is located outside of the spine and skull. the pns is divided into two divisions: the somatic nervous system and the autonomic nervous system. Both of these divisions are composed of afferent nerves and efferent nerves. Afferent nerves carry sensory signals from the pns to the cns and efferent nerves carry motor signals from the cns to the pns. The autonomic nervous system is responsible for regulating the internal environment.
