Psyc2410 – Chapter 3
3.1 General Layout of the Nervous System
Divisions of the NS: human NS consists of the PNS (outside skull and spine) and CNS (brain + spinal cord).
Central Nervous System
Peripheral Nervous System
Somatic Nervous System (SNS) part that interacts with the external environment. Composed of afferent nerves
that carry sensory information from the skin, skeletal muscles, joints, eyes, ears, etc. to the CNS
Autonomic Nervous System (ANS) part that regulates the body’s internal environment. Composed of afferent
nerves that carry sensory signals from internal organs to the CNS and efferent nerves that carry motor signals from
the CNS to internal organs. Efferent Nerves of ANS: sympathetic and parasympathetic. Each autonomic target
organ receives opposing sumpathetic and parasympathetic input. Sympathetic changes are indicative of
psychological arousal, whereas parasympathetic changes are indicative of psychological relaxation.
o Sympathetic nerves are autonomic motor nerves that project from the CNS in the lumbar and thoracic
regions of the spinal cord. Sympathetic neurons synapse on second-stage neurons at a substantial
distance from their target organs. Sympathetic nerves stimulate, organize and mobilize energy resources
in threatening situations.
o Parasympathetic nerves are autonomic motor nerves that project from the brain and sacral region of the
spinal cord. Parasympathetic neurons synapse near their target organs on very short second-stage
neurons. Parasympathetic nerves act to conserve energy.
Cranial Nerves: there are 12 pairs of cranial nerves which project from the brain (OOOTTAFAGVSH).
1. Olfactory: sensory - olfaction
2. Optic: sensory - vision
3. Occulomotor: motor, some sensory – eyelid movements, pupil constriction
4. Trochlear: motor, some sensory – superior oblique eye muscle (rolls your eyes)
5. Trigeminal: mixed (mainly sensory) has 3 Branches:
i. Opthalmic: sensory – from eye, forehead, top of head, upper eyelid
ii. Maxillary: sensory – nose, teeth, gums
iii. Mandibular: mixed – teeth sensations, moves jaw muscles
6. Abducens: motor, some sensory – lateral rectus muscle of the eye, eyelid movements
7. Facial: mixed – facial muscles (expressions), lip movements, glands of the head, tongue sensations (taste)
8. Auditory/Acoustic: sensory - hearing
9. Glossopharyngeal: mixed – tongue sensations (taste), pharynx movements (speech)
10.Vagus (longest nerves): mixed – parasympathetic motor innervations of most viscera – sensations from
11.Spinal Accessory: motor, some sensory – muscles of the neck and shoulders
12.Hypoglossal: motor, some sensory – muscles of the tongue
Meninges, Ventricles and Cerebrospinal Fluid
1. Dura mater (tough mother): tough membrane, outer meninx.
2. Arachnoid membrane (spiderweb-like membrane): middle meninx. Beneath it is a space called the subarachnoid
space which contains many large blood vessels and cerebrospinal fluid
3. Pia mater (pious mother):delicate, innermost meninx, which adheres to the surface of the CNS.
Cerebrospinal fluid: fills the subarachnoid space, the central canal of the spinal cord (small central channel that runs the
length of the spinal cord) and the cerebral ventricles of the brain (four large internal chambers of the brain: two lateral
ventricles and third and fourth ventricles) that are all interconnected and form one reservoir. The cerebrospinal fluid Psyc2410 – Chapter 3
supports and cushions the brain and is continuously produced by the choroid plexuses (networks of capillaries that
protrude into the ventricles from the pia mater). Excess cerebrospinal fluid is continuously absorbed from the subarachnoid
space into large blood filled spaces or dural sinuses, which run through the dura mater and drain into the large jugular veins
of the neck. The cerebral aqueduct connects the third and fourth ventricles.
The blood-brain barrier is a mechanism that impedes the passage of many toxic substances from the blood into the brain. In the
brain, the cells of the blood vessel walls are tightly packed, forming a barrier to the passage of many molecules, particularly proteins
and other large molecules. It doesn’t impede the passage of all large molecules, some that are critical for normal function are
actively transported through cerebral blood vessel walls and some blood vessel walls in some areas of the brain allow certain large
molecules to pass through.
3.2 Cells of the Nervous System
Anatomy of Neurons
Neurons – cell specialized for the reception, conduction and transmission of electrochemical signals. They come in a large variety of
shapes and sizes.
Neuron Cell Membrane: the membrane is a lipid bilayer and embedded in it are many protein molecules that are the basis
of many of the cell membrane’s functional properties. Ex: channel proteins, signal proteins.
Classes of Neurons:
Multipolar neuron: a neuron with more than two processes extending from its cell body (most common)
Unipolar neuron: neuron with one process extending from its cell body
Bipolar neuron: neuron with two processes extending from its cell body
Interneuron: neurons with short axons or no axons, they integrate the neural activity within a single brain
structure. They don’t conduct signals from one structure to another (some in spinal cord, reflex pathway).
Neurons and Neuroanatomical Structure: 2 kinds of gross neural structures in the NS…
Those composed primarily of cell bodies. CNS = nuclei. PNS = ganglia.
Those composed primarily of axons. CNS = tracts. PNS = nerves.
Glial Cells: The Forgotten Cells
Oligodendrocytes: glial cells with extensions that wrap around the axons of some neurons in the CNS. The extensions are
rich in myelin (fatty insulating substance), and the myelin sheaths they form increase the speed and efficiency of axonal
Schwann Cells: found only in the PNS. Individual Schwann cells wrap around neuron axons as myelin sheaths. Also increase
the speed of axonal conduction and also play a part in axonal regeneration after damage.
Microglia: smaller than other glial. They respond to injury or disease in the CNS my multiplying, engulfing cellular debris and
triggering inflammatory responses.
Astrocytes: largest glial cells and are named for their star shape. The extensions of some astrocytes cover the outer
surfaces of blood vessels that course through the brain; they also make contact with neuron cell bodies.
Play a role in allowing or blocking the passage of some chemicals from the blood into CNS neurons
Send and receive signals from neurons and other glial cells,
Control establishment and maintenance of synapses between neurons
Modulate neural activity
Maintain the function of axons
Participate in glial circuits Psyc2410 – Chapter 3
3.3 Neuroanatomical Techniques
Golgi Stain: by Camillo Golgi an Italian physician, 1870s. Silver chromate stains some neurons black, but not all of them, so
you can see the silhouette of their structures.
Nissl Stain: by Franz Nissl, German psychiatrist, 1880s. Uses Cresyl violet dye and other dyes. The dyes penetrate all cells on
a slide, but they bind effectively only to structures in neuron cell bodies, thus often used to estimate the number of cell
bodies in an area but counting the Nissl stained dots.
Electron Microscopy: provides details of neuronal structure. Done by coating thin slices of neural tissue with an electron-
absorbing substance that is taken up by different parts o