ORGANIZATIONAL PLAN
Overview of Topics
Lesson Objectives
Basic Directions
Terms & Directions
Basic Divisions of CNS
Brain Size
Brain Development
3 Brain Divisions
Related Factors
Learning Objectives
- Describe the basic directions used in neuroscience.
- Explain the differences between brain sections through the sagittal, coronal, and transverse plane.
- Outline the basic divisions of the nervous system.
- Outline the basic divisions of the brain and discuss the basic functions associated with each.
- Describe the organization of the nerves in the PNS and explain how the different types of connective tissue are associated with their organization.
The first factor for consideration involved understanding the directions used in identifying structures
in the nervous system. The basic directions provided below are for 4-legged animals. Since the human
stands upright, the head is bent forward. Once you learn the directions for the dog, simply remember that,
in the human, anterior still refers to the front of the brain and dorsal the base (just as in the dog).
Basic Directions (first consider a dog)
Anterior (rostral) - toward the nose
Posterior (caudal) - toward the tail
Dorsal - toward the back
Ventral - toward the front
Superior - above
Inferior - below
Lateral - toward the side
Medial - toward the center
Proximal - toward the trunk or point of origin.
Distal - toward the periphery or away from origin.
The terms below relate to the relationship between central nervous system (CNS) areas and peripheral
nervous system (PNS) effects. Remember that all input and output to the cortex is contralateral. Thus,
the left side of the brain receives information from the right periphery; and, likewise, the left side of the
brain controls muscles on the right side of the body.
Ipsilateral - on the same side
Contralateral - on the opposite side
Brain Sections
Sagittal plane - sections cut anterior to posterior
Coronal plane - sections cut from side to side
Transverse or horizontal plane - as seen looking down from above.
Other Terms:
Nerve - a group of fibers in the PNS surrounded by connective tissue.
Tract - a group of fibers in the CNS surrounded by supporting cells.
Nucleus - a group of cell bodies in the CNS.
Ganglion - a group of cell bodies in the PNS
Lamina - a band of fibers or cell bodies in the CNS
Lemniscus - a tape or band of fibers in the CNS
Column or horn - a collection of fibers in the CNS
Gyrus - raised fold on the cortex
Sulcus - indention between folds in the cortex
Fissure - deeper and/or longer sulcus
Brain Size:
400 grams at birth.
850 grams at 11 months.
1450 grams at maturity.
400 grams in great apes.
850 grams in Java man
1100 grams in Peking man
Neanderthal & Cro-Magnon slightly larger than modern humans.
Gifted no larger than others
Brain size relates to body size
Dolfins have larger brains to body size.
Neurons:
150 billion neurons.
50 billion directly engaged in information processing.
Each receive 15,000 connections with other cells.
All neurons evolve from neuroblasts (primitive cells capable of cell division).
Development of the Brain:
Begins as neural groove.
Develops into neural tube.
Alar plate - sensory.
Baslar Plate - motor.
Basic Divisions of the Nervous System
The major divisions are between the Central and Peripheral Nervous System
|
NERVOUS SYSTEM |
|
| Central Nervous System |
|
Peripheral Nervous System |
| Spinal Cord |
|
Somatic Division |
| Brain |
|
Autonomic Division |
The somatic division of the PNS consists of all the nerves relaying information from and to the periphery.
The autonomic division is divided into the parasympathetic division which functions to restore and replenish the body and the sympathetic division which functions to prepare the body to deal with the environment in a vigorous manner (such as with emotion and/or motivation).
Three Divisions of the Brain
Prosencephalon (Forebrain)
Telencephalon
Cerebrum (cortex)
Corpus Callosum
Basal Ganglia
Limbic System
Olfactory Bulb
Lateral Ventricles
Diencephalon
Thalamus
Epithalamus
Hypothalamus
Pineal Body
Third Ventricle
Mesencephalon (Midbrain)
Tectum
Tegmentum
Cerebral aqueduct
Rhombencephalon (Hindbrain)
Cerebellum
Pons
Medulla
Fourth Ventricle
The major divisions of the nervous system are the PNS and CNS. Our nervous system is centralized:
meaning that; in order to respond to a stimulus, the signal must be relayed into the spinal cord where other
neurons return to the muscles to produce a response. This type of response would be a reflex, and it
usually involves a sensory, connecting, and motor neuron.
Most of the focus of this course is on the CNS where many more neurons are involved. The same
general concept of centralization still applies. The best method for understanding how the nervous system
functions is to consider the sequence of events necessary to respond to a stimulus. A stimulus is detected
by a receptor, is relayed to the spinal cord, goes up the spinal cord to the brain where it is processed, and a
signal is sent from the brain, down the spinal cord to the motor neuron, and out to the muscle for a
response. It can be conceptualized as a linear system, and this model will be explained in detail in the
second section of this course dealing with functional systems of the nervous system.
One major difference in the peripheral nervous system relates to the protection provided by connective tissue.
Endoneurium --- Each axon is surrounded by a very delicate connective tissue the endoneurium.
Perineurium --- Groups of neurons (both sensory and motor) are then grouped and surrounded by a thicker connective tissue the perineruium to make up fasicles.
Epineurium --- Finally, groups of fassicles are surrounded by a thick connective tissue the epineruium.
Terms to Know
| anterior |
posterior |
rostral |
| caudal |
dorsal |
ventral |
| superior |
lateral |
medial |
| proximal |
distal |
sagittal plane |
| coronal plane |
horizontal plane |
nerve |
| tract |
nucleus |
ganglion |
| lamina |
lemniscus |
gyrus |
| sulcus |
corpus callosum |
basal ganglia |
| cerebrum |
diencephalon |
midbrain |
| hindbrain |
endoneurium |
perineurium |
| epineurium |
thalamus |
hypothalamus |
| column or horn |
ipsilaeral |
contralateral |
Links to Associated Areas
