Basic Neuroanatomy:Neuron Structure, Cell Soma, Cytoplasm, Nucleolus

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Neurological Basis of Behavior (PSY - 610)

Lesson25

Basic Neuroanatomy

Objectives:

The students will be familiarized with the functioning of the neurons and their components

· Systems, structure, Cells of the NS Neurons, Types of neurons, axonic and dendritic

communications,

· Neuronal conduction and functioning, ionic and electrophysiological properties,

· Localizing brain areas planes of reference (anterior-posterior etc).

· The Brain and the Peripheral systems: Brain: Forebrain, Mid brain, Hind Brain functioning of

each anatomical location in the CNS. Starting from the posterior located areas upto the

anterior-most. Cerebral Cortex: its layers, Corpus Callosum and the two hemispheres

Brain and spinal cord:

When we study the brain and the spinal cord we will first study the basics of neuroanatomical structure

and systems. The basic component, like all systems in the body is the cells. The building blocks which

the Nervous System is composed of are the neurons, the brains cells and the glial cells. There is also the

cerebrospinal fluid (CSF) which cleans and insulates the brain.

Neuron Structure

The neuron is like the other cells of the body but is specialized cell it is similar in structure and

composition of cell structures but then it differs in other characteristics.

The neuron comprises of three distinct parts as has already been described earlier. The Cell body or cell

soma, the axon (output end) and the dendrites,

Cell Soma

The Cell soma is made up of cytoplasm and contains the nucleus, the nucleolus, the free ribosomes

which are sites for ribonucleic proteins, the Rough endoplasmic reticulum and smooth endoplasmic

reticulum, Mitochondria and other bodies.

Cytoplasm: The jelly like semi fluid in which all the components of the cell float around in Nucleus.

The center the master mind of the cell which contains the genetic code, the DNA. It uses the DNA as a

template to manufacture the mRNA (messenger Ribonucleic acid), which carries the required

information to the Ribosome, where this is needed to manufacture structural proteins, and enzymes

needed for catalytic action within the cell.

Nucleolus: the structure within the nucleus which manufactures the ribosomes to carry the genetic code

outside the center, are manufactured.

Ribosomes: manufacture amino acids basics for proteins for use within the cell and for use outside

where they are transported via the Endoplasmic reticulum

Endoplasmic reticulum: There are two kinds found in the cell, the Smooth Endoplasmic Reticulum

(SER) and the Rough Endoplasmic Reticulum (RER). These are folds of membranes (like folds of

cloth). Both are for transporting material within and outside the cell. The RER's look rough because of

the beaded appearance, which is caused by the ribosomes being transported by RERs. The SER's

transport lipids

Golgi Apparatus: named after the discoverer Camillo Golgi, are where the membranes for vesicles are

prepared.

Neurological Basis of Behavior (PSY - 610)

Mitochondria: The power house of the cell. It provides energy needed to run the cell. Interestingly they

are the respiratory organs of the cell, and they are microorganisms which have survived within the cell

because of the evolutionary advantage to both the cell and the mitochondria. All metabolism of the cell

takes place in the Mitochondria.

Microfilaments and microtubules: supportive network of tubes and fine membrane filaments which

are continuously being formed and broken down as the cell changes learning requires cells shape and

form to change).

The Axon: The Axon is the output end of the cell. It emerges from the cell at the axonal hillock where

summation of messages takes place. It has neurotubules for supporting the shape and from form inside

and also providing a transport system. There are vesicles for carrying neurotransmitters, since axon is

involved in using a large amount of energy for transmitting messages, there is mitochondria floating

around in the axonal processes. Myelin Sheath covers the axon with gaps which are called Nodes of

Ranvier across which message jumps across. At the pre synaptic end the axon has synaptic boutons

which have vesicles and process the transmission using neurtransmitters.

Dendrites are the receiving ends of the neurons, they have multiple branches and there can be extensive

branching and synapses depending on the sites.

Cell membrane: is highly active cytoplasm where constantly ionic and electrical changes are taking

place. Further, complex biochemical processes are also taking place within the cell membrane. These

processes are important as they play an active role in

a) Transmission of signals through the axon to other neurons,

b) Biochemical processes of the soma and

c) Receiving of the transmission by the dendrites,

d) These processes also sustain and keep the cell alive and free of toxins,

e) Controls the number and amount of molecules leaving or entering the cell body

Cell membrane important because main role in

1) Conductance of signals along the axon,

2) Reception in the dendrite

3) control the molecules moving in and out of the cell The Intracellular membrane is composed of

double layer composed of fats and phosphates that is known as the phospholipid--These molecules

have 2 parts: hydrophobic (water repelling) tail, and hydrophilic ( water seeking) head. Fatty acid tail

inside and phosphate head outside. All the hydrophilic heads are on the outside facing the intracellular

and the extracellular medium which is made up of mainly water and other chemicals. These look like

little beads. The hydrophilic ends are towards the inside (like the bread in a three layer sandwich), and

they are retained where each layers lipid tails face each other. There are also some proteins

(glycoproteins), channel proteins, and cytoskeletal elements, which float around the layers, as these are

needed for any living organism. Within this there is a system of regulation of the movement of

molecules across the pores of the membrane

(Ref: Brown and Wallace, Rosenweig, Carlson, Pinel : figures p57-60)

References:

1. Kalat J.W (1998) Biological Psychology Brooks/ Cole Publishing

2. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston

3. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

4 Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd

edition) Worth Publishers New York

5. Bridgeman, B (1988) The Biology of Behaviour and Mind. John Wiley and Sons New York

6 Brown,T.S. and Wallace. (1980) P.M Physiological Psychology

Neurological Basis of Behavior (PSY - 610)

Academic Press New York

Note: References 2, 3, 4, 7 more closely followed in addition to the references cited in text.

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