🎯 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 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 brain 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 🌿 (input end 📥).
🧫 Cell Soma (Cell Body)
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 🔬.
🧬 Key Components:
💧 Cytoplasm
The jelly-like semi fluid 💧 in which all the components of the cell float around 🌊.
🎯 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 🧫:
- Smooth Endoplasmic Reticulum (SER) 🧵: Transport lipids 🧈
- Rough Endoplasmic Reticulum (RER) 🧵🔬: 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 🚂.
These are folds of membranes 📋 (like folds of cloth 🧵). Both are for transporting material within and outside the cell 📦.
📦 Golgi Apparatus
Named after the discoverer Camillo Golgi 👨🔬, are where the membranes for vesicles are prepared 🏭.
⚡ 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: Output End
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 form inside 🏗️ and also providing a transport system 🚂
- Vesicles 🎒: For carrying neurotransmitters 🧪
- Mitochondria ⚡: 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 🏃
- Synaptic boutons 🎯: At the pre-synaptic end the axon has synaptic boutons which have vesicles 🎒 and process the transmission using neurotransmitters 🧪
🌿 Dendrites: Input End
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: The Active Boundary
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 🧫
- c) Receiving of transmission 📥: By the dendrites 🌿
- d) Cell maintenance 🧹: Sustain and keep the cell alive 💪 and free of toxins ☠️❌
- e) Molecular control 🎮: Controls the number and number of molecules leaving or entering the cell body 🧫
🧬 Cell Membrane Composition
Cell membrane important because main role in:
- Conductance of signals along the axon ⚡🔌
- Reception in the dendrite 📥🌿
- 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 🚫💧: Fatty acid tail inside ⬇️
- Hydrophilic (water seeking) head 💧✅: 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 layer's 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 🚪.
📚 References
- Kalat, J.W. (1998). Biological Psychology. Brooks/Cole Publishing Company.
- Carlson, N. R. (2005). Foundations of physiological psychology. Pearson Education New Zealand.
- Pinel, J. P. (2003). Biopsychology. (5th ed). Allyn & Bacon Singapore.
- Bloom, F., Nelson., & Lazerson. (2001), Behavioral Neuroscience: Brain, Mind and Behaviors. (3rd ed). Worth Publishers New York
- Bridgeman, B. (1988). The Biology of Behavior and Mind. John Wiley & Sons, New York
- Brown, T.S. & Wallace, P.S. (1980). Physiological Psychology. Academic Press, New York