Understanding Genetics, Human Genome, and Neurons
Nature Genetics
Genetics is the science that studies the mechanisms of heredity, as the traits passed from parent to child. The basic units of heredity are the genes that allow the continuity of species and determine that each individual has some distinctive features, unique and unrepeatable.
Each cell in the body contains 23 pairs of chromosomes, structures that are composed of DNA and determine your genotype or genetic inheritance. There are 22 pairs of chromosomes, not related to sex, and another pair of sex chromosomes called X and Y.
DNA is a molecule in a double helix linked by chemical bases: adenine, guanine, thymine, and cytosine. The sequence of these bases constitutes the genetic code.
Human Genome
The genome is the set of chromosomes of an organism with its corresponding genes. The genome of each species defines its capabilities: dolphins can do acrobatics on the water, bees can produce honey, and humans can reason.
Neurons and Their Messages
The nervous system is composed of two cell types: neurons and glial cells. Neurons are the basic cells of the nervous system, represent the anatomical and functional unit of the human brain, and are specialized for processing information. They have an outer membrane that allows the conduction of nerve impulses and communication between them through connections called synapses.
Composition of Neurons
Neurons are composed of a cell body and some extensions called axons and dendrites. Their function is to receive and broadcast signals.
- The cell body contains the nucleus, the storehouse of genetic information, and the organelles that synthesize ribonucleic acid and protein.
- Axon: An extension of the neuron, it conducts nerve impulses from the cell body to another neuron to the effector.
- Dendrites: Extensions of the cell body, they are divided like the branches of a tree and act as receptors of signals from other neurons.
Classification of Neurons
The classification of neurons is based on two criteria: structure and function.
Structural Classification
- Unipolar: Have a single extension. Characteristic of the nervous system.
- Bipolar: Have two extensions and many are sensory.
- Multipolar: Have an axon and many dendrites.
Functional Classification
- Sensory neurons: Send information from tissues into the spinal cord and brain.
- Motor neurons: Transmit information from the spinal cord to the muscles and glands.
- Interneurons: Collect and transmit stimuli to motor neurons.
Nerve Impulse
An electric wave is moving through the surface membrane of the neuron and its extensions, as if the neuron was a tiny battery capable of generating electricity.
Neuronal Synapses
It is the junction between two neurons that interact and exchange information or between neurons and muscle cells or glands. The synapse is made up of three elements: the presynaptic terminal, the postsynaptic cell, and the synaptic cleft.
- The electrical synapse: Results from the direct flow of current from the presynaptic to the postsynaptic neuron through channels connecting the cytoplasm of both cells.
- The chemical synapse: It is slower than electricity because the presynaptic neuron releases the neurotransmitter that passes to spread through the synaptic cleft and binds to receptors on after the postsynaptic cell membrane.
Neurotransmitters
Their mission is to communicate with each other neurons. The most important neurotransmitters are:
- Dopamine: Regulates motor activity and levels of responses in many parts of the brain.
- Serotonin: Plays a role in the regulation of moods, in the control of food intake, sleep, and pain regulation.
- Noradrenaline: Transmitter of sympathetic nerves of the ANS is involved in emergency response.
- Acetylcholine: Acts as a messenger at all joints between the motor neuron and muscle.