Nervous System: Coordination, Impulses, and Synapses
At the synapse, a neurotransmitter is released into the synaptic cleft and diffuses to the postsynaptic membrane. It then binds to specific receptors, which determines a potential change of the membrane (postsynaptic potential). If this potential reaches the threshold of excitation, it is propagated through the entire postsynaptic neuron. Once the neurotransmitter has acted, it is inactivated enzymatically, and the stimulation disappears.
Types of Synapses
Chemical Synapses
The arrival of the electrical
Read MoreHuman Reproduction: System, Fertilization, Pregnancy, and Delivery
Item 7: Human Reproductive System
Sexual Reproduction
Humans reproduce sexually. Women produce gametes called eggs, and men produce male gametes called sperm. These two cells combine to form a zygote.
Fertilization is internal; the sperm and egg bind within the female reproductive system. Humans are viviparous.
- Gamete Production: In specialized reproductive organs.
- Fertilization: The union of two gametes within the female reproductive tract, forming a single-celled zygote.
- Zygote Development: Within the
Nucleic Acids: Composition, Structure, and Function
Composition of Nucleic Acids
Nucleic acids are essential biological macromolecules responsible for storing, transmitting, and expressing genetic information in all living organisms. They include DNA and RNA, both of which are composed of nucleotides. Nucleotides consist of a nitrogenous base, a five-carbon sugar (pentose), and a phosphoric acid molecule.
Nitrogenous Bases
Nitrogenous bases are heterocyclic compounds containing carbon and nitrogen, with a flat structure. There are two types:
- Purines:
Human Digestive System: Functions, Anatomy, and Diseases
Digestive System Physiology
Gastrointestinal Tract Function
The gastrointestinal tract, a 10-12 meter tube with associated glands, digests food, transforming complex molecules into simple, usable substances for the body.
The Digestive Process
Digestion starts in the mouth where food mixes with saliva, is crushed by chewing, and formed into a bolus for swallowing.
Stomach Functions
The stomach, a muscular bag, secretes gastric juice, mixing food into chyme. This semi-fluid mass then passes to the duodenum.
Essential Biology Terms and Concepts for Students
Key Biological Terms
Abiotic: Non-living.
Aerobic: Biological processes occurring in the presence of oxygen.
Anaerobic: Biological processes occurring without oxygen.
Anabolism: Metabolic reactions synthesizing larger molecules from smaller ones, requiring energy.
DNA: Molecule containing genetic information, responsible for protein production and hereditary transmission.
Alleles: Alternative forms of a gene.
Amino Acids: Building blocks of proteins.
Antibody: Plasma protein synthesized by the immune system,
Read MoreHuman Circulatory, Endocrine, and Nervous Systems: An Overview
The Circulatory System
Function
The circulatory system is responsible for the transport of nutrients and oxygen to cells and the removal of waste substances.
Components
- Heart: A muscular pump that propels blood throughout the body. It is composed of three layers:
- Pericardium: The outer layer surrounding the heart.
- Myocardium: The thick middle layer responsible for the heart’s pumping action.
- Endocardium: The inner lining of the heart.
- Blood Vessels: Arteries, veins, and capillaries that transport blood.