Neurotransmitters and Hormonal Coordination in Animals
Neurotransmitters
Neurotransmitters are biomolecules synthesized by neurons and stored in small, concentrated vesicles within the axon terminals.
Nerve Reflex Pathways
A nerve pathway is the route followed by nerve impulses from their origin at a dendrite to another body area.
Reflex Arc
A reflex arc consists of:
- Receptors: Structures responsible for capturing a specific internal or external stimulus and transforming it into nerve impulses.
- Sensory Neuron: Conducts the nerve impulse from the receptor to
Cardiac Automaticity and Blood Circulation
Cardiac Automaticity
Some specialized cells in the heart can maintain a rhythmic beat automatically, without needing external signals from the body. This property is known as cardiac automaticity.
Cardiac Cycle (Heartbeat)
The cardiac cycle is an alternating sequence of contraction (systole) and relaxation (diastole) of the heart, which pumps blood from the veins to the arteries.
A cardiac cycle consists of the following stages:
- Atrial Diastole: Blood enters the atria through the pulmonary veins and
Anabolism and Photosynthesis: Processes of Building Life
Anabolism
The part of metabolism dedicated to constructing organic molecules from smaller, oxidized molecules.
Light-Dependent Reactions
These reactions capture light energy and convert it into chemical energy by synthesizing ATP and reduced pyridine nucleotides.
Chemiosmotic Photophosphorylation
ATP synthesis in chloroplasts, much like in mitochondria, is explained by Mitchell’s chemiosmotic hypothesis. Electron transport creates a proton gradient across the thylakoid membrane. Protons flowing back
Read MoreUnderstanding Phylogenetic Trees and Speciation
Phylogenetic Trees and Speciation
Understanding Phylogenetic Trees
A phylogenetic tree visually represents evolutionary relationships. Key components include:
- X-axis: Represents time.
- Red dots: Indicate new emerging traits within a species.
- Node: Marks the branch point where two species diverge (a splitting event).
- Lineage (orange): Shows a series of ancestor and descendant populations.
- Taxon: Any named group of organisms.
- Clade: A taxon including all evolutionary descendants of a common ancestor.
Types
Read MoreHuman Sensory System and Nervous System Overview
Human Sensory and Nervous Systems
Sensory System
Our senses allow us to gather information from both inside and outside our bodies, analyze it, and generate appropriate responses. This process involves:
- Perception: Sensory organs (eyes, ears, nose, tongue, skin) capture stimuli such as light, sound, taste, and pressure.
- Analysis: Stimuli are transmitted to the nervous system, where the central nervous system analyzes the information and decides on a reaction.
- Response: The body responds through the locomotor
Human Evolution and Genetics
Hominid Evolution
Around 1 to 2 million years ago, the first toolmaker, Homo habilis, appeared in East Africa, marking the dawn of humankind. Following Homo habilis, another hominid, Homo ergaster, emerged and migrated from Africa to Indonesia and China around 1.5 million years ago. This migration led to the evolution of Homo erectus, a hominid reaching heights of up to 1.80 meters, possessing a large head, a carnivorous diet, and mastery of fire. Homo erectus persisted until about 50,000 years
Read More