Nervous & Endocrine Systems: Coordination and Control
Coordination Systems
Nervous System
Composed of nerve tissue, it prepares rapid, short-lasting responses. It acts through nerve impulses propagating along nerves.
Endocrine System
Composed of endocrine glands, it prepares slow, but durable responses. It acts through chemical messengers called hormones that travel through the blood to target cells or organs.
Elements of Coordination
Receptor
A structure that perceives stimuli and transmits them to nerve centers. Sensory organs are receptors that pick up
Read MoreVision and Hearing: A Biological Overview
Vision
Pupil Dilation
At night, the pupil dilates. During the day, the pupil contracts.
Insects can see ultraviolet light. Snakes can see infrared light.
Vision Impairment
Night blindness: Difficulty seeing at night due to a Vitamin A (retinal) deficiency.
Eye Structure and Function
Cornea: Allows light to enter the eye.
Anterior chamber (aqueous humor): Nourishes the cells of the cornea.
Pupil: The opening through which light enters and exits.
Iris: Contains two muscles that adjust the pupil’s size.
Lens:
Read MoreBrain Structure and Function: A Comprehensive Overview
Brain Structure and Function
Anatomical Overview
Divisions of the Brain
The brain is divided by anatomical planes: sagittal (hemispheres), coronal (lobes), and horizontal (top and bottom).
Key components include:
- Gray matter: Intracellular communication
- White matter: Long-distance transmission of messages via myelin
- Cerebrospinal fluid (CSF): Surrounds, protects, nourishes, and communicates within the CNS; produced in the lateral ventricles
- Meninges: Protective layers covering the brain, including the dura
Life Cycle of Plants: Sexual & Asexual Reproduction
Life Cycle of Plants
Sexual Reproduction
Plants are formed from the union of two specialized cells called gametes during fertilization to create a zygote.
Advantages:
- Genetic diversity through recombination.
- Different genotypes in each generation.
Asexual Reproduction
New plants develop from one or more cells of a progenitor plant.
Disadvantage:
- Produces clones with identical genotypes to the parent.
Advantage:
- Faster reproduction requiring only one individual.
- Effective colonization.
Haploid and Diploid Phases
Haploid
Read MoreViruses, Cellular Structures, and Processes
Viruses
Viruses originate in aquatic environments and can associate with particular ways of life. They are free, evolving entities that survive by becoming parasites. Essentially, they are organisms that have lost their cellular machinery through adaptation to parasitism or are genetic fragments detached from cellular organisms. Their specificity lies in their nucleic acid, which allows them to parasitize cells.
Each virion consists of a nucleic acid (DNA or RNA, never both simultaneously), a capsid
Read MoreHuman Biology: A Comprehensive Overview of Organ Systems
Human Biology
Circulatory System
Arteries
Structure: Arteries have thick, slightly elastic walls to withstand high pressure from the heart’s pumping action.
Function: Arteries carry oxygenated, nutrient-rich blood away from the heart. Muscle contractions in artery walls regulate blood flow to organs.
Veins
Structure: Veins have thinner walls and one-way valves to prevent backflow.
Function: Veins return deoxygenated blood carrying cellular waste to the heart. Muscle contractions also control blood volume.
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