Human Sensory Receptors: Eye and Ear Anatomy and Function

Eye Receptors: The Sense of Sight

Most of the information that reaches your brain comes through your eyes. Of all the senses, sight is the most complex and often dominates the others.

Structure of the Eye

The eyes are the sensory organs where the receptors for light are located. They are fragile and protected by the bones of the skull, housed inside the orbits. Externally, the eyelids, eyelashes, and tears protect and clean the eyes, while eyebrows help keep sweat out.

  • Outer Layer: This consists of
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Lipids and Proteins: Structure, Types, and Functions

Lipids: Structure and Functions

Waxes

Waxes result from the esterification of a long-chain alcohol with a fatty acid. They primarily function to prevent dehydration.

Esterification Reaction Example:
CH3-(CH2)n-CH2OH + HOOC-(CH2)m-CH3 → CH3-(CH2)n-CH2-OOC-(CH2)m-CH3 (Wax) + H2O

An example is beeswax.

Unsaponifiable Lipids

These lipids cannot be hydrolyzed by saponification.

Steroids

Steroids are lipids derived from the cyclopentanoperhydrophenanthrene structure. Their structure consists of four fused carbon

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Mitochondria and Plastids: Structure and Cellular Roles

Mitochondria: Structure and Functions

Mitochondrial Structure

Mitochondrial Matrix

Contains a semi-liquid material with the consistency of a gel. It includes:

  • Mitochondrial DNA molecules: In most mammalian cells, this is circular, double-stranded DNA, distinct from nuclear DNA.
  • Mitochondrial RNA molecules.
  • Enzymes for mitochondrial DNA replication, transcription, and translation.
  • Enzymes involved in the Krebs cycle and the beta-oxidation of fatty acids.
  • Ions of Calcium (Ca), Phosphorus (P), and ribonucleoproteins.
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Nervous System, Sensory Receptors, and Human Senses

Coordination Systems

Coordination involves the nervous system and the endocrine system.

Neurons: Structure and Function

The nervous system uses independent cells called neurons. Key parts include:

  • Soma: The cell body.
  • Axon: A projection often surrounded by a myelin sheath.
  • Dendrites: Numerous extensions from the soma.

Sensory Receptors and Stimuli Transformation

Sensory receptors detect stimuli and transform them into electrical signals (nerve impulses).

Receptor Classification

  • Mechanoreceptors: Stimulated
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Body Coordination, Senses, and Blood Circulation

Coordination Centers: Nervous & Endocrine Systems

Processing Information: The coordination centers receive information sent by the receptors, process it, generate orders, and send them to the effector organs. The coordination centers are the nervous system, which is responsible for nervous coordination, and the endocrine system, which is responsible for endocrine coordination.

Nervous System

The nervous system is responsible for analyzing the internal and external stimuli perceived by the receptors,

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Human Biology Key Concepts: Nerves, Muscles, Systems

Nervous System Fundamentals

  • Information relay to muscles: Motor neurons relay information from the brain and spinal cord to muscles.
  • Neuron resting potential: Approximately -70 millivolts for most neurons.
  • Motor neuron conducting zone: Includes the axon.
  • Sodium-potassium pump mechanism: Moves ions across the neuron membrane via active transport.
  • Resting membrane potential definition: The voltage difference between the inside and outside of a neuron’s plasma membrane.
  • Action potential nature: An all-or-
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