The Sensory System and Digestive Systems

Sensory System Overview

  • The sensory system enables the experience of the surrounding world.

Special Senses

  • Five Special Senses influence our interaction with the environment:

    • Balance

    • Hearing

    • Sight

    • Smell

    • Taste

  • Special sense organs transmit information to the brain.

General Senses

  • Five General Senses:

    • Touch

    • Pressure

    • Temperature

    • Pain

    • Proprioception

Proprioception

  • Proprioceptors are responsible for:

    • Sensing body orientation and equilibrium.

    • Allowing awareness of body position without visual cues.

    • Located in muscles, tendons, joints, and inner ear.

Types of Sensory Receptors

  • Five Types of Sensory Receptors:

    1. Nociceptors (pain receptors): Respond to tissue damage.

    2. Thermoreceptors: Respond to temperature changes.

    3. Mechanoreceptors: Respond to pressure/movement changes.

    4. Chemoreceptors: Respond to chemical changes (e.g., hydrogen ions for acid-base balance, taste, and smell).

    5. Photoreceptors: Respond to light (vision).

General Location of Sensory Receptors

  • Special senses receptors: Found in specific organs in the head.

  • General senses receptors: Widely distributed throughout skin, muscles, joints, and viscera.

Signals That Stimulate Pain

  • Three Specific Stimuli:

    • Tissue injury affecting chemoreceptors.

    • Oxygen deficiency due to ischemia.

    • Tissue stretching/deformation.

Four Components of Sensation

  • 1. Stimulus: Initiating event that triggers sensory response.

  • 2. Receptor: Specialized structure detecting stimulus.

  • 3. Sensory Nerve: Carries information to the brain.

  • 4. Brain: Processes the sensory information.

Sensation vs Perception

  • Sensation: Awareness of incoming sensory information, can be conscious or unconscious.

  • Perception: Conscious awareness of sensations (e.g., "ouch").

Sense of Smell

  • Anatomy:

    • Olfactory nerve: Carries signals from olfactory receptors in the nasal cavity to the brain.

    • Processes in the temporal lobe.

Sense of Taste

  • Characteristics:

    • Primary taste sensations include:

      • Sweet

      • Salty

      • Sour

      • Bitter

Sense of Hearing

  • Anatomy of the Ear:

    • External Ear: Auricle (pinna) and external auditory canal (collect sound).

    • Middle Ear: Contains Eustachian tube and three small bones (ossicles: malleus, incus, stapes).

    • Inner Ear: Contains cochlea, vestibule, semicircular canals, and cranial nerve VIII (transmit signals to the brain).

Sound Transmission

  • Middle Ear Structures:

    • Tympanic membrane (eardrum): Separates external and middle ear.

    • Auditory ossicles (malleus, incus, stapes): Transmit sound vibrations to the inner ear.

Inner Ear and Balance

  • Mechanoreceptors in the vestibule and semicircular canals:

    • Sense changes in body position.

    • Send messages via vestibular branch of cranial nerve VIII.

The Eye - Organ of Vision

  • Extraocular Structures:

    • Bony orbit protects the eye.

    • Eyebrows, eyelids, eyelashes protect from dust and injury.

    • Conjunctivae: Moisten the eyeball and protect.

The Lacrimal System

  • Components:

    • Lacrimal gland: Produces tear fluid.

    • Tear ducts: Drain tears from eyes.

    • Distributes and drains tears to maintain moisture in the eyes.

Muscles of the Eye

  • Control eye movement:

    • Include superior oblique, superior rectus, inferior rectus, and lateral rectus muscles.

Basic Structure of the Eyeball

  • Key components:

    • Lens, iris, cornea, sclera, retina, choroid, and various chambers (e.g., vitreous chamber).

Layers of the Eyeball

  • Three Layers:

    • Sclera: Tough outer layer that provides protection.

    • Cornea: Transparent tissue allowing light entry.

    • Choroid: Middle layer with blood vessels for nourishment.

    • Iris: Colored part determining pupil size and regulates light entry.

    • Ciliary Body: Secretes aqueous humor, aids in vision.

    • Retina: Inner layer with photoreceptors.

Lens of the Eye

  • Located behind the pupil, helps refract light for focusing on retina.

  • Adjusts shape for distance viewing.

Fluid in the Eye

  • Vitreous Humor: Gel-like substance maintaining retina health and eyeball shape.

  • Aqueous Humor: Liquid separating cornea from lens, providing nourishment.

Photoreceptors in Retina

  • Rods: Detect dim light; primarily for black and white vision.

  • Cones: Detect color; primarily found in the central retina.

Digestive System Overview

  • Key Organs:

    • Esophagus, stomach, intestines, liver, gallbladder, pancreas.

Functions of the Digestive System

  • Key Functions Include:

    • Ingesting food, digesting food, absorbing nutrients, and eliminating waste.

Gastrointestinal Tract Components

  • Gastrointestinal Tract Organs:

    • Mouth, esophagus, stomach, small intestine, large intestine, anus.

  • Accessory Organs:

    • Liver, gallbladder, pancreas.

Enteric Nervous System

  • Unique nervous network regulating GI function:

    • Autonomously controls digestion; influenced by the autonomic nervous system.

    • Described as the "second brain" due to its complexity.

Layers of the Digestive Tract Wall

  • Mucosa: Innermost layer aiding in digestion and absorption; contains glands.

  • Submucosa: Thickness for support; contains blood vessels and nerves.

  • Muscle Layer: Facilitates peristalsis and digestion; has circular and longitudinal muscles.

  • Serosa: Outer layer anchoring digestive organs; aids in infection control.

Structure of Digestive Tract Layers' Functions

  • Layers of digestive tract relate to specific functions:

    • Mucosa: Secretes mucus, enzymes, and hormones.

    • Serosa: Connects and nourishes organs.

    • Muscle Layer: Promotes mechanical digestion.

    • Submucosa: Supplies nutrients to mucosa.

Digestion Process Phases

  • Main Stages:

    1. Ingestion: Taking in food.

    2. Propulsion: Moving food through digestive tract (peristalsis).

    3. Mechanical Digestion: Physical breakdown (chewing, churning).

    4. Chemical Digestion: Enzymatic breakdown of food.

    5. Absorption: Nutrients entering blood and lymph vessels.

    6. Defecation: Elimination of waste.

Nutrients Needed by the Body

  • Essential Nutrients:

    • Include carbohydrates, fats, proteins, vitamins, and minerals.

Metabolic Processes

  • Metabolism Division:

    • Anabolism: Building complex substances from simpler ones.

    • Catabolism: Breaking down complex substances into simpler components.

Catabolic Enzymes

  • Digestive Enzymes:

    • Amylases break down polysaccharides.

    • Proteases breakdown proteins; work with bile in fat breakdown.

    • Lipases breakdown fats into fatty acids and glycerol.

Basal Metabolic Rate (BMR)

  • Concepts:

    • Define BMR, identify increasing and decreasing factors.