Anatomy and Physiology Chapter 11 Lecture Notes

Special Senses and Sensory Receptors

• Sensory receptors are sensitive to different types of stimuli.
• Simplest receptors are dendrites of sensory neurons.
• Receptors monitor internal and external conditions.
  • Examples: thermoreceptors, mechanoreceptors (touch).
• Specialized receptor cells respond to specific stimuli.
  • Examples: rods and cones (vision), olfactory receptors (smell), hearing cells (cochlea), gustatory cells (taste).

Receptive Field

• Smaller field = more precise.
• Larger field = less precise.

Sensation vs. Perception

• Sensation: detecting the stimulus.
  • Sensory information comes in, receptors recognize stimulus, signal is conducted.
• Conduction:
  • Movement of action potentials to the cerebral cortex.
• Cerebral cortex: conscious awareness of sensory information, integration area for deciding what to do.

Adaptation

• Stimuli/sensations are typically adaptable.
  • Example: jumping into a pool feels less cold over time.
• Most senses adapt (becoming less aware of sensory information).
• Pain has poor adaptation.
  • Pain doesn't stop until the problem is fixed.
• Adaptation can be problematic (e.g., factory workers forgetting a machine is running).
  • Safety mechanisms are put in place.

Special Senses vs. General Senses

• Special senses: located only in the head.
  • Sight (vision, eyes).
  • Hearing (ears).
  • Smell (olfaction, nose).
  • Balance/equilibrium (vestibulocochlear nerve, inner ear).
  • Taste (gustation, tongue).
• General senses: found throughout the body.
  • Temperature (thermoreceptors).
  • Touch (mechanoreceptors).
  • Proprioception (joints).
  • Nociception (pain).

Testing Knowledge

• Pressure: general sense (all over the body).
• Vision: special sense (head only).
• Equilibrium/balance: special sense (head only, vestibule in inner ear).
• Gustation/taste: special sense (head only, oral cavity).
• Proprioception: general sense (all over the body, joints).
• Pain: general sense (all over the body).
• Olfaction/smell: special sense (head only, nose).
• Hearing: special sense (head).
• Temperature: general sense (all over the body).
• Vibration: general sense (all over the body).
• Touch: general sense (mechanoreceptors all over the body).

Cranial Nerves and Senses

• Cranial nerve I: olfaction (olfactory nerve).
• Cranial nerves VII and IX: gustation/taste (facial and glossopharyngeal nerves).
• Cranial nerve II: vision (optic nerve).
• Cranial nerve VIII: hearing (vestibulocochlear nerve, cochlear branch).

General Senses

• Distributed throughout the body.
• Include pain, temperature, touch, pressure, vibration, proprioception.
• Proprioception: body's position in space, limb control, sense of effort, weight determination.

Structures of the Eye

• Iris: colored portion, controls pupil diameter.
• Pupil: opening in the iris, dilates/constricts.
  • Dilation: sympathetic nervous system.
  • Constriction: parasympathetic nervous system.
• Eyelids: superior and inferior.
• Sclera: white of the eye, part of the fibrous tunic.

Light and Vision

• Reflection vs. refraction.
• White light: contains all colors of the electromagnetic spectrum (ROYGBIV).
• Color appearance: color you see is being reflected, not absorbed.
• Light from sun hits apple -> apple appears green.
  • All colors are absorbed except green, which is reflected.
• Green light wave enters the eye.
• Cornea: clear portion of the eye.
• Pupil: opening for light to pass through.
• Lens: refracts (bends) the light.
  • Focuses light on the retina.
  • Image upside down, fixed by visual cortex.
• Optic nerve: leaves the eye.
• Optic chiasm, optic tract -> thalamus -> visual cortex.
• Thalamus: relay station (sensory information from spinal cord, eyes, ears).
  • Sends information to the correct region of the cerebral cortex.

Eye Cavities

• Anterior cavity:
  • Two chambers:
    • Anterior chamber.
    • Posterior chamber.
  • Aqueous humor (watery fluid).
• Posterior cavity:
  • Vitreous humor (thick, viscous).
  • Maintains retinal contact with choroid (vascular), ensuring oxygen and nutrient supply.

Glaucoma

• Increased pressure within the eye.
• Can damage retina.
• Retina contains photoreceptors (rods and cones).

Eye Structures and Light Entry

• Superior/inferior eyelid.
• Light passes through cornea (clear region of fibrous tunic).
• Aqueous humor in anterior cavity.
• Pupil: opening surrounded by iris (colored part).
• Lens: refracts light; focuses it on the retina.
• Posterior cavity: vitreous humor (thick, jelly-like).
• Retina: contains photoreceptors (rods, cones).
• Choroid: vascular.
• Sclera: white of the eye, extrinsic eye muscle attachment.
• Optic nerve.
• Optic disc (blind spot): no photoreceptors, entrance/exit of blood vessels and optic nerve.
• Fovea/fovea centralis: light focused here when reading, driving; high concentration of cones.

Layers of the Eye

• Sclera.
  • Attachment point for superior rectus muscle (extrinsic eye muscle).
• Choroid.
  • Vascular (blood supply).
• Retina.
  • Nervous tunic (photoreceptors).

Limbus

• Junction between cornea and sclera.

Macula and Fovea

• Macula : central region of retina.
• Fovea centralis at the center macula: high concentration of cones.

Ocular Health

• Diabetic retinopathy: high blood glucose damages retinal blood vessels, leading to blindness.

Key Structures Recap

• Cornea: clear region for light entry.
• Aqueous humor: liquid in anterior cavity.
• Pupil: portal for light entry.
• Iris: surrounds pupil.
• Lens.
• Ciliary body: adjusts lens shape.
• Suspensory ligaments.
• Lacrimal gland: secretes tears.
• Vitreous humor: viscous fluid.
• Retina: contains photoreceptors.
• Choroid: vascular.
• Sclera: white of the eye, part of fibrous tunic.
• Optic nerve.

Tunics of the Eye

• Fibrous tunic: most superficial.
  • Sclera.
  • Cornea.
• Vascular tunic: middle layer.
  • Choroid.
  • Ciliary body.
  • Iris.
• Nervous tunic: deepest layer.
  • Retina.

Extrinsic Eye Muscles

• Four rectus muscles: superior, inferior, medial, lateral.
• Two oblique muscles: superior, inferior.
• Attached to the sclera.

Innervation of Extrinsic Eye Muscles

• Oculomotor nerve (III): innervates four of six muscles (not superior oblique, lateral rectus).
• Trochlear nerve (IV): innervates superior oblique.
• Abducens nerve (VI): innervates lateral rectus.

Functions of the Fibrous Tunic

• Cornea: clear, allows light to enter.
• Sclera: white of the eye.
  • Attachment for extrinsic eye muscles.
  • Provides support and shape.

Vascular Layer Components

• Choroid: blood vessels, oxygen/nutrient supply.
• Ciliary body: attached to lens, changes shape.
• Iris: adjusts pupil size for light control.

Pupil and Iris Function

• Pupil: opening.
• Iris: colored portion, pupillary muscles control pupil diameter.
• Ciliary body: attached to suspensory ligaments, changes lens shape.
• Choroid: vascular, provides oxygen and nutrients to retina.

Nervous Tunic

• Retina: contains photoreceptors.
  • 6,000,000 cones (color vision).
  • 100,000,000 rods (dim light vision).
• Cones: color vision.
• Rods: dim light (night vision).
• Macula luteae: high concentration of cones, sharpest vision.
• Fovea centralis: center of macula luteae with even higher cone concentration.

Layers of Retina

• Inner layer: mostly nervous cells (ganglion, amacrine, bipolar, horizontal).
• Outer layer: pigmented epithelium, absorbs excess light.

Processes

• Light passes through all retinal cells before hitting rods/cones.
• Action potential goes towards optic nerve.
• Pigmented epithelium absorbs excess light.

Visual Pathway

• Light enters eyes, information crosses at optic chiasm.
• Right visual field -> left cerebral hemisphere.
• Left visual field -> right cerebral hemisphere.
• Optic nerves -> optic chiasm -> optic tracts -> thalamus (lateral geniculate nucleus) -> visual cortex (occipital lobe).
• Contralateral processing: left is processed by the right, and the right is processed by the left.

Eye Tests

• Snellen eye chart: assesses visual acuity.
  • 20/20: normal vision.
  • < 20/20: better than average vision.
  • > 20/20: worse than average vision.
• Astigmatism: misshapen cornea or lens leads to multiple focal points.

Checking Pupils with a Penlight - PERRLA Assessment

• Assessing Neuro Status and Cranial Nerve Function

Key Tools and Initial Observations

• Using a Penlight with Pupil Size Gauge
  • A quality penlight is essential for accurate pupil assessment.
  • Look for one with a gauge to measure pupil size in millimeters.
• Normal Pupil Size: 3-5 mm

Direct and Consensual Responses

Assessment Steps

1. Dim the Lights: Create an environment conducive to observing pupil reflexes.

2. Direct Response

   1. Shine the Light: Focus the penlight on one eye and watch for constriction.
   2. Observe Constriction: Evaluate how quickly and effectively the pupil constricts.

3. Consensual Response

   1. Observe Opposite Eye: Check for simultaneous constriction in the other eye while shining light in the first.
   2. Simultaneous Reaction: Both pupils should constrict together.

4. Swinging Test (Optional): Alternate light between both eyes every few seconds to assess pupil response and symmetry. Observe any abnormal reactions or disparities.

Accommodation

Assessment Details

1. Patient Fixation: Have the patient focus on an object (finger or pen) at a distance.
2. Move Object Closer: Slowly bring the object towards the patient's face, observing eye movement.
3. Pupil Constriction: Note if the pupils constrict and fixate on the object as it moves closer.

Documentation

Using PERRLA

• Pupils Equal: Check that pupil sizes are similar.
• Round: Pupils should be circular in shape.
• Reactive to Light: Pupils constrict when exposed to light.
• Accommodation: Pupils adjust focus as objects move closer.

Key Concepts

• Pupil size: Normal pupil size ranges from 3 to 5 mm.
• Direct response: Constriction of the pupil when light is directly shone into the eye.
• Consensual response: Simultaneous constriction of the other pupil when light is shone into one eye.
• Accommodation: Adjustment of the eyes to focus on objects at varying distances.
• PERRLA: Acronym to document pupils as Equal, Round, Reactive to Light, and Accommodating.

Major Steps

1. Assess Roundness and Equal Size: Examine pupils for shape and size symmetry.
2. Check Direct Response: Shine light in one eye and assess constriction.
3. Evaluate Consensual Response: Observe the other eye for simultaneous constriction.
4. Conduct Accommodation Test: Have patient focus on an object as you move it closer, checking pupil adjustment.
5. Document Findings Using PERRLA: Record pupils as Equal, Round, Reactive to Light, and Accommodating.

Key Considerations

• Practice Coordination: Coordinate your movements and observations for smooth transitions.
• Maintain Communication: Explain each step to the patient for comfort and clarity.
• Document Accurately

Eye vs. Camera - Comparing Optical Systems

Fundamental Similarities

• Both Feature Lenses: To focus light and create a clear image on a sensor.
• Both Employ Sensors: To capture the focused light and convert it into signals.

Divergences in Behavior and Structure

Lens Mechanics

• Camera Lenses: Achromatic for uniform focus of all colors.
• Human Eye Lenses: Selective focus leading to slight chromatic aberrations.

Photoreceptor Setup

• Camera's Single Photoreceptor Type
  • Even Distribution: Uniform arrangement across the sensor.
  • Color Filtering: Utilizes red, green, and blue filters for selective wavelength capture.
• The Human Eye's Diverse Photoreceptor Types
  • Multiple Types: Three types for normal conditions and one for low light.
  • Uneven Distribution
    • No Receptors in Blind Spot
    • No or Few Blue Light Receptors in Center
  • Colorblindness in Low Light

Brain-Driven Visual Processing

• Visual Illusions Result
• Active Filling of Visual Gaps

Continuous Jiggling Movement

• Prevents Vision Shutdown: Needed to stimulate retinal nerves due to photoreceptor fatigue.
• Suppression of Movement Detection
• Movement-Free Image

Functional Advantages in Optical Systems

Video Cameras

• Detailed Image Capture.
• Long-Distance Magnification.
• Accurate Recordings.

Human Eyes

• Evolved for Efficiency.
• Visual Filling to Overlook Details.

Eye Surgery - Lens Replacement

Overview

• Correcting Vision Issues Through Surgery

Key Points

1. Natural Lens Clouding
2. Main Steps in the Surgical Process
3. Recovery and Follow-Up

Structures of the Ear

• Oracle/Pinna:
  • Collects and funnels sound towards the auditory canal.
• Auditory Canal/External Acoustic Meatus:
  • Funnel sounds toward the tympanic membrane.
• Tympanic Membrane:
  • Vibrates in response to sound waves.
• Auditory Ossicles (Malleus, Incus, Stapes):
  • Amplify vibrations from the tympanic membrane.
• Oval Window:
  • Connects to the cochlea and transmits vibrations.
• Eustachian Tube/Auditory Tube:
  • Equalizes pressure in the middle ear with the external environment.
• Inner Ear (Vestibule, Semicircular Canals, Cochlea):

Names

• Eustachian tube is also known as auditory tube or pharyngotympanic tube.

Sound Waves & Cochlea Function

Mechanical to Fluid Vibrations: Key Steps

1. Sound waves collected: Oracle/Pinna. Sound is funneled to the Auditory Canal.
2. Tympanic Membrane Vibration: Initiates the ossicle movement.
3. Ossicle Amplification: Malleus, Incus, & Stapes vibration amplifies the Ossiciles and Transfers force to next step.
4. Pressure on the Oval Window: Fluid movement in inner ear initiates signal transmission.
5. Fluid Dynamics: Vestibular/Tympanic duct fluid movement. Cochlear duct involvement activates hair cells.
   Hair Cell Activation: Movement creates action potentials. Vestibulocochlear nerves transmit signals to CNS.

Sound Waves Pathway - Cochlea Overview

Sound Wave Collection -> Action Potential Generation

1. Vibrations in Auditory Canal: Sound waves funnel down to the thin Tympanic Membrane.
2. Tympanic Membrane Response: The collected sound waves make the disk like membrane vibrate.
3. Amplification through Ossicles: Amplify through the middle ear bones: Malleus, Incus, & Stapes.
4. Vibration Transmission: Transfer through the Oval Window into the inner ear.

Amplification/Damage -> Signal Relay and Result

Brain Dynamics: Auditory cortex processes data. Temporal lobe integrates sound perception finally.

The Auditory System - Ear/Brain Dynamics

1. Sound Waves to Fluid Waves Conversion: Fluid vibration within the cochlea.
2. Tympanic Membrane Mechanics: Converts waves into bone action through a thin membrane.
3. Bone Interactions and Fluid Motion: Hammer-Anvil-Stirrup action transfers vibrations.
4. Basilar Membrane: Inner hair cells (vibration sensors) are activated.

Hearing - Cochlear Mechanics

• Short WL, High Freq: Stiffness (bass). Vibration near round window end
• Long WL, Low Freq: Flexibility (soprano). Vibration near oval window end.

Sound Location Processing within The Brain.

Signal Transmission

• Temporal Variations Analyzed: Microsecond differentials.
• Intensity Differences Noted: Sound pressure and intensity as clues.
• Auditory Cortex Synthesis: Delivers the sound direction results.

Innervation of Ear Structures

• Cochlear Nerve.: Auditory sensation.
• Vestibular Nerve: Balance/spatial input.
• Target Brainstem, Thalamus then The Auditory Cortex.

Ear Anatomy Review

Oracle (pinna): Gathers sound.
Auditory canal: Channels sound
Tympanic membrane: Sound vibration
Malleus, incus, stapes: Sound amplification
Eustachian tube: Pressure stabilization
Cochlear nerve: Hearing
Vestibular nerve: Balance and equilibrium
Semicircular canals: Head rotation sensing
Cochlea: Sound processing (frequency and amplitude)

Olfaction Overview

Structures Involved

• Olfactory Epithelium location is in the the Superior Nasal Cavity
• Cribriform Plate of the Ethmoid Bone serves a purpose in what to do with receptors

Physiological Elements

• Odorants must Vaporize for nasal passageway
• Receptor Cells detect odorants and what is done.
• Supporting Cells assist
• Basal Stem Cells produce receptors

Glandular and Cellular Functions

• Bowman's Glands create mucus to humidify odorants
  Cell permeability changes allow for potential through action.

Neural Path for the Ethmoid Bone Plate and Nerves

• The receptors connect to the olfactory bulb, then the cribriform plate, and then connect.
  -Through Bony Openings within the Plate and Receptor Nerves in the Olfactory Epithelium
  -Odorants reach and connect within Action Potentials
  -Axons and Nerves connect to the Olfactory Nerve from within The Olfactory Bulb
  -Mitral Cells form the Olfactory Tract Alphabetize, Bulb Tract.

Olfactory Processes - Pharynx and Nasal Dynamic

• Air Inhalation carries The Incoming Signals
• Bowman's Cells keep things lubricated.
• Nasal Passageway opens to all the pharynx regions: Naso-, Oro-, Laryngopharynx.

Structure Labeling and Function Review

*Nasal Passages: Incoming Signals ArriveHere. Cribriform Plate is where ethmoid bone openings are found.
*Olfactory Nerves send to Nerve Fibers via Plate
*Olfactory Bulb collects, processes, and then relays to the brain and action pathway

Anatomy of Gustation - Taste

• Papillae: Circumvallate type- taste bud heavy, Folate type-, Fungiform type- mushroom like are the found locations.
  Oral Cavity soft palate of Pharynx area plays a part.

The Taste Mechanics

Chemoreceptors: Key to Chemicals in food analysis. Taste buds for chemical to saliva connection.
Papillae Variety of Taste Buds as noted earlier plays a part.

Taste Pathway Summary

1. Taste Chemistry: Saliva dissolves chemicals for taste pores to conduct.
2. Receptor Excitation creates action potentials; relayed to the brain for interpretation
3. Texture, Smell, and Experience add complexity.

Nerve Function and Taste Signal Relay Dynamics.

Taste Nerve Review: Hypoglossal vs, Facial, Glossopharyngeal, Vagus all affect signals and senses.
Taste and The Hypoglossal Nerve exclusion makes the other taste nerve groups affect sensory output.

Nerves, Tongue Location and Related Reflexes: Facia is the anterior, Glossopharyngeal Nerve is posterior, and reflexes related with Vagus for swallowing and cough.

Key Points about Nerves and Location of The Tongue
Facial (Anterior),Glossopharyngeal (Posterior), Vagus for Swallowing/Cough- Reflex.

Taste Nerve Breakdown Summary

-Facial [VII]: Anterior two-thirds -Face.
-GlossopharyngeaL[IX]: Posterior one-third- Swallowing.
Vagus [X]: Throat. Cough, Swallowing.
Motor/Mix for All. The nerves here all share some Motor and Sensory Functions. Except for the Hypo-Glossal Nerve system, which is only in the Moto Format. And, what all the listed nerves do is mixed.

The Science of Spice: More Than Just Taste

Spiciness Isn't a Taste

• Activating Heat Receptors: Spicy compounds trigger polymodal nociceptors, resulting in the sensation of heat
  Sensing Heat: Our brains read a 'spicy' as heat, causing symptoms such as stress of heat and pain.

• Contrasting Sensations example, menthol activates cold receptors.
  Heat Response Mechanism is the Fight or Flight action.

Spicy Molecules and Perceived Sensations

Reaching the Senses: Capsaicin(found in peppers) is delivered to the mouth and Piperine (black pepper ) for hot flavor result
Isothiocyanates make mustards and the Wasabi hot- volatile vapors (wasabi)

Scoville Scale for Units
0 Scoville Heat Units (Bell Pepper)-> to up to the the race to reach the 1. 5 M Scoville unit score on scale. And, Half the scoville units as Pepper Spray.

Cultural, Historical, and Biological Factors

Humans Embrace Spicy Food for antibacterial to adrenaline to genetic.
Those who like spice find it as thrilling as roller coasters and other risky behavior.
Spicy Tolerance and How to Train Yourself. the sensation as a burn will never dull. You only toughen up. Your only becoming tougher. In Fact- The pain factor will never reduce, you only become tougher and grow to deal with the feeling and results from spicy food..