Practical 6: Sensory Receptors and Perception

Sensory Receptors

Specialised cells or structures that respond to specific types of physical energy and convey information to the brain.

Five Senses

Sight, hearing, taste, smell, touch.

Additional Sensory Modalities

Includes temperature, pain, vibration, proprioception.

Adaptation

Sensory system's insensitivity to constant stimulation.

Nociceptors

Pain receptors that do not adapt to continued stimulation and are responsible for signaling pain from various types of tissue damage or injury.

Visual Spectrum

Electromagnetic range visible to humans, 380-750 nm.

Cones

Retinal cells for color differentiation.

Rods

Retinal cells for light and dark contrast.

Fovea

Region of highest visual acuity in the retina.

Blind Spot

Optic disc area devoid of receptors.

Color Vision

Perception based on cone sensor excitation.

Accommodation

Eye's ability to change focus for distance.

Electromagnetic Energy

Energy detected by visual sensory receptors.

Photo Receptive Cells

Cells in the eye that detect light.

Infrared Detection

Ability to sense body heat by some snakes.

Ultraviolet Vision

Some insects can see beyond human capability.

Peak Sensitivity

Wavelengths where cones are most responsive.

Visual Acuity

Clarity or sharpness of vision.

Retina

Layer of photoreceptors at the back of the eye.

Stimulus Transduction

Conversion of physical energy into neural signals.

Neurotransmitters

Chemicals released by receptors to activate neurons.

Tactile Receptors

Skin receptors that adapt quickly to stimuli.

Acetaminophen

Medication used to interrupt pain signals.

Near Point

Closest distance for clear vision of an object.

Diopter

Unit measuring lens power, equal to 1/m.

Optic Disc

Region where optic nerve exits the eye.

Color Blindness

Inability to distinguish certain colors.

Achromatopsia

Severe color blindness; sees only gray shades.

X-linked Recessive

Genetic trait often inherited through X chromosome.

Visual Field

Total area visible when looking straight ahead.

Focal Length

Distance from lens to focus point.

Nystagmus

Involuntary eye movement, often jerky.

Accommodation Power

Measured in diopters; varies with age.

Retinal Blood Vessels

Supply blood to the retina, emerge at optic disc.

Lazy Eye

Condition where one eye fails to achieve normal vision.

Pen Test

Experiment to measure blind spot and visual field.

Color-Sensing Granules

Pigments in cones that detect color.

Irregular Margins

Uneven edges of the blind spot outline.

Measurement Technique

Using a tailor's tape for distance measurement.

Visual Focus Mechanisms

Three processes for adjusting focus on objects.

Protanopia

Complete red cone deficiency affecting color perception.

Deuteranopia

Complete green cone deficiency affecting color perception.

Protanomaly

Altered sensitivity in red cone function

• individuals have difficulty distinguishing between reds and greens due to a reduced sensitivity to red light. .

Deutanomaly

Altered sensitivity in green cone function.

Tritanopia

Complete blue cone deficiency affecting color perception.

Red-green deficiency

Common color vision defect in males and females.

Equilibrioception

Perception of balance related to vestibular system.

Vestibular system

Inner ear system for balance and spatial orientation.

Semicircular canals

Fluid-filled structures detecting head rotation.

Utricle and saccule

Detect linear acceleration and gravity effects

• organs located in the vestibular system of the inner ear, playing a crucial role in balance and spatial orientation. .

Crista ampullaris

Receptor apparatus in semicircular canals.

Otoconia

Calcium carbonate crystals aiding gravitational detection.

Hearing

Sense of sound perception through vibrations.

Audiometry

Test measuring frequency response of human hearing.

Pure-tone audiometer

Device generating sounds of specific frequencies.

Frequency range

Humans detect sounds from 20 Hz to 20 kHz.

Tactition

Detection of vibrations through body contact.

Sound frequency

Measured in Hertz (Hz), cycles per second.

Amplitude of sound waves

Measured in decibels (dB), sound intensity.

Audiograph

Graph plotting sound frequency against amplitude.

Hearing loss

Reduced sensitivity to sound frequencies over time.

Age-related hearing loss

Common decline in high-frequency sensitivity with age.

Inner ear

Contains structures crucial for hearing and balance.

Frequency of Sound

Measured in Hertz (Hz), indicates sound pitch.

dB

Decibels, unit measuring sound intensity.

Proprioceptive Senses

Awareness of body position and movement.

Pacinian Corpuscles

Complex receptors for deep pressure and vibration.

Two-Point Discrimination

Ability to distinguish two close stimuli as separate.

Minimum Distance

Smallest separation to perceive two distinct points.

Density of Receptors

Varies across body parts, affecting sensitivity.

Thermoception

Sense detecting heat and cold temperatures.

Cold Receptors

Sensitive to temperatures below 37°C.

Warm Receptors

Sensitive to temperatures between 37°C and 45°C.

Achilles Tendon Vibration

Stimulates proprioception during balance tests.

Postural Swaying

Movement of body while maintaining upright position.

Demonstrator

Individual assisting in practical exercises for safety.

Wobble Board

Platform used to assess balance and stability.

Physiological Basis

Underlying biological mechanisms explaining sensory differences.

Statistical Difference

Comparison of data to determine significance between groups.

Standard Deviation (SD)

Measure of data variability around the mean.

Standard Error of the Mean (SEM)

Estimates accuracy of sample mean relative to population.

Temperature receptors

Found in subcutaneous skin layers, detect temperature.

Homeostatic thermoceptors

Regulate internal body temperature near hypothalamus.

Thermal illusion

Perception of temperature changes based on adaptation.

Ciliary muscle

Muscle that adjusts lens shape for focusing.

Zonule fibers

Connect ciliary muscle to the lens

They play a crucial role in adjusting the shape of the lens for focusing. .

Short sightedness

Inability to see distant objects clearly.

Far sightedness

Inability to see close objects clearly.

Perimetry

Test to measure visual field extent.

Color blindness

Difficulty distinguishing certain colors, often sex-linked.

Cone photopigments

Proteins in cones that detect color, located on X chromosome.

Dichromacy

Type of color blindness with two functioning cones.

Romberg's Test

Balance test assessing proprioception and vestibular function.

Proprioception

Sense of body position and movement.

Pacinian corpuscle

Rapidly adapting skin receptor for pressure.

Merkel disks

Slowly adapting skin receptors for light touch.

Ruffini endings

Slowly adapting receptors for skin stretch.

Meissner corpuscles

Rapidly adapting receptors for light touch.

Thermal adaptation

Decreased sensitivity to temperature after prolonged exposure.

Temperature-related injury

Damage to tissues from extreme temperature exposure.