Sensory

Biol. 211 Anatomy & Physiology 1

Tony Serino, Ph.D.

Biology Department

Misericordia University

Sensation –state of awareness of external and internal conditions of the

body

• Four conditions for sensation:– 1. Adequate stimulus– 2. Adequate receptor (transducer)– 3. Conduction– 4. Translation (interpretation)

Brain’s Assumption in Translating

Assumption: Source of light is from above

Reversing X pattern; notice shading.

How many triangles?

Assumption: Straight lines should connect.

Which dark line is larger?

Assumption: perspective

Characteristics of Sensation

• Modality –ability to interpret nerve impulses differently

• Projection –referral of sensation to point of origin

• Adaptation –decrease in sensitivity of receptors to continued stimulation

– Phasic (fast)– Tonic (slow)– Some receptors never adapt (pain, cold, etc.)

• Afterimage –persistence of sensation after stimulus ceases

Classification of Receptors• Type of Sensory Information Relayed

– Exteroreceptors, Enteroreceptors, Proprioceptors

• Type of Stimulus Transduced– Mechanoreceptors, Thermoreceptors, Chemoreceptors,

and Nociceptors

• Complexity of Receptor– Simple structure (usually single cell) –most general senses

– Complex structure (many cells) –special senses

Receptor Physiology• Stimulation of a receptor leads to the generation of a

receptor (generator) potential in its membrane.

• These are usually excitatory, and are similar to the EPSPs found in neurons

• If the receptor potential reaches the threshold potential for the sensory neuron; it fires an AP into the CNS

• Strength of the stimulus is therefore encoded by the number of AP generated

• Sensations may be sharpened through Lateral Inhibition

Lateral Inhibition

- -

General Senses

• Cutaneous –skin receptors

• Proprioception –sense of body position

• Nociception –pain perception (chemoreceptors that perceive locally secreted warning hormones (prostaglandins))

Distribution of Cutaneous Receptors

Sensitivity of Skin due to Receptive Fields

Cutaneous Receptors

Proprioceptors

Muscle sensors

Muscle spindles (Intrafusal fibers:-senses degree of length of muscle fibers and the rate of change in length

Golgi Tendon organs –sense tension within tendon

Relationship of Stretch to AP

Referred PainIllustrates projection.

General Pathway of Perception

Taste (Gustatory) Sense

Taste Bud

Olfaction (smell) Sense

Olfactory Epithelium

Olfaction Signal Transduction

Vision

Accessory Structures of the Eye

Lacrimal Apparatus

Extrinsic Ocular Muscles

Action and Innervation of Ocular Muscles

Which cranial nerve is injured?

Eye Anatomy

(Canal of Schlemm)

Aqueous Humor Flow

Glaucoma results frominadequate drainage ofAqueous Humor leading to increase pressure in the eye.

Iris controls amount of light entering the eye.

Distant Vision

Near Vision (Accomodation)

Near and Far-sightedness

Astigmatism and Presbyopia

• Astigmatism –results from imperfections in the resolving structures in the eye (lens and/or cornea)

• Presbyopia is the loss of near vision with age; resulting from a decrease in elasticity of the lens.

Retina Cellular Arrangement

Special Areas of Retina

Blind Spot

Optic N.

Optic Disc(blind spot)

Photoreceptors: Cones and Rods

Three Population of Cones

Rod’s and Cone’s Photopigments

Rhodopsin

Light Signal Transduction

Visual Processing

Sound

Frequency vs.

Loudness

Frequency measured in hertz (Hz)

Loudness measured in decibels (dB)

Anatomy of the Ear

Middle and Inner Ear

Ossicles Amplify Sound

Loud Sound Protection

Middle Ear Ossicles

Cochlea and Cochlear Duct

Organ of Corti

Hair Cells in Cochlear Duct

Frequency Perception

• Different frequency (pitch) of sound stimulates different areas of cochlear duct

• The overall area stimulated relates to the sound intensity

Vestibular Apparatus

Macula of Utricle and Saccule

Macula

Otoconia (otoliths)

Hair Cell of Macula

AP Generation in Macula

Ampulla Anatomy