Transcript Sensory - Misericordia University

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:
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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
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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 Pain
Illustrates 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
Aqueous Humor Flow
(Canal of Schlemm)
Glaucoma results from
inadequate drainage of
Aqueous 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 Disc
(blind spot)
Optic N.
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