SENSORY SYSTEMS COMPREHENSIVE LECTURE, Lecture notes of Anatomy

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SENSORY SYSTEMS

SENSORY RECEPTORS AND THEIR RELATED

SENSORY PATHWAYS

DR. BEDA OLABU

LECTURE OBJECTIVES

1. Types of sensations (sensory modalities)
2. Examples and classification of sensory receptors
3. General sensations and their related sensory pathways
4. Organs and receptors of special sensations
5. Special sensations and their related sensory pathways

SOMATIC SENSATIONS

Detected from the body wall (skin or muscle) a) Cutaneous sensations: Tactile (touch), pressure, pain and thermal (temperature) sensations b) Deep sensations: Proprioception and vibration

DEFINITION

2: Sensory receptor:

Specialized neuron or epithelial cell that detects a stimulus Converts environmental stimulus into nerve impulses

DEFINITION

3: Sensory organ:

An organ that houses a sensory receptor Examples include skin………

I: GENERAL SENSATIONS

1. Receptors for general sensations

2. Sensory transduction mechanism

3. Sensory relay pathway

4. Spinal cord sensory pathways

RECEPTORS FOR GENERAL SENSATIONS Thermal receptors:

Ruffini corpuscles

Krause end bulb

RECEPTORS FOR GENERAL SENSATIONS

Pain receptors:

Free nerve endings

Vibration receptors:

Pacinian corpuscles

 Stimuli are converted to graded potentials by the receptors  Potentials above threshold are propagated (as APs)

SENSORY TRANSDUCTION

SENSORY RELAY PATHWAYS

SENSORY RECEPTORS CEREBRAL CORTEX Detect the stimuli Perception & recognition Primary ( st order) sensory neuron SPINAL CORD OR BRAINSTEM Secondary ( nd order) sensory neuron THE THALAMUS

rd Order sensory neuron AFFERENT NERVE SYSTEMS

SPINAL CORD SENSORY PATHWAYS

1. Dorsal columns

2. Spinothalamic

3. Spinocerebellar

II: SPECIAL SENSATIONS

1. Receptors for special sensations

2. Sensory pathways for the special sensations

Focus on: Olfaction, taste, hearing,

equilibrium & vision

Detected by olfactory epithelium, which has chemoreceptor cells Relayed by the olfactory nerve, bulb and tract to the brain Piriform lobe in the temporal cortex

1: OLFACTORY SENSATION

Basic taste sensations:

1. Sweet

2. Sour

3. Bitter

4. Salty

5. Umami

2: TASTE SENSATION