Sensory Receptors Overview

Sensory Receptors

• Specialized cells that monitor internal and external conditions, generating action potentials in response to stimuli.
• Types include mechanoreceptors (detect mechanical force), thermoreceptors (sense temperature), chemoreceptors (monitor chemicals), nociceptors (detect pain), and photoreceptors (respond to light).

Mechanoreceptors and Other Receptors

• Mechanoreceptors respond to physical deformation caused by touch, pressure, or stretching.
• Thermoreceptors are responsible for sensing changes in temperature, both hot and cold.
• Chemoreceptors are involved in sensing environmental chemicals, such as taste and smell.

Pain and Pressure Receptors

• Nociceptors specifically detect pain stimuli, while other receptors like free nerve endings respond to temperature and tissue movements.
• Various types of pressure receptors exist, including Meissner's corpuscles (light pressure), Pacinian corpuscles (heavy pressure), and Ruffini's endings (deep pressure).

Interoception and Proprioception

• Exteroceptors detect stimuli from the external environment (touch, pressure, pain, temperature).
• Interoceptors monitor internal body conditions like chemical changes and organ stretch, often causing sensations of pain or discomfort.
• Proprioceptors inform the brain about body movements and positions, located in muscles and joints.

Adaptation and Sensory Processing

• Sensory adaptation refers to the diminishing sensitivity to a constant stimulus.
• Phasic receptors react quickly and adapt, such as those in the retina, while tonic receptors maintain sensitivity over time, relevant to pain and body position.
• Sensation and perception involve a multi-step process: stimulus detection, nerve circuitry, and brain interpretation.

Nerve Structure and Types

• Nerves are composed of bundles of axons surrounded by connective tissue layers: endoneurium (individual fibers), perineurium (fascicles), and epineurium (entire nerve).
• Three nerve types exist: mixed (both sensory and motor), sensory (toward CNS), and motor (away from CNS).

Cranial Nerves

• Twelve cranial nerves, each with distinct functions, including sensory (olfactory, optic, vestibular), motor (oculomotor, trochlear, abducens, accessory, hypoglossal), and mixed (trigeminal, facial, glossopharyngeal, vagus).
• Functions range from smell and vision to facial movement and equilibrium.

Spinal Nerves and Reflexes

• Spinal nerves consist of 31 pairs, supplying sensory and motor innervation to the body, except the head and some neck areas.
• Dermatome refers to areas of skin innervated by specific spinal nerves, crucial for assessing sensory function.
• Reflex tests, such as the plantar reflex and Babinski's sign, help evaluate neurological health.

Neurological Conditions

• Conditions like sciatica (nerve pain), tabes dorsalis (deterioration due to syphilis), neurofibromatosis (hereditary tumors in nerve tissues), shingles (painful skin infection post-chickenpox), and neuritis (nerve inflammation) highlight common neurological issues.
• Hilton's law states that a nerve serving a muscle also innervates the joint and skin over that joint, indicating a relationship between muscle movement and skin sensation.

Explore the fascinating world of sensory receptors in this quiz. Learn about different types of receptors such as mechanoreceptors, thermoreceptors, chemoreceptors, nociceptors, and photoreceptors, and how they respond to various stimuli. Test your knowledge on how these specialized cells monitor both internal and external conditions.