Sensory Receptors Overview

Sensory receptors

Enable response to stimuli in internal or external environment

General sense organs

Category of sense organs for overall stimuli

Special sense organs

Category of sense organs for specific stimuli

Exteroceptors

Cutaneous receptors located externally

Visceroceptors

Receptors in internal environment (viscera)

Proprioceptors

Receptors in skeletal muscle, joints, tendons for body movement

Mechanoreceptors

Activated by mechanical stimuli like movement and pressure

Chemoreceptors

Activated by smell and taste stimuli

Thermoreceptors

Detect hot or cold stimuli, mostly on the skin

Nociceptors

Receptors for pain sensations

Photoreceptors

Receptors for vision, located in the eye

Osmoreceptors

Receptors for thirst, located in the hypothalamus

Free nerve endings

Widely distributed sensory receptors, nociceptors

Tactile sensations

Include touch, stretch, pressure, vibration, itch, tickle

Root hair plexuses

Receptors for tactile sensations in hair follicles

Encapsulated nerve endings

Touch and pressure receptors in the skin

Tactile corpuscle

Touch and pressure receptor in hairless skin areas

Lamellar corpuscles

Touch and pressure receptor in deep dermis and joint capsules

Autonomic receptors

Receptors like ACh, NE, alpha, beta, nicotinic, muscarinic

Brachial plexus

Nerve network for innervating the upper limb

Axillary nerve

Innervates deltoid and teres minor muscles

Musculocutaneous nerve

Innervates coracobrachialis and biceps brachii

Radial nerve

Innervates triceps brachii and extensor muscles of the forearm

Median nerve

Innervates flexors of the forearm and anterior hand

Ulnar nerve

Innervates flexor carpi ulnaris and intrinsic hand muscles

Anatomy of brain

Includes medulla, pons, mid-brain, diencephalon, cerebellum, cerebrum

Action potential

Rapid electrical fluctuation along a neuron's membrane

Reflex arc

Pathway for nerve impulses producing reflex actions

Joint types

Classified into nonaxial, uniaxial, biaxial, multiaxial

Sliding filament theory

Muscle contraction mechanism involving myosin and actin

Troponin

Binds calcium for muscle contraction initiation

Sarcoplasmic Reticulum

Supplies calcium for muscle contraction

Golgi Tendon Organ

Detects excessive muscle tension to induce relaxation

Muscle Spindles

Relay muscle length changes information

Cranial Nerves

12 pairs controlling various head and neck functions

Hypothalamus

Regulates heart rate, temperature, and hormone release

Neurons

Unipolar, bipolar, and multipolar types conduct impulses

Glial Cells

Support and protect neurons in the nervous system

Nerve Conduction

Impulse transmission from dendrites to synaptic bulb

Membrane Potential

Voltage difference across a cell membrane

Isotonic Contraction

Muscle length changes with constant tension

Isometric Contraction

Muscle contracts without movement

Hyaline Cartilage

Resembles milk glass, forms costal cartilages

Elastic Cartilage

Most flexible, found in external ear and epiglottis

Fibrocartilage

Strongest type with abundant fibrous elements

Endoneurium

Covers individual muscle fibers

Perineurium

Surrounds fiber bundles in the nervous system

Epineurium

Encloses complete nerve structures

Neurotransmitters

Chemicals transmitting signals across synapses

CNS Diseases

Various disorders affecting the central nervous system

Accommodation in Vision

Lens, pupil, and eye convergence adjustments for focus