Chapter 9 Function of the Sense Organs
Chapter 9 Function of the Sense Organs
Introduction Human life would be very different without the ability to sense and perceive external stimul Imagine your world without the ability to see, hear smell. touch. and feel
• Human life would be very different without the ability to sense and perceive external stimuli • Imagine your world without the ability to see, hear, smell, touch, and feel Introduction
Sensations Define sensation: A state of awareness of a stimulus Awareness When a stimulus is detected by the body below the level of consciousness Such as a change in blood pressure or blood pH Perception When a stimulus reaches consciousness; pain, hunger, thirst, sight sound, etc
Sensation requires 1) stimulus Any change in the environment, either internal or external, can generate a stimulus. Example: body temp, pH, BP, light, sound. 2) receptor A structure which detects a stimulus and converts it into an action potential 3)impulse conducted The action potential is send via dendrites to the somas of sensory neurons in the CNS 4)translation The particular region of the CNs that receives the APs will convert them an awareness of the stimulus
Environmental sensation is limited to those forms of energy that sensory receptors are designed to detect Sensory receptors may convey information to the cortex with awareness or perception and may lead to cerebrally controlled responses Sensory receptors also serve as afferent pathways for reflex action with or without conscious sensation
• Environmental sensation is limited to those forms of energy that sensory receptors are designed to detect. • Sensory receptors may convey information to the cortex with awareness or perception and may lead to cerebrally controlled responses. • Sensory receptors also serve as afferent pathways for reflex action with or without conscious sensation
Section 1 Physiology of the receptor and Sense organs I Concept and classification of the Receptor and sense organs
Section 1 Physiology of the Receptor and Sense Organs I Concept and Classification of the Receptor and Sense Organs
Sensory receptors Receptors are specialized nerve cells that transduce energy into neural signals Receptors lack axons, form synapses with dendrites of other sensory neurons Receptors are mode specific Law of specific Nerve Energies": sensory messages are carried on separate channels to different areas of the brain Receptors detect a small range of energy levels Eve:400-700nM Ear:20-20.000Hz Taste buds: specific chemicals
Sensory Receptors • Receptors are specialized nerve cells that transduce energy into neural signals – Receptors lack axons, form synapses with dendrites of other sensory neurons • Receptors are “mode” specific – “Law of Specific Nerve Energies”: sensory messages are carried on separate channels to different areas of the brain • Receptors detect a small range of energy levels – Eye: 400-700 nM – Ear: 20-20,000 Hz – Taste buds: specific chemicals
Spectrum of the Electromagnetic Wave Copyright e The McGraw-Hill Companies, Inc. Permission required for reproduction or display Increasing energy Increasing wavelength 0.001 11010000.01 100 nm nm nm nm cm cm Gamma rays rays light Infrared Microwaves Radio waves Visible light 380430 500 560600650 750 nm nm n nm nm nm nm
Spectrum of the Electromagnetic Wave
Which receptor? Receptors Cell membrane or Specialized cells or structures cytoplasmic receptor for the transduction of varlous proteins stimuli into electrical signals Central Peripheral receptors receptors Eyes(vision) Chemoreceptor(pH, gases, chemicals) Osmoreceptor(osmolarity) Thermoreceptor( temperature) Ears(hearing equilibrium) Baroreceptor(pressure) Proprioceptor(body position) Nose(smell) Other mechanoreceptors pain, vibration, touch) Tongue(taste)
Which receptor?
Stimulus General sensory receptor structure Free nerve endings Free nerve endings dendrites interspersed Unmyelinated axon among other cells/tissues(pain temperature touch Cell body Simple neural receptor
General sensory receptor structure • Free nerve endings: dendrites interspersed among other cells/tissues (pain, temperature, touch)
