Nervous System III Anatomy and Physiology Notes Ch. 12a Nervous System III Anatomy and Physiology

Introduction to Sensory Function Senses are important for connecting to the outside world but also in maintaining homeostasis. Sensory receptors link our nervous system to the outside world. General senses have receptors widely distributed throughout the body (skin, various organs, and joints) Special senses have specialized receptors and are found in the head – like the eyes and ears.

Receptors, Sensation, and Perception How do we interpret different sensory events? It depends on receptors that respond to specific stimuli. All sensory receptors are specific to a certain type of environmental change. Sensation is the raw form that receptors send information to the brain. Perception is the way the brain interprets the information.

Receptor Types 1. Chemoreceptors – respond to changes in the concentration of chemicals. Receptors that have to do with smell and taste are this type of receptor. Also chemoreceptors in internal organs detect the changes in blood concentrations of oxygen, hydrogen ions, glucose, etc.

2. Pain Receptors – respond to tissue damage. This includes any exposer to excess mechanical, electrical, thermal, or chemical energy.

3. Thermoreceptors – Sense temperature change

4. Mechanoreceptors – Sense mechanical forces by picking up any changes that deform the receptors. There are many in the skin that respond to physical contact. Also in the ear to give information about balance and vibrations from sound. Proprioceptors – sense changes in the muscles and tendons Barorreceptors in the blood vessels detect changes in blood pressure Stretch receptors in the lungs sense inflation

5. Photoreceptors – in the eyes respond to light energy of sufficient intensity.

Sensory Impulses Sensory receptors can be the ends of neurons or other cells near neurons. When stimulation occurs it changes the cells’ membrane potentials. In neurons it gives an action potential. In other types of cell the signal has to be transferred to a neuron.

Sensation and Perception A sensation happens when sensory neurons reach threshold and an action potential occurs. A perception occurs when the brain interprets those sensory impulses. Example – pain is a sensation, but realizing you stepped on a tack is a perception.

Most of the time sensory receptors are specialized to certain types stimuli but may respond to other stimuli if strong enough. Example – getting hit on the head can trigger visual receptors causing someone to see stars.

Sensory Adaptation The brain has to prioritize the sensory input it receives or it would be overwhelming. For example – until reading this makes you think about it, you are probably unaware of the pressure of your clothing against your skin, or the background noise in the room. Sensory adaptation is the ability to ignore unimportant stimuli. Watch this link! https://www.youtube.com/watch ?v=nZoNl2t_3tc