SENSE- is the ability to perceive stimuli.
SENSATION (PERCEPTION)- is the conscious awareness of stimuli received by sensory receptors. GENERAL SENSES- are those with receptors distributed over a large part of the body. SOMATIC SENSES- provides sensory information about the body and the environment. VISCERAL SENSES- are more specialized in structure and are localized to specific parts of the body such as pain and pressure. SPECIAL SENSES- are more specialized in structure such as smell, taste, sight, hearing and balance. GENERAL SENSES
RECEPTORS- are sensory nerve endings or specialized cells capable of responding to stimuli. TYPES:
1. Mechanoreceptors – respond to mechanical stimuli such as bending or stretching of receptors. 2. Chemoreceptors – respond to chemicals such as odor molecules. 3. Photoreceptors – respond to light.
4. Thermoreceptors – respond to temperature changes.
5. Nociceptors – respond to stimuli that result in the sensation of pain. RECEPTOR OF THE SKIN
1. Free nerve endings
2. Cold receptors respond to decreasing temperatures but stop responding below 12°C and Hot receptors respond to increasing temperature but stop above 47°C. 3. Touch receptors:
a. Merkel’s disks and Hair follicle receptors detects light touch and superficial pressure.
b. Meissner’s corpuscles involved in fine and discriminative touch.
c. Ruffini’s end organs detects continuous touch and pressure.
d. Pascinian corpuscles detects deep pressure, vibration and position. PAIN
Pain is a sensation characterized by a group of unpleasant perceptual and emotional experiences. Types:
1.Sharp, localized, pricking or cutting pain resulting from rapid action potentials. 2. Diffuse, burning, or aching pain resulting from slow action potentials. Referred pain- is a painful sensation perceived to originate in a region of the body that is not the source of the pain stimulus. SPECIAL SENSES
OLFACTION- is the sense of smell that occur in response to Odorants. Neuronal pathways for olfaction:
Axon of the olfactory neurons from the olfactory nerves, which enter the olfactory bulb. Olfactory tracts carry action potentials from the olfactory bulbs to the olfactory cortex of the brain. TASTE
1. Taste buds contain taste cells with hairs that extend into taste pores. Receptors on the hairs detect dissolved substances. 2. There are five basic taste types: sour, salty, bitter, sweet and umami. Neuronal pathways for taste: the facial nerves carry taste from the anterior 2/3 of the tongue, the glossopharyngeal from the posterior 1/3 of the tongue and vagus nerve from the root of the tongue. VISION
1. The eyebrows prevent perspiration from entering the eyes. 2. The eyelids protect the eyes from foreign objects.
3. The conjuctiva covers the inner eyelids and the anterior surface of the eye. 4. Lacrimal glands produce tears. Tears lubricate and protect the eyes. 5. The extrinsic eye muscles move the eyeball.
SPECIAL SENSES: Anatomy of the Eye
Fibrous tunic- is the outer layer of the eye. It consists of sclera and cornea. Vascular tunic- is the middle layer that consists of choroid, ciliary body and iris. Nervous tunic or Retina- is the innermost layer which consists of outer pigmented retina and inner sensory retina. The inner retina contains photoreceptor cells called Rod and Cones. SPECIAL SENSES: Functions of the Eye
Rods- are responsible for vision in low illumination (night vision). Cones- are responsible for color vision.
Light causes retinal to change shape, causing opsin to change shape, causing cellular changes that result in vision. SPECIAL SENSES: Neuronal Pathways for Vision
Axons pass through the optic nerves to the optic chiasm, where some cross. Axons from the nasal retina cross and those from the temporal retina do not. Optic tracts- from the chiasm lead to the thalamus.
Optic radiations- extend from the thalamus to the visual...
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