Chapter 12 - Special Senses Flashcards
Senses
maintain homeostasis by providing information about the outside world and environment
2 Categories of Senses
- General: receptors widely distributed throughout the body
○ e.g. skin, various organs, joints- Special: specialized receptors confined to structures in the head
○ E.g. ears, nose, mouth
- Special: specialized receptors confined to structures in the head
Pathway of Sensory Information
- The stimulus stimulates sensory receptors
- Transduction occurs where the stimulus is converted into receptor potentials
- Transmission occurs where the receptor potentials trigger action potentials and are conducted along sensory neurons to the CNS
- Interpretation occurs in the CNS
5 Types of Sensory Receptors
- Chemoreceptors: respond to changes in chemical concentrations
○ E.g. smell, taste, oxygen concentration- Pain(nociceptors) receptors: respond to tissue damage
- Thermoreceptors: respond to moderate changes in temperature
- Mechanoreceptors: respond to mechanical forces distorting receptors
○ E.g. touch, stretch, tension - Photoreceptors: respond to light
Sensation V Perception
Sensation: when action potentials make the brain aware of an event
- Awareness of pain
Perception: when the brain interprets sensory impulses
- e.g. realizing pain is due to stepping on a tack
Sensory Projection
when the cerebral cortex interprets sensation as being derived/originating from certain receptors
- Allows a person to locate the region of stimulation due to feeling it at that location
Sensory Adaptation
is done to help ignore unimportant or continuous stimuli leading to stronger stimuli required to trigger impulses
- Best done by thermo or olfactory receptors
Types of General Senses
- Exteroceptive Senses: senses associated with body surface like touch, pressure, temperature and pain
- Interoceptive senses: senses associated with changes in the viscera like BP stretching blood vessels
- Proprioceptive senses: associated with changes in muscles, tendons and joints
- Interoceptive senses: senses associated with changes in the viscera like BP stretching blood vessels
Types of Mechanoreceptors
- Free nerve endings: common in epithelial tissues and sense itching
- Tactile corpuscles: detect fine touch and texture and help distinguish between 2 points
- Lamellated corpuscles: detect heavy pressure and vibrations
Thermoreceptors
free nerve endings in the skin
- Warm receptors are sensitive to temperatures above 77F
- Cold receptors are sensitive to temperatures between 50-60F
Pain Receptors(Nociceptors)
- Consist of free nerve endings and are widely distributed
- No adaptation
Referred pain
visceral pain that can be felt in different areas of the body due to common nerve pathways
Pain Pathways
- Fast Pain: myelinated fibers which conduct impulses rapidly and stop as soon as the stimulus stops
- Slow pain: unmyelinated which conduct impulses slowly and often create aching pain even after the stimulus stops
Types of Proprioceptors
- Lamellated corpuscles: detect pressure in joints
- Muscle spindles: stretch receptors in skeletal muscles and initiate stretch reflexes
- Golgi tendon organs: stretch receptors in tendons that oppose stretch reflexes and help maintain posture
- Muscle spindles: stretch receptors in skeletal muscles and initiate stretch reflexes
Visceral Senses
lamellated corpuscles and free nerve endings which convey information such as feelings of fullness after a meal or discomfort of intestinal gas
Synesthesia
where the brain interprets a stimulus for one sense as coming from another
- e.g. the paint smelled blue
Can be caused by genetic mutations/TBI
Olfactory Nerves
- Olfactory receptor cells are chemoreceptors and provide 75-80% of sense of taste
- Olfactory neurons have knobs covered in cilia found in the upper part of the nasal cavity
- 400 different types which result in unique action potentials(allows for different smells/tastes)
○ Each receptor cell contains 1 type of membrane protein which codes for a certain odorant
- Undergo sensory adaptation quickly losing 50% of smell within 1 second of stimulation