LCSC06|Bioscience Sensation and the special senses (Directed study) Sensation and the special senses (Directed study) Dr Pedro Amarante Andrade

LCSC06|Bioscience 1. What is meant by sensation? The conscious or subconscious awareness of changes in the external or internal environment

LCSC06|Bioscience 2. Sensation can be divided into the somatic (bodily) and the special senses. What do we mean by the special senses? General senses: Somatic sensation (somat = of the body) include tactile sensations (touch, pressure, vibration, itch and tickle), Thermal sensations (warm and cold), pain sensations, and proprioceptive sensations (static & movement) Visceral senses provide information about condition within internal organs Special senses include the sensory modalities of smell, taste, vision, hearing and equilibrium or balance (selectivity).

LCSC06|Bioscience 3. Four events typically occur in order for a sensation to arise. What are these events/components of sensation? a.Stimulation of the sensory receptors b.Transduction of the stimulus c.Generation of nerve impulses d.Integration of sensory input

LCSC06|Bioscience 4. Sensory receptors can be classified according to their location in the body –exteroreceptors (near the surface), –interoreceptors (internally in the blood vessels or organs) and –proprioceptors (some of which we have already briefly discussed when looking at muscle function) a) define the terms exteroreceptor, interoreceptor and proprioceptor b) What are the different functions of receptors?

LCSC06|Bioscience 4. Sensory receptors can be classified according to their location in the body… a.Exteroreceptors (near the surface) are located at or near the external surface of the body; they are sensitive to stimuli originating outside the body and provide information about the external environment. The sensations of hearing, vision, smell, taste, touch, pressure, vibration, temperature, and pain are conveyed by exteroceptors.

LCSC06|Bioscience 4. Sensory receptors can be classified according to their location in the body… b.Interoreceptors (internally in the blood vessels or organs) or visceroceptors are located in blood vessels, visceral organs, muscles, and the nervous system and monitor conditions in the internal environment. The nerve impulses produced by interoceptors usually are not consciously perceived; occasionally, however, activation of interoceptors by strong stimuli may be felt as pain or pressure.

LCSC06|Bioscience 4. Sensory receptors can be classified according to their location in the body… c.Proprioceptors (one’s own - e.g. muscles) are located in muscles, tendons, joints, and the inner ear. They provide information about body position, muscle length and tension, and the position and movement of your joints.

LCSC06|Bioscience 4. Sensory receptors can be classified according to their location in the body… c.Proprioceptors (one’s own - e.g. muscles) are located in muscles, tendons, joints, and the inner ear. They provide information about body position, muscle length and tension, and the position and movement of your joints.

LCSC06|Bioscience TYPES OR RECEPTORS

LCSC06|Bioscience 5. Which area of the body has the highest concentration of mechanoreceptors? Why might this be? Finger tips, hands, lips and external genitalia & bottom of your feet – (sensitive to stretching that occurs as digits or limbs are moved)

LCSC06|Bioscience 6. How does stimulation of a receptor transduce into a generator potential? A sensory receptor transduces (converts) energy in a stimulus into a graded potential. Graded potentials vary in amplitude (size), depending on the strength of the stimulus that causes them, and are not propagated. Each type of sensory receptor exhibits selectivity: It can transduce only one kind of stimulus. For example, odorant molecules in the air stimulate olfactory (smell) receptors in the nose, which transduce the molecules’ chemical energy into electrical energy in the form of a graded potential.

LCSC06|Bioscience TYPES OR POTENTIALS

LCSC06|Bioscience 7. How is information about intensity and duration of a stimulus conveyed to the CNS?

LCSC06|Bioscience 8. With reference to sensation, what is meant by adaptation? Generator potentials or receptor potentials decreases in amplitude during a maintained, constant stimulus (frequency of nerve impulses in the first-order neuron to decrease) e.g. hot shower.

LCSC06|Bioscience 9. Revise the sensory pathways (see ‘Pathways’ lecture). Draw yourself a basic diagram showing the whole pathway, including receptor, first, second and third order neurons, the spinal cord and the thalamus. Which pathway decussates in the spinal cord? Which pathway decussates in the brainstem?

LCSC06|Bioscience LCSD08H | Voice and Fluency SENSORY SYSTEM Organ Ganglion CNS –Cortex CNS – Thalamus CNS – Spinal cord 3 or more neurons

LCSC06|Bioscience SENSORY PATHWAY 5/Chapter%205/A.5p%20Cerebellar%20Pathways.html

LCSC06|Bioscience 10. Some of the spinal cord pathways, as well as the somatosensory cortex, are organised somatotopically. What does this mean? Somatotopy is the point-for- point correspondence of an area of the body to a specific point on the central nervous system. Typically, the area of the body corresponds to a point on the primary somatosensory cortex (postcentral gyrus). OpenStax College

LCSC06|Bioscience 11. What aspects of sensation are integrated at the level of the spinal cord?

LCSC06|Bioscience 12. Sensory pathways from the head: Which cranial nerve carries the sensory information from the face to the CNS? Where is the nucleus of this nerve located? What cranial nerves carry somatic sensation from the buccal cavity/posterior third tongue/anterior two-thirds of the tongue? Good sections to read to get an overview of gustation (taste) and olfaction (smell) can be found in the recommended texts eg Tortora et al, Seikel et al.

LCSC06|Bioscience 12. Sensory pathways from the head: No./NameSensoryOrigin/TargetExit ForamenFunction I OlfactoryOlfactory Purely sensory Telencephalon Located in the olfactory foramina in the cribriform plate of the ethmoid bone.olfactory foraminacribriform plateethmoid bone sense of smell from the nasal cavity. [2] [2] II OpticOpticSensoryRetinal ganglion cellsLocated in the optic canal.optic canal Transmits visual signals from the retina of the eye to the brain. [3] [3] V TrigeminalTrigeminal Both sensory and motor Pons Three Parts: V 1 (ophthalmic nerve) is located in the superior orbital fissure V 2 (maxillary nerve) is located in the foramen rotundum V 3 (mandibular nerve) is located in the foramen ovale.ophthalmic nervesuperior orbital fissuremaxillary nerveforamen rotundummandibular nerveforamen ovale Receives sensation from the face and innervates the muscles of mastication.muscles of mastication VII FacialFacial Both sensory and motor PonsPons(cerebellopontin e angle) above olive Located in and runs through the internal acoustic canal to the facial canal and exits at the stylomastoid foramen. internal acoustic canalfacial canalstylomastoid foramen Receives the special sense of taste from the anterior 2/3 of the tongue and provides secretomotorinnervation to the salivary glands (except parotid) and the lacrimal gland.anterior 2/3 of the tonguesecretomotorinnervationsalivary glandslacrimal gland VIII Vestibulocochlear Vestibulocochlear Mostly sensory Lateral to CN VII (cerebellopontine angle)cerebellopontine angle Located in theinternal acoustic canal.internal acoustic canal Mediates sensation of sound, rotation, and gravity IX Glossopharyngeal Glossopharyngeal Both sensory and motor MedullaLocated in thejugular foramen.jugular foramen Receives taste from the posterior 1/3 of the tongue. Some sensation is also relayed to the brain from the palatine tonsils

LCSC06|Bioscience WHAT YOU SHOULD KNOW ABOUT SPECIAL SENSES

LCSC06|Bioscience OLFACTORY: SENSE OF SMELL Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12 th edition

LCSC06|Bioscience OLFACTORY SENSE Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience OLFACTORY SENSE Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience GUSTATION: SENSE OF TASTE Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience GUSTATION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience GUSTATION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology.

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12 th edition

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12 th edition

LCSC06|Bioscience VISION Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12 th edition