the somatic senses sensory reception of the five senses
TRANSCRIPT
The Somatic Senses
Sensory reception of the five senses
Receptors Five types of receptors
Chemoreceptor – changes in chemical concentrations
Pain – tissue damage Temperature (thermoreceptors)- changes in
temp Mechanoreceptors – changes in pressure and
movement Photoreceptors – changes in light energy
Sensation – what is it?When you touch an objects actually, are
they really hot or cold?
What is happening when you touch hot water or step outside when it is very “cold” out?
Sensation is.. The feeling when the brain interprets
sensory impulses. What you feel when you touch something
“hot” or “cold” is the energy transfer into or out of your body.
Projection is … When the cerebral cortex causes the
feeling to seem to come from the stimulated receptors. This is at the same time the sensation forms.
Basically the brain projects the sensation back to its apparent source.
This allows to pinpoint the region of stimulation. The eyes seem to see; the ears seem to hear.
Sensory adaptation… When sensory receptors are continuously
stimulated As receptors adapt, the impulses
decrease, and continue to decrease, and the reception may even stop
Change in strength of the stimulus will trigger impulses again
Touch and Pressure - Mechanoreceptors: Three kinds of receptors: sensory
nerve fibers (free end), Meissener’s Corpuscles, Pacinian corpuscles
These receptors perceive sensations such as pressure, vibrations, and texture.
Touch and Pressure - Mechanoreceptors: Those found in the very top layers of the
dermis and epidermis and are generally found in non-hairy skin such as the palms, lips, tongue, soles of feet, fingertips, eyelids, and the face.
Those located deeper in the dermis and along joints, tendons, and muscles feel sensations such as vibrations
traveling down bones and tendons, rotational movement of limbs, and the stretching of skin. This greatly aids your ability to do physical activities such as walking and playing ball.
Temperature Senses Two types of free nerve
endings: warm and cold Warm Receptors
Most sensitive at temps above 77oF
Unresponsive at temps above 113oF
This will stimulate pain receptors, produces burning sensation
Cold receptors Most sensitive between 50-68oF Temps below 50oF stimulate pain
receptors, produces freezing sensation
Temperature Senses Cold receptors are found in greater density than
heat receptors. The highest concentration of thermoreceptors can be found in the face and ears (hence why your nose and ears always get colder faster than the rest of your body on a chilly winter day).
Pain receptors Free nerve endings Widely distributed throughout the body,
except in the nervous tissue and brain Adapt poorly, if at all Once stimulated, may continue to send
impulses to the CNS = persistent pain Pain is poorly understood
Pain Pain elicited during a muscle cramp stems
from sustained contraction that squeezes capillaries and interrupts blood flow.
Deficiency in oxygen-rich blood may trigger pain sensations
Referred pain Pain that is coming from some part of the
body other than the part being stimulated Pain from the heart may be felt from the left
shoulder or upper left limb. Generally comes from visceral pain = deep
within the body/ visceral tissue
Special Senses = smell, taste, sight, hearing /equilibrium,
Sense Organ
Smell Olfactory organs
Taste Taste buds
Hearing/ equilbrium Ears
Sight eyes
Smell Olfactory receptor cells =
bipolar Stimulated fibers synapse
with neurons in olfactory bulb
Impulses from the olfactory bulb travel along olfactory tracts to the limbic system
Major interpretation sites are found in the temporal lobes and parts of the frontal lobe.
Olfactory Stimulation Uncertain how this stimulation begins Smells are interpreted as a code
For example, if there are 10 receptors, parsley may stimulate receptors 3, 4, & 8 and chocolate might stimulate 1,5, & 10
Olfactory organs are located high in the nasal cavity May need to force air in during inhale to get a
faint smell Undergo sensory adaptation rapidly
Taste
Each taste bud has a group of taste cells Each bud has 50-150 cells replaced every three days
Entire structure is within the taste pore
Tiny projections are called taste hairs
Taste Salivary glands dissolve chemicals in order for
the tongue to taste 4-7 taste sensations
Sweet Sour Salty Bitter Metallic Alkaline Umami – detects MSG
Taste Each taste cell can detect two sensations,
although one sensation may dominate over the other
Taste cells undergo sensory adaptation rapidly
Impulses move from taste cells through facial, glossopharyngeal and vagus nerves to medulla oblongata They then move to the thalamus to the parietal
lobe
Hearing The ear has an external, middle and inner
part External ear has two parts – auricle and the
external auditory meatus Both direct sound waves toward the middle ear
Middle ear – includes tympanic cavity, eardrum, and auditory ossicles (three small bones)
Eardrum moves back and forth in response to vibrations of the sound wave
These vibrations are transferred to the auditory ossicles, which then stimulate the hearing receptors
Hearing The ear has an external, middle and inner
part Inner Ear – comprised of two labyrinths which
include semicircular canals and the cochlea Sound waves move through this area exciting
hair cells (nerve cells) Sound frequency stimulates only certain cells Cells do not have dendrites or axons, but act
very much like a neuron Impulses are interpreted in the temporal lobe
of the brain
Sight