Special Senses (I)

Sensory Receptor

any structure specialized to detect a stimulus

sense organ

a structure that combines nervous tissue with other tissues that enhance its response to a certain type of stimulus

exteroceptors

sense stimuli external to the body

interoceptors

detect stimuli in the internal organs - also called visceroceptors

receptor potential

a type of local potential

sensory adaption

if the stimulus is prolonged - lowers neuron firing frequency - less aware of stimulus

tactile receptors

vibration/touch/pressure

proprioceptors

stretch

baroreceptors

tension/pressure changes in walls of blood vessels, digestive organs, bladder, lungs

thermoreceptors

detect temperature

mechanoreceptors

sense the position and movements of the body or its parts

chemoreceptors

detect chemicals/molcules in the body

photoreceptors

vision

nociceptors

detect pain

special senses

limited to the head, smell, taste, balance, hearing, and vision, non-neuronal receptors have graded changes in membrane potential, stimulus triggers NT release from sensory cells, except for olfactory neurons

general senses

receptors all over the body, touch, pain, temperature, neurons fire action potentials, unipolar neurons

free nerve endings

pain, heat, and cold

meissner’s corpuscle (tactile)

responds to flutter and stroking movements

merkel disc = tactile disc

sense steady pressure and texture - compression of the skin releases serotonin

pacinian (lamellar) corpuscle

vibration

bulbous corpuscle (ruffini)

heavy continous touch/pressure stretch of skin

hair receptor

light touch - sense hair movement

end bulb (krause)

temperature? touch?

nociceptive pain

stems from tissue injury, visceral pain, and somatic pain

visceral pain

mucosal injury, obstructions or capsular distension

somatic pain

deep: bones, joints, muscles. Superficial: skin

pain

uncomfortable conscious perception of tissue injury or noxious stimulation, it is subjective, highly variable, and influenced by mental state

neuropathic pain

Pain caused by lesions or disease of the somatosensory nervous system occurs when peripheral nerves are damaged, such as in strokes, multiple sclerosis, or spinal cord injury.

nociplastic pain

mechanistic descriptor for chronic pain and altered nociceptive function like fibromyalgia and IBS

endogenous molecules

They contribute to the transmission of pain and make the nociceptors more sensitive. they are released as part of the inflammatory response to an injury

taste buds

the true taste organ

papillae

fungiform and vallate

tastants

chemical stimuli

sweet

carbohydrates

bitter

spoiled foods and alkaloids (nicotine and caffeine)

salt

produced by metal ions (Na+ and K+)

sour

associated with acids

umani

a meaty taste produced by aas such as aspartic and glutamate acids

gustatory receptors

1. taste buds

2. cranial nerves X, IX, & VII

3. NTS (nucleus of the solitary tract)

4. amygdala and hypothalamus

5. orbitofrontal cortex and gustatory cortex (insula)

odorants

airborne chemicals that produce an olfaction response, they’re detected by receptor cells in a patch of epithelium, the olfactory mucosa, in the roof of the nasal cavity

secondary olfactory cortex

Composed of the insula and the OFC, the orbitofrontal cortex, in the PFC, above the eyes, is where we identify and discriminate among odors.

primary olfactory cortex

In the temporal lobe, it receives input directly from the olfactory bulb and creates conscious perception of odors, relaying signals to other brain destinations.

granule cells

can inhibit the mitral and tufted cells

olfactory discrimination

An effect of this feedback is that odors can change in quality and significantly under different conditions