physiology- sense organs (general and chemical senses)

the organs of special senses projects to where

specialized regions of the brain

where does the special sense of taste project to

lower end of postcentral gyrus

where does the special sense of smell project to

medial temporal lobe and inferior frontal lobe

where does the special sense of vision project to

occipital lobe

where does the special sense of hearing project to

superior temporal lobe

where does the special sense of equilibrium project to

cerebellum and lateral/central sulcus via the thalamus

what area of the brain is responsible for interpreting the sensory info about the position of the limbs, location of touch or pain, shape, weight, and texture of an object

somesthetic association area in the parietal lobe

what area of the brain is responsible for interpreting the sensory info about identifying things we see

visual association area in occipital lobe

what area of the brain is responsible for recalling the name of a piece of music or identifying a person by their voice

auditory association area in the occipital lobe

any structure that specializes in detecting a stimulus and some are simple while some are entire organs; acts as a transducer

sensory receptor

combines nervous tissue with others that enhance its response to a specific time of stimulus

sense organ

converting stimulus energy into nerve energy

sensory transduction

local electrical change in receptor cell where the stimulus must be strong enough to cause an AP in the neuron as well as for the release of a neurotransmitter for the epithelial cell that stimulates the AP in the neuron

receptor potential

what are the four aspects of information transmission from receptors

modality, location, intensity, and duration

transmission from receptor that is the type of stimulus and has a labeled line code so the sensory nerve fiber to the CNS is a line from a specific kind of receptor

modality

aspect of transmission from receptors that any sensory neuron detects within a receptive field that varies in size

location

aspect of transmission from receptors that is encoded in three ways and could be soft v loud, bright v dim, or mild v excruciating pain

intensity

what three ways could intensity be encoded

stimulus intensity rises then firing frequency rises, intense stimuli recruit more numbers of nerve fibers to fire, or weak stimulate activate only most sensitive fibers

aspect of transmission that is encoded by changes in firing frequency over time

duration

what are the difference receptors classified by

how quickly they adapt

demonstrated by all receptors and occurs when a stimulus is prolonged so the firing neuron will fire slower over time

sensory adaptaion

type of sensory receptor that has a burst of activity but with quick adaptation

phasic receptor

type of sensory receptor that is slow to adapt but continually generates impulses

tonic receptor

what are the receptors with unencapsulated endings

free nerve endings, tactile discs, and hair receptors

what modalities are free nerve endings responsible for

pain, heat, cold

what modalities are tactile discs responsible for

light touch and pressure

what modalities are hair receptors responsible for

light touch and movement of hairs

what modalities are tactile corpuscles and end bulbs responsible for

light touch and texture

what modalities are bulbous corpuscles responsible for

heavy continuous tough or pressure and joint movements

what modalities are lamellar corpuscles responsible for

deep pressure, stretch, tickle, and vibration

what modalities are muscle spindles and tendon organs responsible for

muscle stretch and tension on tendons (proprioception)

what is the path of the 1st order neuron if it is coming from the body for general senses

enters the dorsal horn of spinal cord from the spinal nerves

what is the path of the 1st order neuron if it is coming from the head for general senses

enters the pons and medulla from the cranial nerve

what is the path of the 2nd order neuron for general senses

decussates to opposite side in spinal cord or the medulla/pons and ends in the thalamus except for proprioception (cerebellum)

what is the path of the 3rd order neuron for general senses

thalamus to the primary somesthetic cortex of cerebrum

an uncomfortable perception of tissue injury or noxious stimulus

pain

allow awareness of tissue injuries and are found in all tissues except the brain

nociceptors

responds to injury within the tissues and inflammation including visceral pain, deep somatic pain, or superficial somatic pain

nociceptive pain

responds to injuries to nerves, spinal cord, meninges and brain and could be headaches, stabbing, burning, tingling, or electrical pain

neuropathic pain

what are the two types of pain responses/ qualities

fast or slow pain

travels in myelinated fibers at 12-30m/sec and results in an immediate sharp, localized, stabbing pain with injury; discriminative in location

fast pain

what fibers is fast pain mediated by

A-delta

travels in unmyelinated fibers at .5-3m/sec and results in pain that is longer-lasting, dull, and diffuse feeling; hard to tell the location

slow pain

what fibers is slow pain mediated by

C fibers

what are the two main pathways that pain reaches the brain by

4 cranial nerves above the neck and three ascending spinal cord tracts for below the neck

what is the main pathway for pain for above the neck

trigeminal nerve (CN V) →pons →descend to synapse in medulla→ ascend to thalamus→ cerebral cortex

what is the secondary pathway for pain above the neck

facial (III) →glossopharyngeal→ vagus→medulla→thalamus→ cerebral cortex

what are the three pathways for pain below the neck

spinothalamic, spinoreticular, and gracile fasciculus

responsible for somatic pain we are conscious of and is the most significant pain pathway and carries most signals that reach cerebral cortex

spinothalamic

activates visceral, emotional, and behavior reactions to pain and carries pain signals to reticular formation and are relayed to hypothalamus and limbic system

spinoreticular

responsible for visceral pain

gracile fasciculus

what is the pathway for somatic pain

post central gyrus of the sensory homunculus

what is the pathway for visceral pain

lateral sulcus in viscerosensory area from gracile fasciculus

misinterpretation of pain location resulting from convergence of neural pathways in the CNS; the brain assumes signals are from the skin because it has more receptors and there is a higher frequency of signals coming from the skin

referred pain

what makes pain so variable for different people

conscious perception in the brainlm;;l;l;;l;;;

CNS has analgesic mechanisms and in states of stress of exercise, the body secretes what

endogenous opioids

what are the endogenous opioids

enkephalins, endorphins, and dynorphins

produced by CNS, pituitary gland, digestive tract and other organs

endogenous opiods

where are endogenous opiods primarily found in

central gray matter of midbrain and dorsal horn of spinal cord

how do endogenous opiods act as neuromodulators

block transmission of pain signals and produces feelings of pleasure/euphoria

what actually prevents the pain signal from getting beyond the dorsal horn of the spinal cord

spinal gating

how is spinal gating accomplished

two pathways: descending analgesic fibers and pain-inhibiting interneurons of dorsal horn

what is the descending analgesic fibers from the brainstem in regards to spinal gating

travels down reticulospinal tract to dorsal horn and blocks pain signals from traveling up the cord

what is the purpose of the pain-inhibiting interneurons of the dorsal horn in regards to spinal gating

receives input from mechanoreceptors in skin and deeper tissues

what are designated as chemical senses

taste and smell

what occurs after environmental chemicals stimulate sensory cells and trigger nerve signals

accept or reject food, activate gastric secretion and blood flow for digestion, stimulate insulin secretion for metabolism

what are the four types of lingual papillae on the tongue

filiform, foliate, fungiform, vallate

what lingual papillae of the tongue has a sense of texture and is the tiny spikes on the tongue

filiform

what lingual papillae of the tongue has a sense of taste and forms the parallel ridges on the sides of the tongue

foliate

what lingual papillae of the tongue has a sense of taste and texture and is found at the tips and sides of the tongue

fungiform

what lingual papillae of the tongue has a sense of taste and is found at the rear of tongue and is arranged in a V; only 7-12 but contain ½ of the taste buds

vallate

what 50-150 cells make up a taste bud

taste (gustatory cells), supporting cells, and basal cells

tuft of microvilli called taste hairs that are receptor surfaces and contains taste pores (pit where hairs project); are epithelia cells not neurons

supporting cells

stem cells that multiply and replace taste cells that have died and synapse with sensory nerve fibers

basal cells

taste type that is produced by metal ions (sodium/potassium); are vital electrolytes and mammals crave it when it is low

salty

taste type that is associated with high carbs and caloric value; plants have evolved to be enticing

sweet

taste type caused by amino acids and is craved by humans to motivate protein intake; aspartic and glutamic acid, monosodium glutamate

umami

taste type caused by acids and citrus; is typically for safety and protection

sour

taste type produced by alkaloids that are toxic, nicotine, caffeine, morphine; typically results in the rejection of a food, low threshold

bitter

what do some people believe there is a possibility to taste

oleogustus (fat) and clean water

what is flavor and taste influenced by

texture, temp, visual appearance, current state of mind, and aroma

what three cranial nerves do taste buds stimulate

facial nerve in anterior 2/3 of tongue, glossopharyngeal in posterior 1/2, and vagus in palate, pharynx, and epiglottis

where do all taste fibers project to

solitary nucleus in medulla

for taste, where do second order neurons travel to from the medulla

hypothalamus and amygdala to activate autonomic reflexes, or the thalamus then to the postcentral gyrus of cerebrum for conscious sense of taste

a response to airborne chemicals/ odorants

smell/olfaction

patch of epithelium that contains receptor cells for olfaction and is poorly ventilated but highly sensitive

olfactory mucosa

neurons with 10-20 immobile cilia that bind odor molecules in a thin layer of mucus and axons pass through the cribriform plate

olfactory cells

what are the only neurons in the body directly exposed to the external environment

olfactory cells

what cells are responsible for dividing

basal cells

what occurs during step 1 for the sense of smell

molecules bind to receptor on olfactory hair and could be hydrophilic or hydrophobic

if the molecule that binds to the olfactory hair is hydrophilic, what happens

diffuses through the mucus

if the molecule that binds to the olfactory hair is hydrophobic, what happens

transported by odorant-binding protein

what occurs during step 2 for the sense of smell

activation of G protein/cAMP system to open ion channels for Na+ and Ca+

what occurs during step 3 for the sense of smell

AP travels to the brain with receptors adapting quickly and nociceptors of the trigeminal nerve

where does the olfactory cortex also send feedback to

olfactory bulbs

how does the olfactory cortex send feedback to the bulbs

travels by granule cells in olfacotry cortex and synapse in glomeruli

what is the effect of the feedback on olfactory bulbs

can change quality and significance of a smell under different conditions; being ill vs being hungry