Chapter 16 Flashcards
What is a sensation, a stimulus, a receptor, and a sense organ?
sensation= Conscious perception of a stimulus
stimulus= change in the environment
receptor= cell or organ that detects a stimulus
sense organ= combines nervous tissue with other tissues that enhance its response to a sitmulus
What are the requirements for a sensation to be perceived?
Requirements: stimulus, receptor, afferent nerve,
translation in the CNS
What are the general properties of receptors?
General properties: transduction, local potential,
modality, adaptation
What is a receptive field?
receptive field= part of the sensory neuron that detects stimuli
the smaller the receptive field, the easier it is to feel and identify things
EX: to determine if something is cotton or silk you would be more successful feeling it with your fingers than forearms because the receptive fields are smaller.
What is sensory adaptation?
reduction in sensitivity to a sitmulus after constant exposure to it
How are receptors classified based on the stimulus modality, the origin of stimulus, and receptor distribution?
By stimulus modality:
Thermoreceptors (respond to heat and cold), photoreceptors, (the eyes, respond to light) nociceptors (pain receptors, respond to tissue injuries),
chemoreceptor (respons to chemicals), and mechanoreceptors (respond to physical deformation of a cell or tissue cause by vibration
By origin of stimulus:
Exteroceptors: detect external stimuli
Interoceptors: detect internal stimuli
Proprioceptors: sense body position and movements
By receptor distribution:
General (somesthetic) senses: widely distributed
Special senses: limited to head
* Vision, hearing, equilibrium, taste, and smell
What is somatosensory projection pathways, what are first, second and third order neurons?
somatosensory projection pathways= the pathways followed by sensory signals to their final destinations in the CNS
first order (afferent neuron)= conducts a pain signal to the spinal cord, all the signals in the face and head region travel directly to the brain stem.
second-order neurons= always carried the message to the thalamus
third order= message goes to the cerebral cortex, relays the message
What is pain? What main chemical is released by the injured tissues?
Pain= uncomfrotable perception of tissue injury, it’s a function for peopel to avoid or escape danger
Seratonin is the main chemical released by injured tissue
What are the receptors for pain sensation? Know the projection pathways for pain.
Nocieptors arethe receptors for pain reception
Protection pathways for pain:
A needle pokes the finger, the nocioceptors send that pain signal through to the first order into the spinal cord. It goes through the spinal cord to the second order nerve fibers and than to the third order to the thalamus
What is a referred pain and what causes referred pain?
Referred pain is when there is pain in the viscera often mistakenly thought to come from the skin
It results from the convergence of neural pathways in the CNS
What is CNS modulation of pain?
CNS modulation of pain is how the central nervous system regulates pain
Uses Neuromodulators (endogenous opioids and enkephalins) which block transmission of pain signals which produces feelings of pleasure and euphoria
Another way of blocking pain signals is by rubbing or massaging the injury
see diagram
1) Nocioceptor releases substance P onto spinal interneuron
2) Second order neuron sends signals to the thalamus
3) third order neuron relays signal to someshetic cortex
4) Input from hypothalamus and cerebral cortex combines onto central gray area of the mid brain
5) Midbrain relays signal to medulla oblongata
6) analgesic fibers secrete serotnin onto spinal interneurons
7) spinal interneurons secrete enkephalins which block pain transmission
8) other analgesic fibers block pain transmission by means or presynaptic inhibition
What are analgesics? What are the different ways to block pain?
Anesthesia= local and general anesthesia
Analgesia= examples are morphine and laudanum. Blocks pain selectively
Electrical stimulation
What is spinal gating (role of substance P, serotonin and enkephalins)? Why does massaging relieve pain?
Spinal gating is a way to block and relieve pain
substance P= a neurotransmitter for pain
serotonin=
enkephalins= two analgesic oligopeptides that have 200 times the potency of morphine
endorphins and dynorphins are the larger analgesic neuropeptides
massaging relieves pain because Rubbing stimulates mechanoreceptors which
stimulates spinal interneurons to secrete
enkephalins that inhibit second-order pain neurons
What are the chemical senses?
gustation and olfaction
How are the tastes and smell receptors stimulated?
taste= stimulated by saliva and tongue
smell= nasal fluids
both chemoreceptors
What are the receptors for taste and smell where are they located?
The are Chemoreeptors= help us perceive chemicals in the environment. They are on the tastebuds and nasal cavities.
What are the anatomy and physiology of Gustation and olfaction (type of cells with their functions)?
gustation (tasting) olfaction (smelling)
Gustation: the visible bumps on the tongue are not taste buds, they are lingual papillae.
Olfaction: scent is the strongest sense tied to memory
Odorant molecules bind to membrane receptor on
olfactory hair
– Hydrophilic: diffuse through mucus
– Hydrophobic: transported by odorant-binding protein in mucus
Activate second messenger system
* Opens ion channels for Na+ or Ca2+
– Depolarizes membrane and creates receptor potential
– Triggers AP in axon of olfactory cells
– Signal is transmitted to brain
– Some odorant act on nociceptors of trigeminal nerve
What are the different type of lingual papillae?
The four types of papillae are filiform papillae (tiny spikes, most abundant, small, function as the sense of texture of foods.) foliate papillae (weakly developed in humans, where most chemicals are released from foods). Fungiform papillae ( mushroom-shaped, function to taste and also food texture) Vallate papillae (large in rear of tongue, contain half of all taste buds
What are the different types of taste and where are their taste buds located?
located in the papillae, half of them are in the valate papillae
What is the nerve supply and projection pathway for the sense of taste and smell?
taste- Facial (VII) nerve: from taste buds over anterior two-thirds of
tongue
* Glossopharyngeal (IX) nerve: from posterior one-third of
tongue
* Vagus (X) nerve: from taste buds of palate, pharynx, and
epiglottis
* All fibers reach solitary nucleus in medulla oblongata
* These impulses then travel to the thalamus and from there
fibers branch to the
– Gustatory cortex (taste)
– Hypothalamus and limbic system (appreciation of taste)
* Sent on to orbitofrontal cortex to be integrated with signals from nose
and eyes; form impression of flavor and palatability of food
see diagram
smell (olfactory) - olfactory signals received in olfactory bulbs, signals relayed in olfactory tracts, primary olfactory cortex in temporal lobe creates a conscious perception of odor and relays signals to other brain destinations, signals from each temporal lobe are relayed to the contralateral temporal lobe, signals relayed to the amygdala, hippocampus, insula, hypothalamus relate the odor to olfactory memory which produces emotional responses to the odor, signals received in orbitofrontal cortex combine with other information to identify and discriminate among odors and integrate the odor into a flavor, feedback to olfactory bulb modulates perception of odor according to circumsatndes.
