Somatosensory, Vestibular and Olfactory systems Flashcards
define stimulus
energy source Internal External
define receptor sense organ
structures specialized to respond to stimuli
define transducers
-stimulus energy converted into action potentials
deine conduction
Afferent pathway Nerve impulses to the CNS
how amny epidermal cells do humans shed a day?
50 million
outline the skin
Glabrous Skin Smooth, thick skin on palms and soles of our feet
Epidermis = 1.5 mm
Dermis = 3 mm
Hairy Skin Thin skin populated with hair follicles Epidermis = 0.1 mm Dermis = 1-2 mm
Sweat Glands Eccrine – secrete saline (heat regulation) Sebaceous – secrete complex cell cytoplasm (Primary source of human body odor!)
what are the 4 types of touch receptors?
Meissner corpuscle -Touch Small receptive fields Fast adapting
Merkel cells - Touch Small receptive fields Slow adapting
Ruffinin ending -Stretch Large receptive fields Slow adapting
Pancininan corpuscle Vibrations Large receptive fields Fast adapting
what is the receptive field?
“The receptive field (RF) of an individual sensory neuron is the particular region of the sensory space in which a stimulus will modify the firing of that neuron”
what effects the RF’s spatial resolution
Size: Smaller RF à Higher Resolution Density: Higher Density à Higher Resolution
ouline the Ascending nervous pathway
afferent sensory information enters CNS
Innervation via Spinal Nerve
effeent signles to muscles and glands via ventral root
what is the dorsal horn and ventral root?
DORSAL HORN = Afferent sensory information VENTRAL HORN = Efferent motor signals
Bell-Magendie Law
The fact that anterior spinal nerve roots contain only motor fibers and posterior roots only sensory fibers.
Dorsal: signals to brain
Ventral: motor-efferent pathway transmits motor information from brain to body.
name the mapping of the sesnory system
Dermatome: Adermatomeis an area of skin that is mainly supplied by a single spinal nerve Although there are 31 pairs of spinal nerves in humans, there are only 30 dermatome
outline the ascending pathway
Tactile signals are sent through the spinal cord via the dorsal column pathway to the primary somatosensory cortex (S1) in the brain Ascending pathway
TACTILE PATHWAY Dorsal column Thalamus Primary somatosensory cortex(S1) Secondary somatosensory cortex(S2) Other brain areas (parietal areas)
where is somatosensory cortex one?
by the cetral sulcus
what does the somatosensory cortex do for mapping?
Each part of the skin surface is represented by a specific region of primary somatosensory cortex somatotopy
“Sensory Homunculus” little man
The area devoted to each body part reflects the receptor density in that par
little man
The area devoted to each body part reflects the receptor density in that part
Cortical Magnification
The receptive fields and cortical representations give more acuity to fingers, mouth, nose and tongue
what is pain?
“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” The International Association for the Study of Pain
Pain and touch are processed by separateneural systems Pain is detected by special receptors in the skin
what is a Nocioreceptor?
Nociceptors are free nerve endings that respond to stimuli that can cause tissue damage or when tissue damage has taken place Small diameter afferent neurons(with A-delta and C-fibersreceptors
what are the key feature of Nocioreceptors?
Nociceptors respond to noxious stimuli Nociceptors are found in: • skin • muscle • joints • and some visceral tissues
- some are specificto one type of stimulus, such as: -mechanical (Mechano-sensitivenociceptors) -thermal (Thermo-sensitivenociceptors)
- but most are polymodal (respond to many stimuli, including chemicals) 3. the number and size of the receptive fields served by each fibermay be small or large, respectively
what is the differecne betwee nA fibers adn C fibers?
Aδ Fiber What they transmit: Sharp, Prickly Pain Characteristics: Thin, Myelinated, Fast
What they transmit: Sharp, Prickly Pain Characteristics: Thin, Myelinated, Fast
Fast Pain Which fiber? Aδ Fiber Fast (first) pain is sharp, instantaneous, and tends to fade
C Fiber What they transmit: Dull, Aching Pain Characteristics: Thin, Unmyelinated, Slow
Slow Pain Which fiber?: C Fiber Slow (second) pain is delayed, dull, diffuse, and long-lasting
explain the pain acending pathway
Pain signals travel through the spino-thalamic tractto the brain and run parallel to somatosensory (dorsal column) pathways
Ascending pathway - PAIN
PAIN PATHWAY
Afferent to spinal cord laminae I & II Cross midline to contralateral
anterolateral column
Thalamus
Primary somatosensory cortex(S1)
Secondary somatosensory cortex(S2)
Anterior Cingulate Cortex, Insula, Amygdala
what is the pain matrix and central mechnaisms for pain?
SENSORY DISCRIMINATIVE
§ Somatosensory cortex (S1 & S2)
Mediate perception of location, intensity, and ”quality” of painful stimuli EMOTIONAL AVERSIVE
§ Amygdala, anterior cingulate cortex, insular cortex § Mediate perception of fear, anxiety, and unpleasantness of painful stimuli
what is the vestibular system?
The vestibular system answers 2 questions basic to the human condition: where I am? which way is up
what are two important parts of the vestibular system?
Semicircular Canals- head angular acceleration
Otoliths head linear acceleration gravity
where are the vestibular organs?
on the temporal bone
what are the semicircular canals?
Sense head rotations (angular acceleration)
Semicircular canals filled with liquid (endolymph) § Rotation of head cause liquid to move opposite to rotation
This bends the jelly-like cupula, causing embedded vestibular hair cells to bend and fire action potentials
PUSH & PULL
what are Otoliths
Sense linear acceleration & gravity Otoliths
The otoliths consist of hair cells embedded in a jelly-like substance, covered with heavy calcium carbonate crystals
Linear acceleration (e.g. tilting the head) cause the crystals to pull the gelatinous substance downward, bending hair cell stereocilia and causing depolarisation
People in space get sick because no vestibular information
No gravity can’t
Space adaptation syndrome= worst motion sickness ever.
explain hypoerpolarization or depolarization of the vestibular system
A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear
Bending toward kinocillium
DEPOLARIZ.
Bending away kinocilliu
what is the Ascending Vestibular Pathway?
ongitudinal fasciculus to the brain Ascending pathway - Vestibular Nerve Brainsterm (Cerebellum) Thalamus Vestibular Areas
what are the vestibular brain areas?
No Primary Vestibular Cortex Vestibular Network in the Brain Somatosensory Cortex,Premotor Cortex, Anterior Insula, Posterior Parietal Cortex, Temporo-Parietal Junction (TPJ), Hippocampus
what are the three vestibular reflexes?
Vestibular-Ocular Reflex keeps the eyes still in space when the head moves
Vestibular-Collic Reflex keeps the head still in space (or on a level plane when you walk)
Vestibular-Spinal Reflex adjusts posture for rapid changes in body position
explain the VOR
VOR eye movements that stabilize gaze by counteringmovement of the head
In VOR the semicircular canals measure rotation of the head and provide a signal for the oculomotor nuclei of the brainstem, which innervate the eyemuscles VOR allows maintaining gaze while rotating or moving head
what does the VSR do?
VSR à areflexbody movement that maintains your posture and stabilizes your body VSR keeps you upright
outline smell adn taste
Involve chemoreceptors Respond to chemicals in aqueous solutions Chemicals dissolve in mucus of nose & saliva in mouth
outline smell
Smell Receptors • Located in roof of nasal cavity • Non-motile cilia covered by mucus
• Axons go to the brain
• Lifespan approx. 30-60 days
• Each olfactory receptor has only one type of receptor protein which bind specific odorant molecules
1. Odorants bind with receptors
2. Olfactory receptor cells are activated and send electric signals (Action Potentials)
3. Signals arerelayed in glomeruli
4. Signals travel tobrain
Brain can analyze ~400 odor molecules We can recognize > 1 trillion odors
what is the smell pathway?
SMELL PATHWAY Signals from the olfactory nerve travel to the pyriform cortex
Neurons in pyriform cortex respond to odours
Amygdala (emotional response)
Thalamus
Orbitofrontal Cortex
outline the types of taste receptors we have
Taste Receptors • Taste buds –receptors with hairs covered by saliva • Most found in papillae • Lifespan = 7-10 days Five basic tastes Each triggered by different chemicals: 1. Sweet 2. Sour 3. Salty 4. Bitter 5. Savoury/umami 80% of taste is actually smell Interpretation of the stimuli is KEY
Give the taste pathway
TASTE PATHWAY Signals from the taste receptors Medulla Thalamus Gustatory Cortex (in Insula)
