Somatosensory, Vestibular and Olfactory systems

Question 1

define stimulus

Answer 1

energy source Internal External 

Question 2

define receptor sense organ

Answer 2

structures specialized to respond to stimuli 

Question 3

define transducers

Answer 3

-stimulus energy converted into action potentials

Question 4

deine conduction

Answer 4

Afferent pathway Nerve impulses to the CNS

Question 5

how amny epidermal cells do humans shed a day?

Answer 5

50 million

Question 6

outline the skin

Answer 6

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!)

Question 7

what are the 4 types of touch receptors?

Answer 7

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

Question 8

what is the receptive field?

Answer 8

“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”

Question 9

what effects the RF’s spatial resolution

Answer 9

Size: Smaller RF à Higher Resolution Density: Higher Density à Higher Resolution

Question 10

ouline the Ascending nervous pathway

Answer 10

afferent sensory information enters CNS
Innervation via Spinal Nerve
effeent signles to muscles and glands via ventral root

Question 11

what is the dorsal horn and ventral root?

Answer 11

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.

Question 12

name the mapping of the sesnory system

Answer 12

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

Question 13

outline the ascending pathway

Answer 13

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)

Question 14

where is somatosensory cortex one?

Answer 14

by the cetral sulcus

Question 15

what does the somatosensory cortex do for mapping?

Answer 15

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

Question 16

what is pain?

Answer 16

“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

Question 17

what is a Nocioreceptor?

Answer 17

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

Question 18

what are the key feature of Nocioreceptors?

Answer 18

Nociceptors respond to noxious stimuli Nociceptors are found in: • skin • muscle • joints • and some visceral tissues

1. some are specificto one type of stimulus, such as: -mechanical (Mechano-sensitivenociceptors) -thermal (Thermo-sensitivenociceptors)
2. 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

Question 19

what is the differecne betwee nA fibers adn C fibers?

Answer 19

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

Question 20

explain the pain acending pathway

Answer 20

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

Question 21

what is the pain matrix and central mechnaisms for pain?

Answer 21

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

Question 22

what is the vestibular system?

Answer 22

The vestibular system answers 2 questions basic to the human condition: where I am? which way is up

Question 23

what are two important parts of the vestibular system?

Answer 23

Semicircular Canals- head angular acceleration

Otoliths head linear acceleration gravity

Question 24

where are the vestibular organs?

Answer 24

on the temporal bone

Question 25

what are the semicircular canals?

Answer 25

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

Question 26

what are Otoliths

Answer 26

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.

Question 27

explain hypoerpolarization or depolarization of the vestibular system

Answer 27

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

Question 28

what is the Ascending Vestibular Pathway?

Answer 28

``` ongitudinal fasciculus to the brain Ascending pathway - Vestibular Nerve Brainsterm (Cerebellum) Thalamus Vestibular Areas ```

Question 29

what are the vestibular brain areas?

Answer 29

No Primary Vestibular Cortex Vestibular Network in the Brain Somatosensory Cortex,Premotor Cortex, Anterior Insula, Posterior Parietal Cortex, Temporo-Parietal Junction (TPJ), Hippocampus

Question 30

what are the three vestibular reflexes?

Answer 30

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

Question 31

explain the VOR

Answer 31

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

Question 32

what does the VSR do?

Answer 32

VSR à areflexbody movement that maintains your posture and stabilizes your body VSR keeps you upright

Question 33

outline smell adn taste

Answer 33

Involve chemoreceptors Respond to chemicals in aqueous solutions Chemicals dissolve in mucus of nose & saliva in mouth

Question 34

outline smell

Answer 34

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

Question 35

what is the smell pathway?

Answer 35

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

Question 36

outline the types of taste receptors we have

Answer 36

``` 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 ```

Question 37

Give the taste pathway

Answer 37

``` TASTE PATHWAY Signals from the taste receptors Medulla Thalamus Gustatory Cortex (in Insula) ```