SENSATION, PERCEPTION, ATTENTION BLOCK 2: PART 2.2

what does olfaction inform us about? 2 pts

1. approaching an external object

2. avoiding an external object

receptors: nose and olfactory muscosa? 5 pts

1. the mucosa is a small region located high in the nasal cavity containing the olfactory receptors found below the olfactory bulb

2. odarant molecules are carried into the nose in an air stream which brings these molecules in contact with the mucosa

3. the olfactory receptor neurons in the mucosa are dotted with olfactory receptors that are senstive to chemical odorants

4. there are 350 types of olfactory receptors each sensitive to a particular group of odorants

5. the large number of olfactory receptors is important because it is a reason we can identify 100,000+ different odors

nose and olfactory mucosa physiological basis of sensation? 6 pts

1. olfaction starts in the nose where the air particles are collected

2. odorant molecules enter in contact with the olfactory mucosa which contains olfactory receptors

3. olfactory receptor neurons (ORNs) in the mucosa are dotted with olfacatory receptors that are senstive to 350 types of chemical odorants

4. activation of receptors in the mucosa causes electrical signals in the ORNs that are distributed across the mucosa

5. the ORNs send signals to structures called glomeruli inthe olfactory bulb

6. the axons of the bipolar olfactory cells constitute the olfactory nerve that contains afferent nerve fibers of olfactory receptor neurons transmitting nerve impulses about odors to the central nervous system where they are perceived by the sense of smell

characteristics of the olfactory bulb? 3 pts

1. mitral cells are locared in the olfactory bulb in the brain whose axons transfer info to the areas in the brain including the piriform/primary olfactory cortex, the orbitofrontal cortex, and the amygdala

2. the olfactory system is the only human sense that bypasses the thalamus and connects directly to the forebrain

3. the amygdala is associated with emotions and plays a role in the emotional reactions that odors can elicit

how do taste and olfaction influence the perception of flavour? 1 pt

odorant molecules released by food in the oral cavity travel through the nasal pharynz to the olfactory mucosa in the nasal cavity resulting in the perception of the flavor of food (taste and smell)

five basic taste qualities? 5 pts

1. sweetness- associated with substances with nutritive value

2. bitterness-associated with potentially harmful subastances

3. saltiness- indicates the presence of sodium

4. sour

5. umami- described as a meaty, frothy, savory taste

receptors on the human tongue? 4 pts

1. filiform- shaped like cones and are found over the entire surface of the tongue giving it its rough appearance

2. fungiform- shaped like mushrooms and are found around the tip and sides of the tongue

3. foliate- a series of folds along the bacl of the tongue on the sides

4. circumvallete- shaped like flat mounds surrounded by a trench and are found at the back of the tongue

how many taste buds are found on the tongue and where? 1 pt

there are about 10K tastebuds that each contain 50-100 taste cells that are found on all the papillae except the filiform meaning stimulation of the back or perimiter of the tongue rather than the central result in a broad range of taste sensations

what is transduction? 1 pt

occurs when chemicals contact receptor sites located on the tip of these taste cells resulting in the generation of electrical signals in the taste cells that are transmitted from the tongue in a number of different nerves

pathway from taste buds to the cortex? 4 pts

taste info will be transmitted to the nucleus of the solitary tract located in the medulla O via a 3 way or 3 cranial nerves (VII, IX, X)

1. facial nerve pathway (VII)- transmits info from the anterior part of the tongue

2. glossopharayngeal nerve pathways (IX)- transmits info from the back of the tongue

3. vagus nerve pathway (X)- transmits the info mrom the palate and the epiglottis

once this info reaches the nucleus of the solitary tract it projects to the posterior medial ventral nucleus (VMP) of the thalamus and from there the info will travel to the primary gustatory cortex located in the insulated and opercular frontal cortex

parts of the somatosensory system? 3 pts

1. cutaneous senses- responsible for the perceptions such as touch and pain that are caused by stimulation of the skin

2. proprioception- ability to sense the position of the body and limbs

3. kinaesthesia- ability to sense the movement of the body and limbs

types of stimuli: skin stimulations? 1 pt

external mechanical energy that in contact with the skin gives rise to sensations of touch (minimal force that generates a small distortion in skin), pressure, or vibration.

types of stimuli: proprioceptive and kinesthetic stimuli? 3 pts

1. internal mechanical energy that is generated by the position or movement of a part of the body

2. the position of the different parts of the body are indicated by the static force of joints, muscles, and tendons to maintain theis position against gravityy

3. the movement of a part of the body is indicated by dynamic changes in the force applied to muscles, tendons, and joints

types of stimuli: painful stimuli? 1 pt

internal or external mechanical energy that gets harmful to the tissue and can be triggered by the sensation of contact with a painful stimulus or as a result of inflammation of a tissue

what is skin? 5 pts

a sensory organ that serves a protective function and prevents the evaporation of organic fluids and is composed of two layers:

1. epidermis- surface epithelium of the skin overlying the dermis consisting of a layer of tough dead skin cells

2. dermis- thick layer of living tissue below the epidermis which forms the trus skin containing blood capillaries. nerve endings. sweat glands, hair follicles, and other structures

3. hypodermis- not considered a part of the skin and is the deepest later formed by connective tissue attached to the dermis and fat cells

mechanoreceptors that respond to mechanical stimulation are found in the epidermis and the dermis layers of the skin

types of touch receptors: mechanoreceptors? 3 pts

1. receptors sensitive to mechanical deformations of the skin (flexion, pressure, stretching) and to the temporal dimensions of these transformations

2. consists of the Meissner and Pacini corpuscles, Ruffini cylinders, Merkel receptors, and hair follicle receptors

3. they have different locations, receptive fields, and response times

types of touch receptors: nociceptors? 3 pts

1. free nerve endings located just below the epidermis

2. spread all over the body except in the brain

3. respond when damage (excessive pressure, excessive heat/cold, harmful chemicals) occurs in the tissues they are inserted in

types of touch receptors: thermoreceptors? 4 pts

1. free nerve endings near the epidermis

2. sensitive to temperature exchanges between the body and the outside

3. detect sudden changes and adapt over time

4. divided into heat detectors (30-45 degrees and above 45 degrees) and cold detectors (10-35 degrees)

types of touch receptors: proprioceptors? 3 pts

1. respond to changes produced by body movement

2. inform about the internal environment; the relative position of the differnt parts of the body and its movements

3. located in the muscles, tendons, and ligaments to respond to mechanical deformations of these tissues

mechanoreceptors: merkel receptor and meissner corpuscle? 2 pts

located close to the surface of the skin near the epidermis and respond to a pressure stimulus that is presented and then removed

1. merkel receptor- fires continously as long as the stimulus is on; senses fine detials (touch-mild pressure)

2. meissner corpuscle- fires only when the stimulus is first applied and when it is removed; senses controlling handgrip (touch-pressure)

mechanoreceptors: ruffini cylinder and pacinian corpuscle? 2 pts

located deeper in the skin and respond to pressure stimulus that is presented then removed

1. ruffini cylinder- responts continously to stimulation; senses stretching of the skin (touch-pressure-heat-pain)

2. pacinian corpuscle- responds when the stimulus is applied and removed; senses rapid vibrations and fine texture (touch-pressure-vibrations)

where are the bulbs of Krause (mechanoreceptors) located? 1 pt

between the skin and the mucous membrane

which receptors adapt quickly over time? 1 pt

meissner receptors and pacinian corpuscles react only to changes

which receptors adapt slowly over time? 1 pt

merkel receptors and ruffini cylinders fire APs as long as the stimulus continues

pathways from skin to cortex? 3 pts

nerve fibers from receptors in the skin travel in bundles(prepheral nerves) that enter the spinal cord through the dorsal root

1. medial lemniscal pathway- has large fibers that carry signals related to sensing the positions of the limbs and perceiving touch

2. spinothalamic pathway- smaller fibers that transmit signals related to temperature and pain

3. fibers from both pathways cross ober to the other side of the body during their upward journey to the thalamus

4. must of these fibers synapse in the ventrolateral nucleus in the thalamus but some synapse in the other thalamic nuclei

5. because signals in the spinal cord cross over to the opposite side of the body on their way to the thalamus meaning signals originating from the left side of the body reach the thalamus in the right hemisphere of the brain and vice versa

maps of the body on the cortex? 3 pts

1. from the thalamus signals travel to the somatosensory receiving area (S1) in the parietal lobe of the cortex and possibly to the secondary somatosensory cortex (S2)

2. signals also travel between S1 and S2 and vice versa to additional somatosensory areas

3. the homunculus shows that some areas of the brain are represented by a disproportionately large area of the brain

sensory homunculus on the somatosensory cortex? 1 pt

parts of the body with the highest tactile acuity area represented by larger areas on the cortex

the somatosnesory cortex in the parietal lobe? 2 pts

1. S1 primary somatosensory area receives inputs from the ventrolateral nucleus of the thalamus

2. S2 secondary somatosensory area partially hidden behind the temporal lobe

what is experience dependent plasticity? 1 pt

when the cortical representation of a particular function becomes larger when that function is used often

types of nerve fibers? 5 pts

A-fibers are large and myelinated so their conduction velocity is greater (spinal nerves)

1. A-alpha fibers- proprioceptive info

2. A-beta axons- touch sensations are transmitted

3. A-delta fibers - mechanical and thermal pain info

C-fibers are small and unmyelinated so they have a lower conduction velocity (50% of sensory fibers)

1. C fibers- mechanical, thermal, and chemical pain

three types of pain? 3 pts

1. nociceptive pain- caused by the activation of nocicpetors in the skin that respond to different stimuli (heat, chemical, severe pressure, cold)

2. inflammatory pain- caused by damage to tissues and inflammation to joints or by tumor cells

3. neuropathic pain- cuased by lesions or other damage to the nervous system e.g. capral tunnel syndrome caused by repetitive tasks, spinal cord injury, brain damage

what is the direct pathway model of pain? 1 pt

this theory states that pain is caused by signals sent directly from the skin to the brain; when pain occurs nocicpetors are sitmulated and send their signals to the brain

how does phantom limb pain occur? 1 pt

cutting nerves that used to transmit signals form the limb to the brain has been found not to eliminate pain meaning pain originates in the pain since signals are send from the remaining amputation/limb

two things that can affect pain? 2 pts

1. a person’s mental state

2. a person’s attention

gate model model? 5 pts

1. pain signals enter the spinal cord from the body and are then transmitted from the spinal cord to the brain

2. proposes that there are additional pathways that influence the signals sent from the spinal cord to the brain

3. signals from these additional pathways can act to open or close a gate located on the spinal cord that determines the strength of the signal leaving the spinal cord

4. this system consists of cells in the spinal cord called the substantia gelatinosa that are activated when pressure is applied to the area that hurts

5. input along the gate control system occurs along the S-fibers, L-fibers, and central control fibers

S-fibers? 4 pts

1. small diameter fibers associated with nociceptors

2. activity in S-fibers increase the activity of the transmission cel/T-cell

3. intensity of pain is determined by the amount of T-cell activity; more activity more pain

4. signals from S-fibers always excite T-cells and therefore increase pain

L-fibers? 4 pts

1. larger in diameter and carry info about non-painful tactile stimulation e.g. signals from rubbing the skim

2. activity in L-fibers can send inhibition to the T-cells

3. signals that pass through SG activate an inhibitory synapse

4. this closes the gate decreasing T-cell acitivty and subsequently decreases pain

central-control? 2 pts

1. contain info related to cognitive functions e.g. expectation, attention, distraction

2. as with L-fibers activity coming down from the brain also closes the gate and decreases T-cell activity and decreases pain

what determines the perception of pain? 1 pt

a balance between the input from the nociceptors in the skin and nociceptive activity from the skin and the brain

who proposed the gate control theory and why? 2 pts

1. melzack and wall (1965)

2. to describe a process of inhibitory pain modulation at the spinal cord level