week 5

Question 1

What is sensation

Answer 1

stimulation occurs through tactile, auditory, visual and chemical sensation
Specialised receptors dedicated to each sensation

Question 2

What is perception

Answer 2

this information is then sent to the brain, where processing takes place

Question 3

What mechanical senses are they

Answer 3

Vestibular sensation
Somatosensation: touch, temperature, pain, proprioception

Question 4

What is vestibulation

Answer 4

made up of receptors in inner ear that respond to body position and movement/tilt of head
This information is used alongside our other senses in order to perceive what is happening
Aids in balance which is why ear infections result in loss of balance and dizziness

Question 5

What are the organs in the vestibulation system

Answer 5

The semicirular canals: 3 canals filled with fluid with hair cells in it
The otolith organ: utricle and saccule-different orientations

Question 6

What is the semicircular canals

Answer 6

3 canals filled with fluid (endolymph) with hair cells in it
movement causes endolymph to move against hair, being the hair
Oriented on 3 planes- stimulation gives brain information about the movement of head

Question 7

What is the Otolith organs

Answer 7

these send messages about our position in 3D space
they are sensitive to acceleration, deceleration and direction changes
Comprised of utricle and saccule-different orientations (similar to the endolymph but they are glutinous)

Question 8

What is vestibular pathway

Answer 8

vestibular afferent fibres-vestibular nuclei in medulla and pons- to cerebellum, nuclei of cranial nerves and ventral posterior thalamus to vestibular area of S1

Question 9

What are key aspects of somatosensation

Answer 9

Senses of the body
Several different modalities:
Hapsis (fine touch/pressure), Kinesthesis, vestibular (movement, position and spatial orientation/balance), proprioception (awareness of our body in space), temperature and pain

Question 10

Somatosensory-or ‘touch’

Answer 10

20 different types of neurons
in all parts of body (except brain) vary in density and sensitivity to stimuli

Stimuli inside the body: interceptors and proprioceptors
Stimuli outside the body: exteroceptors

Question 11

Skin

Answer 11

2 types-hairy and glabrous (hairless)
Glabrous is very sensitive because we use it to explore objects
Functions: protective function, prevents evaporation of bodily fluids and provides direct contact with the world
Sensitivity: 2-point sensitivity test, how close get and still perceive both and weaker in hairy skin

Question 12

What is discriminative touch

Answer 12

this is what we normally mean when we discuss touch: stimuli from and body tissue

Facilitated by specialised touch receptors with different structures: Only surface of sensory dendrites or other tissue

Question 13

Hapsis

Answer 13

there are receptors on your skin which detect vibration and pressure: these are ‘touch receptors’ and detect fine touch/pressure

The sensation of pressure is referred to as ‘hapsis’, so receptors dedicated to pressure are called haptic receptors (also tactile receptors)

Question 14

Layers of skin

Answer 14

Epidermis= top layer contains cells that produce pigment and protect immune system

Dermis= contains much of our nerve endings, oil and sweat glands and hair follicles

Subcutaneous tissue=fat, connective tissue and blood vessels within are different sensory receptors, differences in tissue determines the kind of energy transduced by the receptor to the nerve

Question 15

Hair receptors

Answer 15

dendrite attached to hair on your skin, as an object moves across the skin, these hairs move sending a nerve impulse

Question 16

Cutaneous receptors

Answer 16

cutaneous receptors encapsulated (surrounding by a capsule ) or unencapsulated (includes free nerve endings)
Free nerve endings: most common in skin; different forms, dendrite of sensory neuron, Polymodal sensitive to painful stimuli, to hot and cold and to light touch, slow to adjust to stimulus

Question 17

What types of mechanoreceptors are there

Answer 17

Pacinian corpuscles
Ruffini’s corpuscles
Merkel’s disks
Meissner’s corpuscles

Question 18

Pacinian corpuscle

Answer 18

the specific capsule involved in pressure detection; important for detecting deep touch and vibration, rapidly-adapting involves both superficial and deep layers and hair

Found in both glabrous and hairy skin

Question 19

What is Ruffini’s corpuscle

Answer 19

Also found deep in dermis and subcutaneous tissue, also found in both glabrous and hairy skin

Sensitive to stretching/sustained deep touch: slow adapting

Question 20

What is Merkel’s disk

Answer 20

Unencapsulated
Found in epidermis and deeper, also found in both glabrous and hairy skin

Tonic receptors: sustained light touch-slow adapting

Question 21

Meissner’s corpuscle

Answer 21

Encapsulated receptor; found high within dermis
particularly in glabrous skin and finger pads

Rapidly-adapting, sensitive to light touch
sensitive to shape and textural changes in exploratory and discriminatory touch

Question 22

Temperature and pain

Answer 22

Nociceptors- detect pain and temperature
Thermoreceptors- separates hot from cold

Question 23

What is affective touch

Answer 23

touch plays an important role in many forms of social communication

Low threshold receptors in hairy skin: slower touch system, includes pleasant touch, as well as pain, temperature and itch

Question 24

Proprioception

Answer 24

Location and movement of body
Proprioceptors are encapsulated nerve endings, sensitive to the stretch of muscles/tendons and joint movement: fastest fibres

Question 25

Kinesthesis

Answer 25

Sensation of muscles, tendons and joint moving
allows coordinated movement

Question 26

What effect does ageing have on senses

Answer 26

young- full tactile ability
Aged- tactile defect

Question 27

Receptor specialisation- 2 systems

Answer 27

Rapidly adapting receptors:
produce burst of action potentials, involved in detecting discriminate touch and fluttering

Question 28

what is the second system

Answer 28

Slowly adapting receptors : light pressure- when clothing is on, only these remain active
Firmer pressure: Ruffini corpuscle= vibration due to stretching
Stimulated in different ways and to way ion channels in the membrane of the dendrite respond to mechanical stimulation

Question 29

What is the pathway to the brain

Answer 29

Receptors carry somatosensory info to neuron’s cell body located just outside spinal cord: contains single long dendrite with only tip responsive to sensory stimuli

Each segment of spinal cord has one dorsal root per side with many dorsal-root ganglion neurons

Question 30

Touch and pain: different travel speeds

Answer 30

Haptic and proprioception carried by large, well- myelination axons: Type A fibres

Nociceptive info: temperature, pain, tickle, itch: carried by smaller axons, with little or no myelination: type C fibres
Certain fast pain carried by myelinated ‘type A fibres

Question 31

Different pathways for touch and pain

Answer 31

Touch information ascends spinal cord ipsilaterally via the dorsal column medial lemniscal pathway

Nociceptive information ascends contralaterally via the spinothalamic pathways

Question 32

Pathway to the brain (haptic-proprioception)

Answer 32

Axons located in dorsal portion of spinal cord
synapse at base of brain in dorsal-column nuclei
These then cross to other side of brainstem through medial lemniscus
Synapse in ventrolateral thalamus
sends most axons to somatosensory cortex but some to motor cortex too

Question 33

Pathway to the Brain (Nociception)

Answer 33

axons in synapse in dorsal part of spinal cord’s grey matter
Neurons send axons to ventral part of other side of spinal cortex
Some also send information to the somatosensory cortex: Conscious, sensory aspects of pain, also to insular and anterior cingulate cortex

Question 34

Somatosensory cortex

Answer 34

primary somatosensory cortex in postcentral Gyrus: BA 3b

Other areas: BA 1 and 2 of postcentral Gyrus, Posterior Parietal cortex

Lesions impair somatic sensations

Question 35

Pain

Answer 35

2 types: chronic (long-term) and acute (short-term)

Has adaptive value-usually trying to tell you something:
Those without nociceptors deformity through failure to adjust posture, also experience acute injuries because of failure to avoid harmful situation

Question 36

Pain receptors

Answer 36

Peptides and other chemicals released by cells when damaged/irritated: some irritated surrounding tissue , stimulating chemical release, excites free nerve endings that function as nociceptors, this stimulated blood flow and pain fibres and reason we experience pain, redness and swelling

Haptic info contributes to pain sensation

Question 37

What is Gate theory

Answer 37

Can inhibit pain through:
Pain gates in: spinal cord (countered via epidural), brainstem (countered via electrical stimulation), cortex (countered via distraction)

Question 38

What is thermoregulation

Answer 38

Homeostatic function
operates through automatic response of hypothalamus and behavioural responses
The hypothalamus contains temperature-sensitive neurons

Hypothalamus integrates information with input from skin receptors: releases pituitary hormones to regulate energy, metabolism and production

Question 39

What is the response to temperature change

Answer 39

Heat: rate metabolic activity decreases, blood vessels dilate to transfer
Heat to body surface: sweat production and evaporation increase, triggering thirst and panting

Cold: increases secretion of thyroid hormones: increases discharge of sympathetic nervous system, shivering, piloerection, blood vessels constrict to reduce heat loss