Somatic Senses

Question 1

what are the 4 types of receptors ?

Answer 1

1- Mechanoreceptros
2-Thermoreceptors
3-Electromagnetic receptors (eyes)
4-Chemoreceptors

Nociceptors (are mechanoreceptors, thermoreceptors, chemoreceptors)

Proprioceptors (mechanoreceptors )

Question 2

what are the subtypes of mechanoreceptors

Answer 2

respond to stretch , distortion on the membrane

1) Tactile receptors of the skins ( fine or crude touch)
2) Deep tissue receptors
3) Proprioceptors
4) Baroreceptors
5) Inner ear Receptors

Question 3

what are the tactile receptors of the skin ?

all are mechanoreceptors

Answer 3

1) Free never endings
2) Root hair plexus (around hair)
3) Tactile Merkell’s discs (light touch)
4) Tactile Meisnner’s corpuscle (fine touch)
5) Laminated Pacinian corpuscle (pressure)
6) Ruffini Corpuscles (distortion )

Question 4

what are the different types of Proprioceptors ?

Answer 4

They sense the muscle length (Intrafusal fibres ) and trigger muscle stretch receptors ,
Alpha - Gamma motor neurone innervation of Extrafusal fibres allow sensation of stretch even when muscle is contracted.

1) Golgi Tendon organs = muscle tension , initiate an inhibitory reflex = protective
2) Joint receptors = joint movement , pressure, tension

Question 5

Types of temperature receptors

Answer 5

1) free nerve endings
TRPV CHANNELS 
TRPV1 =open when more than 43 degrees , capsaicin in chilli 
TRPV2=open after 52 degrees
TRPA1=less than 18 degrees and menthol

Question 6

Baroreceptors case study

Answer 6

1) monitor BP

2) carotid sinuses, aortic bodies , heart

Question 7

Types of chemoreceptors ?

Answer 7

1) Carotid and aortic bodies
2) Hypothalamic receptors
3) GI tract stimulated by different parts of food contents ( protein triggers gastric secretions)

Question 8

Types of nociceptors ?

Answer 8

respond to mechanical , chemical and temperature stimulation
type1A axon = fast pain
Type C= slow pain

Question 9

somatosensory pathway ? (3)

Answer 9

1) afferent neurone =can be fast or slow / thickness can increase conduction velocity
2) 2nd order neurones= travel to brain via 2 ascending tracts
3) cerebral cortex 3rd order neurones

Question 10

ascending pathways ?

Answer 10

1) Spinothalamic tract (contralateral ) responds to temperature , pain , tickle and itch =2nd order neurone crosses over and ascends , slow conducting
2) Dorsal column ( fine senses , well discriminated ) = primary neurone ascends straight away , second order crosses in brainstem –> thalamus = fast conducting
3) Spinocerebellar tract = primary afferents carry proprioception , travel to cerebellum via many branches , second order = ipsilateral and contralaterally

Question 11

where does the sensory information go to ?

Answer 11

primary sensory cortex
- post central gyrus

1) Occipital lobe =visual cortex
2) Frontal lobe= gustatory cortex
3) Temporal= auditory and olfactory cortex