I’m not sure if I understand all your questions, but I’ll give it a try! I'm not an expert on the somatic sensory system, so if someone more credible could confirm my info, that would be great.

Yes, the types of skin (or: cutaneous) receptors on the scalp are the same as those at other locations on the body: mechanoreceptors (for pressure), thermoreceptors (for temperature) and nociceptors (for pain).

Simply put, there are two types of thermoreceptors. One type increases firing rate with warming and decreases firing rate with cooling. The other type decreases firing rate with warming and increases firing rate with cooling. The two different thermoreceptor types do not innervate the same area of skin. For instance, one small area (e.g. 1mm wide) contains ‘cold’ receptor, while the neighbouring area (of 1mm) contains ‘warmth’ receptors (Bear, Connors & Paradiso, 2007: chapter 12, p. 418; see references at bottom).

Not all sensory nerves from the cranial surface travel to the spinal cord! Receptors on the back of the scalp and on the throat area are innervated by spinal nerves, while receptors on the face and the top of the scalp are innervated by so called cranial nerves (more specifically, the trigeminal nerve). In contrast with spinal nerves - which travel through the spinal cord - cranial nerves go straight to the brain or brainstem. The picture below is a good illustration: as you can see, nerves from the posterior and throat part go to the cervical spine (blue and purple area), while the rest goes directly into the brain via different cranial nerves.

http://en.wikipedia.org/wiki/File:Gray784.png

Also: http://en.wikipedia.org/wiki/Scalp#Innervation. The second and third in this list are spinal nerves. The other three are part of the trigeminal nerve, which is a cranial nerve.

So, to answer your first question: Thermoreceptors in the scalp skin relay information about temperature to the brain. For the posterior and throat regions, this information is relayed through the cervical spine (which is part of the spinal cord) to the brain. For the rest of the scalp, the information is relayed by different cranial nerves directly into the brain.

Unfortunately I don’t understand your last question. Can you rephrase it?

I hope this helps you!

Sources:

This wikibooks page is a great source if you need some general info or some references if you want to read more detailed texts on the subject (see bottom of page for references). http://en.wikibooks.org/wiki/Sensory_Systems/Somatosensory_System#Anatomy_of_the_Somatosensory_System

The textbook Neuroscience: Exploring the Brain (3rd ed.) by Bear, Connors and Paradiso (2007) also has some great info on thermoreceptors and nerves, especially chapter 12: The Somatic Sensory System.

Hi,

what I meant was are there different receptors for skin and scalp to relay temperature information to brain or are they same? If I took hot water head bath I am actually affecting many areas of body from scalp to body skin which transmits the signal that water is hot..to my brain. What are those receptors who do that? 

Thanks for your extensive answer though. 

Hi Kalpita,

They are the same. To give you a short answer: External temperature (like a hot water bath) is sensed by thermoreceptors under the skin. The only thermoreceptors between the skull and skin are those located right under the skin. Simply put, there are two types of thermoreceptors: those that increase firing rate with warming, and those that increase firing rate with cooling (see my previous reply).

A more in-depth answer:

We can differentiate thermoreceptors based on their location.

1. Peripheral thermoreceptors are located under the skin and cause our perception of external temperature. Most thermoreceptors by far are peripheral. There are 2 temperature types: warm and cold, see above. My textbook mentions 6 different channels, two of which increase firing rate with cooling, and four that increase firing rate with warming.

2. Central thermoreceptors are located more internally in the body, namely in the medial pre-optic area of the hypothalamus. These change their firing rate in response to small changes in core temperature (3 temperature types: see source).

So, in your example of a hot water head bath, due to the sudden change in temperature near the skin surface the peripheral thermoreceptors under the skin would dramatically change their firing rate (increase or decrease depending on type of receptor). After a few seconds pass and temperature stays the same, the initial receptor response is attenuated as the receptors adapt to the new temperature.

The central thermoreceptors only change their firing rate with a change in core body temperature, and I am unsure whether this is the case with a hot water head bath. I am not a hot water bath expert, but maybe core temperature is only affected after an extended period of time or with a very hot bath! I guess you could test this by measuring core temperature during the hot water bath.

Hope this helps! Good luck.

If you need to know more, like ion channel properties or their exact location under the skin, I suggest you look at some textbooks or articles.

General source with a few pages on this subject: Neuroscience: Exploring the Brain (3rd ed.) by Bear, Connors, and Paradiso (2007).

Source for central thermoreceptors: http://link.springer.com/article/10.1007%2Fs11055-007-0167-4#page-2

Thanks Sacha,

for the insight. I am trying to find more things on hot water induced phenomena. Any reference will be valuable.

Kalpita