Week 6 Lesson 43a: Touch and temperature

What is the purpose of the tactile sense of touch?

• orientation in space

• social interaction

• feeding/hunting

• contribution to the coordination of movements

What are the Qualities of the tactile sense of touch?

• Light, discriminating/ crude touch

• Pressure

• Vibration

What type of receptors are mechanically-gated channels embedded in free or encapsulated nerve endings of touch-sensitive neurons?

Touch receptors

What receptors are stimulated any stretching or deviations of neuron membranes change channel opening (as discussed in proprioception)?

Touch receptors

What type of free nerve ending are in the skin at the interface epidermic/dermis?

Crude touch

What free nerve ending has nerve ending can form discs called Merkel’s Discs?

Light touch

What free nerve endings are a part of the hair root that are the most sensitive to touch?

Hair Root Plexus

What encapsulated nerve endings are for reacting to light touch?

Meissner corpuscles

What encapsulated nerve endings are for reacting to pressure?

Ruffini corpuscles

What encapsulated nerve ending are for reacting to Pressure and Vibration?

Pacinian Corpsuscles

What pathway does the most touch neurons follow?

Dorsal Column Pathway

What order for touch neurons ascends in the spinal nerve to the spinal cord where the axons enter the dorsal column pathway and terminates in the ipsilateral medulla?

1st order

What order for touch neurons cross in the medulla and ascend into the ARAS?

2nd order

What order for touch neurons ascend to the somatosensory cortex/touch area for perception?

3rd order

What is it called when each spinal nerve innervates a section of skin?

Dermatome

What is it called when each plexus innervates a section of skin?

Autonomous zone

What is it called when a spinal nerve or plexus is damaged, its skin section loses the sensory function?

It feels numb

How do you evaluate nerve function, dermatome and autonomous zones?

Through touch or light pain stimulus

If the animal does not react to the stimulus what does it mean about the respective nerve?

it is likely damaged

Testing of a nerve is functioning through light pain stimulus or touch is not used in Small Animal practice, but it is used Large animal. When would you use this test in large animal practice?

To support a diagnosis of nerve damage

What is the reflex arc that is stimulates the touch receptors in the dorsal lumbar and thoracic region. The signals enter the spinal cord via spinal nerves into dorsal horns. The 2nd order interneurons travel bilaterally to spinal segments T1 and C8. The synapse with an stimulate lower motor neurons of the lateral thoracic nerve causing a twitching of the cutaneous trunci muscles?

The Cutaneous trunci reflex (CTR)

What reflex is the most useful to test the integrity og the spinal cord from L4 to T1 assisting in lesion localization of TL spinal cord injuries?

CTR reflex

In warm blooded species most of the bodies heat is generated as a by product of what?

Metabolic process

Why is it important to tightly control the body temperature?

Safeguard enzymatic and cellular functions

What is the temperature control center of the body?

Hypothalamus

The hypothalamus acts like what to maintain body temperature within 0.5 degree celcius of it?

Thermostat with a set point

Where are the two main thermoreceptors in the body?

Central from the organs and the peripheral sensors of the skin

Signals from the temperature sensors in the skin travel via what tract to the ARAS?

The lateral spinothalamic tract

When the signals from the temperature sensors in the skin travel up the lateral spinothalamic tract to the ARAS where do the signals go from there?

The somatosensory cortex for perception and to the hypothalamic control center for control

What nerves are used to transmit the temperature signals from the central receptors to t

What receptors are thermally-gated ion channels mostly in free nerve endings of temperature sensitive neurons?

Thermoreceptors

What is the range for thermoreceptors to defect cold?

10-40 degrees C

What is the range in which thermoreceptors are able to read warm?

30-45 (50) degrees celcius

Which receptors read temperature at any range lower than 10 degrees or greater than 45 degrees Celsius?

Pain receptors

How does the hypothalamus, the temperature control center, keep the body at a regulated body temp?

Compares the body temp to a set point to the actual body temperature and starts compensatory mechanisms to fix it.

What are examples of mechanism that the hypothalamus use to restore body temp to its set point?

Autonomic, metabolic, and behavioral responses

What are examples of heat losing mechanisms?

• Vasodilation of the skin causing heat radiation

• Sweating or panting

• Metabolic rate reduction via thyroid gland

• Appetite reduction

• behavioral changes

What are examples of heat conserving mechanisms?

• Vasoconstriction

• Muscle shivering = thermogensis

• non-shivering thermogenesis (brown fat)

• Metabolic rate and appetite increase

• behavioral changes

Cold-blooded animals have hypothalamic control centers that have broader set point ranges. What are the two ranges?

35-39 degrees C

15-25 degrees C

What do cold-blooded and warm blooded animals have in common?

The both have peripheral and core thermoreceptors

Unlike Warm blooded animals who what many mechanisms to regulate their body temperature, cold blooded animals rely mostly on what to achieve temperature control?

Behavioral mechanism

What are examples of behavioral mechanism that cold blooded animals do to achieve temperature control?

• Sun-bathing

• Shade seeking

• Burrowing

• Change in skin color

How do pyrogens temporarily effect the hypothalamic set poin

What phase of a fever is the body temperature being below the set point due to pyrogens, causing the hypothalamus to induce heat-conserving mechanisms?

Chill phase

What phase of a fever is when the body temperature reaches the new set point that was set by the pyrogens?

Fever phase

What phase of a fever is when pyrogens are removed which lowers set point back down to normal, causing the hypothalamus to

What organ in some snake species contians thermoreceptors sensitive to infrared radiation. Enabling them to sense body heat radiating off of prey animals?

Pit organ

What animals have their hypothalamic set point shows diurnal fluctuations: tolerate core temps from 34-41 degrees C to avoid water loss via sweating?

Camelids

What animals have their hypothalamic set points change depending on the season: enter torpor with core temps of 30-34 degrees C and a metabolic rate reduces to 25% periodic muscle activity?

Bears and hibernation

What somatic sense pathway is used in conscious proprioception and touch?

What somatic sense pathway when lesions are below the medulla they have ipsilateral signs but if its above the medulla they have contralateral signs?

Dorsal Column

What somatic sense pathway is used for unconscious proprioception?

Spinocerebellar tract

What somatic sense pathway when has lesions the signs are only ipsilateral?

Spinocerebellar tract

What somatic sense pathway is used for fast pain and temperature, it shows bilateral signs but the contralateral signs can be dominant??

Lateral spinothalamic tract

What somatic sense pathway is used for the slow pain it shows bilateral signs but the contralateral signs can be dominant??

Medial spinothalamic tract

What somatic sense pathway is this and what senses use this pathway?

Dorsal Column: Conscious proprioception and touch

What somatic sense pathway is this and what senses use this pathway?

Spinocerebellar tract and unconscious proprioception

What somatic sense pathway is this and what senses use this pathway?

Lateral spinothalamic tract: fast pain and temperature

What somatic sense pathway is this and what senses use this pathway?

Medial spinothalamic tract and slow pain