Touch. Flashcards
Is touch essential for proprioception?
Yes.
What are most of the receptors that contribute to touch?
Free nerve endings within the skin.
How do the receptors that respond to touch vary?
They have different sensitivities, some are very sensitive, others take massive pressure before any stimulus is generated.
What and pacinian corpuscles?
Sensors found in the subcutis.
What is sensed by pacinian corpuscles?
Vibrations.
What animals are pacinian corpuscles often found in?
On the wingtips of birds or in animals that hunt.
What spinal tract is used for the sense of touch?
The dorsal column.
Will the sense of touch be ipsilateral or contralateral as it runs up the spinal cord?
It stays ipsilateral until it reaches the medulla, where it crosses over and travels to the cortex.
What are dorsal cutaneous branches of spinal nerves?
Small branches that project off each spinal nerve.
What is the function of the dorsal cutaneous branches?
They innervate a small section of skin which is known as a dermatome.
What kind of nerves innervate the forelimb?
Plexus nerves.
Are spinal nerves found in the forelimb?
Spinal nerves travel to the brachial plexus and then plexus nerves continue to innervate the forelimb.
What name is given to the area of skin that is innervated by a plexus nerve?
An autonomous zone.
How do touch stimuli travel from the free nerve endings to the spinal cord?
Down a spinal/plexus nerve (first order neuron) to the dorsal grey horn of the spinal cord.
How does a touch stimulus travel up a 2nd order neuron?
It travels up the spinal cord to the medulla.
How does a touch stimulus travel up a 3rd order neuron?
It crosses over in the medulla and then travels to the cortex to be processed.
Can we use dermatomes to test spinal nerves?
Yes.
E.g. If we test spinal nerve T8 we find the correct dermatome and touch it or prick it to see if we get a normal response.
How can we tell if there is damage to a spinal nerve or plexus nerve from a dermatome?
There will be loss of sensation in that dermatome or autonomous zone.
How can we tell if there is damage to the spinal cord?
There will be no sensation anywhere below the location of the damage.
When does the cutaneous trunci reflex occur?
When we stimulate the skin in the thoracolumbar region of an animals back.
What happens in the cutaneous trunci reflex after the animals skin has been stimulated?
There is contraction of the cutaneous trunci muscle.
What nerve innervates the cutaneous trunci muscle?
The lateral thoracic nerve.
Where does the lateral thoracic nerve originate from?
Around the level of the shoulder.
The lateral thoracic nerve receives nerve fibres from what vertebrae?
The vertebrae from C8 to T1.
What kind of nerve is the lateral thoracic nerve?
A motor nerve with no sensory elements.
What happens in the cutaneous trunci reflex if we prick the animal at the level of L3?
The cutaneous trunci muscle should twitch if the reflex is working.
When will the cutaneous trunci reflex not be working?
If there is damage to the spinal cord above the point where you prick the animals back.
In what direction will we test the cutaneous trunci reflex?
From caudal to cranial.
The cutaenous trunci reflex can be tested between what areas of the spinal cord?
C8/T1 to L4/L5.
