Chapter 10 Part 1

What is somatic sense?

What the body can sense

What can the body sense?

1. Touch

2. Pain

3. Temperature

4. Itch

5. Proprioception

Which cranial nerve does the somatic sense of vision?

CN II

Which cranial nerves does the somatic sense of hearing?

CN VIII

Which cranial nerve does the somatic sense of taste?

CN VII, CN IX, CN X

Which cranial nerve does the somatic sense of smell?

CN I

Which cranial nerve does equilibrium?

CN VIII

What is pseudounipolar neuron?

A neuron that has a fake cell body.

• The cell body is not really part of the axon

What is the whole point of the nervous system? (3 things)

1. To get a signal from the outside world

2. Send the signal to the brain

3. Act upon the signal

When a dendrite is near the sensory area, what is this called?

Free Nerve Ending

What is free nerve ending?

A sensory nerve receptor found on the skin or tissue to detect change

What do dendrites have in order to detect the change?

Receptors

What is special about receptors in terms of change?

Receptors are very specific to the types of change

What are the types of sensory receptors?

1. Chemoreceptors

2. Mechanoreceptors

3. Photoreceptors

4. Thermoreceptors

What is chemoreceptors?

Receptors that detects different chemicals

What are some chemicals that chemoreceptors can take?

1. Oxygen

2. pH (H+)

3. Organic molecule

What is mechanoreceptor?

A receptor that detects the

1. Vibration

2. Pressure

3. Osmoregulation

4. Acceleration

What is photoreceptor?

A receptor that detects the light photons

What is thermoreceptors?

A receptor that detects to varying degrees of temperatures

What is transduction?

The ability to turn the outside world stimulus energy into an action potential that the nervous system can process

Give an example of transduction?

Example: It is hot outside

• The skin receives the stimulus energy of the heat

• The stimulus energy turns into an action potential that the nervous system can process

What is important to remember about the stimulus and change?

The stimulus must be strong enough in order for there to be change

What is the receptive field?

The physical area where a stimulus activates a neuron

What is a two point discrimination?

A test for the receptive field

• When 2 points can turn into one action potential

Where can we see vision of the eye?

Occipital Lobe

Where can we see hearing and balance?

Temporal Lobe

Where can we see all sensory?

Parietal Lobe

Where can we see taste?

Gustatory Complex

Where can we see Smell?

Insula Lobe

What is localization?

The idea that certain functions take place in certain locations or areas within the brain

What is the localization of sound?

If the sound is closer to one ear:

• You can hear the sound earlier in the closer ear

• The sound however will sound like one because the sound is almost identical and comes at almost the same time

What 2 categories is somatic sensory broken up into?

1. Epicritic Sensory

2. Protopathic Sensory

What does the Epicritic Sensory sense?

1. Fine sensory (two point discrimination)

2. Vibration

3. Pressure

4. Proprioception

What is Proprioception?

Unconscious 6th sense

• The body’s ability to sense its own position and movement

What does the Protopathic Sensory sense?

1. Coarse/Plain Touch

2. Pain (fast and slow)

How does Epicritic Sensory turn into action potential?

By receptors

What receptors does Epicritic use?

1. Merkel Receptor

2. Meissonier Corpuscle

3. Pacinian Corpuscle

4. Ruffini Corpuscle

What does the Meissenier Corpsule receive?

Pressure and touch

What does the Pacinian Corpsule receive?

Vibration

What does the Ruffini Corpsule receive?

Skin Stretching

How does Protopathic Sensory turn into action potential?

Free Nerve Ending

What is the pathway of Sensory for Epicritic?

It is in your notes

What is the pathway of Sensory for Protopathic?

It is in your notes

What is Nociception?

Pain

How does Epicritic Sensory travel?

Ipsilaterally

How does Protopathic Sensory travel?

Contralaterally

Once both the epicritic and protopathic reach the thalamus what happens?

Everything is on the same side as primary somatic sensory cortex

In the medial part of the primary somatic sensory cortex, what parts of the body is there?

Lower limbs

In the lateral part of the primary somatic sensory cortex, what parts of the body is there?

Upper limbs

If there was a T3 GSW on the right, What happens to the Epicritic pathway?

The spinal nerve T3 and below will not have any sensory on the right

If there was a T3 GSW on the right, What happens to the Protopathic pathway?

The spinal nerve T3 and below will not have any sensory on both sides

What are the classes of somatosensory nerve fibers?

1. A (beta)

2. A (delta)

3. C (fibers

What is A beta?

A somatosensory nerve fiber that is epicritic

• Large and myelinated

What is A delta?

A somatosensory nerve fiber that is protopathic

• Small, myelinated pain fibers

Is A delta fast pain or slow pain?

Fast

What is C fibers

A somatosensory nerve fiber that is protopathic

• Small, non myelinated pain fibers

Is C fibers fast or slow pain?

Slow pain

What does a large myelinated neuron mean?

Very fast signal

What is referred pain?

Pain that is felt in one area of the body, but the origin of the pain is somewhere else.

Do organs have epicritic or protopathic sensory? If not what do they have?

They do not… They have action potential

If there is pain in the organ, what will happen?

The organ will action potential to turn on a nearby C fiber and fire the pain signal to the brain and then on the skin

If you have upper abdominal pain, where is the pain reflected on?

The stomach

If you have a heart attack, where would you feel the pain?

The whole upper body

If your liver and gallbladder issues, where would you feel the pain?

Right Shoulder

What happens when there is no stimulation to the C fiber?

A inhibitory neuron will prevent the pain pathway to go through

What happens when there is stimulation for the C fiber?

The C fiber will inhibit the inhibitory neuron while activating the protopathic pain pathway

What happens when there is stimulation for the C fiber but a epicritic pathway comes through?

The C fiber will inhibit the inhibitory neuron while activating the protopathic pain pathway

• HOWEVER, epicritic sensory calms down the protopathic pain pathway by activating the inhibitory neuron

What does the epicritic sensory do to pain from the C fiber?

It distract pain from the C fiber by adding another stimulus