Sensory system

Question 1

What are free nerve endings?

Answer 1

encoding sensory stimulus

mostly found in skin (muscle, joints and viscera) signals need to reach brain due to network of neurones which develop an awareness of sensations.

Question 2

Explain the simple structure of free nerve endings

Answer 2

• branching and unencapsulated
• Penetrate dermis (skin)

Question 3

What do free nerve endings do?

Answer 3

Senses temperature, crude touch, itch and nociception (pain)

Question 4

What is nociception?

Answer 4

Sensing or encoding noxious stimuli

Question 5

Apart from free nerve endings what are other unencapsulated nerve endings?

Answer 5

Tactile discs and hair receptors

Question 6

How are free nerve endings activated?

Answer 6

1. Temperature, stretch, touch and pressure
2. NoCiceptive signal (danger, damage and impending damage)
   Inflammatory chemicals

Question 7

What are the three types of neurones in the spinothalamic tract?

Answer 7

first order neurone

second order neurone

third order neurone

Question 8

What are first order neurones?

Answer 8

1. – Can be nociceptor
   – free nerve ending
   – sense and encode information into the spine
   – celll body in dorsal root ganglion

Question 9

What are second order neurones?

Answer 9

– carry signal up the spine and into the thalamus
– synapses information to third order
– cell body found in dorsal horn of spinal cord

Question 10

What is a third order neurone ?

Answer 10

– thalamus to primary somatosensory cortex
- cell body found in thalamus

Question 11

Explain the process of nerve endings to awareness of information between free nerve ending and two the second order neuron

In a single (action potential) as it arrives at spinal cord.

Answer 11

-Synapse passes sensory signal to the second order neuron
- Spinal ganglion AKA dorsal root ganglion

1. Up and along free nerve ending ->
2. cell body (in spinal ganglion or dorsal root ganglion) ->
3. second axon ->
4. into grey matter of spinal cord ->
5. synapse in spine to the second order neurone

Question 12

Explain the process from second order neurone to awareness of information

as a single action potential arrives at the spinal cord

Answer 12

1. MRI image spinal sensory tract to show bundle of axon movement of second order neurone up spine to the thalamus
2. Information arrives at thalamus (sits under lateral ventricles)
3. Second order neurones synapses with third order neuron in the thalamus
4. Finally the sensory signal is carried to the somatosensory cortex (primary sensory cortex)
   We become aware of the information

Question 13

What does the motor cortex somatic do ?

Answer 13

motor control of skeletal muscle

for motor planning

Question 14

What does the sensory cortex do?

Answer 14

input from the skin, proprioceptors and spatial discrimination

Question 15

What is somatotopy?

Answer 15

Body maps onto brain surface

Question 16

What is the homunculi?

Answer 16

Sensory mapping in post central gurus
Which area of the brain the information does to tells the brain which area of the body has been effected

Question 17

What is direct spinothalamic?

Answer 17

Spinothalamic pathways to the brain

-cortical areas
- better spatial discrimination

• Information at third order neurone goes to primary somatosensory cortex

Question 18

WHat is indirect spinothalemic?

Answer 18

Spinothalamic pathways to the brain

Info taken to - lambic system, hypothalamus, reticular formation and reticular activity system.

poor spatial discrimination like emotional salience

Question 19

What. type of spinothalamic information is received at the reticular formation?

Answer 19

Indirect spinothalemic information

Go to the autonomic centres of the brain and brain stem - warns the system

Triggers parasympathetic - rest and digest or the sympathetic flight or fight response.