Sensory system Flashcards
What are free nerve endings?
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.
Explain the simple structure of free nerve endings
- branching and unencapsulated
- Penetrate dermis (skin)
What do free nerve endings do?
Senses temperature, crude touch, itch and nociception (pain)
What is nociception?
Sensing or encoding noxious stimuli
Apart from free nerve endings what are other unencapsulated nerve endings?
Tactile discs and hair receptors
How are free nerve endings activated?
- Temperature, stretch, touch and pressure
- NoCiceptive signal (danger, damage and impending damage)
Inflammatory chemicals
What are the three types of neurones in the spinothalamic tract?
first order neurone
second order neurone
third order neurone
What are first order neurones?
- – Can be nociceptor
– free nerve ending
– sense and encode information into the spine
– celll body in dorsal root ganglion
What are second order neurones?
– carry signal up the spine and into the thalamus
– synapses information to third order
– cell body found in dorsal horn of spinal cord
What is a third order neurone ?
– thalamus to primary somatosensory cortex
- cell body found in thalamus
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.
-Synapse passes sensory signal to the second order neuron
- Spinal ganglion AKA dorsal root ganglion
- Up and along free nerve ending ->
- cell body (in spinal ganglion or dorsal root ganglion) ->
- second axon ->
- into grey matter of spinal cord ->
- synapse in spine to the second order neurone
Explain the process from second order neurone to awareness of information
as a single action potential arrives at the spinal cord
- MRI image spinal sensory tract to show bundle of axon movement of second order neurone up spine to the thalamus
- Information arrives at thalamus (sits under lateral ventricles)
- Second order neurones synapses with third order neuron in the thalamus
- Finally the sensory signal is carried to the somatosensory cortex (primary sensory cortex)
We become aware of the information
What does the motor cortex somatic do ?
motor control of skeletal muscle
for motor planning
What does the sensory cortex do?
input from the skin, proprioceptors and spatial discrimination
What is somatotopy?
Body maps onto brain surface
What is the homunculi?
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
What is direct spinothalamic?
Spinothalamic pathways to the brain
-cortical areas
- better spatial discrimination
- Information at third order neurone goes to primary somatosensory cortex
WHat is indirect spinothalemic?
Spinothalamic pathways to the brain
Info taken to - lambic system, hypothalamus, reticular formation and reticular activity system.
poor spatial discrimination like emotional salience
What. type of spinothalamic information is received at the reticular formation?
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.
