The beggining Flashcards
4 main functions of sensory information
Perception
Control of Movement
Regulation of the function of internal organs
Maintenance of arousal
Perception
The brain’s construction of the world using certain rules
Also means that out sensory experiences actually feel like something that can only be understood when you experience it
Common Properties of sensation
- Modality ( quality, e,g, somatic/vision/audition/olfaction)
- Submodality(e.g fine touch, warmth, heat) - Intensity
- Duration
- Location
Dorsal Column-medial lemniscal pathway
Fine touch (sensitive touch at fingertips and vibration)
Proprioception (Sensory feedback from muscles and joints)
Anterolateral pathway
Pain
Temperature
These two are more involved in monitoring body states
Primary sensory afferents of DCMLP
1) A-alpha and A-beta fibers enter the spinal cord from the periphery and remain ipsilateral
2) They travel up to the brainstem and then FIRST SYNAPSE in this pathway
Differences between the DCMLP and ALP
ALP makes a synaose right as it enters the spinal cord and ipsilaterally make a synapse which then goes to the other side of spinal cord
Anterolateral pathway fibers?
A-delta and C fibers
Dorsal column-medial lemniscal pathway fibers?
A-alpha
A-beta
Primary Somatic Sensory Afferent Description
One long axon
No dendrites
Cell body off to the side before reaching the spinal cord
Equivalent to dendrites is the specialized ending (sensory receptor)
Transduction baby!!!!!
Sensory Transuction
First step of sensory processing
Sensory information from the external(or internal) environment into opening (or closing) of ion channels in receptor cells.
Low-threshold mechanoreceptors
Stretch-activated ion channels
Ending gets depolarized which causes an action potential
Primary Sensory Fiber
Pressure on the skin is encoded as action potentials in primary sensory fibers
Action potential encoding
When AP starts stimulus starts
When AP ends stimulus ends
As pressure increases, frequency of action potentials increases
Sensory receptors
Act as filters, extracting specific forms of sensory information and ignoring others
Types of primary somatic sensory fiber endings
Slowly Adapting
Rapidly Adapting
Free nerve endings
Slowly Adapting
They fire action potentials as long as there is pressure on the skin, firing rate however starts to fade out over time.
Merkel and Ruffini have endings that are specialized to maintain depolarization throughout the pressure pulse so neuron keeps firing throughout the pressure pulse
Almost all sensory transduction processes fade out over time
Rapidly Adapting
Fire at the beginning and in the end
Meissner and Pacinian
SA1
Merkel Cell
Light touch
SA2
Ruffini ending
Stretch
RA1
Meissner Corpuscles
- Detect vibration
- really high frequency vibration like hundreds of hertz
- Detect texture
RA2
Pacinian Corpuscles
- Detect vibration
- low frequency vibration
- Detect texture
Free nerve endings
- Transducing pain and temperature
Perception has to do with which labeled line is activated
Specific subset of neurons have to be activated e.g neurons over 50 degrees Celsisus
Capsacian activate labeled line of heat
Mint activates cool
Combinatorial Processing
Perceived
Fast pain - Stove
a-delta
Slow pain - Stove
C fibers
Receptive field
The primary somatic sensory neurons Innervate a specific region of the body surface. Stimulus within receptive field excites the cell
Anterolateral Pathway
A-delta and C fibers
Cross to contralateral side in anterolateral column, continue to brainstem and then cortex
DCMLP
A-alpha and A-beta
Stay on ipsilateral side, until brainstem synapse where they cross to contralateral side
Length and diameter of spinal cord
42 to 45cm long
<= 1cm in diameter
31 segments of spinal cord
8 cervical
12 thoracic
5 lumbar
5saccrial
1 coccygeal
Each corresponds to the entry point of a pair of spinal nerves
Cervical and lumbar enlargements
Correspond to the segments that innervate the limbs
Lumbar cistern
Cord is shorter then verterbral canal, ending at the 1st lumbar vertebra
Below this spinal nerves project down towards the lumbar cistern
Vertebra form this space
Exit at the appropriate vertebrae forming the CAUDA EQUINA (horse’s tail)
Cauda Equina
The sack of nerve roots (nerves that leave the spinal cord between spaces in the bones of the spine to connect to other parts of the body) at the lower end of the spinal cord. These nerve roots provide the ability to move and feel sensation in the legs and the bladder.
Foramen Magnum
Where cord enters skull to form the medulla
What is the most caudal region of the brainstem?
medulla
First pain
A-delta
Second pain
C-fiber
