Somatic Sensation Flashcards
1
Q
Sensory neurons are…
A
Uni polar
- one process eminates from cell body
- the branches into dendridites
- peripheral terminal is dedridites (inputs)
- axons are output in PNS
2
Q
Propprioceptors
A
- a sensory receptor which receives stimuli form within the body
- responds to position and movement
3
Q
Medulla oblingata
A
A major relay centre for sensory information
4
Q
What happens if you experience a light touch sensation
A
- touch mechanical receptors in skin (unipolar neuron) will generate a receptor potential, if its brought to threshold, it will be caries along from dendrites a long cell body and through axon to CNS
5
Q
Receptors are…
A
Unipolar axons
6
Q
Mechanoreceptors - proprioception + touch - what are they stimulated by and what are their endings
A
- stimulated by physical forces which distort plasma membrane
- nerve endings contain mechanically gated ion channels
- proprioceptors (muscle spindles)
- baroreceptors (blood pressure)
- tactile receptors - touch, pressure, vibration
7
Q
A
8
Q
When muscle spindle is stretched
A
- muscle spindle has sensory nerve endings
- when stretched, mechanically gated ion channels are opened thus initiation of a receptor potential
- if RP is bought to potential it will fire an AP and that info will be sent to higher centres in brain to meditate changes but will also trigger an reflex response without higher centres
9
Q
Different shapes and locations of a receptor
A
- the closer a receptor is to the surface, the more sensitive it is to light touch
- sensors at different layers sensing various types of touch and pressure
- encapsulated nerve endings - give greater sensivility to stimuli
- long and thin sense stretch - deep, strong, shallow wreaths ??
- tactile disk - sensitive to vibration
10
Q
Hairy skin?
A
- there are sensory nerves (nerve endings) associated with the root of each hair
- ## you can feel the hair when you move it as a result of the displacement of the hair shaft interacting with mechanically gates ion channels on nerve fibres on base of hair cell
FREE NERVE ENMDINGS?????
11
Q
Nocieceptors
A
- activated by noxious stimulu - typically responding to signals generated by tissue damage - trigger perception of pain
- wide spread everywhere except Brian
- free nerve endings respond to three main types of noxious stimulus
- thermal
- mechanical
- chemical
12
Q
Signal transduction
A
- sensory receptors have a specialisation that makes them sensitive to a particular stimulus
- e.g touch has mechanically gated channels
- preentrautin of the stimulus opened ion channels which leads to a change in MP - RECEPTOR POTENTIAL
- if RP reaches threshold, an AP is initiated in the sensory receptor
- by this mechanism, a stimulus from the external environment is converted into a change in membrane potential so it’s presence can be recorded in the brain
- the process of converting a stimulus of one from (touch) into a different form (change in membrane potential) is called signal transduction
13
Q
Receptive field
A
- endings of any single receptor spread over a restricted area
- senseory neuron is stimulated only when the stimulus is presented within the area its receptors are located, the receptive field
- big field provides poor localisation of the stimulus, small fields provide good localisation e.g touch on fingertip vs shoulder
- good (tiny receptor field) vs poor discrimination (huge receptor field)
14
Q
Two type of responses to stimuli
A
Phasic
Tonic
15
Q
Phasic receptor
A
- during change, receptors are firing actions potentials
- during new steady state, neuron is not firing action potential
- when changes again, action potentials are fires until it reaches new steady state
- normally silent, respond briefly to change e.g touch and temp receptors
- fast adapting - like putting your sock on
16
Q
Tonic receptors
A
- continually active to reflect background level of stimulation
- AP frequency changes when stimulus intensity changes e.g muscle spindles
- slowly adapting
- reach a new steady state after a change in frequency
- body can tell where bicep is in space
Tonic - frequency
17
Q
Information coding: receptors in code 4 types of info
A
Modality
Intensity
Duration
location
18
Q
Modality
A
- type of receptor activated
- we can distinguish temperature from touch, because some receptors are temperature sensitive and some are touch sensitive
- this info is kept seperate in the axons through the sensory pathways to the diff parts of the Brian
- sensory receptors carrying specific types of information are kept seperate to signal their different parts of the brain
19
Q
Intensity
A
- stimulus strength, encoded by frequency of AP firing in afferent neuron
- big stimulus can encode a high frequency firing of AP
- bigger receptor Potential because more sustained depolarisation results in higher frequency of APS
- size of stimulus is encoded in the frequency of AP firing
20
Q
Duration
A
- time period over which stimulus exists
- encoded by time period over which APS are fired in afferent neuron
21
Q
Location
A
- place in body where receptors are activated (mapped) in brain (somatosensory cortex) - action potentials
22
Q
Primary cortex organisation
A
- the post central gurus functions at the primary somatosensory cortex
- specific regions of the somatosensory cortex receive sensory information from specific regions of the body
- receptor fields of tounge/face neurons are much smaller and the neurons themselves are much more numerous then the neurons that project to legs and trunk
- gives greater discrimation and sensation arising from tounge and face compares to trunk (relates to receptive fields and number of recepters in the skin)
23
Q
Are nocieceptors myelinated and are they free?
A
Slightly or unmyelinated
Free
24
Q
Are thermo receptors free and are the myelinated?
A
- myelinated and free
25
Q
Are mechanical receptors free / myelinated?
A
Contained in specialised capsules
