Section 3a: Sensory Contribution Flashcards
Why do we need sensory information?
Sensory Feedback is important so we learn how to navigate and interact with our world using our motor behaviour
where do the sensory feedback receptors stem from?
head
muscles
joints
skin
what are the parts of the neuron
- cell body: where the nucleus is
- dendrites: branches of cell body and connects to other neuron’s
- axon: where the electric signal travels by propagating down
- presynaptic terminal: where there neurotransmitters are made & stored in vesicles
- postsynaptic neuron- the neuron that receives the signal from the other neuron’s by the neurotransmitters
what are the 4 functional components that generate signals
-receptive components: dendrite
- Integrative Component: for Sensory its the first node of ranvier; for motor/interneurons its the axon hillock
- signalling components: axon to conduct action potential
- Secretory: a post synaptic terminal
what are the 3 types of neurons
Sensory- (afferent) PNS to CNS
Motor (Efferent) CNS to PNS
Interneurons: in CNS connecting the sensory info to motor neurone
what’s the resting membrane potentials?
-65 to -70mV
what are the states of a neuron
depolarization: when the inside of the membrane has become more positive by the increase Na+ in the membrane
hyperpolarization: when the inside of the membrane have become more negative than resting potential due to efflux of K+ ions
what are the 3 types of potentials?
- Receptor Potential
- Synaptic Potential
- Action Potential
Describe an Action potenial
it occurs when a receptor or synaptic potential is able to change the resting membrane potential to its critical threshold of -55mV. Then a positive feedback loop of depolarization by Na+ channels occurs and increases until +50mV
describe a receptor potential
sensory receptors relieve energy and causes a disturbance in the resting membrane potential but as signal travels passively, it loses amplitude
describe a synaptic potential
similar to receptor except a neurotransmitter release from one neuron causes a disturbance in the post synaptic neuron altering the resting membrane potential but is also decreases in amplitude as it travels
What are the 2 features of the signal from neuron?
- number of action potentials
- time between the action potentials
what 4 features are the nervous system extracting from the signals they receive
- modality: type of stimulus
- intensity: the frequency and number of receptors as firing (population coding), area sensitivity
- duration: how long stimulus is detected
- location: some area of skin have large receptive fields and others have small to detect fine stimuli
how does the brain know about modality or location?
labelled line concept- each neuron is delivering one aspect of information from a place in the body and the nervous system knows what information is carried by what neurons
what is proprioception?
the sensation and perception of limb, trunk and head position
what are the 3 types intrafusal muscle fibres
nuclear bag
- dynamic 1 bag
- static 2 bag
chain fibres
what does dynamic 1 bag detect?
changes in muscle length and limb/muscle movement
what does static bag 2 detect?
static length or position of muscle
what does the chain fibre detect?
static length or position of muscle
which sensory neurons are connected to which intrafusal muscle fibre
Group 1a - Dynamic Bag 1, Static Bag 2 and Chain
Group 2 - Static Bag 2 and Chain
what does motor neurons are connected to which intrafusla muscle fibre?
gamma dynamic - dynamic bag 1
gamma static - static bag 2 and chain
what is the motor gamma dynamic neuron job?
increase sensitivity to muscle length changes
what is the motor gamma static neuron job?
increase sensitivity to muscle length position
what neurons detect changes in length
motor - gamma dynamic
afferent - group 1a
what neurons detect stationary length and position of muscle
motor- gamma static
afferent- group 2 (MOSTLY), group 1a (minor)
which muscles have the highest muscle spindle density
(extraocular) eye muscles, hand and neck
what are extrafusal muscle fibres?
regular muscle fibres
what is alpha gamma co activation and why is it important
its the motor neurons working together. if they alpha neurons where to move on their own the gammas wouldn’t know and the muscle would be stuck in that state. But since the muscles move tother, the motor neurons can detect changes and signal the alpha when to change again
monosynaptic
when it goes directly from afferent to motor
disynaptic
when afferent goes to interneuron then motor
what are GTOs and what do they do
Golgi Tendon organs- they are receptors and the muscle tendon junction that detect load or force
- only care about shortening
what is special about GTOs
they aren’t connected to the CNS
what sensory neuron is connected to the GTOs
group 1b
techniques that study proprioception
- deafferentation
- sensory neuropathy
- muscle/tendon vibration
what is deafferentation
surgical- removing afferent pathways
temporary deafferentation - circulation cut off
sensory neuropathy
diabetes stops their afferent nerves from working
- they can’t sense their limbs
- can’t copy movement without seeing their own limb
muscle/tendon vibration
distorts the group 1a afferents
- may think muscle is lengthening
touch is based on what type of receptors
- pacinian corpuscle
- meissner corpuscle
- Ruffini’s corpuscle
- merkel’s disk
- free nerve endings
pacinian corpuscle detection
vibration
meissner corpuscle
stroking and vibration
merkel’s disk
pressure
ruffini’s corpuscle
skin stretch
free nerve endings
pain
how does sensory info reach the brain
through dorsal root ganglion to the primary somatosensory
