IC2&3 - Neurophysiology Flashcards
What is an afferent?
Neuron fibre that transmit information from PNS To CNS
What are efferents?
Nerves fibres that transmit signal from CNS to PNS
What are the two factors that affects the speed of signal conduction?
Myelination and size
Pain signal is communicated via the ______ pathway to neurons via _____.
afferent, synapses
What are the two examples of postsynaptic target?
Dendrites (excitatory synapse)
Soma (inhibitory synapse)
How is signal transmitted to CNS?
Via generation electrical signal/ Action Potential from a negative resting membrane potential is generated.
Upstroke of action potential results in _____.
opening of voltage gated Na+ channels
Downstroke of action potential results in ______ and ______.
Inactivation of Na+ channel, opening of K+ channel
Name 2 ways in which ions pass through the ion channels?
- Concentration gradient
- Electrical ‘pull’ and electrochemical gradient
Hyperpolarization causes neurons to be _______.
inhibited
What is the inhibitory transmitter that is involved in hyperpolarization?
GABA
Describe the process in generating action potential when touch is applied.
- Touch
- Conversion of external stimuli to electrical charges
- Depolarization results in action potential
- Action potential jumps from node to node (nodes of ranvier) via saltatory conduction
- Goes to CNS
List the 5 roles of cortex.
- Sensation, perception
- Voluntary movement
- Personality traits
- Learning + Memory
- Language
What are the four defined regions in neuron?
- Cell body (Soma)
- Dendrites
- Axons
- Presynaptic terminals
What is the resting membrane potential related to?
Differential distribution of ions across the membrane
What are the three components of the synapse?
Presynaptic terminal, postsynaptic cell and synaptic cleft
What is released in the process of synaptic transmission?
Neurotransmitters (E.g. Acetylcholine)
Where does acetylcholine binds to?
Nicotinic receptor
What is the major excitory transmitter at CNS synapse?
Glutamate
Which fibres respond to pain?
A-delta and C fibres
Which fibre respond to touch
A-beta
How does K+ cells move in and out of cells?
- Concentration gradient
- Electrical pull
What are the two limbic structures in the medial temporal lobe?
Hippocampus, Amygdala
What are the two major somatosensory relay?
- Spinothalamic tract pathway (pain)
- Dorsal column pathway (touch)
Describe the pain somatosensory relay.
Tissue damage > Signal generated at nocireceptor > Relay of peripheral signal via action potential to spinal cord > Enter dorsal horn and synapse on receiving neurons > receiving neurons sends long axons to thalamus > information is then sent to cortex
Signal travels along ______________.
Topographic lines
Which somatosensory cortex does the input from somatic surface reaches?
Primary
Information from lower limb reaches the _____ part of the somatosensory homunculus.
Medial
Information from the upper parts reaches more ______ regions of the somatosensory cortex.
Lateral
The somatosensory homunculus contains _____ mapping of the face due to ______ density of receptor in the face regions.
Larger, higher
What is a labelled line?
It refers to the receptor and its associated first order neurons.
How many types of stimulus does the labelled line respond to?
1
The intensity of the external stimulus applied to skin is encoded by _____.
sensory relay
What are the two types of intensity encoding?
Frequency code (No of AP evoked in labelled line)
Population code (No of receptors excited)
Describe the relation between pain intensity and the intensity coding.
The higher the number of receptors excited , the higher the action potential generated per unit time, the more intense the sensation.
Sensation felt by an individual is due to which factors?
Quality (labelled line)
Intensity (frequency and population code)
Location (receptive field, sensory homunculus)
Define hyperalgesia.
Increased pain to a given noxious stimulus
Define Allodynia.
Pain to a normally non-painful stimulus
What is sensitization?
Spontaneous activity and increased responsivness
Also shows a decrease in excitation threshold of pain pathway
List three possible mechanisms of touch allodynia.
- Degeneration of inhibitory neuron
- Altered inhibitory neuron functions
- Altered spinothalamic neuron functions
How does degeneration of inhibitory neuron cause touch allodynia?
Lesser inhibitory neurons for inhibition of pain, hence decreasing threshold of pain and increase pain
How does altered inhibitory neurons casue touch allodynia?
Excites spinothalamic neuron post injury instead of inhibit
How does altered 2nd order spinothalamic neurons casue touch allodynia?
Injury causes nocireceptors to becomes more excitable due to decreased threshold and increase excitation of ST neuron, making it more responsive to touch
What are two types of pain modulation?
Segmental modulation (Gate theory)
Descending
Explain segmental modulation.
Stimulation of large diameter afferents for touch excite inhibitory interneurons, in turn decreasing transmission of pain signal in spinal cord
Explain descending modulation of pain.
Stimulation of mid brain activates medullary regions and hence stimulating internuerons in spinal cord, inhbiting transmission of pain signal
What are three types of movements?
Reflexes
Rhythmic motor patterns
Voluntary
Reflexes involves _______ movements.
involuntary
Rhythmic motor patterns requires ______ initiation and termination.
Voluntary
Goal directed movements are _____.
voluntary
The _____ controls voluntary movement.
cortex
The ____ controls postural reflexes and rhythmic motor patterns
brain stem
How do the cortex and brainstem regions influence movement?
via neurons that send long axons from the site of origin to spinal cord
Adjustment in output of efferent via cortex and brainstem can ______ affect movement
indirectly
What disorder will occur if the basal ganglia is damaged?
Movement and posture disorder
