Neuroscience of Pain, Neuroplasticity, and Sensory Systems

What is the definition of pain?

An unpleasant experience associated with tissue damage that helps discourage/prevent future damage and promotes healing behaviors.

What are nociceptors?

Peripheral receptors that respond to painful stimuli, acting as specialized receptor proteins.

What are A delta fibers?

Myelinated fibers that conduct signals quickly and are associated with sharp, first pain, responding to temperature changes, chemicals, and pain.

What are C fibers?

Unmyelinated fibers associated with diffuse, longer-lasting second pain, responding to all forms of pain stimuli (thermal, mechanical, or chemical).

How do nociceptors produce action potentials?

They use pain-specific voltage-gated sodium channels.

What pathways convey information about pain to the brain?

The spinothalamic and trigeminal pain pathways.

What does the trigeminal pathway relay?

Pain and temperature information from the face.

What does the spinothalamic pathway relay?

Pain and temperature information from the rest of the body.

What is the role of the primary somatosensory cortex in pain perception?

It receives information about pain, including its intensity, location, and quality.

What is the function of the spinothalamic tract?

It transmits pain and temperature sensations to the brain.

What is the pathway of pain signals from nociceptors to the cortex?

Nociceptors send axons into the dorsal horn of the spinal cord, synapse on spinal neurons, which decussate and ascend to the thalamus, then to the cortex.

What are the regions involved in the motivational aspects of pain?

The prefrontal cortex, anterior cingulate cortex, insular cortex, and primary and secondary somatosensory cortices.

What is the gate control theory of pain?

A model that allows for top-down control of pain signals, suggesting that non-noxious touch can inhibit pain transmission.

How do A-beta fibers affect pain perception?

They transmit mechanical stimulation impulses and can inhibit pain signals through activation of inhibitory interneurons.

What is the descending pain modulation pathway?

A pathway where nerve signals from the somatosensory cortex and hypothalamus reach the periaqueductal grey matter, which then modulates pain transmission.

What role do endorphins play in pain management?

They are released by neurons in the medulla to inhibit pain transmission in the spinal cord.

What is the effect of morphine and opiate painkillers?

They stimulate opioid receptors in the spinal cord and brainstem to block pain.

What is the significance of the anterior cingulate cortex in pain?

It is involved in processing the emotional consequences and unpleasantness of pain.

What is the function of the insular cortex in pain perception?

It contributes to the emotional aspects of pain and its unpleasantness.

What happens to pain signals after they reach the thalamus?

They are further processed and relayed to the somatosensory cortex for interpretation.

What is neuroplasticity?

The ability of the nervous system to change in response to experience or environment.

What are the four volumetric changes in the brain due to neuroplasticity?

Neuron size, dendritic branching, synaptic changes, and addition of glial cells.

What is the difference between genotype and phenotype?

Genotype refers to stable DNA genetic information, while phenotype refers to unstable physical characteristics that can change.

What are the three cell layers developed in a human embryo?

Endoderm, mesoderm, and ectoderm.

What is the role of the neural tube in brain development?

The neural tube forms from the neural groove and develops into the forebrain, midbrain, and hindbrain.

What is neurogenesis?

The process where non-neuronal cells divide to produce neurons.

What is synaptogenesis?

The establishment of synaptic connections as axons and dendrites grow.

What are the two types of cell death in neurodevelopment?

Necrosis (passive cell death due to injury) and apoptosis (programmed cell death).

What promotes neural regeneration in the peripheral nervous system (PNS)?

Schwann cells promote regeneration.

What happens if original myelin sheaths remain after a neuron is severed?

Regenerating axons grow back to their original targets.

What is synaptic rearrangement?

The pruning and remodeling of synaptic connections, occurring later in life.

What is the sensitive period in brain development?

A time window where experiences have a particularly strong impact on brain organization.

How does experience influence neuroplasticity?

Experience alters gene expression and refines synaptic connections.

What is the relationship between environment and synaptic connections?

Environmental factors can interact with genetic factors to influence synaptic connections.

What is gating in the context of neuroplasticity?

The process related to neuromodulator release that allows the brain to turn neuroplasticity on or off in specific locations.

What role do cholinergic neurons play in neuroplasticity?

They are important in the process of gating and are active when learning new tasks.

What is the effect of damage on synaptic connections?

Loss of input can unmask existing connections, leading to long-term changes and potential new connection growth.

What is the difference between sensation and perception?

Sensation is the process of receiving information from the environment, while perception is the interpretation of that information.

What is the role of cell adhesion molecules in neural development?

They guide cellular migration and the growth of axons and dendrites.

What is the significance of neurotrophic factors?

They influence the survival of neurons and play a role in apoptosis.

What is the impact of early life experiences on brain development?

Changes and experiences early in life can have long-lasting effects on brain organization.

What happens to the prefrontal cortex during brain maturation?

It matures last and is involved in complex cognitive functions.

What is the role of glial cells in neural development?

Glial cells guide cell migration and support the growth of neurons.

What is the process of cell differentiation in neurons?

Cells express certain genes to create specific proteins necessary for their function in particular regions.

What is the effect of enriched environments on synaptic connections?

Rats in enriched environments show extensive synaptic connections compared to those in standard environments.

What is sensory transduction?

The conversion of a stimulus into a change in membrane potential in a receptor cell.

What do receptor cells do in sensory systems?

They act as transducers, converting stimuli into neural signals.

What is the role of action potentials in sensory systems?

Senses use action potentials to convey information, with distinct pathways for each sense.

What is adaptation in sensory processing?

The progressive loss of response to a repeated stimulus.

What are phasic receptors?

Receptors that display adaptation and respond to changes in stimuli.

What are tonic receptors?

Receptors that show little to no adaptation to stimuli.

What is top-down processing in sensory perception?

The process where higher brain centers suppress some sensory inputs and amplify others.

What is the somatosensory system responsible for?

Perception of touch, vibration, pain, temperature, and body position.

What are the three types of sensory systems based on stimulus origin?

Exteroceptive (external stimuli), proprioceptive (internal body position), and interoceptive (internal conditions).

What are mechanoreceptors?

Sensory receptors in the skin that transduce physical movement into neural signals.

What do Pacinian corpuscles respond to?

Vibrations and pressure, detecting texture.

What is the function of Golgi tendon organs?

They provide information about changes in muscle tension.

What is a receptive field in sensory systems?

The region of space where a stimulus will alter a sensory neuron's firing rate.

What is the dorsal column system?

A sensory pathway that delivers touch and proprioception information to the brain.

What happens in the trigeminal touch pathway?

Touch information from the face bypasses the spinal cord and enters the brain at the pons.

Where is the primary somatosensory cortex located?

In the postcentral gyrus of the parietal lobe.

What is the sensory homunculus?

A representation of the body based on cortical representation, showing areas with fine tactile discrimination.

What is the difference between primary and non-primary sensory cortex?

Primary sensory cortex processes initial sensory input, while non-primary receives projections for further processing.

What is the role of primary afferent axons?

They bring information from somatic sensory receptors to the spinal cord and brain stem.

What is the significance of dermatones?

They represent areas of skin innervated by sensory neurons from a single spinal nerve, important for identifying lesions.

What is the function of the ventral posterior nucleus of the thalamus?

It relays sensory information to the primary somatosensory cortex.

How does the somatosensory system process touch information?

Touch information enters the dorsal horn, synapses on second-order neurons, and ascends to the brain.

What is the role of adaptation in sensory receptors?

It allows receptors to become less responsive to constant stimuli over time.

What types of stimuli do exteroceptive receptors respond to?

External stimuli applied to the skin.

What is proprioception?

The sense of body position and movement, mediated by receptors in muscles and joints.

What is the function of mechanoreceptors in touch perception?

They respond to vibrations, stretching, and pressure, creating graded responses.

What is the primary function of the sensory cortices?

To process and integrate sensory information from various modalities.

What is a reflex?

A simple, stereotyped, unlearned response to a particular stimulus used to protect the body.

What is the role of the spinal cord in reflexes?

Integration occurs in the spinal cord, where impulses travel from sensory receptors to motor pathways.

What is a motor plan?

A set of muscle commands established in the brain before an action occurs, conveyed to muscles and fine-tuned via feedback.

What are the main components of the motor control hierarchy?

The hierarchy includes the brain, brainstem, spinal cord, and skeletal muscles.

What is the function of the primary motor cortex?

Responsible for the execution of voluntary movements, with neurons changing activity patterns based on movement direction.

What is the role of the cerebellum and basal ganglia in motor control?

They modulate activities of the control systems, sometimes via thalamus in a feedback loop to the cortex.

What are muscle spindles and golgi tendon organs?

They provide proprioceptive information from muscles to the central nervous system.

How are muscles organized for movement?

Muscles are organized into antagonistic pairs: extensors extend and flexors contract, with opposing patterns of excitation and inhibition.

What are upper motor neurons?

Neurons with soma in the cortex that synapse in the spinal cord after decussating.

What do lower motor neurons do?

They start in the spinal cord, exit through the anterior root, and directly command muscle contraction.

What is the neuromuscular junction (NMJ)?

The synapse between motor neurons and muscle fibers where neurotransmitters are released to cause muscle contraction.

What neurotransmitter is involved in muscle contraction at the NMJ?

Acetylcholine binds to ionotropic receptors in muscle, leading to contraction.

What is the role of the supplementary motor area (SMA)?

Important for the initiation of movement sequences, especially internal and preplanned movements.

What does the premotor cortex do?

It programs movement by combining information from the prefrontal cortex and posterior parietal cortex.

What are mirror neurons?

Neurons that fire both when making a movement and when observing another individual make the same movement, important for imitation learning.

What is the corticobulbar tract responsible for?

Controls movement of the face, tongue, and eyes, with upper motor neurons originating in the motor cortex.

What is the lateral corticospinal tract?

A pathway for movements of distal limbs, where upper motor neuron cell bodies originate in the primary motor cortex.

What is the ventral corticospinal tract?

A pathway for movement of the upper legs and trunk, with upper motor neuron cell bodies also in the primary motor cortex.

What is the significance of pyramidal decussation?

It is where axons of upper motor neurons cross over to the contralateral side of the body.

What role do cranial nerves play in motor control?

They serve as lower motor neurons for facial movements, swallowing, and other functions.

What is the function of the primary motor cortex's map of the body?

The amount of cortical area corresponds to the fineness of movement in that part of the body.

What are the basal ganglia?

A group of interconnected forebrain nuclei that modulate movement, receiving information from primary and secondary motor areas and the somatosensory cortex.

What is the primary function of the basal ganglia?

To smooth movements and automate learned movement sequences.

What are the main components of the basal ganglia?

Striatum, caudate nucleus, putamen, substantia nigra (compacta and reticulata), subthalamic nucleus, globus pallidus (internal and external segments).

How do the basal ganglia influence lower motor neurons?

They indirectly influence lower motor neurons via the thalamus and cortex.

What neurotransmitters are involved in basal ganglia circuitry?

Dopamine (DA), glutamate, and GABA.

What is the role of D1-like receptors in the basal ganglia?

They are excitatory and activate the direct pathway, causing disinhibition and activity in the thalamus and cortex.

What is the role of D2-like receptors in the basal ganglia?

They are inhibitory and activate the indirect pathway, causing inhibition of motor nuclei and cortex.