Week 4: Somatic Nervous System PT. 2 & Physiology of Pain Flashcards
Which pathway do peripheral sensations follow?
They follow specific tracts that travel to the brain via the Ascending Pathway.
What are somatosensory pathways divided by?
Based on the location of the neurons.
Which somatosensory pathways have neurons located below the neck?
Dorsal Column and Spinothalamic Tract (3 neurons each)
Which somatosensory pathways have neurons located in the head/neck?
Trigeminal Pathway
What is the Dorsal Column Sequence responsible for?
Touch and Proprioception
What are the 3 neurons of the Dorsal Column Sequence?
Dorsal Root Ganglion
Nucleus Gracilic
Postcentral Gyrus of the Cerebral cortex
What is the Spinothalamic Tract responsible for?
Pain and Temperature
What are the 3 neurons of the Spinothalamic Tract?
Dorsal Root Ganglion
Thalamus
Postcentral gyrus of the cerebral cortex
What are the 3 neurons of the Trigeminal Pathway?
Brainstem to Pons
Thalamus
Primary Somatosensory cortex
What are the steps of the Gustation Pathway?
- Facial and Glossopharyngeal Nerves
- Solitary Nucleus
- Ventral Posterior Nucleus (Thalamus)
- Gustatory Cortex (Parietal Lobe)
What are the parts of the Audition Pathway and Sound Localization?
- Vestibulocohlear Nerve
- Cochlear Nuclei (Superior Medulla)
- Brain Stem Processing
- Inferior Colliculus
Sound Localization: What is Intramural Time Difference?
Time difference in sound arrival between ears.
Sound Localization: What is Interaural Intensity Difference?
Loudness difference due to head blocking sound waves.
What are the Projections from Inferior Colliculus?
- Thalamus
- Superior Colliculus
- Medial Geniculate Nucleus
- Auditory Cortex
What is the Vestibular System responsible for?
Balance and reflexes
What are the parts of the Vestibular System and Balance?
- Vestibular Ganglion
- Head and Neck movements
- Eye and Head movements
- Vestibular Nuclei (Medulla)
Vestibular System and Balance: What is the Vestibular Ganglion?
It carries information from utricle, saccule, and semicircular canals.
Vestibular System and Balance: What are Head and Neck movements?
Controlled in response to vestibular signals.
Vestibular System and Balance: What are Eye and Head movements?
Coordinated to maintain visual attention.
Vestibular System and Balance: What is the Vestibular Nuclei (Medulla)?
It is the main termination point for axons but some have direct projections from the vestibular ganglion to the cerebellum (no synapse point in the medulla).
What are the Vestibular Pathways and Reflexes projection targets?
- Reticular formation
- Spinal cord
- Oculomotor, Trochlear, and Abducens Nuclei
- Thalamus
- Vestibular Cortex
Vestibular Pathways and Reflexes: What is the Reticular Formation?
It influences respiratory and cardiovascular functions.
Vestibular Pathways and Reflexes: What is the Spinal Cord?
It initiates spinal reflexes for posture and balance.
Vestibular Pathways and Reflexes: What are the Oculomotor, Trochlear, and Abducens Nuclei?
It influences cranial nerve signals (Vestibulo-Ocular Reflex - VOR) and compensates for head/body movement stabilizing images on retina
Vestibular Pathways and Reflexes: What is the Thalamus?
It joins proprioceptive pathway and relays message to vestibular cortex
Vestibular Pathways and Reflexes: What is the Vestibular Cortex?
It is conscious equilibrium perception.
What are the parts of the Vision and Optic Nerve Connections?
- Complex Connections
- Visual Information Segregation
- Decussation at Optic Chiasm
- Lateral Retina Axons
- Visual Field Processing
Vision and Optic Nerve Connections: What are Complex Connections?
They are more intricate than other cranial nerves.
Vision and Optic Nerve Connections: What is the Visual Information Segregation?
They are divided between left and right visual fields.
Vision and Optic Nerve Connections: What is the Decussation at Optic Chiasm?
They are where the medial retina axons cross over.
Vision and Optic Nerve Connections: What are the Lateral Retina Axons?
They do not cross over.
Vision and Optic Nerve Connections: What is Vision Field Processing?
Left visual field processed on the right side of the brain.
Right visual field processed on the left side of the brain.
What are the 3 major targets of the Optic tract?
- Lateral Geniculate Nucleus (Thalamus)
- Superior Colliculus (Midbrain)
- Suprachiasmatic Nucleus (Hypothalamus)
What is the Optic Tract?
It extends from the optic chiasm.
Optic Tract: What is the Lateral Geniculate Nucleus (Thalamus)?
It projects to the visual cortex in the occipital lobe.
Optic Tract: What is the Suprachaismatic Nucleus (Hypothalamus)?
It receives input from photosensitive retinal ganglion cells (RGCs).
What is the Diencephalon?
Part of the brain comprised of the thalamus and hypothalamus.
What is the Thalamus responsible for?
It relays communication between the cerebrum and the rest of the nervous system.
Important for most special senses (Taste, Hearing, Vision, Balance)
What are the 3 Nuclei of the Thalamus?
Anterior Nucleus
Medial Nucleus
Lateral Nuclei
Thalamus: What are Anterior Nuclei for?
They relay messages between the hypothalamus and limbic system (emotions/memory)
Thalamus: What are Medial Nuclei for?
They relay information from the limbic system and basal ganglia to cerebral cortex (memory/alertness)
Thalamus: What are Lateral Nuclei for?
They are where specific/somatic senses connect and are relayed to the appropriate sensory cortex of the cerebrum
What is the Hypothalamus responsible for?
- Somatic functions (voluntary movements of skeletal muscles)
- Autonomic functions. (involuntary functions of smooth/cardiac muscles and glands)
- Communicates with limbic system (controls emotions/memory functions)
Thalamus: What are Sensory Inputs?
Collection of several nuclei categorized into anatomical groups (defined by white matter) and are where conscious sensory perception begins
What is Cortical Processing?
Somatosensory receptors in the body are mapped onto the somatosensory cortex (within parietal lobe-postcentral gyrus), depicted using a sensory homunculus
What are the 3 parts of the Sensory Processing in the Cerebral Cortex?
Primary Sensory Cortex
Association Area
Multimodal Integration Area
What is the Primary Sensory Cortex (sensory processing in the cerebral cortex)?
The initial processing of sensory information
What is the Associated Area (sensory processing in the cerebral cortex)?
The further processing and integration of sensory data
What is the Multimodal Integration Area (sensory processing in the cerebral cortex)?
It combines information from different senses
What 4 parts make up the Visual Association Cortex?
Primary Visual Cortex (V1)
Surrounding Areas (V2 & V3)
Visual Processing/Information Flow
What is the Primary Visual Cortex (V1) of the visual association cortex?
It is the initial visual processing in the occipital lobe.
What is the Surrounding Areas (V2 and V3) of the visual association cortex?
It is visual association cortex, meaning it adds colour and motion information.
What are the 2 streams of Visual Processing/Information Flow?
To the Temporal Lobe (Ventral Stream) or the Parietal Lobe (Dorsal Stream)
What is the Ventral Stream (temporal lobe)?
Identifies visual stimuli and their significance.
Interacts with non-visual cortex and important for memory.
Determines “what it is”.
What is Dorsal Stream (parietal lobe)?
Locates objects in space and guides body movements in response to visual stimuli.
Interacts with somatosensory cortex and influences frontal lobe matter functions.
Determines “where it is”.
What is Cortical Processing?
Sensory stimuli get registered through receptor cells and information is relayed to the CNS along the ascending pathway to the cerebral cortex (primary sensory area).
Sensory stimuli then get sent to different areas of the brain (associative sensory area) and this leads to sensory perceptions being incorporated into memory or, more importantly into a response (integrative sensory areas)
What is the executive function of the Prefrontal Cortex?
It is Goal-Directed Behaviours
What is a working memory?
“Mental Scratch Pad” for organizing information
What is the Prefrontal Cortex responsible for?
Responsible for aspects of attention (i.e. inhibiting distracting thoughts/actions) to help focus on goals and direct behaviours to achieve goals.
What is the Primary Motor Cortex?
It is located in pre central gyrus of the frontal lobe.
It receives input from several areas that aide in planning movement with eh principle output stimulating spinal cord neurons to stimulate skeletal muscle contractions.
What is a Motor Homunculus?
Neurons arranged in similar fashion to primary somatosensory cortex-i.e. it has topographical map of body
What is Precentral Gyrus?
MOTOR outputs (descending pathways)
What are Postcentral Gyrus?
SENSORY inputs (ascending pathways)
What are the 2 parts of the Secondary Motor Cortex?
The Premotor Cortex and the Supplemental Motor Areas
What is the Premotor Cortex?
It aides in controlling movements of core muscles to maintain posture during movement
What is the Supplemental Motor Area?
It is involved with planning/coordinating movement, manages sequencing of motor movements, attainment of motor skills
What are the 2 areas specialized for motor planning centers?
Frontal Eye Fields and Broca’s Area
What do Frontal Eye Fields do (specialized for motor planning centers)?
They are responsible for moving eyes in response to visual stimuli (direct connection to superior colliculus)
What does Broca’s area do (specialized for motor planning centers)?
It is responsible for controlling speech production, if area is damaged, leads to expressive aphasia (Broca’s aphasia), one understands speech but cannot produce it
What are Descending Motor Output Pathways?
Output descending from the cortex to brain stem and spinal cord
What are Betz Cells?
Large neurons in the primary motor cortex synapse with lower motor neurons in brain stem or spinal cord
What are the Two Descending Pathways travelled by axons of Betz cells?
The Corticobulbar Tract
The Corticospinal Tract
What is the Corticobulbar Tract?
From cortex to brain stem.
Axons are ipsilateral (project from cortex>motor nucleus on same side of body)
What is the Corticospinal Tract?
From cortex to spinal cord.
Axons are contralateral (cross midline of brain stem or spinal cord and synapse on opposite side of body)
What are the 7 steps of the Corticospinal Tract Pathway?
- Descent from cortex through deep white matter of cerebrum.
- Passes between caudate nucleus and putamen (internal capsule).
3.Tract then passes through midbrain (cerebral peduncles). - Burrows through pons.
- Stimuli enters Medulla, large white matter tract (pyramids).
- Fibers cross to opposite side of brain (pyramidal decussation)
- Tract splits into two parts, controlling different musculature domains
What is Appendicular Control?
The axons that control our appendages
What is Lateral Corticospinal Tract (appendicular tract)?
Fibers that cross midline at point of decussation
Lateral Corticospinal Tract: What is Cervical Enlargement?
Larger than lumbar due to greater fine muscular control required in upper limbs (ie. Fingers)
Lateral Corticospinal Tract: What is Lumbar Enlargement?
Not as prominent due to less fine motor control required in lower limbs
What is Axial Control?
The axons that control our trunk
What is the Anterior Corticospinal Tract (ACT)?
Axons do not decussate in medulla.
Remain in anterior position as they descend brain stem and enter spinal cord.
Axons travel to spinal cord level at which they synapse with a lower motor neuron.
What are Extra Pyramidal Controls?
They lie outside corticospinal tract and includes the pyramids
What is the Tectospinal Tract?
It projects from midbrain to spinal cord, important for postural movements
What is the Reticulospinal Tract?
It connects reticular system (diffuse region of gray matter in brain stem) with spinal cord, influences posture, locomotion, contributes to muscle tone and influences autonomic functions
What is the Vestibulospinal Tract?
It connects brain stem nuclei of vestibular system with spinal cord, allows for modulation of posture, movement, balance on basis of equilibrium info provided by vestibular system
What is the Rubrospinal Tract?
It controls corrective commands to the spinal cord when there are conflicts between motor commands and body position
What is the Ventral Horn Output?
Lower motor neurons responsible for muscle contraction are found in the ventral horn of the spinal cord
What is the Neuron Structure?
Large, multipolar with dendrites around the cell body.
What is an Axon Pathway:
Extends from ventral horn, travels through ventral nerve root, joins spinal nerve.
What is an Axon Length?
It is long to reach peripheral muscles; some up to a meter (e.g., lumbar motor neurons innervating muscles of first digits of the feet).
What are Branches of the ventral horn output?
Can innervate multiple muscle fibers (motor unit), contribute to precision of control of muscle, connect at the neuromuscular junction
What are Reflexes?
They are automatic and involuntary responses to specific stimuli, often preventative and protective, and maintain stability of the body.
What is Pain?
Painful stimuli travels through the central nervous system via the pain pathway to the brain where the brain processes and initiates a response.
What is a Nociceptor?
A nociceptor is designed to respond to potentially damaging stimuli by sending nerve signals to the spinal cord and brain.
What is the 5 steps in the Physiological Process of Pain?
- Nociception
- Transduction
- Transmission
- Perception
- Modification
What is Step 1: Nociception?
Nociception is the process by which the body sends painful stimuli from the peripheral nervous system to the brain, where it is processed, and a response is formed.
What is Step 2: Transduction?
It occurs when activated nociceptors in the peripheral nervous system send a pain signal to the central nervous system, starting in the dorsal root of the spinal cord.
What is Step 3: Transmission?
- After the nociceptive signal is activated, transmission of pain sends the pain signal through the central nervous system.
The pain signal is sent from the spinal cord to the nucleus of the brain stem, which initiates the brain’s perception of pain.
The brain then localizes the pain and creates an appropriate physical or emotional response.
What is Step 4: Perception?
After the brain stem receives the pain signal, it is sent to the cerebral cortex where the brain perceives the severity of the pain and activates the body’s defense to the perceived threat.
What is Step 5: Modification?
The modification of pain occurs when the brain changes the intensity of the pain signal based on the situation that originated the pain signal to protect the body.
What is the Gate Control Theory of Pain?
The gate control theory states that the central nervous system can use neurological “gates” to determine when pain is felt. These “gates” determine which pain signals are allowed through to the brain and acts as a survival mechanism for the body.
EX. When the “gates” are open, the pain signal can travel to the brain and be perceived as pain. When the “gates” are closed, the pain signal is blocked from traveling to the brain.
What are Biological Factors affecting pain?
Age
Brain function
Cognitive function
Genetic sensitivity
Hormones
Illness
Injury (past or present)
Medical diagnosis
Nociception
Obesity
Source of pain
What are Psychological Factors of pain?
Anxiety
Attitudes
Beliefs
Coping mechanisms
Developmental stage
Emotional status
Expectations
Fatigue
Fear
Meaning of pain
Memory
Mood
Sleep
Stress
What are Social Factors of pain?
Culture
Education
Environment
Ethnicity
Social support
Socioeconomic status
Spirituality
Values
What are the 3 CLASSIFICATION of pain?
Acute
Chronic
Breakthrough
What is acute pain?
Short in duration (few seconds-months) and caused by an acute event.
What is chronic pain?
Pain lasts longer than six months.
What is breakthrough pain?
Acute pain that exists along with chronic pain.
What are the 4 TYPES of pain?
Cutaneous Pain
Visceral Pain
Somatic Pain
Referred Pain
What is Cutaneous pain?
Arising from skin, can sometimes become chronic.
EX. diabetes, autoimmune disease, rashes, skin lesions (cuts, shingles, burns etc.)
What is Visceral pain?
Arising from organs such as kidneys (nephritis), gallbladder (gallstones), appendix (appendicitis).
Organs are sensitive to stretch, ischemia, inflammation, pain is diffuse/difficult to locate “deep, sharp, squeezing, pressure” and often accompanied by nausea/vomiting/change in vitals (temp, tachy, low BP)
What is Somatic pain?
Can be superficial or deep, ligaments, tendons, bones, blood vessels, fascia, and muscles, “dull, aching, throbbing”, may show outward signs of injury (burns, swelling, bruising, incisions)
What is referred pain?
The injury/lesion is at one site, but the pain is at another, occurs when both sites are innervated by the same spinal nerve and the brain can’t determine the original site of injury.
EX. Myocardial Infarction (MI/heart attack); pain is often felt in the left arm.
What are the 3 Etiologies of pain?
Nociceptive Pain
Neuropathic Pain
Idiopathic Pain
What is Nociceptive pain?
Originates in PNS (somatosensory receptors), mechanical/chemical cause, r/t degree of injury (mild-stubbing toe Vs. Severe-burns from house fire)
What is Neuropathic pain?
A lesion or disease in the peripheral or central nervous system causing abnormal processing of the stimuli (may be tingling, burning, ‘shooting’, numbness).
What is Idiopathic pain?
Pain without a known cause or unknown origin (eg. Fibromyalgia, multiple sclerosis, headaches, irritable bowel disease, typically a chronic pain, difficult to diagnose and treat
