Lecture 30 Outline of Last Lecture I. The spinothalamic tract consists of lateral and dorsal pathwaysII. Pain is an unpleasant sensory and physical experiencea. Responses to pain may be “initial” or “later”b. There are many classifications of pain depending on certain psychological and physiological factorsIII. Nociceptors detect damage or potential damagea. Responsive to mechanical, chemical, or thermal stimuliIV. Perceiving pain occurs in the frontal lobeOutline of Current Lecture I. Pathways from the lateral spinathalamic tract extend to:a. Reticular formation and periaqueductal grayb. Tectumc. Amygdalad. HypothalamusII. Visceral pain has the following characteristics:a. Wide variance of sensitivityb. Weak pain and injury relationshipc. Is diffuse/poorly localizedd. Exhibit exaggerated autonomic responsesIII. The hypothalamus performs acute and chronic stress responsesa. Controls many preganglionic spinal cord neuronsIV. The Gate Theory of Pain claims that different sensory pathways compete for arousal and perception in response to a stimulia. Certain methods reduce our perception of pain by inhibiting nociceptive receptorpathwaysV. Stimulation of the periaqueductal gray matter reduces perception of painVI. The vestibular system is responsible for orienting movements and controlling balancea. Semicircular canals and otolith organs work together to help us perceive our body’s position in spacei. Utricle and sacculeVII. The secondary somatosensory cortex receives input from the primary somatosensory cortexa. Gives rise to dorsal and ventral streams in nearby cortical regionsVIII. Aggression has a neural basis in the periaqueductal gray and hypothalamusa. There are numerous subcategories of aggressive behaviorsCurrent LectureThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. NSCI 110 1st Edition- Pathways from the anterolateral system/lateral ST tract have extensive connections:o Reticular formation and periaqueductal gray (arousal)o Tectum (orienting responses)o Amygdala (emotional responses)o Hypothalamus (hormonal and cardiovascular responses)- Unique features of visceral pain (internal organs)o Wide variance of sensitivity  Liver has low sensitivity to pain Urethra has high sensitivityo Pain and injury relationship is weak GI tract  burning is not perceived but twisting is excruciating The heart is extremely sensitive to decreased blood flowo Is diffuse/poorly localized Referred to the peripheryo Exaggerated autonomic reactions such as increased sweating, paleness, blood pressure changes, heart rate- Hypothalamus’ role in autonomic controlo Drives preganglionic cells’ activityo Acute stress response: Hypothalamus  sympathetic innervation of adrenal medulla  epinephrine release (occurs between post ganglionic cell and target cells)o Chronic stress response: Hypothalamus  anterior pituitary gland  adrenal cortex  cortisolo Hypothalamus controls thousands of preganglionic cells in the spinal cord- Gate Theory of Pain states that activities in different sensory pathways compete for arousal and perceptiono Competition between dorsal ST tract and lateral ST tracto Haptic-proprioceptive stimulation can reduce pain perception by activating inhibitory interneurons that reduce nociception o Acupuncture and massage therapy can reduce our perception of pain- Periaqueductal gray mattero When stimulated can decrease our perception of paino Can activate brainstem pathways that project to the dorsal spinal cord to inhibit lateral ST tract neuronso Some neurons project to the hypothalamus (autonomic regulation) and amygdala (regulating emotion)- The vestibular system and balanceo Each ear’s vestibular organ consists of three semicircular canals and otolith organs (utricle and saccule)o Vestibular organ functions include: Body position in relation to gravity Changes in direction and speedo Any head motion causes the movement of endolymph (fluid) in semicircular canals This pushes the cilia of hair cells in the cochlea, causing them to bend Cilia bending causes hair cell receptor potentials and action potentials in the neurons of the vestibular nerve Depolarization (move to right) and hyperpolarization (move to left)o The utricle and saccule also contain hair cells embedded within a gelatinous substance that contains otoconia (made of otoliths  calcium carbonate crystals) Movement causes a shift of the gelatinous substance and the cilia bend, generating action potentials in vestibular nerve axonso Somatosensory cortex receives sensory input Secondary cortex receives input from primary somatosensory cortex Refines the construction of perceptions and projects to the frontal cortex Primary cortex is organized into four separate homunculi This cortex confirms that movements have occurred- Damage  does not disrupt movement plans but disrupts how movements are performed (their execution may be fragmented)- Apraxia is the inability to complete a plan of action accurately This cortex is a node for the dorsal and ventral streams and signals widely to the motor cortex- Dorsal (how) streamo Works without conscious awarenesso Vision for actiono Visual and somatosensory info integrated for appropriate movemento Shapes and directs hand while grasping- Ventral (what) streamAGGRESSION- Neural basiso Stimulation of the periaqueductal gray in the midbrain and the hypothalamus change aggressive responseso Temporal lobe tumor induced assault without provocation- Aggression is behavior that causes harm, damage, or destructiono How to categorize?  It is often expressed as a mix of types - Affective  associated with fear/threat, reaction, defensive- Predatory  proactive, premeditated aggression o Affective aggression in cats: hissing, ears flat, body low, higher blood pressure and heartrate, piloerection, paw striking Stimulation of medial hypothalamus or dorsolateral PAG Cerebral cortex not essentialo Predatory aggression in cats: highly directed to prey item, stalking, aiming to bite back of neck of prey Stimulation of lateral hypothalamus or ventral PAG Cerebral cortex