Diencephalon PDF

Diencephalon Anne Galgon PT, PhD, NCS Eric S. Pelletier PT DPT PCS Saint Joseph’s University Department of Physical Therapy  Objectives Identify the structures within the diencephalon Identify the function of the structures of the diencephalon Understand the path...

Diencephalon Anne Galgon PT, PhD, NCS Eric S. Pelletier PT DPT PCS Saint Joseph’s University Department of Physical Therapy  Objectives Identify the structures within the diencephalon Identify the function of the structures of the diencephalon Understand the pathways of neural information to and from the thalamus  Diencephalon Structures Thalamus Hypothalamus Epithalamus – Pineal Gland Subthalamus (functions as part of the basal ganglia) Pretectum Function of Diencephalon – relay station for majority of motor and sensory connections. Diencephalon Anatomy What separates the two thalami and hypothalamic?  Diencephalon Anatomy Hypothalamus Diencephalon Anatomy Diencephalon Anatomy Posterior View Thalamus This is only a representation of the thalamus interacting with the motor system, Remember it interacts with sensory system Thalamus  Thalamus Means “inner chamber” or “bedroom” in Greek Major relay station for sensory and motor information from cortex, basal ganglia, cerebellum, limbic system Large egg shaped collection of nuclei located bilaterally above the brainstem Y shaped sheet of white matter divides the thalamic nuclei into three groups o Anterior o Medial o Lateral Thalamus  Thalamus Function Regulates flow of information to cortex o Selective filter of information o Regulates the activity level of cortical neurons All sensory pathways relay in the thalamus Cerebellar, Basal Ganglia, Limbic pathways have relays here  Thalamic Nuclei Thalamic Nuclei can be divided to three functional groups: o Relay Nuclei Convey information from sensory systems (except olfactory), the basal ganglia, and cerebellum Majority of the thalamic nuclei o Association Nuclei Process emotional and some memory information or integrate different types of sensation o Nonspecific Nuclei Regulate consciousness, arousal, and attention Nuclei of thalamus (except reticular nucleus) project to the ipsilateral cerebral cortex  Relay Nuclei Receive specific information and serve as relay stations Send information directly to specific localized area of cortex  Relay Nuclei - Sensory Ventral Posterior (VP) Ventral Posterolateral (VPL) o Receive input from trunk and limbs from spinothalamic and medial lemniscus o Projects to primary somatosensory cortex o Emotions and Memory Ventral Posteromedial (VPM) o Receives taste information from medulla and vestibular information from vestibular nuclei o Emotions and Memory  Relay Nuclei - Sensory Medial Geniculate (MG) o Auditory system o Receives fibers from midbrain o Projects to auditory cortex of temporal lobe o “Medial Music” Lateral Geniculate (LG) o Visual system o Termination site of optic tract o Projects to internal capsule and optic radiation o “Lateral Light”  Relay Nuclei - Motor Ventral Anterior (VA) and Ventral Lateral (VL) o Receive fibers from basal ganglia and cerebellum o Project to motor area of frontal lobe  Association Nuclei Connect reciprocally to large areas of cortex Axons project from association nuclei to the cortex and axons project from cortex to association nuclei Distributes and gates the information between cortical structures  Association Nuclei Anterior Nucleus (AN) and Lateral Dorsal (LD) o Part of the limbic system o Involved in control of instinctive drives, emotional aspects of behavior and memory Medial Dorsal (MD) o Extensive reciprocal connections with the cortex of frontal lobe o Controls mood and emotions  Association Nuclei Lateral Posterior (LP) o Connects with sensory association area of parietal lobe Pulvinar (P) o Connections with association cortices of parietal, temporal, and occipital lobes o Behavioral orientation to visual stimuli  Nonspecific Nuclei Receive multiple types of input and project to widespread areas of the cortex Regulate consciousness, arousal, and attention Midline (M), Midline Nuclear Group (MNG), Intralaminar (I), Reticular (R). Thalamic Relays Thalamic Relays Summary Of Nuclei  Blood Supply of the Thalamus Primary blood supply is from branches of the posterior cerebral artery (PCA)  Thalamic Impairment Problems with sensation, memory, balance, and speech. It also often causes a set of symptoms known as Dejerine-Roussy Syndrome or central pain syndrome. Lesions to thalamus interrupt ascending pathways Compromises or eliminates (depending on size and severity of lesion) contralateral sensation o Usually Proprioception is most affected https://radiopaedia.org/articles/thalamic-infarct Hypothalamus  Hypothalamus Small, less than 1% brain weight Influences viscera via Autonomic NS (ANS) Regulates endocrine function Chief effector of the limbic system  Hypothalamus Integrates behaviors with visceral functions o Coordinates Eating with digestive activity Maintains homeostasis o Adjusts body temperature o Metabolic rate o Blood Pressure o Water intake and excretion o Digestion Eating, Reproductive, and Defensive behaviors  Hypothalamus Emotional expressions o Pleasure o Rage o Fear o Aversion Regulation of circadian rhythms o Coordinated with pineal gland Endocrine regulation o Growth o Metabolism o Reproductive organs  Hypothalamus Functions of Hypothalamus are carried out through regulation of pituitary gland secretions (hormones) and through efferent neural connection with the cortex o Via the Thalamus, Limbic System, Brainstem, and Spinal Cord Hypothalamus Divisions Regional divisions Anterior Hypothalamus  Anterior Hypothalamus Anterior area influences Parasympathetic Nervous System (PSNS) via projections to brainstem PSNS nuclei Anterior Hypothalamic Nuclei o Preoptic Maintain constant body temperature Lesion – central hypothermia o Supraoptic/Paraventricular Regulate water balance Lesion – Diabetes insipidus; decreased thirst response leading to hyponatremia (low sodium) o Anterior Regulate appetite and food intake Lesion – Obesity (medial); anorexia and emaciation (lateral) o Suprachiasmatic Regulates circadian rhythms Tuberal (Middle) Hypothalamus  Tuberal (Middle) Hypothalamus Blood Pressure, Heart Rate, Satiety regulated here Nuclei o Dorsomedial nucleus Feeding, drinking, body-weight regulation; circadian rhythms o Ventromedial nucleus Feeding, fear, thermoregulation Lesion – leads to obesity, chronic irritability, and aggression o Arcuate nucleus Control endocrine functions Posterior Hypothalamus  Posterior Hypothalamus Posterior area influences Sympathetic Nervous System (SNS) through projections to the lateral gray horn Posterior Hypothalamic Nuclei o Mammillary Body Play role in memory (to be discussed with limbic system) o Posterior Nucleus Thermoregulation Hypothalamic Nuclei  Hypothalamic Nuclei Functions Temperature Regulation o Posterior nucleus conserves heat o Anterior nucleus dissipates heat o Fever starts – sweating o Fever ends – chills Feeding Function o Lateral nucleus induces eating o Ventromedial nucleus inhibits eating Output from the Hypothalamus Neural output is widespread to cerebral cortex, hippocampus, amygdala, pituitary gland, thalamus, brainstem, and spinal cord Blood Supply of the Hypothalamus Penetrating branches of the anterior cerebral arteries (ACA) and anterior communicating arteries supply the anteromedial regions Penetrating branches of the posterior cerebral arteries (PCA) and posterior communicating arteries supply the posteromedial regions  Epithalamus Forms the roof of the third ventricle Houses the pineal gland Includes the choroid plexus – involved in cerebrospinal fluid production Pineal Gland Pineal Gland is an endocrine gland associated with seasonal cycles Innervated by sympathetic fibers Regulates circadian rhythms (sleep-wake cycles) Secretes Melatonin Influences secretions of pituitary gland, adrenals, parathyroids, and islets of Langerhans  Subthalamus Located superior to substantia nigra of midbrain Part of the basal ganglia circuit Involved in regulating movement – rhythmic movement Facilitates basal ganglia output nuclei Contains bundles of projection fibers Stimulation of this area is a treatment for Parkinson’s disease This is a coronal section of the cerebrum showing basal ganglia and diencephalon  Pretectum Receives binocular input Pupillary light reflex – produces change in pupil size in response to light input  Vascular Supply PCA supplies the thalamus MCA supplies the internal capsule  Clinical Case One HA is a 47 year old woman recovering from surgery to remove a benign tumor in the optic chiasm region. One day post surgery, the physical therapist arrives to assess HA. The therapist notes that the patient is unconscious and has no bedcovers, the air conditioning is on full, and fans are placed to blow across the patient’s body, yet the temperature of her skin is unusually warm. When the therapist arrives the next day, HA is warmly covered, the heater is on, and the room temperature is near 90 degrees F, yet her skin is cool. Which of the following structures is MOST LIKELY impaired? A. Corpus Callosum B. Hippocampus C. Hypothalamus D. Primary Somatosensory Cortex E. All of the above F. None of the above G. I do not know H. I do not care Which of the following structures is MOST LIKELY impaired? A. Corpus Callosum B. Hippocampus C. Hypothalamus D. Primary Somatosensory Cortex E. All of the above F. None of the above G. I do not know H. I do not care Why do you think the hospital staff is manipulating the room temperature for HA?