Neuroanatomy - Head & Neck Anatomy PDF

Neuroanatomy Naida Jakirlic, OD, FAAO Head & Neck Anatomy Fall 2024 Learning Objectives ▪ Review major divisions of the brain ▪ Identify the main features and functions of a neuron ▪ Identify the major features and functions of the telencephalon, including corpus callosum, hippocampus, amygdal...

Neuroanatomy Naida Jakirlic, OD, FAAO Head & Neck Anatomy Fall 2024 Learning Objectives ▪ Review major divisions of the brain ▪ Identify the main features and functions of a neuron ▪ Identify the major features and functions of the telencephalon, including corpus callosum, hippocampus, amygdala, and the basal nuclei ▪ Identify the location, features, and functions of the thalamus and hypothalamus ▪ Identify the location, features, and functions of the pituitary gland ▪ Identify the location, features, and functions of the brainstem ▪ Describe the major features and functions of the cerebellum 2 Organization of the Nervous System ▪ Central Nervous System (CNS) ▪ Brain ▪ Spinal cord ▪ Peripheral Nervous System (PNS) ▪ Cranial nerves: 12 pairs ▪ Spinal nerves: 31 pairs Organization of the PNS ▪ Dorsal roots: carry sensory information to the spinal cord ▪ Ventral roots: carry outgoing motor axons from the spinal cord ▪ PNS is arranged on 2 axes: ▪ Longitudinal: rostral to caudal ▪ Dorsal to ventral: back to front Neurons ▪ Electrically excitable cells of the nervous system ▪ Make up the brain and nervous system ▪ Consist of ▪ Cell body (soma) ▪ Dendrite ▪ Axon ▪ Axon terminal www.neuroanatomy.ca Types of Neurons ▪ Sensory neurons: pseudounipolar ▪ Motor neurons: multipolar Supporting cells of nervous system ▪ Aka neuroglia ▪ Not involved in conducting action potential ▪ Provide mechanical support to neurons ▪ Serve as insulators and prevent neuronal impulses from spreading in unwanted directions ▪ Types ▪ Astrocytes: blood brain barrier ▪ Microglia: main immune defense in the CNS ▪ Schwann cells: produce myelin sheath in the PNS ▪ Oligodendrocytes: produce myelin sheath in the CNS Nervous System Cells Nerve cells: neurons Glial cells: glia Divisions of the Brain ▪ Cerebrum (aka forebrain) ▪ Cerebral hemispheres: cerebral cortex, white matter, basal ganglia ▪ Thalamus and hypothalamus (aka inter-brain) ▪ Cerebellum ▪ Brainstem (aka hindbrain) ▪ Midbrain: contains cranial nerve nuclei, cerebral peduncle, cerebral aqueduct ▪ Pons: contains cranial nerve nuclei, motor tracts, fourth ventricle ▪ Medulla oblongata: contains cranial nerve nuclei, motor tracts, fourth ventricle 10 Cerebral Cortex ▪ Convoluted outer surface ▪ Grooves: sulci ▪ Elevated regions: gyri ▪ Contains ~12 billion neurons Gray and White Matter Gray matter ▪ Nerve cell bodies ▪ Dendrites White matter ▪ Myelinated axons Gray & White Matter ▪ Brain: gray matter lies external to white matter ▪ Spinal cord: white matter surrounds spinal core of gray matter www.neuroanatomy.ca Axial cut Corpus Callosum ▪ C-shaped nerve fiber bundle ▪ Connects right and left cerebral hemispheres ▪ Largest collection of white matter tissue in the brain ▪ Forms majority of the roof of the lateral ventricles Limbic System Group of brain structures responsible for emotions and memory ▪ Hippocampus ▪ Amygdala ▪ Thalamus ▪ Hypothalamus ▪ Basal ganglia ▪ Cingulate gyrus The Limbic System The Hippocampus ▪ Involved in formation of new memories – one site in the brain where new neurons are made from adult stem cells ▪ To visualize, take coronal cut from the brain through the temporal lobe ▪ On the coronal cut, the hippocampus is in the part of the temporal lobe that appears to be curled in on itself The Amygdala ▪ Emotion center of the brain: pleasure, fear, anxiety, anger ▪ Strengthens emotional content of memories ▪ Also located in the temporal lobe Basal Ganglia ▪ Subcortical structures found deep within the brain ▪ Consist of five pairs of nuclei that receive information from the cortex about upcoming movement in order to fine-tune movement ▪ The basal ganglia process and adjust movement information from the cortex ▪ Damage to basal ganglia results in difficulty starting, stopping, or sustaining movement (parkinsonism) Basal Ganglia Components: ▪ Caudate nucleus Striatum ▪ Putamen ▪ Globus pallidus: cerebrum ▪ Subthalamic nucleus ▪ Substantia nigra: midbrain The Striatum ▪ The striatum is a group of contiguous subcortical structures including ▪ Caudate nucleus: cognitive processing ▪ Putamen: motor control ▪ Nucleus Accumbens: motivation Thalamus & Hypothalamus ▪ Thalamus ▪ Relay center: processes & distributes all sensory & motor information going to/from the cortex ▪ Links nervous & endocrine system ▪ Emotional control ▪ Hypothalamus ▪ Regulates autonomic nervous system ▪ Controls body temperature, thirst, hunger, emotional behavior Thalamus ▪ Paired structure located on lateral aspects of the third ventricle ▪ Mostly composed of gray matter ▪ Central relay station of sensory impulses from the body to the cerebral cortex Hypothalamus ▪ Maintains homeostasis, hormonal regulation, autonomic control, and instinctual drives ▪ Has many nuclei ▪ Works closely with the pituitary gland to modulate endocrine activity Pituitary Gland ▪ Aka hypophysis ▪ Pea-sized ▪ Attached to hypothalamus by the pituitary stalk (aka infundibulum) ▪ Master gland: controls activity of most hormone-secreting glands ▪ Located immediately beneath the optic chiasm (clinical correlation: bitemporal hemianopia Brainstem ▪ Information channel between brain and spinal cord ▪ Composed of midbrain, pons, and medulla ▪ Contains most of the cranial nerve nuclei ▪ Produces many of the brain’s neurotransmitters ▪ Control center for basic bodily functions: ▪ Respiration ▪ Cardiac rhythm ▪ Urination and bowel movements ▪ Sexual functions https://youtu.be/Mkj78h8w4a8 Midbrain ▪ Superior colliculus: relay station for eye movements ▪ Inferior colliculus: relay station for hearing ▪ Medial longitudinal fasciculus: fibers coordinating movement of eyes ▪ Medial lemniscus: relays sensations of touch and proprioception to the cortex ▪ Cerebral peduncle: delivers motor information from cortex to cerebellum and spinal cord ▪ Cerebral aqueduct: carries CSF from third to fourth ventricle ▪ CN III and IV nuclei Pons ▪ Contains several cranial nerve nuclei: CN V, VI, VII, VIII ▪ Contains nuclei that relay signals from the forebrain to the cerebellum ▪ Contains nuclei that deal with sleep, respiration, swallowing, bladder control Medulla Oblongata ▪ Most caudal part of brainstem ▪ Motor and sensory pathways converge ▪ Contains breathing center ▪ Continuous with spinal cord caudally ▪ Rostral medulla: open medulla because it opens onto the fourth ventricle ▪ Anterior surface contains pyramids (descending motor tracts) ▪ Contains CN IX, X, XII nuclei  Brainstem – Anterior Surface https://skfb.ly/6XPPM Brainstem – Posterior Surface Brainstem – External Anatomy Cerebellum ▪ Mostly white matter covered with thin layer of gray matter ▪ Receives sensory input from spinal cord, motor information from cerebral cortex, and input about balance from the inner ear ▪ Coordinates planning & timing of voluntary muscle movement ▪ Maintains balance Cerebellum ▪ Posture and balance ▪ Coordination of movement ▪ Skill formation https://skfb.ly/6QURI 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