Canine Neuroanatomy Summary PDF

Anatomy of a Canine Brain ​ Meninges: Protective membranes covering the brain and spinal cord. ​ Detailed view provides insight into specific brain regions related to canine behavior, such as: ○​ Ability to distinguish chew toys. ○​ Shameless sniffing center. ○​ "Play wi...

Anatomy of a Canine Brain ​ Meninges: Protective membranes covering the brain and spinal cord. ​ Detailed view provides insight into specific brain regions related to canine behavior, such as: ○​ Ability to distinguish chew toys. ○​ Shameless sniffing center. ○​ "Play with me" processor. ○​ Responses to abandonment and guilt. ○​ Hyperactive gland and shedders information. Learning Objectives ​ Describe key anatomical structures: ○​ Where the spinal cord ends. ○​ Membranes around the Central Nervous System (CNS). ○​ Processes of Cerebrospinal Fluid (CSF) production, function, and circulation. ○​ Access points for epidural and subarachnoid spaces; safety and preferences. Central Nervous System Overview ​ Components: ○​ Brain ○​ Spinal Cord ○​ Peripheral Nervous System (PNS) ​ PNS further categorized into: ○​ Sensory (afferent) system ○​ Motor (efferent) system ​ Protective environment provided by cranial cavity and vertebral canal. Spinal Cord and Cauda Equina ​ Spinal cord terminates around lumbosacral junction. ​ Cauda equina: Cluster of spinal nerves traveling caudally in the vertebral canal past L7. ​ Symptoms of nerve root compression include: ○​ Pain in lower back. ○​ Reduced tail wagging. ○​ Difficulty defecating. ○​ Potential hind limb weakness. Cauda Equina Syndrome (CES) ​ Causes: ○​ Compression of nerve roots at lumbosacral junction. ○​ Lumbosacral stenosis due to disc degeneration or arthritis. ​ Symptoms: ○​ Lower back pain. ○​ Changes in behavior (e.g., low tail carriage). ○​ Urinary or fecal incontinence in severe cases. ​ Diagnosis: ○​ Neurologic exam, spinal palpation, radiographs. ​ Treatment:  ○​ Conservative (rest and pain meds) for mild cases. ○​ Surgical intervention (dorsal laminectomy) for severe cases. ​ Prognosis: ○​ Good with mild symptoms; guarded with incontinence. Meninges and Spinal Membranes ​ Layers of the meninges: 1.​ Dura Mater: Outermost, thickest layer, fused to periosteum in cranial cavity. 2.​ Arachnoid: Attached to dura; blood vessels present in trabeculae leading to pia mater. 3.​ Pia Mater: Innermost layer, follows gyri and sulci, involved in CSF production. ​ Fourth membrane - periosteum lining vertebral canal and skull. Cerebrospinal Fluid (CSF) Functions ​ Shock Absorption: Protects brain during movement. ​ Nutrition: Supplies essential nutrients (glucose, proteins). ​ Intracranial Pressure Regulation: Maintains constant pressure around the brain. ​ Waste Removal: Cleans up toxins through circulation. ​ Temperature Regulation: Stabilizes brain and spine temperatures. ​ Immune Function: Contains immune cells to monitor for pathogens. CSF Sampling and Access Points ​ Key sampling sites: ○​ Cerebellomedullary cistern. ○​ Lumbar (sacral) cistern. ​ Epidural Anesthesia: ○​ Used to numb specific nerves. ○​ Precautions: ​ Avoid cauda equina and venous sinuses. ​ Do not inject into CSF directly. Brain Hemisphere Control ​ The right half of the brain controls the left side of the body. ​ The left half of the brain controls the right side of the body. ​ Remark: "Only left-handed people are in their right mind." ​ Pathways of nerve impulses are crossed, indicating functional lateralization of brain function. Left-Right Brain Activity ​ Left Brain: responsible for reading words, analytical thought. ​ Right Brain: responsible for recognizing colors, creativity. ​ Task: Saying the color of words challenges left brain to read versus right brain's color recognition. Role of the Nervous System ​ Controls and coordinates essential body functions. ​ Essential for thinking, feeling, movement, and survival. ​ Integrates and responds to environmental stimuli. Environmental Interaction ​ Detection, integration, interpretation, and behavioral response are key nervous system functions. ​ Described as the most complicated of body systems (reference: Dyce, Sack & Wensing). Nervous System Functions Sensory Function ​ Function: Involves sensory receptors monitoring changes inside and outside the body. ​ Gathers sensory input for processing. Integrative Function ​ Function: Processes and interprets sensory input, decides on actions (Integration). Motor Function ​ Function: Sends information to effectors (muscles, glands, internal organs) based on integrative functions. Simplified Neural Circuit ​ Receptor to effector pathway consists of: 1.​ Skin receptor 2.​ Afferent (sensory) neuron 3.​ Interneuron 4.​ Efferent (motor) neuron 5.​ Striated muscle (effector) (Reference: Dyce, Sack & Wensing) Nervous System Subdivisions Central Nervous System (CNS) ​ Components: ○​ Brain ○​ Spinal Cord Peripheral Nervous System (PNS) ​ Components: ○​ Cranial nerves ○​ Spinal nerves PNS Functional Divisions Afferent Division (Sensory) ​ Conducts impulses toward CNS from sensory receptors. Efferent Division (Motor) ​ Conveys impulses away from CNS to effectors. Somatic vs. Visceral Systems Somatic System ​ Involves sensory and motor functions related to the outside world. ​ Responsible for voluntary movements and behavioral actions. Visceral System ​ Involves sensory and motor functions related to internal organs. ​ Controls activities like blood pressure, heart rate, glandular functions, and digestive processes. ​ Includes the Autonomic Nervous System. Autonomic Nervous System ​ Divisions: ○​ Sympathetic (mobilizes during activity) ○​ Parasympathetic (conserves energy during rest) ​ Often have opposing actions on the same organ, facilitating a balance. Nervous System Summary Components ​ CNS: ○​ Integrative control centers (brain and spinal cord). ​ PNS: ○​ Communication lines (cranial and spinal nerves). Key Functions ​ Sensory (Afferent): Conducts impulses from receptors to CNS. ​ Motor (Efferent): Conducts impulses from CNS to muscles and glands. Neurons ​ Basic building blocks of the nervous system. ​ Dendrites: conduct impulses toward cell body. ​ Axon: conducts impulses away from cell body. Spinal Cord Structure ​ White Matter: Contains myelinated axons. ​ Gray Matter: Contains cell bodies of neurons. ​ Dorsal and Ventral Roots: Connect sensory and motor neuron pathways. Brain Structure Major Parts ​ Cerebrum ​ Cerebellum ​ Brainstem (midbrain, pons, medulla oblongata) Cranial Nerves  ​ Types: ○​ Sensory ○​ Motor ○​ Mixed ​ Functionality: ○​ Includes sense functions (e.g., smell, sight) and motor actions (e.g., eye movement). Reflex Arc ​ Basic elements: ○​ Receptor ○​ Sensory neuron ○​ Integration center ○​ Motor neuron ○​ Effector ​ Types: ○​ Somatic Reflexes: Involve skeletal muscle actions. ○​ Autonomic Reflexes: Involve smooth muscle and gland regulation. Page 1 ​ Title: Autonomic Nervous System Vet Prep Structural and Functional Biology ​ Presenter: Dr. Melissa Kehl ​ Courtesy of: Dr. Terri Clark Page 2: Learning Objectives ​ Overview of Objectives: ○​ Describe the parts of a spinal nerve. ○​ Explain what a nerve plexus is and its purpose. ○​ Distinguish between sensory and motor, voluntary and involuntary functions. ○​ Differentiate between autonomic and somatic motor circuits. ○​ Describe the outflows of both Parasympathetic Nervous System (PsNS) and Sympathetic Nervous System (SNS) and their innervation targets. ○​ Outline how autonomic systems control heart functions and involvement of nerves. Page 3: Central and Peripheral Nervous Systems ​ CNS (Central Nervous System): ○​ Composed of the brain and spinal cord. ​ PNS (Peripheral Nervous System): ○​ Encompasses all nerves outside of the CNS. ○​ Starting Branches: ​ Cranial nerves and spinal nerves. ○​ Functionality: ​ Sensory (Afferent) nerves send impulses to the CNS. ​ Motor (Efferent) nerves transmit signals from the CNS. ​ Somatic: ​ Efferent, voluntary control of striated/skeletal muscles. ​ One neuron from cell body in CNS. ​ Visceral Efferent (ANS): ​ Involuntary control over smooth and cardiac muscles, and glands.  ​ Involves two neurons: one in the CNS and one in a ganglion. ​ Divided into Parasympathetic and Sympathetic divisions. Page 4: Peripheral Nervous System Overview ​ Definition: PNS includes all nerves, ganglia, and nerve plexi outside of the CNS. ​ Spinal Nerves: ○​ Total: 33 spinal nerves comprising: ​ 8 cervical nerves ​ 13 thoracic nerves ​ 7 lumbar nerves ​ 3 sacral nerves ​ 5 caudal (coccygeal) nerves. ​ Cranial Nerves: Nerves in the head referred to as I-XII. Page 5: Peripheral Nervous System Cells ​ Neurons: ○​ Nerve cells categorized into: ​ Sensory (Afferent): Transmits signals to the CNS. ​ Motor (Efferent): Sends impulses to organs, muscles, and glands. Page 6: Spinal Cord Anatomy ​ Anatomical Features: ○​ Sensory Ganglion: Area where sensory neuron cell bodies reside. ○​ Dorsal Root and Ventral Root of the spinal nerve ○​ Gray Matter: Contains cell bodies. ○​ White Matter: Contains myelinated axons. Page 7: Rami and Their Functions ​ Definition of Rami: Branches of the spinal nerve. ​ Branching: ○​ Dorsal ramus, ventral ramus, and ramus communicans. ○​ Each branch carries both sensory and motor information. ○​ Dorsal Ramus: Carries information to/from epaxial structures. ○​ Ventral Ramus: Serves the rest of the body. Page 8: Nerve Plexi and Phrenic Nerve ​ Definition: Nerve plexus is a network of intersecting nerves, e.g., brachial plexus. ​ Purpose: Ensures complete innervation throughout the body. ​ Phrenic Nerve: Root values include C5, C6, and C7. Page 9: Revisiting CNS and PNS ​ CNS: Brain and spinal cord ​ PNS: All nerves outside the CNS, including cranial and spinal nerves. ​ Efferent and Afferent Nerves: ○​ Afferent brings sensory info to CNS. ○​ Efferent sends motor commands from CNS. Page 10: Motor Subdivision of PNS ​ Efferent Pathways: ○​ Somatic Efferent: Involves one neuron for voluntary muscle innervation. ○​ Visceral Efferent: Involves two neurons for involuntary tissue innervation. Page 11: Synapses ​ Key point: Nerve impulses pass through synapses to connect neurons (passing the baton). Page 12: Review of CNS vs PNS ​ Buffering Key Information: Efferent and afferent nerves and their respective functionalities continue to be a focal point in understanding the CNS and PNS. Page 13: Autonomic Nervous System (ANS) ​ Visceral Efferent: Handles automatic body functions (e.g., digestion, respiration). ○​ Characteristics: ​ Not under conscious control. ​ Affects smooth muscle, cardiac muscle, and glands. ​ Comprises at least two neurons. ​ Has sympathetic and parasympathetic divisions. Page 14: Autonomic Nervous System - Two Neuron System ​ Preganglionic neuron: ○​ Cell body located in the CNS. ○​ Axon exits CNS and synapses onto a second neuron in a ganglion. ​ Postganglionic neuron: ○​ Cell body in ganglion. ○​ Targets organs (smooth muscle, cardiac muscle, glands). Page 15: Sympathetic vs Parasympathetic Nervous System ​ Sympathetic Nerves: ○​ Dilate pupils, inhibit salivation, raise heartbeat, dilate airways, stress responses. ​ Parasympathetic Nerves: ○​ Constrict pupils, stimulate salivation, slow heartbeat, stimulate digestive processes. Page 16: Recap of Autonomic Systems ​ Similar reiteration of key functions and roles of each nervous system division ​ PsNS changes for homeostasis and SNS activity in stress responses remain critical concepts. Page 17: Sympathetic Nervous System (SNS) ​ Functionality: ○​ Centers on the "fight or flight" response. ​ Neuroanatomy: ○​ Preganglionic neurons originate in the thoracolumbar region. ○​ Postganglionic neurons located in cervical, thoracic, or abdominal ganglia.  ○​ Referred to as the thoracolumbar system. Page 18: SNS Ganglion Synapses ​ A sympathetic preganglionic axon can synapse on a postganglionic cell body in a ganglion that is not nearby, providing flexibility in the SNS structure. Page 19: Sympathetic Trunk/Chain Ganglia ​ Ganglia Locations: Found on either side of the vertebral column, encompassing cervicothoracic ganglion and the sympathetic trunk. Page 20: Review: CNS vs PNS Terms ​ Important to reinforce the distinctions and functionalities between CNS and PNS. Page 21: Parasympathetic Nervous System (PsNS) ​ Focus: Responsible for rest and digest functions. ​ Neuroanatomy: ○​ Preganglionic neurons found in the brainstem and sacral region. ○​ Postganglionic neurons' cell bodies are located in terminal ganglia at the site of innervation. ○​ Also known as the craniosacral system. Page 22: Structural Aspects of PsNS ​ Diagrams showing preganglionic and postganglionic nerve fibers, emphasizing ganglia at the organ of innervation. Page 23: Vagus Nerve in PsNS ​ Key Structures: ○​ Contributions from the vagus nerve to the autonomic functions, including innervation of organs in the thoracic cavity. Major Divisions of the Nervous System 1.​ Central Nervous System (CNS) ○​ Composed of the brain and spinal cord. ○​ Functions as the integrative and control center. 2.​ Peripheral Nervous System (PNS) ○​ Includes cranial and spinal nerves. ○​ Serves as communication lines between the CNS and the rest of the body. Divisions of the PNS ​ Sensory (Afferent) Division ○​ Comprises somatic and visceral sensory nerve fibers. ○​ Conducts impulses from receptors to the CNS. ​ Motor (Efferent) Division ○​ Comprises motor nerve fibers. ○​ Conducts impulses from the CNS to effectors (muscles and glands). Autonomic Nervous System (ANS) ​ Sympathetic Division ○​ Mobilizes body systems during activity ("fight or flight"). ​ Parasympathetic Division ○​ Conserves energy and promotes housekeeping functions during rest. Types of Cells in the Nervous System 1. Neurons ​ Major functional units of the nervous system. ​ Electrically excitable and specialized in information processing. ​ Do not divide once matured; injuries can lead to permanent changes. 2. Neuroglial Cells (Glia) ​ Support cells in the nervous system involved in the nutrition and maintenance of nerve cells. ​ Major types include astrocytes, oligodendrocytes, and Schwann cells. Neuron Classifications Functional Classifications 1.​ Sensory (Afferent) Neurons ○​ Convey sensory information from receptors to CNS. 2.​ Interneurons (Association Neurons) ○​ Connect motor and sensory neurons within the CNS. 3.​ Motor (Efferent) Neurons ○​ Transmit information from the CNS to effectors. ○​ Includes somatic (voluntary) and autonomic (involuntary). Structural Classifications 1.​ Unipolar (Pseudounipolar) Neurons ○​ Single axonal process that branches into peripheral and central processes. ○​ Found in sensory ganglia and cranial nerves. 2.​ Bipolar Neurons ○​ Have two processes (axon and dendrite). ○​ Located in retina, inner ear, and olfactory epithelium. 3.​ Multipolar Neurons ○​ Possess one axon and multiple dendrites. ○​ Most common neuron type, found throughout the body. Neuron Anatomy Components and Functions 1.​ Dendrites ○​ Receive information from presynaptic neurons. 2.​ Cell Body (Soma) ○​ Contains organelles: nucleus, ribosomes, rER, Golgi apparatus, and mitochondria. 3.​ Axon  ○​ Conducts electrical signals away from the cell body. 4.​ Presynaptic Terminals ○​ Release neurotransmitters to send signals to neighboring neurons. Myelin and its Functions ​ Myelin Sheath ○​ Formed by Schwann cells in PNS and oligodendrocytes in CNS. ○​ Acts as electrical insulation to speed up signal conduction. ○​ Internodal segments of myelinated axons interspersed with nodes of Ranvier, supporting saltatory conduction. Membrane Potential and Action Potentials 1.​ Resting Membrane Potential (RMP) ○​ The electrical potential difference across the plasma membrane when a cell is not excited; typically around -70mV (neuron). ○​ Maintained by Na+/K+ pump and permeability differences across the membrane. ○​ Ion concentrations: higher K+ inside and higher Na+ outside the cell. 2.​ Action Potential ○​ Triggered when the membrane potential reaches a threshold. ○​ Involves sequential opening and closing of voltage-gated Na+ and K+ channels. ○​ Propagates down the axon triggering neurotransmitter release at the synapse. Neurotransmitter Release at Synapses ​ Action potentials trigger Ca2+ influx at axon terminals, leading to neurotransmitter release via exocytosis. ​ Major classes include: ○​ Amino Acids: Glutamate, GABA ○​ Amines: Acetylcholine, serotonin ○​ Catecholamines: Dopamine, norepinephrine, epinephrine ○​ Peptides: Endorphins, endogenous opioids. Summary of Action Potential Stages 1.​ Depolarization: Na+ channels open, Na+ flows in, causing less negative potential. 2.​ Repolarization: Na+ channels close; K+ channels open to restore negative potential. 3.​ Hyperpolarization: K+ continues to leave, making the inside more negative temporarily before returning to resting state. 4.​ Propagation: Action potentials propagate down the axon via passive charge spread at myelinated segments. Additional Information ​ Calcium Ions (Ca2+): Involved in synapse signaling; essential for neurotransmitter release. ​ Neurotransmitter Effects: Depends on type and receptor activated, influencing either excitatory (EPSP) or inhibitory (IPSP) potentials. ​ Conduction Velocity: Faster in myelinated fibers and larger diameters.