Intro to Nervous System-English (1) ppt

Introduction to the Nervous System

  • Presented by Kristen Stanford, Clinical System Professor at Northeastern University

  • Focus: Adrenergic and central nervous system drug effects, distinctions among major neuropathies

Overview of Neurological Tests

X-rays

  • Visualize bony structures; quick and inexpensive.

  • Diagnose issues like fractures, arthritis, and soft tissue abnormalities.

CT Scans

  • Uses multiple X-ray images to create cross-sectional views.

  • Useful for examining bones and soft tissues, diagnosing tumors, infections, and bleeding.

  • Can be performed with or without contrast.

MRI (Magnetic Resonance Imaging)

  • Utilizes strong magnetic fields and radio waves.

  • Safe for repeated use (no ionizing radiation).

  • Excellent for imaging soft tissues, particularly the brain and spinal cord.

  • Detects tumors, inflammation, and structural damage.

MRA (Magnetic Resonance Angiography)

  • Specialized MRI focusing on blood vessels.

  • Diagnoses arterial conditions like stenosis and aneurysms.

  • Important for detecting strokes and transient ischemic attacks.

PET Scans (Positron Emission Tomography)

  • Injects a radioactive tracer to visualize metabolic processes.

  • Useful for diagnosing brain tumors and Alzheimer’s disease.

Other Tests

  • Brain Scan: Utilizes radioactive tracers to assess brain function and flow.

  • Cerebral Angiography: Detects vascular abnormalities.

  • Myelography: Diagnoses spinal issues via injected dye.

  • EEG (Electroencephalogram): Records electrical brain activity; helps diagnose seizures.

  • CSF Analysis: Diagnoses infections and inflammations.

Structure of the Nervous System

Central Nervous System (CNS)

  • Comprises the brain and spinal cord.

  • The brain interprets sensory information and coordinates movement.

  • The spinal cord transmits signals between the brain and body, coordinating reflexes.

Peripheral Nervous System (PNS)

  • Includes cranial and spinal nerves.

  • Afferent pathways: Carry sensory information to the CNS.

  • Efferent pathways: Carry motor signals from the CNS to effectors (muscles/glands).

Functional Divisions of the Peripheral Nervous System

Somatic Nervous System

  • Involves voluntary control and sensory perception.

  • Sensory neurons convey information from sensory organs to the CNS.

Autonomic Nervous System

  • Regulates involuntary functions (heart rate, digestion).

  • Divided into Sympathetic (fight or flight) and Parasympathetic (rest and digest) systems.

Neurons and Supporting Cells

Neuron Structure

  • Cell Body/Soma: Contains nucleus and organelles; integrates signals.

  • Dendrites: Receive signals from other neurons or receptors.

  • Axon: Transmits electrical impulses away from the cell body.

  • Axon Terminals: Release neurotransmitters into the synaptic cleft.

Supporting Cells (Glial Cells)

  • Astrocytes: Maintain neuron health; support blood-brain barrier.

  • Oligodendrocytes: Produce myelin in CNS; speed transmission.

  • Microglia: Resident immune cells; respond to injury/infection.

  • Schwann Cells: Myelinate axons in PNS and aid in regeneration.

Neural Pathways

  • Process starts with sensory receptors detecting stimuli.

  • Sensory info converted to electrical signals, sent to the CNS for processing.

  • Motor neurons send responses to effectors, resulting in actions.

Brain Structure and Functions

Major Parts of the Brain

  • Cerebrum: Largest part; involved in cognition, perception, and movement.

    • Divided into four lobes: Frontal (executive functions), Parietal (sensory processing), Temporal (auditory, memory), Occipital (visual processing).

  • Cerebellum: Coordination and regulation of movements.

  • Brainstem: Connects cerebrum to spinal cord; regulates vital functions.

    • Midbrain: Sensory processing.

    • Pons: Relay center for signals, regulates sleep.

    • Medulla Oblongata: Controls vital functions like breathing and heart rate.

Diencephalon

  • Contains thalamus (sensory relay) and hypothalamus (autonomic functions).

Meninges & Cerebrospinal Fluid (CSF)

Meninges Layers

  • Dura Mater: Tough outer layer with two layers.

  • Arachnoid Mater: Middle layer; contains CSF in the subarachnoid space.

  • Pia Mater: Inner layer; directly adheres to brain surface.

CSF Functions

  • Cushions and protects the brain and spinal cord.

  • Maintains buoyancy, transports substances, and removes waste.

Blood Supply to the Brain

Major Arteries

  • Internal Carotid Arteries: Supply anterior parts of the brain.

  • Vertebral Arteries: Supply posterior regions, forming the basilar artery.

  • Circle of Willis: Provides collateral circulation.

Venous Drainage

  • Blood collected in dural venous sinuses, draining into internal jugular veins.

Neural Communication

  • Neurotransmitters: Chemical messengers facilitating communication between neurons.

    • Types: Acetylcholine, norepinephrine, epinephrine, dopamine.

  • Synaptic Transmission: Action potential causes neurotransmitter release, binding to receptors.

    • Mechanisms of action include reuptake, enzymatic degradation, and receptor blockade.

Pharmacology Overview

Drug Interactions with Neurotransmitters

  • Drugs can inhibit synthesis, block receptors, mimic neurotransmitters (agonists), or prolong neurotransmitter action.

  • Selectivity in Pharmacology: Indicating specific interaction with targets reduces side effects.

Adrenergic Receptors

  • Sympathetic System: Primarily uses norepinephrine; receptors include alpha (contraction) and beta (relaxation) subtypes.

  • Parasympathetic System: Uses acetylcholine; receptors include muscarinic (varied effects) and nicotinic (muscle contraction).

Key Drugs in Neuropharmacology

  • Dopamine: Used in low blood pressure and cardiac output situations; side effects include tachycardia.

  • Phenylephrine: Alleviates nasal congestion; side effects include rebound congestion and increased blood pressure.

  • Isoproterenol: Used for bradycardia; can cause increased heart rate and bronchodilation.

Rest and Digest Functions (Parasympathetic)

  • Decreases heart rate, stimulates digestion, promotes relaxation, and conserves energy.

  • Counteracts the sympathetic system, ensuring balance in body functions.

Cholinergic Effects

  • Nicotinic and muscarinic receptors produce various physiological effects; anticholinergic drugs can block these actions.

Neuromuscular Control

Differences between Spasms and Spasticity

  • Spasm: Sudden involuntary muscle contraction, can be painful and short-lived.

  • Spasticity: Chronic increased muscle tone, often due to CNS damage.

Central Pathways

  • Corticospinal Tract: Controls voluntary movement; damage leads to contralateral effects.

  • Extrapyramidal Tract: Involuntary motor regulation; dysfunction can lead to movement disorders.

Baclofen

  • Treats spasticity by acting as a GABA B receptor agonist; can cause sedation and withdrawal symptoms.