24-25+MPharm+L16+Overview+of+NS+for+Canvas

Overview of Nervous System

  • Conducted by Dr. Wendy Leadbeater, MPharm HS-1 at the University of Birmingham.

Learning Outcomes

  • Identify basic human tissue cell types and their functional characteristics.

  • Describe how neurons receive and process internal and external information, generate electrical signals, and communicate via synapses.

What is the Nervous System?

  • Facilitates perception and interaction with the environment.

  • Functions as the controlling, regulating, and communicating system of the body.

Organisation of the Nervous System

  • Central Nervous System (CNS): Brain and Spinal Cord

    • Efferent (Motor): Commands are sent out.

    • Afferent (Sensory): Receives signals from various senses.

  • Peripheral Nervous System (PNS): Links CNS to limbs and organs.

    • Somatic Nervous System: Voluntary control (e.g., skeletal muscle).

    • Autonomic Nervous System: Involuntary control (e.g., cardiac and smooth muscle, glands).

    • Enteric Nervous System: Specified for gastrointestinal function.

    • Sympathetics: Responsible for the "fight or flight" response.

    • Parasympathetics: Responsible for "rest and digest" functions.

  • Tracts: Ascending tracts relay sensory information; descending tracts relay motor information.

Cells of the Nervous System

  • Importance of glial cells alongside neurons.

  • Types of Glia:

    • Astrocytes: Support and spatial buffering.

      • Help in efficient signaling and form part of the blood-brain barrier (BBB).

    • Myelinating Glia:

      • Oligodendrocytes (CNS): Myelinate multiple axons.

      • Schwann Cells (PNS): Myelinate a single axon.

    • Microglia: Immune defense (phagocytic).

    • Ependyma: Line ventricular system of brain and spinal cord.

Blood Brain Barrier (BBB)

  • A protective barrier formed by tight junctions between endothelial cells.

  • Selectively permeable to small lipophilic molecules (e.g., nicotine, alcohol, gases).

  • Functions: Protects brain, controls environment, and maintains ionic balance.

Nerve Regeneration

  • Schwann cells: Myelinate single axons and allow for regeneration in the peripheral nervous system.

  • Oligodendrocytes: Involved in CNS myelination but do not support regeneration.

The CNS Protection Mechanisms

  • Physical Structures:

    • Bone: Skull and vertebrae.

    • Meninges: Protective layers around the brain and spinal cord.

    • BBB: Limits entry to harmful substances.

  • Cerebrospinal Fluid (CSF):

    • Flows through sub-arachnoid space, maintains ionic composition, and has a low volume with high turnover.

Ventricular System and Choroid Plexus

  • Ventricular System: Fluid-filled spaces that act as a shock absorber, bathes CNS cells, and maintains ionic balance.

  • Choroid Plexus: Produces CSF, regulates its ionic environment, and is located in various brain ventricles.

Pharmacological Challenges

  • Drugs must penetrate the BBB using specific mechanisms or transport means (e.g., nanoparticle delivery).

  • Drug delivery options include targeting blood-CSF-brain barrier.

Fundamental Units of the Nervous System

  • Neurons: Essential for signal transmission.

    • Dendrites: Receive incoming signals.

    • Axon Hillock: Integrates signals and initiates action potentials.

    • Axon: Conducts electrical signals to target cells.

Classification of Neurons

  • Multipolar Neurons: Most common; one axon and multiple dendrites.

  • Pseudo-unipolar Neurons: Single axon that bifurcates; typically sensory.

  • Bipolar Neurons: Single axon and one dendrite; associated with sensory systems (retina, olfactory).

Tracts versus Nerves

  • In the CNS, bundles of axons form tracts.

  • In the PNS, they form nerves.

  • Cell bodies grouped into nuclei (CNS) or ganglia (PNS).

Main Areas of the CNS

  • Brain: Divided into

    • Cerebrum: Conscious thought and memory.

    • Diencephalon: Hypothalamus and thalamus functions.

    • Brain Stem: Includes midbrain, pons, and medulla for various reflexes and functions.

    • Cerebellum: Coordination and balance.

  • Spinal Cord: Connects CNS to PNS with 31 spinal nerve pairs for specific muscle innervation.

Roles of CNS and PNS

  • CNS:

    • Responds to internal/external changes.

    • Coordinates body activities, maintains memory, and regulates essential functions (e.g., heart rate).

  • PNS:

    • Detects peripheral sensory information and sends it to the CNS.

    • Executes commands from the CNS for muscle contractions and organ functions.

Efferent Pathways of PNS

  • Somatic Nervous System: Controls voluntary functions.

  • Autonomic Nervous System: Controls involuntary functions like sympathetic (fight/flight) and parasympathetic (rest/digest).

Next Lectures

  • Focus on neuron communication, membrane potential, action potentials, and synaptic transmission.