PHR2002M-Neurotransmission-Overview.24.02.25BB (1)

Overview

Course Information

• Course Title: CNS & Neurotransmission

• Module Code: PHR2002M

• Instructor: Dr. Richard Ngomba

• Date and Time: Online, 24-02-25 from 10 am to 1 pm

• Institution: University of Lincoln

Session Outline

• Key Topics:

  • Organisation of the nervous system

  • Anatomical regions of the brain

  • Neurosynaptic transmission

  • Process of chemical neurotransmission

  • Neurotransmitters and receptors

Organisation of the Nervous System

• Understanding psychiatric disorders requires a foundation in the normal structure and function of the nervous system. It consists of two principal parts:

  • Central Nervous System (CNS): Comprising the brain and spinal cord.

  • Peripheral Nervous System (PNS): Composed of nerves that connect the CNS to the rest of the body.

  • Neural Cells: Two main types are present:

    • Neurones: Basic nerve cells responsible for transmitting messages.

    • Glial Cells: Supportive cells with various roles, including:

      • Microglia: Aid in immune defense and repair processes.

      • Macroglia: Include oligodendrocytes, Schwann cells, astrocytes, and ependymal cells, serving different supportive functions.

Structure and Function of Neurones

• Cell Body: Contains necessary biological machinery (e.g., nucleus) to sustain the neurone's life.

• Dendrites: Projections that receive signals from other neurones, often with multiple branches.

• Axon: The long part of the neurone that transmits action potentials, typically a single axon per neurone.

• Myelin Sheath: A fatty layer surrounding axons that enhances signal transmission speed. Neurones with this sheath are termed 'myelinated axons'.

• Axon Terminals: Release neurotransmitters into the synaptic cleft to transmit signals to other neurones.

Anatomical Regions of the Brain

Diencephalon

• Located between cerebral hemispheres, includes:

  • Thalamus: Relay center for sensory information (excluding smell).

  • Hypothalamus: Regulates homeostatic functions such as hunger, thirst, sleep, and circadian rhythms.

Cerebrum

• Known as the seat of intelligence, divided into hemispheres with three main regions:

  • Cerebral Cortex: Grey matter covering the brain, responsible for conscious activities.

  • White Matter: Composed of myelinated axons and glial cells.

  • Basal Ganglia: Group of nuclei involved in movement regulation.

Cerebellum

• Located at the back of the brain, crucial for motor control, balance, and fine motor skills.

Brainstem

• Involves essential involuntary functions such as heart rate and respiration.

Neurosynaptic Transmission

• Neurones communicate through synapses, where they are separated by the synaptic cleft.

• Action potentials trigger neurotransmitter release from presynaptic neurones.

• Binding neurotransmitters to receptors on the postsynaptic neuron can either excite or inhibit response via generating or preventing action potentials.

Chemical Neurotransmission Process

1. Action Potential Arrival: An action potential reaches the axon terminal.

2. Calcium Influx: Vesicles fuse with the presynaptic membrane, allowing calcium ions to enter.

3. Neurotransmitter Release: Stored neurotransmitters are released into the synaptic cleft.

4. Receptor Binding: Neurotransmitters cross the cleft and bind to postsynaptic receptors, influencing cellular actions.

5. Clearing Neurotransmitters: Neurotransmitters are removed through reuptake, astrocyte removal, diffusion, or enzyme breakdown.

Key Neurotransmitters and Receptors

Overview of Neurotransmitters

• Glutamate: The main excitatory neurotransmitter; acts on various receptor subtypes including NMDA and AMPA.

• GABA (Gamma-Aminobutyric Acid): Main inhibitory neurotransmitter, classified into GABAA, GABAB, and GABAC subtypes.

• Serotonin: Influences mood and sleep, with receptors distributed widely across the body, particularly within the CNS.

• Noradrenaline: Involved in mood regulation and arousal, binding to adrenergic receptors.

• Dopamine: Regulates movement, motivation, and reward pathways; characterized by various transmission pathways related to different behavioral functions.

Conclusion

Recommended Further Reading

1. Tortora & Derrickson. Principles of Anatomy and Physiology, 12th edition. 2009.

2. Martin. Neuroanatomy Text and Atlas, 3rd edition. 2003.

3. Kandel et al. Principles of Neural Science, 4th edition. 2000.

4. Stahl. Stahl’s Essential Psychopharmacology.