bio lecture 9

Nervous System Overview

  • Presenter: Sofia Khan, PhD student in human health sciences at the University of Guelph

  • Main Focus: The nervous system

Introduction

  • Sofia's academic background:

    • Bachelor's degree in Biomedicine at University of Guelph

    • Master's degree from University of Guelph

    • Currently in a PhD program

Nervous System Structure

  • The nervous system is divided into two main systems:

    1. Central Nervous System (CNS)

      • Comprises the brain and spinal cord

    2. Peripheral Nervous System (PNS)

      • Consists of somatic and autonomic nervous systems

  • Somatic Nervous System:

    • Involves conscious activities such as movement and sensory functions

    • Nerves connect to skin and muscles

  • Autonomic Nervous System:

    • Governs unconscious activities

    • Regulates bodily functions without conscious control

Control and Communication Network (CCM)

  • Other systems include:

    • Endocrine system

    • Local support and defense system

  • Focus will primarily be on the nervous system

Video Overview

  • Video provides a general overview of the nervous system

  • Additional resources for students to view the video themselves

Peripheral and Central Nervous System Functions

  • Peripheral Nervous System (PNS):

    • Sensory Input: Signals from sensory receptors sent to CNS

    • Motor Output: Actions and bodily functions controlled by CNS

  • Central Nervous System (CNS):

    • Integrates sensory information and directs responses

  • Example of reflex action:

    • Touching something hot activates sensory receptors

    • Information relayed to CNS results in a quick withdrawal of hand

Motor System Output

  • Two subdivisions:

    1. Somatic Nervous System:

    • Voluntary movements (e.g., catching a frisbee)

    1. Autonomic Nervous System:

    • Involuntary activities (e.g., heart rate, digestion)

      • Mnemonic: Autonomic = Automatic

Autonomic Nervous System Subdivisions

  • Parasympathetic Nervous System:

    • Promotes rest and digest functions

    • Functions improve bodily activities during calm states

  • Sympathetic Nervous System:

    • Activates fight or flight response in stressful situations

    • Increases dopamine and norepinephrine levels

    • Example: Running from a bear elevates heart rate and alertness

Neurons and Glial Cells

  • Main Cell Types in the Nervous System:

    1. Neurons

    2. Glial Cells:

    • Oligodendrocytes, Schwann Cells, Astrocytes, Microglia, Ependymal Cells

  • Neurons:

    • Function: Transmit signals throughout the nervous system

    • Structure:

      • Dendrites: Receive information

      • Axon: Sends impulses down the neuron

    • Speed of transmission influenced by myelination

    • Example of signal transmission:

      • Action potentials move along neurons and trigger synapses

Myelination and Signal Speed

  • Myelination:

    • Myelin sheath increases speed and efficiency of action potentials

    • Nodes of Ranvier: Gaps in the myelin where action potentials occur

    • Speed Comparison:

      • Unmyelinated Neuron: 0.5−2extm/s0.5 - 2 ext{ m/s}

      • Myelinated Neuron: 6−120extm/s6 - 120 ext{ m/s}

  • Multiple Sclerosis (MS):

    • Characterized by myelin destruction leading to slower signal transmission

    • Symptoms include impaired movement due to slow action potentials

Neurotransmitters

  • Neurons typically release a specific neurotransmitter

  • Types of Neurons:

    • Dopaminergic Neurons: Exclusively release dopamine

  • Neurons can release either excitatory or inhibitory neurotransmitters, influencing action potentials

  • Teeter Totter Model:

    • Balance of neurotransmitters determines neuronal firing

Neuronal Networks and Development

  • Neurons can diverge and converge to form networks

  • Growth occurs significantly during childhood and adolescence

  • Dopamine Sensitivity:

    • Increased sensitivity contributes to risk-seeking behaviors in teenagers

  • Myelination Increase:

    • Continuation into teenage years enhances signaling efficiency

Types of Glial Cells

  • Oligodendrocytes vs. Schwann Cells:

    • Oligodendrocytes:

      • Produce myelin in CNS, act on multiple axons

    • Schwann Cells:

      • Produce myelin in PNS, act on single axons

  • Astrocytes:

    • Functions:

    1. Regulate blood-brain barrier

    2. Coordinate ventricular function

    3. Support nodes of Ranvier function

    4. Form tripartite synapses with 2 neurons

    5. Facilitate calcium signaling in networks

  • Microglia:

    • Immune cells providing defense within CNS

  • Ependymal Cells:

    • Line brain ventricles, produce cerebrospinal fluid (CSF)

Blood-Brain Barrier

  • Structure: Tightly controlled, selective permeability to protect CNS

  • Allows only specific substances to enter CNS, such as:

    • Lipid-soluble compounds (e.g., alcohol, caffeine)

    • Glucose (via GLUT1 transporter, not insulin-sensitive)

  • Implications for drug delivery to CNS

    • Challenges in targeting drugs effectively due to barrier

    • Some medications must bypass to be effective, while others should not affect CNS

Concluding Remarks

  • Invitation for questions from students

  • Offer to communicate via email for further inquiries

  • Wish for successful understanding of the nervous system concepts