CNS 1

1st Year Syllabus Overview

  • Blood Physiology

  • Cell Physiology

  • Central Nervous System Physiology

  • Autonomic Nervous System Physiology

1st Year Lecture Schedule

  • Lecture No: 1
    Date: 7/2/2026
    Title: Blood Physiology
    Exam Date: 2/3/2026

  • Lecture No: 2
    Date: 14/2/2026
    Title: Blood Physiology

  • Lecture No: 3
    Date: 21/2/2026
    Title: Blood Physiology

  • Lecture No: 4
    Date: 28/2/2026
    Title: Blood Physiology

  • Lecture No: 5
    Date: 7/3/2026
    Title: Cell Physiology
    Exam Date: 26/3/2026

  • Lecture No: 6
    Date: 14/3/2026
    Title: Cell Physiology

  • Lecture No: 7
    Date: 21/3/2026
    Title: Cell Physiology

  • Lecture No: 8
    Date: 28/3/2026
    Title: Central Nervous System
    Exam Date: 16/4/2026

  • Lecture No: 9
    Date: 4/4/2026
    Title: Central Nervous System

  • Lecture No: 10
    Date: 11/4/2026
    Title: Central Nervous System

  • Lecture No: 11
    Date: 18/4/2026
    Title: Autonomic Nervous System

  • Lecture No: 12
    Date: 25/4/2026
    Title: Autonomic Nervous System

  • Lecture No: 13
    Date: 2/5/2026
    Title: Autonomic Nervous System

Central Nervous System

Overview

  • Presented by Dr. Ibrahim Said Abu-alya, Assistant Professor of Physiology, Faculty of Veterinary Medicine, University of Sadat City.

Learning Objectives

  1. Students will be familiar with the different parts of the central nervous system and their physiological functions.

  2. Students will classify different neurons and neuroglia cells.

  3. Students will recognize the physiological importance of neurons and neuroglia cells.

  4. Students will describe synaptic transmission and its structure.

  5. Students will explain the process of synaptic transmission and its significance.

Functional Classification of the Nervous System

  • Nervous System: Divided into
      - Central Nervous System (CNS)
      - Peripheral Nervous System (PNS)

  • Subdivisions of PNS:
      - Autonomic Nervous System (ANS): Involuntary control and homeostasis
        - Sympathetic Nervous System: "fight or flight" response
        - Parasympathetic Nervous System: "rest and digest"
        - Enteric Nervous System: Controls the digestive system
      - Somatic Nervous System: Receives external stimuli, voluntary muscle control

Anatomy of the Central Nervous System (CNS)

Components

  • Brain: Composed of:
      - Cerebral Cortex: Two hemispheres and several important nuclei (thalamus, hypothalamus, basal ganglia)
      - Brain Stem: Comprises midbrain, pons, and medulla oblongata
      - Cerebellum

  • Spinal Cord: 31 segments -
      - 8 Cervical
      - 12 Thoracic
      - 5 Lumbar
      - 5 Sacral
      - 1 Coccygeal

Functional Anatomy of the CNS

  • Cerebrum

  • Cerebellum

  • Brainstem

  • Spinal Cord

  • Cervical nerves (1-8)

  • Thoracic nerves (1-12)

  • Lumbar nerves (1-5)

  • Sacral nerves (1-5)

  • Conus Medullaris and Spinal Meninges: Includes Pia mater, Arachnoid mater, Dura mater

Peripheral Nervous System (PNS)

Components

  1. Cranial Nerves: 12 pairs originating mainly from the brain stem.

  2. Spinal Nerves: 31 pairs, one from each segment of the spinal cord.

  3. Autonomic Nerves: Includes sympathetic and parasympathetic fibers, controls involuntary functions throughout the body.

General Functions of the Nervous System

  1. Integration of body processes.

  2. Control of voluntary structures (skeletal muscles) and mediation of voluntary reflexes.

  3. Control of involuntary structures (smooth muscle, cardiac muscle, glands) and mediation of autonomic reflexes (heart rate, blood pressure, glandular secretion).

  4. Response to stimuli.

  5. Responsible for conscious thought, awareness, emotions, and personality.

Cells of the Nervous System

  1. Neurons: The functional cells responsible for transmitting messages.

  2. Neuroglia (Glial Cells): Supporting cells that interact functionally with neurons.

Neuron Structure

  • Cell Body (Soma): Contains nucleus and is the metabolic center.

  • Processes: Fibers extending from cell body.
      - Dendrites: Conduct impulses toward the cell body.
      - Axons: Conduct impulses away from the cell body, ending in axon terminals containing neurotransmitters.
      - Synaptic Cleft: The gap between neurons.

Nerve Fiber Coverings

  • Schwann Cells: Produce myelin sheaths around axons, with gaps called Nodes of Ranvier.

Neuron Cell Body Location

  • Most neuron cell bodies are located in the central nervous system.

  • Gray Matter: Contains cell bodies and unmyelinated fibers.

  • Nuclei: Clusters of cell bodies within white matter in CNS.

  • Ganglia: Collections of cell bodies outside CNS.

Classification of Neurons

1. Functional Classification

  • Sensory (Afferent) Neurons: Carry impulses from sensory receptors.

  • Motor (Efferent) Neurons: Carry impulses from CNS to effector organs.

  • Interneurons (Association Neurons): Found in CNS, connecting sensory and motor neurons.

2. Structural Classification

  • Multipolar Neurons: Many extensions from the cell body.

  • Bipolar Neurons: One axon and one dendrite.

  • Unipolar Neurons: A short single process leaving the cell body.

3. Classification by Diameter

  • Group A: Largest (3-20 microns), fastest conduction speed, sensitive to pressure.

  • Group B: Medium diameter (1.3-3 microns), moderate speed, sensitive to lack of O2.

  • Group C: Smallest (0.3-1.3 microns), slowest speed, unmyelinated postganglionic autonomic nerves.

Neuroglia (Glial Cells)

  • Derived mostly from ectoderm.

  • Functions:
      - Supporting function
      - Supplying nutrients to neurons
      - Maintaining electrical potential
      - Forming part of the blood-brain barrier

Glial Cells in CNS

  1. Astrocytes: Star-shaped cells, form barrier between neurons & capillaries, control chemical environment.

  2. Microglia: Phagocytic cells removing debris, toxins, microbes.

  3. Ependymal Cells: Line brain/cavity, circulate cerebrospinal fluid.

  4. Oligodendrocytes: Produce myelin sheath around nerve fibers.

Glial Cells in PNS

  1. Satellite Cells: Protect neuron cell bodies.

  2. Schwann Cells: Produce myelin sheath in PNS.

Synapses

  • Definition: Specialized junction for transmission of information between neurons, muscles, or glands.

Structure of Synapse

  • Presynaptic Ending: Contains neurotransmitters, organelles.

  • Postsynaptic Ending: Contains receptor sites for neurotransmitters.

  • Synaptic Cleft: Space between presynaptic and postsynaptic endings (approx. 20nm wide).

Function of Synapse

  1. Transmit impulses from one neuron to another.

  2. Facilitate integration of impulses.

Types of Synapses

  • Neuronal Synapses: Junctions between two nerve cells (axodendritic, axosomatic, axoaxonic).

  • Neuromuscular Synapses: Junctions between motor neurons and muscles.

  • Neuroglandular Synapses: Junctions between neurons and glands.

Synaptic Transmission

  • Definition: Process of communication between nerve cells or with muscles and glands occurring in synapses.

  • Types:
      - Electrical Transmission: Direct action potential transfer via touching membranes (rare).
      - Chemical Transmission: Conversion of electrical activity into neurotransmitter release binding to receptors on postsynaptic cells (common).

Neurotransmitters

  1. Excitatory: Initiate new impulses (e.g., acetylcholine, norepinephrine, dopamine).

  2. Inhibitory: Produce inhibitory postsynaptic potential (IPSP) reducing chance of new impulses (e.g., serotonin, GABA, glycine).

Properties of Synaptic Transmission

  • Unidirectional transmission.

  • Delayed nerve impulses.

  • Susceptible to fatigue.

  • Sensitive to anesthetics and changes in O2, CO2.

  • Summation: Strengthens subthreshold stimuli.

  • Divergence: One neuron stimulates several neurons.

  • Convergence: Several neurons stimulate one neuron.

Key Learning Points