Central Nervous system

Nervous System Overview

The nervous system is a complex network consisting of nerves and cells that transmit messages between the brain, spinal cord, and various parts of the body. This system is responsible for allowing humans to communicate with the outside world while also controlling internal mechanisms.

Functionality

  • Information Processing: The nervous system processes sensory information and triggers bodily reactions, such as muscle movement and sensation of pain.

Central Nervous System (CNS)

  • Components: The CNS is comprised of the brain and spinal cord, which serve as the control center of the body.

  • Coordination: It coordinates body activities via impulses transmitted through neurons.

Peripheral Nervous System (PNS)

  • Composition: The PNS encompasses all the nerves that relay messages to and from the CNS, functioning like telephone lines connecting households.

Brain Composition

  • The brain is regarded as the most intricate organ, accounting for every thought, action, memory, feeling, and sensory experience. It weighs approximately 1.4 kilograms and consists of around 100 billion neurons.

Neuronal Connectivity

  • Each neuron can connect with thousands of others through synapses, forming a dynamic network with millions of new connections established every second.

Neuroglia and Neurons

  • Neurons: These are the primary units responsible for transmitting electrical signals through the body and consist of:

    • Dendrites: Receive impulses.

    • Cell Body: Contains the nucleus.

    • Axon: Conducts impulses away from the cell body.

    • Axon Terminals: Transmit impulses to other neurons.

  • Neuroglia: These cells support and nourish neurons. Four types in the CNS include:

    • Astrocytes: Maintain the blood-brain barrier and chemical environment.

    • Oligodendrocytes: Myelinate axons, providing structural support.

    • Ependymal Cells: Line brain ventricles and produce cerebrospinal fluid (CSF).

    • Microglia: Cleanup cell debris and pathogens.

Synapse Structure

A synapse is the junction connecting two neurons, with a significant gap known as the synaptic cleft. Each neuron plays a specific role:

  • Presynaptic Neuron: Contains neurotransmitter-filled vesicles.

  • Postsynaptic Neuron: Contains receptors for receiving signals.

  • Synaptic Cleft: The gap between neurons.

Myelination

  • Myelinated Nerve Fibres: Possess a myelin sheath allowing faster impulse transmission through saltatory conduction.

  • Non-myelinated Nerve Fibres: Lack a myelin sheath and transmit impulses slower through continuous conduction.

Types of Neurons

  1. Multipolar Neurons: Predominantly found in the CNS and contain multiple processes.

  2. Bipolar Neurons: Have two processes; found in sensory organs.

  3. Unipolar Neurons: Have one process; primarily serve in sensory functions.

Brain Coverings: The Meninges

The meninges are protective membranes that encompass the brain and spinal cord:

  • Dura Mater: Outermost, thick layer adjacent to skull bones.

  • Arachnoid Mater: Middle layer containing the sub-arachnoid space filled with cerebrospinal fluid.

  • Pia Mater: Innermost layer tightly adhered to the surfaces of the brain and spinal cord.

Cerebrospinal Fluid (CSF)

CSF is a clear fluid surrounding the brain and spinal cord, cushioning against injuries, removing waste, and maintaining proper functioning of the CNS. It is produced by the choroid plexus, with an adult's secretion varying from 400 to 600 ml daily. Hydrocephalus occurs due to abnormal CSF accumulation.

Blood-Brain Barrier (BBB)

The BBB is a selective barrier formed by endothelial cells to protect the brain from toxins while allowing necessary nutrients to pass through.

Brain Structure and Functionality

  • The brain features distinct folds (gyri) and grooves (sulci), providing increased surface area for neuron processing.

  • Divisions, lobes, and functional specialization occur based on these structures.

Sections of the Brain

  1. Cerebrum: Largest section controlling memory, intelligence, and voluntary muscle movements.

  2. Cerebellum: Coordinates voluntary movements, including balance and posture.

  3. Brainstem: Connects the brain to the spinal cord and regulates involuntary actions.

Vascular Supply

The Circle of Willis, an arterial circle located at the base of the brain, ensures a continuous blood supply from the vertebral and internal carotid arteries.

Diagnostic Techniques: EEG

Electroencephalography (EEG) measures brain waves via electrodes placed on the scalp, identifying four primary wave types:

  1. Alpha

  2. Beta

  3. Theta

  4. Delta

Genetic Disorders

  • Klinefelter Syndrome: Affects males with an extra X chromosome, leading to varied symptoms such as infertility and learning difficulties.

  • Turner Syndrome: Affects females missing a complete X chromosome, associated with short stature and heart defects.

Quiz Overview

A series of quiz questions and answers relate to the nervous system, brain parts, structural units, and functions, reinforced through assessments to solidify understanding.