Nervous_system_II_F2020

Central Nervous System Overview

• The Central Nervous System (CNS) is the primary control center for the body.

• It integrates sensory information, coordinates both conscious and unconscious activities, and governs basic reflexes and patterns.

Components of the CNS

Major Structures

• BRAIN: Responsible for most complex functions like thinking, feeling, and remembering.

• SPINAL CORD: Conducts two-way signals between the brain and the body.

Functions of the CNS

• Sorts out sensory information from the environment.

• Gives orders to other parts of the body for appropriate responses.

Meninges: Protective Layers

• The meninges are protective membranes covering the brain and spinal cord.

• Three Layers:

  • Dura mater: Tough outer layer.

  • Arachnoid membrane: Middle layer, has a subarachnoid space containing cerebrospinal fluid (CSF).

  • Pia mater: Delicate inner layer that clings to the brain and spinal cord.

Brain Anatomy

Division of the Brain

• The brain has specialized regions that have specific roles:

  • Brain Stem: Includes Medulla Oblongata, Pons, and Midbrain.

  • Cerebellum: Coordinates muscular activity and controls posture and balance.

  • Cerebral Hemispheres: Responsible for higher functioning tasks.

  • Diencephalon: Includes Thalamus, Hypothalamus, and Epithalamus.

Functions of Brain Regions

• Medulla Oblongata: Cranial continuation of the spinal cord, controls autonomic functions.

• Pons: Regulates breathing and relays signals to the cerebellum.

• Cerebellum: Aids in muscle coordination and balance.

• Thalamus: Acts as the relay station for sensory information.

• Hypothalamus: Regulates vital bodily functions including temperature and hormonal balance.

• Epithalamus: Contains the Pineal Gland, important for sleep cycles.

Cerebral Hemispheres Structure

• Largest brain region, involved in complex functions.

• Composed of an outer gray matter layer (cerebral cortex) and inner white matter.

• Surface area increases through folds called gyri separated by grooves known as sulci or fissures.

• Communicates between hemispheres via the corpus callosum.

Cerebrospinal Fluid (CSF) and Ventricles

• Ventricles: Four chambers (Lateral, Third, Fourth) filled with CSF.

• CSF is formed by ependymal cells and plays a critical role in cushioning and protecting the brain.

• Circulates within the ventricular system and is reabsorbed continuously.

Spinal Cord Structure and Function

• The spinal cord is encased within the vertebral column, conducting signals to and from the brain.

• Central gray matter surrounded by peripheral white matter.

• Spinal nerves formed from dorsal (sensory) and ventral (motor) roots; these are bidirectional systems.

Peripheral Nervous System (PNS)

• Connects CNS with the rest of the body, encompassing all nerves outside the brain and spinal cord.

• Comprised of spinal nerves and cranial nerves, aiding in sensation and motor functions.

Types of Reflexes

Innate (Intrinsic) Reflexes

• Quick, automatic responses to stimuli without the involvement of higher brain functions.

Learned (Acquired) Reflexes

• Develop from experience, such as driving or riding a bike.

Autonomic Nervous System (ANS)

• Involuntary control over visceral functions (heart rate, digestion).

• Composed of two divisions:

  • Sympathetic Division: Prepares the body for stress (fight or flight).

  • Parasympathetic Division: Controls resting functions (rest and digest).

Sympathetic System Effects

• Increases heart rate, dilates pupils, and inhibits processes like digestion.

Parasympathetic System Effects

• Slows heart rate, stimulates digestion, and conserves energy during rest.