Nervous System Overview

Nervous System Overview

• The nervous system connects all body parts and transmits signals between them.
• It's a system of cells, tissues, and organs that regulates responses to internal and external stimuli.

Main Divisions of the Nervous System

• Central Nervous System (CNS):

  • The main processing center of the entire nervous system.
  • The command center for the entire body.
  • Processes information and sends instructions to other body parts.

• Peripheral Nervous System (PNS):

  • Connects the CNS to organs and limbs.
  • Made up of bundled, rope-like structures called nerves.
  • Gathers and delivers information to and from the CNS.

Central Nervous System (CNS) - Brain

• Brain:

  • Organ located within the skull.
  • Acts as an organizer and distributor of information for the body.
  • It averages around 1.4kg.
  • Appears gray due to the presence of cell bodies of approximately 100 billion neurons.
  • White matter is underneath the gray matter, made up of bundles of axons.

• Meninges:

  • Three protective layers surrounding the brain:
    • Pia mater (delicate inner layer)
    • Arachnoid (web-like middle layer with cushioning fluid)
    • Dura mater (tough outer layer)

• Cerebrospinal Fluid (CSF):

  • Clear, colorless fluid that bathes the brain and spinal cord.
  • Protects and cushions the brain and spinal cord.

Parts of the Brain

• Cerebrum:

  • The largest and most noticeable part of the brain (about 85%).
  • Lined with deep, wrinkled grooves that increase the surface area for learning, intelligence, and judgment.
  • Controls voluntary body activities and shapes personality.
  • Divided into two halves (left and right), the right controls the left side of the body and the left controls the right side of the body.

• Cerebellum:

  • Located behind the brain stem.
  • Coordinates muscle actions, maintaining balance, and allowing smooth, steady, and efficient movement.
  • Crucial for posture, equilibrium, and coordination.

• Brain Stem:

  • Connects the spinal cord to the rest of the brain.
  • Coordinates vital survival functions like breathing, heart rate, sleep, and wakefulness; location of the thalamus and hypothalamus.
  • Made up of three regions:
    • Medulla oblongata (controls involuntary actions like heartbeat, breathing, and blood pressure)
    • Midbrain (processes visual and auditory reflexes)
    • Pons (helps control respiratory functions)

Central Nervous System (CNS) - Spinal Cord

• Spinal Cord: A long bundle of nerves and cells that extends from the brain's lower portion to the lower back. It is the pathway for nerve impulses to and from the brain. Spinal column protects it.

Peripheral Nervous System (PNS) - Divisions

• Somatic Nervous System:

  • Associated with voluntary control of body movements.
  • Includes spinal nerves and cranial nerves.

• Autonomic Nervous System:

  • Regulates involuntary body functions.
  • Divided into the Sympathetic (activated in stressful situations) and Parasympathetic (restoring the body to normal relaxed mode) systems

• Spinal Nerves: Carry sensory and motor signals between the spinal cord and the body.

• Cranial Nerves: Carry information into and out of the brain stem.

Additional Brain Facts

• Multitasking is impossible; brains need to focus on tasks individually.
• An adult brain weighs about 3 pounds.
• The human brain is approximately 75% water.
• The human brain triples in size during the first year of life.
• Headaches result from chemical reactions.
• The brain has approximately 100 billion neurons.
• The belief that humans only use 10% of their brain is a myth.
• Cholesterol is crucial for learning and memory.
• Dreams involve imagination, physiological factors, and neurological factors.
• Short-term memory lasts about 20-30 seconds.
• Brain freeze is a warning signal..
• The brain can't feel pain.
• The brain shrinks as we age.
• Alcohol affects the brain in various ways, including vision, speech, and coordination.
• Brains generate random thoughts.
• Brain activity can power small light bulbs.
• Reading out loud uses different brain pathways than silent reading.
• The brain is mainly made up of fat.
• Sleep is essential for the brain's proper function.