Brain and Spinal Cord

• The brain and spinal cord are the central nervous system (CNS) components.

Brain

• The brain is the nervous system's control center.
• It weighs about 1.5 kg.
• Billions of neurons and glial cells make it up.
• The cerebrum, diencephalon, brainstem, and cerebellum are its four main regions.

Cerebrum

• The cerebrum, the largest brain part, divides into left and right hemispheres.
• The longitudinal fissure separates the hemispheres.
• The corpus callosum, a large nerve fiber bundle, connects them.
• Gray matter makes up the cerebral cortex, the cerebrum's outer layer.
• Higher-level functions like language, memory, and reasoning are the responsibility of the cerebral cortex.
• Frontal, parietal, temporal, and occipital lobes divide each hemisphere.
• Motor control, planning, and decision-making involve the frontal lobe.
• The parietal lobe processes sensory data like touch, temperature, and pain.
• Auditory processing, memory, and language comprehension are the responsibility of the temporal lobe.
• The occipital lobe handles visual processing.

Diencephalon

• The diencephalon sits beneath the cerebrum.
• The thalamus, hypothalamus, and epithalamus comprise it.
• The thalamus transmits sensory and motor data to the cerebral cortex.
• The hypothalamus controls body temperature, hunger, thirst, and sleep-wake cycles.
• The epithalamus has the pineal gland, which produces melatonin.

Brainstem

• The brainstem joins the cerebrum and diencephalon to the spinal cord.
• It consists of the midbrain, pons, and medulla oblongata.
• The midbrain regulates motor function, vision, and hearing.
• The pons transmits data between the cerebrum and cerebellum and regulates sleep and breathing.
• The medulla oblongata regulates critical bodily processes, including heart rate, blood pressure, and breathing.

Cerebellum

• The cerebellum is posterior to the cerebrum, at the back of the brain.
• Coordinating movement, balance, and posture comes under its responsibility.
• It gathers sensory input from both the spinal cord and other brain regions.
• It uses this data to improve motor abilities.

Spinal Cord

• The spinal cord is a long, cylindrical structure that runs from the brainstem to the lower back.
• It is about 45 cm long and 1-1.5 cm wide.
• The vertebral column protects it.
• The spinal cord sends sensory and motor information between the brain and the body.
• It also manages reflexes.
• The spinal cord comprises gray plus white matter.
• The gray matter, located in the spinal cord's center, contains neuronal cell bodies.
• The white matter that surrounds the gray matter is composed of myelinated axons.
• The spinal cord divides into segments, each producing a pair of spinal nerves.
• There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

Brain and Spinal Cord Protection

• Several structures protect the brain and spinal cord.
• The skull, meninges, and cerebrospinal fluid are among them.
• The skull protects the brain as a bony structure encompassing it.
• The vertebral column protects the spinal cord.
• The meninges comprise three layers of protective tissue around the brain and spinal cord.
• The dura mater, arachnoid mater, and pia mater comprise the three layers of meninges.
• The dura mater is the outermost layer, a tough, fibrous membrane.
• The subdural space separates the arachnoid mater, the middle layer, from the dura mater.
• The pia mater is the innermost layer, directly connected to the brain and spinal cord surfaces.
• Cerebrospinal fluid (CSF) is a clear, colorless fluid surrounding the brain and spinal cord.
• CSF cushions the brain and spinal cord, protecting them from injury.
• It also eliminates waste from the brain and spinal cord.
• The blood-brain barrier (BBB) is a protective barrier that restricts the passage of substances from the bloodstream into the brain.
• Tight junctions between the cells lining brain capillaries form the BBB.
• It shields the brain against dangerous substances, including toxins and pathogens.

Brain Development

• Early embryonic development marks the start of brain development, which lasts throughout childhood and adolescence.
• Early in development, the neural tube develops, giving rise to the brain and spinal cord.
• Different brain regions develop at varying rates.
• The cerebral cortex develops last in the brain.
• Genetics plus environmental variables affect brain development.
• The brain exhibits considerable plasticity during development, allowing it to adapt and change according to experience.

Brain Functions

• The brain regulates various processes, including:
  • Sensory perception
  • Motor control
  • Cognition
  • Emotion
  • Memory
  • Language
  • Consciousness
• Different brain regions specialize in different functions.
• However, many functions involve the coordinated activity of multiple brain regions.

Sensory perception

• Detecting and interpreting sensory input from the environment is sensory perception.
• Sensory neurons send sensory data to the brain.
• The brain interprets this data, creating a perception.

Motor control

• Motor control includes the planning, start, and execution of movements.
• Motor neurons send motor commands from the brain to the muscles.
• The cerebellum is essential for balance and movement coordination.

Cognition

• Thinking, reasoning, and problem-solving all fall under the category of cognition.
• The cerebral cortex regulates higher-level cognitive functions.
• The frontal lobe is crucial for executive functions, including planning, decision-making, and working memory.

Emotion

• Emotion comprises subjective feelings plus accompanying physiological responses.
• The limbic system comprises brain regions involved in emotion.
• The amygdala regulates emotions like anger and fear.
• The hippocampus contributes to memory formation and retrieval.

Memory

• Memory refers to the capacity to store plus retrieve data.
• Sensory, short-term, and long-term memory are different memory types.
• Creating new long-term memories requires the hippocampus.
• The cerebral cortex contributes to storing long-term memories.

Language

• Language is a complex communication system using symbols plus rules.
• Language functions typically localize to the brain's left hemisphere.
• Broca's area contributes to speech production.
• Wernicke's area contributes to language comprehension.

Consciousness

• Consciousness refers to being aware of oneself and one's surroundings.
• The neural basis of consciousness remains not fully understood.
• However, it likely involves the coordinated activity of several brain regions.

Spinal Cord Functions

• Relaying information to and from the brain
• Processing reflexes