Central Nervous System: Brain and Spinal Cord

• The brain and spinal cord constitute the central nervous system (CNS).
• The CNS integrates sensory information and coordinates bodily functions.
• The brain is the control center for thought, memory, emotion, and language.
• The spinal cord serves as a communication pathway between the brain and the peripheral nervous system.

Brain

• The brain is divided into the cerebrum, diencephalon, brainstem, and cerebellum.
• The cerebrum is the largest part of the brain divided into two hemispheres.
• The cerebral cortex is the outer layer of the cerebrum and is responsible for higher-level cognitive functions.
• The cerebral cortex is highly folded, increasing its surface area.
• Each hemisphere is divided into four lobes: frontal, parietal, temporal, and occipital.
• The frontal lobe is involved in motor control, planning, and decision-making.
• The parietal lobe processes sensory information such as touch, temperature, and pain.
• The temporal lobe is involved in auditory processing, memory, and language.
• The occipital lobe is responsible for visual processing.
• The diencephalon is located beneath the cerebrum and includes the thalamus and hypothalamus.
• The thalamus relays sensory and motor information to the cerebral cortex.
• The hypothalamus regulates body temperature, hunger, thirst, and the sleep-wake cycle.
• The brainstem connects the cerebrum and diencephalon to the spinal cord.
• The brainstem consists of the midbrain, pons, and medulla oblongata.
• The midbrain is involved in motor control, vision, and hearing.
• The pons relays information between the cerebrum and cerebellum.
• The medulla oblongata controls vital functions such as heart rate, breathing, and blood pressure.
• The cerebellum is located behind the brainstem and is responsible for motor coordination and balance.

Spinal Cord

• A long, cylindrical structure that extends from the brainstem to the lumbar region of the vertebral column.
• The spinal cord transmits sensory information from the body to the brain.
• The spinal cord transmits motor commands from the brain to the body.
• The spinal cord is protected by the vertebral column.
• The spinal cord is surrounded by three layers of protective tissue called the meninges.
• The meninges consist of the dura mater, arachnoid mater, and pia mater.
• The spinal cord is divided into segments, each of which gives rise to a pair of spinal nerves.
• Spinal nerves carry sensory and motor information to and from the spinal cord.
• The spinal cord contains both gray matter and white matter.
• Gray matter is located in the center of the spinal cord and contains neuronal cell bodies.
• White matter surrounds the gray matter and contains myelinated axons, which transmit signals rapidly.
• The dorsal horns of the gray matter receive sensory information.
• The ventral horns of the gray matter contain motor neurons.
• Ascending tracts in the white matter carry sensory information to the brain.
• Descending tracts in the white matter carry motor commands from the brain.

Protection of the CNS

• The brain and spinal cord are protected by bone, membranes, and fluid.
• The skull protects the brain.
• The vertebral column protects the spinal cord.
• The meninges surround both the brain and spinal cord.
• The meninges consist of the dura mater, arachnoid mater, and pia mater.
• The dura mater is the outermost layer, made of tough connective tissue.
• The arachnoid mater is the middle layer, separated from the dura mater by the subdural space.
• The pia mater is the innermost layer, tightly adhered to the surface of the brain and spinal cord.
• Cerebrospinal fluid (CSF) fills the spaces between the meninges and within the ventricles of the brain.
• CSF cushions the brain and spinal cord, protecting them from injury.
• CSF also helps to remove waste products from the CNS.
• The blood-brain barrier (BBB) protects the brain from harmful substances in the blood.
• The BBB is formed by specialized cells in the walls of brain capillaries.
• The BBB restricts the passage of large molecules and toxins into the brain.

Neural Development

• The development of the brain and spinal cord begins early in embryonic development.
• The neural tube forms from the ectoderm during the third week of gestation.
• The anterior part of the neural tube develops into the brain.
• The posterior part of the neural tube develops into the spinal cord.
• The neural crest cells migrate away from the neural tube and give rise to various cell types.
• These cell types include sensory neurons, autonomic neurons, and glial cells.
• Brain development involves cell proliferation, migration, differentiation, and programmed cell death.
• Synaptogenesis, the formation of synapses, occurs throughout development and into adulthood.
• Myelination, the formation of myelin sheaths around axons, continues into adolescence.
• Environmental factors can influence brain development.

Neural Communication

• Neurons communicate with each other through electrical and chemical signals.
• Action potentials are electrical signals that travel along the axon of a neuron.
• Neurotransmitters are chemical signals that transmit information between neurons.
• Synapses are the junctions between neurons where neurotransmitters are released.
• Neurotransmitters bind to receptors on the postsynaptic neuron, causing a change in its membrane potential.
• Excitatory neurotransmitters increase the likelihood of an action potential in the postsynaptic neuron.
• Inhibitory neurotransmitters decrease the likelihood of an action potential in the postsynaptic neuron.
• The brain contains many different types of neurotransmitters.
• These neurotransmitters include acetylcholine, dopamine, serotonin, and glutamate.
• Neural circuits are networks of interconnected neurons that process information.
• Plasticity refers to the brain's ability to change and adapt over time.
• Learning and memory involve changes in synaptic connections.

Common Neurological Disorders

• Stroke occurs when blood supply to the brain is interrupted
• Alzheimer's disease is a progressive neurodegenerative disease that causes memory loss and cognitive decline
• Parkinson's disease is a neurodegenerative disease that affects motor control
• Multiple sclerosis is an autoimmune disease that affects the myelin sheaths of nerve fibers
• Epilepsy is a neurological disorder characterized by recurrent seizures
• Spinal cord injury can result in paralysis and loss of sensation
• Meningitis is an inflammation of the meninges
• Encephalitis is an inflammation of the brain
• Brain tumors are abnormal growths in the brain