Nervous System: Neurons and Glial Cells

• The nervous system comprises neurons and glial cells, exploring its divisions and understanding brain structures, functions, genetics, and their impact on neuroscience.

Cells of the Nervous System

• Neurons are the fundamental units of the nervous system, with approximately 90-100 billion in the human brain.
• Neurons generate action potentials and release neurotransmitters for communication and process motor, sensory, and cognitive information.

Structure of a Neuron

• Dendrites receive signals from other neurons.
• The soma (cell body) contains the nucleus and cellular components.
• The axon transmits signals away from the soma.
• Axon terminals release neurotransmitters into the synapse.

Functional Types of Neurons

• Sensory Neurons (Afferent) carry sensory information to the CNS.
• Interneurons connect neurons within the same neural region.
• Motor Neurons (Efferent) carry signals away from the CNS to muscles/glands.

Glial Cells

• Oligodendrocytes form myelin in the CNS.
• Astrocytes form the blood-brain barrier, respond to neuronal injury (gliosis), and provide nutrients for neurotransmitter synthesis and maintain ion balance
• Microglia act as immune cells, removing waste.
• Ependymal cells produce cerebrospinal fluid (CSF).

The Nervous System: Terminology & Divisions

• The neuraxis is the central axis of the nervous system.

Directional Terms

• Anterior - Posterior (Front - Back)
• Dorsal - Ventral (Top - Bottom)
• Medial - Lateral (Middle - Side)
• Superior - Inferior (Above - Below)

Peripheral Nervous System (PNS)

• The Somatic Nervous System controls voluntary muscle movements.
• The Autonomic Nervous System (ANS) controls involuntary functions.
• The Sympathetic Nervous System is responsible for "fight or flight" responses, releasing norepinephrine.
• The Parasympathetic Nervous System enables "rest and digest" functions by releasing acetylcholine.
• The Enteric Nervous System regulates digestion.

Central Nervous System (CNS)

• The Hindbrain includes the medulla, pons, and cerebellum.
• The Medulla regulates breathing, heart rate, and reflexes.
• The Pons connects brain regions and affects arousal/sleep.
• The Cerebellum controls balance, coordination, and motor timing.
• The Midbrain includes the superior and inferior colliculus, substantia nigra, ventral tegmental area (VTA), and periaqueductal gray (PAG).
• The Superior Colliculus controls visual tracking.
• The Inferior Colliculus processes auditory information.
• The Substantia Nigra produces dopamine and regulates movement (affected in Parkinson's disease).
• The Ventral Tegmental Area (VTA) is important for reward processing.
• The Periaqueductal Gray (PAG) regulates pain and is rich in endorphins.
• The Forebrain includes the thalamus, hypothalamus, limbic system, cerebral cortex, nucleus accumbens, and basal ganglia.
• The Thalamus serves as a sensory relay station.
• The Hypothalamus regulates hormones, hunger, temperature, etc.
• The Limbic System controls emotion and memory.
• The Cingulate Gyrus processes pain and emotions.
• The Hippocampus is involved in memory formation.
• The Amygdala is responsible for fear and aggression.
• The Olfactory Bulb processes smells.
• The Nucleus Accumbens is part of the reward system.
• The Cerebral Cortex enables higher cognitive functions.
• The Occipital Lobe controls vision.
• The Temporal Lobe handles hearing and language.
• The Parietal Lobe involves sensory processing.
• The Frontal Lobe relates to decision-making, personality, and movement.
• The Basal Ganglia stabilizes voluntary movement and regulates habitual movement.

Cerebral Blood Flow & Cerebrospinal Fluid (CSF)

• Cerebral blood flow is essential for normal brain function.
• The Blood-Brain Barrier (BBB) controls substances entering the brain from the bloodstream.
• Cerebrospinal Fluid (CSF) is produced in the ventricles, provides cushioning and nutrient transport, and its analysis helps in drug and neurotransmitter studies.

Genetics & the Nervous System

• The nucleus contains 46 chromosomes, made of DNA.
• Genes are segments of DNA that determine traits.
• Polymorphisms are gene variations that influence traits like enzyme production and neurotransmitter levels.
• Gene expression can be modified without changing the DNA sequence.
• Methylation: Tightly wound DNA (gene off).
• Acetylation: Loosely wound DNA (gene on).
• Transgenic Animals are modified to study gene function, either globally (whole-body gene change) or conditionally (specific area/time change).

CRISPR-Cas9 Gene Editing

• CRISPR-Cas9 is a technique to edit genes or turn them on/off.
• It could be used for treating genetic disorders.

Explore the nervous system's fundamental components: neurons and glial cells. Understand neuron structure, including dendrites, soma, and axon terminals. Learn about sensory, inter, and motor neuron functions within the nervous system.