Nervous System Overview

Nervous System Organization

• Nervous system divided into two parts: Central Nervous System (CNS) and Peripheral Nervous System (PNS)
• CNS includes the brain, spinal cord, optic nerve, and retina
• PNS includes everything else, like the sympathetic and parasympathetic nervous systems

Brain and Nerve Cells

• Brain contains neurons and glial cells
• Neurons are the functional units of the nervous system, requiring glucose for function
• Glial cells provide structural and nutritional support to neurons

Neuron Structure

• Neurons consist of dendrites, a cell body (soma), an axon, and axon terminals
• Dendrites receive signals from other neurons
• The cell body integrates these signals
• The axon transmits signals to other neurons
• Axon terminals release neurotransmitters to communicate with other neurons

Neuron Communication

• Axon terminals contain synaptic vesicles filled with neurotransmitters
• Action potentials travel down the axon, causing vesicles to release neurotransmitters into the synaptic cleft
• Neurotransmitters bind to receptors on the dendrites of other neurons
• Electrical signals become chemical signals

Neural Impulse (Action Potential)

• Neurons maintain a negative internal charge compared to the positive external charge
• A stimulus opens sodium channels, allowing sodium ions to flow into the neuron, creating a positive internal charge (depolarization)
• Potassium ions then flow out of the neuron, restoring the negative internal charge (repolarization)
• This rapid change in charge is the action potential
• The neuron must repolarize before another action potential can occur

Neurotransmitters

• Neurotransmitters are chemical messengers that transmit signals across synapses
• Acetylcholine (ACh): Associated with muscle movement, attention, arousal, memory.
• Monoamines (Dopamine, Norepinephrine, Serotonin): Involved in movement control, arousal, mood, sleep, hunger, and sexual behavior
• Amino acids (GABA, Glutamate): GABA is inhibitory, reducing neuron firing; glutamate is excitatory, increasing neuron firing
• Anandamide: Unconventional neurotransmitter, playing a role in eating, memory, motivation, and sleep (related to cannabis effects)
• Neuropeptides (endorphins): Act as hormones and neurotransmitters, involved in pain relief

Nervous System Communication

• Nervous system is a fast communication system.
• Endocrine system is a slower communication system, using hormones released into the blood.

Neural Plasticity

• Neural system's ability to adapt and change throughout life
• Includes growth of dendrites and axons, synapse formation, pruning of synapses, and myelination
• Can occur in response to learning, injury, etc

Early Development

• Neural development includes growth, synaptogenesis (formation of synapses), pruning, and myelination
• Pruning is important for efficient neural connections

Neural Plasticity & Injury

• The brain can compensate for injury by taking over functions from damaged areas
• Factors like neurogenesis (creation of new neurons) can play a role in recovery after injury

Meninges

• Protective membranes that cover the brain and spinal cord (dura mater, arachnoid mater, pia mater)

Cerebral Ventricles

• Contain cerebrospinal fluid that cushions and protects the brain

Cerebral Cortex

• Outer layer of the brain, responsible for higher-level functions (processing information, language, etc)
• Divided into lobes (frontal, parietal, temporal, occipital)

Subcortical Structures

• Structures beneath the cerebral cortex, including the basal ganglia (involved in voluntary movement)
• Limbic system (including thalamus, hypothalamus, hippocampus, amygdala) plays a role in emotions, learning, motivation, and memory.