Nervous System Structure and Function

Nervous System Structure and Function

• The nervous system is organized into a central nervous system (CNS) and peripheral nervous system (PNS).
• The CNS consists of the brain and spinal cord, where information processing occurs.
• The PNS transmits information to and from the CNS, controlling movement and internal environment. It is composed of nerves and ganglia.
• The PNS has two major divisions: the somatic nervous system (motor system) controlling skeletal muscles, and the autonomic nervous system controlling smooth and cardiac muscles. The autonomic system further branches into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
• The enteric nervous system (ENS) is a branch of the PNS that controls the digestive tract, pancreas, and gallbladder independently.
• Vertebrate nervous system hierarchies show a clear structure, integrating information for complex tasks.
• Neurons (nerve cells) communicate across synapses, strengthening connections when active together, and weakening others.
• The brain regions have specialized functions, such as the frontal, parietal, temporal, and occipital lobes with specific sensory and cognitive functions. Examples include comprehending spoken words, object recognition, or forming speech.
• The spinal cord generates basic locomotion patterns and reflexes, independent of the brain. A reflex is an automatic response to a stimulus. An example is the knee-jerk reflex.
• The CNS develops with distinct embryonic regions, that fully develop into more complex structures in the adult brain.

Nervous System Disorders

• Disorders affecting the nervous system include: schizophrenia, depression, Alzheimer's disease, Parkinson's disease, and drug addiction.
• Schizophrenia is characterized by psychotic episodes and distorted reality perception, often with a strong genetic component. It involves disruptions in dopamine neurotransmitter pathways.
• Depression is characterized by depressed mood and abnormalities in sleep and appetite and is linked with a disruption of monoamine (serotonin) neurotransmitter pathways. Fluoxetine (Prozac) is a drug that increases biogenic amine activity in the brain.
• Alzheimer's disease, a form of dementia, is associated with age, amyloid plaque and neurofibrillary tangle formation, and massive brain shrinkage, reflecting neuronal death.
• Parkinson's disease, a motor disorder, is marked by muscle tremors, poor balance, and shuffling gait due to dopamine deficiency in the midbrain. L-dopa, a dopamine-related drug, can reduce disease symptoms.
• Drug addiction affects the reward system in the brain. Addictive drugs like nicotine, opioids, and cocaine, stimulate dopamine release and/or inhibit dopamine removal, which becomes linked to reward circuits and compulsive drug use.