Honors Anatomy and Physiology Unit 8 Review: Nervous System

Key Structures and Functions

• The nervous system consists of the brain, spinal cord, and a complex network of nerves that transmit signals throughout the body
• Neurons are the primary functional units of the nervous system and are responsible for receiving, processing, and transmitting information
• Glial cells provide support, protection, and maintenance for neurons, ensuring optimal functioning of the nervous system
• The brain is divided into several regions, each with specific functions (cerebrum, cerebellum, brainstem)
• The spinal cord serves as a conduit for information between the brain and the rest of the body and is involved in reflexes and motor control
• Nerves are bundles of axons that carry signals between the central nervous system and the periphery, enabling communication and coordination
• The blood-brain barrier is a selective barrier that protects the brain from harmful substances while allowing essential nutrients to pass through

Neurons and Synapses

• Neurons are specialized cells that transmit electrical and chemical signals, enabling communication within the nervous system
• The structure of a neuron includes the cell body (soma), dendrites, and axon
  • Dendrites receive signals from other neurons
  • The axon conducts electrical impulses away from the cell body
• Synapses are the junctions between neurons where information is transmitted through the release of neurotransmitters
• Neurotransmitters are chemical messengers that bind to receptors on the postsynaptic neuron, triggering changes in the cell's electrical potential
• Synaptic plasticity refers to the ability of synapses to strengthen or weaken over time, which is crucial for learning, memory, and adaptation
• Action potentials are the electrical signals that propagate along the axon, enabling the transmission of information from one neuron to another
• Myelination of axons by glial cells (oligodendrocytes and Schwann cells) increases the speed and efficiency of signal transmission

Central Nervous System

• The central nervous system (CNS) consists of the brain and spinal cord and is responsible for processing, integrating, and coordinating information
• The cerebrum is the largest part of the brain and is involved in higher cognitive functions (perception, memory, decision-making, language)
  • The cerebral cortex is the outer layer of the cerebrum and is divided into four lobes (frontal, parietal, temporal, occipital)
• The cerebellum is responsible for motor coordination, balance, and fine-tuning of movements
• The brainstem connects the brain to the spinal cord and regulates vital functions (breathing, heart rate, sleep, arousal)
• The spinal cord is a long, thin bundle of nervous tissue that extends from the brainstem and is involved in reflexes, sensory processing, and motor control
• The ventricular system consists of interconnected cavities (ventricles) within the brain that produce, circulate, and absorb cerebrospinal fluid (CSF)
• CSF provides mechanical and immunological protection to the brain and spinal cord, as well as maintaining homeostasis in the CNS

Peripheral Nervous System

• The peripheral nervous system (PNS) consists of nerves and ganglia outside the brain and spinal cord, connecting the CNS to the rest of the body
• The PNS is divided into the somatic nervous system, which controls voluntary movements and processes sensory information, and the autonomic nervous system, which regulates involuntary functions
• Sensory (afferent) nerves carry information from sensory receptors to the CNS for processing and interpretation
• Motor (efferent) nerves carry signals from the CNS to muscles and glands, enabling movement and secretion
• The autonomic nervous system is further divided into the sympathetic and parasympathetic divisions, which work together to maintain homeostasis
  • The sympathetic division is associated with the "fight or flight" response and prepares the body for action
  • The parasympathetic division is associated with the "rest and digest" response and promotes relaxation and energy conservation
• Ganglia are clusters of neuronal cell bodies located outside the CNS that serve as relay stations for sensory and motor information

Sensory and Motor Pathways

• Sensory pathways carry information from sensory receptors to the CNS for processing and interpretation
• Sensory receptors are specialized structures that detect specific stimuli (touch, temperature, pain, light, sound, chemicals)
• The somatosensory system processes information related to touch, pressure, temperature, and pain from the skin and internal organs
• The visual system processes light stimuli detected by photoreceptors in the retina and transmits this information to the visual cortex for interpretation
• The auditory system detects sound waves and processes them in the cochlea before sending signals to the auditory cortex for interpretation
• Motor pathways carry signals from the CNS to muscles and glands, enabling movement and secretion
• The pyramidal (corticospinal) tract is a major motor pathway that originates in the cerebral cortex and controls voluntary movements
• The extrapyramidal system includes motor pathways that originate in the brainstem and basal ganglia and is involved in the control of posture, balance, and involuntary movements
• Reflexes are rapid, automatic responses to specific stimuli that involve sensory and motor pathways, often bypassing the brain for faster processing

Neurotransmitters and Signaling

• Neurotransmitters are chemical messengers that transmit signals between neurons at synapses
• The main classes of neurotransmitters include amino acids (glutamate, GABA), monoamines (dopamine, serotonin, norepinephrine), and peptides (endorphins, oxytocin)
• Neurotransmitters are synthesized in the presynaptic neuron and stored in synaptic vesicles
• Upon the arrival of an action potential, neurotransmitters are released into the synaptic cleft and bind to receptors on the postsynaptic neuron
• Receptors can be ionotropic, directly opening ion channels, or metabotropic, activating intracellular signaling cascades
• The effects of neurotransmitters can be excitatory, increasing the likelihood of an action potential in the postsynaptic neuron, or inhibitory, decreasing the likelihood of an action potential
• Neurotransmitters are cleared from the synaptic cleft by reuptake into the presynaptic neuron or degradation by enzymes
• Neuromodulators are substances that modify the effects of neurotransmitters, altering the excitability and responsiveness of neurons

Disorders and Diseases

• Neurodegenerative diseases, such as Alzheimer's and Parkinson's, involve the progressive loss of neurons and impairment of cognitive and motor functions
• Alzheimer's disease is characterized by the accumulation of amyloid plaques and neurofibrillary tangles, leading to memory loss and cognitive decline
• Parkinson's disease is caused by the degeneration of dopaminergic neurons in the substantia nigra, resulting in tremors, rigidity, and impaired movement
• Multiple sclerosis is an autoimmune disorder that attacks the myelin sheath of neurons, disrupting signal transmission and causing a range of neurological symptoms
• Stroke occurs when blood flow to the brain is disrupted, leading to cell death and neurological deficits (paralysis, speech difficulties, sensory loss)
• Epilepsy is a neurological disorder characterized by recurrent seizures, which are abnormal, excessive, or synchronous neuronal activity in the brain
• Psychiatric disorders, such as depression, anxiety, and schizophrenia, involve imbalances in neurotransmitter systems and alterations in brain structure and function
• Traumatic brain injury (TBI) results from external forces causing damage to the brain, leading to a range of cognitive, emotional, and physical impairments

Clinical Applications and Research

• Neuroimaging techniques, such as MRI, fMRI, and PET, allow for non-invasive visualization of brain structure and function, aiding in diagnosis and research
• Electroencephalography (EEG) measures the electrical activity of the brain using electrodes placed on the scalp, providing insights into brain function and disorders
• Deep brain stimulation (DBS) involves the implantation of electrodes in specific brain regions to modulate neural activity, offering potential treatments for movement disorders and psychiatric conditions
• Optogenetics is a technique that uses light to control the activity of genetically modified neurons, enabling precise manipulation of neural circuits in animal models
• Stem cell therapy holds promise for the regeneration of damaged or lost neurons, with potential applications in neurodegenerative diseases and spinal cord injuries
• Gene therapy involves the introduction of functional genes into cells to replace defective ones or to provide new functions, offering potential treatments for genetic neurological disorders
• Psychopharmacology is the study of drugs that affect the nervous system, including the development and use of medications to treat psychiatric and neurological disorders
• Computational neuroscience combines mathematical modeling and computer simulations to understand the complex functions of the nervous system and to develop new therapeutic approaches