The Nervous System Overview

The Nervous System

• The nervous system is responsible for sensing, processing, and responding to information from the environment
• Peripheral nervous system (PNS) connects the outer portions of the body with the CNS
  • Somatic division controls voluntary movements (e.g., walking, talking)
  • Autonomic division controls involuntary functions (e.g., breathing, heart rate)
    • Sympathetic nervous system activates the "fight-or-flight" response
    • Parasympathetic nervous system calms the body after a stressful event
• Central nervous system (CNS) consists of the brain and spinal cord
  • Brain processes information and controls behavior
    • Hemispheres are connected by the corpus callosum
    • Hindbrain controls basic life functions, such as breathing and heart rate
    • Midbrain involved in movement and attention
    • Forebrain involved in higher-level cognitive functions, such as language and thought
  • Spinal cord serves as an information superhighway
    • Interneurons connect neurons to each other
    • Reflexes are automatic behaviors that bypass the brain for faster responses

The Neuron

• Dendrites receive messages from other neurons
• Soma (cell body) keeps the neuron alive and functioning
  • Contains the nucleus
• Axon carries messages out to other cells
  • Messages travel in one direction
• Resting potential is the electrical charge of a neuron at rest
  • Inside of the neuron is negatively charged relative to the outside
• Action potential is the electrical signal that travels down the axon
  • Neuron quickly reverses its electrical charge
• Absolute refractory period is when the neuron cannot fire
• Relative refractory period is when the neuron is more resistant to firing
• Neurotransmitters are chemicals that transmit signals across the synapse, having excitatory or inhibitory effects
  • Excitatory increases the likelihood of the receiving neuron firing
  • Inhibitory decreases the likelihood of the receiving neuron firing

Sending the Message

• Synaptic vesicles store neurotransmitters
• Neurotransmitters are released into the synapse, where they bind to receptor sites on the next neuron
• Synaptic gap is the fluid-filled space between neurons
• Receptor sites are proteins that bind to specific neurotransmitters
• Diffusion is when neurotransmitters drift away from the synapse
• Reuptake is when neurotransmitters are reabsorbed by the sending neuron
• Enzymatic degradation is when enzymes break down neurotransmitters

How Neurons Fire

• All or none principle: Neurons fire completely or not at all
• Threshold for firing is the minimum amount of stimulation needed to trigger an action potential
• Firing rate is the frequency of action potentials
• Refractory period limits how quickly a neuron can fire again

Neurotransmitters and their Functions

• Acetylcholine (ACh) - involved in muscle movement, learning, and memory
  • Excitatory or inhibitory
• Dopamine - involved in movement, attention, learning, and pleasure
  • Excitatory
• GABA - the primary inhibitory neurotransmitter in the brain, involved in anxiety regulation
  • Inhibitory
• Glutamate - the primary excitatory neurotransmitter in the brain, involved in learning and memory
  • Excitatory
• Norepinephrine - involved in arousal, alertness, and mood
  • Excitatory
• Serotonin - involved in mood, sleep, appetite, and aggression
  • Excitatory or inhibitory

The Brain

• Subcortical structures are located beneath the cerebral cortex
  • Basal ganglia plays a role in motor movement
  • Limbic system involved in emotions and motivated behaviors
  • Thalamus relays sensory information (except smell) to the cortex
  • Hypothalamus responsible for regulating basic body functions (e.g., temperature, hunger)
  • Hippocampus involved in memory consolidation (long-term memory)
  • Amygdala processes fear and emotional responses
  • Cingulate cortex involved in emotional and cognitive processing

Cerebral Cortex

• The** cerebral cortex** is the outer layer of the brain responsible for higher-level functions
  • Lobes - frontal, parietal, temporal, and occipital
    • Frontal lobe - involved in planning, reasoning, and personality
    • Parietal lobe - processes sensory information (touch, temperature, pain)
    • Temporal lobe - processes auditory information and language
    • Occipital lobe - processes visual information

Mirror Neurons

• Mirror neurons fire both when a person performs an action and when they observe someone else performing the same action
• May play a role in empathy, imitation, and understanding intentions
• May be involved in language development and learning
• May be helpful for treating stroke victims and people with emotional problems

Common Neurological Disorders and Diseases

• Parkinson's Disease - characterized by tremors, rigidity, and slowed movement
  • Related to dopamine deficiency in the substantia nigra
• Alzheimer's Disease - a progressive neurological disease that causes memory loss and cognitive decline
  • Characterized by the buildup of amyloid plaques and neurofibrillary tangles in the brain
• Multiple Sclerosis (MS) - an autoimmune disease that attacks the myelin sheath of neurons, disrupting the transmission of nerve impulses
  • Causes a range of symptoms, such as fatigue, weakness, and vision problems
• Depression, anxiety, and schizophrenia - are psychological disorders with neurological underpinnings
  • Involve imbalances in neurotransmitter systems

Explore the intricate workings of the nervous system, including the central and peripheral systems. Learn about the somatic and autonomic divisions and their roles in voluntary and involuntary functions. Delve into the brain's structure and its various functions from basic life support to advanced cognitive abilities.