Nervous System and Neuroglia Cells

• The nervous system is the body's control center, overseeing communication between organ systems.
• It performs sensory input, integration, and motor output functions.

Nervous Tissue Composition

• Neurons (nerve cells) are excitable cells that transmit signals.
• Neuroglia (glial cells) are supportive cells that provide nutrition, insulation, and aid in signal transmission.

Types of Neuroglia Cells

• Astrocytes are in the CNS, regulate synapse function, support neurons metabolically, and protect against toxic compounds.
• Ependymal cells line brain cavities and the spinal cord, producing cerebrospinal fluid.
• Microglial cells are throughout the brain and spinal cord of the CNS, remove debris, and regulate brain development.
• Oligodendrocytes provide myelin membranes to insulate CNS axons.
• Satellite cells in the PNS supply nutrients and act as protective cells for surrounding neurons.
• Schwann cells in the PNS form myelin sheaths around axons to aid nerve impulse conduction and regeneration.

Neuron Structure

• Soma (cell body) contains the nucleus and organelles.
• Processes are extensions from the cell body, including dendrites and axons.
  • Dendrites receive signals (input region).
  • Axons generate and transmit nerve impulses (conducting region/nerve fiber).
• Ganglia are collections of nerve cell bodies outside the brain and spinal cord.
• Nerves are bundles of axons extending from the brain and spinal cord.
  • Axon terminals release neurotransmitters at a synapse (secretory region).
• The myelin sheath covers long axons to protect and insulate, increasing nerve impulse speed.
• Nodes of Ranvier are unmyelinated gaps in the myelin sheath that increase signal conduction velocity.

Neuron Classification (Structural)

• Multipolar neurons have more than 3 processes (one axon, two or more dendrites); 99% of neurons are multipolar.
• Bipolar neurons have 2 processes (one axon, one dendrite on opposite ends); rare, found in special sense organs.
• Unipolar neurons have 1 process, dividing from the cell body like a T; found in PNS ganglia.

Neuron Classification (Functional)

• Sensory (afferent) neurons transmit information from sensory receptors to the CNS; most are unipolar.
• Motor (efferent) neurons transport information from the CNS to the rest of the body; most are multipolar.
• Interneurons (association neurons) in the CNS transport information between sensory and motor neurons; most are multipolar.

Organization of the Nervous System

• The nervous system consists of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
• The CNS includes the brain and spinal cord for integration and control.
• The PNS includes spinal and cranial nerves to communicate between the CNS and the body.
• The PNS divides into sensory (afferent) and motor (efferent) divisions.
• The motor division has somatic (voluntary) and autonomic (involuntary) nervous systems.
• The autonomic nervous system includes parasympathetic and sympathetic branches.

CNS

• The brain is protected by the skull, meninges, and cerebrospinal fluid.
• Ventricles are fluid-filled cavities in the brain containing the choroid plexus, which produces cerebrospinal fluid.
• The cerebrum is the largest part of the brain.
  • It has left and right hemispheres and four lobes.
  • Functions include learning, speech, emotion, reasoning, vision, hearing, and fine movements.
  • The surface is the cerebral cortex, arranged in folds to increase surface area.
• The cerebellum is under the cerebrum.
  • It maintains posture and balance.
  • It coordinates timing and patterns for smooth and agile movements.
• The brainstem is the base of the cerebrum and anterior to the cerebellum.
  • Includes the medulla oblongata, midbrain, and pons.
  • Relays information and coordinates automatic functions like respiration, circulation, body temperature, sleep, digestion, and swallowing.

PNS

• The autonomic nervous system (ANS) includes sympathetic (fight or flight) and parasympathetic divisions.
• Sensory nerve receptors take in stimuli and send them to the brain to interpret and respond.
• Mechanoreceptors detect mechanical force (vibration, pressure, stretch, touch).
• Thermoreceptors detect temperature changes.
• Photoreceptors detect light.
• Chemoreceptors detect chemicals.
• Nociceptors detect pain.

Reflexes

• Reflexes are automatic reactions to stimuli.
  • Can be innate/intrinsic or learned/acquired.
• The reflex arc is the neural pathway for reflexes.
  • Includes a receptor, sensory neuron, integration center, motor neuron, and effector.

Vocab

• Soma (cell body): The main part of a neuron that contains the nucleus and organelles.
• Dendrites: Branch-like extensions of a neuron that receive signals from other neurons.
• Axon: A long, slender projection of a neuron that transmits electrical impulses.
• Ganglion: A cluster of neuron cell bodies in the peripheral nervous system.
• Nerve: A bundle of axons that transmit signals between the brain, spinal cord, and body.
• Axon terminal: The endpoint of an axon where neurotransmitters are released.
• Myelin sheath: A fatty layer that insulates axons and speeds up nerve impulses.
• Nodes of Ranvier: Gaps in the myelin sheath that facilitate rapid signal transmission.
• Sensory neurons: Neurons that carry signals from sensory receptors to the central nervous system.
• Motor neurons: Neurons that transmit signals from the central nervous system to muscles or glands.
• Interneurons: Neurons that connect sensory and motor neurons within the central nervous system.
• Resting membrane potential: The electrical charge difference across a neuron's membrane at rest.
• Graded potential: A small, localized change in membrane potential that varies in strength.
• Threshold: The minimum membrane potential needed to trigger an action potential.
• Action potential: A rapid electrical signal that travels along a neuron.
• Nerve impulse: The transmission of an action potential along a nerve fiber.
• Depolarization: The process of a neuron's membrane potential becoming more positive.
• Repolarization: The restoration of a neuron's negative membrane potential after depolarization.
• Hyperpolarization: A change in membrane potential that makes a neuron more negative than its resting state.
• Synapse: The junction between two neurons where communication occurs.
• Meninges: Protective membranes that surround the brain and spinal cord.
• Ventricle: Fluid-filled cavities in the brain that produce and circulate cerebrospinal fluid.
• Cerebrum: The largest part of the brain responsible for higher cognitive functions.
• Cerebellum: The brain region that coordinates movement and balance.
• Brain stem: The structure that connects the brain to the spinal cord and controls vital functions.
• Neurotransmitter: A chemical messenger that transmits signals across a synapse.
• Hormone: A chemical released by glands that regulates physiological processes.
• Mechanoreceptor: A sensory receptor that detects touch, pressure, and vibration.
• Thermoreceptor: A sensory receptor that responds to temperature changes.
• Photoreceptor: A sensory receptor in the eye that detects light.
• Chemoreceptor: A sensory receptor that detects chemical stimuli, such as taste or smell.
• Nociceptor: A pain receptor that detects harmful stimuli.
• Reflex: An automatic, involuntary response to a stimulus.
• Sclera: The white, protective outer layer of the eye.
• Cornea: The transparent front part of the eye that helps focus light.
• Choroid: The vascular layer of the eye that supplies nutrients and oxygen.
• Ciliary body: A structure that controls the shape of the lens and produces aqueous humor.
• Exocrine: Glands that release secretions through ducts, such as sweat glands.
• Endocrine: Glands that release hormones directly into the bloodstream.
• Humoral stimuli: Hormone release triggered by changes in blood levels of certain substances.
• Neural stimuli: Hormone release triggered by nerve signals.
• Hormonal stimuli: Hormone release triggered by other hormones.
• Permissiveness: When one hormone enhances the effects of another hormone.
• Synergism: When two hormones work together for a stronger effect.
• Antagonism: When one hormone opposes the action of another hormone.
• Iris: The colored part of the eye that controls the size of the pupil.
• Pupil: The opening in the iris that regulates the amount of light entering the eye.
• Suspensory ligament: Fibers that hold the lens in place and adjust its shape for focusing.
• Retina: The light-sensitive layer of the eye that contains photoreceptors.
• Optic nerve: The nerve that carries visual information from the retina to the brain.
• Fovea centralis: A small pit in the retina responsible for sharp central vision.
• Optic disc: The blind spot in the retina where the optic nerve exits the eye.
• Rods: Photoreceptors in the retina that detect low light and peripheral vision.
• Cones: Photoreceptors in the retina that detect color and fine details.
• Lens: A transparent structure that focuses light onto the retina.
• Vitreous humor: The gel-like substance that fills the interior of the eye.
• Aqueous humor: The fluid that nourishes and maintains pressure in the front of the eye.
• Odor: A scent detected by olfactory receptors.
• Olfactory epithelium: The sensory tissue in the nasal cavity that detects smells.
• Taste buds: Clusters of sensory cells on the tongue that detect flavors.
• Papillae: Small bumps on the tongue that contain taste buds.
• Gustatory epithelial cells: The receptor cells responsible for detecting taste stimuli.
• Basal epithelial cells: Cells that replace worn-out gustatory cells.

Key Functions and Processes

• Sensory Input: Detects stimuli, and signals travel via sensory neurons.
• Integration: Processing of sensory information in the brain/spinal cord.
• Motor Output: Sending signals to muscles and glands.
• Response: The body's reaction to the motor output.

Types of Nervous Tissue Cells

• Neurons: Transmit electrical and chemical signals.
• Neuroglia (Glial Cells): Support, protect, and nourish neurons.

Signal Transmission Between Neurons

• Action Potential: Travels down the axon.
• Synapse: Releasing neurotransmitters at the axon terminal.
• Neurotransmitters: Binding to receptors and generating a response.
• Signal Strength: Determined by neurotransmitter quantity and receptor sensitivity.

Role of Protein Channels in Nerve Impulses

• Na+/K+ Pump: Maintains resting membrane potential.
• Depolarization: Na⁺ channels open, making the cell more positive.
• Repolarization: K⁺ channels open, restoring negativity.
• Hyperpolarization: Overshoot before balance is restored.

Types of Gated Protein Channels

• Voltage-Gated: Respond to voltage changes (Na⁺ & K⁺ channels in action potentials).
• Ligand-Gated: Open when a specific neurotransmitter binds.
• Mechanically-Gated: Open in response to pressure or stretch.

Neurotransmitters

• Excitatory: Increase action potential likelihood (e.g., glutamate, dopamine).
• Inhibitory: Decrease action potential likelihood (e.g., GABA, serotonin).

Nervous System Divisions

• CNS: Brain and spinal cord (processes and integrates info).
• PNS: Nerves outside the CNS (connects CNS to the body).

Brain Sections

• Cerebrum: Higher thinking, memory, voluntary movements.
• Cerebellum: Coordination, balance, fine motor control.
• Brainstem: Controls automatic functions.

PNS Divisions

• Sensory (Afferent): Sends signals from receptors to the CNS.
• Motor (Efferent): Sends signals from CNS to muscles/glands.

Motor systems

• Somatic: Voluntary control (skeletal muscles).
• Autonomic: Involuntary control (organs, glands).

Autonomic Branches

• Parasympathetic ("Rest & Digest"): Lowers heart rate, increases digestion.
• Sympathetic ("Fight or Flight"): Increases heart rate, slows digestion.

Reflexes

• Innate: Automatic, built-in responses.
• Learned: Acquired through experience.

Sense

• General: Touch, pain, temperature (spread throughout the body).
• Special: Vision, hearing, taste, smell, equilibrium (specific organs).

Overview of the nervous system's function as the body's control center. Discussion of nervous tissue composition, including neurons and neuroglia. Examination of neuroglia cells such as astrocytes, ependymal cells, microglia, oligodendrocytes, satellite cells, and Schwann cells.