Nervous System and Neurons Quiz

Biological Psychology

• Biological psychology studies the biological underpinnings of behavior.
• Biology explores cells, brains, physiology, the central nervous system, the body itself, and neuroanatomy.
• Psychology is interested in behavior, such as walking, talking, eating, sleeping, and other activities.

Biological Explanations of Behavior

• Physiological explanation: Relates a behavior to the activity of the brain and other organs (e.g., pigeons drink with their heads down due to their neck muscle structure).
• Ontogenetic explanation: Describes the development of a structure or behavior (e.g., early-stage pigeons learn to drink from their parents).
• Evolutionary explanation: Examines a structure or behavior in terms of evolutionary history (e.g., both doves and pigeons have a common ancestor, and thus drink with their heads tilted).
• Functional explanation: Describes why a structure or behavior evolved (e.g., drinking with the head down allows pigeons to drink faster, spend less time on land, and evade predators).

The Mind-Brain Relationship

• Mind-brain problem concerns relationships between mind and brain.
• Dualism: Belief that the mind and body are distinct entities that interact; thought (mind) and physical substance (body).
• Monism: Belief that the universe consists of one substance:
• Materialism: Everything that exists is physical or material.
• Mentalism: Only the mind truly exists.
• Identity position: Mental and brain processes are the same, simply described differently.
• Solipsism: Belief that only the individual's mind exists.
• The problem of other minds involves the difficulty of determining if others have consciousness.

1.1 The Cells of the Nervous System

• Mental experiences depend on interconnected cells' activity.
• Understanding depends on examining nervous system cells.

How Many Neurons Do We Have ?

• Cerebral cortex and associated areas: 12-15 billion neurons.
• Spinal cord: 1 billion neurons.
• Cerebellum: 70 billion neurons (in the back of the brain).

Neurons and Glia, Part 1

• The nervous system consists of neurons and glia.
• Neurons receive and transmit information to other cells.
• Glia's functions include support and insulation of neurons.
• Examples of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.
• The human brain contains approximately 100 billion individual neurons.

The Structures of an Animal Cell, Part 1

• Neurons share cellular structures like other body cells, including membrane, nucleus, mitochondria, ribosomes, endoplasmic reticulum, and Golgi bodies.

An Electron Micrograph of the Parts of a Neuron

• Illustrations of neuron structures (like the nucleus, ribosomes, etc.), provided by electron microscopy.

Types of Neurons

• Sensory neurons (bipolar): Carry messages from the senses (eyes, ears) to the CNS (central nervous system).
• Motor neurons (multipolar): Carry signals from the CNS to muscles and glands.
• Interneurons (pseudopolare): Form neural circuitry within the CNS (brain, spinal cord).

Neurotransmitters

• Neurotransmitters are chemicals that allow impulses to pass from one nerve cell to another.

Types of Neurotransmitters

• Neurotransmitters can be excitatory or inhibitory, depending on their effect on the postsynaptic cell.

Neurotransmitters

• Glutamate: key excitatory transmitter in the majority of fast synapses in the brain and spinal cord, important for memory formation.
• GABA: major inhibitory transmitter in the brain, crucial for controlling neuronal excitability.
• Acetylcholine: key transmitter at the neuromuscular junctions and certain brain areas, involved in muscle actions and cognition.
• Dopamine: involved in reward, motivation, and motor control, dysfunction can cause Parkinson's disease and schizophrenia.
• Serotonin: plays a role in mood, sleep, temperature, and appetite regulation.
• Substance P: a neuropeptide involved in pain transmission.

Neuronal Firing

• Action Potential: Electrical signals in neurons.
• Sodium and potassium pump: Regulates ion concentrations, maintaining the neuron's electrical gradient.

Components of All Neurons

• Dendrites: Receive information.
• Soma/cell body: Contains cell’s nucleus and organelles.
• Axon: Transmits information away from the cell body.
• Presynaptic terminals: Release chemical signals (neurotransmitters).

Dendrites

• Branching fibers lined with synaptic receptors to receive information.
• Dendritic spines increase surface area for information reception.

Cell Body/Soma

• Contains the neuron's nucleus, mitochondria, and ribosomes.
• Responsible for the metabolic work of the neuron.
• Covered by synapses on its surface in many neurons.

Axons

• Thin fibers transmitting nerve impulses to other neurons, organs, or muscles.
• May have myelin sheaths for insulation with nodes of Ranvier.
• Presynaptic terminals at the ends release neurotransmitters.

Afferent, Efferent and Intrinsic Neurons

• Afferent axons: Bring information into a structure.
• Efferent axons: Carry information away from a structure.
• Interneurons/intrinsic neurons: Entirely contained within a particular structure.

Variations Among Neurons

• Neurons vary widely in size, shape, and function.
• Shape determines neuron's connections and contribution to nervous system function.

The Diverse Shape of Neurons

• Diagrams showing examples of neuron diversity and variability.

A Vertebrate Motor Neuron

• Diagram illustrating cell components: dendrites, soma, nucleus, axon, axon hillock, myelin sheath, synaptic terminals, muscle fiber.

A Vertebrate Sensory Neuron

• Diagram featuring components such as dendrites, axon, soma, nucleus, and sensory endings in relation to the skin surface.

Action Potential

• Details on depolarization and repolarization during the action potential.

The Action Potential

• Youtube videos on action potential.

The Membrane of a Neuron

• Diagram of the neuron membrane showing phospholipid bilayer and protein molecules.

Forces Acting on Sodium and Potassium Ions

• The membrane is selectively permeable, allowing some chemicals to pass more freely than others.
• Sodium, potassium, calcium, and chloride pass through channels in the membrane.
• Sodium channels are closed.
• Potassium channels are partially closed, allowing slow potassium passage.

Ion Pathways in the Membrane of a Neuron

• Illustrations of ion channels in a neuron membrane.

Ion Channels

• The sodium-potassium pump is a protein complex that continually pumps three sodium ions out of the cell while drawing two potassium ions into the cell.

Electrical and Concentration Gradients (Resting Potential)

• Electrical gradient pulls sodium ions out of the cell, concentration gradient works in opposition to this.
• However, potassium ions slowly leak out, carrying a positive charge.

Sodium and Potassium Gradient for a Resting Membrane

• Diagrams illustrate the concentration and electrical gradients of sodium and potassium ions across the resting neuron membrane.

The Action Potential, Part 1

• The resting potential remains stable until the neuron is stimulated.
• Hyperpolarization: increasing the polarization or the difference in charge between two places.
• Depolarization: decreasing polarization moving towards zero.
• Threshold of excitation: A level above which any stimulation produces a massive depolarization.

Voltage-Activated Channels

• Membrane channels whose permeability depends on the voltage difference across the membrane. (e.g., sodium & potassium channels)

The Movement of Sodium and Potassium Ions During an Action Potential

• Illustrative graphs showing the changes in the transmembrane electrical potential due to sodium and potassium ionic movement during an action potential.

The Movement of Sodium and Potassium

• After an action potential, sodium channels close, the neuron returns to resting state, potassium flows out, and the sodium-potassium pump restores the original ion distribution.

Restoring the Sodium-Potassium Pump

• The restoration of sodium & potassium ion distribution requires time.
• Unusually rapid action potentials cause sodium buildup, and are potentially toxic.

Blocking Sodium Channels

• Local anesthetic drugs block sodium channels, preventing action potential generation (e.g., Novocain, Xylocaine).

The All-or-None Law, Part 1

• Action potentials back-propagate into dendrites, the neuron becoming more susceptible to structural changes (learning).
• The "all-or-none law": action potential’s amplitude and velocity are independent of the stimulus intensity.

The All-or-None Law, Part 2

• Action potentials vary in amplitude, velocity, and shape across different neurons.
• Mammalian axon studies indicate significant variation in protein channels, leading to differing action potential characteristics.

Refractory Periods

• After an action potential, a refractory period follows, during which a neuron resists producing another action potential.
• Two refractory period phases: absolute (no action potential possible), relative (a stronger-than-usual stimulus is needed).

Propagation of an Action Potential, Part 1

• Action potentials start at the axon hillock (where the axon leaves the cell body).
• Propagation is the transmission of the action potential down the axon.

Propagation of an Action Potential, Part 2

• Elaboration on how signals pass through the axon – the action potential does not travel directly down the axon.

The Myelin Sheath

• The myelin sheath of axons is interrupted by nodes of Ranvier.
• Myelin is an insulating material composed of fats and proteins.
• Action potential regenerates at nodes of Ranvier, propelled by previous segment's positively-charged ions.

An Axon Surrounded by a Myelin Sheath

• Diagram of an axon coated with a myelin sheath, and the nodes of Ranvier.

Saltatory Conduction

• Saltatory conduction: Rapid action potential transmission between the nodes of Ranvier.
• Multiple sclerosis: A disease impacting myelin sheath destruction affecting muscle coordination and vision

Saltatory Conduction in a Myelinated Axon

• Diagrams illustrate the movement of ions during saltatory conduction.

Local Neurons, Part 1

• Local neurons have short axons and do not produce action potentials.
• They produce graded potentials that vary in magnitude according to stimulation.

Local Neurons, Part 2

• These neurons are difficult to study due to their small size, much of our knowledge comes from studies of larger neurons.
• Myth: Only 10 percent of neurons are active at any given moment.
• Truth: All neurons are used, even at times when they are not being used as explicitly as at other specific times.

Santiago Ramón y Cajal, a Pioneer of Neuroscience

• Santiago Ramón y Cajal was a pioneering scientist who demonstrated that individual nerve cells (neurons) remain separate and do not merge.

Neurons and Glia, Part 2: Types of Glia

• Astrocytes: Help synchronize activity within axons by wrapping around presynaptic terminals, taking up released chemicals.
• Microglia: Remove waste material, viruses, and fungi from the brain.

Neurons and Glia, Part 2

• Oligodendrocytes (in the brain and spinal cord) and Schwann cells (in the periphery of the body) build myelin sheath, insulating vertebrate axons.
• Radial glia: Guide the migration of neurons and the development of axons and dendrites during embryonic development.

Neurons and Glia, Part 3

• After embryonic development, most radial glia differentiate into neurons, while others become astrocytes and oligodendrocytes.

Shapes of Various Glia Cells

• Illustrations depicting various glial cell shapes and locations (astrocytes, oligodendrocytes, Schwann cells, microglia, etc.).

How an Astrocyte Synchronizes Associated Axons

• Diagram illustrating how astrocytes synchronize the activities of associated axons; demonstrating the structure of a neuron with an astrocyte.

Glia Cells Video

• Youtube link to a video about glial cells.

The Blood-Brain Barrier

• A mechanism that surrounds the brain, blocking most chemicals.
• The immune system destroys damaged/infected cells.
• The blood-brain barrier protects the delicate neuronal cells from harmful material.

How the Blood-Brain Barrier Works

• Diagram illustrating the mechanisms of the blood-brain barrier, emphasizing the selective permeability.

The Blood-Brain Barrier and the Active Transport

• The blood-brain barrier is important for health, but can prevent certain chemicals from entering (e.g., chemotherapy).
• Active transport (a protein-mediated process): expends energy to pump specific chemicals from blood into the brain (e.g., glucose, hormones, and certain vitamins).

Nourishment of Vertebrate Neurons

• Neurons primarily depend on glucose.
• Neurons require a constant oxygen supply (20% of body's oxygen usage).

Nourishment in Vertebrate Neurons

• Thiamine (vitamin B1) is necessary for glucose use.
• Chronic thiamine deficiency (e.g., Korsakoff's syndrome) leads to neuron death and memory impairment.

Test your knowledge about the human nervous system, including the types of cells, the functions of glial cells, and the structure of neurons. This quiz will challenge your understanding of key concepts like solipsism and the identity position in relation to mental experiences. Perfect for students studying neuroscience or psychology.