Neuroscience Reflex Mechanisms Quiz

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Questions and Answers

What does synaptic delay in reflexes suggest about neural pathways?

They are primarily influenced by effector responses.

They involve synaptic gaps that necessitate delays in transmission. (correct)

They are solely dependent on sensory receptors.

They consist of continuous circuits without interruptions.

Which of the following components is NOT involved in the reflex arc as identified by Sherrington?

Control centers in the nervous system

Psychological triggers (correct)

Sensory neurons

Efferent neural pathways

In Sherrington's findings, which response type indicates a more complex interaction at synapses?

Inhibitory responses exclusively

Automatic responses without delay

Excitatory and inhibitory responses (correct)

Reflex responses only

What phenomenon demonstrates that small stimuli can combine to enhance a response?

Spatial and temporal summation Signup and view all the answers

Which of these accurately describes the role of motor neurons in reflex actions as examined by Sherrington?

They transmit responses from the CNS to effectors. Signup and view all the answers

What does Neuron Theory propose about the nature of neurons?

Neurons are the functional units of the nervous system. Signup and view all the answers

What is the primary role of the soma in a neuron?

To synthesize proteins and perform metabolic work. Signup and view all the answers

Which type of neuron carries sensory information toward the central nervous system?

Afferent neurons. Signup and view all the answers

What distinguishes oligodendrocytes from Schwann cells?

Oligodendrocytes can myelinate multiple axons, while Schwann cells typically myelinate one. Signup and view all the answers

Which component of a neuron is primarily responsible for receiving signals?

Dendrites. Signup and view all the answers

What is a common characteristic of microglia in the nervous system?

They eliminate waste and harmful agents. Signup and view all the answers

In which way do Purkinje cells contribute to the nervous system?

They have branching structures that facilitate complex connections. Signup and view all the answers

What is the primary function of Schwann cells in the peripheral nervous system?

They form the myelin sheath around axons. Signup and view all the answers

What role do oligodendrocytes play in the central nervous system?

They form myelin sheaths around axons. Signup and view all the answers

How does the process of saltatory conduction enhance signal transmission?

By allowing action potentials to skip nodes. Signup and view all the answers

What is characteristic of the resting membrane potential in neurons?

It is maintained by ion distribution across the membrane. Signup and view all the answers

Which statement best describes the membrane structure of neurons?

It is a phospholipid bilayer with distinct hydrophilic heads and hydrophobic tails. Signup and view all the answers

Which factor primarily determines the permeability of the cell membrane to a compound?

The molecular size and lipid solubility of the compound. Signup and view all the answers

What role do ligand-gated channels play in neuron function?

They open or close in response to neurotransmitter binding. Signup and view all the answers

Which type of glial cells is responsible for the immune response in the CNS?

Microglia. Signup and view all the answers

What initiates the generation of action potentials in excitable cells?

Changes in the membrane potential due to stimulation. Signup and view all the answers

What role do sodium channels play during the generation of a nerve impulse?

They enable the influx of sodium ions into the cell. Signup and view all the answers

What characterizes the absolute refractory period?

Sodium channels are inactivated, preventing action potential generation. Signup and view all the answers

What happens to potassium channels after an action potential?

They open to help restore the resting state of the neuron. Signup and view all the answers

What is a consequence of excessive activation of neurons?

Sodium buildup within the axon leading to potential neuron death. Signup and view all the answers

How does the sodium-potassium pump restore ion distribution?

By moving ions against their concentration gradients over time. Signup and view all the answers

Why do local anesthetics block sodium channels?

To prevent the generation of action potentials and stop pain sensation. Signup and view all the answers

What occurs during the relative refractory period?

A stronger stimulus is necessary to trigger another action potential. Signup and view all the answers

What is the major risk associated with tetrodotoxin (TTX)?

It blocks sodium channels, preventing action potentials and causing respiratory failure. Signup and view all the answers

What mechanism helps prevent sodium buildup after rapid action potentials?

The sodium-potassium pump restores the ion distribution. Signup and view all the answers

What triggers the opening of voltage-activated channels?

Changes in the membrane potential due to action potentials. Signup and view all the answers

What occurs during hyperpolarization of a neuron's membrane potential?

The membrane potential becomes more negative. Signup and view all the answers

What primary role does the Na⁺/K⁺ pump play in maintaining resting membrane potential?

It pumps 3 Na⁺ ions out and 2 K⁺ ions in. Signup and view all the answers

Which factor primarily determines the resting membrane potential (RMP)?

The unequal distribution of ions across the membrane. Signup and view all the answers

How does an increase in Na⁺ permeability affect the membrane potential?

It results in a more positive membrane potential. Signup and view all the answers

Which statement about the electrical gradient in neurons is accurate?

It promotes the influx of Na⁺ ions. Signup and view all the answers

What is the resting membrane potential (RMP) typically characterized by?

Negative inside the membrane and positive outside. Signup and view all the answers

What effect does the electrical gradient have on K⁺ ions during resting potential?

It repels K⁺ ions out of the cell. Signup and view all the answers

What happens to the membrane potential during repolarization?

The membrane potential returns to its resting state. Signup and view all the answers

Which ion's permeability change most significantly influences the resting membrane potential?

K⁺ Signup and view all the answers

What is the primary function of the sodium-potassium pump?

To establish and maintain the ion concentration gradients across the membrane. Signup and view all the answers

What is the primary action of inhibitory postsynaptic potentials (IPSPs) on a neuron's membrane potential?

They hyperpolarize the membrane, making it more negative. Signup and view all the answers

Which of the following best describes the integration of excitatory and inhibitory postsynaptic potentials?

They combine algebraically, determining the probability of generating an action potential. Signup and view all the answers

In pain response feedback mechanisms, what role does the interneuron play?

It inhibits the main neuron to reduce the pain signal over time. Signup and view all the answers

Which synaptic type is characterized by a connection between an axon terminal and a neuronal cell body?

Axo-somatic. Signup and view all the answers

How do excitatory postsynaptic potentials (EPSPs) affect a neuron's activity?

They depolarize the membrane, increasing the likelihood of firing an action potential. Signup and view all the answers

What is the primary function of myelin in the nervous system?

To insulate axons and speed up signal transmission. Signup and view all the answers

How do Schwann cells differ from oligodendrocytes?

Schwann cells form myelin in the peripheral nervous system, while oligodendrocytes do so in the central nervous system. Signup and view all the answers

What role do microglia play in the central nervous system?

They carry out immune responses and clean cellular debris. Signup and view all the answers

What characterizes the resting membrane potential of excitable cells?

It is around -70mV due to unequal ion distribution across the membrane. Signup and view all the answers

Which statement accurately describes saltatory conduction?

Action potentials jump from one node of Ranvier to the next along myelinated axons. Signup and view all the answers

What property of phospholipid bilayers affects the permeability of the neuron membrane?

Permeability primarily depends on the size and lipid solubility of molecules. Signup and view all the answers

What mechanism facilitates the transport of ions across the neuron's membrane?

Membrane transporters that move ions and large molecules across the membrane. Signup and view all the answers

What primarily drives the movement of molecules in facilitated diffusion?

The chemical gradient Signup and view all the answers

Which statement accurately describes the function of the sodium-potassium pump?

It maintains the concentration gradients of sodium and potassium using ATP. Signup and view all the answers

What is the primary consequence of increased sodium permeability during an action potential?

A significant depolarization of the membrane potential Signup and view all the answers

Which factor significantly influences the resting membrane potential (RMP)?

The permeability of potassium at rest Signup and view all the answers

What characterizes equilibrium potential for an ion?

It is when chemical and electrical gradients are equal. Signup and view all the answers

What is the effect of the electrochemical gradient on ion movement?

It dictates the direction and rate of ion movement across the membrane. Signup and view all the answers

What happens when a potassium leak channel opens?

The membrane potential becomes more negative. Signup and view all the answers

In the context of ion conductance, which statement is true?

Higher ion permeability leads to higher conductance. Signup and view all the answers

Which function is NOT associated with the resting membrane potential?

It is primarily influenced by sodium permeability. Signup and view all the answers

What characterizes the trigger zone in sensory neurons?

It is where the dendrites meet the axon. Signup and view all the answers

Which feature of action potentials ensures they travel in one direction?

Absolute refractory period. Signup and view all the answers

During which period can a stronger-than-normal stimulus generate an action potential?

Relative refractory period. Signup and view all the answers

What does the All or None Law imply about action potentials?

Once triggered, they always reach the same depolarization value. Signup and view all the answers

What physiological function does back-propagation of the action potential serve?

It contributes to synaptic plasticity and Long-Term Potentiation. Signup and view all the answers

What major factor allows action potentials to maintain a consistent speed during propagation?

Sequential opening of sodium channels. Signup and view all the answers

In which type of neuron does the action potential primarily originate from the dendrites?

Unipolar sensory neurons. Signup and view all the answers

What role does the absolute refractory period play in action potentials?

It prevents the generation of new action potentials. Signup and view all the answers

What initiates the domino effect of action potentials along the axon?

Activation of sodium channels due to depolarization. Signup and view all the answers

Which statement regarding the speed of action potentials is accurate?

It can vary due to resting membrane potential. Signup and view all the answers

What distinguishes graded potentials from action potentials?

Graded potentials can vary in amplitude and polarity. Signup and view all the answers

What determines the amplitude of a graded potential?

The strength of the triggering stimulus. Signup and view all the answers

Where do graded potentials primarily occur within a neuron?

In the soma or dendrites. Signup and view all the answers

What occurs during temporal summation of graded potentials?

Two graded potentials from one neuron happen close in time. Signup and view all the answers

What happens to the amplitude of graded potentials as they propagate?

They decrease in amplitude with distance. Signup and view all the answers

What triggers the opening of ion channels in graded potentials?

Interaction between neurotransmitters and receptors. Signup and view all the answers

What is a critical threshold for generating an action potential?

The specific strength needed in a graded potential at the axon hillock. Signup and view all the answers

What is the difference between depolarization and hyperpolarization in graded potentials?

Depolarization increases the likelihood of an action potential, while hyperpolarization decreases it. Signup and view all the answers

In what way do graded potentials differ from action potentials regarding summation?

Graded potentials can sum to trigger action potentials while action potentials cannot. Signup and view all the answers

What role does the axon hillock play in neuronal signaling?

It integrates inputs to decide if an action potential should be generated. Signup and view all the answers

What is the primary role of radial glia during embryonic development?

To guide neuron migration and facilitate axon/dendrite growth Signup and view all the answers

Which statement accurately describes the function of astrocytes?

They regulate material exchange between blood and brain extracellular fluid Signup and view all the answers

Which characteristic best describes the structure of the blood-brain barrier?

It is composed of endothelial cells with tight junctions Signup and view all the answers

How does active transport facilitate the function of the blood-brain barrier?

It requires energy to move chemicals against their concentration gradient. Signup and view all the answers

Which nutrient is primarily relied upon by vertebrate neurons for energy?

Glucose Signup and view all the answers

What distinguishes the function of Schwann cells from that of oligodendrocytes?

Oligodendrocytes can support multiple axons, while Schwann cells support a single axon. Signup and view all the answers

What is a significant challenge presented by the blood-brain barrier?

It complicates the delivery of certain therapeutic drugs to the brain. Signup and view all the answers

Which class of receptors is coupled to G-proteins and does not control ion channels directly?

Metabotropic receptors Signup and view all the answers

Which second messenger is activated by metabotropic receptors and is primarily involved in memory regulation?

cAMP Signup and view all the answers

What type of receptors does acetylcholine utilize within both the neuromuscular junction and the autonomic nervous system?

Both Nicotinic and Muscarinic Signup and view all the answers

Which of the following is NOT a class of metabotropic receptors mentioned?

GABA A receptors Signup and view all the answers

What processes are primarily affected by transcription factors activated through signaling pathways from metabotropic receptors?

Gene expression and regulation Signup and view all the answers

What distinguishes electrical synapses from chemical synapses?

Electrical synapses allow action potential transmission without neurotransmitter release. Signup and view all the answers

Which statement about the pre-synaptic terminal is correct?

It is responsible for storing neurotransmitters. Signup and view all the answers

What effect do gap junctions have on neuron behavior?

They synchronize the activity of connected neurons. Signup and view all the answers

Which type of synapse is more common in the nervous system?

Chemical synapse Signup and view all the answers

What determines whether a synaptic signal will be excitatory or inhibitory?

The type of neurotransmitter released and its receptor type. Signup and view all the answers

What primary role do connexins play in gap junctions?

They form channels that allow ions to flow between neurons. Signup and view all the answers

How does an action potential influence neurotransmitter release at a chemical synapse?

It must arrive at the terminal to facilitate neurotransmitter release. Signup and view all the answers

What characterizes the synaptic release influenced by background activity?

It results in miniature potentials due to constant neurotransmitter release. Signup and view all the answers

What is a key feature of axo-secretory synapses?

They release neurohormones for hormonal signaling into the bloodstream. Signup and view all the answers

What is the role of astrocytes in tripartite synapses?

They buffer neurotransmitter release and generate internal calcium signals. Signup and view all the answers

Which neurotransmitter is primarily associated with excitatory synapses that astrocytes modulate?

Glutamate Signup and view all the answers

What primarily triggers the release of neurotransmitters from synaptic vesicles?

An increase in calcium concentration within the pre-synaptic membrane Signup and view all the answers

What is the significance of Long-Term Potentiation (LTP) in synaptic function?

It indicates a stronger response after repeated activation of a synapse. Signup and view all the answers

Which structures are responsible for storing neurotransmitters before their release?

Storage granules and synaptic vesicles Signup and view all the answers

How do glial transmitters affect synaptic communication?

They can increase or decrease the excitability of both pre- and post-synaptic terminals. Signup and view all the answers

What is a primary function of mitochondria in synaptic terminals?

To generate ATP needed for neurotransmitter release processes. Signup and view all the answers

What role do microtubules play in the synaptic process?

They transport neurotransmitter vesicles from the cell body to the synapse. Signup and view all the answers

What effect do astrocytes have on the concentration of neurotransmitters in the synaptic cleft?

They buffer excess neurotransmitter levels to prevent overstimulation. Signup and view all the answers

What distinguishes metabotropic receptors from ionotropic receptors in terms of response speed?

Metabotropic receptors have a slow response, while ionotropic receptors respond quickly. Signup and view all the answers

Which mechanism correctly describes the action of a second messenger like cAMP in the context of metabotropic receptors?

It activates G-proteins and influences cellular processes. Signup and view all the answers

What type of ion channel is primarily involved in the fast response mechanism of ionotropic receptors?

Ligand-gated channels that open upon neurotransmitter binding. Signup and view all the answers

What effect does the activation of G-proteins have on cellular processes regarding metabotropic receptors?

It initiates the formation of second messengers like cAMP. Signup and view all the answers

In terms of neurotransmitter effects, which statement is true regarding the multiple receptor activation?

The same neurotransmitter can activate both types for different cellular effects. Signup and view all the answers

What is the impact of a second messenger like cAMP on potassium channels upon activation?

It can either open or close potassium channels, depending on the signaling pathway. Signup and view all the answers

How does the structure of ionotropic receptors differ from metabotropic receptors?

Ionotropic receptors are made of 5 subunits forming a pore, metabotropic receptors are not channel-forming. Signup and view all the answers

What physiological changes does the opening of potassium channels induce following cAMP activation?

It causes hyperpolarization, decreasing neuronal excitability. Signup and view all the answers

What process is initiated when a neurotransmitter binds to a metabotropic receptor?

G-protein activation following receptor binding. Signup and view all the answers

In the context of neuromodulation, how do metabotropic receptors impact communication efficiency?

They can modulate communication by altering membrane polarization or gene expression. Signup and view all the answers

What does the GHK equation primarily calculate?

The overall membrane potential based on ion equilibrium and permeabilities Signup and view all the answers

How does the sodium-potassium pump contribute to maintaining resting membrane potential?

By using ATP to pump 3 Na⁺ out and 2 K⁺ in Signup and view all the answers

What role do potassium channels play in establishing resting membrane potential?

They allow K⁺ to leak out of the cell, contributing to the negative inside potential. Signup and view all the answers

What is a direct consequence of the sodium-potassium pump stopping due to the lack of ATP?

The membrane potential dissipates or fades. Signup and view all the answers

When sodium channels open, what is the effect on the membrane potential?

The inside of the cell becomes less negative due to Na⁺ influx. Signup and view all the answers

Which of the following correctly describes the role of ion gradients at resting potential?

K⁺ is high inside the cell while Na⁺ is high outside. Signup and view all the answers

What establishes the equilibrium potential for potassium specifically?

Potassium channels alone. Signup and view all the answers

What is the primary function of the cerebrospinal fluid (CSF)?

To act as a cushion for the brain Signup and view all the answers

Which layer of the meninges is considered the strongest?

Dura mater Signup and view all the answers

What space lies between the dura mater and the arachnoid mater?

Subdural space Signup and view all the answers

How does the blood-brain barrier function in relation to brain tissue?

It prevents direct communication between blood vessels and brain tissue Signup and view all the answers

What is the main consequence of meningitis?

Inflammation of the meninges Signup and view all the answers

What occurs immediately after the membrane potential reaches its peak during an action potential?

Sodium channels inactivate and potassium channels open Signup and view all the answers

During repolarization, which direction do potassium ions primarily move?

Out of the cell Signup and view all the answers

What is the main consequence of the absolute refractory period in neural signaling?

No action potential can be triggered, regardless of stimulus Signup and view all the answers

What characteristic distinguishes the relative refractory period from the absolute refractory period?

Some sodium channels have recovered to an active state Signup and view all the answers

What maintains the resting membrane potential in neurons?

Potassium leak channels Signup and view all the answers

What drives the initial depolarization during an action potential?

Sodium influx Signup and view all the answers

What phenomenon occurs during hyperpolarization in a neuron?

The membrane potential becomes more negative than resting values Signup and view all the answers

What primarily ensures unidirectional propagation of the action potential along the axon?

Refractory periods Signup and view all the answers

Which type of channels are activated based on the membrane voltage difference?

Voltage-activated channels Signup and view all the answers

What is the function of autoreceptors in the brain?

Detect neurotransmitter levels and inhibit release Signup and view all the answers

What type of signaling do endocannabinoids utilize?

Retrograde signaling Signup and view all the answers

Which neurotransmitter is a precursor to serotonin?

Tryptophan Signup and view all the answers

What is the role of cannabinoid receptors when cannabinoids bind to them?

Inhibit further neurotransmitter release Signup and view all the answers

Which of the following neurotransmitter classes does NOT include endocannabinoids?

Modified Amino Acids Signup and view all the answers

How do cannabinoids primarily affect neuronal communication?

By reducing both excitatory and inhibitory messages Signup and view all the answers

Which statement describes the effect of cannabinoid binding on neurotransmitter release?

It inhibits neurotransmitter release from presynaptic terminals Signup and view all the answers

What lipid is primarily involved in the endogenous cannabinoid system?

Anandamide Signup and view all the answers

Which neurotransmitter is classified as a purine?

ATP Signup and view all the answers

What characterizes post-synaptic neurons' role in the feedback mechanism?

Inhibiting further neurotransmitter release from the presynaptic terminal Signup and view all the answers

What distinguishes the synthesis of neuropeptides from other neurotransmitters?

Neuropeptides are synthesized in the cell body. Signup and view all the answers

What triggers the release of neuropeptides?

Repeated depolarization. Signup and view all the answers

Which statement accurately describes the duration of effects for neuropeptides compared to other neurotransmitters?

Neuropeptides have effects lasting many minutes. Signup and view all the answers

How do lipid transmitters like endocannabinoids differ from classical neurotransmitters?

Lipid transmitters are derived from membrane phospholipids or cholesterol. Signup and view all the answers

Which of the following is NOT a characteristic of gaseous transmitters?

They are actively transported into vesicles. Signup and view all the answers

Regarding the action of neuropeptides as neuromodulators, which of the following is true?

They can diffuse widely and influence multiple neurons. Signup and view all the answers

How does the binding of endocannabinoids to receptors impact synaptic transmission?

It inhibits the release of other neurotransmitters. Signup and view all the answers

What factor determines whether a neurotransmitter is excitatory or inhibitory?

The receptor type on the postsynaptic neuron. Signup and view all the answers

Which characteristic is true of ion transmitters like Zinc (Zn2+)?

They are released into the synaptic cleft with other transmitters. Signup and view all the answers

Which of the following components differentiates metabotropic receptors from ionotropic receptors?

Metabotropic receptors lead to slower, longer-lasting effects. Signup and view all the answers

Study Notes

Biological Psychology

Biological psychology studies the biological mechanisms behind behavior and experience, focusing on the brain and body.
The goal is to relate brain function to behavior, understanding that every action has a biological cause.

Mind-Body Problem

Historical roots: Greek-Roman mythology connected behavior to the psyche, not the brain.
Mentalism: The mind controls behavior, but how does a non-material entity direct the body?
Dualism (Descartes): Mind and body are separate but connected via the brain; the pineal gland acts as a bridge. Descartes suggested that the pineal gland was the bridge between the non-material mind and the material body.
Materialism: Behavior is wholly explained by the nervous system, rooted in evolutionary theories.
Gall's Localization: Specific brain areas control particular behaviors (supported by phrenology).

Nervous System

The central nervous system (CNS) includes the brain and spinal cord; the peripheral nervous system (PNS) connects the brain to the body.
The nervous system has functional divisions including the somatic (voluntary) and autonomic (involuntary) nervous systems.
The autonomic nervous system further breaks down into the sympathetic ("fight or flight") and parasympathetic ("rest and digest") divisions. The enteric nervous system (ENS) is also present.
Different structures are connected to different parts of the body.

Brain

The brain interprets sensory information, regulates bodily functions, and supports thinking, learning, memory, and emotions.
Major brain regions include the corpus callosum (connects hemispheres), cerebral cortex (planning, reasoning, language), brainstem (heart rate, breathing), cerebellum (coordination), diencephalon (thalamus, hypothalamus, pineal gland), and the spinal cord.

Neurons

Structure: Nucleus, cell body, dendrites, myelin sheath, axons, and nerve endings.
Communication: Neurons rely on electrical and chemical processes.
Action Potential: Electrical signals travel along axons to send information.
Behavior Control: Influences thoughts, feelings, and responses to rewards and stimuli.
First Recorded Action Potential: By Hodgkin and Huxley in 1939.

Cells of the Nervous System

Neurons (transmit electrical impulses) and glial cells (support and nourish neurons) are interconnected to create mental experiences.
The brain contains about 100 billion neurons.
Santiago Ramón y Cajal's work (late 1800s) proved neurons are separate cells.

Neuron Structure

Neurons are specialized, polarized nerve cells that receive and transmit signals.
Neurons require oxygen and glucose.
They have a high metabolic rate.
Neurons can't be replaced, except by stem cells.

Neuron Components

Dendrites: Receive signals; contain synaptic receptors/dendritic spines (increase surface area).
Soma (Cell Body): Contains nucleus, mitochondria, ribosomes, and manages metabolic tasks.
Axon: Transmits impulses; may be myelinated with nodes of Ranvier/releases chemicals at terminals.
Afferent, Efferent, Intrinsic Neurons: Sensory inputs, motor output, and local connections.
Variations: Vary in size, shape, and function, influencing their connections.

Glial Cells

Astrocytes: Synchronize axon activity, support neurons, form the blood-brain barrier, and take up neurotransmitters.
Microglia: Remove waste, viruses, fungi.
Oligodendrocytes & Schwann Cells: Form myelin sheaths around axons (CNS vs. PNS).
Radial Glia: Guide neuron migration during development.
Ependymal Cells: Secrete cerebrospinal fluid (CSF) and help with ion regulation.

Action Potential

Action potential (AP) is an electrical signal propagating along an axon.
Phases: Depolarization, repolarization, hyperpolarization, resting potential.
Refractory Periods: Absolute (no AP is possible) and relative (stronger stimulus needed for AP).
Saltatory Conduction: Faster AP transmission in myelinated axons.

Exitable Cells

Membrane potential changes due to stimulation, generating APs.
Voltage-gated ion channels facilitate these changes.
Resting membrane potential (-70 mV) due to unequal ion distribution.
Neuron membrane: Phospholipid bilayer.
Membrane permeability depends on lipid solubility and molecular size.
Membrane transporters move ions and molecules.
Ligand-gated channels (ionotropic receptors) involved in synaptic transmission.
Voltage-gated channels crucial for generating action potentials.
Facilitated diffusion (passive) and active transport (e.g., Na+/K+ pump) regulate ion movements.
Electrochemical gradients and equilibrium potentials influence ion movement.
Nernst and GHK equations calculate equilibrium and membrane potentials.

Sodium-Potassium Pump (Na+/K+)

Maintains resting membrane potential.
Actively pumps 3 Na+ out and 2 K+ in using ATP.
Essential to sustain resting potential during neural activity when Na+ influx intensifies; necessary to maintain ion gradients for action potentials.

Ion Movements and Channels

Ion channels are essential for selective ion passage.
K+ channels are open at rest, allowing K+ leakage.
Na+ channels are mainly closed at rest.
Chemical and electrical gradients balance ion movement.
Equilibrium potential exists for each ion.
Resting membrane potential (-70 mV) is influenced by K+ high permeability.

Graded Potentials (GPs)

Graded potentials are changes in membrane potential that vary in size, unlike action potentials (APs).
Stimuli at the synapse, dendrites, or cell body generate them.
They can be depolarizing (+) or hyperpolarizing (-).
They diminish in amplitude as they spread.
Temporal summation: Summation of potentials from one neuron, close together in time.
Spatial summation: Summation of potentials from multiple neurons, nearly simultaneous.
Integration: Summation of EPSPs or IPSPs to determine if the threshold for an AP has been reached.

Synapses

Neurons communicate at synapses (gaps between neurons, discovered by Charles Scott Sherrington in 1906).
Synaptic delay: Delay in communication between neurons, indicating the presence of synapses.
Spatial and temporal summation: Multiple small stimuli can combine to trigger a response, especially as they occur in quick succession.
Excitatory and inhibitory responses: Synapses can cause opposing effects.
Reflex arc: Neural pathway for automatic muscle responses (e.g., withdrawal reflex).

Tripartite Synapses

Synapses and astrocytes collaborate to modulate synaptic activity. Astrocytes take up and release glial transmitters influencing synaptic communication. They also buffer neurochemicals, like glutamate.
This tripartite interaction enhances synaptic plasticity via changes in receptors' expression and sensitivity.

Quadpartite Synapses

Includes microglia enhancing or suppressing synaptic activity.
Dysfunctional glial cells are associated with aberrant synaptic plasticity in psychological disorders, like depression.

Neurons and Neurotransmission

Neurons communicate via neurotransmitters (chemicals).
Neurotransmitters work with receptors to generate an active response.
Types of receptors:
- Ionotropic: Fast, direct effects on ion channels.
- Metabotropic: Slow, involve signalling cascades via secondary messengers.
Synaptic transmission: 5 steps (synthesis, packaging, transport and release, binding, and termination of signaling).
Neurotransmitter inactivation: Occurs via diffusion, degradation, or reuptake.
Types of neurotransmitters: Amino acids (glutamate, GABA), amines (dopamine, serotonin, norepinephrine), neuropeptides, gases, and lipids (endocannabinoids).
Quantal release suggests that neurotransmitter release occurs in discrete packets (quanta).
Different classes of neurotransmitters have varying impact on the brain (speed, pathways, and role in different systems).
Drugs often act as agonists or antagonists influencing neurotransmitter activity.

Neuron Structure (Electrical and Chemical Signals)

Neuron membrane structure: Phospholipid bilayer, crucial for regulating movement of ions and larger/larger molecules.
Channels and pumps: Essential for maintaining resting potential and rapid, graded potentials; neurons respond to and send signals electrochemically.
Two types of receptors (speed, pathways, final activity)
- Ionotropic: Fast effects through direct ion channel opening.
- Metabotropic: Slow effects through secondary messenger systems like cAMP modulation, affecting various neural functions.
G-proteins: Relay transmitters' signals inside the cell.

Anatomy of the Nervous System

Central Nervous System (CNS) components: Brain, spinal cord.
Peripheral Nervous System (PNS) function: Connects CNS to body; includes somatic (voluntary) and autonomic (involuntary) divisions.
Directional terms: Rostral/caudal, ventral/dorsal, anterior/posterior, superior/inferior, lateral/medial and ipsilateral/contralateral are used to reference locations and directions in the nervous system; also included are coronal, horizontal, and sagittal planes to visualize the brain.
Neural structures: Laminae (layer), columns (organization structure), tract (axons), nerve (axon/dendrite bundles).

Meninges

Meninges: Protective coverings (dura mater, arachnoid mater, pia mater) around the brain and spinal cord.
CSF circulation and its role in protection and support; also CSF cushioning of the brain and spinal cord.

The Brain Stem

Structures: Medulla, pons, midbrain.
Functions: Control of vital reflexes, pathways for signals, sleep-wake cycles, movement regulation; integrates movement and sensory data.

Cerebellum

Location: Back of the brain, above the pons.
Structure: Highly folded structure.
Functions: Motor learning, timing, coordination of movements, balance, attention shifts; also important for motor learning and error correction, contributing to smooth, coordinated movements.
Cerebellar homunculus: Representation of body parts in cerebellum.

Diencephalon

Structures: Thalamus, hypothalamus, pineal gland.
Functions: Relay station for sensory information (thalamus), maintains homeostasis (hypothalamus), hormone function (hypothalamus), sleep cycles/circadian rhythms (pineal gland).

Forebrain (Cerebrum)

Organization: Two hemispheres; layers.
Functions: Higher cognitive functions (perception, planning, emotions, personality, and personality), integrating sensory input; includes allocortex and neocortex.
Allocortex: Important for motivation, emotion, and memory.
Neocortex: Critical for complex cognitive tasks.
Basal ganglia: Structures underneath the cortex, involved in motor control, memory, and emotional expression (e.g., initiation of skilled movement, reward); important for selection and execution of movements.

Spinal Cord

Location: Central nervous system; within the spinal column.
Structure: Segmented; grey and white matter.
Signals: Relay signals for sensory and motor functions via dorsal and ventral roots; also crucial for spinal reflexes.
Spinal reflexes (e.g., knee-jerk reflex, crossed extensor reflex): Control rapid, automatic responses without conscious engagement from the brain (sensory & motor involvement).
Neural pathways moving motor and sensory information along the length of the spinal cord.

Peripheral Nervous System (PNS)

PNS components: Motor and sensory neurons bundled in nerves, somatic (voluntary) and autonomic (involuntary).
Motor nerves: Carry signals for muscle contraction.
Sensory nerves: Carry sensory information.
Mixed nerves: Contain both motor and sensory fibers.
Nerve structure: Myelinated axons bundled with connective tissue; different types of nerves exist (motor, sensory, or mixed), based on function.

Autonomic Nervous System (ANS)

The autonomic nervous system controls involuntary bodily functions.
Divisions: Sympathetic (stimulatory, "fight or flight") and parasympathetic (inhibitory, "rest and digest").
Anatomical differences: Ganglia location (near spinal cord vs. near target organs), length of pre- and post-ganglionic fibers.
Neurotransmitters: Acetylcholine and norepinephrine.
Receptors: Varying receptor types on target tissues, resulting in different effects; receptors present on the target tissues are either nicotinic or muscarinic (sympathetic/parasympathetic, respectively).

Senses

Sensory division of the peripheral nervous system collects information from the external and internal environment and sends it to the brain.
Sensory receptors transduce stimuli (converting physical energy into electrical signals).
Different receptors respond to distinct types of stimuli; a primary sensory receptor converts stimuli of a particular kind to a nerve impulse.
Pathways: From receptors/ganglia to the brain, crossing the midline (opposite) in many cases.
Coding: Converts stimuli to patterns of neural activity.
Adaptation: Receptors adjust to sustained stimuli.

Auditory System

Detects sound waves (periodic air compressions).
Ear anatomy: Outer, middle, inner ear structures.
Cochlea: Transduces sound waves into electrical signals.
Hair cells: Sound detectors in the cochlea, bending in response to vibrations that activate neural signals.
Auditory pathways/cortex: Process and code auditory information (frequency, loudness).
Tonotopic organization: Specifies frequency-specific areas in the auditory cortex.
Sound localization: Identifies the source of sounds by analyzing differences in arrival time and intensity between ears.
Pathways: Cochlea→ brain stem → inferior colliculus in midbrain → medial geniculate nucleus (thalamus) → auditory cortex (processing and analysis).
Processing pathway differences: "What" pathway identifies sounds; "how" pathway facilitates movement in response to sounds.

Visual System

Perceives light energy in the visible spectrum (400-700 nm).
Eye structure: Cornea, pupil/iris, lens, retina.
Retina: Convert light energy to electrical signals (transduction from light to electrical signals).
Fovea: Region of sharpest vision, contains cones, and each cone activates one bipolar neuron).
Rods: High sensitivity to dim light; located peripherally, many rods converge onto a single neuron).
Cones: High acuity and color vision; concentrated in the fovea, each cone activates one bipolar neuron.
Phototransduction: Converts light into electrical signals.
Visual pathways: Optic nerve, optic chiasm, lateral geniculate nucleus (thalamus), visual cortex (processing and analysis).
Dorsal and ventral streams: Separate visual processing pathways ("where" and "what").
Visual fields and receptive fields: Define visual region/stimulation to activate a neuron.
Color vision: Trichromatic and opponent-process theories explain color perception.
Blind spot: Region of the retina lacking photoreceptors where the optic nerve exits the eye.

Movement

Hierarchical motor system organization: Cerebral cortex plans and initiates movement, with brainstem and spinal cord executing the action.
Parallel processing: Allows the brain to coordinate several independent actions simultaneously.
Feedback mechanisms: Continuously adapt movement based on sensory information.
Muscles, muscle fibers, and motor units enable movement.
Antagonistic muscle pairs (e.g., biceps and triceps) enable coordinated movement.
Proprioceptors (muscle spindles and Golgi tendon organs) provide feedback for movement accuracy.
Pathways through the spinal cord, brain stem, and cerebellum refine movement.
Motor and Sensory areas receive information from each other, allowing for the development of a response. Motor and Somatosensory cortices work together in parallel to coordinate movements and sensations.

Neurotransmitters and Psychoactive Drugs

Many psychoactive drugs influence neurotransmitters and receptors in the nervous system which alters the behaviour; drugs can act as agonists or antagonists for specific neurotransmitters.
Studying drug actions involves understanding neurotransmitter systems and their influence on various brain functions; drugs affect different neurotransmitter systems and vary in their effects (doses, timing, frequency of exposure, and route of administration).
Tolerance and sensitization are critical concepts indicating adaptations to drug use. The brain adapts to the presence of the drug leading to tolerance. The brain also adapts to the constant presence of the drug, leading to sensitization.

Brain Development

Brain development involves processes across the entire body which affect the entire CNS.
Neuronal development: Proliferation, migration, differentiation, maturation (axon/dendrite growth), synaptogenesis, apoptosis, and myelination.
Neurogenesis: The creation of new neurons.
Migration: Neurons move to their destinations.
Differentiation: Neurons specialize into specific types.
Maturation: Refinement of neurons that happen throughout the entire body.
Synaptogenesis: Formation of synapses.
Apoptosis: Programmed neuron death.
Myelination: Formation of the myelin sheath around axons.
Neural Darwinism: Neurons competing for resources and connections.
Neurotrophic factors (NGF): Support neuron survival and growth.
Experience and neural connectivity: Experience during development significantly shapes neural connections through physical and chemical effects (chemical gradients, signalling, etc.)
Enriched environments promote brain development.
Sensitive periods: Specific developmental windows when experiences have greater impacts.

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Test your knowledge on the reflex arc, synaptic delay, and neuronal structures based on Sherrington's findings in neuroscience. This quiz will cover the roles of different neurons and glial cells, and explore the principles of Neuron Theory. Challenge yourself and strengthen your understanding of neural pathways and reflexes.