Neurophysiology Overview and CNS
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Questions and Answers

What is the primary function of sensory nerve fibers?

  • They secrete neurotransmitters like acetylcholine.
  • They carry motor impulses from the body to the central nervous system.
  • They are responsible for the thickness of nerve fibers.
  • They transmit sensory impulses to the central nervous system. (correct)

Which type of nerve fibers are known to secrete noradrenaline?

  • Type C nerve fibers
  • Type B nerve fibers
  • Cholinergic nerve fibers
  • Adrenergic nerve fibers (correct)

How are Type A nerve fibers classified?

  • By the diameter and conduction velocity (correct)
  • Based on their neurotransmitter secretion
  • By the site of synapse termination
  • According to their myelination status

What is the conduction velocity of Type A gamma fibers?

<p>15 to 30 meters per second (A)</p> Signup and view all the answers

Which statement is true regarding Type C nerve fibers?

<p>They are the thinnest fibers and have the slowest conduction speed. (A)</p> Signup and view all the answers

What is the primary function of attachment proteins such as V SNARE and T SNARE in synapse structure?

<p>Promoting the fusion of vesicles with the presynaptic membrane (A)</p> Signup and view all the answers

Which type of synapse is characterized by the direct passage of ions between neurons through gap junctions?

<p>Electrical synapse (D)</p> Signup and view all the answers

Which type of postsynaptic potential results from the binding of excitatory neurotransmitters and can lead to action potential generation?

<p>Excitatory postsynaptic potential (EPSP) (B)</p> Signup and view all the answers

What is primarily removed from the synaptic cleft to terminate the action of neurotransmitters?

<p>Neurotransmitters (A)</p> Signup and view all the answers

Which of the following accurately describes the composition of the extracellular fluid (ECF) in the synaptic cleft?

<p>Rich in sodium (Na+), chloride (Cl-), and calcium (Ca2+), poor in potassium (K+) (D)</p> Signup and view all the answers

What is the primary responsibility of the somatic nervous system?

<p>Controlling muscular activities and body movements (A)</p> Signup and view all the answers

Which statement correctly distinguishes motor neurons from sensory neurons?

<p>Motor neurons convey impulses from the central nervous system to peripheral effector organs. (A)</p> Signup and view all the answers

Which type of nerve fibers are considered myelinated?

<p>Nerve fibers that have a myelin sheath. (A)</p> Signup and view all the answers

What distinguishes visceral nerve fibers from somatic nerve fibers?

<p>Visceral fibers innervate internal organs. (C)</p> Signup and view all the answers

Which comparison correctly describes cranial nerve fibers versus spinal nerve fibers?

<p>Cranial fibers arise from the brain. (A)</p> Signup and view all the answers

How do sensory neurons generally differ in structure from motor neurons?

<p>Sensory neurons have short axons and long dendrites. (C)</p> Signup and view all the answers

What feature is unique to neurons compared to other cells?

<p>Inability to undergo division. (D)</p> Signup and view all the answers

What classification criterion is used for nerve fibers that distinguishes them based on their origin?

<p>Cranial versus spinal nerve fibers. (C)</p> Signup and view all the answers

What are the two main parts of the nervous system?

<p>Central nervous system and peripheral nervous system (B)</p> Signup and view all the answers

In which part of the brain is the white matter located?

<p>Outer region of the spinal cord (B), Inner region of the cerebrum (D)</p> Signup and view all the answers

What does gray matter predominantly consist of?

<p>Nerve cell bodies and proximal nerve fibers (A)</p> Signup and view all the answers

Which layer of the meninges is closest to the brain and spinal cord?

<p>Pia mater (D)</p> Signup and view all the answers

What is the role of cerebrospinal fluid?

<p>Suspends and protects the brain and spinal cord (A)</p> Signup and view all the answers

What type of neurons are primarily found in the peripheral nervous system?

<p>Sensory neurons (A)</p> Signup and view all the answers

Which part of the nervous system is responsible for quicker responses compared to the endocrine system?

<p>Central nervous system (A)</p> Signup and view all the answers

Which of the following correctly describes the arrangement of gray and white matter in the spinal cord?

<p>White matter is found on the outside, gray matter on the inside (C)</p> Signup and view all the answers

What is the effect of alkalosis on synaptic transmission?

<p>It increases synaptic transmission (C)</p> Signup and view all the answers

Which substance is known to inhibit the effect of GABA and can lead to severe excitatory responses?

<p>Strychnine (D)</p> Signup and view all the answers

What role do small molecules play in the nervous system?

<p>They are responsible for acute rapid responses (A)</p> Signup and view all the answers

How does hypoglycemia affect synaptic transmission?

<p>It decreases synaptic transmission (B)</p> Signup and view all the answers

In which condition does prolonged hypoxia lead to brain damage?

<p>Only after several minutes of oxygen deprivation (B)</p> Signup and view all the answers

Which type of chemical transmitter is known for its prolonged action compared to small molecules?

<p>Neuropeptides (B)</p> Signup and view all the answers

What is a significant effect of the neurotoxin produced by tetanus bacteria?

<p>Prevents the release of GABA (D)</p> Signup and view all the answers

Which of the following diseases is associated with the blockage of acetylcholine release?

<p>Botulism (C)</p> Signup and view all the answers

What is the primary effect of inhibitory postsynaptic potentials (IPSPs) on the postsynaptic membrane?

<p>They cause hyperepolarization of the postsynaptic neuron. (A)</p> Signup and view all the answers

Which of the following describes the mechanism of presynaptic inhibition?

<p>Closure of sodium channels in the presynaptic neuron. (D)</p> Signup and view all the answers

What causes synaptic fatigue during rapid repetitive stimulation?

<p>Exhaustion of synaptic vesicles in the presynaptic neuron. (C)</p> Signup and view all the answers

What characterizes the directionality of synaptic transmission?

<p>Synaptic transmission is unidirectional from presynaptic neurons to postsynaptic neurons. (B)</p> Signup and view all the answers

What is responsible for long-term potentiation in the hippocampus?

<p>Increased levels of glutamate and sodium influx. (C)</p> Signup and view all the answers

During short-term inhibition (habituation), what primarily causes the decreased response to stimuli?

<p>Inactivation of calcium channels and reduced intracellular calcium. (B)</p> Signup and view all the answers

What effect does presynaptic facilitation have on neurotransmitter release?

<p>It increases neurotransmitter release by enhancing calcium entry. (A)</p> Signup and view all the answers

Which term describes the phenomenon where a benign stimulus loses its efficacy due to repeated exposure?

<p>Habituation. (C)</p> Signup and view all the answers

What is the primary function of synaptic plasticity?

<p>To change the function of synapses based on demand. (D)</p> Signup and view all the answers

What is a key feature of synaptic delay?

<p>It represents time needed for synaptic transmission and is approximately 0.5 msec. (D)</p> Signup and view all the answers

Flashcards

Central Nervous System (CNS)

The part of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The part of the nervous system that connects the CNS to the rest of the body.

Gray Matter

Part of the brain and spinal cord composed of nerve cell bodies and the proximal parts of nerve fibers.

White Matter

Part of the brain and spinal cord composed of the remaining parts of nerve fibers.

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Meninges

Three protective membranes covering the brain and spinal cord.

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Cerebrospinal Fluid (CSF)

Fluid that fills the subarachnoid space, surrounds and cushions the brain and spinal cord.

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Cranial Nerves

Nerves that arise directly from the brain.

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Spinal Nerves

Nerves that arise from the spinal cord.

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Sensory Nerve Fibers

Carry sensory impulses from the body to the central nervous system.

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Motor Nerve Fibers

Carry motor impulses from the central nervous system to the body.

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Adrenergic Nerve Fibers

Secrete noradrenaline as a neurotransmitter.

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Type A Nerve Fibers

Thickest nerve fibers with fastest impulse conduction.

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Synapse

Junction where one neuron communicates with another.

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Somatic Nervous System

Part of the nervous system that controls voluntary muscle movements.

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Autonomic Nervous System

Part of the nervous system that regulates involuntary functions like digestion.

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Neuron

Basic unit of the nervous system, transmitting information.

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Motor Neuron

Neuron carrying signals from brain to muscles or other organs.

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Sensory Neuron

Neuron carrying signals from the body to the brain.

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Myelinated Nerve Fiber

Nerve fiber with a fatty coating (myelin) for faster signal transmission.

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Non-myelinated Nerve Fiber

Nerve fiber without myelin sheath, slower signal transmission.

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Cranial Nerve Fibers

Nerve fibers originating from the brain.

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Synaptic Cleft

The small gap between the presynaptic and postsynaptic neurons where neurotransmitters are released.

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EPSP

Excitatory postsynaptic potential; a partial depolarization of the postsynaptic membrane, increasing the likelihood of an action potential.

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Synaptic Transmission

Process of communication between two neurons at a synapse, involving release and binding of neurotransmitters.

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Types of Synapses (Mode)

Synapses can be electrical (rare, gap junctions) or chemical (common, uses neurotransmitters).

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Postsynaptic Potential (PSP)

A temporary change in the postsynaptic membrane potential, either excitatory (EPSP) or inhibitory (IPSP).

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AMPA Receptor Activation

Increased sodium influx into the postsynaptic neuron, triggered by activation of AMPA receptors.

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Synaptic Transmission Factors

Factors influencing the efficiency of information transfer at synapses, including pH, hypoxia, hormones, electrolytes, and drugs

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Long-term Depression (LTD)

A prolonged decrease in the postsynaptic neuron's response to repeated stimulation due to low depolarization.

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Hypoxia Effect

A significant decrease in synaptic transmission and even coma due to insufficient oxygen supply to the brain.

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Hypoglycemia Impact

Reduced synaptic transmission because glucose is the primary energy source for the nervous system.

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Strychnine's Effect

Strychnine inhibits GABA's (inhibitory neurotransmitter) function, leading to heightened excitatory pathways and potential convulsions or death.

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Chemical Transmitters (Small Molecules)

Rapid-acting neurotransmitters responsible for immediate responses in the nervous system, including acetylcholine, amines (norepinephrine, dopamine), amino acids (glutamate, GABA), and others.

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Chemical Transmitters (Large/Neuropeptides)

Potent, slow-acting neurotransmitters with a lasting impact; crucial for prolonged responses. Examples include hypothalamic and pituitary peptides, opioid peptides.

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Temporal Summation

Repeated signals from one presynaptic neuron to one postsynaptic neuron, building up to a response.

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Inhibitory Postsynaptic Potential (IPSP)

A temporary hyperpolarization of a neuron membrane, making it less likely to fire an action potential.

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Presynaptic Inhibition

A 3rd neuron reduces the release of neurotransmitter from a presynaptic neuron, decreasing its stimulation on the postsynaptic neuron.

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Presynaptic Facilitation

A 3rd neuron increases the release of neurotransmitter from a presynaptic neuron, increasing stimulation on the postsynaptic neuron.

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Synaptic Fatigue

Reduced synaptic transmission due to repeated stimulation, which can exhaust synaptic vesicles.

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Synaptic Plasticity

The ability of synapses to change their strength and function over time, depending on activity levels.

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Short-Term Inhibition (Habituation)

Gradual decrease in response to a repeated, harmless stimulus.

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Short-Term Facilitation (Post-Tetanic Potentiation)

Increased response in a postsynaptic neuron for a short period after a burst of stimulation.

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Long-Term Potentiation (LTP)

Long-lasting strengthening of synaptic connections through repeated stimulation. Important for learning and memory.

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Synaptic Delay

The brief period (0.5 msec) it takes for communication across a synapse to occur.

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Study Notes

Neurophysiology Overview

  •  Neurophysiology is the study of the nervous system's functions.
  •  The nervous system controls all bodily activities, faster than the endocrine system.
  •  The nervous system is categorized into the central nervous system (CNS) and peripheral nervous system (PNS).

Central Nervous System (CNS)

  •  The CNS comprises the brain and spinal cord.
  •  Brain tissue and spinal cord are comprised of two layers: gray matter and white matter.
  •  Gray matter consists of nerve cell bodies and proximal parts of nerve fibers originating from the cell body.
  •  White matter contains the remaining parts of nerve fibers.
  •  In the brain, white matter is inner, gray matter is outer.
  •  In the spinal cord, white matter is outer, gray matter is inner.
  •  The brain sits in the skull, continued as the spinal cord through the foramen magnum.
  •  The brain and spinal cord are encased by three meninges: dura mater (outer), arachnoid mater (middle), and pia mater (inner).
  •  The subarachnoid space lies between the arachnoid and pia mater, filled with cerebrospinal fluid (CSF).
  •  Brain regions discussed include Cerebrum, Cerebellum, Midbrain, Pons, Medulla oblongata.
  •  Spinal Cord includes parts like Cervical, Thoracic lumbar, Sacral and Coccygeal parts.

Peripheral Nervous System (PNS)

  •  The PNS is composed of neurons and their processes emanating from the CNS, supplying all body regions.
  •  Parts include cranial nerves from the brain and spinal nerves from the spinal cord.
  •  The PNS has two subdivisions: somatic and autonomic.
  •  Somatic nervous system controls voluntary, skeletal muscle functions.
  •  The autonomic nervous system controls involuntary, visceral functions, divided into sympathetic and parasympathetic divisions.

Neuron Structure and Function

  •  The neuron is the fundamental unit of the nervous system.
  •  Neurons are similar to other body cells, but have branches/processes called axons and dendrites.
  •  Dendrites transmit impulses toward the nerve cell body.
  •  Axons transmit impulses away from the nerve cell body.
  •  Axons and dendrites are collectively called nerve fibers.
  •  Neurons cannot divide.

Nerve Fiber Classification

  •  Myelinated nerve fibers are covered by a myelin sheath.
  •  Non-myelinated nerve fibers lack a myelin sheath.
  •  Somatic nerve fibers supply skeletal muscles.
  •  Visceral (autonomic) nerve fibers supply internal organs.
  •  Cranial nerve fibers originate from the brain.
  •  Spinal nerve fibers originate from the spinal cord.
  •  Sensory (afferent) nerve fibers carry sensory impulses to the CNS.
  •  Motor (efferent) nerve fibers carry motor impulses from the CNS.

Chemical Transmitters

  •  Classified by the substance secreted: Adrenergic (noradrenaline), Cholinergic (acetylcholine)
  •  Small molecules (rapidly-acting)
    • Examples include acetylcholine, norepinephrine, dopamine, serotonin, histamine, glutamate, aspartate, GABA, glycine.
  •  Large molecules (slowly-acting - neuropeptides)
    • Examples include hypothalamic releasing peptides, pituitary hormones, opioid peptides, gastrointestinal peptides, other neuropeptides (e.g., substance P).

Synapses

  •  Synapse is the point of contact between pre- and postsynaptic neurons, without continuity.
  •  Structure: presynaptic terminal, synaptic cleft, postsynaptic membrane.
  •  Synaptic function depends on neurotransmitters.

Synaptic Transmission

  •  Transmission is unidirectional, from pre to postsynaptic neuron.
  •  Shows a delay (0.5 msec).
  •  Factors influencing synaptic transmission include: - Ion concentrations (pH, Ca2+)
    • Hypoxia (lack of oxygen)
    • Hypoglycemia (low blood sugar) - Hormones - Electrolytes
    • Drugs - Diseases (e.g., tetanus, botulism)

Postsynaptic Potentials (PSPs)

  •  Local states of change in the postsynaptic membrane potential.
  •  Types include: Excitatory (EPSP), Inhibitory (IPSP), Grand Postsynaptic Potential - EPSPs result in partial depolarization. - IPSPs result in partial hyperpolarization. - Summation of multiple EPSPs and IPSPs determines whether threshold is reached.

Synaptic Plasticity

  •  Synapses can adjust their function over time (Short and long term).
  •  Short-term plasticity: changes in synaptic transmission lasting seconds or minutes (habituation, facilitation).
  •  Long-term plasticity: changes in synaptic transmission lasting days or weeks (long-term potentiation and depression).
  •  Factors affecting synaptic plasticity include repeated stimulation, transmitter release, activity of enzymes, etc.

Modulation of Presynaptic Potential

  •  Presynaptic neurons can be modulated by third neurons.
  •  This includes presynaptic inhibition(reducing presynaptic neurotransmitter release) and presynaptic facilitation (increasing presynaptic neurotransmitter release).

Mechanisms of Synaptic Inhibition

  •  Direct postsynaptic inhibition
    • When inhibitory presynaptic neurons act directly on postsynaptic membranes.
  • Indirect presynaptic inhibition
    • When the inhibitory third neuron relies on excitatory presynaptic neurons.

Classification of Nerve Fibers

  •  Type A, B and C - differentiated by diameter, myelination. - Type A are the thickest, myelinated fibers (a-alpha, alpha-beta, alpha-gamma, alpha-delta). - Type B - intermediate diameter, myelinated.
    • Type C - the thinnest, non-myelinated fibers.

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This quiz covers the essentials of neurophysiology, focusing on the functions of the nervous system and its components. It highlights the structure and roles of the central nervous system, including the brain and spinal cord, as well as the significance of gray and white matter. Test your knowledge of this vital subject in neuroscience!

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