Nervous System: CNS and PNS
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What is the primary event that initiates the depolarization of a neuron during the generation of an action potential?

  • Pumping of sodium ions (Na+) out of the cell.
  • Influx of sodium ions (Na+) into the cell. (correct)
  • Outflow of potassium ions (K+) from the cell.
  • Closing of voltage-gated calcium channels.

An action potential will always be generated regardless of the strength of the stimulus applied to a neuron.

False (B)

Describe the state of the neuron's plasma membrane (charge inside and outside) during its resting state.

During the resting state, the external surface of the neuron's plasma membrane is slightly positive, while the internal face is slightly negative.

During depolarization, the inner surface of the neuron membrane becomes more ______ as _____ ions enter the cell.

<p>positive</p> Signup and view all the answers

Match the term with its description during the generation of a nerve impulse:

<p>Resting State = External surface of neuron's plasma membrane slightly +ve and Internal face slightly -ve Depolarization = Inside becomes more +ve whereas outside become more -ve (graded potential) Action Potential = Depolarisation causes membrane polarity to be completely reversed Nerve impulse = Either propagated (conducted or sent) over entire axon or doesn’t happen at all.</p> Signup and view all the answers

Which of the following statements accurately describes the function of Schwann cells?

<p>Forming the myelin sheath around axons in the peripheral nervous system, analogous to oligodendrocytes in the CNS. (B)</p> Signup and view all the answers

The presence of myelin sheaths contributes to the white appearance of white matter in the central nervous system.

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

What is the typical resting membrane potential (RMP) of a neuron, and what does the negative voltage indicate?

<p>-70mV, it indicates that the inside of the plasma membrane contains more negative charge compared to the outside.</p> Signup and view all the answers

Gaps in the myelin sheath along an axon are known as _______.

<p>Nodes of Ranvier</p> Signup and view all the answers

What is the 'all-or-none' principle regarding action potentials?

<p>Any stimulus that reaches the threshold will generate a full action potential; otherwise, no action potential occurs. (C)</p> Signup and view all the answers

Graded potentials can propagate along the entire plasma membrane without losing strength.

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

Match the functional properties of neurons with their descriptions:

<p>Irritability = Ability to respond to a stimulus and convert it into a nerve impulse Conductivity = Ability to transmit a nerve impulse to other neurons, muscles, or glands</p> Signup and view all the answers

The action potential in a neuron is also known as a:

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

Which of the following best describes the primary function of the nervous system?

<p>To maintain homeostasis and provide quick, brief responses. (B)</p> Signup and view all the answers

The central nervous system (CNS) consists of all neural tissue outside the brain and spinal cord.

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

What are the two main functional divisions of the peripheral nervous system (PNS)?

<p>Afferent and Efferent</p> Signup and view all the answers

The division of the efferent nervous system responsible for controlling skeletal muscle contractions is the ______ nervous system.

<p>somatic</p> Signup and view all the answers

Match each division of the autonomic nervous system with its primary function:

<p>Sympathetic division = Fight or flight response Parasympathetic division = Rest and digest</p> Signup and view all the answers

Which type of neuroglia is responsible for forming the myelin sheath around axons in the central nervous system (CNS)?

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

Neurons in the adult nervous system can readily divide and regenerate if damaged.

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

What is the primary function of the axon hillock?

<p>Generation of action potential</p> Signup and view all the answers

Clusters of rough endoplasmic reticulum (RER) and ribosomes in the neuron cell body that produce neurotransmitters are called ______ bodies.

<p>Nissl</p> Signup and view all the answers

Which type of neuron is most commonly found in the CNS and includes all motor neurons that control skeletal muscles?

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

Sensory neurons are also known as efferent neurons.

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

What is the role of interneurons in the nervous system?

<p>Connect sensory and motor neurons</p> Signup and view all the answers

The blood-brain barrier is maintained by ______, which secrete chemicals that isolate brain tissue from general circulation.

<p>astrocytes</p> Signup and view all the answers

Which of the following neuroglia are phagocytic cells that clean up cellular debris, waste products, and pathogens in the CNS?

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

Match the type of neuron with its location:

<p>Unipolar neurons = Sensory neurons of PNS Bipolar neurons = Special sensory organs (sight, smell, hearing) Interneurons = Brain and Spinal cord</p> Signup and view all the answers

During the propagation of an action potential, what causes the repolarization of the membrane?

<p>Efflux of K+ ions out of the cell. (C)</p> Signup and view all the answers

Saltatory propagation of action potentials occurs in unmyelinated axons and is relatively slow.

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

What is the role of acetylcholinesterase (AChE) at the synapse?

<p>To remove acetylcholine (ACh) from the synaptic cleft</p> Signup and view all the answers

The junction between a neuron and a muscle cell is known as a ______ junction.

<p>neuromuscular</p> Signup and view all the answers

Which part of the neuron is the starting point for the generation of an action potential?

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

Neurons contain centrioles, allowing them to readily divide and regenerate after injury.

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

What is the primary function of dendrites on a neuron?

<p>To receive stimulation</p> Signup and view all the answers

The somatic motor neurons innervate ______ muscles.

<p>skeletal</p> Signup and view all the answers

Which of the following structures contains the axons of sensory neurons?

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

The gray matter of the spinal cord is primarily composed of myelinated nerve fibers.

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

In which segments of the spinal cord is the lateral gray horn found?

<p>Thoracic and lumbar</p> Signup and view all the answers

During synaptic transmission, extracellular ______ enters the axon terminal and triggers exocytosis of acetylcholine.

<p>calcium</p> Signup and view all the answers

Which division of the autonomic nervous system has ganglia located near or within the target organs?

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

Match the characteristic to the correct division of the autonomic nervous system:

<p>Sympathetic division = Short preganglionic fibers Parasympathetic division = Long preganglionic fibers</p> Signup and view all the answers

Flashcards

Resting membrane potential

The electrical charge difference across a neuron's membrane when it is not active, typically around -70 mV.

Depolarization

A change in membrane potential where the inside of the neuron becomes more positive due to Na+ influx.

Action potential

A rapid and substantial change in membrane potential that constitutes a nerve impulse.

Na+ ion diffusion

The movement of sodium ions into the neuron when the membrane becomes permeable.

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All-or-none response

The principle that an action potential either occurs fully or not at all, once the threshold is reached.

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Nervous System

Works with endocrine system to maintain homeostasis and provide quick responses.

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CNS and PNS

CNS includes the brain and spinal cord; PNS includes all neural tissues outside CNS.

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Afferent Division

Carries sensory information from receptors to the CNS.

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Efferent Division

Carries motor commands from the CNS to effectors like muscles and glands.

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Somatic Nervous System

Controls skeletal muscle contractions under voluntary control.

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Autonomic Nervous System

Regulates involuntary functions, controlling smooth and cardiac muscles.

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Neurons

Basic functional units that send and receive signals.

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Neuroglia

Support and protect neurons, not sending or receiving signals.

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Multipolar Neurons

Neurons with multiple dendrites and one long axon, common in CNS.

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Unipolar Neurons

Sensory neurons with continuous dendrites and axons; cell body is to one side.

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Bipolar Neurons

Rare neurons with one dendrite and one axon, found in special sensory organs.

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Astrocytes

Largest neuroglia forming structural framework for CNS and maintaining blood-brain barrier.

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Oligodendrocytes

Neuroglia that form myelin sheath around axons, speeding up electrical impulses.

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Microglia

Smallest neuroglia that act as phagocytic cells cleaning up cellular debris.

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Ependymal Cells

Line the cavities of the brain and spinal cord, some secrete cerebrospinal fluid.

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Satellite cells

Support and surround neuron cell bodies in the PNS.

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Schwann cells

Form myelin sheath around peripheral axons.

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Myelination

Process that increases nerve transmission speed and makes nerves appear white.

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Nodes of Ranvier

Gaps between adjacent myelin sheaths in a nerve.

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Graded potentials

Local changes in membrane potential in response to stimuli, not spreading far.

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Threshold

Level of membrane potential that must be reached to trigger an action potential.

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Propagation of Action Potential

The spread of action potentials along the membrane, triggered by depolarization and ion movement.

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Sodium-Potassium Pump

A mechanism restoring ion concentrations by pumping 3 Na+ out and 2 K+ in, maintaining resting potential.

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Continuous Propagation

Slow transmission of action potential in unmyelinated axons due to gradual depolarization along the entire length.

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Saltatory Propagation

Rapid transmission of action potential in myelinated axons, jumping from node to node.

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Synapse

The junction where one neuron communicates with another or an effector cell.

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Presynaptic Neuron

The neuron sending the signal at the synapse, releasing neurotransmitters from its terminals.

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Postsynaptic Neuron

The neuron receiving the signal at the synapse, with receptors for neurotransmitters.

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Neurotransmitter

Chemicals released by neurons to transmit signals across a synaptic cleft.

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Acetylcholine (ACh)

A common neurotransmitter released at synapses affecting muscle contraction and memory.

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Acetylcholinesterase (AChE)

Enzyme that breaks down acetylcholine in the synaptic cleft, stopping its action.

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Sensory Neurons

Neurons that carry information from sensory receptors to the CNS, involved in sensing the environment.

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Motor Neurons

Neurons that transmit instructions from the CNS to muscles and glands, facilitating movement or action.

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Interneurons

Neurons connecting sensory and motor neurons, involved in processing information within the CNS.

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Study Notes

Nervous System

  • Works with endocrine system to maintain homeostasis and provide quick responses
  • Aim of nervous system is to maintain homeostasis and provide fast responses
  • Monitors body's internal and external environments
  • Integrates sensory information and follows up with commands to effectors
  • Coordinates voluntary and involuntary responses of other organ systems

Nervous System Organization

  • Consists of central nervous system (CNS) and peripheral nervous system (PNS)
  • CNS includes the brain and spinal cord which receive and process sensory information and send signals to effectors
  • PNS is all neural tissue outside the CNS, contains afferent and efferent divisions, for sensory receptors and effectors

Anatomical Divisions of Nervous System

  • Central Nervous System (CNS):
    • Brain and spinal cord
    • Integrates, processes and coordinates sensory input and motor commands
  • Peripheral Nervous System (PNS):
    • Includes all neural tissues outside the CNS
    • Carries information between CNS and the rest of the body (body to CNS and CNS to effectors)

Functional Divisions of PNS

  • Afferent Division:
    • Carries sensory information from sensory receptors to the CNS
    • Receptors are sensory structures that detect environment changes or specific stimuli. This is also known as sensory neurons.
  • Efferent Division:
    • Carries motor commands from the CNS to effectors (muscles and glands). This is also known as motor neurons.
    • Target organs respond by executing a specific function

Further Divisions of Nervous System

  • Somatic Nervous System:

    • Controls skeletal muscle contractions (voluntary)

  • Autonomic Nervous System:

    • Controls involuntary actions
    • Regulates smooth muscles, cardiac muscles and glandular secretions
    • Further divided into sympathetic (fight-or-flight) and parasympathetic (rest-or-digest) divisions.

Nervous System Cells

  • Contains two types of cells: neurons and neuroglia (glial cells)
  • Neurons are the basic functional units, sending and receiving signals.
  • Neuroglia cells support and protect neurons, they don't directly send or receive signals.

Neuron Structure

  • Cell body (soma):
    • Large round nucleus, prominent nucleolus
    • No centrioles; neurons cannot divide or regenerate
  • Axon hillock:
    • Thickened region near axon
    • Starting point for action potential generation
  • Dendrites:
    • Many, short, branched extensions
    • Sensitive to stimulation
  • Axon:
    • Single, long extension
    • Transmits electrical signals

Neuron Classification

  • Sensory neurons (afferent):

    • Carry information from sensory receptors to the CNS
    • Two types:
      • Somatic sensory neurons monitor external environment
      • Visceral sensory neurons monitor internal environment

  • Motor neurons (efferent):

    • Carry instructions from the CNS to effectors
    • Two types:
      • Somatic motor neurons innervate skeletal muscles
      • Visceral motor neurons innervate cardiac, smooth muscles, and glands.

  • Interneurons (bipolar):

    • Located in brain and spinal cord
    • Connect sensory and motor neurons
    • Involved in information distribution, motor coordination, memory, planning and learning.

Neuroglia (Glial Cells)

  • Make up half the volume of CNS
  • Supporting cells in nervous system
  • Found in CNS and PNS
  • Astrocytes, oligodendrocytes, microglia, ependymal cells, satellite cell, and Schwann cells are types of neuroglia.
    • Astrocytes form structural framework and support blood-brain barrier.
    • Oligodendrocytes produce myelin sheaths in CNS.
    • Microglia are phagocytic cells that clean up cellular debris.
    • Ependymal cells line fluid-filled passageways and secrete cerebrospinal fluid.
    • Satellite cells support neuron cell bodies in PNS
    • Schwann cells form myelin sheaths around peripheral axons.
  • Myelination speeds up nerve impulse transmission.

Nerve Conduction

  • Irritability: Ability to respond to a stimulus and generate a nerve impulse
  • Conductivity: Ability to transmit the impulse to other neurons, muscles, or glands
  • Resting membrane potential: (-70mV) is the difference in electrical charge across the plasma membrane of a neuron when it is not transmitting a signal.
  • Action potential: nerve impulse; inside of neuron membrane becomes positively charged; generated by opening and closing of gated sodium and potassium channels.
  • Propagation: spreading of an action potential along an axon. Continuous vs. saltatory (in myelinated axons)

Synapse

  • Site of neuron-to-neuron or neuron-to-effector communication
  • Presynaptic neuron releases neurotransmitters into synaptic cleft
  • Neurotransmitters bind to receptors on postsynaptic neuron/effector

Transmission of Action Potential at Synapse:

  • Action potential arrives at axon terminal of presynaptic neuron.
  • Calcium channels open, allowing calcium ions to enter the neuron.
  • Neurotransmitters are released into the synaptic cleft.
  • Neurotransmitters bind to receptors on the postsynaptic neuron. This triggers a response in the postsynaptic neuron.
  • Neurotransmitters are broken down or removed from the synaptic cleft.

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Description

The nervous system works with the endocrine system to maintain homeostasis. It consists of the central nervous system (CNS) and peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS includes all neural tissues outside the CNS.

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