Nervous System Functions and Divisions

Questions and Answers

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

Transmit sensory information to the CNS

Produce cerebrospinal fluid

Form a myelin sheath around axons (correct)

Remove debris and protect against bacteria

Which type of neuron has two processes: one dendrite and one axon?

Bipolar neurons (correct)

Multipolar neurons

Pseudo-unipolar neurons

Unipolar neurons

What is the role of the blood-brain barrier?

Protect neurons from toxic substances in the blood (correct)

Stimulate the division of neuroglia cells

Enhance the conductivity of action potentials

Allow all substances to freely enter the brain

In which phase of neural signaling does the CNS determine an appropriate response?

Integration Signup and view all the answers

How does myelination affect action potentials in neurons?

Increases speed through salutatory conduction Signup and view all the answers

What primarily characterizes gray matter in the central nervous system (CNS)?

Groups of neuron cell bodies and their dendrites Signup and view all the answers

What is the main role of the sodium-potassium pump in maintaining resting membrane potential?

To maintain higher Na+ concentration outside the cell Signup and view all the answers

What event occurs during depolarization of a neuron?

Na+ ions quickly diffuse into the cell. Signup and view all the answers

Which statement best describes saltatory conduction?

Action potentials skip from one node of Ranvier to the next. Signup and view all the answers

Which channel opens in response to a specific change in membrane potential?

Voltage gated channels Signup and view all the answers

What is the all-or-none principle in action potentials?

Once a threshold is reached, an action potential occurs. Signup and view all the answers

What separates the presynaptic and postsynaptic membranes at a synapse?

Synaptic cleft Signup and view all the answers

Which of the following best describes white matter in the central nervous system?

Composed mainly of myelinated axons Signup and view all the answers

What is the role of neurotransmitters in the nervous system?

They serve as chemical messengers between neurons. Signup and view all the answers

What characterizes a converging neuronal pathway?

Multiple neurons synapse with the same neuron. Signup and view all the answers

Which type of summation allows local potentials from different locations on the postsynaptic neuron?

Spatial summation Signup and view all the answers

What is the primary function of the spinal cord in relation to the brain?

It transmits information to and from the brain. Signup and view all the answers

Which part of the spinal cord is associated with ascending tracts?

Lateral columns Signup and view all the answers

How is the gray matter of the spinal cord structurally represented?

Shaped like the letter H Signup and view all the answers

What are reflexes primarily characterized by?

Involuntary reactions to stimuli. Signup and view all the answers

What does the cauda equina resemble?

A horse's tail Signup and view all the answers

Study Notes

Functions of the Nervous System (CRIME)

Controlling Muscles and Glands: Regulates voluntary and involuntary responses.
Receiving Sensory Input: Gathers information from sensory organs.
Integrating Information: Processes sensory data to make decisions.
Maintaining Homeostasis: Regulates internal environment to ensure stability.
Establishing and Maintaining Mental Activity: Supports cognitive functions such as thinking and memory.

Divisions of the Nervous System

Central Nervous System (CNS): Comprises the brain and spinal cord.
Peripheral Nervous System (PNS): Includes nerves and ganglia.
- Sensory Division: Afferent pathway transmitting signals from sensory receptors to the CNS.
  - Sensory Neurons: Carry action potentials from peripheral stimuli to the CNS.
    - Somatic Sensory Fibers: Relay information from skin, muscles, and joints.
    - Visceral Sensory Fibers: Transmit impulses from internal organs.
- Motor Division: Efferent pathway conducting signals from the CNS to effectors.
  - Motor Neurons: Relay action potentials from the CNS to peripheral targets.
    - Somatic Motor Nervous System: Controls skeletal muscle movements (voluntary).
    - Autonomic Motor Nervous System: Regulates cardiac and smooth muscles, and glands (involuntary).
      - Sympathetic Division: Mediates 'fight or flight' responses.
      - Parasympathetic Division: Facilitates 'rest and digest' activities.
    - Enteric Nervous System: Controls digestive tract functions through its own sensory and motor neurons.

Cells of the Nervous System

Neurons: Main signaling cells responsible for receiving and transmitting signals.
- Cell Body: Contains the nucleus, essential for gene expression.
- Dendrites: Extensions that receive signals from other neurons.
- Axon: Long projection conducting action potentials; varies by neuron type.
  - Sensory Neurons: Conduct signals toward the CNS.
  - Motor Neurons: Conduct signals away from the CNS.
- Axon Hillock: Junction where the axon exits the cell body.
- Nissl Bodies: Rough endoplasmic reticulum within the neuron cell body.
- Schwann Cells: Form myelin sheaths that speed up impulse transmission.
- Collateral Axons: Branches off the main axon.

Types of Neurons

Multipolar Neurons: Characterized by many dendrites and a single axon.
Bipolar Neurons: Have one dendrite and one axon.
Pseudo-unipolar Neurons: Comprise a single process that splits into two branches.

Neuroglia (Glial Cells)

Non-neuronal support cells that outnumber neurons and can divide.
- Astrocytes: Provide structural support and regulate environment; contribute to the blood-brain barrier.
- Ependymal Cells: Produce and circulate cerebrospinal fluid.
- Microglia: Serve as immune cells; remove pathogens and debris.
- Oligodendrocytes (CNS) and Schwann Cells (PNS): Form insulating myelin sheaths around axons.

Neural Signaling Process

Reception: Stimuli detected by sensory receptors.
Transmission: Sensory neurons convey information to the CNS.
Integration: CNS interprets incoming data to decide on responses.
Transmission: CNS sends signals to motor neurons.
Response: Effectors (muscles/glands) react based on motor neuron signals.

Myelin Sheaths

Specialized insulation that enhances signal conduction.
Unmyelinated Axons: Slow signal transmission as impulses travel along the entire axon.
Myelinated Axons: Rapid transmission through saltatory conduction between nodes.
Nodes of Ranvier: Gaps in myelin enabling ion exchange, crucial for action potential propagation.

Organization of Nervous Tissue

Gray Matter: Composed of neuron cell bodies and dendrites; lacks myelin.
- In the CNS:
  - Cortex: Gray matter on the brain's surface.
  - Nuclei: Groups of gray matter located deeper in the brain.
- In the PNS:
  - Ganglion: Cluster of neuron cell bodies.
White Matter: Consists of bundles of parallel axons and myelin sheaths.
- In the CNS:
  - Nerve tracts: Pathways for conduction, propagating action potentials within the CNS.
- In the PNS:
  - Nerves: Bundles of axons encased in connective tissue sheaths.

Electrical Signals and Neural Pathways

Resting Membrane Potential (RMP): Represents an uneven distribution of charge across the cell membrane.
- Higher potassium (K+) concentration inside, sodium (Na+) concentration outside.
- Cell membrane is more permeable to K+ than Na+.
Channel Types:
- Leak channels: Always open.
- Gated channels: Closed until a specific signal opens them.
- Chemically gated channels: Activated by neurotransmitters.
- Voltage-gated channels: Activated by changes in membrane potential.
Sodium-Potassium Pump: Essential for maintaining higher Na+ concentration outside and K+ inside the cell.

Action Potentials

Excitable Cells: Their RMP alters in reaction to stimuli triggering gated ion channels.
Depolarization: Causes the cell membrane's interior to become positive.
Threshold Value: Critical point required to generate an action potential.
Action Potential: Sequence of depolarization followed by repolarization.
Hyperpolarization: Membrane charge becomes more negative than RMP.
All-or-None Principle: An action potential occurs fully if the threshold is met; no partial action potentials.
Conduction Types:
- Continuous conduction: Action potential travels along the entire axon membrane.
- Saltatory conduction: Action potentials jump between nodes of Ranvier.

The Synapse

Synapse: Junction between the axon of one neuron and another neuron or effector cell.
- Presynaptic Terminal: End of the axon.
- Postsynaptic Membrane: Membrane of the receiving neuron or effector.
- Synaptic Cleft: Gap separating the presynaptic and postsynaptic membranes.
Neurotransmitters: Chemical messengers released into the synaptic cleft.
Synaptic Vesicles: Storage for neurotransmitters.
Hyperpolarization in Postsynaptic Cell: Results in a more negative interior.

Reflexes

Reflex: Involuntary response to stimuli from the peripheral nervous system to the CNS.
Reflex Arc: Pathway through which reflexes occur, involving:
- Sensory receptor.
- Sensory neuron.
- Interneurons.
- Motor neuron.
- Effector organ (muscle or glands).

Neuronal Pathways

Converging Pathway: Multiple neurons synapse with a single neuron.
Diverging Pathway: One neuron's axon splits to synapse with multiple neurons.
Summation: Process integrating various sub-threshold local potentials, helping to reach action potential threshold.
- Spatial Summation: Local potentials from different locations on the postsynaptic neuron.
- Temporal Summation: Local potentials overlapping over time.

Spinal Cord

Extends from the foramen magnum to the 2nd lumbar vertebra.
Serves as a two-way conduction pathway to and from the brain.
Cauda Equina: Bundle of spinal nerves resembling a horse's tail at the inferior end.

Functions of the Spinal Cord

Transmits information to and from the brain.
Controls various reflex activities of the body.

White Matter of the Spinal Cord

Consist of:
- Dorsal (posterior) Columns.
- Ventral (anterior) Columns.
- Lateral Columns.
  - Ascending tracts: Conduct action potentials towards the brain.
  - Descending tracts: Conduct action potentials away from the brain.

Gray Matter of the Spinal Cord

Shaped like the letter "H" and consists of:
- Posterior Horns.
- Anterior Horns.
- Small Lateral Horns.

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Description

Explore the essential functions and divisions of the nervous system in this quiz. Delve into how the central and peripheral nervous systems operate, including the roles of sensory neurons. Test your knowledge on muscle control, sensory input, and mental processes.