Central Nervous System Quiz

Nervous System Organization

• The nervous system is responsible for organizing and controlling the body's responses.
• It gathers and processes information, resulting in an appropriate response.
• The nervous system has two main parts: central nervous system (CNS) and peripheral nervous system (PNS).

CNS Objectives

• List the general functions of the nervous system.
• Explain the structural and functional classification of the nervous system.
• Define the central and peripheral nervous systems, including their main parts.
• Describe the structure of a neuron.
• Describe the functional and structural classification of neurons..
• Describe the composition of grey and white matter.

Master & Fast Control & Communication System

• The nervous system processes and responds to signals to maintain homeostasis.
• Stimuli are gathered by sensory receptors and the information is interpreted.
• The interpretation results in an output signal which creates a response via effectors.
• This response often affects muscles or glands.

Functions of the Nervous System

• Sensory input: Gathering information from inside and outside the body. Changes are called stimuli.
• Integration: Processing and interpreting sensory input and deciding upon an action.
• Motor output: Producing a response via muscles or glands.

Structural Classification of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord. Involved in processing and coordinating information.
• Peripheral Nervous System (PNS): Includes nerves, cranial nerves, and spinal nerves. These nerves act as communication lines to and from the CNS.
• Nerves are structures composing bundles of axons. Cranial and spinal nerves are examples.

Organization (Divisions) of the Nervous System

• Sensory (afferent) division: transmits impulses from sensors. Includes somatic and visceral sensory fibers.
• Motor (efferent) division: transmits impulses from CNS to effectors. Includes somatic and autonomic nervous system.
• Somatic nervous system: voluntary control of skeletal muscles.
• Autonomic nervous system (ANS): involuntary control of visceral organs (internal organs). Includes sympathetic and parasympathetic divisions.
  • Sympathetic: mobilizes body systems during activity.
  • Parasympathetic: conserves energy.

Neuron Anatomy

• Neuron: a nerve cell, specialized cells transmitting messages.
• Cell body: contains the nucleus.
• Dendrites: extensions conducting impulses towards the cell body.
• Axons: extensions conducting impulses away from the cell body.
• Axon terminals (presynaptic terminals): branching ends of the axon, containing neurotransmitters.
• Neurotransmitters are chemical messengers, enabling signals between neurons.

Pre and postsynaptic cells

• Presynaptic cell: transmits signal.
• Postsynaptic cell: receives signal.
• Synapse: point of contact between two cells.
• Synaptic cleft: gap between neurons.

Axons and Nerve Impulses

• Axons end in axonal terminals.
• Axonal terminals contain neurotransmitter vesicles.
• The next neuron is separated by a synaptic cleft.
• Synapse is the junction between adjacent nerves.

Nerve Fiber Coverings- PNS

• Schwann cells produce myelin sheaths, insulating material around axons.
• Nodes of Ranvier: gaps in myelin sheath along the axon.
• Neurilemma is a protective covering around axons in the PNS.

Neuron Classification

• Sensory neurons: afferent neurons transmit impulses from receptors (to CNS).
• Interneurons: found within the CNS.
• Motor neurons: efferent neurons transmit impulses from CNS to effectors.

Neuron Classification (Examples/Location)

• Sensory neuron cell bodies are typically located outside the CNS (peripheral).
• Cell bodies found in a bundle are called ganglia.
• Motor and interneuron cell bodies are found in the CNS (brain & spinal cord).

Peripheral and Central Nervous System

• Peripheral nervous system: carries signals to the CNS, carries signals from the CNS.
• Central nervous system: processes signals and coordinates responses.

Neuron Cell Body & Fibers (CNS v PNS)

• CNS: Nuclei
• PNS: Ganglia
• Bundles of fibers (CNS): Tracts
• Bundles of fibers (PNS): Nerves

Structural Classification of Neurons

• Multipolar neurons: many extensions from the cell body (common in CNS).
• Bipolar neurons: one axon and one dendrite (rare, found in special sensory organs).
• Unipolar neurons: one axon from the cell body (mainly sensory, in PNS).

White Matter vs Gray Matter

• White matter: myelinated fibers / axons
• Gray matter: neuron cell bodies/ axons not covered.

Functional Properties of Neurons

• Irritability: ability to respond to stimuli.
• Conductivity: ability to transmit impulses across the membrane.
• Polarization: membrane at rest, has fewer positive ions inside than outside.

Objectives - Additional Details

• Describe nerve impulse generation and conduction between neurons
• Define reflex arc and its components with examples.

Reflex Arc

• A reflex is a rapid, predictable, and involuntary response to a stimulus.
• Direct route from sensory neuron, to interneuron, to effector.
• It has 5 key components: receptor, sensory neuron, interneuron, motor neuron, and effector.

Reflex Arc: Components

• Component 1: Receptor. Receives input and transduces a stimulus into a nerve impulse.
• Component 2: Sensory neuron. Transmits the impulse towards the central nervous system.
• Component 3: Integration center. Processes the impulse (typically in the CNS)
• Component 4: Motor neuron. Carries the signal away from the integration center.
• Component 5: Effector. Receives the signal and creates an appropriate response.

Types of Reflexes

• Autonomic reflexes: involuntary control of smooth muscle, glands, and cardiac muscle (e.g., blood pressure regulation).
• Somatic reflexes: voluntary control of skeletal muscles (e.g., knee-jerk reflex).

Homeostasis and Negative Feedback

• The body maintains homeostasis through negative feedback mechanisms.
• Feedback loops involve these steps: Stimulus produces a change in a variable (like temp), Receptor detects change, Control center processes info, Effector response is initiated, Response feeds back to modify the stimulus.

Synapse: Transmission events

• Nerve impulses cross synaptic clefts via neurotransmitters.
• Step 1: Impulse reaches axon terminal.
• Step 2: Neurotransmitter release happens into the synaptic cleft where it binds to receptors.
• Step 3: Receptor binding causes a change and an action potential is initiated.
• Step 4: Impulse ceases via inactivation within the dendrite.

Synapse: Structures

• Synaptic end bulb: an enlarged swelling at the end of the axon, containing neurotransmitter-filled vesicles.
• Synaptic cleft: the narrow space separating the axon terminal from the postsynaptic neuron.
• Postsynaptic membrane: membrane on the postsynaptic cell, where receptors bind to initiate a new signal.

CNS Neuroglia (Support cells) - Various types

• Astrocytes: star-shaped cells, anchor neurons, form connections between capillaries & neurons, control chemical environment of the brain.
• Microglia: spider-like phagocytes, dispose of debris (dead cells/cellular wastes).
• Ependymal cells: line the cavities within the brain or spinal cord, to circulate cerebrospinal fluid.
• Oligodendrocytes: produce myelin sheaths around nerve fibers within the CNS.

PNS Support Cells

• Satellite cells: protect neuron cell bodies (in PNS).
• Schwann cells: form the myelin sheaths around nerve fibers in the PNS.

Nerve Fiber Coverings - CNS

• Many nerve fibres have myelin sheaths (produced by oligodendrocytes).
• No neurilemma.

Test your knowledge on the central nervous system with this quiz covering brain and spinal cord functions, neuron operations, and their roles in the nervous system. Understand the differences between central and peripheral components, synapse functions, and neuronal communication mechanisms.