Nervous System Structure and Function: Study Guide for Units 14 & 15

Learning Objectives: Nervous System (Units 14 & 15)

This study guide covers the structure and function of the nervous system, focusing on neural pathways, reaction times, neuroanatomy, and histology. The objectives and activities are designed to help students understand the organization and physiology of the central and peripheral nervous systems.

Neural Pathways and Response

• Neural Pathway: A sequence of neurons that transmit signals from sensory input to motor output, enabling responses to stimuli.

• Types of Stimuli: Visual, auditory, and tactile stimuli are processed by specific neural pathways.

• Reaction Time: The time taken for a stimulus to elicit a response, which can be measured and compared across different types of stimuli.

• Example: Measuring the time it takes to respond to a light versus a sound.

Motor Neuron Anatomy and Function

• Motor Neuron: A nerve cell that transmits impulses from the central nervous system to muscles or glands.

• Key Components: Dendrites, cell body (soma), axon, axon terminals, myelin sheath, and nodes of Ranvier.

• Function: Conducts electrical impulses to initiate muscle contraction or glandular secretion.

• Diagram: Students should be able to label these parts on an anatomical model or chart.

Myelin and Electrical Impulse Conduction

• Myelin Sheath: A fatty layer that insulates axons, increasing the speed of electrical impulse conduction.

• Nodes of Ranvier: Gaps in the myelin sheath where action potentials are regenerated, enabling saltatory conduction.

• Significance: Myelinated fibers conduct impulses faster than unmyelinated fibers.

Chemical Synapse and Neurotransmission

• Chemical Synapse: A junction where neurotransmitters are released from one neuron to stimulate the next cell.

• Key Steps:

  1. Action potential arrives at axon terminal.

  2. Neurotransmitter is released into the synaptic cleft.

  3. Neurotransmitter binds to receptors on the postsynaptic cell, initiating a response.

• Example: Acetylcholine release at the neuromuscular junction.

Neuroglia and Nervous Tissue Organization

• Neuroglia (Glial Cells): Supportive cells in the nervous system, including astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS; Schwann cells and satellite cells in the PNS.

• Functions: Provide structural support, insulation, and metabolic support to neurons.

• Example: Oligodendrocytes form myelin in the CNS; Schwann cells form myelin in the PNS.

Cross Section of a Nerve

• Connective Tissue Layers:

  • Endoneurium: Surrounds individual axons.

  • Perineurium: Bundles groups of axons into fascicles.

  • Epineurium: Encloses the entire nerve.

• Other Structures: Blood vessels, myelinated and unmyelinated fibers.

Brain Anatomy and Function

• Major Brain Regions:

  • Cerebrum: Responsible for higher brain functions such as thought, memory, and voluntary movement.

  • Cerebellum: Coordinates movement and balance.

  • Diencephalon: Contains the thalamus and hypothalamus, involved in sensory relay and homeostasis.

  • Brainstem: Includes the midbrain, pons, and medulla oblongata; controls vital functions.

• Meninges: Three protective layers (dura mater, arachnoid mater, pia mater) surrounding the brain and spinal cord.

• Ventricles: Cavities within the brain that produce and circulate cerebrospinal fluid (CSF).

Spinal Cord Structure

• Gray Matter: Contains neuron cell bodies; forms the central "H" shape in cross-section.

• White Matter: Composed of myelinated axons; surrounds the gray matter.

• Spinal Nerves: Emerge from the spinal cord and contain both sensory and motor fibers.

Reflex Arcs

• Reflex Arc: The neural pathway involved in a reflex action.

• Components: Receptor, sensory neuron, integration center, motor neuron, effector.

• Example: Knee-jerk (patellar) reflex.

Sheep Brain Dissection

• Purpose: To identify and describe the major structures of the brain in a hands-on laboratory setting.

• Structures to Identify: Cerebrum, cerebellum, brainstem, ventricles, cranial nerves, and internal features in sagittal and coronal sections.

Histology of Nervous Tissue

• Motor Neuron: Large cell body with prominent nucleus and nucleolus, dendrites, and a long axon.

• Peripheral Nerve: Bundles of axons with myelin sheaths, visible connective tissue layers.

• Mammalian Nerve Fibers: Teased preparations show individual myelinated and unmyelinated fibers.

Lab Manual Activities

• Unit 14 Activities: 1, 2, 3, 4

• Unit 15 Activities: 1, 2, 3, 4, 5

Materials and References

• Meter stick, blindfold, motor neuron model, anatomical charts, histology slides, brain model

• Reflex hammer, sheep brain, dissection pan and tools, safety glasses

• References: A Brief Atlas of the Human Body, Vimeo: Sheep Brain Dissection

Table: Major Brain Regions and Functions

Region	Main Function
Cerebrum	Conscious thought, memory, voluntary movement
Cerebellum	Coordination of movement, balance
Diencephalon	Sensory relay, homeostasis
Brainstem	Vital functions (breathing, heart rate)

Key Equations

• Reaction Time Calculation:

$\text{Reaction Time} = \frac{\text{Distance Fallen}}{\text{Acceleration due to Gravity}}$

Additional info: The above equation is a simplified form; actual reaction time calculations may require more detailed kinematic equations depending on the experimental setup.