Study sheet: Reflex Behaviors and Nervous System

📋 Course Outline

1. Nervous System Organization
2. Neurons and Glial Cells
3. Reflex Behaviors and Pathways

📖 1. Nervous System Organization

🔑 Key Concepts & Definitions

• Nervous system : a rapid communication system between organs, continuously connecting all organs through nerve fibers.

★ Must-know

• The encephalon contains:
  • the brain
  • the brainstem
  • the cerebellum

Further detail

• Nerves contain sensory fibers, motor fibers, or both, including 12 pairs of cranial nerves and 31 pairs of spinal nerves.

• The nerve centers are protected by three membranes called the meninges.

💡 Memory Hook

Centers → nerves → muscles or glands

📖 2. Neurons and Glial Cells

🔑 Key Concepts & Definitions

• Neuron : an excitable, stimulable, and information-conducting cell.

★ Must-know

• Dendrites receive and integrate information from other neurons or sensory receptors, and a myelinated axon sends the message toward another neuron, a muscle cell, or a glandular cell.

Further detail

• The human encephalon contains approximately 100 billion neurons, while glial cells are approximately 20 times more numerous than neurons.

• The neuron includes: dendrites, a cell body containing the nucleus, an axon, a myelin sheath with Schwann cells and nodes of Ranvier, terminal arborization ending at synapses

💡 Memory Hook

Neurons transmit information; glial cells protect and nourish them

📖 3. Reflex Behaviors and Pathways

🔑 Key Concepts & Definitions

• Reflex behavior : an innate, involuntary, and stereotyped movement that occurs in response to a given stimulus.
• Myotatic reflex : a postural reflex in which a muscle contracts in response to its stretching, helping a person remain standing or sitting without conscious thought.

★ Must-know

📌 A conditioned reflex follows learning, whereas an innate reflex occurs without prior learning.

Further detail

📌 A withdrawal reflex in response to pain is a medullary reflex because it involves the spinal cord rather than the encephalon.

💡 Memory Hook

Stimulus → nervous message → involuntary stereotyped movement

📊 Synthesis Tables

Comparison of Reflex Types

Reflex	Trigger or origin	Role	Nervous center involved
Innate reflex	Given stimulus	Involuntary, stereotyped response	Not specified generally
Conditioned reflex	Learning	Acquired response	Not specified
Myotatic reflex	Muscle stretching	Posture maintenance	Not specified
Withdrawal reflex	Pain	Withdrawal movement	Spinal cord