Control of Self and Spinal Arc Reflex

• Spinal Reflex: Involuntary muscle response to a stimulus that bypasses the brain; crucial for survival.
  • Automatic: Operates without higher brain involvement, maintaining homeostasis.
  • Types: Can be somatic (skeletal muscles) or autonomic (smooth muscles).
  • Characteristics: Stereotyped, immediate, rapid, predictable, unlearned.

Components of the Reflex Arc

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

  • Sensory Receptor: Detects a stimulus.
  • Sensory Neuron: Transmits information to the spinal cord.
  • Interneuron: Processes the signal in the spinal cord (not involved in monosynaptic reflexes).
  • Motor Neuron: Carries the signal to the effector.
  • Effector Organ: Muscle or gland that responds.

• Types of Reflexes:

  • Monosynaptic Reflex: Simplest reflex path (e.g., stretch reflex).
  • Only one synapse between sensory and motor neuron.
  • Polysynaptic Reflex: Complex with interneurons (e.g., Golgi tendon reflex).
  • Multiple synapses involving more than one neuron.

Neuron Structure and Classification

• Function of the Nervous System:

  • Control of voluntary and involuntary actions.
  • Coordination of sensory information for response.

• Neurons:

  • Parts: Dendrites, cell body, axon (both central and peripheral processes).
  • Types:
  • Sensory Neurons: Transmit sensory information.
  • Motor Neurons: Carry signals to muscles.
  • Interneurons: Process information within the CNS.

Neuroglial Cells

• Functions and Locations of neuroglial cells in CNS and PNS:
  • Support and insulation for neurons.
  • Maintain homeostasis and nutrient supply.

Resting Membrane Potential (RMP)

• Definition: The voltage difference across a neuron's membrane when not actively transmitting a signal.

  • RMP typically around -70 mV.

• Charges on Sides:

  • Inside is more negative compared to outside due to distribution of ions (Na+, K+).

• Changes During Stimulation:

  • Voltage changes, leading to action potential generation if the threshold is reached.

Synapse Structure and Function

• Synapse: The junction between two neurons where neurotransmission occurs.

  • Components:
  • Pre-synaptic terminal, synaptic cleft, and post-synaptic membrane.

• Action at Synapse:

  • Release of neurotransmitters to propagate the signal to the next neuron or effector.

Difference Between Reflex and Reaction

• Reflex: Automatic and faster response, does not require direct brain processing.

  • E.g., patellar reflex.

• Reaction: Voluntary response requiring cognitive processing.

  • E.g., catching a ball.
  • Generally slower than reflex actions.

Learning Objectives

• Understanding the Nervous System:
  • Function classification (CNS vs. PNS).
  • Characteristics of somatic vs autonomic systems.
  • Analyze the structure of neurons and their functions.