Recording-2025-03-11T09_54_49.474Z

Review Information

• Students encouraged to listen to last year's lecture recording uploaded for revision.

• Noted that the content is the same as the current year's lectures.

• Emphasis on using study guide questions instead of final slide questions.

Reflection on Teaching Methods

• Instructor values engaging teaching methods through analogies for better understanding of anatomy.

• Encourages student interaction, asking if students appreciate analogies as teaching tools.

Introduction to Reflexes

• Reflexes are a blend of anatomy and physiology.

• Important indicators of a healthy nervous system.

• Presence of reflexes at birth termed as neonatal reflexes; some reflexes disappear as a child develops due to myelination.

  • Example: Rooting reflex in newborns, where they turn their head toward tactile stimulation.

• Key reflexes discussed include:

  • Plantar reflex

  • Babinski reflex

Learning Objectives for Lecture

• Describe the five components of a reflex arc and their signal pathway.

• Understand muscle spindles' function and the stretch reflex pathway.

• Differentiate between stretch and tendon reflexes.

• Explore pupillary and vestibulo-ocular reflexes specifically related to vision.

Definition of Reflex

• Reflex: an inborn, automatic response of the human body to stimuli that ensures rapid reactions.

• Key roles:

  • Maintaining posture (e.g., stretch reflex to prevent knee buckling).

  • Regulating visceral activities (e.g., heart rate, digestion).

  • Providing safety mechanisms (e.g., pulling hand away from hot surface).

  • Reflexes can be modified through learning.

Classification of Reflexes

• Somatic Reflexes: Involving skeletal muscle (main focus).

• Visceral Reflexes: Involving smooth and cardiac muscles, and glands.

Reflex Arc Components

1. Receptor: Site where the stimulus acts.

2. Sensory Neuron: Transmits afferent impulses to the CNS.

3. Integration Center: Located in the spinal cord; may be monosynaptic or polysynaptic.

4. Motor Neuron: Sends efferent impulses to the effector organ.

5. Effector Organ: Typically skeletal muscle (for somatic reflexes).

Monosynaptic vs. Polysynaptic Reflexes

• Monosynaptic Reflex: One sensory neuron synapsing directly with a motor neuron (fast).

• Polysynaptic Reflex: Involves interneurons; takes longer due to multiple synapses.

Spinal Reflexes

• Mainly somatic reflexes mediated by the spinal cord without brain involvement.

• Reflex testing is critical for assessing CNS health; absence of reflexes may indicate pathology.

Key Types of Reflexes Covered

Stretch Reflex

• Mechanism allowing muscle contraction to prevent over-stretching.

• Involves muscle spindles providing information about muscle length.

• Reciprocal Inhibition: Agonist contracts while antagonist relaxes simultaneously.

Tendon Reflex

• Protects muscles from excessive stretching or tension through Golgi tendon organs.

• Initiates muscle relaxation when excessive tension is detected; opposite action to stretch reflex.

• Reciprocal Activation: Stimulates antagonist while relaxing the agonist.

Flexor Withdrawal Reflex

• Triggered by painful stimuli; involves automatic withdrawal from harm.

• Ipsilateral: Occurs on the same side of the body using polysynaptic pathways.

Crossed Extensor Reflex

• Balancing reflex that occurs simultaneously with the flexor reflex; involves the opposite limb.

• Essential for maintaining balance when one side withdraws.

Additional Reflexes

Pupillary Reflex

• Controls pupil diameter in response to light exposure; relevant for accommodating light levels.

Vestibulo-Ocular Reflex

• Maintains stable vision by moving eyes in opposite direction to head movement; critical for balance.

• Among the fastest reflexes in the body.

Newborn Reflexes

• Plantar Reflex: Tests spinal cord integrity.

• Babinski Sign: Indicates immature development in infants (toes dorsiflex instead of flex).

Upcoming Classes

• Next class will cover the musculoskeletal system.