Class Overview

• Spring fling on campus today, free food, music, games from 11am to 1pm.
• Cranial nerve assignment is due tomorrow night. Focus of today's class is on chapter 14 - visceral reflexes.
• Plan to discuss chapter 15 in preparation for upcoming lab activity on neural testing next week.

Visceral Reflexes

• Definitions:
  • Visceral Reflexes: Reflexes that involve the internal organs and typically involve cranial nerves.
  • Cranial Nerves: Include nerves that control sensory and motor functions, especially those pertaining to the head and neck.

Direct Light Reflex

• Example: Test for reaction when light shines into the eye.
• Expected Response: Constriction of the pupil (both the eye exposed to light and the opposite eye due to consensual reflex).
  • Cranial Nerves Involved:
  • Cranial Nerve II (Optic Nerve): Carries sensory information from the eye.
  • Cranial Nerve III (Oculomotor Nerve): Controls pupil constriction.
• Stimulus: Light striking rods and cones in the retina (photoreceptors).

Consensual Light Reflex

• Function: When light is shined in one eye, the opposite pupil constricts slightly delayed.
• Terms:
  • Ipsilateral: Same side response.
  • Contralateral: Opposite side response.

Other Reflexes

Corneal Reflex

• Stimulus: Contact with the cornea using cotton.
• Cranial Nerves Involved:
  • Cranial Nerve V (Trigeminal Nerve): Sensory; detects sensation.
  • Cranial Nerve VII (Facial Nerve): Motor; controls eyelid closing and facial expressions.

Important Cranial Nerves

1. Cranial Nerve II: Vision.
2. Cranial Nerve III: Pupillary reflex (constriction).
3. Cranial Nerve V: Sensation from face, motor to muscles of mastication.
4. Cranial Nerve VII: Controls muscles of facial expression.
5. Cranial Nerve VIII: Auditory (hearing and balance).
6. Cranial Nerve IX: Swallowing and taste from posterior tongue.
7. Cranial Nerve X: Autonomic functions of heart and digestive tract.

Pathways in Sensory Processing

• Types of Sensory Neurons:
  • First Order Neuron: Delivers sensations to the CNS; cell body in dorsal root ganglion.
  • Second Order Neuron: Interneuron in brain/sub-brain areas; links first order neuron to the third order neuron, often decussates (crosses over).
  • Third Order Neuron: Delivers sensory info to the cortex for perception.

Major Sensory Pathways

• Spinothalamic Pathway:

  • Anterior Spinothalamic Tract: Carries crude touch and pressure.
  • Lateral Spinothalamic Tract: Carries pain and temperature sensations.

• Posterior Column Pathway (Dorsal Column Medial Lemniscus Pathway):

  • Carries fine touch, vibration, and proprioception (conscious awareness of one's own body).

• Spinocerebellar Pathway:

  • Carries proprioception but does not go to the thalamus (unconscious proprioception).

Sensory Receptors

• Exteroceptors: Detect external stimuli (touch, pain).
• Interoceptors: Detect internal environment (blood pressure, heart rate).
• Proprioceptors: Detect body position and movements.

Cerebral Cortex Functional Areas

• Precentral Gyrus: Primary motor cortex; involved in voluntary movement control.
• Postcentral Gyrus: Primary somatosensory cortex; receives and processes sensory information from the body.

Lab Preparations

• Upcoming Lab on Neural Testing: Involves reflex assessments (deep tendon reflexes, two-point discrimination, Romberg test) and understanding of essential neural pathways.
  • Deep Tendon Reflexes: Assess spinal cord reflex arc.
  • Two-Point Discrimination: Measures sensory receptor density in various skin areas.
  • Romberg Test: Evaluates balance and proprioception.

Review for Final Exam

• The final exam will be online (May 7 - May 8).
• Review session scheduled before the exam for any last-minute questions.