The Impact of Screen Time on Mental Health

General Overview

• The central nervous system (CNS) is comprised of the brain and spinal cord.
• The peripheral nervous system (PNS) comprises the nerves that connect the CNS to the rest of the body.
• The PNS is categorized into sensory (afferent) and motor (efferent) components.
• The motor component is further divided into somatic (voluntary) and autonomic (involuntary) parts.
• The autonomic nervous system (ANS) is further divided into sympathetic and parasympathetic components.

Cranial Nerves

• There are 12 pairs of cranial nerves.
• Cranial nerves I and II originate from the brain, while the remaining 10 originate from the brainstem.
• Some cranial nerves have both sensory and motor functions.

Spinal Nerves

• There are 31 pairs of spinal nerves.
• Each spinal nerve has a dorsal (sensory) root and a ventral (motor) root.
• Spinal nerves exit the vertebral column via intervertebral foramina.
• Spinal nerves are categorized into cervical, thoracic, lumbar, sacral, and coccygeal regions.
• Spinal nerves form plexuses which are networks of nerves within the body.

Organization & Function of the Brain

• Cerebrum:
  • Divided into lobes: frontal, parietal, temporal, occipital.
  • Important for higher-order functions like language.
  • Contains the primary motor cortex.
• Diencephalon:
  • Contains the thalamus and hypothalamus, which are key relay centers for sensory information and hormone regulation respectively.
• Brainstem:
  • Composed of the midbrain, pons, and medulla oblongata.
  • Crucial for regulating vital functions like breathing and heart rate.
• Cerebellum:
  • Located dorsal to the brainstem.
  • Responsible for motor coordination, balance, and posture.

Peripheral Nervous System (PNS)

• The PNS is comprised of the cranial nerves and spinal nerves.
• Somatic Nervous System: Controls voluntary movements.
• Autonomic Nervous System (ANS): Regulates involuntary functions such as heart rate, digestion, and temperature.
  • Sympathetic nervous system: Prepares the body for stress or “fight or flight”.
  • Parasympathetic nervous system: Calms the body and conserves energy.

Cranial Nerve Examples

• Olfactory nerve (I):
  • Sensory; responsible for the sense of smell.
• Optic nerve (II):
  • Sensory; responsible for vision.
• Oculomotor nerve (III):
  • Motor; controls most eye movements, including pupil constriction and lens accommodation.

Basic Circuitry

• Reflex arcs: Allow for rapid, involuntary responses to stimuli.
• Cranial and spinal nerve tracts and pathways: Carry signals between the CNS and PNS for motor and sensory information.