Exam Notes

Smooth Muscle Physiology

• Takes longer to initiate contraction and increases contractile force more slowly than skeletal muscle.
• Holds tone longer with less energy.
• Regulates contraction/relaxation at the myosin level, not troponin-actin.
• Single-unit smooth muscle exhibits phasic/rhythmic contractions (e.g., peristalsis) and has higher plasticity.
• Contracts involuntarily; hormones and mechanical stretch can trigger contraction.

Neuron Classification

• Structural Categories:
  • Unipolar: Somatic.
  • Bipolar: Special.
  • Multipolar.
• Physiology:
  • Sensory (afferent) → interneuron → motor (efferent).

Neuroglial Cells

• Central Nervous System:
  • Astrocytes: Creates compartment in the central nervous system
  • Ependyma: Lines fluid-filled cavities of the brain or spinal cord.
  • Microglia: Destroys bad product.
  • Oligodendrocytes: Creates myelin sheaths.
• Peripheral Nervous System:
  • Satellite cells.
  • Schwann cells.

Cerebrospinal Fluid (CSF)

• Functions: Cushioning, nutrient/waste transport.
• Composition: Passive filtration of plasma + active transport of ultrafiltrate into ventricles.
• Production: Choroid plexuses (with ependymal cells) in ventricles.
• Circulation: Subarachnoid space.
• Absorption: Arachnoid granulations.

CSF Production - Choroid Plexus

• Blood-CSF barrier.
  • Fenestrated endothelium (of pia mater capillaries).
  • Basement membrane.
  • One layer of ependymal cells (choroid epithelial cells) with tight junctions.
  • Passive filtration & active transport.

Blood-Brain Barrier (BBB) vs. Blood-CSF Barrier

• BBB (Cerebral Vasculature):
  • Capillary endothelium (simple squamous epithelium with tight junctions).
  • Basement membrane.
  • Pericytes (smooth muscle cells).
  • Astrocytes (neuroglial cells).
  • Unidirectional.
• Blood-CSF Barrier (Choroid Plexus):
  • Bidirectional.