Lecture Notes on Nervous System and Sensory Physiology

Nervous System Overview

• Central Nervous System (CNS):

  • Composed of the brain and spinal cord.

• Peripheral Nervous System (PNS):

  • Consists of nerves outside the brain and spinal cord.

• Meninges:

  • Coverings of the brain and spinal cord.
  • Three layers: dura mater (outermost), arachnoid mater (middle), pia mater (innermost).

Cerebrospinal Fluid (CSF)

• Production:

  • Made in ventricles by the choroid plexus (specialized capillaries).

• Storage:

  • Located in the subarachnoid space.

• Drainage:

  • Drained by arachnoid granulations.

• Functions:

  • Shock absorber, nourishing neurons, and providing a stable environment.

Brain Structure and Function

• Major Parts of the Brain:

  • Cerebrum (largest part)
  • Diencephalon
  • Cerebellum (second largest part)
  • Brainstem

• Cerebrum:

  • Contains lobes (frontal, parietal, temporal, occipital) each with specific functions.
  • Frontal Lobe: Motor cortex, reasoning, and personality.
  • Parietal Lobe: Sensory processing.
  • Temporal Lobe: Auditory processing.
  • Occipital Lobe: Visual processing.

• Broca's Area:

  • Located in the frontal lobe, responsible for motor speech.

• Wernicke's Area:

  • Located between temporal and parietal lobes, responsible for language comprehension.

• Gray Matter vs. White Matter:

  • Gray matter: Cell bodies and dendrites.
  • White matter: Myelinated axons.

Reflexes and Spinal Cord

• Spinal Cord:

  • Extends from the foramen magnum to L2-L3 in adults.
  • Contains cervical and lumbar enlargements for nerve innervation to limbs.

• Reflex Arc:

  • Components: Receptor, sensory neuron, interneuron, motor neuron, effector.
  • Reflexes indicate an intact spinal cord.

Autonomic Nervous System (ANS)

• Sympathetic Nervous System:

  • Activates "fight or flight" responses, increases heart rate, dilates pupils, etc.

• Parasympathetic Nervous System:

  • "Rest and digest" functions, decreases heart rate, constricts pupils, etc.

Sensory Systems

• Types of Receptors:

  • Chemoreceptors, pain receptors, thermoreceptors, mechanoreceptors, photoreceptors.

• Adaptation:

  • Ability to ignore constant stimuli, e.g., smell, taste.

• Taste and Smell:

  • Taste involves five primary sensations: sweet, sour, salty, bitter, umami.
  • Smell is linked to the olfactory nerve and involves chemoreceptors.

• Vision:

  • Eye structure includes cornea, sclera, lens, and retina.
  • Retina contains rods (low light) and cones (color vision).

• Hearing and Balance:

  • Ear composed of external, middle, and internal parts.
  • Cochlea for hearing, vestibule and semicircular canals for balance.

Summary

• Review chapters 10, 11, and 12 thoroughly for upcoming exams.
• Understand the major systems, brain functions, and sensory pathways.
• Focus on the function and anatomy of the nervous and sensory systems as discussed in the lecture.