Detailed Notes on The Brain and Cranial Nerves

Specific Learning Objectives

• Describe the peripheral nervous system (PNS) with reference to the somatic nervous system and the motor division of the autonomic nervous system.
• Describe the anatomy of the PNS, including peripheral ganglia, spinal and cranial nerves, and associated central nervous system (CNS) structures.
• Identify the main regions of the brain.
• Describe the functions of the brain.

Brain Regions in Development

• Three primary brain regions in the early embryo:
  • Forebrain
  • Midbrain
  • Hindbrain

Anatomy of the Brain

• The major structures of the brain include:
  • Forebrain
  • Cerebrum
  • Diencephalon
  • Midbrain
  • Hindbrain
  • Pons
  • Medulla oblongata
  • Cerebellum

Brainstem

• Function: Responsible for autonomic reflexes that maintain body homeostasis, cardiovascular and respiratory functions, and other reflex responses (e.g., hiccups, swallowing).
• Structure:
  • Medulla Oblongata
  • Regulates heart rate, force of contraction, and vessels' diameter.
  • Controls the rate and depth of breathing.
  • Pons
  • Bridges connections between the spinal cord and brain.
  • Contains longitudinal tracts and transverse tracts connecting cerebrum to cerebellum.
  • Functions as a sleep center and respiratory center.

Midbrain

• Function: Integrates visual, auditory, and tactile sensory input, initiating movements of the head and eyes in response to stimuli.
  • Controls:
  • Eye movements
  • Locomotion
  • Fine motor control
  • Posture and balance

Diencephalon

• Components:
  • Thalamus: Paired structure, sensory relay center, influences mood.
  • Hypothalamus:
  • Central controller of the endocrine system, connected to pituitary gland via the infundibulum.
  • Regulates autonomic and endocrine functions including:
    • Body temperature
    • Food and water intake
    • Emotions and sleep-wake cycles
    • Sexual development and behavior

Cerebrum

• Structure: Includes gyri (folds), sulci (grooves), and fissures (deep grooves).
• Cerebral Lobes:
  • Frontal Lobe:
  • Primary motor functions, planning, mood regulation, sense of smell.
  • Parietal Lobe: Receives and evaluates sensory information, excluding special senses.
  • Occipital Lobe: Integrates visual input.
  • Temporal Lobe: Evaluates smell and hearing input; involved in memory.
  • Insula: Evaluates taste information.

Grey and White Matter

• Grey Matter:
  • Contains cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia; found in the cortex of the brain and spinal cord, as well as deep nuclei.
• White Matter:
  • Composed of myelinated axons forming nerve tracts.

Limbic System

• Described as the ‘emotional brain’ influencing memory, motivation, emotion, and learning, while affecting the autonomic and endocrine systems.

Meninges and Ventricles

• Meninges: Protective layers for the brain and spinal cord.
• Ventricles: Four continuous ventricles lined with ependymal cells, producing cerebrospinal fluid (CSF) that cushions and bathes the brain and spinal cord.

Cerebrospinal Fluid (CSF)

• Function:
  • Provides protection, cushioning, and allows the brain to float within the cranial cavity.
  • Produced primarily by the choroid plexus, similar to blood serum but lacking most proteins.

Compendium Questions

1. What are the major parts of the brain?
2. Identify the main lobes, sulci, and gyri of the cerebrum.
3. What connects the two cerebral hemispheres?
4. Advantages of convolutions in the cerebrum?
5. Differences between white matter and grey matter?
6. Roles of the thalamus and hypothalamus?
7. Functions of the brainstem?
8. Identify the functional areas of the cerebrum.
9. Role of the cerebellum in processing sensory information.
10. Begin and end points of the spinal cord in adults.
11. Entry and exit points of sensory and motor nerve roots in the spinal cord.
12. Divisions of the ANS and their origins in the CNS.
13. Differences between somatic motor and autonomic motor neuron pathways.
14. What are ganglia?
15. Effects of each part of the ANS on the body.