Chapter 14: Brain and Cranial Nerves
Chapter Goals
- Understand brain organization, protection, and blood supply
- Compare brain areas and their functions
- Discuss brain functional organization
- Learn about cranial nerve structure and function
Importance
- Insight into brain contribution to homeostasis through sensory input, decision making, and motor activities.
Development of the Nervous System
- Neurulation: Occurs during the 3rd week of gestation
- Neural Plate: Thickens from ectoderm, folds inward forming a longitudinal groove
- Neural Folds: Raised edges beside the groove, eventually fuse to form the neural tube
Neural Tube Development
- Embryology: Neural tube forms brain and spinal cord
- Primary Vesicles: Prosencephalon (forebrain), Mesencephalon (midbrain), Rhombencephalon (hindbrain)
- Posterior end develops into the spinal cord
Protection of the Brain
- Cranial Bones and Meninges (Pia Mater, Arachnoid Mater, Dura Mater)
- Cover and protect CNS
- Enclose venous sinuses, contain cerebrospinal fluid (CSF)
- Dura Mater: Strong meninge, forms partitions to limit brain movement
- CSF: Supports and cushions the brain
Blood Supply and Brain Protection
- Brain utilizes 20% of body's oxygen
- Blood Brain Barrier (BBB): Selectively prevents substances from entering the brain
- Blood Flow: Via vertebral and carotid arteries, returns via jugular veins
Principal Parts of the Brain
- Cerebral Hemispheres
- Cerebral Cortex: Composed of gray matter, contains billions of neurons
- White Matter: Composed of axons connecting different parts of the brain
- Basal Nuclei: Regulate motor activities
- Diencephalon: Includes thalamus, hypothalamus, epithalamus
- Brain Stem: Midbrain, Pons, Medulla
- Cerebellum: Coordinates muscle activity and balance
Functions of Brain Areas
- Cerebral Cortex: Motor, sensory, and association areas
- Motor Areas: Voluntary movement, including Broca's area for speech
- Sensory Areas: Awareness of sensations
- Association Areas: Integrate complex functions like memory
- Limbic System: Emotion, memory, smell
- Hemispheric Lateralization: Functional differences between hemispheres, contralateral control
Brain Ventricles and CSF
- Ventricles: Chambers filled with CSF
- Choroid Plexuses: Produce CSF
- CSF circulates in central canal of spinal cord and subarachnoid space
Brainstem and Cranial Nerves
- Brainstem: Controls automatic behaviors, consists of midbrain, pons, and medulla oblongata
- Medulla Oblongata: Heart rate, respiration, reflexes
- Pons: Connects brain regions, regulates breathing
- Midbrain: Visual and auditory reflexes
- Cranial Nerves: 12 pairs with sensory, motor, and mixed functions
- Examples: Olfactory (smell), Optic (vision), Vagus (autonomic control)
Disorders and Aging
- Disorders: Tumors, ADHD, stroke, Alzheimer's disease
- Aging Effects: Neuron loss, decreased processing, sensory degeneration
This summary captures the key topics and details about the brain, its development, structure, protection, and associated cranial nerves. It also highlights the physiological functions and potential disorders affecting the brain.