Human Anatomy & Physiology I: The Brain & Autonomic Nervous System

HUMAN ANATOMY & PHYSIOLOGY I

Chapter 14 & 15: THE BRAIN & AUTONOMIC NERVOUS SYSTEM

Healthy Cells

  • Healthy cellular functions are fundamental to overall bodily operations, enabling normal anatomical and physiological processes.

Brain Development Stages

  • Optic Vesicle
  • Diencephalon
  • Metencephalon
  • Myelencephalon
  • Spinal Cord
  • Rhombencephalon
  • Mesencephalon
  • Prosencephalon
  • Timeline: 4-5 weeks gestation, development of the telencephalon from the neural plate.

Major Neuroanatomical Structures

  • Central Sulcus: Division between frontal and parietal lobes.
  • Gyri: Elevated ridges of the brain.
  • Lateral Sulcus: Separates the temporal lobe from frontal and parietal lobes.
  • Temporal Lobe: Associated with processing auditory information and memory.
  • Brainstem: Responsible for vital life functions such as breathing and heartbeat regulation.
  • Rostral and Caudal: Terms used to describe the direction in the brain; rostral is towards the front and caudal is towards the back.
  • Lateral View: Provided for anatomical reference.
  • Spinal Cord: Connects peripheral nervous system to brain.
  • Cerebrum: Largest part of the brain, associated with higher brain functions.
  • Cerebellum: Involved in motor control and coordination.

Vertical Brain Comparisons

  • Comparison of brain structures across species:
    • Crocodile Brain
    • Human Brain
    • Horse Brain

Lateral Brain: Left vs. Right Hemispheres

  • Cerebral Lateralization:
    • Left Hemisphere:
      • Functions include spoken and written language; analytical reasoning prevalent in sciences and mathematics (96% of right-handed, 70% of left-handed individuals).
      • Linear and fragmented processing.
    • Right Hemisphere:
      • Known as the representational hemisphere; perceives wholistic and integrated information.
      • Associated with creative functions such as insight, imagination, pattern recognition, arts, and musical abilities.
      • Males typically demonstrate more lateralization, which increases with age.

Sexual Dimorphism

  • Genotypic Sex: Genetic makeup.
  • Phenotypic Sex: Observable traits and behaviors.
  • Gender Identity: Personal sense of one's sex.
  • Brain Sex: Influenced by hormonal exposure during prenatal development.

Hypothalamic Functionality

  • Regulatory Functions:
    • Blood pressure, heart rate and rhythm, digestive processes, respiratory rates.
    • Bodily temperature regulation, hunger signals, and sleep cycles.

Endocrine Functions of the Hypothalamus

  • Produces releasing hormones that control anterior pituitary function, secreting antidiuretic hormone (ADH) and oxytocin.

Epithalamus

  • Dorsal aspect of the diencephalon, forming the roof of the third ventricle.
    • Pineal Gland: Secretes melatonin, regulating sleep-wake cycles.
    • Choroid Plexus: Structure responsible for the secretion of cerebrospinal fluid (CSF).

Midbrain Nuclei

  • Corporas Quadrigemina: Comprises superior colliculi (visual reflexes) and inferior colliculi (auditory relays).
  • Substantia Nigra: Linked with basal nuclei function.
  • Red Nucleus: Important for descending motor pathways.

Medulla Oblongata

  • Most inferior brainstem region, contains vital centers associated with autonomic functions.
    • Motor Centers: Control vomiting, hiccuping, swallowing, and respiration.
    • Pyramids: Where corticospinal tract neurons decussate (cross).

Reticular Formation

  • A network of gray matter through the brainstem, influencing alertness and consciousness.
    • Key in habituation; regulates response to stimuli through sensitivity filtering.

The Cerebellum

  • Essential for motor coordination and sensory input evaluation; plays roles in spatial perception and timekeeping functions.

The Cerebrum

  • Composed of various lobes (Frontal, Parietal, Occipital, and Temporal) each responsible for specialized functions such as movement, sensory integration, visual processing, and emotional regulation.
    • Cerebral White Matter: Contains projection, commissural, and association tracts vital for communication within the brain and between hemispheres.

The Limbic System

  • Involved in emotion, learning, and memory processing, with critical structures like the cingulate gyrus, hippocampus, and amygdala.

Visceral Reflex Arc

  • The ANS controls involuntary bodily functions through a reflex arc involving receptors, sensory neurons, interneurons in the CNS, and effector pathways.
    • Example: Baroreflex responses to changes in blood pressure.

Autonomic Nervous System (ANS)

  • Dual innervation system with sympathetic and parasympathetic divisions; maintains homeostasis and body regulation.
    • Sympathetic Division: Activates 'fight-or-flight' responses.
    • Parasympathetic Division: Responsible for 'rest-and-digest' activities.

EEG and Brain Waves

  • Waves categorized (Delta, Theta, Alpha, Beta, and Gamma) based on frequency and functions in sleep and alertness levels.
    • Delta Waves: Associated with deep sleep.
    • Theta Waves: Common in children and light sleep.
    • Alpha Waves: Indicate relaxed wakefulness.
    • Beta Waves: Present during alert and active thinking.
    • Gamma Waves: Linked to high-level cognitive functioning.

Sleep Cycles and Stages

  • Stages of Non-REM and REM sleep characterized by specific brain wave patterns, physiological changes, and functions during rest and restoration.