chapter 14 pt 2 Brain and Nervous System Overview

Blood-Brain Barrier and Blood-CSF Barrier

  • The discussion centers around the blood-brain barrier and blood-Cerebrospinal fluid (CSF) barrier.

  • These barriers are areas with incomplete structures that allow for specific physiological mechanisms and protections.

Case Study of Cerebral Hemisphere Loss

  • Case example: A young man who lost his right cerebral hemisphere due to a gunshot wound.

    • Incident: The individual was shot in the head while returning to retrieve his jacket from a store after closing hours.

    • Medical intervention

    • The young man was rushed to the hospital and survived despite the loss of half his brain.

    • Restoration: Surgeons made a mold of his head post-recovery and created a lightweight artificial skull casing for him.

    • Outcome: The subject displayed remarkable cognitive abilities, graduating summa cum laude in college despite his circumstances.

Neuroplasticity

  • Neuroplasticity: Refers to the brain's ability to adapt and reassign functions that were lost due to injury, particularly notable in younger individuals.

    • Remaining brain tissue can take over functions from the damaged hemisphere, aiding in recovery and adaptation.

    • Example: The impact of neural adaptation on creativity, emotional processing, and musical learning.

Brainstem and Medullary Centers

  • The brainstem contains vital centers, particularly in the medulla oblongata, which controls critical functions necessary for survival.

Vital Centers in the Medulla

  • Cardiovascular center: regulates heart function and blood pressure.

  • Respiratory center: manages breathing rhythm.

  • Sympathetic and parasympathetic centers: maintain homeostasis during physical activities.

Cardiac Control

  • The cardiac center influences heart rate and contraction strength through intrinsic mechanisms and vagal nerve connections post-heart transplant.

  • Heart can contract independently but may not signal distress due to the lack of neural connections post-transplant, indicating the importance of the nervous system in cardiovascular health.

Vasomotor Function

  • The vasomotor center regulates blood pressure through vasoconstriction and vasodilation based on blood volume and dehydration.

    • Example Equation: Cardiac output = 70 mL × 72 beats/min = 4,900 mL.

  • Hypovolemic shock discussed in connection with blood volume and overall cardiovascular health risks.

Respiratory Control

  • Inspiratory and expiratory centers: Located in the medulla; control normal breathing patterns.

    • Tidal volume: estimated at approximately 0.5 liters during normal, relaxed breathing.

    • During exercise, the pons modifies breathing patterns, leading to more forceful inhalation and exhalation due to physical exertion.

Stretch Receptors in Lungs

  • Stretch receptors within the lungs inform the medulla to stop inhalation, initiating exhalation once enough air has been taken in.

    • The balance between inspiratory and expiratory control helps maintain effective breathing rates during various activity levels.

Reticular Formation and RAS

  • The reticular formation stretches through the brainstem and impacts consciousness, alertness, and sleep-wake cycles via the Reticular Activating System (RAS).

    • Function: Controls levels of wakefulness and sleepiness.

    • Assessment of how conditioning affects responses during encounters like waking or cardiovascular activation during early morning hours correlating with heart attack incidences.

Cerebellum Anatomy and Function

  • The cerebellum, often referred to as the "little brain", coordinates voluntary movements and balance.

    • Anatomy: Anterior lobe, posterior lobe, vermis, and numerous folds similar to gyri (folia).

    • Purkinje fibers noted for having an extensive number of synapses, aiding in complex motor functions and smooth movements.

Coordination of Movement

  • Ataxia: a disorder stemming from cerebellar deterioration leading to uncoordinated and jerky movements due to loss of control.

    • Damage to the cerebellum can lead to issues with posture and movement smoothness.

Diencephalon Functions

  • The thalamus is a major relay center for sensory and motor information, described as the brain's "traffic cop".

  • The hypothalamus plays a critical role in many autonomic functions such as hunger, thirst, thermal regulation, and emotional regulation via hormonal control.

Hormonal Control via Hypothalamus

  • The hypothalamus releases key hormones such as:

    • Oxytocin: related to social bonding and reproductive functions.

    • Antidiuretic Hormone (ADH): regulates water balance in the body.

  • Influence on balancing thirst, hunger, body temperature, and metabolic functions illustrated in relation to hormone release.

Conclusion and Neurophysial Implications

  • Discussion of the nervous system's structure versus function, emphasizing the complexities of interactions between brain regions and their respective roles in bodily functions.

  • Examples of clinical relevance and the implications of neurotransmitter dysfunction, especially in conditions like Parkinson's disease related to dopamine deficiency.

Key Definitions and Concepts

  • Neuroplasticity: The brain's ability to reorganize and adapt, particularly during childhood after injuries.

  • Medulla Oblongata: Part of the brainstem controlling vital processes like heartbeat and breathing functions.

  • Ataxia: Movement disorder characterized by lack of voluntary coordination of muscle movements, often due to cerebellar dysfunction.

  • Thalamus: Relay station for sensory and motor pathway communications within the central nervous system.

  • Hypothalamus: Critical control center for hormonal regulation and homeostasis within the body, connecting the nervous and endocrine systems.