BIO 334 Principles of Neurobiology
BIO 334 Principles of Neurobiology - Study Notes
Lecture Outline/Study Guide
Overview of BIO 334 Course Structure
Overview of the Field of Neurobiology
Nervous System Organization
Anatomical Conventions
General Mammalian Brain Plan
Cerebral Cortex
a) Types of Cells
Stellate Cells
Pyramidal Cells
Meninges
a) Three Layers
Dura Mater
Arachnoid
Pia Mater
Brain Ventricles and Cerebrospinal Fluid (CSF)
a) Production, Composition, and Circulation of CSF
b) Hydrocephaly
c) Concussion
Blood Supply to the Brain
a) Stroke Types
Ischemic Stroke
Hemorrhagic Stroke
Decussation
Spinal Cord and Peripheral Branch of the Nervous System
Note: This outline is a guideline; other topics may appear in exams.
Why Study Neurobiology?
Prevalence of Adult-Onset Brain Diseases in the USA
Definition: Prevalence refers to the number of cases within the US population.
Long-term care from strokes may include various therapies based on damage severity and location.
Future discussions will cover ischemic and hemorrhagic strokes as noted in the 2013 PLoS ONE study.
Top 10 Causes of Death in the United States, 2021
Source: KFF analysis of CDC mortality and KFF COVID-19 tracker data.
Parkinson’s disease ranks #14 among causes of death.
Neurobiology Research and Its Implications
Research engages all levels of biological analysis, from molecules to synapses:
Exploration of how neurons communicate informs areas such as neuromuscular junctions, synaptic plasticity, learning & memory, language, and consciousness.
The Problem of Consciousness I
Definitions of consciousness:
Physiological Aspect: Describes consciousness in relation to the brain state associated with wakefulness.
Abstract Aspect: Relates to subjective awareness of the external world and self-awareness.
The Problem of Consciousness II
Neural Correlates of Consciousness (NCC): Defined as the minimum neural mechanisms sufficient for a specific conscious percept (Reference: Koch, 2004).
A percept is a mental representation of an object.
Different brain activity patterns correspond to various conscious states, such as sleep.
The philosophical question arises: Can external reality be an illusion, as suggested in sci-fi narratives like The Matrix or Bladerunner?
The Problem of Consciousness III
Perceptual Changes via Neuroimaging: Observed in humans viewing bistable images.
Example: Bistable image interpretation varies between an older woman looking downward and a younger woman looking over her shoulder.
The brain oscillates between different interpretations, illustrating dynamic processing.
Brain Mapping Research
Research emphasizing the detailed organization of the brain, specifically in the somatosensory cortex and motor cortex.
Case Studies in Systems Research
Example: Patient with Wernicke’s aphasia after an MCA ischemic stroke showing damage patterns in the left hemisphere.
Studies of patients with hippocampal loss (due to viral infection) demonstrating profound memory impairments (both anterograde and retrograde amnesia).
Investigation of plasticity in young brains indicating variable developmental outcomes following strokes.
Nervous System Organization I
Structure:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain: Receives/processes sensory information;
Spinal Cord: Conducts signals between brain and body, controls spinal reflexes.
Motor Neurons: Conduct signals from CNS to muscles/glands.
Sensory Neurons: Conduct signals from organs to CNS.
Functional Divisions:
Somatic Motor Division: Controls voluntary movements.
Autonomic Division: Controls involuntary responses (Sympathetic & Parasympathetic branches).
Nervous System Organization II
The Complexity of the Human Brain:
Mass: Approximately 2% of body weight
Energy Consumption: Consumes about 20% of the body's energy
Anatomical Conventions
Ipsilateral: Same side of the midline
Contralateral: Opposite side of the midline
Dorsal, Ventral, Anterior, Posterior, Rostral, Caudal, Proximal, Distal: Directions specified for various anatomical interpretations.
Finding Your Way Around the Body
Sagittal Sections: Cut parallel to the midline; Mid-sagittal goes through the midline.
Coronal Sections: Also referred to as frontal sections.
Cross-Section Terminology: Often used with the spinal cord described by its longitudinal structure.
Cerebral Cortex Overview
Cerebral Cortex Components:
Structure: Thin sheet of cells, approximately a few millimeters thick.
Divided into six layers based on cell types and structures:
Layer I: Contains incoming axons forming synapses with deeper cortical neurons.
Layers II & III: Contain pyramid-shaped pyramidal cells, with varying sizes and connections to other regions of the cortex.
Layer IV: Contains stellate cells, which are star-shaped and receive sensory information; density may vary in sensory versus motor areas.
Layer V: Displays large pyramidal cells that send motor commands out to other brain regions; particularly prominent in motor cortex.
Layer VI: Contains pyramidal neurons that send axons to other brain areas (e.g., thalamus).
The Ventricles and Cerebrospinal Fluid (CSF)
Ventricular System: A series of interconnected cavities filled with CSF.
Choroid Plexus: Highly vascular structure responsible for CSF production in each of the four ventricles.
CSF Characteristics:
Volume: 500 mL produced daily; steady-state volume approximately 125 mL.
Pathway: CSF flows through the following sequence: choroid plexus → ventricles → subarachnoid space → arachnoid villi → superior sagittal sinus → venous circulation.
Pressure Gradient: Drives CSF movement - any blockage can cause issues like hydrocephalus.
Cerebrospinal Fluid Composition Comparisons
Substance | CSF | Plasma |
|---|---|---|
Water Content (%) | 99 | 93 |
Protein (mg/dL) | 35 | 7000 |
Glucose (mg/dL) | 60 | 90 |
Osmolarity (mOsm/L) | 295 | 295 |
Sodium (mEq/L) | 138 | 138 |
Potassium (mEq/L) | 2.8 | 4.5 |
Calcium (mEq/L) | 2.1 | 4.8 |
Magnesium (mEq/L) | 2.0-2.5 | 1.7 |
Chloride (mEq/L) | 119 | 102 |
pH | 7.33 | 7.41 |
Hydrocephalus
Definition: A condition where there is an imbalance in CSF production and absorption, leading to swelling and pressure on the brain.
Causes:
Obstruction: Blockage preventing normal flow of CSF.
Poor Absorption: Issues with CSF moving into the venous system.
Overproduction: Rare instances where CSF is made faster than it can be absorbed.
Treatment: Generally involves a shunt to divert excess fluid from the ventricles.
Brain Plan - Circulation
Overview: The brain consumes 20% of the body's total energy despite being only 2% of its mass.
Blood Supply: Receives oxygenated blood mainly from the internal carotid and vertebral arteries; the circle of Willis ensures proper distribution.
Cerebrovascular Accidents (Strokes)
Types:
Ischemic Stroke: Occurs due to blood clot obstruction (Approximately 85% of strokes).
Hemorrhagic Stroke: Results from the rupture of a vessel and bleeding into the brain.
Ischemic Stroke Complex
Visual representation and patient outcomes guide understanding of stroke implications:
Symptoms include hemiplegia, sensory loss, vision issues, and aphasia depending on the affected area (e.g., Left MCA affects right side of the body).
Decussation: Refers to the crossing of nerve fibers across the midline from one side of the body to another, particularly evident in motor pathways originating from the cerebral cortex.
Spinal Cord Overview
Composition: Human spinal cord contains 31 segments, each associated with two pairs of spinal nerves.
Dorsal Roots: Carry sensory information to the spinal cord.
Ventral Roots: Transmit motor information to the rest of the body, regulating voluntary and involuntary muscle functions.
Nervous System Organization II
Similar structure description as in Organization I, reemphasizing critical functions of sensory and motor neurons in CNS and PNS.
The Enteric Nervous System
Often referred to as the 'Second Brain,' it autonomously governs the gastrointestinal tract.
Inputs and outputs are managed via afferent and efferent pathways including somatic motor and autonomic connections.