Mental vs. Neurological Disorders & Mind-Body Problem

Mental Disorders vs. Neurological Disorders

• Mental disorders are psychological or psychiatric illnesses, such as depression, anxiety, PTSD, personality disorders, bipolar disorder, and schizophrenia.
  • These can be hormone-based, originate from external sources, or stem from trauma.
• Neurological disorders affect the brain and nervous system, including conditions like epilepsy, multiple sclerosis, amyotrophic lateral sclerosis (ALS), Parkinson’s disease, dementia, Alzheimer’s disease, stroke, and tumors.
  • Usually have a clear pathophysiological basis.
• Both types can manifest as physical and behavioral abnormalities and involve abnormal brain function, including chemical imbalances.
• It can be difficult to clearly distinguish between mental and neurological disorders.
• Categorizing disorders either as abnormalities of the nervous system or as abnormalities of behavior may be a solution.
• The consequences of differing the two include societal stigma.

Mind-Body Problem

• Dualism posits that mental and physical realities are separate, with the mind controlling the body.
  • This is scientifically challenging to support, and difficult to conceptualize.
• Monism suggests a single reality, with two variants:
  • Physicalism (materialism) asserts only physical reality exists.
  • Mentalism (idealism) proposes only mental reality exists, with the physical world as a mental construct.
• The emergent property position suggests the mind emerges when the physical world is organized in a particular way.
  • Consciousness is thus more than the sum of its parts, similar to how water emerges from hydrogen and oxygen organization.

History of Localization of Function

• Localization of function proposes that specific brain regions are responsible for particular functions.
• Zang Fu, an ancient tradition, connected organs to mental functions but did not directly involve the brain.
  • Heart equated to happiness.
  • Lungs equated to sadness.
  • Kidneys equated to fear.
  • Spleen equated to consciousness.
  • Liver equated to anger.
• Aristotle believed the heart was the seat of intellect, a view with remnants in expressions like "follow your heart."
• Leonardo da Vinci created detailed anatomical drawings of the body and nervous system.
• Franz Gall, a proponent of phrenology, contributed to localizing brain functions and making measurements.
  • Phrenology involved mapping brain traits.

Modern View of Localization of Function

• Accepted by the majority of scientists, the modern view is that specific cortical regions perform elementary functions.
• Complex abilities arise from interconnected pathways and collaborations between brain regions.
• Neural plasticity allows other brain areas to modify their functions to compensate for damage.

Case Studies in Neuroscience

• Phineas Gage: A railroad worker who survived a metal rod piercing his brain, leading to personality changes.
  • Shows that extensive brain damage doesn't always result in death.
• Paula Broca's Patient "Tan"
• Mike the Headless Chicken
• H.M. Cases

Brain Video Notes

• The brain consists of 90 billion neurons.
• There can be two separate minds within one system.
• Most brain activity occurs without conscious awareness.
• During sleep, the prefrontal cortex is not active, but the motor cortex, visual cortex, language, and balance areas are.
• Brain waves vary in frequency, and drugs can alter communication between brain regions, affecting consciousness.
• The thalamus acts as an information hub, processing auditory, visual, and pain information.
• Communication is key to individual identity; split-brain surgery patients demonstrate separated minds.
• The corpus callosum connects the left and right hemispheres.
• Split-brain surgery, which severs this connection, can prevent the spread of seizures.
• The left hemisphere controls the right side of the body, and vice versa.
• The right hemisphere specializes in evaluating emotions and visualizing space.
• Split-brain patients can perform tasks with the disconnected hemisphere without conscious awareness.
• The brain has over 100 distinct regions for various functions, including vision, movement, speech, and social interaction.
• The belief that our mind is in control is a misconception.
• External factors, including people, influence the brain.
• Emotions like greed and guilt impact decision-making.
• The insula signals to prevent harm to others.
• The ventral medial prefrontal cortex acts like a thermostat.
• Social interaction and experiences can profoundly impact brain biology across generations, and trauma can affect future generations.
• The WWII Dutch famine led to metabolic issues in subsequent generations.
• Mice experiments showed that changes related to the scent of almond could be passed down to the next generation.
• Transcranial magnetic stimulation (TMS) can stimulate brain regions and influence movement.
• Spontaneity involves decreased prefrontal cortex activity.

Case Study: H.M.

• Henry Molaison (H.M.) underwent surgery involving removal of the hippocampus bilaterally to control seizures.
• The case suggested remembering involves multiple brain systems, as H.M. lost recall ability of explicit memories but retained procedural memory formation.
• H.M. had difficulty thinking of the future.

Experimental Demonstration of Localization of Function

• In 1870, Fritsch and Hitzig studied dog brains using electrical stimulation and ablation (tissue removal).
• Specific brain parts were found to be involved in particular functions.
• Using multiple methods to confirm the same thing is convergence.

Neurosciences

• Neurosciences: the scientific study of the nervous system.

Neurosciences and Related Fields

• Clinical Neuropsychology
  • Focus on assessing cognitive, affective, and behavioral functioning associated with brain (neurological) disorders.
  • Common for clinical neuropsychologists to have a PhD or Psy.D. in clinical psychology with specialized training in neuropsychology
• Neurology
  • Applied area of neuroscience
  • Specialization in medicine
  • M.D. (Doctor of Medicine)
  • Focus on the assessment and treatment of neurological/nervous system disorders/brain disorders
• Neuropharmacology
  • Scientific area of neuroscience
  • Study of the influence of drugs on the nervous system
• Neuroanatomy
  • Study of the structure (physical makeup) of the nervous system
  • Scientific area of neuroscience
• Clinical psychology (not a neuroscience)
  • Specialization concerned with the assessment and treatment of mental disorders
  • Applied area of Psychology
  • Practitioners have a PhD or Psy.D. in Clinical Psychology
• Psychiatry (not a neuroscience)
  • Medical specialization concerned with assessing and treating mental/psychological/psychiatric disorders
  • Practitioners have an M.D. or D.O. (Doctor of Osteopathic Medicine (holistic approach to helping patients))
  • Treatment is usually a drug, but psychotherapy is sometimes used. Brain and Behavior/Biopsychology/physiological Psychology/behavioral neuroscience
  • Specialization concerned with understanding how behavior and psychological processes are related to the body, with a focus on the nervous system

The Nervous System’s Functional Anatomy

• The following terms should be memorized along with tree diagram
• Central nervous system
  • Brain
    • Hindbrain – medulla, pons, cerebellum
    • Midbrain
    • Forebrain – 6 major structures:
      • Thalamus, hypothalamus, corpus callosum, basal ganglia, hippocampus, cerebrum
  • Spinal cord
• Enteric Nervous System
• Peripheral nervous system
  • Somatic nervous system
  • Autonomic nervous system
    • Sympathetic N.S.
    • Parasympathetic N.S.

Central vs Peripheral N.S.

• Central: brain and spinal cord
• Peripheral: everything outside the brain and spinal cord

Peripheral Nervous System: Somatic Nervous System

• Skin sensations and skeletal muscle movement
• Attached to cell bodies that reside in the spinal cord. Then they go out and release chemicals onto muscles and allow them to move.
• Skin  afferent nerve  spinal cord  efferent nerve  muscle. Anything outside is part of the central nervous system. Skin to spinal cord is part of the somatic.
• Communicates skin sensations
• Communicating to muscles

Peripheral Nervous System: Autonomic Nervous System

• Parasympathetic
  • Decrease in this decreases heart rate
• Sympathetic
  • Increase in this increases heart rate
• Constant communication of organs, glands, and vasculature
• They regulate what happens in the body at all times

Enteric Nervous System

• Lining of the gut
• The neurons are involved in gut functions like bowel motility, secretion, and blood flow to permit fluid and nutrient absorption as well as to permit waste elimination
  • Possible our mental states affect our digestion and vice versa.
• A growing evidence implicates the ENS in many mental disorders
• Psychobiotics (compounds containing live microorganisms) is the name of a new type of treatment for mental disorders.

Spinal Cord (Central NS)

• Bell-Magendie Law:
  • Dorsal (back side) nerves carry skin sensory info
    • Skin sensations carried to central NS in the back side of the spine
  • Ventral (stomach side) nerves carry motor (skeletal muscle movement) info
    • Laws in science are descriptive (not proven)
    • Theories are explanatory

Individual Neuron: white matter vs gray matter

• White matter is in the peripheral areas (lighter color) of the spinal cord (lots inside the brain)
  • Myelinated axons give the white appearance
    • Myelin sheaths speed up the transmission of information
• Gray matter is in the central areas (darker color) of the spinal cord (lots on outside of the brain)
  • Color due to presence of somas (cell bodies of neurons) and dendrites

Hindbrain: Medulla, Pons, and Cerebellum

• Medulla – critical for staying alive. Involved in vital functions such as breathing and heart rate
• Pons – bridge between the cerebellum and many other areas of the brain
• Cerebellum – involved in many functions including planning and executing complex movement sequences
  • Functions: balance, coordination, movement sequences

Midbrain

• Houses several areas (nuclei) that produce neurotransmitters (chemical messengers) and contains the superior and inferior colliculi.
• Two bottom bumps are inferior colliculi
• Two top bumps are the superior colliculi
  • Superior colliculi – involved in visual reflexes, especially orienting the head and eyes toward something that is seen
  • Inferior colliculi – involved in auditory reflexes, especially orienting the head and eyes toward something that is heard

Forebrain

• Thalamus – involved in organizing, integrating, and projecting sensory information (except smell) to and from the cerebral cortex.
• Hypothalamus – involved in temperature regulation, eating, drinking, and sexual behavior.
• The term brainstem is usually used to refer all of the structures of the hindbrain, midbrain, and the thalamus and hypothalamus
  • Medulla, pons, and cerebellum
  • 4 F’s
• Corpus callosum – a major connection (commissure) between the 2 cerebral hemispheres
  • Commissure – a structure that connects the two hemispheres
• White matter – composed mostly of myelinated axons.
• Gray matter – composed mostly of neuron cell bodies (somas) and dendrites
• Individual neuron – white matter vs gray matter
• Basal Ganglia – group of subcortical forebrain structures involved in coordinating movement. Hippocampus – involved in many types of memory and spatial navigation

Cerebrum: Lobes of the cerebral cortex

• Frontal lobe, parietal lobe, occipital lobe, and temporal lobe
• Cerebral cortex – refers to the gray matter (dendrites and somas) on the outside of the forebrain
• Cerebrum – refers to both gray matter on the outside of the forebrain and the white matter beneath the gray matter

Major Structures:

• Longitudinal fissure – groove right down the middle of the brain.
• Lateral (sylvian) fissure - above the temporal lobe. Long, deep groove in surface of cerebral cortex that divides the temporal lobe from the parietal lobe and the temporal lobe from the frontal lobe.
  • Fissure = long, deep groove in the surface if the cerebral cortex
• Sulcus – a groove in the surface of the cerebral cortex (the longer, little squiggly ones)
  • Central sulcus – groove that separates the frontal lobe from the parietal lobe
• Gyrus - Bump in between the grooves (the little squiggly bumps)

Perspectives when viewing the brain: Planes

• Coronal plane – from the front or the back (sliced straight down)
• Horizontal plane – top or bottom of brain
• Sagittal plane – side or other side of brain
  • Mid-sagittal section of the brain
    • When you see a sliced view of the inside of the brain

Anatomical terms for direction and spatial relationships

• Superior – dorsal (above another structure or toward the top of the brain)
• Inferior – ventral (below another structure or lower part of the brain)
  • Ex. Hypothalamus is ventral to the thalamus and is on the anterior region of the thalamus
• Anterior – front of the brain
  • Ex. Frontal lobe
• Posterior – back of the brain
  • Ex. Occipital lobe
• Medial –
  • Along the midline of the brain is the most medial region
• Lateral – sides, away from the midline

Cells of the Nervous System

• 2 basic types of cells in the nervous system
  • Neurons (nerve cells) –
    • Major cell type in the NS
    • Receive and communicate information… sometimes described as the information processing unit of the nervous system
    • Information processing unit of the NS
  • Glia – glial cells, neuroglia

Categorizing Neurons

• By structure (physical appearance)
  • Unipolar
    • One extension from the soma
  • Bipolar neuron
    • Two extensions from soma
    • Extensions are either dendrites or axons
  • Multipolar neuron
    • Three or more extensions from soma
• By function
  • Sensory neurons
    • Directly respond to environmental (outside the NS) stimulation
    • Ex. Vision
    • Transduction, converting physical energy into electrochemical signals
  • Motor neurons
    • Communicate to skeletal muscles, causing their contraction
    • Directly causing skeletal muscles to contract
  • Interneurons
    • Communicate information between neurons
    • Most neurons in the brain

Glial Cells (Glia)

• Provides insulation and support, aids in repair of neurons, and helps with waste elimination
• two types of glial cells
  • Oligodendrocyte (oligodendroglia cell)
    • Forms the myelin sheath on axons in the central nervous system (brain and spinal cord)
  • Schwann cells (his fav)
    • Forms the myelin sheath on axons in the somatic branch of the peripheral nervous system
    • Wraps around axons. One segment around the axon.

Anatomy of a neuron: Major components

• Cell body (soma)
  • Core region of the cell containing the nucleus and other organelles
• Dendrite
  • Branching extensions from the cell body
• Axon
  • Specialized for carrying information to other cells
• Axon hillock
  • Juncture of the cell body (soma) and axon
• Terminal button (axon terminal… and many other names are used)
  • Knob (swelling) at the end of an axon that stores and releases chemicals, thus conveying information to other cells
• Myelin Sheath
  • Insulation formed by glial cells on some axons
  • Not all axons have myelin sheaths
• Nodes of Ranvier
  • gap between two myelin sheaths on an axon
  • A place where the membrane of the axon is exposed to fluid outside the cell (extracellular fluid)
• Synapse
  • Spatial junction between one neuron and another; forms the information transfer site between neurons
  • Synaptic transmission

Axon vs Nerve (cross-section)

• Thousands of axons in one nerve
• Nerve are big cables with axons inside it in the Peripheral NS.

How Neurons Use Electrical Signals to Transmit Information

Action Potential How a signal travels down an axon

Action Potential

• Brief and dramatic depolarization of the membrane of an axon
• Sodium and potassium cations

Ions

• Electrically charged particle
  • Cation: positively (+) charged particle
  • Anion: negatively (-) charged particle
• Ion channel: pore through which ions may pass into or out of the cell… ion channels are embedded in the membrane of the cell

Relative concentrations of sodium and potassium ions

• Signal traveling down an axon, sodium (Na+) ions have a higher concentration outside the cell compared to inside the cell
• No signal is travelling down an axon, potassium (K+) ions have a higher concentration inside the cell compared to outside the cell
• ( K+ inside, Na+ outside, wanna keep it that way)

2 forces that control the movement of ions (critical in neural communication)

• Diffusion
  • The tendency for molecules to distribute themselves evenly
  • Thus, ions will have a tendency to move from an area of greater concentration to an area of lesser concentration
• Electrostatic pressure
  • Opposite charges attract
  • Like (same) charges repel
  • Thus, ions will have a tendency to move to an area with its opposite charge and move away from an area with its same charge

Four steps of action potential

• Na+ ion channels open
• Na+ ions move inside the axon
• K+ ion channels open
• K+ ions move outside the axon
• Happens all the way down the axon to be released outside the terminal buttons

Voltmeter

• Registers the difference in electrical charge between the inside and outside of the cell (membrane potential)
  • Difference in electrical charge across the membrane

Oscilloscope

• Records the changes in the membrane potential (electrical difference) over time

Measuring the neuron’s electrical activity

• Membrane potential
  • Difference in electrical charge (in millivolts) between the inside and outside of a cell – in reference to the action potential it is the difference in electrical charge between the inside and outside of an axon

Depolarization

• When the inside of the axon is less negative than it was at resting potential

Resting potential

• Membrane potential in the absence of stimulation or an action potential
• At resting potential the inside of the axon is negatively charged with respect to the outside (often about -70mV)

Graded potential

• Small voltage fluctuations across the membrane (between the inside and the outside) of the axon

Hyperpolarization

• When the inside of the axon is more negatively charged than the resting potential value Threshold of excitation – minimum amount of depolarization required in order for an action potential to occur

Reversed polarization

• When the membrane potential has a positive value

Repolarization

• When the membrane potential is returning back to resting potential after the peak of the action potential “spike”

Voltage-activated ion channels

• Open and close at specific membrane voltages
• When threshold is reached, sodium channels open up, sodium comes inside, makes membrane potential move up on the graph

Saltatory conduction

• Refers to the fast movement of signal in a myelinated axon; action potentials only occur in the nodes of Ranvier

Example of a drug that directly affects action potentials: Lidocaine

• A local anesthetic also commonly injected by a dentist for decreasing pain
• Decreases signaling (action potentials) in sensory neurons
• Decreases signaling by blocking sodium ion channels in the sensory neuron axons

Explores the similarities and differences between mental and neurological disorders, highlighting the limitations of their current distinction. It discusses dualism, monism (physicalism & mentalism), emergence, and alternative categorization approaches. Also touches on potential medical curriculum changes.