Exam 1

What is the role of the brain?

Process information from environment, integrate for homeostasis, store knowledge/memory from past experience, and decide to execute actions

What is the brain made of?

86 billion neurons + 85 billion glial cells

What does it mean to say a brain region has a function?

Area has specialized, necessary role in producing a specific behavior, sensation, or cognitive process

Activity of neuron relationship

Closely related to a stimulus/behavior

What does it mean to say a neuron is active?

Each of regions are made up of neurons, and all neurons work in the same basic way

Active

Firing action potentials (spikes)

Action potential

Basic unit of the “language” used by the brain to hold and process information

Electrical event

Tiny and fast

Binary event

Happens or doesn’t happen

Level of activity depends on…

How frequently neurons are firing

Neurons must communicate with each other

Functions the brain must perform are complexc and require more neurons working together

More action potential means

More inputs from other neurons

Synapses

Neurons pass signals to each other

Information is carried within

Changes in electrical potential

Information is passed between neurons within

Chemical signals (synapses)

Neurotransmitters

Neuron makes a certain type of chemical that it releases onto other neurons

Flexibility

Variety of chemicals can impact one neuron and the other

Genetic influences on neural activity

Determine how a cell behaves and interacts with others

Genes

Sections of DNA

Molecular level of analysis

Genes, synapse

Cellular level of analysis

Neuron

Systems level of analysis

Circuit, region, lobe, and brain

Mind-Body problem

Philosophical challenge of explaining how our intangible mental states- thoughts, feelings, and consciousness relate to our physcial bodies and brains

Monism

Body and “mind” are qualitatively the same

Dualism

Body and mind are separate. The body is material, the mind is non-material (spiritual)

Mysterianism

Relationship between mind and body cannot be explained because limitatiosn in human understanding

Oldest recorded form of surgery?

Trepanation

Trepanation

Drilling of a hole into the skull to relieve pressure

The Edwin Smith Surgical Papyrus

Written ~2600 BCE, named after the man that bought it. Oldest known surgical treatise on trauma

Egyptians understood several key functions of brain:

Description of cranial structures, damage to nervous system can result in damage far from og site, and contralateral processing

Contralateral processing

Paralyzed limbs on the opposite side of the body

Humorism

Health and ailment controlled by four fluids

Blood (Sanguine)

Sociability, influence

Phlegm (Phlegmatic)

Calm, reservedness

Black bile (melancholic)

Sad, stupored

Yellow Bile (Choleric)

Aggressive, angry

On the Soul (De Anima), Aristotle

Soul is not floating spiritual ghost, but as the fundamental organizing principle and actuality of any living body

Hippocrates

Identified brain as “analyst of the outside world, interpreter of consciousness, and center of intelligence and willpower”

Hippocratic and Galenic thought

Rely on empirical evidence to suggest a more physical basis of mentation

Galen

Brain is the principle organ that controls all bodily functions, sensation, and thought (hegemonicon)

Alcmaeon of Croton

Dissection of cadavers revealed a physical linkage between eyes and the brain

Avicenna (Father of Modern Medicine)

Described many conditions: insomnia, schizophrenia, mania, epilepsy, stroke, paralysis, etc

al-Zahrawi (Iberian-Islamic Physician)

Treated head injuries extensively, popularized surgical interventions

Medieval Thinking

Synthesis of folk, religious, and scientific belief

De Luzzi and Vigevano

Compile first European anatomy textbook; psychosurgery was exorcism

Renaissance Thought

Rise of Humanism increased interest in philosophical, scientific, and aesthetic realism

Andreas Vesalius

Dissected cadavers, identified seven critical cranial nerves, identified corpus callosum as connecting two hemispheres

Rene Descartes

Rise of rationalism sought to end the debate once and for all

Cogito ergo sum (discourse on Method) -

We cannot doubt our existence while we doubt

Hydraulic Model

Mechanistic explanation of how the brain could control the body; nerves were hollow tubes, network of nerves all throughout the body, inside of tubes flowed humors, sensory stimulus detected —> motor output

Pineal gland

Theorized that this was controlled by the “mind” through this structure

Empiricism

Knowledge through evidence that comes from sensory experience

Use of empirical methods:

Brain works by electricity, functions can be localized to brain regions

Luigi Galvani (1700s)

Electrical stimulation of the muscles produced contractions thus humors/animal spirits are not responsible for movement (nerves operate by electricity)

Fritsch + Hitzig (Germany, 1800s)

Electrical stimulation of the brain in certain areas produced contraction of specific muscles on the opposite side of the body (contralateral processing)

Functional localization

Specific areas of the brain carry out specific functions

Franz Gall + Johann Spurzheim PHRENOLOGY

Believed different personality characteristics, intellect, etc could be determined from the shape of bumps in the skull

Phineas Gage (1848)

Former railroad construction foreman with damage to the frontal lobes of his brain; survived, but resulted in impairments in personality and social conduct

Henry VIII (1524)

History of head injuries; jousting accident

Paul Broca (1861)

Observed the brains of patients with language impairments, found that damage within a small area of the frontal lobe caused severe impairment in speech production

Carl Wernicke (1874)

Observed aphasia in which patients could understand spoken or written language; found that damage to a region of the temporal lobe caused sensory aphasia

Camillo Golgi (1871)

Developed Golgi Staining Technique; proposed “Reticular Theory” of Neurons

Reticular Theory

The brain is a series of continuous cells (reticulum)

Santiago Ramon y Cajal (1890s)

Used Golgi’s method he discovered neurons were discrete cells separated by gaps (synapses); discovered axon growth cones

Otto Loewi (1921)

Discovered first endogenous NT, “Vagustoff” (acetylcholine), chemicals stimulate cells, chemical originate cells themselves

Insular dwarfism

Evolutionary process where large-bodied animal species shrink significantly over generations when their populations are restricted to isolated environments like islands

Afferent signals

Sensation; sensory neurons

Central Nervous System (CNS)

Brain + Spinal Cord

Action

Motor; efferent signals

PNS

Nerves that allow communication of CNS with body

Higher complexity

Taking notes during lecture, signing your name, dancing

Cerebrum aka forebrain

Motor behaviors are controlled at this level

Simple/low complexity

Reflexive kick when doctor taps your knee, reflexive jerk back from painful stimulus

Spinal cord

Sensory input converted to a motor output at this level

Moderate complexity

Breathing, basic walking or running

Brainstem aka hindbrain

These motor behaviors are controlled at this level

Hierarchial Organization

Complexity of behaviors/mental processes, sequence of behavioral and neural development, and evolution of neural systems

Low complexity —> high complexity

Brainstem —> midbrain —> limbic —> cortical

Defining Evolution

Evolution is characterized by small changes between generations that accumulate over time

Darwinian Model of Evolution

Creatures evolve by changing the frequency of genetic traits, those that make creatures more likely to reproduce are passed on general fitness =/= sexual fitness

Structure Derives Function

Behaviors are not inherited, genes are and genes help define structures that give rise to behaviors

Properties of Evolution

Change is gradual, change is not planned, designed, or deliberate, dictated by genetic drift, selection can be natural or artificial, evolution can be convergent or divergent

Evolution of the brain

Primitive nerve-like cells gave rise to more sophisticated nervous system

Encephalization

Eventually neurons congregate into centralized masses

Bigger size correlates to more brain power :

Larger number of neurons, larger number of interconnections between neurons, and larger numbers of specialized circuits