Lectures 1 & 2

Brain & Cognition

Neural Doctrine

Neurons are their own entities.

Syncytium

The cells in the brain form a continuous mass of tissue.

Cytoarchitectonics

Cellular Architecture (There are 52 distinct ares in the cytoarchitectonics map).

Aggregate Field Theory

The theory that the entire brain works together in behaviour.

Phrenology

A pseudoscience that looks at the bumps on the skull to predict mental traits.

Neurons

Eukaryotic cells that transmit information and have a membrane encasing the cell body.

Glial Cells

Cells that function in certain ways.

4 Types of Glial Cells

Astrocytes, Oligodendrocytes, Microglial Cell, & Schwann Cell

Astrocytes

Responsible for the blood-brain barrier, they they are in contact with blood vessels and surround neurons.

Oligodendrocytes

They form the myelin sheath in the CNS only (around the axon of the neuron) - for electrical insulation.

Microglial Cells

Responsible for removing damaged cells.

Schwann Cells

Formation of myelin sheath around neuron’s axons only in PNS - for electrical insulation.

Intracellular Fluid (Cytoplasm)

In a neuron’s cell body there is Cytoplasm which holds up the metabolic machinery that maintains the neuron.

Dendrites

The receivers of action potentials from other neurons.

Axons

Outputs information to send to dendrites (through axon terminals).

Electrical Signal

Just a signal that travels from the dendrites to cell body.

Resting Membrane Potential

When not firing action potentials, a neuron is at rest with a measure of -70mV.

Ions

Atoms or molecules with positive or negative charges.

Main ions found in the neuron

Potassium (K+), Sodium (Na+), Chloride (Cl-), & Organic Anions (A-).

Ion Channels

Channels which selectively allow certain ions to pass through. There are more K+ channels in the cell’s membrane.

Ion Pumps

Actively transports the ions and proteins.

Gated Ion Channels

Ion channels that only open and close according to nearby voltages.

Sodium-Potassium Pump (Na+/K+ Pump)

An enzyme that pumps three Na+ out of the cell and pumps two K+ inside - requires energy.

Intracellular vs Extracellular

Two ares which are separated by the membrane, intracellular is the inside of the cell, and extra is naturally outside.

Intracellular Ions

Mainly consisting of K+ and A-.

Extracellular Ions

Mainly consisting of Na+ and Cl-.

Concentration Gradient

The difference in concentration of Na+ and K+ inside and outside the cell (caused by the Na+/K+ pump).

Permeability of K+

The membrane is more permeable for K+ than it is for Na+ which leads to this difference.

Electrical Gradient

Refers to the difference in the charge between the intracellular area and extracellular area.

Concentration Gradient vs Electrical Gradient

The concentration gradient wants to move K+ from intra to extra, whereas the electrical gradient wants to move K+ from extra to intra.

Electrochemical Equilibrium State

When the concentration gradient and the electrical gradient reach a compromise - basically - leading to a difference of -70mV (resting membrane potential).

Action Potential

The rapid depolarization (meaning, getting more positive) and repolarization (going back to -70mV) of the neuron.

Dendrite Spine

Simply a protrusion on the dendrite that collects the excitatory signal.

Ligand-Gated Channels

Gated channels that only open when certain neurotransmitters bind to the matching channel receptor.

Excitatory Post-Synaptic Potential (EPSP)

The potential becomes more positively charged.

Inhibitory Post-Synaptic Potential (IPSP)

The potential becomes more negatively charged.

Decremental Conduction

A gradual reduction in strength of a signal with distance as it travels from the origin (synapse of the dendrite).

Axon Hillock

An area between the cell body and axon that integrates the EPSP and IPSP. If enough EPSP, an axon potential will fire.

Temporal Summation

Enough EPSP in a time period will have the electrical voltage reach the threshold for an action potential.

Spatial Summation

When enough EPSP reach the axon hillock simultaneously but at different locations, this will reach the threshold and fire an action potential.

Voltage-Gated Sodium Channels

Present at the axon hillock, somewhat responsible for the action potential. Triggered by the change in membrane potential. Opens when voltage is about -55mV and closes quickly after letting in Na+.

Refractory Period

When neurons cannot become active again.

Absolute Refractory Period

A period in which Na+ channels are completely closed and there is no possibility of another action potential.

Relative Refractory Period

A period where an action potential can only be generated by larger than normal depolarizing currents.

Direction of Action Potentials

Go from the axon hillock to the end of the axon terminals - they cannot go back due to the refractory periods.

Nodes of Ranvier

Sections on the axon which are not covered by a myelin sheath. Action potentials can only generate here. Rapid travelling of the action potential.

Multiple Sclerosis - Demyelination

A disease where the immune system destroys the myelin sheath, leading to slower travelling of the action potentials and thus the impairment of many functions.

Synaptic Transmission

The transferring of a signal from one neuron to another.

Two types of synapses

Electrical & Chemical (predominately chemical).

Synaptic Cleft

The space which neurotransmitters in vesicles are released into. Synapses do not touch.

Vesicles

Essentially a container of a neurotransmitter.

Chemical Synaptic Transmission

The vesicles bind to the presynaptic membrane due to the invasion of electrical currents at the axon terminal, so they release the neurotransmitters into the synaptic cleft, thus binding to their corresponding receptors.

G-Protein Coupled Receptors

A neurotransmitter binds to a receptor which activates the G-Protein which sends intracellular messengers (or G subunits) to open up the ion channels, letting ions in.

Effect of Neurotransmitter

This depends on the post-synaptic receptor the neurotransmitter binds to! Some receptors could increase firing, others could decrease firing.

Excitatory

Increases the likelihood of an action potential firing.

Inhibitory

Decreases the likelihood of an action potential firing.

Glutamate

A type of excitatory neurotransmitter that is quite prevalent. Involved in aspects like learning and memory.

GABA (Gamma-Aminobutyric Acid)

A type of inhibitory neurotransmitter that is second most prevalent. Involved in aspects like regulating mood and sleep.

Acetylcholine (Ach)

Present in the neuromuscular junction. Excites muscles.

Dopamine

Motor Control/Cognition. Produced in the Substantia Niagra and Ventral Tegmentum areas. Associated with Parkinson’s disease.

Norepinephrine

Produced in the locus coeruleus area, involved in the fight or flight response.

Serotonin

Mood/cognition, produced in the Raphe Nucleus. Associated with depression.

Dorsal

Above

Ventral

Below

Rostral

Front

Caudal

Behind

Anterior

Front

Posterior

Behind

Superior

Above

Inferior

Below

Lateral

Away from the middle, towards the side

Medial

Towards the middle, away from the side

Proximal

Close

Modistal

Far

Ipsilateral

Same side

Contralateral

Opposite sides

Coronal Plane

See from the front or the back

Saggital Plane

See from the side

Axial/Horizontal Plane

See from above or below

Central Nervous System (CNS)

Made up of the brain and spinal cord.

Nucleus

A cluster of neurons in the CNS.

Peripheral Nervous System (PNS)

Made up of everything else in the body except the CNS.

Ganglion

A cluster of neurons in the PNS.

Function of PNS

Connect the CNS to the limbs and organs.

Dorsal Root Ganglion

A sensory neuron transmitting information from the body to the CNS.

Two parts to the PNS

Autonomic Motor System (Involuntary) and Somatic Motor System (Voluntary)

Autonomic Motor System

Always active, but can be in two states: sympathetic or parasympathetic.

Parasympathetic State

Conserving energy (relaxed and at rest).

Sympathetic State

Ready for fight or flight.

Gray Matter

The layer of tissue surrounding the brain that consists of nuclei.

White Matter

The tissue mass within the gray matter that is made up of axons and glial cells.

Meninges

Three protective membranes that cover the brain.

Dura Mater

The thickest meninges near the skull.

Arachnoid Mater

Spider web looking matter that doesn’t follow the bumps of the brain, but does for the longitudinal fissure.

Pia Mater

The thinest layer that follows the gyri and sulci. Can get infected leading to meningitis.

Cerebrospinal Fluid (CSF)

A fluid that the brain floats within. The subarachnoid space (between arachnoid mater and pia mater) is filled with this fluid. Helps reduce shock and cleans.

Ventricles

Cavities in the brain also filled with Cerebralspinal Fluid.

Left and Right Lateral Ventricle

Near the top/middle of the brain → First and second ventricles.

Interventricular Foramen

Interventricular → Between the ventricles, Foramen → an opening. Between the lateral ventricles and the third ventricle.

Third ventricle.

Yup, here’s the third ventricle! Quite in the middle of the brain.