Introduction to Cognitive and Brain sciences

Cognitive and Brain Sciences Flashcards

Gene

Coding DNA sequences that are the templates for messenger RNA and regulatory DNA sequences that control the qualities a gene is expressed in a given cell type.

Genomics

Analysis of DNA sequences (both coding and regulatory) for a species or an individual and has provided insight into how nuclear DNA helps determine the assembly of the brain and the rest of the nervous system.

Nerve cells/neurons

Cells that specialize in electrical signalling over long distances

Glial cells

Cells that support the signals produced by nerve cells rather than actually generating signals themselves, contribute in repairing nervous system damage and acting as stem cells in some areas of the brain where they promote regrowth of damaged neurons

Synapse

The point at which a nervous impulse passes from one neuron to another

Axon

Where information is sent from the nerve cell

Dendrites

Where information is received in the nerve cell

Cell body (soma)

Where information is received and sent back out of the nerve cell

Myelinated axon

The fat around axons that help to speed up transmission

Convergence

The degree of inputs to a single neuron

Divergence

The number of targets supplied by a neuron

Neurotransmitters

The chemicals which allow the transmission of signals from one neuron to the next across synapses

Synaptic cleft

The site where extracellular proteins influence the diffusion, binding and degradation of the molecules

Action potential

A self regenerating wave of electrical activity which conveys electrical signals over distances

Functions of Glial Cells

Maintaining the ionic milieu of nerve cells, modulating the rate of nerve signal propagation, modulating synaptic action by controlling the uptake and metabolism of neurotransmitters at or near the synaptic cleft, providing a scaffold for some aspects of neural development, aiding or impeding recovery from neural injury , providing an interface between the brain and the immune system and facilitating the flow of interstitial fluid through the brain during sleep (washing out metabolic waste)

Astrocytes

Glial cells restricted to the CNS that maintain an appropriate chemical environment for neuronal signalling, secreting substances that influence construction of new synaptic connections and retaining characteristics of stem cells

Oligodendrocytes

Glial cells restricted to the CNS that lay down a laminated, lipid-rich wrapping of myelin around some axons (speeds up the transmission of electrical signals) and also function through retaining neural stem cell properties and generating new oligodendrocytes in response to injury and disease

Microglial cells

Glial cells derived primarily from hematopoietic precursor cells but in some cases are derived from neural precursor cells and function in removing cellular debris from sites of injury or normal cell turnover, secrete signalling molecules that modulate local inflammation and influence whether a cell survives or dies

Glial stem cells

Glial cells found throughout the adult brain and function in retaining the capacity to proliferate and generate additional precursors or differentiated glial and in some cases, neurons

Neural circuits

Organised ensembles of neurons that process specific kinds of information

Afferent neurons

Nerve cells that carry information from the periphery toward the brain or spinal cord

Efferent neurons

Nerve cells that carry information away from the brain or spinal cord

Interneurons

A neuron who's relatively short axon branch locally to innervate other neurons

Electrophysiological recording

Measures the electrical activity of a nerve cell

Extracellular recording

Electrophysiological recording where the electrode is placed near the nerve cell to detect its activity

Intracellular recording

Electrophysiological recording where the electrode is placed inside the cell of interest

Calcium imaging

Records the transient changes in intracellular concentration of calcium ions that are associated with action potential firing

Optogenetics

Involves using molecular genetic tools

Sensory systems

Acquire and process information from the internal and external environments

Motor systems

Respond to information by generating movement

Central nervous system (CNS)

Comprised of the brain (cerebral hemisphere, deincephalon, cerebellum and brainstem) and the spinal cord

Peripheral nervous system (PNS)

Comprised of sensory neurons that link sensory receptors (on body surface or deeper) with relevant processing circuits in the CNS and motor portion consisting of motor axons (connect the brain and spinal cord to skeletal muscles) that makes up the somatic motor division and cells and axons that innervate smooth and cardiac muscle and glands, making up the visceral or autonomic motor division

Characteristics that distinguish Neural Systems

Unity of function, representation of specific information, specific connectivity among select brain regions and subdivision into subsystems for relaying and processing

Functional analysis

Evaluate the electrical and metabolic activity of the neuronal circuits that make up a neural system

Resting membrane potential

The inside negative electrical potential that is normally recorded across all cell membranes

Receptor potentials

Due to the activation of sensory neurons by external stimuli (light, sound or heat)- neurons respond with a receptor potential that changes the resting potential for fraction of a second

Synaptic potentials

Associated with communication between neurons at synaptic contacts, allows for transmission of information from one neuron to another and serve as means of exchanging information in the complex neural circuits in both the central and peripheral nervous system

Action potentials

Signal generated and conducted along axons and is responsible for long range transmission of information within the nervous system, allowing the nervous system to transmit information to its target organs

Active transporters

Proteins that actively move ions into and out of cells against their concentration gradients

Ion channels

Proteins that allow only certain kinds of ions to cross the membrane in the direction of their concentration gradients

Equilibrium potential

The membrane potential where a given ion is in electrochemical equilibrium that can be predicted by the Nernst Equation

Voltage Clamp Method

Controls or clamps membrane potential (or voltage) at any level - measuring the membrane potential with an electrode placed inside the cell and providing information to define the ion permeability of the membrane and indicates how membrane potential influences ion current to flow across the membrane

Myelination

The process where glial cells wrap around axons to form multiple layers which insulates the axonal membrane that improves the passive flow of electrical current, reduces the ability of current to leak out of the axon which increases the distance local current can flow passively along the axon and increases the speed of action potential conductance

Ion selectivity

Channels that are able to discriminate between Na+ and K+

Patch Clamp Method

An established technique, capable of measuring currents flowing through single channels and revolutionised the study of membrane currents

The patch clamp method

A glass pipette with a small opening is used to make tight contact with a small area of neuronal membrane - the seal between the pipette and membrane is so tight that all ions flow through an ion channel, flow into the pipette and minute electrical currents can be recorded - conveying a wealth of information about the function of ion channels

Microscopic currents

Currents flowing through single channels

Macroscopic currents

Currents flowing through a large number of channels distributed over a much more extensive region or surface membrane

Voltage-Gated Ion Channels

Ion channels that are opened or closed in response to changes in the transmembrane potential and include those that are selectively permeable to each of the major physiological ions Na+, K+ Ca2+ and Cl- which open and close depending on the voltage

Ligand-Gated Ion Channels

Channels that respond to chemical signals (ligands) rather than to changes in the membrane potential and are essential for synaptic transmission and other forms of cellular signalling phenomena

Thermosensitive ion channels

Ion channels that contribute to the sensations of pain and body temperature and open in response to specific temperature ranges

Mechanosensitive channels

Channels that respond to mechanical distortion of the plasma membrane and are the critical components of stretch receptors and neuromuscular stretch reflexes

Active transporters

Move ions against their electrochemical gradients and form complexes with ions they are moving

ATPase Pumps

Membrane pumps that use the hydrolysis of ATP to translocate ions against their electrochemical gradients

Ion exchangers

An active transporter that does not use ATP directly but instead, uses the electrochemical gradients of other ions as an energy source

Anti-porters

Exchange intracellular and extracellular ions and are a type of ion exchanger

Co-transporters

Work by carrying multiple ions in the same direction and are a type of ion exchanger

Electrical synapses

Permit direct, passive flow of electrical current from one neuron to another which is usually sourced from the potential difference generated locally by the presynaptic action potential and arises at an intercellular specialisation known as the gap junction

Chemical synapses

Transmit information via the secretion of chemical signals (neurotransmitters)

Advantages of Electrical synapses

Transmission is extraordinarily fast, transmission can be bidirectional

Signalling transmission at Electrical Synapses

The processes of the presynaptic and postsynaptic neurons are connected via a gap junction which contains connexons (composed of ion channel proteins - connexins, which serve as subunits to form connexon channels formed of transmembrane domains - these hemi- channels form a pore that connects the two cells and permit electrical current to flow

Quanta

The amount of neurotransmitter released from the vesicle

Ionotropic receptors (or ligand-gated ion channels)

Receptors in which the ligand binding site is an integral part of the receptor molecule that have immediate effects

Metabotropic receptors (also called G-protein-receptors)

Receptors that are indirectly activated by the action of neurotransmitters or other extracellular signals typically through G-protein activation that produce long term effects

Excitatory (or EPSPs)

Postsynaptic potentials that increase the likelihood of a postsynaptic action potential

Inhibitory (or IPSPs)

Postsynaptic potentials that decrease the likelihood of a postsynaptic action potential

Small molecule neurotransmitters

The non- peptide neurotransmitters such as acetylcholine (ACh), the amino acids glutamate, aspartate, GABA, glycine and biogenic amines

Neuropeptides

A general term used to describe a large number of peptides that are synthesised by neurons and function as neurotransmitters or neurohormones

Neuropeptides/peptide neurotransmitters

Relatively large transmitter molecules composed of 3 to 36 amino acids

Small molecule neurotransmitters

non-peptide neurotransmitters e.g acetylcholine, amino acids such as glutamate, aspartate, GABA and glycine, purines such as ATP, and biogenic amines such as catecholamines (dopamine, norepinephrine, epinephrine), indoleamine (serotonin - submitted widely across the brain), imidazoleamine (histamine)

Amino acids: Glutamate

Most important transmitter for normal brain function which is synthesised in neurons from local precursors due to it not crossing the blood-brain barrier via the glutamate-glutamine cycle which allows glial cells and presynaptic terminals to maintain an adequate supply of glutamate for synaptic transmission and to rapidly terminate postsynaptic glutamate action

Neuropeptides/Peptide Neurotransmitters

Modulate hormones, are involved in the perception of pain and regulate complex responses to stress via mechanisms responsible for synthesising and packaging peptide transmitters are different from small molecule neurotransmitters and are very similar to those used for the synthesis of proteins secreted from non-neuronal cells

Unconventional Neurotransmitters

Some unusual molecules are used for signalling between neurons and their targets but are not considered conventional neurotransmitters because they are not stored in synaptic vesicles and are not released from presynaptic terminals via exocytotic mechanisms - they do not need to be released from presynaptic terminals and are often associated with retrograde signalling (which is postsynaptic cells back to presynaptic terminals)

Retina

The innermost layer of the eye and contains neurons that are sensitive to light and transmit visual signals to central targets

Uveal tract

The immediately adjacent layer of tissue to the retina and includes three distinct but continuous structures referred to as the uveal tract - largest component of the uveal tract is choroid (composed of a rich capillary bed that nourishes the retinal photoreceptors) and is also made up by the ciliary body (ring of tissue that encircles the lens is made up by two parts; muscular component adjusting to the refractive power of lens and a vascular component that produces the fluid that fills the front of the eye) and iris (coloured part of the eye which contains two sets of apposing muscles that allow the size of the pupil to be adjusted under neural control - the pupil is the opening in the centre)

Sclera

Forms the outermost tissue layer of the eye and is composed of a tough, white, fibrous tissue

Cornea

At the front of the eye, is a highly specialised transparent tissue that permits light rays to enter the eye

Aqueous humor

In the anterior chamber, just behind the cornea and in front of the lens that is a clear, watery liquid that supplies nutrients

Vitreous humor

The space between the back of the lens and the surface of the retina is filled with thick, gelatinous substance

Accommodation

Dynamic changes in the shape of the lens

Emmetropia

normal eye with relaxed ciliary muscles result in a focused image in the distance

Myopia

Nearsighted eye where light rays are focused in front of the retina

Hyperopia

Farsighted eye where light rays are focused beyond the retina

Fundus

The surface of the retina

Macula lutea

A circular region containing yellow pigment located near the centre of the retina - this region supports high visual acuity which is the ability to resolve fine details

Fovea

A small depression or pit in the retina which is where acuity is greatest

Photoreceptors

Specialised photosensitive neurons

Rods and cones

Two types of photoreceptors with an outer segment adjacent to the pigment epithelium which contains membranous disks with light-sensitive photopigment and inner segment that contains the cell nucleus and gives rise to synaptic terminals that contact bipolar or horizontal cells

Horizontal cells

Enable lateral interactions between photoreceptors and bipolar cell that maintain the visual systems sensitivity to contrast over a range of light intensities (luminance)

Amacrine cells

Are postsynaptic to bipolar cell terminals and presynaptic to the dendrites of ganglion cells make distinct contributions to visual function

Retinal organisation

Light rays pass through various non-light sensitive elements of the retina as well as retinal vasculature before reaching the outer segments of the photoreceptors where photons are absorbed due to the relationship that exists with the outer segments of the photoreceptors and the pigment epithelium

Roles played by the pigment epithelium

Removal of photoreceptor disks and to regenerate photopigment molecules after they have been exposed to light

Hyperpolarisation

Shining a light on a photoreceptor results in this

ON-centre and OFF-centre neuron

Ganglion cells that respond to stimulation of a small circular patch of the retina - this defines the cell’s receptive field

Optic tract

Ganglion cell axons on each side of the optic chaism

Hypothalamus

Regulates circadian rhythms which is associated with sleep

Pretectum

Responsible for the reflex that controls the pupil and lens

Superior colliculus

Orients and coordinates the movement of head and eyes

Magnocellular layers

Components of the primary visual pathway, specialised for perception and detection of motion and movement

Parvocellular layers

Also components of the primary visual pathway and specialised for the detection of detail, colour and fine grained stimulus