Neuroscience Final

Dendrites

Input region that receives information from other neurons, may have dendritic spines which increase surface area to allow for more input, converts chemical signals from axon into electrical signals

Soma (Cell Body)

Integrates information coming from dendrites; houses basic cellular architecture (nucleus, etc.). Regulates cell function with the genetic information in the nucleus.

Axon

Long projection leading away from the soma. Information integrated by the soma is relayed down the axon. Begins at axon hillock, which generates an electrical signal called the action potential that is propagated down the axon to the terminals. May fork or branch into axon collaterals, but there is only one axon per neuron

Axon terminals

The very end of the axon, contacts the dendrites of other neurons to pass information along.

Neuron communication

Electrical potential energy stored in neuron and then fired to send neurotransmitters to the next neuron

Synapse

A synapse is the connection between an axon terminal and the next neuron, with synaptic cleft being the space between synaptic membranes

Presynaptic membrane

Part of the axon terminal that releases the neurotransmitter

Postsynaptic membrane

Part of the target cell (often in the dendrites) that detects neurotransmitters

Synaptic vesicles

Dock with the presynaptic membrane, releasing NTs into synaptic cleft. Postsynaptic membrane contains receptors that NTs bind to and receive the chemical signal

Ramon y Cajal

Used cell theory to propose the neuron doctrine, the idea that the brain is comprised of neurons using golgi stains

Reticulum Theory (Golgi)

Idea that the brain was not made up of cells, but was more like a giant net with no synapses or spaces between cells

Glial cells

Support cells in the nervous system

Astrocytes

Help form blood brain barrier by contacting blood vessels, convey nutrients from the blood to neurons to help maintain homeostasis in the extracellular environment

Oligodendrocytes

Creates myelination and Nodes of Ranvier inside the CNS

Schwann cells

Creates myelination and Nodes of Ranvier inside the PNS

Microglia

Protect the brain by scavenging for pathogens, damaged cells, and other debris. Has two states:

-Resting state: cell bodies remain still while branches move and survey area

-Reactive state: once a threat is detected, they change their shape to engulf and destroy the danger

Ependymal cells

Form the barrier around ventricles and channels containing cerebrospinal fluid and contains cilia: hairlike projections that can move to help cerebrospinal fluid flow

Somatic nervous system

Motor nerves control muscles (efferent, away from CNS)

Sensory nerves convey sensation to CNS (afferent, toward the CNS)

Spinal nerves

Sensory information about touch and movement enter the dorsal side of the spinal cord. Motor info going to skeletal muscles exits the ventral side.

Dorsal root ganglia

Contains the somas of specialized neurons that conduct sensory info from PNS to CNS.

Cranial nerves

Enter brain directly without going through spinal cord, convey info about vision, taste, etc. into brain and controls muscles of neck and head

Sympathetic nervous system

“Fight-or-flight” response, tells organs and tissue to burn metabolic energy

Parasympathetic nervous system

“Rest and digest” response, tells organs and tissue to conserve metabolic energy

Enteric nervous system

Nervous system regulating the gut microbiome

Meninges

Multilayered, fluid filled sack under the skull, contains the following from top to bottom:

-Dura mater

-Arachnoid mater

-Subarachnoid space: contains cerebrospinal fluid

-Pia mater

Ventricles

Open spaces in the brain full of cerebrospinal fluid, cerebrospinal fluid is produced in the lateral ventricles, flows through the third and fourth ventricles to the spinal cord, a one-way trip starting in brain and ending in the meninges where it is reabsorbed into the blood

Forebrain

Contains the telencephalon (cerebral hemispheres) and the diencephalon

Telencephalon

Contains the cortex, basal ganglia, and limbic system

Diencephalon

Contains the thalamus and hypothalamus

Hindbrain

Contains the cerebellum, pons, and medulla

Theory of localization

Discovered by Gall, stated that different parts of the brain carry out distinct functions

Neural system

A population of neurons that communicate across the boundaries between brain regions

Neural circuit

A population of neurons that communicate within a brain region or between immediately adjacent brain regions

Cortex

Wrinkly exterior of the human brain, plays a crucial role in many cognitive processes like perception and decision making. Wrinkles made up of gyri (gyrus) and sulci (sulcus)

Gray matter: made up of cell bodies, dendrites, unmyelinated axons

White matter: myelinated axons

Frontal lobe

Subdivision of cortex, executive function and motor control

Parietal lobe

Subdivision of cortex, touch, proprioception, etc.

Occipital lobe

Subdivision of cortex, vision, etc.

Temporal lobe

Subdivision of cortex, hearing, etc.

Neocortex

~90% of human cortical surface area, made up of 6 distinct cell layers, differentiated by size, shape, density, and connections of the neurons in each with layer I being most superficial and layer VI being the deepest

Allocortex

~10% of human cortical surface area, made up of 3 or 4 layers of cells

Lissencephalic brains

Smooth cortex

Gyrencephalic brains

Wrinkly cortex

Basal ganglia

Located deep in the forebrain beneath the cortex, critical for initiating voluntary movement

Limbic system

Important for functions such as emotion and memory (hippocampus and amygdala)

Thalamus

Directs sensory information of all types to cortex

Hypothalamus

Regulates energy intake and control of endocrine system via the pituitary gland

Tegmentum

Part of the midbrain, contains neurons that produce dopamine

Tectum

Part of the midbrain, processes audio/visual information and controls orientation responses

Medulla

Outgrowth of the spinal cord containing nuclei that give rise to the cranial nerves

Pons

Connects the rest of the brain to the cerebellum; contains nuclei that give rise to cranial nerves

Cerebellum

Crucial for precise control of motion

Post-synaptic potentials

Chemical input through NTs causes local changes in electrical charge

Action potential

If local changes in electrical charge are large enough, an action potential is generated and sent down the axon

Resting potential

A neuron’s normal electrical charge relative to area outside of the cell (-50 to -80 mV)

Negative ions

Higher concentration inside the cell

Positive ions

Higher concentration outside of the cell

Ion channels

Proteins that span the membrane and allow ions to pass through from one side to the other (Could be selective, semi-selective, or gated)

Diffusion

Ions move from more concentrated areas to less concentrated areas

Electrostatic force

Ions move away from similar charge and towards opposite charge

Sodium potassium pump

Always active, pulls 2 K+ ions into the cell for every 3 Na+ ions it removes, one molecule of ATP is consumed for each individual exchange.

Potassium channels

Pushes K+ ions back out through selective ion channels to maintain equilibrium

Hyperpolarization

When the charge inside the neuron becomes more negative, occurs when negatively charged ions enter or positively charged ions exit

Depolarization

When the charge inside the neuron becomes more positive, occurs when positively charged ions enter or negatively charged ions exit

Ionotropic receptors

Ion channels that open in response to a neurotransmitter responding to them, mostly found in the post-synaptic membrane, could have either a depolarizing or hyperpolarizing effect based on the type of ions allowed to enter

Excitatory postsynaptic potential (EPSP)

Ionotropic receptors allow positively charge ions into the neuron, causing local depolarization around the synapse

Inhibitory postsynaptic potential (IPSP)

Ionotropic receptors allow negatively charged ions into the neurons, causing local hyperpolarization around the synapse

Spatial summation

Combining the influence of PSPs across space, the closer PSPs occur in space, the more likely they are to sum together

Temporal summation

Combining the influence of PSPs across time, the closer PSPs occur in time, the more likely they are to sum together

Action potential activation

If spatial and temporal summation of PSPs depolarizes axon hillock to its threshold (-40 mV), then an action potential is generated and conducted down the length of the axon

Voltage-gated sodium channels

Initial depolarization depends on these channels which allows Na+ ions into the axon, channels open between -40 mV and +40 mV, then close at the end of that range

Voltage-gated potassium channels

Initial depolarization is followed by rapid hyperpolarization through these channels to return the charge in the axon back to resting potential. Movement of K+ out of the axon causes hyperpolarization, when charge inside the axon becomes more positive, K+ is forced out through potassium channels that are always open but the positive charge also opens additional voltage-gated potassium channels

Refractory period

Once they’ve opened and closed, the voltage-gated sodium channels will enter a brief refractory period during which they will not open again

Saltatory conduction

Describes how action potentials “jump from node to node” of a myelinated axon

-Caine drugs/Tetrodotoxin

Dulls sensation by temporarily preventing voltage-gated sodium channels from working

Voltage-gated calcium channels

Opens and allows Ca2+ ions into the axon terminal in response to depolarization caused by action potential. When calcium is detected by the calcium sensor, NTs are ejected into the synaptic cleft, so electrical communication becomes chemical communication.

Otto Loewi experiment

Tested frog hearts, stimulated vagus nerve to slow heart, then extracted chemicals outputted by the heart and tested them on a different heart, other heart slowed as well. Proves “Soups” theory of chemical communication.

Neurotransmitters

Are synthesized in presynaptic neurons and stored in axon terminals, released when action potentials arrive at axon terminals, causes some change in postsynaptic neurons that, when blocked, prevents the two cells from communicating

Ionotropic receptors

Ion channel that open when NTs bind to them, causing EPSPs or IPSPs

Metabotropic receptors

Activates G-proteins on the interior of the neuron, G-proteins are 2nd messengers that open ion channels and/or trigger a cascade of intracellular events like protein synthesis

Enzymatic degradation

Enzymes in the synaptic cleft break down the NT

Reuptake

Transporter molecules on the presynaptic cell as well as some glia grab the NT and pull it out of the synaptic cleft

Pharmacokinetics

Subsection of pharmacology that deals with the absorption, distribution, and excretion of drugs

Pharmacodynamics

Subsection of pharmacology that deals with how drugs exert their effects at the site of action

Endogenous ligands

Molecules produced by the body, such as NTs

Exogenous ligands

Molecules produced outside the body that bind to receptor sites (e.g. drugs)

Agonists

Bind to receptor and mimic the effect of the endogenous ligand

Antagonist

Bind to receptor and block the action of the exogenous ligand (or of an agonist)

Dose-response curve

The relationship between the amount of a drug administered and the effects that it causes

ED50

Effective dose 50; the amount of drug that will be effective in 50% of subjects

LD50

Lethal dose 50; the amount of drug that will be lethal in 50% of subjects

Therapeutic index

The distance between a drugs ED50 and LD50; determines the margin of safety for a drug. Wide is safe, narrow is dangerous

Sensitization

Drug effects get bigger with repeated exposure (shifts curve left)

Tolerance

Drug effects get smaller with repeated exposure (shifts curve right)

Dependence

Body becomes accustomed to functioning in the presence of the drug and reacts with withdrawal symptoms if drug leaves system

Classical NTs

Includes monoamines and amino acids, synthesized by enzymes in the axon terminal before being packaged into synaptic vesicles

Non-classical NTs

Includes neuropeptides and other NTs that are not synthesized the classical way

Neuropeptides

Amino-acid chains synthesized in the cell body, packaged into a vesicle, and then sent down the axon to the axon terminals

Glutamate

Primary excitatory NT, uses two ionotropic receptors: AMPA (Na+ channel) and NMDA (Ca2+ channel), there are also metabotropic receptors that can have an inhibitory or excitatory effect, depending on the G-protein they activate

GABA

Primary inhibitory NT, has ionotropic GABA receptors (GABAA Cl- channel for IPSPs) and metabotropic GABA receptors (GABAB receptor, activates G-proteins that tend to be inhibitory)

Acetylcholine

Involved in CNS and PNS, NT used at the neuromuscular junction (synapse connecting motor neurons to muscles), produced in basal forebrain and sent to cortex and limbic system affecting attention and memory, has ionotropic excitatory receptors and metabotropic inhibitory receptors