PSY 415 Exam 2

Nerve Net Theory

All nerves are connected to one another. Golgi supported this theory and made the Golgi Stain.

Individual Cells Theory

Neurons are all separated and not connected. Cajal used a Golgi Stain to prove that nerves are individual cells

Dendrites

Receives info

SOMA (Cell Body)

Decides if message will be sent

Axon

Pathway to send message

Myelin Sheath

Wrapped around axons which allows that neuron to talk faster. A fatty pathway

Terminal Buttons

Message goes to other neurons

Neuron

Specialized cell of nervous system that receives information and sends it to other cells

Ependymal Cells

Line ventricles, assist in producing circulating, and monitoring CSF, CNS

Oligodendrocyte

Myelinate CNS axons, providing structural framework, produces 50 myelin sheaths, CNS

Astrocyte

Chemical environment, structural support, nourish neurons, absorb and recycle neurotansmitters, form scar tissue, blood-brain barrier, CNS

Microglia

Developed by the immune system, identity/attack invaders, scavenger (phagocytosis), CNS

Schwann Cell

Produces 1 Mylein sheath (is the myelin sheath), Help regrow neurons that have been damaged, PNS

Satellite Cells

\`Supply nutrients to the surrounding neurons and also have some structural function. Also act as protective, cushioning cells. PNS

Sensory Neurons

Bring information to the central nervous system

Interneurons

Associate sensory and motor activity in the central nervous system. All neurons in your brain is this.

Motor Neurons

Send signals from the brain and spinal cord to muscles.

Tracts and Nerves

Are all large bundles of axons going to and from a particular area.

Tracts

Pathways in brain

Nerves

Pathways in the PNS

Phospholipid Bilayer

Separates extracellular fluid (outside the cell) from intracellular fluid (inside the cell)

Channel

Ions can cross a cell membrane through the appropriately shaped ______. Passive

Gated Channel

Changes shape to allow the passage of substances when gates are open and to prevent passage when one or both gates are closed. Passive

Pump

Transporter changes shape to carry substances across a cell membrane. Active

Passive

Doesn’t require energy from the neuron

Active

Requires energy from the neuron

Mitochondria

Provides cells with energy

Cell Membrane

Double layer of lipid molecules separates intra- from extra-cellular space

Lysosomes

Uses enzymes to break down waste

Nucleus

Where chromosomes reside

Golgi

Protein packaging and trafficking

Microfilaments

Provides structure to the cell; helps give it its shape

Golgi Body

Membranous structure that packages protein molecules for transport.

Lysosomes

Sacs containing enzymes that break down wastes

Microfilaments

Threadlike fibers making up much of the cell’s “skeleton”

Dendrite

Cell extension that collects information from other cells

Dendritic Spine

Small protrusion on dendrites that increase surface area

Nucleus

Structure containing the chromosomes and genes

Nuclear Membrane

Membrane surrounding the nucleus

Mitochondria

Structure that gathers, stores, and releases energy

Endoplasmic Reticulum

Folded layers of membrane where proteins are assembled

Intracellular fluid

Fluid in which the cell’s internal structures are suspended

Tubule

Tiny tube that transports molecules and helps give the cell its shape

Cell Membrane

Membrane surrounding the cell

Axon

Extension that transmits information from cell body to other cells

Chromosome

A double-stranded molecule of DNA

How Proteins are made

DNA → Transcription → mRNA → Translation → Amino Acid Polypeptide Chain → Protein

Codon

Sequence of 3 bases on mRNA that codes for a particular amino acid

Ribosomes

Protein structures that act as catalysts for protein synthesis

Golgi packages up…

Our proteins and sends them where they need to go

Step 1 of protein production

DNA uncoils to expose a gene, a sequence of nucleotide bases that encode a protein

Step 2 of protein production: Transcription

One strand of the gene serves as a template for transcribing a molecule of mRNA

Step 3 of protein production

The mRNA leaves the nucleus and comes in contact with ribosomes in the endoplasmic reticulum

Step 4 of protein production: Translation

As a ribosome moves along the mRNA, it translates the bases into a specific amino acid chain, which forms the protein

Where do proteins go?

Proteins formed in the ER enter the golgi bodies, where they are wrapped in a membrane and given a shipping address → Each protein package is attached to a motor molecule and moves along a microtubule to its destination → A protein may be incorporated into a membrane OR Remain within the cell to act as an enzyme OR Be excreted from the cell by exocytosis.

What do proteins do?

Allow communication among brain cells (receptors), carry oxygen in blood (ex: hemoglobin), digest food (enzymes like amylase, pepsin, and lactose), defend body from invading microorganisms (antibodies), speed up chemical reactions inside body (enzymes), and elasticity to skin (elastin) and strength to hair/nails (keratin)

Protein structure and function is determined by

Amino acid sequence

Gene

Carry genotype (DNA)

Protein

Express phenotype (amino acids and structure)

Location of transcription

Nucleus

Location of translation

Ribosomes in the Endoplasmic Reticulum (rough ER)

Location of protein

Blood, gut, extracellular fluid, intracellular space

Electric signals

Signals sent within the neuron. Signal sent from dendrites → cell body → Axon

Chemical signals

Signals between neurons. Terminals → Dendrite

Resting voltage

\-70mV

Ions

Charged particles

Concentration Gradient

Things like to be evenly distributed

Electrical Gradient

Cations and Anions

Cations

Positively charged

Anions

Negatively charged

Outside of the cell is ___

Positively charged

Inside of the cell is ___

Negatively charged

Sodium-Potassium Pump

Will pump out 2 K+ for every 3 Na+, requires energy, membrane 100x more permeable to K+

Voltage-gated channel

Gate opens or closes when an electrical signal is sent

Ligand-gated channel

Gate opens or closes when a chemical signal is sent

Hyperpolarization

Makes the inside of a cell more negative.

Hyperpolarization is due to …

An influx of K+ to the outside of the cell OR an influx of Cl- to the inside of a cell

Is Hyperpolarization more or less likely to have an AP?

Less likely = Presynaptic inhibition.

Depolarization

Makes the inside of a cell more positive

Depolarization is due to …

An influx of Na+ to the inside of the cell

Is depolarization more or less likely to have an AP?

More likely = presynaptic facilitation

EPSP

More likely to have AP

IPSP

Less likely to have AP

Generating an Action Potential (AP)

1. Na+ channels open, Na+ begins to enter cell. 2. K+ channels open, K+ begins to leave the cell, 3. Na+ channels become refractory, no more Na+ enters cell. 4. K+ continues to leave cell, causes membrane potential to return to resting level. 5. K+ channels close, Na+ channels reset. 6. Extra K+ outside diffuses away.

AP Characteristics

Change in internal environment, threshold (+20 mV change), All or none

Action potential phases:

Na+ floods into the cell causing depolarization, K+ floods out of the cell to repolarize the cell, K+ continues to flood out the cell causing the cell to become hyperpolarized.

Rate Law

The strength of a stimulus is represented by the rate of firing of an axon. The size of each action potential is always the same constant. How things get intense or weak.

Saltatory Conduction

Action potentials in myelinated axons

Synapse

Where communication between neurons occur

Neurotransmitters have to find…

Their specific receptor sites

Ionotropic Receptor

Transmitter binds to the binding site which then causes the pore to open, allowing the influx or efflux of ions

Metabotropic Receptors

1. Molecule of transmitter substance binds with receptor → 2. Receptor activates G protein → 3. Alpha subunit breaks away, binds with ion channel and opens it. → 4. Ions enter cell, produce postsynaptic potential.

Neurotransmitter Termination

Reuptake OR Enzymatic deactivation

Reuptake (Neurotransmitter Termination)

Goes back to the presynaptic side to be recycled and reused for another AP.

Enzymatic Deactivation (Neurotransmitter termination)

Enzyme breaks neurotransmitters down

Vesicles

House the neurotransmitters

Autoreceptor

Manages how many neurotransmitters are released. Self-regulates.

Neuromodulators

In CNS, typically peptides, diffuse effects, typically metabotropic, slower but longer-lasting

Hormones

In PNS, from glands to target cells, via bloodstream, diffuse effects, typically metabotropic, slower but longer lasting.

Epinephrine (adrenaline) (EPI)

Fight or Flight. Produced in stressful situations, increases heart rate and blood flow, leading to physical boost and heightened awareness