Consciousness + Cell Bio - Psyc 211

What is consciousness?

the state or quality of awareness

What is cut in split brain surgery?

Corpus callosum

Left brain controls: (3 things)

1) Muscles on right half of body

2) Complex language comp + speech + writing

3) Processing right half of visual field

Right brain controls: (3 things)

1) Muscles on left half of body

2) Limited language (small ‘dictionary’)

3) Processing left half of visual field

The Left visual field is processed by the __ half of __ eye

Right; each

The Right visual field is processed by the __ half of __ eye

Left; each

What will a split brain patient report:

1) Verbally?

2) Writing with the left hand?

3) Writing with the right hand?

1) Yes - left hemisphere sees the right side and the dot

2) No - Right hemisphere sees empty left side

3) Yes - left hemisphere sees right side and the dot

What will a split brain patient report:

1) Verbally?

2) Writing with the left hand?

3) Writing with the right hand?

1) No - left hemisphere sees empty right side

2) Yes - left side is controlled by right hemisphere which sees left visual field

3) No - left hemisphere sees empty right side

What will a split brain patient report:

1) Verbally?

2) Writing with the left hand?

3) Writing with the right hand?

1) Don’t know - the patient can’t compare because hemispheres can’t communicate

2) No answer - Left hand can’t process question / respond bc of limited language bank (right brain)

3) Don’t know - Right hand (left hem) doesn’t know what right hemisphere saw

What is Gazzaniga’s Interpreter Theory?

• No free will - behaviour is out of our control

• left brain develops meaningful narrative through which we can understand out experiences

What is the acronym for what the biological world is made up of?

CHNOPS

What are the CHNOPS?

Carbon - 11%

Hydrogen - 59%

Nitrogen - 4%

Oxygen - 24%

Phosphorus/Sulpher/Other - 2%

What are the 5 main molecules that CHNOPS form?

Water, Sugar, Fat (lipids), Nucleic Acids, Amino Acids

What are Ribozymes

A subGroup of RNA that can catalyze chemical reactions

RNA vs DNA

RNA - Single stranded chain of nucleic acids; fragile; prob gave life to first life on earth

DNA - Double stranded chain of nucleic acids; stable; primary storage of genetic info

What is the cell membrane made of (specify the two parts also)

Phospholipid bilayer

• hydrophilic phosphate head

• hydrophobic lipid tail

The ___ bilayer makes diffusion across the cell membrane ___.

Phospholipid bilayer; difficult

Prokaryotic vs Eukaryotic cells (3 pt)

Prokaryotic:

• single cell organisms

• cell membrane filled with cytoplasm

• DNA/RNA/Ribosomes free floating inside

Eukaryotic:

• Single OR Multi-cell organisms

• Contains organelles (like mitochondria and nucleus)

• Can store DNA + create energy

What is cytoplasm?

Salty nutrient filled liquid inside all cells - everything inside the cell nucleus

What are the 4 steps of protein synthesis?

1. Segment of DNA in the nucleus is unraveled and a complementary strand of RNA is created (mRNA)

2. mRNA leaves the nucleus

3. Ribosome latches onto mRNA and recruits tRNA to bring in complementary amino acids

4. Amino acids are added to a growing chain that eventually breaks off and folds into a protein

mRNA vs tRNA and what process are they found in?

Found in Protein Synthesis

mRNA - Messenger - carries genetic code from DNA to ribosomes

tRNA - Transfer - brings specific amino acids to ribosome

Proteins are chains of what?

Amino acids!

Jobs of a protein (6 listed)

Scaffolding; transporting molecules; channels; receptors; enzymes; cellular repair

4 Parts of a neuron

1. Soma - cell body

2. Dendrites - loading docks (receive chem/sensory input)

3. Axon - relay system- electrical signals sent down length

4. Axon terminals - send off point - where action potential triggers release of neurotransmitter

What is Cytosol

Salty water-like solution inside neuron/cell - filled with potassium (K⁺), chloride (Cl^-), and sodium (Na⁺)

What makes a cell specialized

What part of the DNA it reads

• neurons are filled w/ proteins that determine a cell’s role

What are the two ways Neurons communicate?

Electrically - within a cell - action potential

Chemically - between cells - neurotransmitter release

Cations vs Anions

Cations - Pos charge (Na⁺, K⁺, Ca²⁺, Mg⁺)

Anions - Neg charge (Cl^-)

Potassium (K⁺) is more abundant (inside/outside) cell and wants to (leave/enter) the cell

Inside; leave

Sodium (Na+) is more abundant (inside/outside) cell and wants to (leave/enter) the cell

Outside; Enter

What does the Sodium Potassium pump do?

Sets the concentration gradient; sends Na⁺ out of cell and K⁺ into cell

What’s the concentration gradient?

The difference in the amount of an ion present in one area vs another

What are determines where ions want to go? (2 things)

Diffusion and Electrostatic force

How does Diffusion determine Ion movement?

• Ions want to be spread out from other similar ions

• if many of the same ion are close together - there’s a pressure to spread away

• Ex: K⁺ within the cell → wants to leave

How does Electrostatic Force determine Ion movement?

• Ions want to be spread out from similarly charged ions

• opposites attract, similar charges repulse

Mom analogy

Lee and Laura are very much opposites (but they are still attracted to each other)

• Lee = K⁺

  • inside circle - always trying venture out and meet more ppl

• Laura = Na⁺

  • feels like she’s on the outside and wants to get in to the more extroverted people on the inside

Equilibrium potential of K⁺ is?

-90 mV

Resting membrane potential inside neuron?

-70mV

What does the Potassium Leak Channel do?

Allows K⁺ to move freely in/out cell; K⁺ leaking sets/maintains cell’s resting membrane potential (making it negative)

What starts an action potential? (3 things)

1. we have a negatively charged cell → pos ions want to come in bc of electrostatic pressure

2. Sodium wants to come in to lower the concentration gradient

3. A depolarizing stimulus

   1. Ex: neurotransmitters released from another cell → sensory stimulus

   2. Ex: Receptor binding opens ion channels which allows initial influx of Na⁺

Membrane potential goes from __ to __ when action potential is initiated?

-70mV → -40mV

When Sodium (Na⁺) rushes in during action potential, what is the membrane potential change?

-40mV → +40mV

Voltage Gated Sodium channel (3 pts)

• Opens when cell is slightly depolarized (aprox -40mV)

• Ball and chain system blocks pore

• Inactivates channel after opening

What ion channel aids in the return to baseline membrane potential (end of action potential)

Voltage-Gated Potassium (K⁺) channel

Voltage-Gated Potassium (K⁺) channel (2 pts)

• Opens during upswing of action potential (aprox 0mV)

• Responsible for return to baseline membrane potential

Hyperpolarization of membrane potential - action potential

(think refractory period)

Some VG K⁺ channels are still open so K⁺ leaves, sends Vm more negative then baseline

7 Stages of the Action Potential (AP) & their Vm:

1. Baseline: -70mV

2. Stimulus: -40mV

3. Upswing: increasing towards peak

4. Peak: +40mV

5. Downswing: decreasing towards hyper-polarization

6. Hyper-polarization: abt -80mV

7. Return to baseline: -70mV

What’s happening during AP stage 1? (Baseline)

Na⁺/K⁺ pump changes ion concentrations; K⁺ leak channel brings K⁺ out

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: Na⁺ wants in

What’s happening during AP stage 2? (Stimulus)

External input depolarizes cell → a few VG Na⁺ channels open

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: Na⁺ wants in

What’s happening during AP stage 3? (Upswing)

Tons of VG Na⁺ channels open; VG K⁺ channels start to open

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: Na⁺ wants in; K⁺ wants out

What’s happening during AP stage 4? (Peak)

VG Na⁺ channels are plugged by ball & chain mechanism; VG K⁺ channels still opening

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: K⁺ wants out

What’s happening during AP stage 5? (Downswing)

VG K+ channels open

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: K⁺ wants out

What’s happening during AP stage 6? (Hyper-Polarization)

Some VG K⁺ channels still open, K⁺ leaves → sends Vm more negative then baseline

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: Na⁺ wants in

What’s happening during AP stage 7? (Return to Baseline)

VG K+ channels close; Vm set by Na⁺/K⁺ pump and K⁺ leak channel

Diffusion: Na⁺ wants in; K⁺ wants out

Electrostatic Force: Na⁺ wants in

Does the force of diffusion ever change? Why?

No - the relative concentrations never change

Voltage-Gated (VG) Calcium Channel

Ca²⁺ into cell triggers neurotransmitter release

What (2) ion channels set the resting potential?

Sodium Potassium Pump (Na⁺/K⁺) & Potassium leak channel (K⁺)

What (2) ion channels open/close during action potential (AP)?

VG sodium channel (Na⁺) & VG potassium channel (K⁺)

What ion channel opens/closes at the axon terminal?

VG calcium channel (Ca²⁺)

Can an action potential ever go backwards?

Yes but only in experimental situations - never naturally.

Why doesn’t the action potential travel backwards?

• AP involves influx of pos charge ions into cell which push other pos ions away (down the concentration gradient)

• Previously active VG Na⁺ are in refractory period (ball clogging pore) → influx of pos ions can’t reopen them

What makes propagation of the action potential more efficient/faster

Myelination!

What is myelination?

An insulating layer of fat around segments of the axon (like the plastic around wires which speeds up their conductivity)

What are Glia Cells?

Crucial non-neuron cells in nervous system that provide support/protection/nourishment to neurons

4 types of Glia cells?

• Astrocytes - janitors of cell

  • break down and clean up waste

  • provide scaffolding for other cellular functions

• Microglia - nurses

  • provide immune support

  • regulate cell development + injury response

• Oligodendrocytes - contractors

  • Create myelin + wrap it around nearby axons

  • can provide sheath for 50 axons

  • *Schwann cells = equivalent in peripheral nervous system

• Ependymal Cells - soldiers

  • line the ventricles

  • Circulate CSF (cerebrospinal fluid)

What’s the effect of insulated sections of the axon on the ions inside?

The ions are insensitive to charge differences outside

What is saltatory conduction?

the propagation of action potentials along myelinated axons from one node of Ranvier to the next

What are Nodes of Ranvier?

Unmylinated segments of membrane where the AP is re-propagated

How many main types of receptors are there & what are they?

The 2 main types are Ionotropic receptors and metabotropic receptors

Ionotropic receptors (3 pts)

• Ion channels (in the name)

• Direct/fast effect on (next) cell’s potential

• EPSP or IPSP

Metabotropic receptors (3 pts)

• G-protein coupled receptors

• Can act indirectly on ion channels

• Slower modification of cell excitability

EPSP

Excitatory postsynaptic potential - NA⁺ permeable - doesn’t always induce AP

IPSP

Inhibitory postsynaptic potential - Cl^- permeable - doesn’t always prevent AP

How do Neurotransmitters get removed? (3 things)

• Re-uptake

  • re-uptake proteins transport NT bac kacross membrane of presynaptic cell

  • nt can then be repackaged into vesicle for next round of release

• Enzymatic deactivation

  • enzymes break down NT in synapse

• Diffusion

  • Released NT moves down its concentration gradient away from initial release site

What does the effect of a metabotropic receptor depend on?

The receptor itself & the signalling cascade its activation causes