Lecture 3: Cellular Function And The Plight Of Paraplegics

Front 1

Structure of Spinal Cord

Back 1

- Long, solid, tapering cylinder like structure that goes down middle of backbone
- Two nerves come out between vertebrae, one at dorsal end and one at ventral end and the two come together

Front 2

Dorsal Root Ganglion

Back 2

- Swelling filled with cell bodies on dorsal nerve coming from spinal cord
- Contain neurons that send one branch out the nerve to the body and another branch that goes into spinal cord and sends axons up in dorsal white matter area and down dorsal and ventral horn

Front 3

Ventral Horn

Back 3

- Send axons out ventral root and into nerves that go to muscles -- anterograde
- Contain motor neurons

Front 4

Dorsal Horn

Back 4

- Contains sensory neurons
- Receives sensory input from body -- retrograde

Front 5

Knee Jerk Reflex

Back 5

Stimulation - activate dorsal neuron - activate ventral neuron - stimulate muscles to move

Front 6

Spinal Cord Injury

Back 6

- Dorsal neurons, ventral neurons, nerves, muscles all in tact
- Problem is with communication between brain and spinal cord
- Brain can't send signals to spinal cord to move, dorsal neurons can't communicate with brain to brain when there is sensory input

Front 7

Polio

Back 7

- Cannot move voluntarily or involuntarily
- Issue in the ventral horn neurons or muscles themselves

Front 8

Leprosy

Back 8

- Can't feel touch/pain, have no reflexive movement
- Dorsal neurons don't work
- Sensory info doesn't get to ventral neurons, so no reflexes

Front 9

Cut Nerve Injury

Back 9

- No touch sensations or movement
- No sensory info coming in, no motor info going out

Front 10

Proteins Along Plasma Membrane

Back 10

* channels: tubes of proteins that allow ions to pass through membrane, controlled to open/close by chemical/electrical energy
* pores: tubes of proteins that are generally open
* pumps: proteins that use ATP to pump ions of one type out cell and another type into cell

Front 11

Concentration of Ions In & Around Neurons

Back 11

Na+ : high outside
K+ : high inside
Cl- : high outside
Ca 2+ : high outside
Protein: high inside

- The concentrations should be the same, but the plasma membrane doesn't allow the ions to cross by themselves (need a pump, pore, channel)

Front 12

Electrical and Chemical Force

Back 12

- Controls concentrations of ions inside and outside of cell
* Electrical force: opposites attract and likes repel
* Chemical force: entropy is increasing and ions want to be evenly distributed across both sides of membrane

Front 13

Reaching Dynamic Equilibrium (example with K+)

Back 13

- Pores allow K+ to cross membrane, leaving an imbalance in charge behind
- Inside of cell becomes more negative, but chemical forces attract K+ back into cell
- Chemical and electrical force will eventually be equal -- dynamic equilibrium

Front 14

Equilibrium Potential

Back 14

- Membrane potential in cell required to reach dynamic equilibrium

Front 15

Nernst Equation

Back 15

- describes equilibrium and and defines electrical force needed to establish equilibrium