Lecture 5

Question 1

What are glycoproteins?

Answer 1

Proteins that have sugars stuck to them

Question 2

What are glycolipids?

Answer 2

Phospholipids that have sugars attached to them

Question 3

What is the main function of glycoproteins and glycolipids?

Answer 3

Adhesion of cells to each other or to the extracellular matrix

Question 4

What is the glycocalyx?

Answer 4

A barrier outside the cell wall formed by sugar groups and water

Question 5

What role does the glycocalyx play?

Answer 5

Acts as a buffer and identification tags for the immune system

Question 6

What happens if sugars are in the wrong arrangement on cells?

Answer 6

The immune system may attack those structures

Question 7

What is osmotic pressure?

Answer 7

Pressure generated by solutes in a solution, can be dangerous in certain situations

Question 8

What does the equation 1 mOsm = 20 mmHg indicate?

Answer 8

The relationship between osmolarity and osmotic pressure

Question 9

What is Vrm?

Answer 9

Resting membrane potential

The charge difference between inside and outside of the cell

• average motor neuron cell around -80
• average smooth muscle cell around -65

Question 10

Which ions are primarily involved in determining resting membrane potential?

Answer 10

K+ and Na+

Question 11

What does the Nernst potential refer to?

Answer 11

Voltage that prevents ions from diffusing across the membrane due to concentration gradients

Question 12

What is the permeability ratio of K+ to Na+ at rest?

Answer 12

10:1 (more permeable to K+ than Na+)

Question 13

What happens during depolarization?

Answer 13

The cell becomes less negative, moving towards a more positive charge

• due to influx of Na and some Ca

Question 14

What is hyperpolarization?

Answer 14

When the membrane potential becomes more negative than resting membrane potential

Question 15

What is the threshold potential?

Answer 15

The membrane charge that must be reached to guarantee an action potential

Question 16

What is the role of voltage-gated sodium channels?

Answer 16

They open quickly to allow Na+ influx during action potentials

Question 17

What happens if a neuron depolarizes enough?

Answer 17

Reaches threshold and An action potential is initiated

Question 18

What is the typical resting membrane potential for a cell?

Answer 18

Around -80 mV

Question 19

Fill in the blank: The most negative the membrane potential could be is _______.

Answer 19

-90 mV

Question 20

Fill in the blank: The most positive the membrane potential could be is _______.

Answer 20

+61 mV

Question 21

What is Ohm’s Law in relation to biological systems?

Answer 21

V=IR

where I is current, V is voltage, and R is resistance

Question 22

What does depolarization result in during an action potential?

Answer 22

An increase in membrane potential towards a positive value

Question 23

What is the primary ion responsible for depolarization in skeletal muscle?

Answer 23

Sodium (Na+)

Question 24

What initiates the depolarization in skeletal muscles?

Answer 24

Acetylcholine binding to its receptor

Question 25

What is the effect of the slow calcium channels in heart cells?

Answer 25

They create a plateau in the action potential

Question 26

What is the consequence of failing to repolarize in heart cells?

Answer 26

The heart won't be able to pump effectively

Question 27

What is a synapse?

Answer 27

A junction where one cell can communicate with another via neurotransmitters Space between presynaptic terminal and post synaptic terminal

Question 28

What happens during hyperpolarization?

Answer 28

The membrane potential briefly drops below the resting membrane potential

Question 29

What is the relationship between permeability and membrane potential?

Answer 29

Higher permeability to an ion will shift the membrane potential closer to that ion's equilibrium potential

Question 30

What is the primary ion involved in muscle depolarization?

Answer 30

Sodium (Na+) ## Footnote Sodium influx into skeletal muscle causes depolarization.

Question 31

What triggers muscle depolarization?

Answer 31

Acetylcholine binding to its receptor on the muscle ## Footnote This binding opens acetylcholine ion channels, allowing sodium to enter the cell.

Question 32

What type of channels open in response to initial depolarization?

Answer 32

Fast Sodium Channels ## Footnote They are voltage-gated and open quickly to allow further sodium influx.

Question 33

What is the result of the opening of fast sodium channels?

Answer 33

Initiates an action potential ## Footnote This process leads to a chain of events that spreads the action potential down the cell.

Question 34

How long do action potentials typically last?

Answer 34

.15 milliseconds skeletal muscles Smooth muscles varies Action potentials are short-lived and reset themselves quickly.

Question 35

What are the two distinct gates of voltage-gated sodium channels?

Answer 35

* Activation Gate * Inactivation Gate ## Footnote The activation gate is on the outside, while the inactivation gate is on the inside.

Question 36

What occurs in the resting state of voltage-gated sodium channels?

Answer 36

The activation gate is closed and the inactivation gate is open ## Footnote This allows the channel to be ready for depolarization.

Question 37

What happens during the activated/open state of voltage-gated sodium channels?

Answer 37

The activation gate swings open, allowing sodium to move through the channel ## Footnote This state is triggered by significant depolarization.

Question 38

What defines the inactivated state of voltage-gated sodium channels?

Answer 38

The inactivation gate closes, shutting off sodium flow ## Footnote The activation gate remains open initially, but the channel cannot open again until it resets.

Question 39

What must occur for a voltage-gated sodium channel to reset from the inactivated state?

Answer 39

The activation gate must close before the inactivation gate opens ## Footnote This prevents further sodium influx.

Question 40

What is the role of potassium channels in repolarization?

Answer 40

They increase cell membrane permeability to potassium ## Footnote This helps reset the cell faster after depolarization.

Question 41

What is the main difference in the gating of voltage-gated potassium channels compared to sodium channels?

Answer 41

Voltage-gated potassium channels have only one gate ## Footnote This gate is located on the inside of the cell and opens in response to depolarization.

Question 42

What is hyperpolarization (undershoot)?

Answer 42

A brief period where the membrane potential dips below the resting membrane potential ## Footnote This occurs due to prolonged potassium efflux.

Question 43

What are leaky channels?

Answer 43

Channels that are always open, maintaining resting membrane potential ## Footnote They include many leaky potassium channels and some leaky sodium channels.

Question 44

What primarily drives depolarization in action potentials?

Answer 44

Sodium influx ## Footnote Sometimes calcium influx also plays a role.

Question 45

What primarily facilitates repolarization during action potentials?

Answer 45

Increased potassium permeability ## Footnote This is crucial for returning to the resting state.

Question 46

What are the alternative names for the activation and inactivation gates?

Answer 46

* Activation Gate: M gate * Inactivation Gate: H gate ## Footnote These names are sometimes used interchangeably.

Question 47

What distinguishes slow calcium channels from fast sodium channels?

Answer 47

* Selected for calcium (Ca2+) * Slower to open and close ## Footnote Their timers are set differently, leading to a longer open duration.

Question 48

What effect do 'caine' drugs have on sodium channels?

Answer 48

They block fast sodium channels ## Footnote This prevents action potential generation and propagation.

Question 49

What is the primary effect of acetylcholine (ACh) in the heart?

Answer 49

Slows heart rate ## Footnote ACh binds to muscarinic acetylcholine receptors (mAChR) in the heart.

Question 50

What is the role of the vagus nerve in cardiac activity?

Answer 50

Releases acetylcholine to suppress cardiac activity ## Footnote This leads to hyperpolarization of cardiac cells.

Question 51

What factors influence action potential speed and efficiency?

Answer 51

* Neuron Diameter * Nerve Length * Insulation (Myelination) ## Footnote Larger diameters and robust myelination significantly improve speed.

Question 52

What is the role of myelin in the nervous system?

Answer 52

Prevents the loss of electrolytes and improves propagation speed ## Footnote It reduces energy consumption and enhances the efficiency of action potential propagation.

Question 53

What cells produce myelin in the CNS and PNS?

Answer 53

* Oligodendrocytes in the CNS * Schwann cells in the PNS ## Footnote Myelination in the PNS has greater plasticity and regenerative capacity.