Lecture Week 10

Question 1

What is neuromuscular junction?

Answer 1

Location where the axon of a motor neuron comes into close contact with the sarcolemma of a muscle fiber and may stimulate that fiber to contract

Question 2

What is a synaptic cleft?

Answer 2

Space between neuron and muscle fiber plasma membranes

Question 3

What are synaptic vesicles?

Answer 3

In motor neuron containing ACh (acetocholine)

Question 4

What is the motor end plate?

Answer 4

Sarcolemma in NMJ

Question 5

What does the motor unit consist of?

Answer 5

Muscle fibers stimulated by single motor neuron
-motor units with fewer fibers allow for more precise control of contraction strength
ex. extrinsic eye muscles have few fibers per motor unit = precise control
ex. hamstring muscle have many fibers per motor unit = not as much precision

Question 6

Nerve and Muscle Impulse Transmission

Answer 6

Nerve cells (neurons) and muscle fibers transmit impulses along plasma membranes
-allows for communication in body

Question 7

Distribution of Ions

Answer 7

-Neurons and muscle fiber plasma membranes are polarized - inside more negative charge, outside more positive charge
-cations positively charged (Sodium major extracellular ion, Potassium major intracellular ion)
-anions negatively charged (amino acids and proteins)

Question 8

Membrane Potentials

Answer 8

Difference in charge across a cell membrane
Resting potential -70mV
Threshold Potential -55mV

Question 9

Channel “Gate” Proteins

Answer 9

Substances move through channels
-chemical gated sodium channels - located at neuromuscular junctions (motor end plate), open when ACh binds which allows sodium into cell
-voltage-gated channels - found all along sarcolemma, open when membrane potential changes to specific value –> voltage gated sodium channels open at threshold potential -55mV, voltage gated potassium channels open when polarity undergoes a reversal +20mV

Question 10

Steps leading to a muscle impulse

Answer 10

1. ACh binds to and opens chemically gated Na+ channels, Na+ diffuses into the cell
2. if the membrane potential changes from resting to threshold.. action potential occurs
   —-voltage gated Na+ channels open, depolarization leads to charge reversal, voltage gated Na+ channels close and voltage gated K+ channels open, repolarization leads to resting potential
3. action potential at one spot of membrane stimulates action potential at adjacent spots
4. traveling action potential is called an impulse
   Na+/K+ pumps restore original ion distribution

Question 11

What is the definition of cellular respiration?

Answer 11

Cellular process in which energy is harvested from nutrients like glucose and used to produce ATP (adenosine triphosphate)
–about 40% of glucose is transferred to ATP, other 60% of energy is released as heat
ADP + P –> ATP

Question 12

Cellular Respiration Stages

Answer 12

Anaerobic (without oxygen gas) portion
1. glycolysis
Aerobic (with oxygen gas) portion
1. acetyl coenzyme A formation
2. citric acid cycle (krebs cycle)
3. oxidative phosphorylation

Question 13

Oxidation

Answer 13

loss of electrons during a reaction

Question 14

Reduction

Answer 14

gain of electrons during a reaction

Question 15

ATP synthase

Answer 15

enzyme that produces ATP as H+ move through it

Question 16

Chemiosmotic ATP synthesis

Answer 16

production of ATP fueled by the movement of H+ down their concentration gradient

Question 17

Anaerobic ATP Synthesis (Fermentation)

Answer 17

-in the absence of oxygen, ATP is produced using just glycolysis
-pyruvate converted into lactate in order to regenerate NAD+
-lactate build up causes muscle pain and eventually interferes with ATP synthesis
-fermentation is only 5% as efficient as aerobic CR but is 2.5x faster

Question 18

Obtaining Energy from Nutrients

Answer 18

Carbohydrates
-digestion produces monosaccharides
-nonglucose monosaccharides are converted into glucose
Proteins
-digestion produces amino acids
-amino acids are deaminated and converted into pyruvate, acetyl CoA, or intermediates in the citric acid cycle
Triglycerides
-digestion produces glycerol and fatty acids
-glycerol is converted into pyruvate
-fatty acids are used to make numerous acetyl CoA

–components of proteins and triglycerides do not go through glycolysis