Neurons, Synapses, Muscles, and Movement - QUIZ

Question 1

Explain the role of the sodium potassium pump in maintaining the resting potential of a neuron.

Answer 1

• Pumps NA+ ions out of axon and potassium ions K+ in
• Requires ATP for active transport
• 3 sodium out every 2 potassium in
• Results in charge differences, outside is positive relative to inside

Question 2

define resting potential

Answer 2

• the difference in charge across the membrane when a neuron is not firing (-70mV)

Question 3

Neuron at rest

Answer 3

• Inside more negative due to more K+
• Outside more positive due to more NA+

Question 4

define Action potential

Answer 4

nerve impulse is generated and propagated (sent) down the axon

Question 5

Explain the events of a nerve impulse and how it is propagated down the axon.

Answer 5

• Nerve impulse are action potentials propagated along axons of neurons
• Resting potential is -70mV (maintained by NA+/K+ pumps)
• More sodium outside than inside at rest
• Action potential stimulates depolarization along axon
• If threshold potential is reached, NA+ channels open and sodium ions diffuse inside
• potassium channels open and K+ ions move out (causing re-polarization)
• Myelination increases propagation speed (saltatory conduction)

Question 6

Myelin sheath

Answer 6

increases the speed of the signal along axon - saltatory conduction

Question 7

Explain the steps of synaptic transmission

Answer 7

• Nerve impulse arrives
• Calcium channels open and calcium diffuses in
• Structures containing neurotransmitter fuse with membrane
• Neurotransmitter released by exocytosis into cleft and binds to receptors

Question 8

Explain the steps involved in synaptic transmission (at the neuromuscular junction) when ACh (acetylcholine) is the neurotransmitter.

Answer 8

-ACh binds to receptor protein
- Causes change in tertiary structure of protein
- Diffusion of ions is then allowed
- Acetylcholinesterase breaks down acetylcholine into acetyl and choline

Question 9

Explain neonicotinoid pesticides

Answer 9

• They irreversibly bind with acetylcholine receptors on postsynaptic membrane
• Enzymes cannot break down neonicotinoids
• Synaptic transmission prevented
• Causing paralysis / death (of insect)

Question 10

Explain muscle contraction

Answer 10

• Happens in sarcomeres located in myofibrils
• Sarcomeres shorten during muscle contraction
• Nerve impulses stimulate contraction
• Calcium ions released into sarcoplasmic reticulum
• Calcium bins to troponin
• Troponin causes tropomyosin to expose binding sites on actin
• ATP provides energy for myosin heads to bind with actin
• Myosin filaments pull actin towards center of sarcomere
• ATP causes binding to break

Question 11

Explain structure of skeletal muscle

Answer 11

Largest to smallest:
muscle, muscular bundle, muscle fiber, sarcolemma, myofibril, sarcomere

Question 12

Explain structures / functions of the elbow joint

Answer 12

Biceps - contract for flexion
Triceps - contract for extension
Humorous - upper bone, leverage for upper elbow muscles
Cartilage - absorbs shock, allows bone to move smoothly
Synovial fluid - provides nutrients to cartilage; reduces friction

Question 13

relative concentrations of sodium and potassium inside and outside of a neuron when it is “at rest”

Answer 13

• Positive outside (more sodium)
• Negative inside (more potassium)