excitation contraction

Question 1

c. Motor unit

Answer 1

one ventral horn nerve cell and all of the muscle fibers

Question 2

skeletal muscle contracts under nervous controls and is organized in ____ each with it’s own ______

Answer 2

i. Organized in long straight parallel fibers. Each fiber has its own synapse

Question 3

Motor neurons are located in the

Answer 3

b. Motor neurons in anterior horns of the spinal cord

Question 4

smaller muscles have more or less motor units?

Answer 4

ii. Smaller muscles (like in our hands) have the most motor units and are best for dexterity
i. If a muscle has smaller but more numerous motor units, its capable of more different types of speeds and strengths of contraction

Question 5

Synapse on muscle fiber occurs at the _ where nerve and muscle come together

Answer 5

Synapse on muscle fiber occurs at the _ where nerve and muscle come together

Question 6

another name for the post-synaptic membrane

Answer 6

b. Post-synaptic membrane, also called the motor end plate

Question 7

Invagination of muscle membrane, also called the ________

Answer 7

c. Invagination of muscle membrane, also called the synaptic gutter

Question 8

a. Nerve terminals descend into the muscle fiber but lie outside the plasma membrane which is also known as the

Answer 8

sarcolema

Question 9

sub-nueral folds do what for the membrane

Answer 9

d. Sub-neural folds increase surface area

Question 10

NT at motor neuron synapse

Answer 10

Ach

Question 11

Ach is housed in these structures before it’s release in the NMJ

Answer 11

vesicles there are approximately 125
and they are released in response to the influx of Ca at the axon terminal which occurs after the transmission of a nerve impulse

Question 12

Ach Binds Ach receptor on motor end plate/postsynaptic membrane and binds to the receptors

Answer 12

a. Binds Ach receptor on motor end plate/postsynaptic membrane and binds to the receptors

Question 13

Chemically gated channels on the motor end plate require binding of how many NT in order to open the channel

Answer 13

c. Chemically gated channels requiring binding of 2 Ach molecules to the external surface in order to open the channel

Question 14

what happens after AcH binds at the motor end plate

Answer 14

when it opens, you have a flux of Na/K down their concentration gradient (so Na is entering the cell and K is leaving)

Question 15

how does the membrane potential differ in the motor end plate compared to the axon

Answer 15

b. EPPs normally increase membrane potential 50-75mV, more than enough to pass threshold to trigger Ap
b. Resting muscle membrane potential (-80-90mV) has a larger “pull” on sodium

Question 16

where do we get choline in the NMJ

Answer 16

breakdown from cholinesterase

Choline is then actively transported back into the presynaptic neuron and can repackaged as Ach again

Question 17

Autoimmune disease in which autoantibodies destroy Ach receptors.

Answer 17

VIII. Myasthenia Gravis

Question 18

what type of channels do we have at the NMJ

Answer 18

chemically gated channel that requires bdining of 2 Ach molecules and is a positive ion channel

5 subunits

alpha beta 2 gamma and delta)

Question 19

resting membrane potential of the muscle cell

Answer 19

-80 to 90

biggest player is sodium

Question 20

EPP trigger

Answer 20

AP

botulism toxin and curare interferes with this

Question 21

t tubules in cardiac and skeletal

Answer 21

only 1 t tubule in cardiac

2 in skeletal

Question 22

muscle stays contracted as long as

Answer 22

there is calcium present in the sarcomere

Question 23

how does atrophy of a muscle occur

Answer 23

lack of innervation

lack of activity

Question 24

dystophies

Answer 24

genetic disorders

cause combination of atrophy
hypertrophy or pseudo hypertrophy and necrosis of muscle tissue depending on the pescific defect

insidious progressive disorders with the primary symptom being weakness

Question 25

pseudo hypertrophy

Answer 25

fat and fibrosis

Question 26

duchenne MD what is it

Answer 26

Hertible absence of dystrophin that is required for muscle structure

Question 27

prevalence in Duchenne MD

Answer 27

males and females have 50%

Question 28

prognosis of duchenne MD

Answer 28

progressive weakness leading to paralysis in 3-5 years
most loose the ability to walk by 12

usually heart and breathing muscles get weak and cause pneumonia or heart failure

Question 29

becker MD

Answer 29

similar but less severe

pt produces dystrophin but it is not fully fucntional

Question 30

fascioscapulohumeral MD

Answer 30

progressive disorder seen in adults

MC form is myotonic seen with cataracts and cardiac abnormalities

Question 31

loss of trophic effect of lower motor neuron is characteristic of

Answer 31

Denervation atrophy

Question 32

• slowly progressive disorder of face, arms, shoulder beginning in teens

Answer 32

a. Fascioscapulohumeral MD

Question 33

MC adult form characterized by cardiac abnormalities and cataracts, swan neck (from inability to support the weight of the head), drooping eyelids

Answer 33

b. Myotonic adult MD