Frog Heart Lab

Question 0

What happens when the temp of the heart is dramatically decreased?

Answer 0

Hr decreases bc the cold decreases the membrane permeability bc membranes are made of phospholipids and lipids are less malleable in cold

Question 1

Effect of caffeine

Answer 1

Causes an increase in sensitivity of the myocardial actin filaments to calcium, which increases the contractile properties of the heart

Question 2

What causes an increase in membrane permeability?

Answer 2

Increased temp

Question 3

How would injecting a solution differ from dropping it onto a frog heart?

Answer 3

Injected solution would travel through the entire circulatory system including diffuse more thoroughly through the heart and also have an effect on the neurological stimulation pathways. Solution dropped on the heart muscle would only be able to affect the cells it contacted directly.

Question 4

What neurotransmitter chemical is secreted by the parasympathetic vagus nerve?

Answer 4

Ach

Question 5

What nerve decreases the heart rate and what neurotransmitter chemical does it release?

Answer 5

The vagus nerve releases Ach.

Question 6

How does release of Ach at the cardiac myofiber affect hr?

Answer 6

Ach hyper polarizes the cardiac myofiber making it more difficult to contract (because more depolarizing ion movement is required to reach AP threshold) and this slows down the HR

Question 7

What are the three types of extrinsic stimulation for the heart?

Answer 7

Parasympathetic stimulation (vagus nerve, Ach, decreases HR)
Sympathetic stimulation (cardiac nerves, epi released and HR increases)
Hormonal stimulation (epinephrine and norepinephrine secreted by adrenal medulla in response to increased stress, physical activity and emotional excitement)

Question 8

What do the cardiac nerves innervate?

Answer 8

Siniatrial, and atrioventricular nodes, atrial and ventricular myocardium, coronary vessels

Question 9

What neurotransmitter chemicals are released by the sympathetic nervousness system.

Answer 9

Epinephrine and norepinephrine

Question 10

Which branch of the nervous system releases preganglionic Ach and postganglion Ach?

Answer 10

Parasympathetic

Question 11

The sympathetic nervous system utilizes which neurotransmitter chemicals and where?

Answer 11

Ach at the ganglion

Epi at the cardiac myofiber

Question 12

What is the limitation to increasing a HR?

Answer 12

The heart has to have time to fill

Question 13

From what stimulation points can the hr be increased by Epi?

Answer 13

The sympathetic cardiac nerves and hormonal control by the adrenal medulla

Question 14

Describe a cardiac muscle cell

Answer 14

Found only in heart
Striated
Usually only 1 nucleus
Intercalated disks and gap junctions
Auto rhythmic cells
Action potentials of longer duration and longer refractory period
Ca++ regulates cntx

Question 15

How does temperature affect the enzymes of the muscle contractions

Answer 15

At warmer temperatures, enzymes (acetylcholinesterase, in this case) work faster, at colder temperatures, enzymes work slower

Question 16

How would Ach act differently if injects vs dropped?

Answer 16

When dropped, it will act like the parasympathetic stimulation that releases Ach at the muscle fiber and decrease HR
when injected, it will also affect the nerves supplying the heart and will give both an increase and decrease reactions since the Ach will reach both the nervous stimulation and the individual fibers