Tutoring1

Question 1

Why is the action potential uni-directional?

Answer 1

• Na+ channel inactivation prevents antidromic (or back) propagation in the AXON
• also limits the frequency of APs an axon can carry because of absolute and relative refractory period

Question 2

Puffer fish toxin vs. Scorpion venom

Answer 2

Look up

Question 3

Events of AP

Answer 3

Look up

Question 4

Why do TCAs and cocaine cause cardiotoxicity?

Answer 4

Blockage of sodium channels

Question 5

Define Threshold:

Answer 5

Threshold = -INa+ + IK+ = Zero

Question 6

Specific __ can opened or closed by transmitters that will alter the threshold for firing of a neuron

Answer 6

K+ channels

Question 7

Patient labs show hyperkalemia and this makes you worry about the effect of potassium on the heart. Why are you not worried about the effects of potassium on the brain?

Answer 7

cerebrospinal fluid (CSF) [K+] is kept lower and remains relatively constant even during hypokalemia and hyperkalemia

Question 8

changes in CSF [K+] would otherwise change CNS neuron ___(e.g., cause seizures etc).

Answer 8

Vm and excitability

Question 9

CAPACITOR. What part of the neuron is this?

Answer 9

Membrane

Question 10

RESISTOR what part of the neuron is this?

Answer 10

Channels

Question 11

Define length constant

Answer 11

The distance V has decayed to 37% of its value at the point of injection defines the length constant, and has values of 1-2 mm in neurons

Question 12

What two entities can cause the length constant to increase?

Answer 12

length constant increases with increase in rm and decrease in ri according to the relation
length constant = √rm/ri

Question 13

What is the time constant equation?

Answer 13

Time constant= RmCm

The time constant, is the time it takes to reach 63% of the final voltage or decay back to 37% of its value

Question 14

ANS
Parasympathetic
1. Pre-ganglion neurotransmitters

2. Post-ganglion neurotransmitters

Answer 14

1. Pre-ganglion neurotransmitters
   Ach – Nicotinic
2. Post-ganglion neurotransmitters
   Ach- Muscarinic

Question 15

ANS
Sympathetic
1. Pre-ganglion neurotransmitters

2. Post-ganglion neurotransmitters
3. Exceptions:

Answer 15

1. Pre-ganglion neurotransmitters
Ach-Nicotinic
2. Post-ganglion neurotransmitters
Nor/Epi – Adrenegic
Exceptions:
Sweat glands. Adrenal medulla.

Question 16

A man is confronted by a wild bear.  He notices his heart rate is 120 bpm.   What signal origin is responsible for his increased HR?
A) CN X
B) CN IX
C) T1-L3
D) S2-S4
E) CN III
F) CN VII

Answer 16

Sympathetic ganglion spans T1-L3

Question 17

T5-T12 gives sympathetic to

Answer 17

gut viscera

Question 18

L1-L3 offers sympathetic to

Answer 18

bowel and bladder.

Question 19

Cholinergic receptors:

- Nicotinic: excited by ___ and blocked by __

Answer 19

Nicotinic: excited by nicotine and blocked by curare

Question 20

Cholinergic receptors:

- Muscarinic: excited by __ and blocked by ___

Answer 20

Muscarinic: excited by muscarine and blocked by atropine

Question 21

Adrenergic receptors:

Answer 21

alpha and beta