Challenge yourself answers

Solution B, negative; or Solution A, positive

150 mmol/L urea

Increases

Upstroke of the action potential

25 quanta

Botulinus toxin

Action potential in nerve fiber; opening Ca ²⁺ channels in presynaptic terminal; ACh release from presynaptic terminal; binding of ACh to nicotinic receptors; opening ligand-gated ion channels; MEPP; EPP; action potential in muscle fiber

Approximately equal to (Hint: Passive tension is negligible in this range.)

Substance P, vasopressin

Double (Hint: ΔC = 10 − 1 = 9. If both sides doubled, ΔC = 20 − 2 = 18.)

l -Dopa, dopamine, norepinephrine

Increasing nerve diameter: increases; increasing internal resistance (R _i ): decreases; increasing membrane resistance (R _m ): increases; decreasing membrane capacitance (C _m ): increases; increasing length constant: increases; increasing time constant: decreases.

Depolarizes; causes muscle weakness by closing inactivation gates on Na ⁺ channels so that they are unavailable to carry Na ⁺ current for upstroke of muscle action potential

Conformational change in myosin that reduces its affinity for actin

Nicotinic receptor antagonist; inhibitor of choline reuptake; inhibitor of ACh release

Water flows from A to B. (Hint: Calculated π _eff of Solution B is higher than that of Solution A, and water flows from low to high π _eff .)

E _K ⁺ is more negative than Em, so K ⁺ “wants” the membrane potential to be more negative than it is. To accomplish this, K ⁺ would move out of the cell = outward current. E _Cl ⁻ is less negative than Em, so Cl ⁻ “wants” the membrane potential to be less negative than it is. To accomplish this, Cl ⁻ would move out of the cell = inward current. (Note that, for Cl ⁻ , negative charge moving out of the cell is the equivalent of positive charge moving into the cell, which is called inward current.)

Dilation of airways; relaxation of bladder wall

Muscarinic; sphincter

Ganglia in or near target tissues (Hints: All postganglionic neurons have nicotinic receptors; sweat glands have sympathetic cholinergic innervation; all preganglionic neurons are cholinergic.)

Inhibits (or blocks); β ₁ receptors

Effect of epinephrine to increase cardiac contractility; effect of epinephrine to increase heart rate

Phenylethanolamine- N -methyltransferase

α ₁ -Adrenergic agonist (would constrict vascular smooth muscle, further elevating blood pressure); β ₁ -adrenergic agonist (would increase heart rate and contractility, further elevating blood pressure)

Muscarinic, contraction, muscarinic, relaxation

α _q binds to GDP, α _q binds to GTP, activation of phospholipase C, generation of IP ₃ , release of Ca ²⁺ from intracellular stores, activation of protein kinase

Slowing of conduction velocity in AV node; gastric acid secretion; erection; sweating on a hot day

Right optic nerve

To the left (Hint: Postrotatory nystagmus is in the opposite direction of the original rotation.)

One

Knee-jerk reflex; stretch reflex (Hint: Knee-jerk is an example of stretch reflex.)

Phasic

Light; conversion of 11- cis rhodopsin to all- trans rhodopsin; transducin; decreased cyclic GMP; closure of Na ⁺ channels; hyperpolarization; release of neurotransmitter

More negative; decreases likelihood of action potentials

Golgi tendon organs: activated

• Ia afferent fibers: unchanged (Hint: Ia afferents are involved in the stretch reflex.)

• Ib afferent fibers: activated

• Inhibitory interneurons: activated

• α Motoneurons: inhibited

Protein; glucose; K ⁺

Initial rotation to the right—right canal is activated; head stops rotating—left canal is activated.

Wider; more compliant; lower