The nurse assumes care of a patient who has myasthenia gravis and notes that a dose of neostigmine (Prostigmin) due 1 hour prior was not given. The nurse will anticipate the patient to exhibit which symptoms?

A) The cell body of the first motor neuron that lies in the brain stem:
This option refers to the somatic nervous system, which controls voluntary muscle movements. In response to a stressful or fearful situation, like the one described, the sympathetic nervous system is activated, not the somatic motor pathways. This is more related to voluntary motor control rather than the autonomic response to stress.

B) Reflex circuitry produced by the ANS reflex:
The autonomic nervous system (ANS) is involved in regulating involuntary functions like heart rate, blood pressure, and digestion. However, the "racing heart" response described here is primarily triggered by the sympathetic division of the ANS due to a stressor, such as seeing the cat. The reflex itself is part of a larger autonomic reaction, but the direct cause of the increased heart rate is the secretion of neurotransmitters.

C) Parasympathetic effect on the vagus nerve:
The parasympathetic nervous system (PNS) generally works to counteract the "fight or flight" response, promoting a relaxed state and slowing the heart rate. The vagus nerve is the primary parasympathetic pathway involved in decreasing heart rate. However, during stress or a fear response, the parasympathetic system is overridden by the sympathetic system, which increases heart rate, making this option incorrect.

D) Secretion of the sympathetic neurotransmitters produced in the adrenal medulla:
When a person experiences a stressor, like the sudden appearance of a cat, the sympathetic nervous system is activated, triggering the release of neurotransmitters like norepinephrine from sympathetic nerve endings and epinephrine (adrenaline) from the adrenal medulla. These chemicals act on the heart, causing it to race in response to the perceived threat.

A) Proteins:
Proteins are generally too large to diffuse freely across the cell membrane. They require specific transport mechanisms, such as endocytosis or transport proteins, to move in and out of cells. The hydrophilic nature of most proteins further complicates their passage across the lipid bilayer.

B) Enzymes:
Like proteins, enzymes are large molecules that do not freely diffuse across cell membranes. Enzymes, being proteins, also need specialized transport mechanisms or need to be secreted or endocytosed to enter or exit cells.

C) Hormones:
Many hormones, particularly lipid-soluble ones like steroid hormones, can diffuse freely across the cell membrane. These hormones pass through the lipid bilayer due to their hydrophobic nature and bind to intracellular receptors, initiating cellular responses. However, water-soluble hormones (e.g., insulin) typically do not diffuse freely but interact with receptors on the cell surface.

D) Electrolytes:
Electrolytes (such as sodium, potassium, calcium, and chloride ions) are charged particles that cannot pass freely through the lipid bilayer due to the hydrophobic interior of the cell membrane. They require specific ion channels or transporters to move in and out of the cell. Diffusion of electrolytes is facilitated through these channels, but it is not a simple diffusion process as seen with small, uncharged molecules.