Thoracic Surgery

• Cholinergic Neurotransmission:
• In cholinergic presynaptic terminals, the rate-limiting step in acetylcholine synthesis is the reuptake of choline from the extracellular fluid.
• Choline is transported across the presynaptic axolemma by a high-affinity, sodium-dependent Choline Transporter (CHT1).
• This transporter is specifically and potently blocked by Hemicholinium (Hemicholinium-3), depleting intracellular choline and halting acetylcholine synthesis.
• (Vesamicol blocks vesicular acetylcholine uptake; Reserpine blocks vesicular monoamine transport).
• nalysis:
• (Hemicholinium): Correct.

Correct option: (2) Hemicholinium

• Central Neurotransmission of Acetylcholine (ACh):
• In the central nervous system, acetylcholine acting on muscarinic receptors ($M_1$ subtype) produces slow, prolonged excitatory postsynaptic potentials (EPSPs).
• The biochemical mechanism involves $G_q$-protein activation, which closes voltage-gated potassium channels (the M-current / $I_M$), causing a decrease in potassium conductance ($g_{K^+}$).
• Decreased outward $K^+$ efflux leads to membrane depolarization and sustained neuronal excitation.
• (GABA and Glycine increase chloride conductance; Dopamine acts through D1/D2 GPCRs).
• nalysis:
• (Acetylcholine): Correct.

Correct option: (4) Acetylcholine

• Copulatory Mechanics of the Ram:
• The ram (Ovis aries) possesses a slender, filiform appendage (urethral process / vermiform appendage) measuring $4 - 5\text{ cm}$ that projects beyond the glans penis.
• During rapid copulation ($\lt 1\text{ second}$), the urethral process undergoes violent, rapid rotation (oscillating up to 60 times per second), spraying semen in a wide circular pattern across the external os of the cervix.
• This physiological phenomenon is famously termed the "Fire hose effect".
• nalysis:
• (Ram): Correct species.

Correct option: (3) Ram

• Total Spermatozoa per Ejaculate in Domestic Animals:
• Boar: Characterized by massive ejaculate volume ($150 - 300\text{ ml}$) and high total sperm count:

(Highest absolute sperm output per single ejaculation among domestic mammals).

• Stallion: $50 - 100\text{ ml}$, $5 - 10\text{ billion sperm}$.
• Bull: $4 - 8\text{ ml}$, $4 - 8\text{ billion sperm}$.
• Ram: $0.8 - 1.2\text{ ml}$, $2 - 4\text{ billion sperm}$ (highest concentration, but low volume).
• nalysis:
• (Boar): Correct.

Correct option: (4) Boar