The Autonomic Nervous System and Its Two Outflows · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Your two autopilots for the organs

Science · The Human Body · ages 20-21
Name ______________________   Date ____________

  1. Which description correctly compares the locations of autonomic ganglia?

    • Sympathetic: near or within organs; parasympathetic: beside or in front of the spine
    • Sympathetic: within the brain and cord; parasympathetic: only in chains beside the spine
    • Sympathetic: beside or in front of the spine; parasympathetic: near or within organs

  2. Where do the sympathetic and parasympathetic preganglionic neurons originate?

    • Sympathetic: thoracic and upper lumbar cord; parasympathetic: brainstem and sacral cord
    • Sympathetic: brainstem and sacral cord; parasympathetic: thoracic and upper lumbar cord
    • Sympathetic: cervical and lower lumbar cord; parasympathetic: thoracic and upper lumbar cord

  3. At the heart, sympathetic beta-1 activation increases heart rate, while parasympathetic muscarinic activation decreases it.

    Circle one:   True   False

  4. A drug blocks alpha-1 receptors in the iris while sympathetic input is active. Which direct response is reduced?

    • Radial iris muscle contraction and pupil dilation
    • Circular iris muscle contraction and pupil constriction
    • Skeletal eye muscle contraction and rotation of the eyeball

  5. A drug selectively blocks beta-1 receptors in a heart with ongoing sympathetic drive. Which prediction fits its direct action?

    • Heart rate tends to increase; vascular alpha-1 receptors are not directly blocked
    • Heart rate tends to decrease; vascular alpha-1 receptors are not directly blocked
    • Heart rate tends to decrease; all vascular alpha-1 receptors are also directly blocked

  6. In the usual autonomic motor pathway from the brainstem or spinal cord to an organ, how many neurons form the chain? Count only the motor neurons.

    Answer: ______________

  7. Arterial pressure rises. Which sequence correctly identifies the sensor, integrator and an effector response in the baroreflex?

    • Aortic baroreceptors sense stretch; spinal circuits alone integrate; the heart slows
    • Aortic baroreceptors sense stretch; brainstem circuits integrate; the heart slows
    • Retinal photoreceptors sense pressure; brainstem circuits integrate; the heart slows

  8. A student assigns norepinephrine to both divisions at ganglia and organ targets. Which transmitter map corrects this? ACh means acetylcholine.

    • Ganglia: ACh in both; targets: sympathetic ACh, parasympathetic mostly norepinephrine
    • Ganglia: norepinephrine in both; targets: sympathetic mostly norepinephrine, parasympathetic ACh
    • Ganglia: ACh in both; targets: sympathetic mostly norepinephrine, parasympathetic ACh
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Your two autopilots for the organs W1-mt_bnVgu4T4E9-s1

  1. Sympathetic: beside or in front of the spine; parasympathetic: near or within organs · Sympathetic ganglia include chains beside the spine and prevertebral ganglia in front of it. Parasympathetic ganglia lie near or within target organs.
  2. Sympathetic: thoracic and upper lumbar cord; parasympathetic: brainstem and sacral cord · Sympathetic preganglionic neurons originate in the thoracic and upper lumbar spinal cord. Parasympathetic origins are the brainstem and sacral cord.
  3. True · These two inputs have opposing effects on heart rate through different target receptors.
  4. Radial iris muscle contraction and pupil dilation · Iris alpha-1 activation contracts radial muscle and dilates the pupil. Blocking these receptors reduces sympathetic dilation; it does not prevent every possible change in pupil size.
  5. Heart rate tends to decrease; vascular alpha-1 receptors are not directly blocked · Beta-1 blockade reduces sympathetic acceleration of the heart. Selective beta-1 blockade does not directly block vascular alpha-1 receptors or guarantee lower blood pressure.
  6. 2 · The usual motor chain contains one preganglionic neuron and one postganglionic neuron. Sensory neurons and integrating circuits are outside this count.
  7. Aortic baroreceptors sense stretch; brainstem circuits integrate; the heart slows · Aortic baroreceptors detect stretch, brainstem circuits integrate the signal, and the heart acts as an effector. Increased parasympathetic and reduced sympathetic output slow the heart.
  8. Ganglia: ACh in both; targets: sympathetic mostly norepinephrine, parasympathetic ACh · Both divisions use ACh in ganglia. At organ targets, most sympathetic postganglionic neurons release norepinephrine, while parasympathetic postganglionic neurons release ACh. Sympathetic nerves to most sweat glands are an exception.
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