1.Human anatomyMedium
Where does the spinal cord normally end in an adult?
- AAt the level of the sacrum
- BAt the coccyx
- CAt about the level of T10
- DAt about the level of vertebrae L1–L2
Anatomy and Physiology: cram pack
Formula sheets, the key method steps for every topic and 4 practice problems, with full solutions at the back.
1Practice problems
2.Human anatomyHard
After a difficult delivery with traction on the neck, a baby's arm hangs by the side, internally rotated with the forearm pronated ("waiter's tip"). Which part of the brachial plexus is injured?
- AUpper trunk (C5–C6)
- BPosterior cord
- CMedial cord
- DLower trunk (C8–T1)
3.Human physiologyMedium
Since action potentials are all-or-none, how does a neuron signal a stronger stimulus?
- ABy making each action potential longer
- BBy making each action potential larger
- CBy firing action potentials more often
- DBy changing the neurotransmitter it releases
4.Human physiologyHard
According to the length–tension relationship, why does a skeletal muscle fibre produce less force when overstretched?
- AThe muscle runs out of ATP when stretched
- BActin and myosin overlap less, so fewer cross-bridges form
- CThe neuromuscular junction stops working
- DCalcium is no longer released from the sarcoplasmic reticulum when stretched
2Solutions
1.Human anatomy
Answer: D · At about the level of vertebrae L1–L2
Why this is the answer
In adults the cord ends at the conus medullaris near L1–L2. Below that lies the cauda equina, which is why lumbar punctures are done at L3–L4 or L4–L5.
Answer
D · At about the level of vertebrae L1–L2
2.Human anatomy
Answer: A · Upper trunk (C5–C6)
Why this is the answer
Erb's palsy follows stretching of the upper trunk (C5–C6), paralysing deltoid, the external rotators and biceps. Lower trunk injury (Klumpke's) affects the small hand muscles instead.
Answer
A · Upper trunk (C5–C6)
3.Human physiology
Answer: C · By firing action potentials more often
Why this is the answer
Stimulus strength is coded by the frequency of action potentials and by how many neurons are recruited, not by their amplitude.
Answer
C · By firing action potentials more often
4.Human physiology
Answer: B · Actin and myosin overlap less, so fewer cross-bridges form
Why this is the answer
Maximum force occurs at an optimal sarcomere length with best filament overlap. Overstretching reduces overlap; too short a length makes filaments collide.
Answer
B · Actin and myosin overlap less, so fewer cross-bridges form
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