Practice IB Biology Topic C3.1 Integration of Body Systems with authentic exam-style questions for both SL and HL students. This question bank focuses on the exact syllabus content for C3.1 Integration of Body Systems and mirrors Paper 1A, 1B, 2 style where relevant.
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Two responses followed the same stimulus. Which signalling routes are supported?
A skin receptor was stimulated; the CNS and muscle remained functional. Which pathway assignment is supported?
| Blocked pathway | Impulse reaches CNS | Muscle contracts |
|---|---|---|
| P | no | no |
| Q | yes | no |
| Response | Onset time | Duration | Distribution | Intervention that abolishes response |
|---|
| P | 0.04 s | 0.3 s | one muscle | voltage-gated Na⁺ channels blocked at one local site |
| Q | 40 s | 60 min | six tissues | the same membrane receptor blocked in all six tissues |
Four cardiac preparations were tested. Which inference about biological organization is supported?
| Preparation | Structure | Observed function |
|---|---|---|
| P | one cardiac muscle cell | contraction; no fluid movement |
| Q | layer of similar cardiac muscle cells | synchronized contraction; no directional flow |
| R | chamber of muscle, epithelial and connective tissues with valves | directional fluid flow |
| S | R connected to vessels and lungs | gas transport between organs |
Which identification and consequence of removing Q from selected fibres are supported?
Recordings were made from the same peripheral nerve during two treatments. Which structural conclusion is supported?
| Treatment | Recorded impulse direction |
|---|---|
| Stimulate skin receptor | Towards CNS |
| Stimulate motor area of CNS | Towards skeletal muscle |
P is endocrine through blood; Q is nervous along neurons
P is nervous along neurons; Q is endocrine through blood
P and Q are both endocrine through blood
P and Q are both nervous along neurons
P is sensory, receptor to CNS; Q is motor, CNS to muscle
P is motor, CNS to muscle; Q is sensory, receptor to CNS
P and Q are both sensory pathways to the CNS
P and Q are both motor pathways from the CNS
