The brain and hormonal control: exam questions

Answer: C (1) The medulla oblongata controls heart rate and breathing.

• similarity: both involve chemicals / act on effectors / target specific cells (1)
• nervous is fast, hormonal is slower (1)
• nervous transmitted by neurones (impulses), hormonal transmitted in the blood (1)
• nervous effects short-lived, hormonal effects longer-lasting (1)
• nervous acts on specific effectors, hormones act on any target cells with receptors (1)
• Max 4

• hypothalamus monitors blood / body conditions such as temperature or water content (1)
• hypothalamus produces releasing hormones / controls the anterior pituitary (1)
• hypothalamus makes ADH, which is released from the posterior pituitary (1)
• pituitary secretes hormones that act on target glands / tissues (1)
• so links the nervous and endocrine systems (1)
• Max 4

• (a) CT (1)
• quick / shows bleeding and bone / widely available in emergencies (1)
• (b) fMRI (1)
• detects changes in blood flow / oxygen use in active areas, as the patient performs the task (1)

• MRI gives more detailed images of soft tissue (1)
• so smaller tumours / their boundaries are seen more clearly (1)
• MRI uses no ionising radiation, so can be repeated safely; CT uses X-rays (1)
• MRI is slower, more expensive and less widely available than CT (1)
• MRI cannot be used for patients with a pacemaker / metal implants (1)
• reasoned conclusion, e.g. MRI is better for diagnosing and locating the tumour, but CT may be used when MRI is unavailable or unsafe for the patient (1)
• Max 5

• neurones that make dopamine (in the brain) are lost / die (1)
• so less dopamine is released at synapses / less transmission in the regions that control movement, causing tremor and rigidity (1)
• L-DOPA crosses the blood–brain barrier (dopamine cannot) (1)
• L-DOPA is converted to dopamine in the brain, restoring transmission (1)

• serotonin stays in the synaptic cleft for longer / concentration of serotonin in the cleft increases (1)
• serotonin binds to receptors on the postsynaptic membrane more often / for longer (1)
• so synaptic transmission is increased, which counteracts the low serotonin activity linked to depression (1)

• the cerebellum coordinates movement (1)
• and balance / posture, using information from muscles, joints and the ear (1)
• the motor areas of the cerebral hemispheres and the muscles are undamaged / muscles can still contract, so muscle strength is normal (1)