Home / iGCSE Biology (0610)-14.1 Coordination and response – iGCSE Style Questions Paper 4

iGCSE Biology (0610)-14.1 Coordination and response – iGCSE Style Questions Paper 4

IGCSE Biology (0610) Practice Questions Paper 4 - All Chapters
Question

Fig. 3.1 is a diagram of the junction between two neurones in a healthy person.

Fig. 3.2 is a diagram of the junction between the same two neurones in a person who has Parkinson’s disease. This disease affects the nervous system.

 

(a) Identify the parts labelled X and Y in Fig. 3.2.

(b) Parkinson’s disease affects neurones in the brain that are responsible for movement.

Using the information in Fig. 3.1 and Fig. 3.2, suggest and explain the effect of Parkinson’s disease on a person’s movement.

(c) Describe two ways nervous control differs from hormonal control.

(d) (i) The shape of the receptor proteins shown in Fig. 3.1 and Fig. 3.2 is important for their function.

Explain how the shape of the receptor proteins is determined.

(ii) Cell membranes also contain protein carriers. Describe the role of protein carriers.

▶️ Answer/Explanation
Solution

(a) X – vesicle (membrane); Y – synapse/synaptic gap

Explanation: In Fig. 3.2, X represents the membrane-bound vesicles that contain neurotransmitters, which are crucial for signal transmission between neurones. Y is the synaptic gap, the physical space between two neurones where neurotransmitters diffuse to carry the signal from one neurone to the next.

(b)

Explanation: Parkinson’s disease significantly impairs movement due to several neurological changes:

  1. Movement becomes slower and less coordinated because there are fewer vesicles containing neurotransmitters.
  2. The reduced number of neurotransmitters means fewer signals are transmitted across the synaptic gap.
  3. With fewer neurotransmitters binding to receptor proteins, the postsynaptic neurone receives weaker signals.
  4. This results in slower reflexes and difficulty initiating or controlling movements.
  5. The overall effect is impaired motor function, characteristic of Parkinson’s symptoms like tremors and rigidity.

(c)

  1. Nervous control is much faster than hormonal control, with responses occurring in milliseconds compared to seconds or minutes for hormones.
  2. Nervous control is localized to specific areas through neural pathways, while hormonal control has widespread effects throughout the body via the bloodstream.

Explanation: The nervous system uses electrical impulses that travel quickly along neurones, allowing for rapid responses. In contrast, hormones are chemical messengers that travel through the blood, resulting in slower but more sustained effects. Additionally, nervous control targets specific muscles or glands, whereas hormones can affect multiple target organs simultaneously.

(d)(i)

Explanation: The shape of receptor proteins is determined by:

  1. The specific sequence of bases in the gene/DNA that codes for the protein.
  2. This DNA sequence is transcribed into mRNA and translated into a specific sequence of amino acids.
  3. The amino acid sequence then folds into a unique three-dimensional shape that determines the protein’s function.
  4. This precise shape allows the receptor to bind specifically to certain neurotransmitters.

(d)(ii)

Explanation: Protein carriers in cell membranes have crucial roles:

  1. They actively transport specific molecules or ions across the membrane against concentration gradients.
  2. This process requires energy from ATP produced during respiration.
  3. They enable the movement of substances that cannot diffuse freely through the membrane.
  4. Examples include transporting glucose into cells or pumping sodium and potassium ions in nerve impulses.
Question

(a) Complete the sentence about the mammalian nervous system:

The ………………………………………….. nervous system consists of the brain and spinal cord, and the ………………………………………….. nervous system consists of the nerves outside the brain and spinal cord.

(b) Fig. 4.1 shows the parts of a reflex arc.

(b)(i) Put the parts listed in Fig. 4.1 into the correct sequence, and write the letters in the boxes. Two have been done for you.

(b)(ii) State two stimuli that are detected by the skin.

(b)(iii) The pupil reflex controls the amount of light that enters the eye.
State the name of an effector in the pupil reflex.

(c) Describe and explain how impulses are only passed in one direction from one neurone to the next.

▶️ Answer/Explanation
Solution

(a) The central nervous system consists of the brain and spinal cord, and the peripheral nervous system consists of the nerves outside the brain and spinal cord.

(b)(i) Correct sequence:

Pathway: Stimulus → Receptor → Sensory neurone → Relay neurone → Motor neurone → Effector → Response.

(b)(ii) Two stimuli detected by skin:
1. Temperature changes (heat/cold).
2. Pressure/touch.

(b)(iii) Effector in pupil reflex: Circular muscles or radial muscles of the iris.

(c) Unidirectional impulse transmission occurs because:
1. Neurotransmitters are only released from the presynaptic neurone.
2. Receptors are only present on the postsynaptic neurone.
3. Synaptic vesicles fuse with the presynaptic membrane to release neurotransmitters into the synaptic cleft.
4. Neurotransmitters bind to complementary receptors, triggering an impulse in the next neurone.

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