Theory question 107
Nervous Coordination(a) Name three main parts of the human brain.
(b) State the functions of the following:
(i) Cerebrum; (ii) Hypothalamus; (iii) Medulla Oblongata.
(c) (i) List three organs of a higher plant that can respond to stimulus.
(ii) What is tactic movement?
(d) Explain the following terms, giving one example in each case:
(i) Phototaxis; (ii) Hydrotaxis; (iii) Chemotaxis.
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(a) Fore brain (cerebrum, thalamus, hypothalamus); mid brain; hind brain (cerebellum, medulla oblongata).
(b)(i) Cerebrum: controls thinking, intelligence, memory, learning, speech and voluntary actions; receives and interprets sensations (sight, hearing, touch).
(ii) Hypothalamus: controls body temperature, water balance, hunger and thirst; links the nervous system with the pituitary gland.
(iii) Medulla oblongata: controls involuntary actions such as breathing rate, heartbeat, blood pressure, swallowing, coughing and sneezing.
(c)(i) Any three: shoot/stem; root; leaf; tendril; flower (e.g. petals opening).
(ii) A tactic movement is the movement of a whole organism (or a free-moving cell) from one place to another in response to a directional stimulus, towards it or away from it.
(d)(i) Phototaxis: movement of a whole organism in response to light, e.g. Euglena or Chlamydomonas swimming towards light.
(ii) Hydrotaxis: movement in response to water or moisture, e.g. woodlice or earthworms moving to damp places.
(iii) Chemotaxis: movement in response to chemicals, e.g. sperm of mosses/ferns swimming towards chemicals from the archegonium; bacteria moving towards food.
Taxis is movement of the whole organism; do not confuse it with tropism (growth of part of a plant).