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Excretion & Coordination of Body Systems Workbook

Assignment 2 (CBH294, LO 3, 4)

Grade Descriptors 1, 3, 5, 7

TASK 1: ROLE OF LIVER IN EXCRETION (3.1)

Explain the role of the liver in the formation of urea (150 words).

TASK 2: THE KIDNEYS (3.1)

a) The diagram below shows a nephron and its blood supply.

On the diagram, use label lines and the letters provided to indicate an area where:

A ADH affects the permeability of cell membranes

B active transport of sodium ions occurs

C reabsorption of amino acids occurs

D there are podocyte cells

E the concentration of blood plasma proteins is highest.

b) Explain how the kidney removes urea from the blood without losing

essential nutrients such as glucose by answering the following questions:

(i) Explain the process of ultrafiltration making reference to the structure of

the filter (200 words).

(ii) Explain what happens to glucose in the proximal convoluted tubule and

how the tubules structure is adapted for its function (150 words).

(iii) Explain what happens to urea in the distal convoluted tubule to assist with

its removal from the kidneys.

TASK 3: BLOOD GLUCOSE REGULATION (4.2)

Produce an A3 poster explaining the regulation of blood glucose levels using negative feedback mechanisms.

TASK 4: COORDINATION OF DIGESTION (4.1)

a) Explain the role of the following two reflexes in the secretion of

saliva (250 words):

(i) Conditioned reflex

(ii) Unconditioned reflex

b) Explain the role of reflexes and hormones in the gastric phase of digestion (150 words).

c) Complete the following table contrasting the differences between nervous

and hormonal responses.

FEATURE

NERVOUS SYSTEM ENDOCRINE SYSTEM

Form of signal

Means of transmission

Effectors

Speed of response

Duration of response

d) Explain the advantages of coordinating digestion with both nervous and

hormonal responses (100 words).