Question

6) a)i)sketch the pathway of air in the human respiratory system.(5marks) ii) Analyse air and water as respiratory medium in gas exchange.(5marks) lii))illustrate labelled phases of an action potential.(5marks) b)i)Prepare a labelled diagram of longitudinal section for both xylem and phloem in plant. (5marks) ii))illustrate the mechanism of autocrine and paracrine signaling. (5marks) lii))illustrate with a labelled diagram the sarcome structure structure during relaxation structure during relaxation and contraction. (5marks) C) i)Sketch a labelled diagram which explain how Auxin affects phototropism towards plant shoot. (5marks) ii)Explain with the aid of diagram the osmoregulation of fish in hyperosmotic condition. (5marks) lii)illustrate the labelled structure of mammalian respiratory system. (5 marks)

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Answer 1

##### Answer and Explanation #####

a. (i) Air pathway of human respiratory -  In the human body there are various systems playing their different kinds of roles, out of them Respiratory system is one of the important system which include the following parts with playing their role -

• Nose and nasal cavity - Sinsuses - Mouth - pharynx - Larynx - trachea - Diaphragm -Lung - Bronchial tubes/bronchi - Bronchioles - Alveoli - Capillaries.
• Air pathway - Nostril - Nasal Cavity - Pharynx - Larynx - Bronchus - Bronchiole - Lungs. (See the diagram).

2. Nasal Cavity 1. Nostrily Pharynx 4harynx -shing 6. Bronchus Bronchiole. fig- Pathway of air in of air in the human Respiratory System

(ii) Air and water as respiratory medium- During the respiration Water and gases work as respiratory agent where water helps the hemoglobin to be liquid hence it can flow from one place to the other places of the body, since water gases like Oxygen and Carbon- Dioxide can dissolve into water hence their transportation becomes easily. In this way with the help of CO2 and Oxygen are brought to the alveoli for exchange reultin exit and entry into the blood stream respectively.

(iii) Action Potential- These are the nerve signals which are conducted and generated by the neuron cells and proceeded to transmit to the target cell , where these can stimulated, inhibited or modulated in some of the way.

Since the process is based on the permeability of the membrane hence change in the concentration gradient keep occurring, due to the exchanges of ions in the cells on the basis of concentration gradient  there are Following stage of the action potential (See figure) -

+ 30 3. Overshoot 2. Depokrizations 4. Pepolarization Thresholtsst- Resting -70 ş. Hyperposanization. potential L. Hypopolarization Time fig - Action potential.

• Hypopolarization - It is the situation of initial increase of membrane potential due to the influx of ions.
• Depolarization - In this phase cell membrane gets more and more electro positive.
• Overshoot - After the situation of depolarization electropositive, gradient becomes at extreme, getting closure to the equilibrium of +61mV.
• Repolarization - After the phase of overshoot , high electrical positivity the channels close for the one ion (i.e Sodium Ion) while other channel open for other ion (Potassium ion) and efflux of potassium ions occurs finally cell membrane restores its resting membrane potential.
• Hyperpolarization - This situation leads to the cell more negative than the default cell due to the repolarization phase.

(iv) Longitudinal section of Xylem and pholem- Xylem and phloem are the complex tissues which help in the conduction of water and food translocation respectively. Xylem has four cells- tracheids, Vesels, Xylem parenchyma and Xylem sclerenchyma. While phloem has also four cells Vessels, Companian cells, phloem parenchyma and phloem sclerenchyma. Here the L.S of Xylem and phloem has been given (See the Figure).

1. Cell wall 3. Cell wall 4. Annulue eignin ENLINNASS I - Sieve peata Cell 2. well SASS 2. Spiral Phloem xylent lignin tudinal Section Xylemi

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