Biol 121 questions answers PDF

Preview

Summary

Answers to written assignment grade HD...

Description

Na me : St u d e n t n u mb e r :

BIOL121 WORKSHEET Due: 3am Wednesday 8th May Submit: via Turnitin link on BIOL121 LEO page Weighting: 20% final grade Answers must be in an easy to read colour that is distinctly different to black. QUESTION 1 Which type of immunity is expressed in the following scenarios? Choose between:   

Non-specific (first line defence) Specific (antibody-mediated) Specific (cell-mediated immunity)

(0.5 mark each – total 2 marks)

Scenario Bacterial septicaemia (bacterial contamination in systemic circulation)

Type of immunity Specific Antibody Mediated

The pH of hydrochloric acid in the stomach acts to destroy ingested bacteria

Non-Specific (first line)

A liver cell mutates and becomes cancerous

Specific Cell Mediated

A virus multiplies inside the epithelial cells in your throat.

Specific Cell Mediated

QUESTION 2 Choose TWO of the below scenarios and highlight these rows bold. State which general property of adaptive immunity the scenario illustrates in the second column. Select ONE phrase (from the list below) that BEST describes what is happening at a cellular level to result in this property of adaptive immunity. Write the letter corresponding to this phrase in the third column. An example is included. (2 mark) Scenario

General property of immunity

Even though your body contains a relatively small number of lymphocytes, your immune system can mount a response against almost any antigen it encounters.

Explanatio n

Versatility

A

Generally, after an initial infection, subsequent immune responses to that antigen are faster, stronger and more sustained.

Memory

C

You can suffer from ‘the flu’ multiple times throughout your lifetime.

Specificity

B

Your immune system can distinguish between antigens on your own cells, and those of an invading pathogen.

Possible phrases are listed below. Not all phrases will need to be used and only ONE phrase is required per row. If you record more than one, you will not be awarded any marks for your explanation. A

There are millions of different lymphocyte populations, each of which is sensitive to a different antigen. Lymphocytes proliferate when activated by their specific antigen.

B

Each T or B cell has receptors that respond to only one antigen and ignores all others.

C

Activated lymphocytes produce two groups of cells: one group that attacks the invader immediately, and another that remains inactive unless it is exposed to the same antigen at a later date.

D Each T and B cell can recognise many antigens and respond to a wide variety of possible threats. E

T cells are versatile because they produce copious quantities of antibodies that can respond to a wide variety of threats.

F

Phagocytes have a reduced ability to destroy pathogens during subsequent infections.

G The immune response ignores self-antigens and targets non-self antigens. H B cells differentiate into T cells to create a long-lived immune response.

2

QUESTION 3 Describe how bone cells respond to the hormones involved in the homeostasis of blood calcium ion concentration. (3 marks) When blood calcium levels are increased the thyroid gland C-cells secrete calcitonin. This inhibits osteoclast activity and osteoblasts deposit Ca2+ into the bone matrix. As a result, blood calcium levels decrease to maintain homeostasis. When blood calcium levels are decreased the parathyroid gland secrets parathyroid hormone. This increases osteoclast activity which break down bone to release Ca2+ into the blood stream. This increases the calcium concentration in the blood and maintains homeostasis.

QUESTION 4 Why is injury to the medulla oblongata usually fatal? (2 marks)

The medulla oblongata is the control centre for heart rate, blood pressure, and respiration as well as automatic reflexes such as coughing and sneezing. Injury to this site would prevent these vital functions from occurring resulting in death.

QUESTION 5 Complete the following table summarising the effects of autonomic innervation on target tissues. You must include both the effect upon the target tissue and a consequence of this stimulation in your answer. The first row has been completed as an example. (1 mark/box; 4 marks total) Target tissue

Effect of sympathetic stimulation

Effect of parasympathetic stimulation

Contractile

Contractile force increases; more blood

No parasympathetic innervation of 3

force of the heart

pumped from heart

ventricular myocardium; therefore, no result

Airways in the lungs

Dilation of airways and increased respiratory rate; increase oxygen and carbon dioxide exchange.

Contraction of airways and decreased respiratory rate; decreased oxygen and carbon dioxide exchange.

Pupil

Pupil dilation; allows more light to the retina to increase vision

Pupil constriction; decreases light to the retina

QUESTION 6 Using the diagram provided as a prompt, outline the four steps involved in the transmission of an electrical impulse from the presynaptic neurone to the post synaptic neurone. (4 marks)

Step

Outline 1 2 3

As the action potential arrives at the axon terminal, the voltage gated Ca2+ channels open causing calcium ions to rush in. Calcium ions inside the cell causes the exocytosis of neurotransmitter vesicles. Neurotransmitters travel across the synaptic cleft and bind to ligand-gated ion channels in the postsynaptic neuron. 4

4

The neurotransmitters are either 1) taken up by the astrocytes or the presynaptic axon terminal, 2) degraded by enzymes, or 3) diffuse away from the synapse.

5

QUESTION 7 The following paragraph refers to muscle contraction. Fill in each of the blanks to complete the paragraph using terms from the list provided. More terms than necessary are provided, and terms may be used more than once. (0.5 mark each; total 3 marks)

The action potential spreads along the sarcolemma , until it reaches a T-tubule. The action potential continues down the T-tubule, where it triggers the release of Ca2+ from the sarcoplasmic reticulum. This exposes binding sites on actin. Myosin heads bind to the exposed sites on actin to form cross-bridges.     

Na+ K+ Ca2+ Mg2+ actin

    

sarcoplasm sarcolemma sarcoplasmic reticulum sarcomere nucleus

    

mitochondria Golgi apparatus myofibril myosin myofilament

QUESTION 8 Think about how the renin-angiotensin-aldosterone system acts to maintain normal blood pressure. Susan has sustained damage to her adrenal glands. Consequently, her circulating levels of aldosterone are abnormally low. A. Where are the target cells for aldosterone located in the body? (1 mark) Adrenal glands

B. What do you expect the lack of aldosterone to do to Susan’s blood pressure? Explain your answer. (3 marks) Aldosterone is responsible for the retention of sodium in the blood. Therefore, the lack of aldosterone would result in sodium loss. This would reduce Susan’s blood pressure as water follows sodium.

6

QUESTION 9 Explain the role of baroreceptors in the control of blood pressure during a short period of widespread vasodilation. (3 marks) Widespread vasodilation results in a drop in blood pressure. As a result, the barorecptors located in the aortic arch and carotid sinuses are inhibited. Electrical impulses are sent to the brainsteam via the vagus and glossopharyngeal nerves. This results in signals via the sympathetic nervous system to increase vasoconstriction, cardiac output, contractility, and heart rate. Consequently, blood pressure increases to return to normal.

QUESTION 10 Explain the term ‘normal sinus rhythm’. (1 mark) Normal sinus rhythm is the heart beat due to electrical impulses generated at the SA node (pacemaker).

QUESTION 11 For each of the scenarios below, indicate whether you would you expect resting heart rate to be greater or less than that associated with normal sinus rhythm of a person with average fitness. Explain the cardiac physiology underlying the identified change. (4 marks)

Heart rate Greater than

Less than

Situation A person of average fitness running a 5km fun run.

Explanation More oxygen is required at target tissues so the heart rate would need to increase to maintain adequate oxygen supply.

An endurance athlete at rest.

Endurance athletes have hypertrophic cardiac tissue and stroke volume increases. This means 7

that cardiac output can be similar to that of a normal person but can maintain a lower heart rate.

QUESTION 12 Haemophilia is the oldest known hereditary bleeding disorder. Explain why haemophilia is more commonly seen in males. (3 marks)

alcohol inhibits the

C B

ete the missing

A

D

utes are the tubular 8

lumen to peritubular capillaries (blood) Along the length of the tubular network; the exact location depends on the substance being transported QUESTION 15 The Wigger’s diagram (below) represents pressure and volume relationships in the left side of the heart during one cardiac cycle. To answer this question, you should focus on the changes in pressure in different chambers of, or vessels leading from, the left side of the heart. For TWO of the labelled points, state which valve is open/closed at that time. Highlight your chosen point in bold. You must also explain WHY that valve opened/closed and where the blood is flowing immediately after this point in time, due to the change in position of the valve. An example is provided. (4 marks) Label A

Valve (name and open/closed)

Explanation

Left AV/bicuspid valve opens

The pressure in the left ventricle becomes lower than that in the left atrium. Blood flows from the left atrium to the left ventricle.

B C D

9

QUESTION 16 A person with type B blood has been involved in a car accident and excessive bleeding necessitates a blood transfusion. Due to an error by a careless laboratory technician, the person is given type A blood. Explain what will happen. (4 marks) When a person is given blood with an incompatible type, a transfusion reaction occurs. Type A blood cells have different surface antigens than type B blood cells. This would cause anti-A antibodies present in the blood plasm to attach to the Type A cells. This would result in haemolysis of the Type A cells and causes them to clump together (agglutination).

QUESTION 17 A. Complete the below table of partial pressures in external respiration. (2 marks) pO2 (mmHg)

pCO2 (mmHg)

Alveoli

10

Capillary

B. Use to the figures above to explain how differences in partial pressures drive the direction of gas movement between the blood and alveoli. (2 marks)

11

QUESTION 18 The figure below illustrates inspiration and expiration. Refer to this figure to answer the following questions. (0.5 marks each - 3 marks total)

Question Contraction of which muscle/s produces the movement labelled "1"? Contraction of which muscle/s produces the

Answer

Diaphragm

movement labelled “2”? At label “3”, is pressure outside greater than or less than pressure inside the lungs? Is the pressure in the space labelled "4", higher or lower compared to the atmospheric pressure? At label “8”, is pressure outside greater than or less than pressure inside the lungs? Name any ONE muscle that contracts to cause the extra movement required when you need to expire forcefully (indicated by the arrows labelled "6" and "7").

12

QUESTION 19 The graph below displays the oxygen dissociation curve and factors that affect the release of oxygen from haemoglobin (Hb). According to the graph, list the three factors that affect the release of oxygen into the blood supply of a hard-working skeletal muscle. For each factor, explain how it contributes to the release of oxygen from haemoglobin. (3 marks)

Image from http://www.gpnotebook.co.uk/simplepage.cfm?ID=20250669

13...