BIOL121 Worksheet: Human Biology - Semester 1 Assignment - University

This document presents a completed BIOL121 worksheet, addressing various aspects of human biology. The assignment includes questions on immunity (specific and non-specific), properties of adaptive immunity, bone cell response to hormones, the function of the medulla oblongata, effects of autonomic innervation, the transmission of electrical impulses in neurons, muscle contraction, the renin-angiotensin-aldosterone system, the role of baroreceptors, normal sinus rhythm, heart rate changes, haemophilia, the effects of alcohol on ADH, urine formation steps, and the cardiac cycle. The provided answers offer comprehensive explanations and insights into these core biological concepts, providing a valuable resource for students studying human physiology and related fields.

Name:
Student number:
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 Type of immunity
Bacterial septicaemia (bacterial
contamination in systemic circulation)
Specific (antibody mediated)
The pH of hydrochloric acid in the
stomach acts to destroy ingested
bacteria
Non-specific (first-line defence)
A liver cell mutates and becomes
cancerous
Specific (Cell-mediated immunity)
A virus multiplies inside the epithelial cells in
your throat.
Non-specific (first-line defence)

QUESTION2
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
Explanation
Even though your body contains a relatively small number of
lymphocytes, your immune system can mount a response
against almost any antigen it encounters.
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.
Your immune system can distinguish between antigens on
your own cells, and those of an invading pathogen.
Self-
recognition G
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.
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QUESTION 3
Describe how bone cells respond to the hormones involved in the homeostasis of blood calcium ion
concentration. (3 marks)
Bone cells are crucial in homeostasis of blood calcium. Parathyroid glands release parathyroid hormone
(PTH) when there are low blood calcium levels, which stimulates bone resorption. Besides, PTH directly
affects the kidneys by preventing the loss of calcium ions through urine; hence reabsorption of the
ions. On the other hand, thyroid glands release calcitonin in response to high blood calcium. Calcitonin
suppresses bone resorption activity and increases the amount of calcium excreted in urine. PTH and
calcitonin act as feedback mechanisms to balance blood calcium ion concentrations (Chonchol &
Kendrick, 2019).
QUESTION 4
Why is injury to the medulla oblongata usually fatal? (2 marks)
Medulla oblongata is found on brain stem. It is essential in regulating the body’s involuntary processes,
such as respiration, digestion, reflex, and neuronal responses. An injury to this part is life-threatening
as it may disrupt the involuntary processes. It may cause paralysis, loss of body coordination, loss
touch senses, and ultimately cause 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
force of the
Contractile force increases; more blood
pumped from heart
No parasympathetic innervation of
ventricular myocardium; therefore, no
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heart result
Airways in
the lungs
Smooth muscles relax; bronchioles
increase in diameter; results in dilation of
the bronchioles
Smooth muscles contract; bronchioles
decrease in diameter; hence causing
constriction of the bronchioles
Pupil Radial muscles contract; the pupil dilates Circular muscles contract; thus, the pupil
constricts
QUESTION6
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
Nerve impulse at the axon end stimulates the opening of the Na+ voltage-gated channel.
Na+ depolarizes the pre-synaptic membrane, and activates the K+ channel, which further
depolarizes voltage gated Ca+ channel (Pereda, 2014).
2
Calcium ions results in the fusion of synaptic vesicles with the pre-synaptic membrane.
Neurotransmitters bind with receptors on of the ligand-gated channels of the post-
synaptic membrane.
3 The post-synaptic membrane depolarizes.
The neurotransmitters may elicit inhibitory or excitatory responses
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4
The post-synaptic membrane resets ready to receive another signal. The
neurotransmitters need to be removed from the cleft. It can diffuse or recycled into the
presynaptic membrane.
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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+  sarcoplasm  mitochondria
 K+  sarcolemma  Golgi apparatus
 Ca2+
 Mg2+
 sarcoplasmic reticulum
 sarcomere
 myofibril
 myosin
 actin  nucleus  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)
Distal tubule
Collecting ducts
B. What do you expect the lack of aldosterone to do to Susan’s blood pressure? Explain your
answer. (3 marks)
Aldosterone is a steroid hormone responsible for the reabsorption of water along with Na+; elevating
blood volume; therefore, raising blood pressure. However, damage to the adrenal glands results in lack
production of aldosterone. As a result, Susan’s kidneys will not retain Na+ and water as well as excrete
K+. Therefore, the homeostatic imbalance of water and salts will result in low blood volume, hence
decreased blood pressure.
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QUESTION 9
Explain the role of baroreceptors in the control of blood pressure during a short period of widespread
vasodilation. (3 marks)
Baroreceptors line the blood capillaries and help monitor blood pressure changes. Elevated blood
pressure stimulates an increased parasympathetic input. Consequently, it results in lower heart rate,
vasodilation, and low blood pressure.
QUESTION10
Explain the term ‘normal sinus rhythm’. (1 mark)
It is the rhythm originating at the sinus node. It describes the typical rhythm of a normal heart. A
normal sinus rhythm denotes all the measurements of an electrocardiogram, such as PR and QT
intervals are normal. Besides, it denotes a normal P wave axis and heart rate.
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 Situation Explanation
Greater
A person of average fitness
running a 5km fun run.
The heart rate rises causing the person’s body to
increase cardiac output. It determines the amount
of oxygenated blood supply to muscles and tissues.
Less
An endurance athlete at
rest.
Endurance athletics increase cardiovascular
efficiency; it strengthens the heart muscles that
results in larger stoke volume; therefore, greater
volumes of oxygen is delivered to the heart and
peripheral organs.
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QUESTION12
Haemophilia is the oldest known hereditary bleeding disorder. Explain why haemophilia is more
commonly seen in males. (3 marks)
Haemophilia is a recessive X-linked disorder that is passed to generations through the X chromosome.
It is common in males who have XY chromosomes as they inherit a single X chromosome unlike their
female counterparts who have XX chromosomes. The males inherit their X and Y chromosomes from
their mothers and fathers respectively. Thus, they will have haemophilia when the single X
chromosome carries a mutation for the disorder (Wang et al., 2017).
QUESTION 13
Tasma is enjoying a night out at the pub with her friends. It is well established that alcohol inhibits the
secretion of ADH. Explain how this will affect her urine output. (3 marks)
Alcohol acts on pituitary glands by inhibiting the secretion of ADH that regulates the amount of water
reabsorbed by the kidneys. Since alcohol acts on the hypothalamus and pituitary glands, it reduces the
amounts of ADH in circulation. When ADH reduces in Tasma’s body, her kidneys won’t reabsorb more
water, thus, more urine output.
QUESTION 14
The following table describes the three elementary steps of urine formation. Complete the missing
parts of the table. (4 marks total)
Step in urine formation
(0.5 marks/cell)
Where does this step take place?
(0.5 marks/cell)
What happens?
(1 mark/cell)
Filtration Glomerulus Blood passes through the
glomerulus at greater pressure
pushing water and small molecular
weight substances, such as
nitrogenous wastes from the blood
capillaries into Bowman’s capsule.
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The glomerulus retains cells and
blood components.
Reabsorption Along the renal tubule Water and/or solutes are
transported from the tubular
lumen to peritubular capillaries
(blood)
Secretion Along the length of the tubular
network; the exact location
depends on the substance being
transported
Different components such as
creatinine are eliminated from the
blood via the capillaries to the
collecting ducts to form urine:
substances nor reabsorbed
following glomerular filtration or
tubular filtration (Lawrence, Daniel
& Raman, 2018).
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 Valve (name and open/closed) Explanation
A
Left AV valve closes
The pressure in the left ventricle is greater than in the
left atrium. Blood flows from the left ventricle into the
left atrium.
B
Left Semilunar valve opens
Ventricular muscles contract generating high pressure
than that in the arterial tree. Blood flows to the aorta
and pulmonary trunk.
C Left semilunar valve closes The left ventricles relax. Arterial pressure becomes
greater than ventricular pressure making the semilunar
valves to close. It prevents the blood flow into the
ventricles.
D 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.
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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)
The ABO blood system consists of four blood groups: A, B, AB and O. ABO incompatibility reactions
occur when patients are given the wrong blood type, for instance in this case where person with type B
blood is given type A blood. Red blood cells contain antigens on their surfaces. Type A and B blood has
A and B antigens respectively. Usually, the immune system produces antibodies against antigens that are
not recognized in the blood. Thus, the person with type B blood will create antibodies against B antigens
following the blood transfusion. The ABO incompatibility reactions will destroy the donor’s blood cells
resulting in severe symptoms, such as flank pain, fever, and dizziness (Mitra, Mishra, & Rath, 2014).
QUESTION 17
A. Complete the below table of partial pressures in external respiration. (2 marks)
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pO2 (mmHg) pCO2 (mmHg)
Alveoli High; about 100 mmHg Low; about 40 mmHg
Capillary Low; about 40 mmHg High; about 45 mmHg
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)
Gases move from regions of higher partial pressure to the regions of low pressure. As a result, oxygen
will move from the alveoli (100 mmHg) into the blood capillaries (40 mmHg). Similarly, carbon (IV)
oxide is released from the capillaries (45 mmHg) to the alveoli (40 mmHg).
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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 Answer
Contraction of which muscle/s produces the
movement labelled "1"?
Intercostal muscles; enlarges chest cavity.
Contraction of which muscle/s produces the
movement labelled “2”?
Diaphragm; increases chest cavity for which the lungs
expand.
At label “3”, is pressure outside greater than or less
than pressure inside the lungs?
The pressure outside is greater than in the lungs;
pressure difference facilitates the movement of air
into the lungs: inhalation.
Is the pressure in the space labelled "4", higher or
lower compared to the atmospheric pressure?
Lower than the atmospheric pressure.
At label “8”, is pressure outside greater than or less
than pressure inside the lungs?
The pressure outside is less than that in the lungs; the
higher pressure in the lungs flows out: exhalation.
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").
Abdominal muscles; pushes the diaphragm up which
raises alveolar pressure; hence, exhalation.
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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
Partial pressure of oxygen: Gases move from high pressure to low pressure regions. The affinity of
oxygen molecules to haemoglobin increase more molecules are bound. As seen from the curve, as the
partial pressure of oxygen increases, there is a subsequent increase in the molecules of oxygen that is
bound to heme. Thus, partial pressure is critical in determining the extent of binding or dissociation of
oxygen to heme at the respiratory and tissue sites (Nagalakshmi, Madhisudhana, Rajendra &
Manjunath, 2016).
pH: Low pH stimulates the dissociation of oxygen from haemoglobin. By contrast, high pH inhibits the
dissociation of oxygen from haemoglobin. Higher carbon (IV) oxide concentration generates more
hydrogen ions, thus lower blood pH, which contributes to the release of oxygen.
Temperature: High temperature levels stimulate the dissociation of oxygen from haemoglobin. On the
contrary, low temperatures inhibit the dissociation of oxygen molecules from the haemoglobin. High-
active tissues that release more energy stimulates the dissociation of oxygen from haemoglobin, hence
supplying more oxygen to the active tissues (Nagalakshmi et al., 2016).
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References
Chonchol, M., & Kendrick, J. (2019). Calcium Homeostasis in Kidney Disease. In Endocrine Disorders in
Kidney Disease (199-206). Springer, Cham.
Lawrence, E. A. (2018). Function of the nephron and the formation of urine. Anaesthesia and intensive
care medicine, 19(5), 249-253. doi:10.1016/j.mpaic.2018.03.001
Mitra, R., Mishra, N., & Rath, G. P. (2014). Blood groups systems. Indian journal of anaesthesia, 58(5),
524-528. doi:10.4103/0019-5049.144645
Nagalakshmi, N. V., Madhusudhana, R., Rajendra, N., & Manjunath, A. K. (2016). Hemoglobin and
oxygen transport. Karnataka Anaesthesia Journal, 2(1), 1-6.
Pereda A. E. (2014). Electrical synapses and their functional interactions with chemical synapses.
Nature reviews neuroscience, 15(4), 250-263. doi:10.1038/nrn3708
Wang, M., Cyhaniuk, A., Cooper, D. L., & Lyer, N. N. (2017). Identification of patients with congenital
hemophilia in a large electronic health record database. Journal of blood medicine, 8, 131-139.
doi:10.2147/JBM.S133616
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