MMED1005: How Your Body Works Assignment 1 - Physiology Review

This assignment, completed for the MMED1005 course, delves into fundamental biological processes. Question 1 explains cellular respiration, detailing the breakdown of glucose, the role of mitochondria, and the four stages of the process including glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation. Question 2 explores action potentials, the role of calcium channels, the release and breakdown of acetylcholine, and the effects of organophosphate poisoning. Question 3 contrasts the sympathetic and parasympathetic nervous systems, outlining their functions and discussing the effects of beta-blockers. Finally, Question 4 examines reflex pathways, including the palmar grasp reflex and the role of proprioceptors in detecting body position and movement, illustrated by the example of Mary dropping books.

Assign. 1: Question 1 Surname, First Name
Cellular respiration is a process in which animals get their energy through the breakdown of glucose
through a catabolic process1.
The glucose molecule is the raw material for cellular respiration, and it is obtained from carbohydrates
for example bread, protein for example fish which is first broken down to amino acids and fats for
example butter are broken down to fatty acids. The glucose molecule is catabolised into water and
carbon dioxide, and in the process, ATP is produced
Cells involved in cellular respiration are mitochondria, cytoplasm, plasma membrane and
mitochondrial membrane.
There are four stages in the process of mammal’s cellular respiration. This is glycolysis, citric acid
cycle (kerb cycle), pyruvate oxidation and oxidative phosphorylation. Usually, this process uses oxygen
called aerobic respiration, and when oxygen is not available, the cells make use of anaerobic
respiration.
The first step in glycolysis. This is mainly the breakdown of glucose, and it occurs at the cytoplasm of
the cell. At this step, one molecule of glucose is catabolised into two pyruvate molecule. Glycolysis can
produce 2 ATP molecules and 2 NADH.
Pyruvate oxidation is the second stage which takes place in mitochondria, this stage requires oxygen,
and pyruvate from glycolysis is oxidised where the carboxyl group from pyruvate is removed forming
acetyl group which combine with coenzyme A to form acetyl CoA. In turn, 1NADH and carbon
dioxide is produced.
Citric acid cycle (kerb cycle) is the third stage which is aerobic, it takes place in mitochondria, and
ATP concentration regulates the rate of this cycle, acetyl CoA produced during pyruvate reaction
combines with four molecules. It produces NADH, FADH2 that act as electron storage compound, but
temporary which use atmospheric oxygen, and it generates CO2, 2ATP, 3NADH and FADH2.
The last step is oxidative phosphorylation stage which is an electron transport chain where NADH and
FADH2 produced in the Kreb cycle and pyruvate oxidation deposit their electrons into electron
transport chain, and they change to stable forms that are NAD and FAD. Proton pump transports
hydrogen from inside mitochondria to the outside making the phosphate group attached. This
movement of protons changes ADP to ATP.
Cellular respiration is able to produce 90% ATP obtained from glucose breakdown. A total of 38ATP is
produced at the end of cellular respiration two from glycolysis, two from the citric acid cycle (Krebs
cycle) and 34 produced during electron transport chain.

Assign. 1: Question 2 Surname, First Name
a) When an action potential reaches the axon terminal, activation of the voltage-gated calcium
channels occurs 2 found in the cell membrane, because they are in higher concentration at the
outside of the neuron than inside it causes in-flux of calcium into the cell causing synaptic vesicles
to fuse with a terminal of the axon of the neuron which makes acetylcholine to be released from the
vesicles into the synaptic cleft. Diffusion of acetylcholine molecules into the synaptic cleft occurs,
and this allows binding on the receptors of the target cell that is on the postsynaptic cleft when
receptors are activated it allows opening and closing if ion channel present in the cell membrane
which can make inside of the cell to be more positive or more negative.
b) Acetylcholine is removed by the mechanism of diffusion where acetylcholinesterase found in the
synaptic left breaks down acetylcholine into choline and acetate it is then removed by glial cells the
presynaptic terminal3.
c) Organophosphate is a chemical substance which is produced as a result of a chemical reaction
between phosphoric acid and alcohol, and they affect the body by destroying acetylcholinesterase
enzyme which is responsible for transmitting signals in the body. Unavailability of acetylcholine
production can lead to muscle weakness.
d) Organophosphate poisoning has the following clinical signs: vomiting, lacrimation, urination,

defecation, and abdominal pain. The receptors involved are muscarinic and nicotinic.
Assign. 1: Question 3 Surname, First Name

a) Autonomic nerves system consists of both parasympathetic and sympathetic system and therefore,
nerves of both parasympathetic and sympathetic4. Autonomic nervous system exit both sides of the
brain and the spinal cord. The sympathetic system has the following functions; dilates pupil, inhibit
salivation, increases heart rate, dilate the airways, inhibit digestion, constrict the peripheral blood
vessels, sweat gland activation, and activation of adrenal glands, rectum contraction, bladder relaxation
and orgasm stimulation. The parasympathetic system has the following functions; constrict pupil,
stimulate salivation, slows heart rate, constrict the airway, stimulation of digestion in the digestive
system, rectum relaxation during elimination, bladder contraction and stimulation of arousal in the
genitals.
b) Drugs like beta-blockers slow down heart rate, and this occurs as a result of the effect on the
parasympathetic system, which slows heart rate by releasing acetylcholine5.
Assign. 1: Question 4 Surname, First Name

a) Palmar grasp reflex. Neural reflex pathway helps in controlling a reflex, and it helps in faster reflex
action6. A neural pathway has several components. These components are; stimuli, receptors, muscles,
neurons which are three: sensory, interneurons and motor neurons. The neural pathway has five steps
that are sensor which has receptors that are able to detect stimuli when the receptor detects the stimuli,
sensory transfers the message from the receptor which travels via interneuron to the motor neuron,
which transfers the message to the effector that has receptors, this causes the effector to be stimulated.
The reaction is produced, which is the response to the stimuli.
b) proprioceptors specifically Muscle sensory receptors that can detect internal stimuli that is
movement and position on of the body7, this is sensory receptors found in the skeletal muscle which
detect the changes in muscles length or stretching that leads to motor control. When the 5th textbook is
added to Mary's hand proprioceptors are able to detect overstretching of the muscle, thus causing
relaxation of the arm. When the hand relaxes, it is unable to support the weight of the books, and this
leads to Mary dropping the books. The brain was able to detect the internal stimuli through the
proprioceptors, and it gave a response involuntarily, which is Mary dropping the books.

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2017 Jun 28.
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methods. Journal of Sport and Health Science. 2016 Mar 1;5(1):80-90.