University Assignment: Principles of Anatomy and Physiology, BIOL 235

This document is a comprehensive solution to an anatomy and physiology assignment, addressing key concepts within the field. The assignment explores the muscles involved in breathing, detailing their locations and actions. It also examines the events at a chemical synapse, explaining how nerve impulses are transmitted. Furthermore, the assignment delves into the physiological role of reflexes, including cranial reflexes and the role of the brain in reflex pathways. The document also analyzes the neuronal pathways activated by pain, such as when hitting a thumb with a hammer, and the structural and functional relationship between the hypothalamus and the pituitary gland. The components of the eye and their functions are described, along with the consequences of any abnormalities. Finally, the document details the physiological responses to fear, such as the fight-or-flight response, offering a detailed exploration of the subject matter.

Running head: PRINCIPLES OF ANATOMY AND PHYSIOLOGY
Principles of Anatomy and Physiology
Name of the Student
Name of the University
Author Note

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PRINCIPLES OF ANATOMY AND PHYSIOLOGY
Answer 1
The main muscles that are used in breathing or respiration (inhalation and exhalation)
is diaphragm. Diaphragm aids in expansion and contraction of the thoracic activity and thus
helping in the process of breathing. After diaphragm, the second muscle that aids in the
process of breathing is intercostals muscles. It mainly drives the respiration during the
process of quite breathing. The lungs can be expanded and contracted in two different ways.
The downward and upward movement of the diaphragm is used to lengthen or to shorten the
chest cavity. The depression and elevation of the ribs helps in increasing and decreasing the
antero-posterior diameter of the chest cavity. During the inspiration and contraction, the
diaphragm (located just below the rib-cage) pulls the lower surfaces of the lungs downward.
During expiration, diaphragm relaxes the pulmonary muscles and the walls of the chest. This
leads to the compression of the abdominal structure and thereby helping the lungs to expel
the air (Tortora & Derrickson, 2008).
Answer 2
When the neuron is at resting phase (nonstimulated), the electric potential in the
axonal terminal is -60mV (inside negative in comparison to outside). This resting potential is
similar to the membrane potential of the non-neuronal cells. The peak of the action potential
is +50mV. Thus the net change is 110mv (approx). This increase in the electric potential from
the resting membrane stage to the action potential is known as depolarization.. Depolarization
is followed by rapid repolarization helping to return to the resting membrane stage/ An action
potential mainly originates at the axon hillock. Axon hillock is known as the junction
between the axon and the cell body. The action potential moves through the action and
arrives at the action terminal (through the process of depolarization). The axon terminals are
regarded as the small branches of axon that form synapses or connection of the other axons

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(axon hillocks). This movement of the action potential through the axon occurs at the rate of
100 meters per second. At arrival of the action potential at the action terminal cause opening
of the voltage gated Ca2+ ion channels. This cause influx of the Ca2+ ions causing localized
increase in the Ca2+ ion concentration at the axon terminus. The increase in the Ca2+ ions in
turn triggers the fusion of the small versicles containing the neutron-transmitter (carried by
the action potential up to the action terminal) with the plasma membrane. This occurs
releasing of the neuro-transmitter from the presynaptic cell into the synaptic cleft. Synaptic
cleft is the narrow spacing separating it from the post-synaptic cells. 0.5 mill-second time is
require diffusing the neurotransmitter across the synaptic cleft followed by the binding to a
receptor present on the post-synaptic cells. This helps in the flow of the nerve impulses from
one neurone to the neighbouring neurone (Tortora & Derrickson, 2008).
Answer 3
Reflexes are automatic yet subconscious response to the changes that are occurring
within or outside the body. The main physiological role of reflexes in the body is it helps in
maintaining homeostasis (autonomic reflexes) of the breathing rate, digestion, heart rate and
blood pressure. Reflexes also help to carry out the autonomic action like swallowing,
coughing, sneezing and vomiting. Reflex also helps in maintaining the body balance, posture,
control of the limbs and eye movements (Tortora & Derrickson, 2008).
The reflex action is carried out by the spinal cord. However, the information inputs
also reach the brain. Thus it is important for the brain to remember the incident and to act
accordingly. For example, the example of the action of removing hand away from touching
the hot plate is a type of reflex action. During the first instance, when the person is actually
touching the hot-plate, the hand is being removed under the action of the spinal cord. The
memory of pain or the burning sensation occurred upon touching the hot plate is stored in the

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brain and thus in every other instance when the hands near the hot plate, the reflex action is
executed by the brain (Tortora & Derrickson, 2008).
Cranial reflexes are mediated by the cranial nerves. One example of the cranial
reflexes are blinking or closing of the eye lids upon exposure of the cornea to bring light or
when cornea comes in contact with any dust particles. Malfunction in the cranial nerves
hamper the proper functioning of the cranial reflexes. For example, the involuntary closing of
the eye-lids fails to operate upon dust exposure to cornea. Closing of the eye lids upon dust
exposure to cornea is followed by secretion of tears from the tear glands that helps in the
removal of the dust. In the absence of closing of eyelids the tear glands fail to secrete tears
and thus leading to corneal damage (Tortora & Derrickson, 2008).
Answer 4
Hitting thumb accidentally with hammer is a type of non-neuropathic pain or
nociceptive pain arising from tissue injury. The pain after hitting the thumb with the help of
hammer is modulated by the sensory nociceptive nerve endings that is highlight conserved in
mammals and cutaneous nociceptors that are extremely heterogeneous in mammals.
Cutaneous nociceptors are housed in the peripheral sensory ganglia that are located outside
the central nervous system (CNS). These nociceptors transduce external noxious stimuli
present in the skin up to few meters away from their respective cell-bodies. Nociceptors are
mainly electrically silent and transmit all-or-none action potential once stimulated. However,
the activity of the nociceptors does not always leads to the generation of pain. Nociceptors
requires proper peripheral information in order to reach the higher centres and mainly relies
on the overall frequency of the action potentials coming from the primary afferents,
temporals summation of the post and pre-synaptic neuronal signals and CNS. The speed of
transmission of the action potential carrying the sensation of pain from the nociceptors

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mainly depends on the diameter of the axons of the sensory neurons and the degree of
myelination. The nociceptors are small in diameters and have unmyelinated axons that
remains surrounded by the Schwann cells. They mainly support the conduction velocities of
pain. Initial, first onset of pain is mediated by the myelinated nociceptors in case to hammer
hit injury, leading to tissue damage, the pain is sensed by the capsaicin-insensitive A – fibre
nociceptors (primary afferent nociceptors). Transmission of pain signals occur through direct
gating under the action of Na2+ ion channels (Tortora & Derrickson, 2008).
Answer 5
The pituitary gland is also known as hypophysis, is a small gland if 1 centimetre in
diameter and 1 gram (approx.) in weight. It is situated in the bony cavity at the base of the
brain as it is connected to the hypothalamus with the help of the pituitary stalk. Pituitary
gland is physiologically divided into two distinct portions; one is anterior pituitary
(adenohypophysis) and posterior pituitary (neurohypophysis). Anterior pituitary secretes six
different peptide hormones plus several other hormones. Posterior pituitary secretes two
important peptide hormones. The main hormones of the anterior pituitary are growth
hormones, adreno-corticorticotropin hormone, thyroid stimulating hormone, prolactin,
follicle stimulating hormone, luteinizing hormone, antidiuretic hormone (vasopressin) and
oxytocin. The secretion of all the hormone from the pituitary gland is controlled by the
hormonal and the nervous signal mediated by the hypothalamus (Tortora & Derrickson,
2008).
Answer 6
The path of light to the retina of the eye begins as soon as the light hits the eye. The
light upon reaching the eyes, begins the second journey through the optical organs of the
eyes. The main duty of the optical parts of the eyes is to adjust and focus the light to the

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neuronal cells that in turn carry the image of that object to the brain. Light, after reaching the
eyes encounter the cornea. It is known as the protective clear covering that is present over the
pupil and the iris. The role of the cornea is to bend the light waves and to initiate the pathway
of the image formation. After cornea, the light passes to the pupil. It is the dark circle that is
present at the centre of the irirs. It is regarded as the coloured portion of the eyes. The role of
the pupil is to regulate the amount of light that will enter into the inner eye area, based on the
prevailing environmental conditions. Pupils dilates, growing bigger in order receive more
light under dim light condition and shrinks during the bright light condition. This response of
pupil tends to decrease with the process of aging. After pupil, the light waves travel to the
lens of the eye. Lens is clear ye flexible structure that make an upside-down image over the
retina. The lends focuses the light over the retina finally. Retina is a layer of sensitive cells
present at the back of the eyes. It is made of cone cells and rod cells. These are photo-
receptor cells. Cone transmits colour and sharp images. Rods are sensitive to light and are
present in more concentration than cones. Rod cells help in dim light vision. Tshe image
produced in retina is transmitted through optic nerve to the brain for further image
development. The brain flips the image upside down and thus the image becomes upright
again (Tortora & Derrickson, 2008).
Injury to the eyes or normal variations in the eye (like myopia) or with the process of
again, focusing power of the lens might get altered and thus making it difficult to focus on the
far away or nearby objects. With again there might occur deposition of cataracts over the
lends leading to the generation of cloudy or dim vision. Keratoconus is a disease that results
in the thinning of cornea such that cornea is unable to bend all the light that is reaching over
its surface leading to the development of blurry vision. Retina might get damaged due to high
concentration of glucose in the blood (diabetic neuropathy) leading to the development of

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double vision. Problem in pupils hampers the dilation of the light entering into retina and this
in turn damages the retina further (Tortora & Derrickson, 2008).
Answer 7
The psychological response upon seeing a beer is fear. The main physiological
response controlling the effective management of fear is generation of the “fight or flight”
response. This response leads to the secretion on the stress hormones known as cortisol and
adrenaline. Any type of stress or phobia (physical or neurogenic) causes an immediate yet
significant increase in the secretion of ACTH from the anterior pituitary gland and this is
followed by greatly increased adrenocortical secretion of cortiso and adrenaline within
minutes. The secretion of these two hormones tells the brain whether to run away from the
fear (flight) or to fight against the fear. Cortisol is the major gluco-corticoid hormone that is
secreted from the adrenal cortex and it also provides mineralocorticoid activity. Cortisol
being a gluco-corticoid causes rapid mobilization of the fat and amino acids from the cellular
store and thus helping in the management of stress by immediate supply of energy to the
brain and muscle cells. After getting an escape from bear, the secretion of the cortisol from
adrenal cortex under the action of the ACTH decreases gradually (Tortora & Derrickson,
2008).
Answer 8
1: g, j
4: h
6: e
8: i

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10: b
14: d
15: f
17: c
18: a
19: h
Answer 9
a: 17
b: 6
c: 9
d: 1
e: 13
f: 9
g: 12
h: 19
i: 10
j: 1

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PRINCIPLES OF ANATOMY AND PHYSIOLOGY
Answer 10
The secretion of the hormones from the posterior pituitary occurs under the action of
the nerve signals originating from hypothalamus and terminating at the posterior pituitary.
The nerve endings pass through the pituitary stalk in order to reach posterior pituitary
(Tortora & Derrickson, 2008).
The hormones from the anterior pituitary are controlled by the hormones of the
hypothalamus known as hypothalamic releasing hormones and hypothalamic inhibitory
hormones. All these hormones are secreted from the hypothalamus and are transmitted to the
anterior pituitary by the hypothalamic hypophysial portal vessels. The major hormones of the
hypothalamus that control and co-ordinates the secretion of the anterior pituitary are:
 Thyrotropin-releasing hormone: Controls and co-ordinates the secretion of the
thyroid-stimulating hormone
 Corticotropin releasing hormone: Stimulates secretion of adreno corticotropic
hormones (ACTH) by the corticotropes
 Growth hormone releasing hormone: Stimulates the secretion of the growth hormones
by somatotropes
 Growth hormone inhibitory hormone (somatostatin): Inhibits the secretion of the
growth hormones by somatotropes
 Gonadotropin releasing hormone: Stimulates the secretion of the gonadotropic
hormones (follicle stimulating hormones, luteinizing hormone)
 Prolactin inhibitory hormone (dopamine in nature): Inhibits the secretion of the
prolactin hormone by lactotropes
(Tortora & Derrickson, 2008)

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References
Tortora, G. J., & Derrickson, B. H. (2008). Principles of anatomy and physiology. John
Wiley & Sons. 14th edition