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Summary 4BBY1060- Fundamentals of Physiology and Anatomy
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4BBY1060- Fundamentals of Physiology andAnatomy
L3: Homeostasis and physiological control
• Homeostasis is the dynamic maintenance of physiological variables within a predictable range.
• Physiological variables include blood glucose/O2/CO2/pH, extracellular fluid osmolarity/volume
(immediate survival), temperature, metabolic rate, appetite/gastro-intestinal secretions (medium/
long term survival), and steroid hormone levels (survival of
species).
• A variable of greater immediate importance can be maintained
at the expense of other variables.
• Negative feedback (reflex arcs): change in variable is
compared against a set-point, causing a response which will
bring the variable back to the set-point.
• Neuronal integrating centres for physiological control are
located in the hypothalamus, pons and medulla (part of the
ANS).
• An example (control of body temperature) is seen:
• Within endocrine control mechanisms, response of a target
tissue depends on the type of hormone receptor expressed.
• The hypothalamus sends releasing hormones, triggering the
release of oxytocin and ADH (peptides) from the posterior
pituitary and FHSH, LH, (glycoproteins) and GH (polypeptides) etc.
• Peptides, proteins, glycoproteins, catecholamines hormones have their receptors in the
plasma membrane and evokes a rapid, transient response.
• Steroids and thyroid hormones have their receptors in the cytoplasm or nucleus and evokes a
slow, prolonged response.
• Negative feedback reflexes that operate locally are independent of the CNS. Sensors,
integrating centres and effectors located in the same tissue.
• Feed forward: anticipation of a change brings about a response before the change has
occurred.
• They are normally neuronal. Examples include anticipation of physical exertion or a meal.
• Positive feedback: change in variable triggers a response that causes further change in that
variable.
• It can be hormonal, neuronal, or a combination of both. Examples include oxytocin secretion
+ve feedback which increases the excitability of the uterus during parturition (contraction of
uterus during childbirth).
,L4: Epithelial Cells
• Epithelial cells cover body surfaces and line body cavities.
• Specialisations on the apical surface include the glycocalyx,
cilia (in respiratory tract/uterine tube) and microvilli (in small
intestine and kidneys).
• The glycocalyx is a cell coat. It consists of glycoproteins/
glycolipids that project from the plasma membrane. It aids with
cell-cell recognition/communication and intercellular adhesion.
• The cilia appear as short, hair-like structures between 1-10µm.
They help move particles and fluid along epithelial surfaces.
• Microvilli are irregular ‘bleb’ like projections (1µm). They are tall, closely packed in cells that have
an absorptive function.
• The lateral domain contains various junctions and intermediate filaments.
• The basal domain has 3 features: the basal lamina (where cells sit), cell to ECM junctions and
basal cell infolding (increase cell surface area to increase interactions between cells and ECM).
• The basal lamina acts as an adhesion interface between epithelial cells and the ECM, as a
permeability barrier and may control cell organisation and specialisation.
Type Feature Image Location
where diffusion, absorption
Simple single layer
and/or secretion takes place
oral cavity, pharynx,
oesophagus, cervix and
Stratified two or more layers
vagina, site which are kept
noise by secretions
Squamous cell width > height
Cuboidal cell width=depth=height
basement membrane
Columnar cell width < height
all cells sit on the basal
airways of the respiratory tract,
Pseustratified lamina however not all
nose and sinuses.
reach the surface
, • There are often different names for different locations such as endothelium
(blood/lymphatic vessels), endocardium (heart) and mesothelium (body
cavities).
• Transitional epithelium is a form of stratified epithelial which has umbrella/
dome cells which are large and rounded. As they approach the basal lamina
the cells become more cuboidal.
• All endothelial cells are simple squamous epithelium. Gas exchange: simple squamous
• The epithelia form a protective/selective barrier, from Absorption: usually simple columnar
glands and secrete products, regulate exchange of Filtration: simple
molecules and help with absorption. Reabsorption: simple cuboidal
• Type I pneumocytes line 95% of the alveoli and type Secretion: usually simple columnar
II pneumocytes produce a thin layer of surfactant.
L5: Structure and development of the cardiovascular system
• The heart develops during post-conception 3-8 weeks. First cells specialise into the 3 germ
layers, the mesoderm forms the heart. By day 50 the heart is fully developed.
• The heart operates in double circulation using both the pulmonary and systemic system.
• The heart is enclosed in a connective tissue known as the pericardium which also prevents
friction. It consists of an outer layer which anchors the heart to the diaphragm, blood vessels
and anterior chest wall to hold its position and 2 inner layers. The visceral layer is adherent to
the heart and the parietal layer is in the middle.
• There is a fluid-filled space between the two layers.
• The left ventricle of the heart always appears larger than the right as it has thicker walls as it is
under higher pressure.
• The fibrous skeleton of the heart is dense connective tissue which separates the atria from the
ventricles, and the flow of electrical impulses.
• Cardiac conduction system: An excitation signal caused by the sinoatrial node causes a wave of
excitation across the atria causing them to contract. Once it reaches the atrioventricular node it
is delayed and then conducted to the Bundle of His, then to the Purkinje fibres causing the
ventricle to contract.
• The left and right coronary arteries are the main suppliers of blood to the heart. They arise from
aortic sinuses. When the heart is relaxed back-flow of blood fills these arteries.
• Several cardiac veins drain into the great cardiac vein which empties into the coronary sinus and
then into the right atrium.
• The AV valves, bicuspid (left) and tricuspid (right), prevent back flow in the heart. Semilunar
valves separate the atria from the ventricles.
• Contraction of the papillary muscles within the AV valves tenses the cords attached to the
cusps, causing them to swing together and prevent back flow when the ventricle contracts.
• Semilunar valves consist of a thin layer of connective tissue lined by endothelium. They are
forced apart by the ejection of blood when the ventricle contracts. When they are closed they
appear as a ‘Y’ shape.
• Heartbeats are caused by the closing of valves. A heart murmur is when the AV valves don't
close properly.
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