Miscellaneous Flashcards
Define regulated variable
Any variable that is kept within certain limits by a homeostatic mechanism
Define sensor
A mechanism that measures a variable and generates an output signal proportional to its magnitude
Define set point
Range of values that the system attempts to maintain
Error detector
Computes difference between the set point and actual values and generates an error signal
Control centre
Combination of an error detector and controller that generates an out put signal to change an effector’s activity
Effector
A mechanism that contributes to determining the value of the regulated variable
Blood pressure
Give the:
a) regulated variable
b) sensors
c) control centre
d) effectors
e) response
a) Mean arterial pressure
b) mechanosensors In aorta and neck
C) medulla oblongata
d) heart and blood vessels
e) heart rate, contraction, peripheral resistance
Blood oxygen
Give the:
a) regulated variable
b) sensors
c) control centre
d) effectors
e) response
Arterial PO2
Chemoreceptors in aortic and carotid bodies
Brain stem
Diaphragm and respiratory muscles
Breathing frequency and depth
Blood glucose
Give the:
a) regulated variable
b) sensors
c) control centre
d) effectors
e) response
Blood glucose concentration
Islets of Langerhans
Pancreas
Liver, adipose tissue, skeletal muscle
Alter storage/ metabolism/ glucose release
Body temperature
Give the:
a) regulated variable
b) sensors
c) control centre
d) effectors
e) response
Core body temperature
Thermosensors in hypothalamus
Hypothalamus
Blood vessels, sweat glands, skeletal muscle
Change skin vessel resistance, sweat secretion, shivering
Problems with negative feedback
Slow response
Variable must change before effector responds resulting in oscillations and instability
What is a feedforward mechanism
Anticipatory response: producing an effector response before regulated variable changes
What does the posterior pituitary secrete
ADH and oxytocin
What is the fastest nerve conduction velocity
What is typical nerve conduction velocity
120m/s
50m/s
What do primary active transporters use
ATP
Where is glycine used
In the spine
Where is GABA found
The brain
Name inhibitory NT
Glycine
GABA
When does the length of A band change
Never
What is mean pulmonary arterial pressure
15mmHg
What is the ratio of capillaries: heart cells
1:1
What is the site of definitive hematopoiesis
Bone marrow
What colour is active bone marrow
Red colour
What is function of thymus
Selects lymphocytes that react with non self and not self
Give 4 key functions of the blood
Transport of nutrients, gases, hormones, waste
Restriction of fluid loss during injury
Defence from infection
Homoeostasis
What is hemostasis
Restriction of fluid loss
What are the 2 routes of transport across the capillary endothelial cell layer
Para cellular
Trans cellular
Describe the paracellular route of transport through capillary endothelium
Water and small solutes pass through the paracellular which this transport mode is limited by tight junctions and gap Junctions
Describe the transcellular route through endothelium
Larger sockets pass through this route either via a) receptor-mediated endocytosis or B) Trancytosis C) trans-endothelial channels such as vesicular vacuolar organelles
What are VVOs
Interconnected vesicles forming channels across the cell
Describe transcytosis
When cells take up extra cellular medium through caveolae-mediated macro pinocytosis and transfer to the opposite side of the cell
Where is fenestrated endothelium found
GI tract
Glomerulus
Endocrine cells
Describe the endothelium of the liver
It is discontinuous
Characterised by fenestrae without diaphragms and poorly organised basement membranes
These endothelial cells have a high level of clathrin mediated receptor endocytosis increasing their ability to take up specific molecules
Describe continuous nonfenestrated endothelium
Water and small solutes pass in between cells where as larger solutes pass through the cells via trans-cytosis
Where is the permeability of endothelium especially restricted
Brain
What forms the blood brain barrier (3)
Tighter endothelial junctions
Thicker basement membrane
A layer of supporting astrocytes
What does the BBB allow through (5)
Water Gases Lipid soluble hormones Glucose Some αα
How does the BBB prevent the entry of lipophilic potential neurotoxins
An active transport mechanism mediated by P – glycoprotein
Why are brain pathogens hard to treat
Antibodies are too large to cross the blood brain barrier and only certain antibiotics are able to pass
How do endothelial cells facilitate inflammation
Increase permeability so that plasma proteins and neutrophils can exit and reach the tissue/site of infection.
Do you fish and reptiles have enucleated RBCs
No
What could the loss of the nucleus in Mammalian red blood cells be related to
A larger genome in relation to body size and smaller diameter of capillaries
What does a pulse oximeter do
Measures blood oxygenation by comparing the different absorption of oxy Hb and deoxy Hb
Where does erythropoiesis occur in
a) adults
b) foetus
a) bone marrow
b) liver and spleen
How do RBC progenitor cells differentiate
How are old RBCs destroyed
They progressively differentiate into red blood cells losing the nucleus, ribosomes and organelles
By macrophages in the liver or spleen
Discuss EPO (3)
Erythropoietin
Produced in the kidney and regulated by negative feedback
Low oxygen stimulates the release of EPO, stimulating release of RBCs
Resulting high oxygen levels suppress production of EPO
What is the hypoxia response regulated by
Hif α
hypoxia inducing factor
What happens to Hif α in normoxia
What happens in hypoxia
Hydroxylated, leading to degradation
The activity of hydroxylases is reduced and HIF α can activate transcription of EPO
Why is destruction of RBCs important
Damaged RBCs release haemoglobin and iron which are sequestered in the kidney causing inflammation and damage
Name the 3 granulocytes
Neutrophils
Eosinophils
Basophils
Name the 4 agranulocytes I
T lymphocytes
B lymphocytes
Monocytes
Megakaryocytes
Discuss neutrophils (3)
Granules are visible with neutral dies
Crucial for a bacterial infections
Most abundant cells in the blood
discuss eosinophils
Granules are visible with acidic days
Play a role in parasitic infections
Granules contain peroxides and enzymes toxic to parasites
Discuss basophils
Granules are visible with basic ties
Produce histamine and heparin
Play a role in allergy
What do a) T and b) B lymphocytes do
a) kill infected cells or produce signals that assist function of other immune cells
b) produce antibodies
What are natural killer cells
They kill ourselves through different mechanisms, important for antitumour responses
What do monocytes do
Differentiate into other cells that can mediate phagocytosis and activation of T cells
Most tissues have resident macrophages and dendritic cells but monocyte serve as a reserve pool to supply more of the cells upon infection
What can monocytes differentiate into
Macrophages and dendritic cells
What are megakaryocytes
They are large multinucleated cells whose segmentation gives rise to platelets
Important for haemostasis
What happens after a vessel is injured
A vascular spasm
Platelets aggregate at the site Foreman a plug to seal the wound
Release of factors from platelets trigger the coagulation reaction and a fibrin mesh forms
What is a vessel spasm
A decrease in diameter of vessel by muscle contraction
What factors are released from platelets (3)
What do they do
ADP
Serotonin
Prostaglandin
Trigger the coagulation reaction, whereby fibrinogen is converted into fibrin by thrombin to form a gelatinous mash that provides a stable seal for the wound
What happens to the fibrinous mesh once the vessel wound is healed
Fibrinolysis follows
Plasminogen has to be converted into plasmin, which breaks down fibrin
Bradykinin relaxes the muscles and restores bloodflow
Give 4 functions of the lymphatic system
Returns interstitial fluid and plasma proteins to blood
Filters blood by removing harmful agents like toxins and microbes
Provides a structural basis for the immune system
Transports dietary lipids from the gastrointestinal tract to blood
Is the lymphatic system a closed circulation
No it is 1 way
Which is higher: hydrostatic or osmotic capillary pressure
Which are more permeable: lymphatic or blood vessels
Hydrostatic
Lymphatic
3 things that facilitate lymph flow
Breathing
Exercise
Good posture
Where does the thoracic duct enter into
Subclavian vein
What is elefantiasis
Parasitic infection (helminth) of the lymphatic system
Causes oedema
3 cells present in lymph
Lymphocytes
Macrophages
Dendritic cells
Where are B and T cells produced
B= bone marrow T= thymus
What do macrophages and dendritic cells do
Macrophages: clear dead cells
Dendritic cells: activate T cells
What are the secondary lymphoid organs
Lymph nodes
Spleen
Gut lymphoid
How many blood cells are produced a day
500 billion
Why does haematopoiesis decrease with age
Replacement of haematopoietic tissue with fat
It decreases faster in Lower limbs
What colour is fat
Yellow
How many lymph nodes are there
A few hundred
What part of the lymph-node receives lymph
What else is here
The sub calculus sinus received lymph from afferent lymphatic vessels
Macrophages
What is below the subcapsular sinus of the lymph nodes
The cortex and medulla, dense cellular areas of lymphocyte residence
What is the function of the spleen
Remove old red blood cells and filter blood-borne antigens
Also serves as the location for initiation of immune response to blood pathogens
Why is the spleen highly vascularised
To enable good blood filtration
Does the spleen have a capsule
Yes but it is weak
What is below the capsule of the spleen
A red blood cell rich area called the red pulp where and blood antigens are filtered and red blood cells removed
There is also a white blood cell rich area called the white pulp, where lymphocytes initiate immune responses to blood pathogens
How many lymphocyte clones can react with a specific antigen of the invading pathogen
How is this overcome
1 in 10^6
Recirculation of lymphocytes
Describe recirculation of lymphocytes
Naive lymphocytes transit through the blood, lymph-node‘s, spleen and return to the blood via the thoracic duct
Lymphocytes into limp nodes through venules called HEVs
Inside the lymph-node different lymphocytes concentrate in different areas: B cells home to follicles in the cortex, T cells home to the paracortex.
In these areas they can recognise and bind antigens brought by the lymph
How do lymphocytes encounter antigens
Antigen presenting cells angles microbes and then actively migrate to the nearest lymph-node
3 ways neutrophils kill bacteria
Phagocytosis
Production of cytokines and Antimicrobial enzymes
How do neutrophils move
Amoeboid fashion
Give 4 facts about nitric oxide
It generated by sheer stress on the endothelium of certain blood vessels
May up regulate factors involved in development of new vessels
Produced from L arginine
Vasodilator
