Homeostasis Flashcards
Describe the reasons for a Fever/Pyrexia
This occurs due to a release of endogenous pyrogens (EPs = cytokines) that are released into the circulation –> causing thermoregulatory responses
This releases heat production, whilst reducing heat loss –> causing the core temperature to rise
This higher body temperature then stabilises
What causes Rheumatoid Arthritis?
A swollen/inflammed synovial membrane
What effect does an increase in wind have?
Increases heat output
Define what is meant by the ‘Musculoskeletal System’
The skeleton, muscles and accessory tissues which together allow locomotion and articulation
Describe the regulation of 1,25(OH)2 D3 production
The skin converts Vitamin D3 into 25(OH)D3, which is then converted to 1,25(OH)2 D3 due to the secretion of PTH
The formation of this molecule causes an increase in Ca2+ and a reduction in PO4^3- –> which inhibits PTH secretion and the conversion of the first step
The amount of inactivation (first molecule to 24,25(OH)2 D3) also effects the amount of 1,25(OH)2 D3 that is in the body
What is the recommended physical activity level per week?
150mins of moderate activity
Explain how Endochondral Ossification occur?
Hylaine cartilage is formed, creating a matrix for real bone to replace later on
Once the bone is formed there is some cartliage left in the Epiphyseal Plate –> which is used for further growth in the future
Define Healthy Nutrition and Malnutrition
Healthy Nutrition - A balanced diet that contains adequate amounts of nutrients in relation to bodily requirements
Malnutrition - Any physical condition resulting either from an inappropriate or inadequate diet that either provides too much or too little of a necessary nutrient
What are the two types of vitamins in the body?
Water soluble = not stored
Fat soluble = stored
Describe the main points of a synovial joint
Hylaine Cartilage covers the end of the bones
A fibrous layer that attatches to the periosteum
An inner synovial membrane that produces synovial fluid
What are the 4 types of bone?
Long/trabecular
Flat
Short
Irregular
Explain how intramembranous Ossification
The bone is formed directly from inside of the condensation
No cartilage is used
What is Calcitonin?
A single chain polypeptide
It is secreted more when there is high [Ca2+]
Its effect is to reduce body Ca2+ levels –> so it has the opposite effects to PTH
Describe 1,25 (OH)2 D3
It is an active metabolite of Vitmain D3
Its a secosteroid (due to its open B ring)
Its a very lipohillic molecule so it needs to be carried by transcalciferin (a vitamin D binding protein) –> only the unbound molecule is active
The molecule acts on osteocytes/blasts, as well as nuclear receptors
What are the three different types of cartilage?
Hylaine - Found in growth plates, joint surfaces and the temporary bone scaffold
Fibrocartilage - Found in the menisci and intervertabral discs –> There is NO fibrous perichondrium
Elastic - Present in the inner ear, epiglottis and larnyx
What is the difference between Hypercalcemia and Hypocalcemia?
Hypercalcemia - When there is too much PTH –> so too much Ca2+ is formed
Hypocalcemia - When there is PTH resistance, or a lack of Vitmain D intake
Is body temperature normally warmer or cooler than the outside temperature?
Warmer
Long bones are made up of many units that work together, so they are refered to as….
A modular tissue
List why fats are important in the diet
They are a good source of essential fatty acids (alpha linoleic acid and linoleic acid)
They acts as carriers for fat soluble vitamins
They are used for membrane synthesis, as well as glycolipids and steroid hormones
Explain how post-natal bone growth occurs
Chondroblasts in the Epiphyseal Plate quickly divide, lengthening the bone
Old chondrocytes then enlarge, triggering the calcification of the matrix
The matrix becomes calcified, whilst the chondrocytes die
Osteoclasts then digest the cartilage, whilst osteoblasts replace it with actual bone
How does the body cope when above/over 37 degrees
Above - Sweating, vasodialation and shievering in order to get blood into the periphery
Below - Vasoconstriction and horripilation
Define BMR - TEE - PAL - EAR
Basal Metabolic Rate - The mimimum amount of energy required to maintain vital functions
Total Energy Expenditure - The combination of BMR + energy needed to process food + physical activity
Physical Activity Level - A 24hr index of energy expenditure due to physical activity
Estimated Average Requirement - BMR x PAL
Explain the differences between an Osteoblast - Osteocyte - Osteoclast
Osteoblast - A cell that forms the bone matrix by several working together
Osteocyte - A cell that maintains the bone tissue, and is formed by several osteoblasts becoming imbedded into the membrane
Osteoclast - A multinucleated cell that breaks down and absorbs old bone during growth
How much calcium is the ultrafiltrate is reabsorbed?
Almost all of it
“Humans are homeothermic” means what?
They are warm-blooded
Where is the biggest store of calcium in the body?
The bone
What is PTH?
What does it do?
Where is it produced/released?
Parathyroid Hormone
It is a single chain polypeptide that srimulates both osteoblasts and osteocytes (and osteoclasts indirectly) –> its also got a short half-life, so its effects are only for a small period of time
- The purpose of this is to increase plasma Ca2+ levels
Its produced in the chief cells of the parathyroid gland
The less ionized calcium that is present –> the more PTH is secreted
Explain the importance of the hypothalamus in terms of thermoregulation
The hypothalamus takes in all the information from thermoreceptors in the periphery and the core and compares it to the set point of 37oC
Above 37 - Detected in the anterior hypothalamus
Below 37 - Detected in the posteriour hypothalamus
Why are many dietary carbohydrates a good source of fibre?
And why are they useful?
Many polysaccharides are plant based, and so they can’t be broken down
These can then add bulk to the GI tract
They’re also useful for the production of short chain fatty acids
What is the RNI for protein per day?
0.75g/Kg
What is embryonic mesenchyme?
An early bone cell that is undifferentaited, which aggregate to form a condensation
What are the three layers that make up a bone?
Compact = Exterior
Trabecular = Interior
The bone is then incased in a fibrous periosteum
What is the Thermoneutral Zone (TNZ)
The range of ambient temperatures over which the heat produced from basal metabolism is sufficient to maintain the bodies core temperature
Above the temperature there is a net gain of heat –> where as below there is a net loss of heat
What are the functions of the bone?
Support
Protection
Lipid storage
Formation of RBC’s from red marrow (in young bones)
Endocrine function for carbohydrate metabolism
What deficiencies can cause Anaemia?
Iron
Vitamin B12
Which vitamins are water soluble?
B’s and C
What type of calcium is physiologically active?
Ionized and Unbound
In what type of bones is cartilage used to form a temporary scaffold?
Long bones
What are the two subsections of the skeleton?
Axial - Bones of the skull, vertebral column and ribs (80)
Appendicular - Bones of the limbs , pelvis, scapular and clavicle (126)
What are the 6 types of synovial joint?
Planar - Hinge - Pivot - Condyloid - Saddle - Ball and Socket
Who, on average, have a greater bone mass… men or women?
Men
Why does temperature change during pregnancy?
The basal tempreture is raised due to the effects of progesterone
How does Bone Regeneration occur?
A hematoma is produced from the produced blood
A callus is formed between the ends of the bones
Spongy bone replaces the calluses (ossification)
Pure bone replaces the spongy bone
