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NLM1 (semester 2) > Physiology > Flashcards

Physiology Flashcards

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1
Q

What is the function of articular cartilage and of Growth plate cartilage?

A

Articular cartilage - Shock absorber.

Growth plate cartilage - Facilitate longitudinal growth of long bones.

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2
Q

What are the main components of the hyaline cartilage matrix?

A

Collagen
Proteoglycans (aggrecan)
Water (70-80%)

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3
Q

In which disease is cartilage erosion a problem?

A

Osteoarthritic cartilage.

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4
Q

What happens when aggrecan (a proteoglycan of articular cartilage) is degraded? why is this so? what is this condition called?

A

Osteoarthritis

Pain - due to exposed bone (bone has nerves unlike cartilage.

Loss of shock absorbing ability.

Inflammation.

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5
Q

What is strontium ranelate?

A

A drug which retards progression of osteoarthritis.

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6
Q

Two types of bone formation and what the bone matrix is deposited on in both?

A

Intramembraneous - Membrane.

Endochondral bone formation - Cartilage.

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7
Q

What factor mostly contributes to bone growth?

A

Chondrocyte hypertrophy.

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8
Q

In endochondral ossification what happens in the calcification zone and in the resorption zone?

A

Calcification zone: Dissolved minerals calcify the matrix giving calcified hyaline cartilage matrix

Resorption zone (below the calcification zone): Osteoclasts dissolve the calcified matrix and leave spicules of trabeculae.

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9
Q

What is an anlage?

A

Like a cartilaginous template for bone formation.

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10
Q

Factors that affect the healing of fractures?

A

Foreign bodies, infection, Degree of mobility around the fracture wound ends, level of vascularity, chemo/radiotherapy

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11
Q

Why do we have bone?

A

Support and protection

Movement

Store for metabolic calcium

Store for bone marrow

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12
Q

Difference in the bone matrix and the cartilage matrix?

A

Consistency: Bone - Minerlised hard tissue. Cartilage - Permeable hydrated gel.

Organic matrix: Bone - 90% collagen (type I), 4% proteoglycans, Cartilage - 40% collagen (Type II) 60% proteoglycans

Growth: Bone - appositional, Cartilage - interstitial

Vascularity - Bone - Dependent on vascular supply Cartilage - avascular.

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13
Q

What is osteogenesis inperfacta?

A

‘brittle bone disease’ a mutation in or absence of type I collagen, causing bones to fracture easily.

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14
Q

Range for plasma concentration of Ca?

A

2.25-2.5 mmol/L

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15
Q

What Three things are mostly involved in the regulation of Plasma Calcium?

A

Parathyroid hormone

Calcitriol (steroid hormone)

Calcitonin (peptide hormone)

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16
Q

Where is calcium mostly located in the body?

A

Bone - 99%

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17
Q

What two pools of calcium exist in the plasma?

A

Diffusible pool - Free/unbound Ca, and some complexed with small MW compounds.

Non-diffusible pool - bound to Ca-binding proteins and plasma proteins.

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18
Q

In alkalosis (high pH) is there going to be hyper or hypocalcaemia? Why?

A

Hypo:

Fewer H+ bound to proteins
Favouring the binding of proteins to calcium
The amount of calcium in the non-diffusible pool rises and the diffusible pool falls.

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19
Q

In acidosis (low pH) is there going to be hyper or hypocalcaemia? Why?

A

Hyper:

More H+ bound to proteins
Favouring the binding of proteins to H+
The amount of calcium in the diffusible pool rises and the non- diffusible pool falls.

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20
Q

How are Calcium levels regulated by PTH?

A

G-protein coupled Ca receptors monitor the plasma levels of Ca and secrete PTH In low Plasma Ca concentrations.

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21
Q

In the Liver Vitamin D is converted to what? which is the major form of Vit D in the circulation.

A

25OHD3.

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22
Q

In the kidneys 25OHD3 is converted into what two things?

A

The biologically active form (Calcitriol) and a degradation product - 24, 25(OH)2D3

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23
Q

What does calicitriol do?

A

Intestine: Promotes the absorption of dietary Ca2+

Bone: promotes mineralization of osteoid (deposition of Ca2+ and PO4 2-

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24
Q

What happens when the plasma level of Ca rises above normal?

A

PTH secretion by the parathyroid gland ceases.
Bone resorption decreases.
Renal excretion of Calcium increases.
25(OH)D3 is not converted into calcitriol.
Intestinal absorption of dietary Ca decreases.

Calcitonin is produced which also reduces bone resorption.

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25
What is the most common cause of hypercalcaemia and hypocalcaemia?
Hyperparathyroidism (excessive secretion of PTH) usually due to an adenoma. Hypoparathyroidism (could be due to surgical removal of thyroid or congenital PTH deficiency§
26
Will Hypocalcaemia cause increased or decreased excitability of muscles?
Increased excitability due to raised resting potential.
27
Will Hypercalcaemia cause increased or decreased excitability of muscles?
Decreased excitability, due to decreased resting potential.
28
Signs of hypocalcaemia?
Anxiety, Abnormal tingling sensations (Paraestesia), Periodic spasms (tetany).
29
Signs of Hypercalcaemia?
Depression, tiredness, muscle weakness and slow muscle contraction.
30
Most common cause of Vit D deficiencies?
Lack of UV exposure.
31
Problems associated with Vit D deficiency?
Rickets/Osteomalacia due to decreased intestinal absorption of dietary Ca2+.
32
Treatment for rickets and osteomalacia?
Vitamin D and Calcium administration.
33
What is healing by first intention?
Incised clean wound, with minimal tissue damage. Minimal bacterial colonisation. Edges are promptly drawn together.
34
What is healing by second intention?
A wound that does not fulfil the categories for healing by first intention so it can have one of these factors: Significant tissue destruction. Infection. Edges not opposed.
35
Process of healing by first intention?
Blood clot and scab. Acute inflammation, re-epithelisation and phagocytosis. Proliferation of capillaries and fibroblasts (granulation tissue) Inflammation subsides, vascularity decreases and collagen increases Mature scar formed.
36
Process of healing by second intention?
Blood clot covers surface of cut. Acute inflammation. Chronic inflammation, granulation tissue formation and re-epithelialisation. Granulation tissue gradually fill the defect (weeks to months) myofibroblasts and remodelling reduce the size of the scar.
37
What types of collagen fill wounds?
Type I first Type III Later.
38
What is a keloid scar?
one that extends beyond the original site of injury.
39
How is healing by first and second intention promoted in bone healing?
Simple splinting - First intention. Close surgical apposition - second intention.
40
What is the hierarchal arrangement of a muscle?
Muscle > Fascicle > Muscle cell > myofibril > sarcomere
41
What is the I band?
Band consisting of only actin.
42
What is the H zone?
Band consisting of only myosin.
43
What is the A band?
The whole region that myosin covers, including the H zone.
44
What binds to the Z line?
Titin and Actin.
45
What is the M line?
The line in the middle of the H zone that myosin filaments radiate from.
46
How many actin filaments surround a myosin filament?
6 actin filaments.
47
What chains does myosin consist of?
2 heavy chains 4 light chains
48
What is the structure of the actin filament?
Includes actin subunits that polymerise to form chains.Troponin.Tropomyosin.
49
What does the troponin complex consist of?
Tn-C (calcium binding)Tn-I (Inhibitory subunit)Tn-T (Tropomyosin binding)
50
What is the process of myosin binding to actin, from the beginning with no calcium?
At first the myosin head (in the presence of a small ca2+ concentration) has ADP and Pi bound to it.When Ca2+ concentration is high, Ca2+ binds to the Tn-C on troponin and causes a conformational change dragging tropomyosin with it, and revealing myosin binding sites.The myosin head binds.Pi is released which causes a conformational change and produces the power stroke (the actin is dragged 11nm past the myosin fibres.The myosin head then binds ATP which causes it to dissociate and the head then quickly hydrolysed to ADP and Pi, cocking it to the starting position again.
51
What is Duchenne muscular dystrophy?
The common form of muscular dystrophy, causes rapidly progressing muscle weakness and atrophy of muscle tissue.
52
What is the sarcolemma, the T-tubule system and the sarcoplasmic?
Sarcolemma is the folded part of the Motor end plate, which navigates the action potential through the tissue by the T - tubule system, the impulse then travels to the sarcoplasic reticulum which is the specialised endoplasmic reticulum of muscle cells, specialised in secreting Ca2+ ions.
53
What are Ryanodine receptors?
They are receptors that are located on the sarcoplasmic reticulum and release Ca2+ ions in response to depolarisation of the T-tubule system.
54
What conditions can result from defective ryanodine receptors?
Malignant hypothermia. Caused by an excessive release of Ca2+ into the SR, which can then lead hyper metabolism as the body tries to replenish lost ATP.
55
What are the three main sources for ATP replenishment?
Creatine phosphateMuscle glycogen cellular respiration
56
What is creatine kinase and what are the three forms?
The enzyme that converts creatine phosphate and ADP to ATP and creatine. MM (muscle) BB (Brain) MB (cardiac tissue)
57
What parts of the CNS regulate motor activity?
Cerebral cortex Basal ganglia Cerebellum Spinal cord
58
What is the LMN/Alpha neurone (lower motor neurone)?
Any neuronal output from the spinal cord.
59
Are LMN's myelinated or unmyelinated?
myelinated?
60
Is there are sensory integration in the LMN?
Nope, none once neurone leaves the spinal cord.
61
What area of the spinal cord do LMN's come from?
The Ventral horn.
62
If a neurone had fine motor control would it innervate a large or small number of motor neurones?
A small number.
63
What is a motor unit?
The group of fibres activated by a single motor neurone.
64
what lamina of the spinal cord are motor neurone cell bodies located
lamina IX
65
What is a terminal bouton?
A site of transmitter release on the motor end plate.
66
What is the function of the junctional folds in a NMJ?
To increase the cell surface area.
67
What is an EPP?
An end-plate-potential
68
How does Ach activate a nicotinic type 2 receptor at a NMJ?
Two Ach molecules bind to the alpha sub unit.
69
What is the result of Ach binding to the nicotinic receptor at the NMJ?
Influx of Na+ and efflux of K+, causes local depolarisation which then can go on to cause the opening of voltage dependent Na+ channels at the junctional folds.
70
What is summation of end plate potentials, and why is this important?
Summation is increased frequency of EPP's to produce smoother contraction, and increased tension.
71
What happens when an action potential is generated at a NMJ?
The AP is carried throughout the T-Tubule system, leading to calcium release and muscle contraction.
72
What is tetanus in reference to the NMJ?
Smooth contraction resulting in the generation of maximum tension.
73
Will an AP in a motor neurone always result in a muscle contraction?
Yes - a single AP will result in one muscle twitch.
74
Three possible consequences of denervation?
Flaccid paralysis, possible initial fasciculation, atrophy.
75
What is denervation hypersensitivity?
The redistribution of Ach receptors along the length of the muscle fibre, resulting in hypersensitivity to Ach along the whole nerve.
76
What types of glial cells are there within the PNS and the CNS?
In the CNS: Astrocytes, Microglia and Oligodendrocytes.In the PNSSatellite cells, Microglia (a few) and Schwann cells
77
What are microglial cells?
Like 'brain macrophages' They Phagocytose dying cells in development, and mostly consist in a down-regulated phenotype. They are activated in many neurological conditions e.g. Stroke, dementia, head injury.
78
What is prominent in the soma of a neurone?
Rough ER (Nissl bodies)Free RibosomesGolgi Mitochondria
79
Differences in Axons and Dendrites?
Dendrites:- Receive chemical input and converts to electrical output- Has Ribosomes and mRNA (protein synthesis occurs)- Branched, unmyelinated and covered in spines- Decreasing diameterAxons:- Converts electrical input to chemical output- No mRNA and no ribosomes - Single process, can be myelinated- Constant Diameter
80
What are the three types of Synapses?
Axo-dendritic (normally excitatory)Axo-somatic (axon-cell body)Axo-axonic
81
What is Temporal and Spatial integration
Temporal: Summation of EPSPs generated at the same synapse assuming they occur within rapid successionSpatial: Summation of EPSPs generated by multiple inputs
82
What are astrocytes and what are some of their roles?
Multipolar cells with long processes, located throughout the CNS function in the BBB, Scar formation, maintenance of local Hormones and regulation of homeostasis.
83
How do Astrocytes maintain the levels of local hormones?
Take K+ from the extracellular space, take up neurotransmitters such as glutamate, convert this to glutamine.
84
What are two examples of sensory systems in the musculoskeletal system?
Golgi tendon organs and muscle spindles.
85
What do the sensory systems of the musculoskeletal system sense?
``` – Muscle length – Muscle tension – Joint position – Acceleration – Magnitude of movement ```
86
What is the muscle spindle structure?
Runs in parallel with the muscle fibres, in intrafusal muscle fibres. The central portion of the muscle fibres are non-contractile. Upper and lower portions are contractile. 1A sensory afferents wind around the non-contractile area and detect changes in muscle length. The small diameter gamma motor neurones innervate the contractile elements.
87
What are the roles of the Alpha and Gamma neurones in the muscle spindle, and in the tendon reflex?
Activation of the 1a (alpha) sensory fibres (caused by lengthening of the muscle) causes muscle contraction (so as to return the muscle to it's previous state of contraction), activation of the Gamma neurones causes spindle shortening in order to cope with muscle contraction (so both are at the same length).
88
What is the process of a tendon reflex?
1A sensory neurone is activated, causing activation of homonymous muscle and heteronymous muscle, and inhibition of antagonistic muscle, (see diagram for more info).
89
How does Increasing the overall excitatory tone in the descending motor neurones result in an amplified reflex response?
Results in the recruitment of a pool of LMN's that would not normally fire in response to the stimulus.
90
Is the muscle reflex response to pain mono or polysynaptic?
Polysynaptic
91
How is the tendon reflex modulated?
Through descending motor pathways and the corticospinal pathway
92
What are renshaw cells and what is their role?
They are an interneurone that receives input from a branch of the LMN, which then goes to project back and stimulate the same LMN and an inhibitory interneurone. They are involved in a feedback mechanism to prevent damage to muscles during tetanic stimulation.
93
Where are golgi tendon organs located?
Between the termination of muscle fibres and the tendon.
94
What is the function of a golgi tendon organ and how is this achieved?
Function is to detect changes in muscle tension Achieved as 1b sensory afferents increase in firing rate as muscle tension increases. the 1b afferent synapses with an inhibitory interneurone and the activity of the LMN is reduced.
95
What are the different things that a muscle spindle will detect and change and a golgi tendon organ will detect and change?
muscle spindle - length of muscle Golgi tendon organ - tension of organ
96
What other electrical integration id received by the inhibitory interneurone activated by the golgi tendon organ?
- Cutaneous mechanoreceptors - Joint receptors - Descending motor pathways
97
What type of impulse is a simple stretch reflex, e.g. poly/monosynaptic and inhibitory/excitatory?
Monosynaptic and excitatory.
98
What are the four types of axons in the sensory system? Which is fastest and which is slowest?
A(alpha), A(beta), A(delta) and C fibres. A(alpha) is the fastest and C is the slowest.
99
What do each of the different types of axon respond to?
A(alpha) - proprioceptors of skeletal muscle A(beta) - Mechanoreceptors of the skin A(delta) - Pain, temperature C - Temp, Pain and Itch
100
What are the five Mechanoreceptors in the skin, that respond to changes in pressure?
Merkels disc Meissner's corpuscles Hair follicle receptor Pacinian corpuscle Ruffini's ending
101
What axons travel from peripheral mechanoreceptors?
A(beta) axons
102
What is a point discrimination test?
Test used to determine the receptive fields of receptors (how large an area that one receptor can sense).
103
Do fast or slow mechanoreceptors undergo adaptation quicker?
Fast mechanoreceptors.
104
Is adaptation due to the neuronal or structural component of the receptor?
The structural component.
105
Are C fibres myelinated or unmyelinated?
Unmyelinated.
106
In what two ways can pain receptors be activated?
Directly by chemical stimuli. Indirectly by mediators of tissue damage.
107
What is meant by the fact nociception is biphasic?
That fast and slow nociceptors are activated simultaneously, producing both the sharp pricking pain and the dull ache.
108
What axons are cold receptors and what axons are warm?
Cold - A-(delta) fibres Warm C fibres
109
Outline the process of a simple knee jerk reflex.
Muscle spindle is stimulated 1A afferent sensory fibre with it's cell body in the dorsal root ganglia is activated It then synapses with an alpha motor neurone which then stimulates the muscle
110
What are spinal reflexes modulated by?
Descending motor pathways, and therefore Upper Motor Neurones.
111
What are valgus and varus deformities of the leg?
Varus - distal part towards the midline (outwards facing) Valgus distal part away from the midline (inwards facing)
112
How would you investigate a possible orthopaedic problem in the legs?
Look, feel and move. Gait assessment.
113
What is femoral anteversion?
When the femoral head has rotated anteriorally.
114
What is flexible flat foot?
No arch until 5 years resulting in a flat foot, no reason to treat in most cases.
115
What is DDH?
Developmental Dysplasia of the Hip. Refers to any manifestation of disability, dislocation or dysplasia of the hip. Can become arthritic at age 20.
116
What is Legg Calve Perthes Disease?
Idiopathic avascular damage to the femoral head.
117
What is the difference in a demyelinated versus an axonal injury?
Demyelinating - Loss of myelin results in slow conduction which is often reversible Axonal - Loss of excitable tissue - results in loss of amplitude and is often irreversible
118
Three classifications of nerve injuries?
Neuropraxia - Mildest form following pressure over the nerve causing ischaemia and demyeination (dead arm). Axonotmesis - Axonal damage, can cause muscle atrophy and recovered through reinnervation. Neurotmesis - most severe, complete axonal break, requires nerve repair.
119
What is the function of an EMG machine/NCS machine?
For the assessment of patients with neuromuscular diseases.
120
What is a fasciculation and a fibrillation?
A fasciculation is the spontaneous discharge of an entire motor unit A fibrillation is the spontaneous discharge of a single muscle fibre.

NLM1 (semester 2) (8 decks)

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