Physiology Flashcards
1
Q
what is homeostasis?
A
the maintenance of steady states within our bodies by coordinated physiological mechanisms
2
Q
what is feedforward?
A
responses made in anticipation of a change
3
Q
what is feedback?
A
responses made after a change has been detected
4
Q
what does positive feedback do?
A
amplifies an initial change
5
Q
describe the permeability of a cell membrane.
A
selectively permeable
6
Q
what are 4 functions of the membrane?
A
- controls entry of nutrient and exit of waste and secretory products
- maintains differences in ion concentration inside and outside the cell
- participates in joining of cells to form tissues and organs
- enables a cell to respond to changes in the cell’s environment
7
Q
what does the plasma membrane consist of?
A
lipids: phospholipids, cholesterol
proteins
small amount of carbohydrates
8
Q
describe a phospholipid
A
has a negatively charged hydrophilic head and an uncharged hydrophobic fatty acid tail.
9
Q
how are the phosphlipids positioned in the lipid bilayer?
A
hydrophobic tails facing each other, a row of hydrophilic heads facing intracellularly, another facing extracellularly
10
Q
what 2 things does cholesterol contribute to in the plasma membrane?
A
- fluidity
2. stability
11
Q
where are integral proteins in the plasma membrane?
A
embedded in the lipid bilayer
12
Q
where are transmembrane proteins in the plasma membrane?
A
extend through the membrane
13
Q
where are peripheral proteins in the plasma membrane?
A
don’t penetrate the membrane, are more commonly intracellulary
14
Q
short carbohydrate chains are often bound to membrane proteins and lipids as what molecules?
A
glycoproteins and glycolipids
15
Q
what layer do the the glycoproteins and glycolipids form?
A
glycocalyx
16
Q
why is the fluidity of the membrane important?
A
allows the cells to change shape (eg RBC or a muscle cell)
17
Q
what function do docking-marker acceptors have?
A
they are membrane proteins located on the inner membrane surface where they interact with secretory vesicles leading to the exocytosis of the vesicles contents
18
Q
what do cadherins do? (a type of membrane protein)
A
help hold cells within tissues together
19
Q
what do integrins do? (a type of membrane protein)
A
span the plasma membrane and act like a link between extra and intracellular environments
20
Q
what do membrane carbohydrates do?
A
serve as self-identity surface markers, ensure cells do not overgrow their own territory
[excepetion = cancer cell grow- abnormal surface markers]
21
Q
what are the 3 kind of specialised cell junctions?
A
- desmosomes
- tight junctions
- gap junctions
22
Q
what are desmosomes? (a type of specialised cell junction)
A
adhering junctions that anchor cells together, especially in tissues subject to stretching
23
Q
what are tight junctions? (a type of specialised cell junction)
A
they join the lateral edges of epithelial cells near their apical/lumenal membranes
(junctions can be tight or leaky)
24
Q
what are gap junctions? (a type of specialised cell junction)
A
communicating junctions that allow movement of charge carrying ions and small molecules BETWEEN two adjacent cells.
25
molecules and ions that can penetrate the membrane are passively driven across the membrane by what 2 forces?
1. diffusion down a concentration gradient
| 2. movement along an electrical gradient
26
What 5 factors influence the rate of diffusion across the membrane and collectively make up Fick's Law of Diffusion?
1. the magnitude of the concentration gradient
2. the surface area of the membrane across which diffusion is taking place
3. the lipid solubility of the substance
4. the molecular weight of the substance
5. the distance through which diffusion must take place
27
what is osmosis?
the movement of water down it's concentration gradient
28
what 2 ways can water pass through the membrane?
1. water molecules can permeate the plasma membrane
| 2. aquaporins (water channels)
29
what is osmolarity?
the concentration of osmotically active particles present in a solution
units = osmoles/litre
30
what is tonicity?
the effect a solution has on cell volume
| ie isotonic, hypotonic, hypertonic
31
what is the tonicity of saline solution (0.9% NaCl)?
isotonic
32
how does carrier mediated transport work?
substance binds onto a specific carrier which undergoes a conformational change and transports the substance
33
what are the 3 important characteristics which determine the kind and amount of material transferred across the membrane through carrier mediated transport?
1. specificity of substrate
2. saturation (transport maximum)
3. competition (a couple of substrates are available and the presence of both diminishes the rate of transfer for either)
34
what are the 2 forms of carrier-mediated transport?
```
facilitated diffusion (no energy required)
active transfer (energy required)
```
35
facilitated diffusion uses a carrier to facilitate the transfer of a substance across the membrane from ____ concentration to ____ concentration.
high concentration to low concentration
36
active transport uses a carrier to expend energy to transfer a substance across the membrane from a ____ concentration to a ____ concentration?
low concentration to a high concentration
| ie against a concentration gradient
37
Active transport comes in what 2 forms?
1. primary active transport (uses ATP)
| 2. secondary active transport
38
what type of carrier is the Na+K+ATPase pump?
primary active transporter
39
how many Na+ are transported out of the cell in? how many K+ are transported into the cell?
3Na+ is transported out
| 2K+ is transported in
40
what are the 3 important roles for the Na+K+ATPase pump?
1. helps establish Na and K concentration gradients across the plasma membrane
2. helps regulate cell volume by controlling intracellular solute concetration
3. energy used to drive the pump indirectly serves as the energy source for secondary active transport
41
what is the definition of secondary active transport?
the transfer of a solute across the membrane that is coupled with the transfer of the ion that supplies the driving force (typically Na+)
42
what are the 2 mechanisms of secondary active transport?
1. symport (co-transport)
solute and ion move in same direction
2. antiport (exchange or countertransport)
solute and ion move in opposite directions
43
what type of transport is vesicular transport?
active transport
44
what is exocytosis?
a vesicle fuses with the plasma membrane, releasing its contents to the ECF
45
what is endocytosis?
pinching off of the membrane to engulf substance
46
what does membrane potential refer to?
the electrical difference ECF and ICF
47
compare the permeability of the membrane to K and Na at resting potential
membrane 100x more permeable to K than Na
48
what is the Nernst equation?
allows you to calculate the equilbrium potential for any given ion
simplified: E(ion) = 61log([ion]o/[ion]i)
49
what affect does permeability of an ion have on the membrane potential?
the greater the permeability for a given ion, the greater the tendency for that ion to drive the membrane potential towards the ions own equilibrium potential
this is why the membrane potential is close to E(K) than E(Na)
50
What is the Goldman-Hodgkin-Katz equation?
used to calculate E(m)
51
What controlled variable to baroreceptors detect?
Mean arterial pressure
52
when baroreceptors detect a change in MAP, what is the control centre that they inform?
Medulla
53
when baroreceptors detect a change in MAP, what effectors does the Medulla bring about a response in?
```
heart (HR, SV)
blood vessels (TPR)
```
54
what type of feedback mechanism is the baroreceptor mechanism?
negative feedback
55
what is blood pressure?
the outwards hydrostatic pressure exerted by the blood on blood vessel walls
56
what is mean arterial blood pressure? (MAP)
the average arterial blood pressure during a single cardiac cycle
57
MAP =
| using blood pressures
[2DBP + SBP]/3
58
what is pulse pressure?
difference between SBP and DBP
59
what is the normal range of MAP?
70-105mmHg
60
what MAP is the minimum needed to perfuse the vital organs? (brain, heart, kidneys)
60mmHg
61
where are the 2 grous of baroreceptors?
aortic arch
| carotid sinus
62
what type of receptors are baroreceptors and what are they sensitive to?
baroreceptors are mechanoreceptors which are sensitive to strech
63
if there is an increased MAP, what happens to the firing rate in the afferent neurone?
increase firing rate in afferent neurone
64
if there is a decreased MAP, what happens to the firing rate in the afferent neurone?
decreased firing rate in afferent neurone
65
what is the site of 1st synapse for all CVS afferents?
Nucleus Tractus Solitarius (NTS) in the cardiovascular control centre of the medulla
66
what does the NTS do when receiving CVS afferent information?
relays information to other regions in the brain
67
a vagal ouflow to the heart is generated in the cardiovascular control centrein response to afferent CVS information and is relayed where?
to the nucleus ambiguus in the medulla
68
Mean Arterial Pressure (MAP) =
| using CO and TPR
CO x TPR
| SV x HR x TPR
69
what is the cardiac output?
the volume of blood pumped by each ventricle of the heart per minute
70
what is the stroke volume?
the volume of blood pumped by each ventricle of the heart per heart beat
71
what is TPR?
the sum of resistance of all peripheral vasculature in the systemic circulation
72
what 3 factors are regulated to control MAP?
heart rate,
stroke volume,
TPR
73
what is the name of the process of the heart beating rhythmically in the absence of external stimuli?
autorhythmicity
74
how is the intrinsic control of stroke volume managed?
Frank Starling Mechanism
75
what vessels in the CVS are the main resistance vessels?
arterioles
76
what increases TPR?
contraction of vascular smooth muscle (vasoconstriction)
77
what decreases TPR?
relaxation of vascular smooth muscle (vasodilation)
78
what is vasomotor tone?
tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline
79
what are the 2 areas of arterial smooth muscle where there is parasympathetic innervation?
penis and clitoris
80
what type of changes to baroreceptors respond to?
ACUTE changes in blood pressure
81
what hapens to baroreceptors firing if high blood pressure is sustained?
decrease firing, baroreceptors have re-set
82
why is the brain a glucose obligate tissue?
blood brain barrier makes brain inaccessible to plasma fatty acids
83
what levels of glucose count as hypoglycaemia and what can this cause?
4 is the floor
84
what negative effect can chronic hyperglycaemia cause?
damage to blood vessels
85
what 3 cell types are part of the pancreatic islets of langerhans?
alpha-cells
beta-cells
D-cells
86
what do alpha-cells from the pancreatic islets of langerhan release?
glucagon
87
what do the beta-cells from the pancreatic islets of langerhan release?
insulin
88
what do the D-cells from the pancretic islets of langerhan release?
somatostatin
89
what is the term which describes glucose in the urine?
glycosuria
90
immediately after a meal, and glucose rises, what hormone also rises?
insulin rises
| glucagon falls
91
what is the effect on insulin secretion on a carb-rich meal compared to normal mixed meals?
insulin secretion is much higher for a carb-rich meal than for a normal mixed meal
92
What is the function of insulin?
stimulates the uptake of glucose from the blood into muscle and fat cells
stimulates conversion of glucose into glycogen
stimulates conversion of fatty acids into triglycerides
stimulates conversion of amino acids into protein
(anabolism role)
hormone of the fed-state and overall lowers glucose concentration in the plasma
93
what is the function of glucagon?
stimulates conversion of glycogen into glucose
simulated the conversion of triglycerides into fatty acids
(catabolism role)
hormone of the hungry-state
94
what glucose transporter protein does insulin cause to be inserted into the plasma membrane of muscle and fat cells?
GLUT4
95
where does GLUT4 originally come from?
intracellular stores
96
what 5 factors promote the secretion of insulin?
1. increased glucose
2. increased amino acids
3. increased parasympathetic activity (ie eating)
4. increased glucagon
5. GIP (gastric inhibitory polypeptide
97
what 2 factors promote the inhibition of secretion of insulin?
1. decreased glucose
| 2. increased sympathetic activity (eg exercise)
98
Why does severe diabetes cause thirst?
high glucose concentrations in the urine cause large urinary volume, in addition to high glucose concentrations in the blood- dehydration
99
in severe diabetes, the cells are unable to utilise glucose. What chemical breakdown reaction has a compensatory increase in order to provide an alternative energy source?
lipolysis, generates fatty acids
100
why are ketone bodies formed in severe diabetes?
metabolism of fatty acids generates acetyl CoA. the liver is unable to process the excess acetyl CoA through citric acid cycle so they are converted to ketones instead.
101
what type of blood gas alteration occurs in severe diabetes?
metabolic acidosis
| blood pH is lowered
102
in severe diabetes, what mechanism tries to compensate for the metabolic acidosis?
compensatory hyperventilation
103
compare the onset of type 1 and type 2 diabetes.
type 1- childhood
| type 2- usually adulthood
104
compare the levels of insulin in the body of type 1 and type 2 diabetes
type 1- little/no insulin secretion
| type 2- normal/high
105
which is the predominant diabetes type, type 1 or type 2?
type 2 (80-90%)
106
which diabetes can cause ketosis to develop?
type 1
107
what is the treatment for type 1 diabetes?
insulin injections
108
what is the treatment for type 2 diabetes?
diet/exercise and oral drugs for treatment
109
compare the development of symptoms between type 1 and type 2 diabetes
type 1- symptoms develop rapidly
| type 2- symptoms develop slowly
110
what 3 factors stimulate the release of glucagon?
decreased blood glucose
amino acids
sympathetic nervous activity
111
what 2 factors inhibit the release of glucagon?
raised blood glucose
| insulin
112
what 3 ways does glucagon raise plasma concentrations of glucose?
increases liver glycogenolysis
inhibites liver glycogen synthesis
promotes liver gluconeogenesis
113
what are the serious consequences of starvation?
protein catabolism and muscle wasting
114
from the connective capsule to the medulla, describe the layers of the adrenal gland?
```
connective tissue capsule
zona glomerulosa
zona fasciculata
zona reticularis
medulla
```
115
what part of the adrenal gland produces aldosterone?
the zona glomerulosa of the adrenal cortex
116
what part of the adrenal gland produces cortisol?
the zona fasciculata
117
what part of the adrenal gland produces sex hormones?
zona reticularis
118
what part of the adrenal gland produces adrenaline?
storage granules of the medulla
119
what rhythm does cortisol secretion exhibit?
diurnal rhythm
| plasma cortisol concentration peaks in the morning, falls over the day and it lowest in the night
120
what are adrenaline and cortisol released in response to?
stress
121
what are the 2 functions of adrenaline in terms of glucose concentration of the plasma?
raises glucose concentration of the plasma by :
1. stimulating glycogenolysis
2. stimulating gluconeogenesis
122
what are the 3 functions of cortisol?
1. raises glucose concentration of the plasma by stimulating gluconeogenesis
2. stimulates protein catabolism
3. stimulates lipolysis
123
compare adrenalin and cortisol in terms of there effectiveness for rapid mobilisation of fuel
adrenaline is important in the rapid mobilisation of fuel, cortisol is not
124
where is growth hormone produced?
anterior lobe of the pituitary gland
125
in response to starvation what 3 functions does the growth hormone have?
1. decreases glucose uptake by muscle- 'glucose sparing'
2. mobilised glucose from liver
3. promotes lipolysis in fat cells
126
what hormone(s) is/are important for raising glucose concentration in the blood in emergencies?
adrenaline
127
what hormone(s) is/are important for maintaining glucose concentration in the blood during starvation?
cortisol, growth hormone
128
what is defined as the core body temperature?
the temperature of structures deep within the body
129
what is the term that described the normal core body temperature?
normothermia
130
what happens to cellular metabolism as body temperature increases?
cellular metabolism increases
131
what are the 4 main detrimental effects of overheating?
protein denaturation
nerve malfunction
convulsions
death
132
what happens if the body temperature decreases?
slowing down of cellular reactions, may fatally slow down metabolism
133
what type of variation is seen in body temperature?
diurnal variation
| lowest temp early in the morning
134
how may body temperature be altered? (give 4 ways)
activity
emotions
exercise
exposure to extremes of temp
135
when in the menstrual cycle do females have a slightly higher temperature?
2nd half of the cycle (after ovulation)
136
how is heat gained from the internal environment?
metabolic heat
137
how is heat gained from the external environment?
mainly radiation
(convection
conduction)
138
how is heat lost to the external environment?
convection
conduction
radiation
evaporation
139
what is metabolic heat?
heat produced from the oxidation of metabolic fuel derived from food in the body
140
what is the Basal Metabolic Rate? (BMR)
the minimum amount of energy required to sustain vital body functions, leads to basic level of heat production
141
what 3 hormones can increases the BMR?
adrenaline
noradrenaline
thyroxine
142
what type of fat is involved in thermogenesis in young children?
brown fat
143
What is radiation?
emission of heat energy in the form of electomagnetic waves from a surface
(elecromagnetic waves trave through space and transform into heat on striking another surface)
144
how much of the body's heat is lost through radiation?
50%
145
what is conduction?
transfer of hear between object in contact
146
with regards to conduction, how does heat move?
from warmer to cooler object
147
what 2 factors does heat transfer depend on?
temperature gradient
| thermal conductivity
148
what is convection?
transfer of heat energy by air (or water) currents
149
what can increase the combined effect of conduction-convection? (dissipation of heat)
forced air movement
150
which is a better thermal conductor, air or water?
water
151
what body mechanism works by active evaporation?
sweating
152
what part of the ANS is sweating controlled by?
sympathetic nervous system
153
how is evaporation result in heat loss?
energy is required to convert water in the skins surface and the lining of the respiratory airways into vapour
154
what type of evaporation occurs continuously and is not under physiological control?
passive evaporation
155
what type of feedback system controls body temperature?
negative feedback
156
what 2 types of thermoreceptors are there?
central thermoreceptors
| peripheral thermoreceptors
157
where are central thermoreceptors located?
hypothalamus, abdominal organs, other areas
158
where are the peripheral thermoreceptors located?
in skin
159
what is the control centre for the negative feedback loop of thermoregulation?
hypothalamus
160
what 3 effectors are important in the negative feedback loop of thermoregulation?
skeletal muscle
skin arterioles
sweat glands
161
what type of inputs come to the hypothalamus from the negative feedback receptors for thermoregulation?
neural inputs
162
what part of the hypothalamic centre is activated by cold?
posterior hypothalamic centre
163
what part of the hypothalamic centre is activated by warmth?
anterior hypothalamic centre
164
in response to stimulation of the posterior hypothalamic centre, what do skin arterioles do?
vasoconstrict (decreased heat loss)
165
in response to stimulation of the posterior hypothalamic centre, what physiological involuntary action do skeletal muscles do?
increase muscle tone,
shiver,
(increased heat production)
166
in response to stimulation of the posterior hypothalamic centre, what voluntary action do skeletal muscles do?
increase voluntary movement (increased heat production)
| postural changes, warm clothing (increased heat loss
167
in response to stimulation of the anterior hypothalamic centre, what physiological involuntary action do skin arterioles do?
vasodilation (increases heat loss)
168
in response to stimulation of the anterior hypothalamic centre, what physiological involuntary action do sweat glands do?
increased sweat production (increased heat loss)
169
in response to stimulation of the anterior hypothalamic centre, what physiological involuntary action do skeletal muscles do?
decreased motor tone
| decreased heat production
170
in response to stimulation of the anteior hypothalamic centre, what voluntary action do skeletal muscles do?
```
decreased voluntary movement (decreased heat production)
cool clothing (increased heat loss)
```
171
what are endogenous pyrogen? (eg interleukins)
chemicals released from macrophages, produced in response to infection or inflammation and stimulate the release of prostaglandins in the hypothalamus
172
what does prostaglandins release in the hypothalamus achieve?
reset the thermostat in the hypothalamic thermo-regulatory centre to a higher temperature- fever
173
when will the hypothalamic set point be restored to normal after pyrogenic release has caused it to alter?
when pyrogen release is reduced or stopped
OR
prostaglandins synthesis is decreased or stopped
174
temperature of 38-40 =
fever
175
temperature greater than 40 =
hyperthermia
176
temperature below 35 =
hypothermia
