Physiology Flashcards
1
Q
What term describes
“Maintenance of steady states within our bodies by coordinated physiological mechanisms essential for function and survival of cells”?
A
Homeostasis
2
Q
What types (2) of cells are influenced by changes to membrane potential?
A
Muscle and nerve cells
3
Q
What are the 2 types of physiological controls to maintain homeostasis?
A
Intrinsic - local and inherent to organ
Extrinsic - accomplished by nervous and endocrine system
4
Q
What is a response made in ANTICIPATION of change known as? Give an example.
A
Feedforward.
Exercise.
5
Q
What is a feedback response?
A
Response AFTER change has been detected
6
Q
What are the 2 types of feedback response?
Give an example for each
A
Positive - AMPLIFIES initial change (E.g. Uterine contraction during labour)
Negative - OPPOSES initial change (E.g. BP, Temp)
7
Q
What are the 3 components in a feedback response? (Closed-loop)
A
Sensor - monitors MAGNITUDE
Control centre - COMPARES with a SET POINT
Effector(s) - RESPONSE to bring desired effect
8
Q
What is the purpose of the baroreceptor reflex?
A
Short-term moment to moment control of MAP
9
Q
What is blood pressure?
A
Outwards hydrostatic pressure exerted on arteries during cardiac contraction (Sytole) or relaxation (Diastole)
10
Q
What is the cut-off for hypotension?
A
=/< 90/60mmHg
11
Q
What is the normal pulse pressure range?
A
30-50mmHg
12
Q
Is CO and SV based on both or 1 ventricle?
A
1 ventricle
13
Q
What is the normal MAP range?
A
70-105mmHg
14
Q
At least how much MAP is needed for vital perfusion?
A
60mmHg
15
Q
What are the 3 components in a baroreceptor feedback response for MAP?
A
Sensor: Baroreceptor (Carotid sinus/ bifurcation via CN IX/ Hering’s nerve) & (Aortic arch via CN X)
Control centre: Medulla oblongata
Effectors: Heart (HR, SV) and Blood vessesls (SVR)
16
Q
How does MAP affect the firing rate of the afferent neurons of the baroreceptors?
A
MAP rises - firing rate increases
MAP decreases - firing rate decreases
17
Q
What is SVR?
A
Sum of all resistance of all vasculature in the systemic circulation
18
Q
How much effect does CN X have on ventricular contractility?
A
Little
Mostly by sympathetic
19
Q
What are the major resistance vessels? (Biggest change in pressure)
A
Arterioles
20
Q
What regulates SVR?
A
Vascular smooth muscle - changes diameter thus resistance
21
Q
Why are arterial smooth muscles partially contracted at rest?
A
Due to vasomotor/ sympathetic tone where there is tonic/continuous discharge and release of noradrenaline by sympathetic nerve
22
Q
Parasympathetic innervation of arterial smooth muscle can be found in ONLY which body parts?
A
Penis and clitoris, otherwise no.
23
Q
What happens when firing rate of afferent baroreceptor neurons decrease?
A
Reduced cardiac vagal efferent nerve fiber activity
Increased cardiac sympathetic efferent nerve fibre activity
Increased sympathetic vasoconstrictor nerve fibre activity
24
Q
Sympathetic constrictor tone influences which vessels and what are the outcomes of each?
A
Veins - influences venous return hence SV
Arteries - influences SVR
25
What happens to the firing of baroreceptors in CHRONIC high BP?
Firing rate decreases
| Only resets and fires again if there is an acute change above the NEW set point
26
How is MAP controlled in the long-term?
Control of blood volume (E.g. GI, Kidneys) - mainly endocrine
27
Does SV increase or decrease if cardiac contractility is increased?
Increase
28
Where does the medulla first synapse and what happens after that?
Nucleus tractus solitarius
| Then relays information to other brain regions
29
Where is the vagal outflow for the heart relayed to in the CNS?
Nucleus ambigus in medulla
| And regulation of spinal sympathetic neurons
30
If the baroreceptor reflex (autonomic nervous system) if an extrinsic control of SV then what governs the intrinsic control?
Frank-starling mechanism.
| Direct relation between EDV and SV
31
How does blood flow in normal arteries? Any sound?
Smooth laminar fashion.
| Inaudible.
32
What sound is heard when BP cuff exceeds SBP?
No sound as flow is blocked
33
What sound is heard when BP cuff is kept between SBP and DBP? Why?
Korotkoff sound.
| Due to turbulent flow when BP intermittently exceeds cuff pressure.
34
What is the formula for MAP?
DBP + 1/3 (SBP-DBP)
35
How much longer is diastole compared to systole in a single cardiac cycle?
Twice longer
36
What is the normal pulse rate?
| What else should you note for when taking a pulse? (3)
60-100bpm.
| Rhythm, volume, character
37
What is the normal resp rate?
12-20/min
38
What is the normal capillary refill time?
<2s
39
How is consciousness recorded?
AVPU
| or GCS
40
What is the normal O2 sat?
>95%
41
At what temperature is the core body maintained at?
37.8
42
Increased body temp increases cell metabolism.
| But what can overheating result in? (4)
Protein denaturation, nerve malfunction, convulsion, death
43
What can low body temp result in?
Slow down cell reaction and metabolism
44
What site is good for measuring body temp in hypothermia? (<35)
What is the normal range?
Rectal (more representative of core temp)
| 36.7 - 37.5
45
Other than rectal, what other sites can be used to measure body temp?
Tympanic - 35.5 - 37.5
| Oral - affected by foods and drinks
46
Body temp shows slight diurnal variation.
| When is body temp lowest?
Early morning
47
When is body temp higher in menstrual cycle?
2nd half from time of ovulation
48
What contributes to heat generation in the internal environment (3)?
1. Brown fat
2. Muscle activity (E.g. Shivering)
3. Oxidation of metabolic fuel
49
What increases BMR?
Hormones such as adrenaline, noradrenaline, thyroxine
50
What contributes to heat generation from the external environment? (3)
```
Mostly radiation (50%).
Convection, conduction
```
51
What contributes to heat loss to the external environment? (4)
Radiation, convection, conduction, evaporation
52
Is water or air a better conductor of heat?
Water
53
What is forced air movement across body surface (E.g. by wind or fan)
Carries more heat away in a given period (Wind chill factor)
54
Convection works with which other process?
Conduction.
| E.g. Air warmed via conduction from skin before rising
55
What is passive evaporation?
Occurs continuously and not subjected to physiological control
56
What is active evaporation?
E.g. Sweating
| Controlled by sympathetic NS
57
What is one environmental factor that affects evaporation?
Humidity
58
What is evaporation?
Energy from body required to convert water on skin surface and lining of respiratory airways into vapour
59
What are the 3 component for the feedback response to regulate temperature?
Sensor: Central thermoreceptors found in hypothalamus, abdominal organs for core temp. Peripheral thermoreceptors found in skin
Control centre: Hypothalamus
Effectors: Skeletal muscle, skin arterioles, sweat glands (and indirectly lead to behavioural changes)
60
What does the posterior and anterior hypothalamic centre contribute in terms of temperature regulation?
Posterior - cold
| Anterior - warmth (A&W)
61
What are the outcomes of a cold response? (3)
Skin arteriole (SNS): Vasoconstriction restricts blood flow to skin surface to conserve heat
Skeletal muscle: Increased muscle tone, shivering, increased voluntary movement to produce heat/ warm the body
Behavioural changes: Postural change to reduce exposed surface area, warm clothes
62
What are the outcomes of a warm response? (4)
Skin arteriole (SNS): Vasodilate to promote blood to skin surface to lose heat
Skeletal muscle: Decrease muscle tone, decrease voluntary movement
Sweat glands: Sweat --> evaporation
Behavioural change: Cool clothing
63
What happens to temp control in infection/ inflammation?
What response is initiated?
Macrophage release endogenous pyrogens which stimulate prostaglandins release in the hypothalamus.
Body temp raised to a higher setpoint --> cold response initiated --> body starts to warm --> Fever (38-40 deg)
64
When is the setpoint restored back normal from a fever? (2)
What response is initiated?
1. Pyrogen release reduced/stopped (E.g. Antibiotics)
2. Prostaglandins synthesis reduced (E.g. NSAIDs)
Initiates hot response to cool body --> temp brought down to normal hypothalamic set point `
65
What can failure of heat regulating mechanism result in?
Hyperthermia (>40 deg)
66
What is hypothermia?
<35 deg
67
What component of the phospholipid bilayer have an influence on fluidity?
Cholesterol
68
What influences the thickness of the phospholipid bilayer?
R groups at the end of the fatty acid tail
69
How often do phospholipid flip to the other leaflet?
Rarely
70
What kind of molecules are able to cross the lipid bilayer freely?
Small, uncharged polar molecules
| Lipid soluble molecules
71
What appearance does the cell membrane give off in the electron micrograph?
Laminar appearance with less dense layer in the middle
72
What are the 3 types of membrane proteins?
Peripherally associated membrane proteins
Integral membrane proteins
Docking-marker acceptors
73
Are peripheral membrane proteins covalently bonded to integral proteins?
No
74
What do peripheral membrane proteins adhere tightly to?
Cytoplasmic or extracellular surface of plasma membrane
| Not embedded within membrane
75
How are integral membrane proteins intimately associated with the bilayer? (3)
1. Span lipid layer once or several times (a-helical) - transmembrane proteins
2. embedded but do not cross bilayer
3. linked to lipid component of membrane of fatty acid derivative in the membrane
76
What are the 5 functions of integral membrane proteins
1. Ligand-binding receptors
2. Adhesion molecules (E.g. Integrins, Cadherins)
3. Transmembrane movement of water soluble substance by acting as pores (passive), carriers (facilitated) or pumps (active)
4. Enzymes (E.g. membrane bound carbonic anhydrase)
5. Intracellular signalling role (E.g. Kinases and GTP-binding proteins at cytoplasmic surface)
77
Where are docking-marker acceptors located?
V-SNARE on Inner membrane surface of vesicle coat (coatamer)
78
What do docking-marker acceptors interact with?
V-SNARE interact with t-SNARE docking marker acceptor of targeted plasma membrane
79
How are appropriate cargo from the golgi lumen selected for export into vesicles?
Recognition markers in outer membrane of Golgi binds only to the sorting signals of protein molecules to be secreted
80
What is glycocalyx made of
Glycolipids and glycoproteins
81
What do membrane carbohydrates serve as?
Self-identify markers for growth, development and interaction
82
What kind of pump is usually found at the basolateral region of the epithelial cells?
Na+/K+ ATPase
83
What kind of transport do tight junctions promote and prevent?
Promotes transcellular and prevent/ reduce paracellular
84
Which part of the lateral edges of epithelial cells do tight junctions join at?
Near apical side
85
Do desmosomes allow materials to move around in the intercellular space?
Yes
86
What kind of tissues have desmosomes?
Those subjected to stretching
87
What is the polarity of the connexins/ channels of gap junctions?
Hydrophilic
| *Allows charged ions and small molecules to pass
88
What are the 2 factors involved in permeability of a particle to pass through a membrane?
1. Lipid solubility
| 2. Size
89
What are the 2 types of driving force for movement across a membrane?
Passive and active (ATP)
90
What kind of membrane transport involves molecules and ions that are passively driven across membrane down concentration/ electrical gradient?
*Give 2 examples
Unassisted membrane transport
Simple diffusion, Osmosis
91
When does simple diffusion stop?
When NET diffusion becomes zero - dynamic equilibrium
*NB there's still ongoing movement of substance but gradient = 0
92
What are the 3 directly proportional factors and 2 inversely proportional factors of Fick's law that affects RATE of NET diffusion across membrane?
Direct: Magnitude of gradient, surface area of membrane, lipid solubility of substance
Inverse: Molecular weight of substance, diffusion distance (bilayer thickness is fairly constant throughout)
93
Electrical gradient promotes movement of ios towards area of?
Opposite charge
*Like charges repel
94
What are the 2 types of ion-specific channel proteins?
Leak (always open)
| Ligand-gated
95
What consist of an electrochemical gradient?
Simultaneous electrical and chemical gradient acting on an ion
96
What channels do water pass through readily in the plasma membrane?
Aquaporins (passive)
97
Osmosis is the NET diffusion of WATER from an area of higher to lower what?
Solute concentration
98
What is osmolarity?
Concentration of osmotically active particles in solution
99
What is the effect of solution on cell volume known as?
Tonicity
100
What is assisted membrane transport for? (2)
1. Poorly lipid soluble molecules
| 2. Transport against concentration gradient
101
What are the 4 types of assisted membrane transport?
1. Carrier-mediated - depends on carrier specificity and saturation (movement of molecule/time) and substance competition to carrier
2. Facilitated - carrier transports down concentration gradient
3. Vesicular - requires energy to form vesicles; endocytosis and exocytosis
4. Active - Energy required to go against gradient; Primary and secondary. Another flashcard
102
Other than secreting enzymes and hormones, what else does exocytosis contribute to?
Adding carriers, channels or receptors to plasma membrane.
103
What is primary active transport?
Give an example of a pump
ATP hydrolysed by carrier protein, Pi binds to carrier and increases affinity for ion
Ion binds, conformation change, affinity reduced, ion and Pi released, shape reverts
Na+/K+ ATPase
104
What does transport 3 Na OUT and 2 K IN help in? (2)
1. Regulate cell volume (solute concentration)
| 2. Indirectly serves as energy source for secondary active transport
105
What is secondary active transport?
Uses second-hand energy (indirectly) stored in ion concentration gradient (Na+ will want to go back into cell), acting as driving force to couple with transport solute across plasma membrane
106
What are the 2 types of secondary active transport?
1. Symport - Solute and Na+ in same direction (E.g. GI absorption)
2. Antiport - opposite direction (E.g. Na+/H+ to regulate intracellular pH)
107
What is the 'separation of opposite charges across membrane to do work' known as?
Membrane potential
108
What does the magnitude of membrane potential depend on?
Depends on number of opposing charges separated (concentration gradient and permeability to the ions)
109
At resting membrane potential, is the membrane more permeable to K+ or Na+
K+, by 100x
110
Are large negatively charged intracellular proteins permeable?
No
111
What is the movement of K+ based on concentration and electrical gradient like?
K+ moves out down concentration gradient -> ECF becomes more positive and moves back into cell down electrical gradient due to negatively charged proteins
When both opposing gradients are at equilibrium, net movement = 0
**Same for Na+ but opposite (ECF becomes more negative due to Cl-)
112
Why is the resting membrane potential slightly more positive than EK+ (Equilibrium potential of K+) in nerve cell?
```
Resting = -70mV
EK+ = -90mV upon net diffusion outwards
```
More positive due to inward leak of Na+
113
What does Na+/K+ pump do to the membrane potential?
Hyperpolarises
114
Why does K+ preferentially move outwards in potassium selective channels?
Outward concentration gradient energy > inward electrical gradient energy
115
As an ion becomes more permeable, what does it drive the membrane potential towards?
It drives it closer to the ion's own equilibrium potential
116
What are the stimuli that regulate gated-ion channels? (3)
1. Voltage
2. Ligand/ chemical
3. Physical (Mechanical/ thermal)
117
What does action potential do to the polarity of the membrane?
Brief reversal
118
Generation of action potential follows which principle?
All or None
119
Activation of Na+ selective channel is?
| What is the outcome?
Self-reinforcing
| Opening of a few channels will open more (Positive feedback)
120
What happens to Na+ channels during maintained depolarisation?
What does it contribute to (2)?
Goes from open to non-conducting, inactive state which contributes to repolarisation and refractory period
121
What happens to Na+ channels during repolarisation?
Becomes closed (ready for depolarisation)
122
Activation of K+ selective channel is?
| What is the outcome?
Self-liming
| Repolarisation closes the channel (Negative feedback)
123
What are the 2 refractory periods? When do they each occur?
1. Absolute - during repolarisation (no stimulus can elicit 2nd AP; all Na+ channel inactivated)
2. Relative - during hyperpolarisation (stronger than normal stimulus can elicit 2nd AP - mix of inactivated and closed Na+ channels)
124
Action potential amplitude, magnitude and velocity. Do they fluctuate when propagated along the axon?
No, they stay constant
125
How to increase passive current spread which increases AP velocity (2)?
1. Increase axon diameter
| 2. Decrease current leak across axon via insulation (Myelin)
126
How do myelinated and unmyelinated axons conduct AP?
Myelinated - salutatory conduction (jump from node of ranvier to next) --> faster
Unmyelinated - passive current spread
127
Demyelinating disorders slow nerve conduction.
| Give 1 example from the CNS and PNS
CNS: Multiple sclerosis
PNS: Guillain Barre Syndrome
128
What kind of channels are clustered at the node of ranvier?
Voltage-activated Na+ channel
129
What microglial cells are responsible for myelin sheath production in the CNS and PNS?
PNS: Schwann cells - many surround a single axon thus multiple myelin layers
CNS: Oligodendrocytes - one cell surround many axons
