Physiology COPY Flashcards
(161 cards)
1
Q
What do membranes do?
A
Control exit and entry of waste products, they are selectively permeable.
-Maintain ion concentration gradients and participate in the joining of cells
2
Q
What is the plasma membrane?
A
-Phospholipid bilayer
-Cholesterol
-Proteins
-Carbohydrates
3
Q
What does cholesterol add to plasma membrane?
A
Fluidity and stability
-Stiffens the membrane
4
Q
3 types of proteins in plasma membrane?
A
Integral
Transmembrane
Peripheral
5
Q
Where are integral proteins in membrane?
A
Embedded in bilayer
-Receptors
6
Q
What are names of transmembrane proteins and where are they?
A
Transporters/channels
-Extend through membrane
7
Q
What is different about peripheral proteins compared to transmembrane and integral?
A
They do not penetrate the membrane
8
Q
What makes up the glycocalyx?
A
Glycoproteins
Glycolipids
9
Q
Functions of lipid bilayer?
A
Basic structure of membrane
Hydrophobic interior serves as a barrier
Responsible for fluidity
10
Q
Function of carrier/transport proteins?
A
Span the membrane and are substrate specific
11
Q
Where are docking marker acceptors?
A
Inner membrane surface
12
Q
How do docking membrane acceptors work?
A
Interact with secretory vesicles leading to exocytosis of vesicle contents
13
Q
How do receptor proteins work?
A
Bind specific molecules - lock & key
14
Q
Types of cell adhesion molecules (proteins)?
A
Cadherins
Integrins
15
Q
What do cadherins do? And what are they?
A
Hold cells within tissues together
Cell adhesion molecules
16
Q
What do integrins do?
A
Span membrane acting as a link between extra and intra-cellular environments
17
Q
2 Functions of carbohydrates?
A
-Serve as self identity markers enabling cells to identify and interact with one another (different cell types have different markers)
-Role in tissue growth
18
Q
3 types of specialized cell junctions?
A
Gap junctions
Tight Junctions
Desmosomes
19
Q
Desmosomes?
A
Adhering junctions that anchor cells together
20
Q
Tight junctions?
A
Join lateral edges of epithelial cells near luminal/apical membrane
21
Q
Gap junctions?
A
Communicating junctions that allow movement of charge carrying ions and small molecules between 2 adjacent cells
22
Q
What does Fick’s law of diffusion relate to?
A
-Magnitude of conc gradient
-SA of the membrane diffusion is taking place across
-Lipid solubility of substance
-Molecular weight of substance
-Distance which diffusion must take place across
Q ∝ 𝝙C · A · P
23
Q
What is an electrochemical gradient?
A
Where an electrical and a concentration (chemical) gradient may be acting on a particular ion at the same time
24
Q
Osmosis?
A
Net diffusion of water down a concentration gradient
25
what does osmosis levels depending of ?
the availability of Aquaporins (water channels) in the cell membrane
26
Osmolarity?
Concentration of osmotically active particles in a solution
27
What is osmolarity measured in?
Osmoles/Litre
28
Osmolarity of body fluids?
~300mOsm
29
Tonicity?
Effect a solution has on cell volume
30
Units of tonicity?
NO UNITS
31
What is carrier-mediated transport?
Substance binds to specific carrier and undergoes transformational change to transport substance
32
What is saturation another term for?
Transport maximum (Tm)
33
Fact file of facilitated diffusion?
-Energy?
-Mediated?
-Gradient direction
No energy required
-Carrier mediated
-From high to low conc
34
Active transport fact file?
Energy?
Gradient?
Types?
-Energy required
-Low concentration to high concentration
-Primary= energy directly required
Secondary= Energy required but not used directly
35
Secondary active transport energy?
-Energy required but not used directly
-It is stored in the form of an ion concentration gradient (usually Na+)
36
Mechanisms of secondary active transport?
2 mechanisms
-Symport- (contransport)= the transported solute and the ion move in the same direction across the membrane. For example, the glucose-sodium symporter
-Antiport (countertransport): In this mechanism, the transported solute and the ion move in opposite directions across the membrane. For example, the sodium-calcium exchanger
37
What is K+/Na+ATPase used in? Where is it?
Primary active transport
Plasma membrane of all cells
38
Ratio of NA:K movement in primary AT?
3 Na out
2 K in
39
3 important roles of Na+/K+ATPase?
-Establish Na/K concentration gradients across plasma membrane
- Regulate cell volume by controlling concentration of solutes inside the cell
-Energy used to drive the pump indirectly serves as energy source for secondary AT
40
Types of vesicular transport?
Endocytosis
Exocytosis
41
Endocytosis?
Membrane pinches off to engulf substance
42
Exocytosis?
Vesicle fuses with membrane, releasing contents to ECF
43
What is Em? Units?
Membrane potential - separation of opposite charges across membrane
-mV
44
Concentration gradient direction for K+?
Outward
45
Concentration gradient for Na+?
Inward
46
Electrical gradient for K+/Na+?
Both positively charged so the EG for both will be towards the negatively charged side of the membrane
47
Equilibrium potential for K+?
When concentration and electrical gradients balance eachother
48
Membrane potential at Ek?
-90mV
49
Membrane potential for Na+?
ENa+ +61mV
50
Nernst equation?
Eion=
61Log10 [ion]0/[ion]i
51
Resting membrane potential for a typical nerve cell?
-70mV
52
What is the Nernst equation used for?
To find cell potential under non-standard conditions
53
Why is Em of nerve cell close but not identical to Ek?
Slight inward leak of Na+ into the cell, K+ gradient is most important factor here
54
Goldman-Hodgkin-Katz equation
Em= 61Log10 Pk+[K+]o + PNa+ [Na+]o
___________________________________
Pk+[K+]i + PNa+ [Na+]i
55
What is the Goldman Hodgkin Katz equation used for?
Calculating overall membrane potential
56
What does P stand for in Goldman Hodgkin Katz equation?
Relative permeability
57
Hyperpolarization?
More negative
58
Depolarisation?
More positive
59
Which hormones control glucose in post absorptive and absorptive states?
Insulin
Glucagon (pancreas)
60
Which hormone controls glucose in emergencies?
Adrenalin (adrenal gland)
61
Which hormones control glucose during starvation?
Cortisol (Adrenal)
Growth hormone (pituitary)
62
Types of pancreatic islets of langerhan?
Alpha
Beta
Delta
63
What do alpha pancreatic islets of langerhan produce?
Glucagon
64
What do beta pancreatic islets of langerhans produce?
Insulin
65
What do delta pancreatic islets of langerhan produce?
Somatostatin
66
What are pancreatic islets of langerhan located in?
Endocrine glands
67
What happens to levels of
-Glucose
-Insulin
-Glucagon
in absorptive state?
-Glucose rises
-Insulin rises
-Glucagon falls
68
Which process does insulin favour?
Anabolism
69
What is converted to what by insulin?
Glucose -> Glycogen
Fatty acids-> Triglycerides
Amino acids -> protein
70
What is the hormone of the fed state?
Insulin
71
Effects of insulin?
-Lowers glucose by stimulating uptake from blood and activating liver enzymes
-Promoting secretion= increased glucose= increased parasympathetic activity
-Inhibiting secretion = decreased glucose = increased sympathetic activity
72
Which process does glucagon favour?
Catabolism
73
What is converted to what by glucagons presence?
Glycogen -> Glucose
Triglycerides-> Fatty acids
74
What is glucagon the hormone of?
The hungry state
75
Effects of glucagon?
Raises glucose by increasing glycogenesis, inhibiting liver glycogen synthesis, promoting liver gluconeogenisis, lipolysis
76
What happens in type 1 diabetes?
Little/no insulin release
-Defect in beta cells
Insulin injections required
-Early onset
77
Stimulation of release of glucagon?
Decreased blood glucose
Amino acids
Sympathetic nerve activity
78
Stimulation of inhibition of release of glucagon?
Raised blood glucose
Insulin
79
Type 2 diabetes?
Insulin secretion MAY be normal
-Defect in insulin sensitivity
-Diet/exercise/oral drugs
ADULT onset
80
Adrenaline raises glucose. True or false?
True
-Stimulates gluconeogenesis
-Stimulates glycogenolysis
81
When is adrenaline released?
During short term emergencies
82
What does cortisol do to glucose levels?
Raises them
83
What processes does cortisol stimulate?
-Protein catabolism
-Gluconeogenesis
-Lipolysis
-
84
Where is growth hormone secreted from?
Anterior lobe of pituitary
85
In response to ________, growth hormone does 3 things
1.
2.
3.?
Starvation
1.Decreases glucose uptake by muscle
2. Mobilises glucose form liver
3. Promotes lipolysis in fat cells
86
What happens to baroreceptor firing if high blood pressure is sustained?
Firing decreases
They only respond to acute changes
87
MAP equations when you have diastolic and systolic?
MAP = [(2x diastolic) + systolic]/3
MAP = DBP + 1/3 difference between SBP/DBP
88
MAP equations?
MAP = Cardiac output (CO) x Total peripheral Resistance (TPR)
89
CO equation?
CO = stroke volume (SV) x Heart rate (HR)
90
How can MAP be regulated?
By regulating
-HR
-SV
-TPR
91
Which hormones can increase metabolic heat?
Adrenaline, noradrenaline, thyroxine
92
What is basal metabolic rate?
Basic level of heat production
93
Ion channels responsible for action potentials in neurones?
Voltage activated Na channels = depolarizing
Voltage activated K channels = Hyperpolarizing
94
What are voltage activated Na/K channels activated by?
Membrane depolarization
-Na channels rapid, K channels slight delay allwing time for Na cahnnels to close
95
What is positive feedback (upstroke of graph)?
Activation of Na channels is self-reinforcing, the opening of a few channels causes further depolarization
96
How is the activation of K channels self-limiting?
The outward movement of K causes repolarisation which turns off the stimulus (negative feedback) downstroke of graph ad undershoot due to delayed closure of K channels
97
What does an absolute refractory period mean?
A
No stimulus, however strong, can elicit a second AP
98
Oligodendrocytes?
Produce myelinated cells in CNS (Shwann cells do it in PNS)
99
Which ion is most important in determining the resting membrane potential?
POTASSIUM
100
What is meant by autorhythmicity of the heart?
A
It is able to generate its own electrical impulses without external stimuli
101
Where does excitation of the heart normally originate?
A
SA node
102
What are the specialised cells within the SA node that initiate the heart beat called?
A
Pacemaker cells
103
What is meant by sinus rhythm?
A
Describes the heart's pace being controlled by the SA node
104
SA node cells have a stable resting membrane potential. True/False?
A
False
They exhibit spontaneous pacemaker potential
105
What is the function of the spontaneous pacemaker potential?
A
Takes the membrane potential to threshold (depolarisation) to generate an action potential
106
What gives rise to pacemaker potential?
A
Decrease in K+ efflux
Slow Na+ influx
107
What causes the rising phase of the action potential (depolarisation) in SA node cells?
A
Opening of Ca++ channels, resulting in Ca++ influx
108
What causes the falling phase of the action potential (repolarisation) in SA node cells?
A
Opening of K+ channels, resulting in K+ efflux
109
Summarise the phases of the SA node action potential
A
Pacemaker potential: decreased K+ efflux, slow Na+ influx
Rising phase: Ca++ influx
Falling phase: K+ efflux
110
Which junctions allow cell-to-cell spread of excitation?
A
Gap junctions
111
The AV node is the only point of electrical contact between atria and ventricles. True/False?
A
True
112
AV node cells are large and slow to conduct. True/False?
A
False
They are small and slow to conduct
113
Why is AV nodal delay present?
A
To allow time for atrial systole to precede ventricular systole
114
Which fibres enable the excitation to spread to the ventricles?
A
Bundle of His and Purkinje fibres
115
What gives rise to the rising phase of the action potential in ventricular contractile cells?
A
Fast Na+ influx
116
Describe Phase 0 of the cardiac action potential
A
Fast Na+ influx causes reversal of the resting membrane potential from -90mV to +30mV
117
Describe Phase 1 of the cardiac action potential
A
Closure of Na+ channels + transient K+ efflux causes some repolarisation
118
What gives rise to the plateau phase (phase 2) of the cardiac action potential?
A
Ca++ influx
119
What gives rise to the falling phase (phase 3) of the cardiac action potential?
A
K+ efflux
120
Describe Phase 3 of the cardiac action potential
A
Closure of Ca++ channels and opening of K+ channels allows K+ efflux which causes repolarisation of the membrane potential back to -90mV
121
Sympathetic stimulation causes increased heart rate. True/False?
A
True
122
What is meant by vagal tone?
A
Parasympathetic stimulation to the heart dominating in resting conditions
123
The vagus nerve supplies only the SA node. True/False?
A
False
Supplies both SA and AV nodes
124
What does parasympathetic stimulation do to the AV node?
A
Increases AV nodal delay
125
Which neurotransmitter acts on which receptor in parasympathetic control of the heart?
A
ACh on M2 receptors
126
Name a competitive inhibitor of ACh that is used in bradycardia
A
Atropine
127
Vagal stimulation causes the slope of the pacemaker potential to increase. True/False?
A
False
Slope decreases (increased AV node delay)
128
What is meant by negative chronotropic effect?
A
Decreased contraction of the heart due to less frequent action potentials
129
Which areas of the heart does the sympathetic system supply?
A
SA node
AV node
Myocardium
130
Which neurotransmitter acts on which receptor in sympathetic control of the heart?
A
Noradrenaline on B1 receptors
131
Sympathetic stimulation does what to the slope of the action potential?
A
Increases it (become sharper )
132
What is meant by positive chronotropic effect?
A
Increased contraction of the heart due to more frequent action potentials
133
Where does Lead I of an ECG connect?
A
Right arm - Left arm
134
Where does Lead II of an ECG connect?
A
Right arm - Left leg
135
Where does Lead III of an ECG connect?
A
Left arm - Left leg
136
Cardiac muscle is striated. True/False?
A
True
137
What creates the striated appearance of cardiac muscle?
A
Contractile protein elements (actin and myosin)
138
Give the name of protein channels that which form electrical communication between neighbouring myocytes
A
Gap junctions
139
What do desmosomes do in the heart?
A
Provide mechanical adhesion between adjacent cardiac cells
Ensure tension is developed
140
What is contained within muscle fibres?
A
Myofibrils (contractile protein elements of muscle)
141
Actin filaments are thick and appear light. True/False?
A
False
They appear light but are thin
142
Myosin filaments are thick and appear dark. True/False?
A
True
143
What is the arrangement of of actin and myosin within each myofibril called?
A
Sarcomere
144
Myosin filaments slide over actin filaments to produce muscle tension. True/False?
A
False
Actin slides over myosin!
145
What is required to generate the force by which sliding of filaments can occur?
A
ATP
Calcium
146
What is the role of calcium in sliding of filaments?
A
Required to 'switch on' cross-bridge formation
1. binds to troponin complex on actin
2. causes conform change which exposes actin binding site
3. cross-bridge forms via site and myosin binding site
147
What is the role of ATP in sliding of filaments?
A
Binds to myosin head to either energise it or break down the cross-bridge between myofibrils (that is created by calcium)
148
Where does the calcium that activates contractile machinery come from (where is it stored)?
A
Sarcoplasmic reticulum
149
What is meant by calcium-induced calcium release?
A
Ca++ influx during the plateau phase of the AP causes Ca++ to be released from the sarcoplasmic reticulum to cause contraction
150
What is meant by the refractory period?
A
Period following action potential where it is not possible to generate another action potential
151
What are the two moments where a new action potential cannot be generated?
A
Plateau phase (Na channels in closed state)
Falling phase (K channels open, thus membrane cannot depolarise)
152
What is the clinical benefit of the refractory period?
A
Prevents tetanic contractions of the heart
153
Define stroke volume
A
Volume of blood ejected by each ventricle per heart beat
EDV - ESV
154
What is meant by end diastolic volume (EDV)?
A
Volume of blood remaining in each ventricle following diastole
155
What determines EDV?
A
Venous return
156
Describe the Frank-Starling Law of the Heart
A
The greater the EDV (as a result of more venous return), the greater the stroke volume will be during systole
157
Optimal skeletal muscle fibre length (for contraction) is achieved by stretching the muscle. True/False?
A
False
Optimal length is at rest
158
What is meant by preload?
A
Volume of blood in each ventricle before contraction
159
What is meant by afterload?
A
The resistance against which the heart has to pump after contraction
160
What determines the resting membrane potential?
The resting membrane potential is determined by charged ions existing on each side of the membrane in unequal distribution. due to the membrane permeability to specific ions (e.g present of potassium leak channels )
161
What effect does dephosphorylation of the sodium potassium pump have on sodium transport outside of the cell?
The pump desphosphorylates, and changes shape to move the K+ ions inside the cell. The unphosphorylated pump has a higher affinity for Na+ ions than K+ ions, so the K+ ions are released.
therefore for every 2K+ enter the cell 3 Na+ move out the cell.
