Physiology Flashcards
(181 cards)
1
Q
What is the maintenance of steady state within our bodies by coordinated physiological mechanisms?
A
Homeostasis
2
Q
Where does a lot of physiological control occur?
A
Cell membrane
3
Q
What is central to the functionality of nerve and muscle cells?
A
Changes in membrane potential
4
Q
What must a control system be able to do to maintain homeostasis?
A
Sense deviations from normal, integrate this information, make appropriate adjustments
5
Q
What is intrinsic control?
A
Local controls within an organ
6
Q
What is extrinsic control?
A
Regulatory mechanisms from outside an organ, accomplished by the nervous and endocrine systems
7
Q
What is feedforward?
A
Responses made in anticipation of a change
8
Q
What is responses made after a change has been detected?
A
Feedback
9
Q
What is a deviation in a controlled variable detected by?
A
Sensors
10
Q
What does a sensor inform?
A
Appropriate control centre
11
Q
What do control centres instruct?
A
Effectors
12
Q
What is an example of positive feedback?
A
Contractions during labour
13
Q
Where are membranes found?
A
The outer boundary of every cell
14
Q
How permeable are membranes?
A
Selectively permeable
15
Q
What do membranes control entry and exit of?
A
Entry of nutrients and exit of waste/secretory products
16
Q
What are the amphipathic parts of lipids?
A
Hydrophilic head, hydrophobic tail
17
Q
What do lipids form in aqueous solution?
A
Fluid, lipid bilayer
18
Q
What is movement of membrane phospholipids dependent on?
A
Temperature
19
Q
What does cholesterol do in the membrane?
A
Aids stiffening and can flip easily
20
Q
What is the lipid membrane permeable/impermeable to?
A
Impermeable- charged molecules and water soluble substances
Permeable- small polar molecules
21
Q
Where are peripheral membrane proteins?
A
Not embedded within the membrane and adhere tightly to the cytoplasmic/extracellular surface
22
Q
What are transmembrane proteins?
A
Integral proteins which span the membrane
23
Q
What can integral proteins be linked to?
A
Membrane lipids or fatty acids
24
Q
What can integral proteins act as?
A
Ligand binding receptors, adhesion molecules, transporters, enzymes, intracellular signals
25
What do pores and channels allow?
Passive transport
26
What do carrier transporters do?
Facilitate or couple the transport of a molecule
27
What do transport pumps do?
Use energy from ATP to transport substances against a gradient
28
What are docking marker acceptors and where are they found?
Inner membrane surface, interact with secretory vesicles leading to exocytosis
29
What are short chain carbohydrates bound to membrane proteins or lipids known as?
Glycoproteins or glycolipids
30
What do glycoproteins/lipids form a layer called?
Glycocalyx
31
What do membrane carbohydrates have a role in?
Self identity markers and tissue growth
32
What are tight junctions?
Join the lateral edges of epithelial cells near the apical membranes
33
What are adhering junctions which anchor together cells, especially in tissues subject to stretching?
Desmosomes
34
What are gap junctions?
Communicating junctions which allow the movement of charge carrying ions and small molecules between 2 adjacent cells
35
What two properties determine whether a particle can pass through the membrane or not?
Lipid solubility and size
36
What is required for any transport through membranes?
A driving force- active or passive
37
What two mechanisms drive unassisted transport?
Diffusion down a concentration gradient or movement along an electrochemical gradient
38
Increasing what factors increases the rate of diffusion?
Concentration gradient, membrane surface area, lipid solubility
39
Decreasing what factors increases the rate of diffusion?
Molecular weight and distance
40
What type of channels are always open, or ligand gated?
Leak channels
41
What is it known as when electrical and chemical gradients act on an ion at the same time?
Electrochemical gradient
42
What is the electrochemical gradient involved in setting up?
Resting membrane potential
43
What is the relative speed of osmosis?
Slow
44
What is used to help water transport?
Aquaporin channels- passive
45
What makes different cells have different permeabilities to water?
Different numbers of aquaporins
46
What is osmolarity?
The concentration of osmotically active particles in a substance
47
What are two methods for carrying molecules against concentration gradients?
Carrier mediated transport or vesicular transport
48
What happens when a substance binds to a carrier transporter?
The carrier changes conformation
49
What 3 characteristics determine the kind and amount of material transferred through carrier mediated transport?
Specificity, saturation, competition
50
What are the two forms of carrier transport?
Facilitated diffusion or active transport
51
What is primary active transport?
Energy directly required
52
What is secondary active transport?
Energy not used directly, uses second hand energy stored in ion concentration gradients
53
What does Na+/K+ ATPase transport?
3Na+ out for every 2K+ in
54
What does the Na+/K+ ATPase pump have a role in?
Establishing Na+/K+ gradients, regulates cell volume, energy source for secondary active transport
55
What ion is usually coupled in secondary active transport?
Sodium
56
What is symport transport?
Secondary active transport where the solute and sodium move in the same direction
57
What is antiport transport?
Secondary active transport where the solute and sodium move in different directions (Na+ into)
58
Does vesicular transport require energy?
Yes
59
What are examples of vesicular transport?
Exo and endocytosis
60
What is a membrane potential?
Uneven distribution of charge across a membrane
61
What does membrane potential refer to?
Differences in charge between layers of ECF and ICF
62
What type of cells have the ability to produce rapid changes in membrane potential?
Excitable cells e.g. nerve and muscle
63
What is the resting membrane potential?
-70mV
64
What will the electrical gradient be towards for Na+ and K+?
Negative side
65
What is the resting membrane potential more permeable to, K+ or Na+?
K+
66
What is the concentration gradient for K+?
Outwards
67
What is the electrical gradient for K+?
Inwards
68
What is the equilibrium potential for K+?
-90mV
69
What does the +/- sign on a polarity represent?
The excess charge on the inside of the membrane
70
What is the concentration gradient for Na+?
Inwards
71
What happens when more Na+ moves into the cell following its chemical gradient?
Outside becomes more negative and is full of Cl- ions
72
After an influx of Na+, what is the electrical gradient for Na+?
Outwards
73
What is the equilibrium potential for Na+?
+60mV
74
What happens with increasing permeability of the membrane to an ion?
This ion drives the membrane potential towards its own equilibrium potential more strongly
75
Which of K+ and Na+ has a bigger effect on membrane potential?
K+
76
What helps maintain K+ and Na+ gradient across the membrane?
Na/K ATPase
77
What type of current does Na/K ATPase create?
Hyperpolarising
78
What are examples of what membrane potential changes can cause?
Contraction of muscle or secretion of insulin
79
What is depolarisation?
Membrane potential becomes less negative
80
What is hyperpolarisation?
Membrane potential becomes more negative
81
What are ion channels?
Transmembrane proteins which allow rapid flow of selected ions
82
What are the three types of gated ion channels?
Membrane voltage (voltage gated), chemical substances (ligand gated), physical stimuli
83
What ion channels are responsible for the depolarisation (upstroke) of APs?
Voltage gated Na+
84
What ion channels are responsible for the hyperpolarisation (downstroke) of APs?
Voltage gated K+
85
When do Na+ ion channels become activated during and AP and what does this cause?
Threshold potential- rapid depolarisation
86
What do neuron APs allow signalling over?
Long distances
87
Does the size of the stimulus have an effect on the size of the AP?
No- it happens or it doesn't
88
What activates both Na+ and K+ channels?
Membrane depolarisation
89
Which ion channel responds to membrane depolarisation quicker?
Na+
90
The activation of which ion channel is self reinforcing and what does this mean?
Na+: the opening of a few channels causes more to open which causes more depolarisation (positive feedback)
91
The activation of which ion channel is self limiting and what does this mean?
K+: outward movement of K+ causes repolarisation which then turns off the stimulus for opening (negative feedback)
92
What is the refractory period?
During maintained depolarisation, Na+ channels enter a non-conducting, inactivated state
93
What is required after the refractory period?
Repolarisation for the channels to enter the closed state
94
On an AP graph, the area from the start of hyperpolarisation to the lowest point on the graph is known as what?
Absolute refractory period
95
What does the absolute refractory period mean?
No stimulus, however large can elicit a second AP
96
What is the state of the Na+ channels in the absolute refractory period?
All inactivated
97
On an AP graph, what is the area from the end of the absolute refractory period to the area where the next AP begins known as?
Relative refractory period
98
What does the relative refractory period mean?
A stronger than normal stimuli may elicit a second AP
99
What is the state of Na+ channels in the refractory period?
Mixed inactivated and closed channels as the membrane is hyperpolarised
100
What is the maximum number of APs in a second?
1000
101
Why do passive signals in nerve cells not spread far?
Current loss
102
What is the potential change of an axon relative to?
The given current
103
What does membrane potential decrease exponentially with?
Distance
104
What does the distance over which the current spreads depend on?
Membrane and axial resistance
105
What is the effect of diameter of the axon on current flow resistance?
Bigger the diameter, lower the resistance
106
What does greater current spread increase?
AP conduction velocity
107
Is conduction faster in myelinated or non-myelinated axons?
Myelinated
108
What are Nodes of Ranvier?
Points between myelin sheaths of axons
109
What id Saltatory conduction?
APs jumping between Nodes of Ranvier
110
What are examples of demyelinating conditions?
MS and Guillian-Barre syndrome
111
What do demyelinating conditions cause?
Slowing or cessation of nerve conduction
112
What is fuel metabolism regulated by?
Hormones- glucagon, insulin, growth hormone, adrenaline and cortisol
113
What does thyroid hormone regulate?
Metabolic rate
114
What can be used instead of glucose in prolonged starvation?
Ketones
115
What does hypoglycaemia lead to?
Confusion and coma
116
What does hyperglycaemia lead to?
Damaged blood vessels
117
What are the two types of glands which the pancreas contains?
Exocrine and endocrine (islets of Langerhans)
118
What do exocrine pancreatic cells produce?
Secrete digestive enzymes and HCO3- to intestinal lumen
119
What do alpha cells in the islets of Langerhans produce?
Glucagon
120
What do beta cells in the islets of Langerhans produce?
Insulin
121
What do delta cells in the islets of Langerhans produce?
Somatostatin
122
What do F cells in the islets of Langerhans produce?
Pancreatic polypeptide
123
What does insulin stimulate?
Anabolism: glucose to glycogen, amino acids to proteins and fatty acids to triglycerides
124
What is insulin the hormone of?
The fed state
125
What does glucagon stimulate?
Catabolism: glucagon to glucose, triglycerides to fatty acids
126
What is glucagon the hormone of?
Hunger state
127
What does glucagon have no effect on?
Protein metabolism
128
What are the most abundant cells in the islets of Langerhans and whereabouts are they found?
Beta cells in the centre
129
Which cells are found around the outsides of islets of Langerhans?
Alpha and delta
130
What are all the different types of cells of the islets of Langerhans linked by?
Gap and tight junctions
131
What happens to insulin when glucose in the blood is high?
More is secreted into the blood
132
During fasting, less insulin is secreted and lipids and amino acids are mobilised. What do these lipids and amino acids do?
Provide fuel for oxidation and act as precursors for hepatic ketogenesis and gluconeogenesis
133
What effect does sympathetic/parasympathetic stimulation have on insulin secretion?
Sympathetic- inhibits, parasympathetic- stimulates
134
What effect does exercise have on insulin secretion?
Suppresses it
135
What 3 incretins (peptides) increase insulin secretion?
CCK, GLP-1 and GIP
136
Where are incretins released and what do they do?
GI tract cells- feedforward mechanism to prime Beta cells for insulin secretion
137
What are the three prime targets for insulin?
Liver, skeletal muscle and adipose tissue
138
Where else can insulin affect but isn't a prime target?
Cardiac muscle
139
Where are insulin insensitive cells?
Brain, kidneys and RBCs
140
What is the glucose storage molecule in liver and skeletal muscle?
Glycogen
141
What is the glucose storage molecule in adipose tissue?
Triglycerides
142
How does insulin lower plasma glucose in the liver?
Activating enzymes which convert glucose to glycogen
143
How does insulin lower plasma glucose in skeletal muscle?
Stimulating uptake of glucose from blood into muscle via GLUT4
144
Where is the defect in type 1 and 2 diabetes?
Type 1- beta cell function
| Type 2- insulin receptor sensitivity
145
Which type of diabetes is more prone to ketogenesis?
1
146
How is diabetes diagnosed?
Glucose after a meal higher then 11mmol/l
147
What are some effects of severe diabetes?
Increased plasma glucose after a meal, glucose in urine, formation of ketone bodies, decreased pH and hyperventilation
148
What is glucagon secreted in response to?
Ingested proteins
149
What is the principle target of glucagon?
Liver
150
Where are adrenaline and cortisol released?
Adrenal gland in response to stress
151
What do adrenaline and cortisol do to plasma glucose?
Increase it
152
What do adrenaline and cortisol do to gluconeogenesis?
Stimulate it
153
What does adrenaline stimulate which cortisol doesn't?
Glycogenolysis
154
What does cortisol stimulate which adrenaline doesn't?
Protein catabolism and lipolysis
155
When are adrenaline and cortisol released?
Adrenaline- short term emergencies
| Cortisol- long term
156
Where is growth hormone secreted?
Anterior lobe of pituitary gland
157
What does growth hormone cause in response to starvation?
Decreased glucose uptake by muscles, ,obilises glucose from liver, promotes lipolysis in fat cells
158
What is core optimum body temperature?
Around 37.8 degrees C
159
How can body heat be gained?
Metabolic heat (internal), radiation, convection, conduction (external)
160
How can body heat be lost?
Radiation, convection, conduction, evaporation
161
What hormones increase heat production through metabolic heat?
Adrenaline, noradrenaline, thyroxine
162
What external action does increased metabolic heat cause?
Muscle activity and hence shivering
163
What is conduction?
Transfer of heat from objects in contact- heat moves from warmer to cooler
164
What is convection?
Transfer of heat by air or water currents which carry heat away from the body
165
What is an active evaporative heat loss process?
Sweating
166
What controls sweating?
Sympathetic nervous system
167
What is body temperature controlled by?
A negative feedback system
168
Where are central thermoreceptors?
Hypothalamus and abdominal organs
169
Where are peripheral thermoreceptors?
Skin
170
Where are the effectors for maintaining body temperature?
Skeletal muscle, skin arterioles, sweat glands, behavioural adaptations
171
Where is the temperature control centre?
Hypothalamus
172
What part of the hypothalamus is activated by cold?
Posterior
173
What part of the hypothalamus is activated by warmth?
Anterior
174
What adaptations does cold result in?
Vasoconstriction and increased skeletal muscle tone (shivering)
175
What adaptations does warmth result in?
Vasodilation, evaporation of sweat and decreased skeletal muscle tone
176
What happens to the temperature setpoint in fever?
Increases
177
Where are chemicals released from in response to infection/inflammation?
Macrophages
178
What do macrophages stimulate release of which act on the hypothalamus to change the set point?
Prostaglandins
179
What response does the hypothalamus have to an increased temperature setpoint?
Elicits the cold response to increase temperature
180
What classes as hyperthermia?
>40 degrees
181
What classes as hypothermia?
< 35 degrees
