1
Q
Why is a comparative approach to physiology can be advantageous?
A
A comparative approach to physiology is advantageous because it takes an integrative look at organisms, how mechanisms work, and what that means for processes.
2
Q
Describe how homeostasis is achieved through negative feedback.
A
Control systems regulate a variable by opposing its deviation from a set-point thereby keeping the variable within its homeostatic range.
3
Q
Acclimation
A
Process of change in response to a controlled environmental variable in the lab.
4
Q
Acclimatization
A
Process of change in response to a natural environmental variation.
5
Q
Adaption
A
Process of change through natural selection leading to an organism whose physiology, anatomy, and behavior are matched to the demands of its environment.
- Takes place over many generations, results from changes in the DNA, and is usually irreversible
6
Q
August Krough Principle
A
There is an optimally-suited animal to study most biological problems.
7
Q
Set-point
A
Ideal physiological value or range that homeostatic mechanisms aim to maintain.
8
Q
Regulators
A
Animal maintains conditions to a certain extent.
9
Q
Conformity
A
Matches external environment.
10
Q
What is animal physiology and how can it be used?
A
Animal Physiology - The study of how animals function at all levels of organization
Can be used to understand
- Understand physiological diversity
- Understand diseases
- Predict impacts of environmental change
- Plan for conservation management
11
Q
Homeostasis
A
The tendency for animals to maintain relative (not static) internal stability in the face of external fluctuations.
- maintained by regulatory systems
12
Q
T or F: Homeostasis is constancy
A
False - Homeostasis is not constancy.
13
Q
Conformers
A
Matches external environment.
14
Q
Regulators
A
Animal maintains conditions to a certain extent.
15
Q
Advantages of being a conformer (1)
A
It is not energetically expensive
16
Q
Disadvantage of conforming
A
Not being able to survive a broad ranging conditions.
17
Q
Advantages of being a regulator
A
Able to survive broader conditions/ more variable conditions.
18
Q
Disadvantage of being a regulator
A
Energetically expensive
19
Q
Physiological Regulation - Negative Feedback
A
Control systems regulate a variable by opposing its deviation from a set-point thereby keeping the variable within its homeostatic range.
20
Q
Physiological Regulation - Positive Feedback
A
Controls systems regulate non-homeostatic change and create rapid change away from set-point. This promotes a large, unidirectional response.
- Much less common than negative feedback.
21
Q
Hydrophobic
A
Molecules that do not mix with water.
22
Q
Amphipathic
A
Having both hydrophilic and hydrophobic parts (phospholipids)
23
Q
Homeoviscous
A
An adaption in organisms to maintain a stable cell membrane fluidity by adjusting their lipid composition in response to changes in temperature.
24
Q
What is phenotypic plasticity?
A
Changes occur within the lifetime of an individual. No changes to DNA sequence.
25
Which two aspects of physiological regulation are examples of phenotypic plasticity?
1. Acclimation
2. Acclimatization
26
What is evolution
Changes occur over generations. Change to DNA sequence.
27
Which aspect of physiological regulation is an example of Evolution
Adaption
28
What separates the intracellular from the extracellular fluid
Lipid bilayer membrane
29
What kind of proteins does the cell membrane contain?
Peripheral and integral membrane proteins.
30
Why are membranes called a fluid mosaic?
Everything in the membrane can move around.
- the membrane is heterogenous
31
The composition of cell surfaces is related to their...
permeability
32
Permeability of ___ cells is greater than the ____ because...
1. Epithelial cells
2. integument
The low permeability of most integuments depends on a thin layer of keratins, lipids, or wax
33
Transcellular paths across epithelium
- Have molecules through the cell.
- Must cross both apical and basolateral cell membranes
34
Paracellular Paths across epithelium
- Moving between two cellular paths
- Materials following this path must be able to move through the band of tight junctions; only very small molecules are able to do this.
35
T or F: the inner and outer layers of the membrane are distinct?
True
36
Lipid Raft
Regions that accumulate cholesterol and glycolipids
- these regions are more rigid and preferentially recruit specific proteins that are involved in signalling pathways
- Lipid rafts readily move in the plasma membrane
37
How does temperature affect membrane fluidity?
- Cold temperatures make the phospholipid molecules more rigid (gel state)
- Warm temperatures make the phospholipid bilayer more fluid (liquid crystalline state)
38
Phospholipids are ___ molecules
amphipathic
39
Four changes that can occur to alter membrane fluidity
1. Fatty Acid chain length
2. Saturation
3. Poplar head group
4. Cholesterol
40
How does fatty acid chain length alter membrane fluidity?
Shorter tails mean less surface area for neighbouring fatty acids to interact/ bond with which would make the membrane more fluid.
41
How does saturation alter membrane fluidity?
Existence of double bonds = unsaturated = more kinks and tails = cant pack as tightly and creates more space = more fluidity due to fewer Vanderwhals forces
42
How does polar head groups alter membrane fluidity?
PC has more cylindrical heads = pack tightly
PE has cone heads = harder to pack = more fluid
43
How does Cholesterol alter membrane fluidity?
Interaction of cholesterol with fatty acid tails cholesterol disrupts interaction between fatty acid tails increasing membrane fluidity.
44
How does the interaction of cholesterol with polar heads affect permeability?
Cholesterol fills gaps between polar heads, decreasing membrane permeability to small molecules.
45
Coldwater fishes have more ____ fatty acids
Unsaturated
46
Simple Diffusion
Molecules move constantly and randomly
- Over time, more molecules move at random from an area of high concentration to an area of low concentration. This process is passive (no energy needed)
47
Fick's Law of Diffusion
The net rate of diffusion of a solute across a membrane is described by the Fick Diffusion Equation.
- The higher the difference in concentration the faster the movement
48
Electrochemical Gradients determine
The movement of solutes across permeable membranes
49
Ionic charge seperation occurs only within...
Nanometers of membranes
50
When the electrical and chemical gradients are in the same direction diffusion is...
Fast
51
When chemical and electrical gradients are in opposite directions diffusion is...
slow
52
at equilibrium there is a slight imbalance in ___ ions depending on the strength of diffusion
Sodium
53
Which gradient can be stronger chemical or electrical
Electrical
54
Osmosis
Osmosis is the diffusion of water through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.
- Osmosis depends on the number of dissolved entities in the solution, not on what those entities are.
55
Osmotic Pressure
property of a solution that allows you to predict which way water will move.
56
Osmolarity
Total dissolved entities per liter
- In biological systems, osmolarity is the unit of measure for osmotic pressure
57
Tonicity
The effect of a solution on cell volume.
- Effect of tonicity depends on differences in osmolarity but also on the permeability of the membrane to the solutes.
58
Osmosis vs. Tonicity
Osmolarity considers the total concentration of penetrating and non-penetrating solutes
vs
Tonicity relates only to the total concentration of non-penetrating solutes - depends on what can move across membrane - differs from different cells types
59
Hypertonic
Increased salt means water leaving cells
60
Hypotonic
Too much water entering the red blood cells because of osmotic pressure exceeds cell strength can cause red blood cells to burst.
61
Donnan Equilibrium
- Electroneutrality + permeant ion equilibrium + osmolarity
- The Donnan Equilibrium predicts that the distribution of ions across a membrane will be unequal if the membrane is impermeable to one or more types of charged particles
- Explains why in nature we see different concentrations across membranes
- Animal cells tend toward Donnan Equilibrium because they contain high concentration of non-permeating anionic molecules (A-).
- Donnan Equilibrium refers to a closed system - no ions are added or removed in this example
62
What three rules dictate the distribution of ions across a membrane
1. Principal of electroneutrality - Positive charges must equal total number of negative ions (net zero charge)
2. The product of the concentration of permeant (diffusible) ions inside the cell equals the product of the concentration of permeant ions outside the cell.
3. Osmolarity inside and outside must balance.
63
Passive Membrane Transport
- No energy required
- Solutes move down concentration gradient
Ex. simple diffusion
64
Active Membrane Transport
- Uses ATP
- Solute moves up concentration gradient
65
Uniporter
A channel that can only alow one type of molecule to go through one at a time
66
Antiporter
Swaps specific ions from one side to another. Needs to move everything at once
67
Symporter = co-tran'//sporter
Need to move everything all at once. Electroneutral.
68
Simple diffusion follows a ___ relationship
Linear
- Ficks equation
69
Facilitated transport follows a ___ relationship
Hyperbolic
- Michaelis-Menton Kinetics
70
What hormone regulates water permeability
AVP
71
3 Classes of Ion Channels
1. Voltage gated channels
2. Ligand-gated channels
3. Mechanically-gated channels
72
Voltage Gated Channels
Opens/closes in response to changes in membrane potential.
73
Ligand-Gated Channels
Open/close in response to presence/ absence of ligand
74
Mechanically-Gated Channels
Open/close in response to changes in cell shape
75
Polymoral
Known to open by multiple means? Such as trap channels like hot and cold
76
Primary Active Transport
Energy released by ATP hydrolysis drives solute X movement against an electrochemical gradient.
- The most common primary active transporter is the NA+ - K+ pump
77
Secondary Active Transport
Movement of ion X down its electrochemical gradient provides the energy to drive co-transport of second solute (S) against its electrochemical gradient
78
What is the NA+ - K+ pump is responsible for?
Maintaining high [K+]in and [Na+]out
Maintaining the transmembrane electrical potential - Not electrochemically neutral.
79
What did Cajal discover?
He identified neurons are discrete units using Golgi’s method.
80
What is a neuron?
Neuron - The anatomical and functional unit of the nervous system
- Neurons are contiguous (not continuous)
- The morphology of neurons varies within and across species - neural structure varies depending on function and location in the body
81
What two categories are the nervous system organized into?
1. Central Nervous System
2. Peripheral Nervous System
82
The peripheral nervous system is divided into what two fundamental groups?
1. Sensory Pathway
2. Motor Pathway
83
Autonomic Nervous System
Involuntary
- Sympathetic and parasympathetic work in opposition of each other
84
Sympathetic - Autonomic Nervous System
Usually stimulates, accelerates, or increases
- fight or flight
Stress -> Adrenaline
85
Parasympathetic - Autonomic Nervous System
Usually inhibits, slows, or decreases
- rest and digest
relax -> acetylcholine
86
Somatic Nervous System
Voluntary
87
What are the 4 types of glial cells?
1. Astrocyte
2. Microglia
3. Ogliodendrocyte
4. Schwann cell
88
Astrocyte
- CNS
- Transport nutrients, remove debris, regulate synaptic neurotransmitter
levels
- Interface between neurons and blood supply
- Regulate extracellular ion content
- Regulate neurotransmitter concentration
89
Microglia
- CNS
- Remove debris and dead cells, immune responses
- Response to disease
90
Oligodendrocyte
- CNS
- Form myelin sheath - wrap around neuron and change the permeability of the neural membrane and help speed things up
91
Schwann Cell
- PNS
- Form myelin sheath (motor and sensory neurons)
92
What are the four functional zones of Neurons
1. Signal Reception (input)
2. Signal Integration
3. Signal Conduction
4. Signal Transmission (output)
93
Signal Reception (input)
Dendrites- chemical signal comes in and gets turned into an electrical signal.
94
Signal integration
Axon hillock
95
Signal Conduction
Axon - allow fast transmission
96
Signal Transmission (output)
Axon terminals - where the signal ends up and electrical signal turns back into a chemical signal
97
True or False: Signals can only move in one direction on a neuron.
True
98
Synapse
Is the connection between an axon terminal and a target cell.
- Target cells can be other neurons, muscle cells, secretory cells
- Found at dendrites/soma (receive signals)
- Found at end of axon (send signals)
99
Neural signals are unidirectional from ___ -> ___
Soma -> Synapse
100
Afferent Neuron
Carries a signal away from a stimulus (sensory neuron)
- Simulus -> CNS
- A = away
101
Efferent Neurons
Carries a signal to cause a response.
- CNS -> effector
102
T or F: Neurons have a resting membrane potential meaning the inside of the cell has a different charge than the outside
True
103
Neurons are ___, meaning they can rapidly change their membrane potential. Changes in membrane potential act as ___
Excitable, electrical signals
104
Depolarization
Happens when the inside of a cell becomes less negative
Moving up towards zero
- Can use ATP to remove charges
105
Re-polarization
Na-K ATPpase
106
Hyper-polarization
Membrane potential becomes more negative
- If you open a potassium channel
107
The distribution of an ion across an ion-selective membrane depends on two opposing forces...
1. The chemical potential
2. The electrical potential
108
Equilibrium Potential
Is the voltage difference across the membrane when the two forces acting on that ion are equal
- EK = the equilibrium potential of K+
109
The Nernst Equation
Calculates the equilibrium potential for single ions
110
The Goldman Equation
- The Goldman Equation calculates the final membrane potential (Vm) from all the contributing ions
- Vm is proportional to the ratio of the ionic concentrations across the membrane and the permeability of the membrane to the ions
111
Neural Circuits
- Neurons are organized into functional circuits that rapidly conduct information to target
- A stimulus is converted into chemical and electrical signals that are carried rapidly through a relay of neurons called a neural circuit.
112
T or F: Neural circuits are in all multicellular life
True
113
Information through neuronal circuits alternate between... (2)
1. Graded and all or none signals
2. Electrical and chemical signals
114
Graded vs. all-or-none
Graded: Magnitude of response proportional to stimulus strength
All-or-none: Response is invariant, respective of stimulus strength
115
Electrical vs Chemical
Electrical: ions
Chemical: Neurotransmitters
116
Ligand gated ion channels convert chemical signals into...
Electrical signals by changing the membrane potential.
117
Graded Potentials
- In the dendrites and soma the electrical signals generated by ligand-gated ion channels are called graded potentials
- Ligand binds to channel -> ions can now move across the membrane
- As long as the chemical signal is bound the channel will stay open
118
T or F: Neurotransmitters cannot be released and used again
False
- they can be
119
Graded potentials are proportional to...
Stimulus strength
120
Why are neural circuits so complicated? Why not just one afferent/ one efferent neuron?
- Functional redundancy
- Many different stimuli - different stimuli require different responses
- Every step of the chain every time a signal is being converted is an opportunity for modulation, opportunity to fine tune whats going on and what the response to stimuli is.
121
Graded potentials can depolarize the cell via...
Na+ and Ca2+
122
Graded potentials can Hyper-polarize the cell via...
K+ and Cl-
123
Signals decay due to
Membrane permeability - leakage of ions across the membrane
Cytoplasmic resistance - Inherent resistance to current flow - cytoplasm is resistant to the flow of current
124
Signal magnitude ___ as it moves away from the source
Decreases
- exponential decrease
125
What causes an action potential?
The axon hillock need to depolarize the membrane beyond the threshold potential for the axon to fire an action potential.
126
Sub-threshold
- Graded potentials do not intake an action potential
- Starts dendrite but does not reach the threshold
127
Supra-threshold
Graded potentials causes the axon to fire an action potential.
128
Spatial Summation
Graded potentials from different locations can interact to influence the net change in membrane potential at the axon hillock.
129
Exhibitory
Signals depolarize the membrane.
130
Inhibitory
Signals Hyper-polarize the membrane.
131
Temporal Summation
Graded potentials occurring at slightly different times can interact to influence the net graded potential.
132
True or False: All supra-threshold stimuli produce an identical action potential.
True
- Magnitude of response is proportional to magnitude of the stimulus
133
How does a neuron transmit information?
1. Receptors on dendrites open, positive ions enter (depolarization)
2. positive charge moves electrotonically to the cell body
3. If positive charge is above threshold membrane potential (-50 mV), an action potential is generated
4. Na+ movies in and an action potential is propagated down the axon (all-or-nothing, not graded)
5. Action potential ends at terminal branches
6. An action potential is an all or nothing response that depends on the axon hillock reaching the voltage threshold
134
Conductance (g)
Movement of change per unit space
135
Why is it useful for an action potential to end with neurons in a hyper-polarized state?
Makes it more likely that it will be out of the channel
If it stayed at threshold potential that means it would only take the tiniest gradient potential before the neuron fired
Disease state - neurons don't enter the hyperpolarized state - epilepsy - causes abnormal firing
136
Properties of an Action Potential (3)
1. After an AP is triggered, neurons enter a refractory period
2. During the absolute refractory period, no AP can be triggered because the voltage-gated Na+ channels are in an inactivated state.
3. It is harder to generate a new AP during the relative refractory period because the membrane is hyperpolarized
137
Patch-Clamp Recording
- Can isolate and ion channel and measure current
- Solution mimics the extracellular fluid
- Adheres to the membrane
138
T or F: Potassium channels have a lag time
True
139
Voltage Gated Sodium Channels
- The voltage gated sodium channel has two gates: a voltage dependent activation gate and a voltage dependent time delayed inactivation gate
- The voltage gated Na+ channel can exist in three conformations
140
The voltage gated K+ channel
Has only one voltage dependent time delayed gate that can be either open or closed.
141
Signal conduction can occur by... (4)
1. Passive spread (electrotonic)
2. Action potential
3. Saltatory conduction
4. Chemical and electrical synapses
142
Axonal Conduction
- Is a combination of electronic current flow and APs
- Electrotonic current flow is much faster than APs
143
Electrotonic current flow is ___ and can only travel ___ distances
graded, short
144
What are the factors affecting conduction speed?
1. The length constant (λ)
2. The time constant (τ)
145
The length constant (λ)
- The decay of Vm with distance is described by the length constant: λ
- Electrotonic conduction is enhanced by high membrane resistance and low longitudinal (exoplasmic) resistance
146
The time constant (τ)
- Membrane voltage changes are reduced by high capacitance and resistance
- Following an applied voltage the time needed to reach an given change in membrane potential (Vm) is described by time constant
- How quickly a stimulus can cause a change in the membrane
- Τ = Rm x Cm (Rm = membrane resistance, Cm membrane capacitance - ability of membrane to store charge)
147
Factors Effecting the speed of propagation (2)
1. Axon Myelination
2. Axon diameter
148
Axon Myelination
- The axon of some neurons are wrapped with myelin - fatty membranes of glial cells: oligodendrocytes or Schwann cells
- Myelination increases the speed of propagation
- Segmented myelination leads to fast saltatory conduction of APs
- Increases Rm and thus λ (length constant)
Myelination also decreases C, maintaining τ
149
Axon Diameter
Increasing axonal diameter reduces longitudinal resistance (Ri), thereby increasing the length constant (λ) and conduction velocity.
150
The signal transmission zone includes three components...
1. Pre-synaptic cell - carries the signal to the synapse
2. Synaptic cleft - the space in between the pre- and post-synaptic cells
3. Postsynaptic cell - neurons, muscles, and endocrine glands
151
A neuron muscular junction
The synapse between a motor neuron and a muscle cell.
152
Electrical Synapses
Transfer information between cells by direct ionic coupling via gap junctions
153
What is the principal advantage and disadvantage of an electrical synapse?
Advantage of being fast but disadvantage of not spreading as far.
154
Electrical Synapse
- Rare in complex animals
- Comparatively fast
- Bi-directional
- Postsynaptic signal is similar to presynaptic
- Excitatory
155
Chemical Synapse
- Common in complex animals
- Comparatively Slow
- Uni-directional - controlled direction
- Postsynaptic signal can be different
- Excitatory or Inhibitory
156
How does the anatomy of an electrical and chemical synapse differ?
Chemical
- Transmission is indirect (there are no connections), instead there are receptors on postsynaptic, vesicles for transmitters on presynaptic
- Calcium channel
- Spacing is larger
Electrical
- Spacing is closer together
157
Fast vs Slow Chemical Synaptic Transmission
Differentiated by their post synaptic mechanisms - NOT by their neurotransmitters
158
Fast Chemical Synapses
Act through ionotropic receptors (ex. Ligand gated channels) found on the post-synaptic membrane
159
Slow Chemical Synapses
Act through metabolic receptors found on the post-synaptic membrane
160
Effector
Could be an ion channel can change things over a longer term function of synapse
161
The neuromuscular junction: structural specializations
- APs are conducted to skeletal muscles via large myelinated motor neurons
- The neuromuscular junction includes pre- and post-synaptic specializations
162
EPSPs move Vm ___ threshold potential
toward
163
IPSPs move Vm ___ from threshold potential
away
163
EPSPs and IPSPs ___
summate
164
Plasticity
Change in response to experience.
165
Neuronal Plasticity
Ability to change
synaptic strength over time via both synaptic
connections and functional properties of
neurons.
166
The synaptic transfer of information depends on its...
History
167
Whether a neurotransmitter is excitatory or inhibitory depends on the properties of its ___
Receptors
168
Evidence for learning ->
Modification of behaviour through experience.
169
A simple reflex behaviour
Stimulation of the mantle or siphon leads to gill withdrawl
170
Short-term Habituation
Occurs from a reduction in neurotransmitter release by the sensory neuron
171
Short-term sensitization
Occurs from an increase in neurotransmitter release due to presynaptic facilitation
172
Long-term sensitization
Can occur if kinase activity elicits changes in sensory neuron protein synthesis
ZOO*3600 - CAP I
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