Physiology Unit 1

Front 1

What is the value of adding "slack" to the range of values for the physiological variables regulated in homeostasis?

Back 1

-Less energy expenditure
-Decreased need for precision of receptors/effector mechanisms
-Greater flexibility about changing conditions without need to reset the set point

Front 2

What percentage of total body water is made up of plasma?

Back 2

7%

Front 3

What percent of body water is considered interstitial fluid?

Back 3

26%

Front 4

What percentage of water is considered intracellular fluid?

Back 4

67%

Front 5

Is more fluid intra- or extracellular?

Back 5

About twice as much body water is in intracellular fluid than extracellular (33% intracellular as opposed to 67% extracellular)

Front 6

Define: Set point

Back 6

The mean steady-state value maintained by a homeostatic system (about which there exists a range of values).

Front 7

Define: Feedback control system

Back 7

A system in which the regulatory signal depends upon the read "output" value.

Front 8

Define: Negative feedback system

Back 8

A feedback system whose regulatory signal operates to decrease the difference between the read "output" value and the desired value.

Front 9

Define: Positive feedback system

Back 9

A feedback system whose regulatory mechanism increases the effect of any perceived disturbance, ultimately driving the system to extremum.

Front 10

Define: Feed-forward control system

Back 10

Control mechanism has predictive quality. Regulation can only come from brain.

Front 11

Define: Control theory

Back 11

Theory of regulation of a system's reaction to disturbance

Front 12

Define: Controller

Back 12

Element of a system responsible for control/regulation

Front 13

Define: Control system

Back 13

System arranged in such a way that it can self-regulate (and/or regulate other systems)

Front 14

What are the limitations of negative feedback?

Back 14

Can correct for disturbances that affect the system, but not those that affect perception of system variables (in which case the "output" that is compared the set-point is not the actual output).

Front 15

How does a physiological variable under positive control returned to its steady-state value after having been driven to an extremum?

Back 15

After reaching extremum, negative feedback control restores the system to its initial set point.

Front 16

Define: Alloteric modulation

Back 16

Regulation of enzyme function by formation of a non-covalent bond with the protein (at the allosteric binding site), resulting in a conformational change that inactivates the binding site

Front 17

When a receptor is sensitive for multiple ligands, which reaches saturation more readily?

Back 17

The one with a greater affinity for the ligand.

Front 18

What factors contribute to the degree of reaction?

Back 18

Reactant/product + modulator/cofactor concentrations (law of mass action)
Activation energy (binding affinity, etc.)
Temperature
Presence/absence of a catalyst

Front 19

Define: Covalent modulation

Back 19

Regulation of enzyme function by formation of a covalent bond with the protein (usually kinase-mediated phosphorylation) that alters enzyme conformation at the binding site.

Front 20

Define: Metabolism

Back 20

The sum of the chemical reactions required for the synthesis and breakdown of organic molecules required for structure and function.

Front 21

What factors contribute to enzyme-mediated reaction rate?

Back 21

Concentrations of products, reactants, enzyme, and modulators
Temperature
Enzyme activity

Front 22

If two enzymes of different substrate affinities have the same reaction rate at saturation, how would their curves (reaction rate as a function of substrate concentration) differ?

Back 22

The enzyme with greater affinity will reach saturation more rapidly (i.e. linear portion will have steeper slope)

Front 23

Why are the steps associate with a large drop in free energy more likely to come under regulation?

Back 23

Because these "committed steps" are the ones that can be assumed to directly influence the forward rate of a particular reaction to the greatest degree (less chance of pushing equilibrium back to the left/branching to other pathways). Also, a large drop in free energy corresponds to a larger range (comparatively) of available reaction rates, so that regulation can result in a large change.

Front 24

What attribute of regulation is highlighted by the relationship between ATP and the enzyme PFK, and why is it important?

Back 24

Feedback by substrate (ATP as a substrate, but also as an allosteric inhibitor).

Front 25

What are the three mechanisms for maintaining [ATP], and which macromolecule classes are associated with them?

Back 25

Glycolysis - Carbohydrates
Krebs Cycle - Fats, proteins, products of glycolysis
Oxidative phosphorylation - Fats, products of glycolysis + Krebs cycle

Front 26

What form of control is exemplified by the activation of PDC (metabolic enzyme) by calcium ions?

Back 26

Feed-forward control: Ca ions released to activate muscle cells simultaneously initiate system of producing ATP (that muscle cells need) even before negative feedback control systems report necessity

Front 27

From what class of molecules (sugars/proteins/lipids) is most of the cell's energy derived?

Back 27

From lipids (from the form trigyceride of Cn s.t. n = 2a, and a some integer)

Front 28

Distinguish direct from indirect active transport

Back 28

In direct active transport ATP binds directly to the protein channel to facilitate pumping of ions across the membrane against a gradient. In indirect active transport, by contrast, the energy stored in a different gradient (of some other molecule--generally established by active transport) is used to establish a desired gradient.

Front 29

By means of which process is a gradient established across a membrane (against the equilibrium gradient)

Back 29

Direct active transport

Front 30

What are the types and associated functions of cell-cell junctions?

Back 30

Desmosomes = Dense, firbrous connections between cells anchor them to one another (firm but flexible mechanical support)
Tight Junctions = Fusion of adjacent cell membranes forces molecules to pass through cytoplasm in order to pass membrane barrier
Gap Junctions = pores that enable passage of small molecules/chemical messengers between cells

Front 31

Which part of the brain is associated with learning and memory?

Back 31

The limbic system = amygdala and hippocampus

Front 32

With what functions are the cerebral hemispheres associated?

Back 32

Perception, skilled movement, executive decision-making, reasoning

Front 33

What are the components and functions of the diencephalon?

Back 33

Thalamus and hypothalamus: Awareness, coordination, hunger/thirst sensation, regulation of the endocrine system and the circadian rhythm

Front 34

With what functions in the cerebellum associated?

Back 34

Posture and movement

Front 35

What are the components and functions of the brainstem?

Back 35

Midbrain, pons, and medulla oblongata
Integration centres for cardio-vascular and respiratory controls; cross-way to the spinal cord

Front 36

Describe the 6 centres of the brain

Back 36

Cerebrum, diencephalon, cerebellum, midbrain, pons, medullaoblongata

Front 37

What was the major lesson of the story of Phineas Gage?

Back 37

Demonstration of a link between behavior and the physical brain. More specifically, that the frontal lobes of the cerebal cortex were related to emotion and practical decision making.

Front 38

What is the cell-type breakdown of the CNS (X% A, Y% B...)?

Back 38

10% Neurons
90% Glial cells

Front 39

What are the types of glial cells?

Back 39

Astrocytes, oligodendrocytes, microglia

Front 40

What are glial cells?

Back 40

"Support" cells of the CNS. Play protective and pseudo-immunological roles.

Front 41

What role do oligodendrocytes play in the CNS?

Back 41

Provide myelin sheaths for neuronal axons that regulate the speed with which signals are passed along the axon (akin to Schwann cells in the PNS)

Front 42

What role do microglia play in the CNS?

Back 42

Phagoytose bacteria to protect the CNS

Front 43

What is the purpose of the myelin sheaths (produced by Schwann cells in the PNS and oligodendrocytes in the CNS)?

Back 43

To increase the speed and decease the energy expenditure of electrical signal transmission along the axon.

Front 44

What are the exposed patches of axon (between lengths of myelin sheath) called?

Back 44

Nodes of Ranvier

Front 45

What roles to astrocytes play in the CNS?

Back 45

-Helps regulate the chemical makeup of the extracellular fluid (includes waste management and glucose concentration, ion/neurotransmitter concentration)
-Induces formation of tight junctions between cells of the blood-brain barrier
-Aids in information integration at the synapses
-Helps regulate growth and positioning of neurons

Front 46

What are ependymal cells and what do they do?

Back 46

Glial cells of the CNS with a role in producing and regulating the flow of cerebrospinal fluid

Front 47

Describe the main processes of a neuron

Back 47

From the cell body, the neuron may extend processes: the dendrites and the axons

Front 48

What is the role of neuronal dendrites?

Back 48

To receive information (generally in the form of neurotransmitters) and then to undergo graded potentials to transmit this information

Front 49

what is the role of neuronal axons?

Back 49

To undergo action potentials that deliver information (typically in the form of neurotransmitters) from the action terminals to other cells

Front 50

What is the central dogma of neuroscience?

Back 50

That mature neurons of the CNS are post-mitotic and non-regeneratable (note that neurons of the PNS can be regenerated)

Front 51

What is the mechanism and functional outcome of Altzheimers disease?

Back 51

Degeneration of cholinergic (using acetylcholine as its neurotransmitter) neurons results in memory loss.

Front 52

What is the mechanism and functional outcome of Parkinson's disease?

Back 52

Degeneration of dopaminergic neurons results in a progressive (and irrevocable) loss of motor function.

Front 53

What is the mechanism and functional outcome of a stroke?

Back 53

Death of neurons in a localized region due to ischaemia (restricted blood flow) results in functional loss within the damaged area

Front 54

In what cases is there exception to the central dogma of neurobiology?

Back 54

In the region associated with learning and memory--recall, we associate this function broadly with the hippocampus--there is a (very tightly regulated) ability to develop even in adulthood

Front 55

Define: Electric potential stored in a membrane

Back 55

The potential to due work (per charged species) by opposite charge separated by a membrane, as determined by the Goldman-Hodgkin-Katz equation

Front 56

What is the Goldman-Hodgkin-Katz equation and what is it used for?

Back 56

The multi-species equivalent of the Nernst equation is used to determine the electric potential across membrane (note that this takes into consideration the intra- and extracellular concentrations and membrane permeabilities of each species)

Front 57

What is the resting membrane potential of a neuron, as determined by the Goldman-Hodgkin-Katz equation?

Back 57

-70mV -- note that this membrane polarization is the resting state with interior of cell negative with respect to exterior

Front 58

What pattern of polarization characterizes an action potential?

Back 58

Rest (polarized) -- depolarization -- overshooting -- repolarization -- hyperpolatization -- rest

Front 59

How is a graded potential different from an action potential?

Back 59

Graded potentials are local (decay over distance), with size proportional to the intensity of the detected signal, whereas action potentials are large, global

Front 60

Identify the three types of channel gating

Back 60

Ligand-gated channels
Voltage-gated channels
Mechanical-gated channels

Front 61

What is the nature of the wave induced in an inhibitory graded potential, and what is its relationship the likelihood of inducing an action potential?

Back 61

Results in hyperpolarization, decreasing the likelihood of action potential

Front 62

What is the nature of the wave induced in an excitatory graded potential, and what is its relationship the likelihood of inducing an action potential?

Back 62

Results in depolarization, increasing the likelihood of action potential

Front 63

What is saltatorial conduction and why is it important?

Back 63

Motion of action potential "jumping" between nodes of Ranvier -- enables rapid transmission signal (note that removal of the sheaths, as in MS, decreases the speed of transmission and makes control more difficult)

Front 64

How does the structure of a primary afferent neuron of the CNS uniquely fit its function?

Back 64

One long axon with very small nucleus (at very small centre). One end has specialized sensory receptor (may be membrane or even a separate cell) and the other synapses onto another neuron (usually to CNS)

Front 65

Distinguish "afferent" from "efferent" neurons

Back 65

Afferent corresponds to "toward the CNS" = sensory

Efferent implies "away from the CNS" = motor

Front 66

By what sort of gating are the ion channels involved in action potentials regulated?

Back 66

Voltage-gated. This allows positive feedback in Na channel opening (changing voltage opens the Na channels rapidly...and they close rapidly just by their nature, preventing backward flow + K channels open slowly providing negative feedback for potential)

Front 67

How are Na channels "inactivated"?

Back 67

They shut down by themselves after some discrete amount of time

Front 68

Describe the functions of the afferent neurons

Back 68

-Translating stimuli into electrochemical signals
-Coding these signals so that they may be properly interpreted by the CNS
-Propagating these signals along axon
-Transfering these signals to the CNS via synaptic transmission

Front 69

What are EPSPs and IPSPs and how do they contribute to the formation of an action potential?

Back 69

Excitatory postsynaptic potentials and inhibitory postsynaptic are graded depolarizations and hyperpolarizations (respectively) which, summer together spatially or temporally, contribute to the formation of an action potential

Front 70

What mechanisms result in the summation of EPSPs and/or IPSPs?

Back 70

Temporal (i.e. repeated stimulus at one receptor sends signals within small enough time window as to result in wave interference) and spatial (i.e. stimulus of multiple receptors within same region results in distinct stimuli that interfere) summations

Front 71

Define: sensory transduction

Back 71

Translation of stimulus to graded potential (signal)

Front 72

Define: rate coding in the single-neuron context

Back 72

Translation of initial receptor signal to signal in action potential (summation of graded potentials), usually by with graded potential intensity corresponding to action potential frequency

Hint 72

We're thinking about a SINGLE neuron, so that's from the signal received to the action potentials induced

Front 73

What characteristic of photoreceptor neurons make them unique?

Back 73

Stimulating photoreceptors results in a graded potential that is never coded to an action potential because synapse directly to retinal ganglion cells (which have action potentials without graded potentials)

Front 74

Define: synapse

Back 74

Anatomically specific junction between neurons (or between a neuron and another cell type) at which information may be passed rapidly via electrical or chemical signals

Front 75

How does chemical synapse work?

Back 75

Receptor on pre-synaptic cell induces release of neurotransmitter into synaptic cleft. Binding of neurotransmitter to ligand-gated sodium channels induces voltage change to induce graded potential (subject to temporal and spatial summation) in post-synaptic cell.

Front 76

Define: receptive field

Back 76

Given a single neuron, the receptive field is the corresponding sensory region where stimulation results in response

Front 77

Define: 2-point discrimination

Back 77

Way of determining size/scope of neuronal receptive fields, by ability to discriminate between multiple points of contact

Front 78

Define: sensory adaptation

Back 78

Reduction of signal response to a repeated/continuous stimulus (as with a scent)

Front 79

Distinguish (functionally) primary from association cortices

Back 79

Primary sensory cortices are limited to single modalities with less processed information. Generally functions in these areas are not perceived. Association sensory cortices may deal with single (unimodal) or multiple (multimodal) modalities, deal with relatively more processed information. Activities here can generally be perceived.

Front 80

Define: Perception

Back 80

Awareness gained from associative processing of sensory information

Front 81

Define: Gestalt effect

Back 81

Effect of unimodal association processing: Form-forming ability of our brains (consider optical illusions...vase or two faces)

Front 82

Explain: cocktail party phenomenon

Back 82

Effect of unimodal association processing: We are able to distinguish and focus on some sounds over others in a noisy place

Front 83

What factors determine the velocity (speed AND direction) of action potential propagation?

Back 83

Speed: (existance and) spacing of nodes of Ranvier, diameter of axon--myelination and increased diameter increase speed

Direction: The refractory period of an action potential results in uni-dimensional motion of the action potential

Front 84

How is the repolarization stage of action potential terminated?

Back 84

Slow opening of potassium voltage-gated channels (beginning at membrane potential ~ +30mV) initiates repolarization, which begins to shut off at around -50mV (note slow opening/closing of potassium channels results in hyperpolarization before returning to resting potential)

Front 85

What characterizes the refractory period of an action potential and how does this inhibit re-activation?

Back 85

It is during this time that the membrane is being repolarized, hyperpolarized, and then returned to resting potential.

Front 86

Which characteristics make the pre-frontal cortex best adapted to feed-forward control and the spinal cord best for feedback control?

Back 86

The pre-frontal cortex is the site of executive decision-making, and is therefore able to make dictate predictive responses. Also, it is far enough from stimuli that it could not produce rapid enough feedback responses to be completely dependable.

The spinal cord has no associative machinery, and so is incapable of predictive action. It, however, close to stimuli and developed enough to dictate complex patterns of action.

Front 87

What is the motor servo?

Back 87

The spinal negative feedback control mechanism that integrates muscle stretch and force receptor signals to regulate stretch, force, and related variables

Front 88

What is the size principle?

Back 88

That, when force sensors dictate the need for recruitment of more motor neurons, smaller neurons are recruited before larger motor neurons (note that this principle beaks down for humans)

Front 89

Which receptors are responsible for detecting force on a muscle?

Back 89

Golgi tendon organs (GTOs)

Front 90

Which receptors are responsible for detecting length in a muscle?

Back 90

Muscle spindles (via stretch monitoring)

Front 91

What is "recruitment" and when is it necessary?

Back 91

When a stimulus dictates that more force is required from a muscle, more motor units are made available

Front 92

What is "rate coding" (in the context of motor control) and when is it necessary?

Back 92

When force is exerted on a muscle (or a collection of recruited muscles), each motor unit is rate coded--that is, the frequency of action potentials is regulated to determine the amount of force exerted by that motor unit (with higher frequency corresponding to greater force)

Front 93

How are smooth forces induced in the (most common) scenario that tetnus is not reached?

Back 93

If many small motor units are recruited asynchronously, then the addition of these many small, out-of-phase waves will ultimately sum to a smooth force

Front 94

What do we define (broadly) as consciousness?

Back 94

Awareness of a distinct, identifiable self with internal processes that can be situated in four-dimensional space-time.

Front 95

What is the organization of motor control?

Back 95

Hierarchical, with cortical command centres (read: frontal lobes) dictating activity through other parts of the cortex, the basal ganglia, thalamus, cerebellum and brain stem to the spinal cord and out to muscles

Front 96

What is the highest level of motor control hierarchy, and what control system is it?

Back 96

Cerebral cortex exerts feedforward control

Front 97

What are the middle components of the motor control hierarchy, and what control system(s) does it exert/represent?

Back 97

Feedforward and feedback motor control occurs at the cortex, basal ganglia, thalamus, cerebellum, and brainstem

Front 98

Which areas of the cortex are associated with motor control, and what are their roles?

Back 98

Prefrontal cortex -- long-range planning, intentionality

Premotor + parietal cortices -- short-term planning and movement programming

Primary motor cortex -- organization and sending out of signals to muscles via axons that synapse directly onto the spinal cord (note that there is a homunculus component to this, just as in the somatosensory cortex immediately dorsal)

Front 99

Which areas of the cortex are associated with short term planning and movement programming?

Back 99

Pre-motor and parietal cortices

Front 100

What part of the cortex is responsible for long-term planning and intentionality?

Back 100

The pre-frontal cortex

Front 101

Which part of the cortex is responsible for organizing and sending signals to the muscles?

Back 101

The primary motor cortex

Front 102

What is the role of the middle levels of the motor control hierarchy?

Back 102

Coordination of precise movements, orientation, posture (via brainstem), and timing, etc.

Front 103

What are the components of a motor unit?

Back 103

1) A single motor neuron
2) All of the (usually many) muscle fibres that it innervates (note that motor units tend to overlap)

Front 104

Describe a motor unit action potential

Back 104

Occurs at the neuromuscular junction with acetylcholine (ACh) as the neurotransmitter (Ca ions into neuron result in release of ACh vesicles). Synapse causes action potential in all muscle fibres belonging to the muscle unit.

Front 105

How is more force derived from a muscle?

Back 105

By a combination of recruitment of multiple muscle units (spatial overlap) and rate coding (temporal overlap).

Front 106

Action potentials in muscle neurons result in Ca release from sarcoplasmic reticulum. What is the effect of these Ca ions on the actual muscle cells?

Back 106

Allosteric regulation: Ca ions signal release of regulatory proteins from actin binding site on myosin motors

Front 107

Which is the actin molecule and which the myosin?

Back 107

The actin is the track(tin) and the myosin is the motor

Front 108

In a broad sense, how does muscle contraction work?

Back 108

Hundreds myosin motors per myosin filament use energy from ATP hydrolysis to pull on actin filaments to contract the muscle

Front 109

How is the mechanism of myosin action specialized for the needs of muscle cells?

Back 109

Muscular motion requires rapid contraction, which is effected by these hundreds of motors moving out-of-sync, such that there is no requirement of constant contact for each individual motor (this is distinct from other motor proteins, like kinesin, which are processive)

Front 110

What factors of fibre structure contribute to muscle effectiveness

Back 110

-That the most common muscular proteins are actin and myosin
-Unidirectionality of force production results in constructive interference of force
-Parallel tracks along with force is produced implies that all force is productive

Front 111

What traits characterize the consciousness state of arousal?

Back 111

Increased wakefulness, vigilance, responsiveness to cortical and thalamic neurons of sensory stimuli

Front 112

What traits characterize coma?

Back 112

Severe decrease in mental function

Front 113

What are the common causes of coma?

Back 113

Damage due to trauma, infection, metabolic dysfunction, drug overdose

Front 114

What is the role of the brain stem in consciousness?

Back 114

Modulation of signals from spinal cord to brain and vice versa (sensation and movement)

Front 115

Degree of arousal is modulated (primarily) through which areas of the brain?

Back 115

Thalamus and hypothalamus

Front 116

What is the role of the thalamus on arousal?

Back 116

Cortical activation, the sleep spindle (bilateral removal of the thalamus results in coma) -- thalamus is necessary (but NOT sufficient) for consciousness

Front 117

What is the role of the hypothalamus in arousal?

Back 117

Contains the "sleep/wake switch" and the SCN (which controls the circadian clock

Front 118

What is the role of the pre-frontal cortex in consciousness?

Back 118

Long-term planning, intentionality, "this is a good/bad idea" modulation

Front 119

How does the EEG machine work?

Back 119

Detection of potential differences between pairs of electrodes establishes a map of synaptic activity for the cortex which can (though generally doesn't) reflect action underneath as well.

Patterns in the amplitude and frequency give information about the number of synchronously activated neurons and degree of responsiveness, respectively.

Front 120

What frequency and consciousness state is associated with alpha waves?

Back 120

8-13 Hz indicates relaxed wakefulness

Front 121

What frequency and consciousness state corresponds to beta waves?

Back 121

13-30 Hz, intense mental activity/concentration

Front 122

What frequency and consciousness state corresponds to theta waves?

Back 122

4-7 Hz = slow-wave sleep

Front 123

What frequency and consciousness state correspond to delta waves?

Back 123

0.5-4 Hz = stages 3 & 4 in the sleep cycle

Front 124

Arrange the EEG wave types according to degree of wakefulness (least to greatest)

Back 124

Delta, theta, alpha, beta

Front 125

What are the stages of sleep, and how long does a cycle last?

Back 125

Stages 1-4 + REM. The cycle lasts about 90 minutes, though the duration of the REM period increases throughout the night.

Front 126

List the given hypotheses on the function of sleep

Back 126

Energy conservation, memory consolidation, neuronal replay (reactivation of neuronal circuits), homeostasis of synapses (refresh button)

Front 127

What traits characterize implicit memory?

Back 127

It is instinctive (non-declarative) and tends to be procedural -- figures in the sequence and relationships between events. Recall is unconscious.

"Just like riding a bike"

Front 128

What traits characterize explicit memory?

Back 128

It is declarative, tends to relate to discrete facts and events in one's direct experience. Recall is conscious.

Front 129

Describe the stages of memory storage shared by implicit and explicit memory

Back 129

Input processed into working (easily-disrupted) memory, then translated to a long-term (stable) store

Front 130

How is memory storage affected by age?

Back 130

Over time, one's ability to adapt working to long-term memory diminishes

Front 131

In which structures is declarative (explicit) working memory encoded?

Back 131

Structures of the temporal lobe (esp. the hippocampus)

Front 132

In which region of the brain are declarative (explicit) memories encoded?

Back 132

In the associative cortex(ices)

Front 133

In which region of the brain is procedural (implicit) memory encoded to working memory?

Back 133

Trick question! It's widely distributed throughout the brain.

Front 134

In which structures of the brain are long-term procedural (implicit) memories encoded?

Back 134

Basal nuclei, cerebellum, premotor cortex

Front 135

What are the processes of forming (and consulting) an explicit memory?

Back 135

Encoding (processing and association), storage, consolidation (movement of short- to long-term; requires generation of new neurons), and retrieval

Front 136

What is long-term potentiation and with what region is it associated?

Back 136

Sort of a Pavlovian neuron response: enhancement of communication between neurons by simultaneous stimulation. Generally associated with the functions of the hippocampus.