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Beyond Midterm 2


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What is a quantal release?
-quantal releases produce miniature PSP (mPSP)
-low freq, random release of approx. 5000ACh molecules/quanta
-need approx 300 quanta to produce stimulated EPSP
What exactly are neurotransmitters?
-small molecules (amino acids)
-many neurons use only 1 NT, but some use more than 1 NT
-NT can have various effects on the post synaptic cell, effect depends on the receptor
What are the 2 ways that the synapse stops neurotransmission?
1)Enzymatic Destruction:
-special enzymes break down NT, after all, NT's are just proteins.
(Eg: acetylcholinesterase)

-NT's are actively transported back into the axon from which it came
-glial cells may also be involved
How do Ionotropic Receptors work?
(ie: nAChR)
-has a direct effect of ligand(NT) binding on receptor
-if receptor is unbound by ligand, ion channels are closed
-if receptor is bound by ligand, ion channels are open
*synaptic currents from each channel sum*
How do Metabotropic Receptors work? (eg: nAChR)
-has an indeirect effect of ligand(NT) binding on receptor
-acts through intracellular messengers like G-proteins and G-protein coupled receptors
-if inactive: subunits bound together and alpha subunit bound to (GDP)

-if active: -alpha subunit dissociates from others and GDP picks up P, becoming GTP
-alpha subunit/GTP migrates through membrane, binds to and opens K channels, causing IPSP's
1)A band
2)I band
1)The 'dark' band
-made of myosin(thick filament) and contains the H-zone and M-line

2)The 'light' band
-made of actin(thin filament and contains the Z-disc

**myofibrils are made of repeating A-bands and I-bands**
What is the H-zone?
-the zone in the A-band where only myosin is present
-thus during contraction, the H-zone shrinks

-the H-zone is bissected by the M-line
What are muscles composed of?
1)sarcolemma: the outer skin
2)muscle cells:
-each composed of lots of fibers
-each fiber composed of bunch of myofibrils
-myofibrils are made of actin and myosin
What is the structure of myosin molecultes?
-has a long tail which connects to the M-line
-has two heads, each head is fully capable of binding ATP and Actin
-ATP site is and ATPase that breaks ATP ADP, releasing energy in the process
Go over the 6 steps in the sliding filament model.
1)Myosin is bound actin (in state of rigor)

2)ATP binds to myosin head and head detaches from actin

3)Myosin ATPase breaks ATP to(ADP + P).
The processes changes the angle of the head but DOES NOT RELEASE either ADP or P from myosin head yet

4)The myosin head moves to the cocked position and binds to the actin molecule

5)Once attached, the myosin releases the P and in turn causes a power stroke, inching the actin 10nm closer to the M-line

6)The myosin head releases the ADP but remains tightly bound to the actin(rigor)

*since myosin has 2 heads, it 'walks' the actin closer to the M-line*
Why is Ca needed for muscle contractions?
-actin has 2 regulatory proteins:
1)troponin(TN): golfclub shape, head binds to actin, handle binds to TM
2)tropomyosin(TM): rides on back of TN and covers about 7 actin/myosin binding sites

-Ca binds to TN which causes it to move, thus causes TM to move, exposing the actin/myosin binding sites
-otherwise, these sites are covered and myosin can't bind
What are sarcomeres?
-the portion between Z-lines
How does neural excitation trigger skeletal muscle contraction? 6 steps.
1)The AP from presynaptic nerve triggers release of ACh

2)ACh binds to receptors on sarcolemma, triggering AP's along the sarcolemma

3)AP propogates all over the sarcolemma and eventually depolarizes T-Tubules found on the sarcolemma

4)Voltage sensitive DHPR is found in the T-Tubule. If DHPR is depolarized, it causes a conformational change that opens the RyR Ca channels of the sarcoplasmic reticulum (SR)

5)Ca from SR binds to TN, therefore TM moves and myosin can bind

6)Cross-bridges go through several cycles as long as Ca remains bound to TN

**Whole process is called
"Excitation-Contraction Coupling"**
What is the sarcoplasmic reticulum(SR)?
-the SR is a network of branching tubules contained entirely within the muscle fiber
-stores Ca which is released when DHPR stimulates RyR
What is Isometric Contraction?
-'same length'
-the sarcomeres shorten VERY slightly during isometric contraction(ie: bicep bulge)
-elastic elements stretch, therefore muscle stays the same length
What are elastic elements in terms of muscle contraction?
2 Parts:
1)Series elastic elements include:
-the connective tissue surrounding individual muscle fibers
-components of the myofibrils(Z-discs and cross bridges)

2)Parallel elastic elements include:
-sarcolemma and connective tissues running parallel to myofibrils
What are Isotonic contractions?
2 Parts:

1)Concentric Contraction:
-Elastic elements are stretched and the muscle shortens(ie: move hand close to face)

2)Eccentric Contraction:
-Elastic elements are stretched, and the muscle lengthens(ie: squatting)
T or F

A motor neuron is only capable of stimulating 1 muscle fibre.
-remember that axons of neurons branch and can therefore make contact with multiple fibres
-each contacted axon can produce a MAP if it delivers an AP
What is a motor unit?
-a motor unit is the motor neuron(Mn) and the muscle fiber
What does DHPR and RyR stand for?
- DHPR = DiHydroPyRidine

- RyR = Ryanodine Receptor
What is tension?
-the force exerted by muscles on an external load
What are 3 ways to alter tension?
-motor unit recruitment(ie: temp summ)
-length/tension relationship(stretch)
-summation of contraction(tetanus)
What is a muscle twitch?
-the mechanical response of a muscle to a single action potential
Describe the difference of latent period, contraction period and relaxation period between isometric and isotonic contractions.
-small LP
-med CP
-large RP

-large LP
-med CP
-smaller RP
Describe the load velocity relationship. (ie: what happens to shortening velocity if load increases?)
-the velocity of shortening decreases as load increases

-this is because the excitation-contraction coupling must occur, and the cross-bridges must develp enough tension ismoetrically to overcom the force exerted by the load
Explain what happens, in terms of tension produced, as you stretch a muscle.
1)Tension increases linearily:
-decrease overlap, therefore allow room for contraction(big H-zone)

2)Max's out and plateaus:
-optimal room and contacts made

3)Declines to 0:
-contacts are lost and eventually completely pulled apart
What is recruitment of motor units?
-increases the number of active motorunits
-the dominant means used to control the amount of tension produced in vertebrate twitch muscles
What's the difference between multiterminal and polyneuronal innervation?
Multiterminal Innervation:
-one motor neuron branches to innervate muscle fibres (vertebrates)
-don't overlap

Polyneuronal Innervation:
-two or more motor neurons are used to innervate muscle fibres (arthropods)
What are 2 factors that affect the amount of work possible?
1)Cross sectional area of myofibril:
-the thicker = more myosin/actin contacts = more work

-sarcomere shortening summates therefore more work
What are the 3 types of vertebrate muscles?
1)Skeletal Muscle

2)Cardiac Muscle

3)Smooth Muscle
How do you find active tension?
Active tension = total - passive
1)Sensory Receptor Cell
2)Sensory Organs
3)Sysory Systems
1)Detects environmental signal
2)groups of sensory cells
3)sensory cells/organs +CNS
4)type/quality of signal
5)Detect external stimuli
6)Detect internal stimuli
7)Detect orientation of joints and muscles
What are the 5 types of sensory receptor categories (modalities)?
1)Mechanoreceptors: touch, stretch, sound, etc.

2)Photoreceptors: light

3)Chemoreceptors: taste, smell

4)Electroreceptors: ie-elec fish sends out current

5)Thermoreceptors: temperature
What are the 4 common functions of sensory receptors?
1)Detection: usually via membrane proteins

2)Transduction: sensory energy converted to cellular energy

3)Amplification/Filterin: often through secondary messengers

4)Electrical Output (Integration/Spreading): sends output to CNS
How does the central nervous system recieve info?
-recieves info as AP's
-sensory receptors can only alter AP freq and timing
-CNS figures what's up by the freq and timing of AP's
What is 'encoding'?
-how sensory cells prepare AP freq and timing related to the stimuli's properties

**has 4 properties**
What is 'decoding'?
-how the CNS interprets sensor modality and quality
-often based on anatomical connections in CNS
What is the 'Labelled Line Principle'?
-axons carrying info about specific modality project to same area of CNS

-explains why any stmiulation of a particular receptor is perceived as the same modality
What are the 7 general features of sensory receptors?
1)Stimulus causes a receptor potential:
-usually inward I(Na), but can be outward I(K)

2)Current spreads electrotonically to SIZ if Vm=V(thresh) => AP

3)Receptor potentials are graded:
-stronger stimulus = more channels open
-larger I(Na or K) movement

4)Larger receptor potentials = higher AP freq b/c V(thresh) reached more often)

5)Sensory receptors respond over a dynamic range:
-min and max detection limit
-related to basic membrane properties

6)Sensory receptors may be spontaneously active

7)Sensory receptors may show adaptation
What 4 main properties of the stimulus that sensory receptors encode?
-what is it?
-uses labelled lines
-can determine quality (eg:color)

-how much?
-usually encoded in # of AP's
-recruitment can extend the range of sensitivity

-where is it?
-usually encoded via labelled lines

-When? How is it changing?
-usually encoded via adaptation
-can also encode location (eg: time difference of each ear)
What factors account for receptors showing maximum AP frequency?
-limited # of ion channels limits size of receptor potential
-length of refractory period limits AP frequency

*if RP intensity plotted against log of stim intensity, increases linearily then levels out*

Same percentage change in stimulus intensity DOES NOT produce the same response in AP freq.
-if the change is the same percentage, the response will be the same, no matter what actual numbers the percentages convert to...

*see Nov.12 notes, you'll know what i mean*
What are Parallel Pathways?
-many sensory neurons converge and are summed by CNS
-reduces sensory noise
What is sensory adaptation?
-firing freq decreases with prolonged stimulus
-allows for detection of 'different' stimululi in presence of background (ongoing) stimuli

2 Types:
1) Tonic Receptors: slow adaptation
2) Phasic Receptors: fast adaptation
T or F
Adapatation allows some receptors to be velocity detectors.
-AP's reflect how intense velocity is
-greater velocity = greater AP freq
What is efferent control?
-input to the sensory receptor from the CNS
-can modulate responses (eg:excite or inhibit sensor)

**CNS can set sensitivity of sensors**
What is afferrent control?
-sensory cell sends stimuli to CNS
What is range fractionation?
-because sensory organs have their own dynamic range (min and max), combining organs with diff ranges increases the sensitivity range
What are mechanoreceptors?
-receptors that responds to mechanical deformation of membrane
-opens mechanically gated ion channels, result is an RP

*5 types*
What are the 5 types of mechanoreceptors in vertebrates?
1)Simple Mechanoreceptors:
-single sensory neuron
-axon projects directly to CNS
-some touch receptors but most are stretch receptors

2)Complex Mechanoreceptors:
-more than one sensory neuron
-generates inward I(Na or K)
-eg: sensory hairs of insects, vert hair cells

3)Stretch Receptors:
-attached to muscle cells or connective tissue
-encoded as firing freq. (relative to degree of stretch)

4)Vertebrate Skeletal Muscle:
-senses muscle length(eg:proprioceptor)
-can also detect changes in length adaptation

5)Golgi Tendon Organ:
-senses muscle tension
-found b/t bone and tendon
What are hair cells?
-single cell with hairs on it
-used to sense equilibrium and hearing

common features:
-receptor cells don't have axons, synapse onto afferent neuron
-afferents project to CNS
-receptor cells release NT
-cells bathed in endolymph
depolarized by inward I(K)
-efferent inhibition can maintain sensitivity
-stimulus affects the amount and rate of NT release
How are hair cells used to establish equilibrium in invertebrates and vertebrates?
-statolith(rock) free to move in fluid
-displaces hair cells, cause RP, cause AP's
-simple gravity, complex gravity & accel

-3 semicircular canals (SC) provides
3-D sensitivity
-hairs are embedded in gelatinous cupula
-movement of endolymph(cupula) deflects hairs
-AP's conducted to CNS
How are hair cells used in hearing?
-detects small changes in air pressure due to sound waves
-freq of pressure changes pitch
-sound vibrates the Tympanic membrane (ear drum)
-transmitted to fluid-filled inner ear by middle ear bones
-sound detected by hair cells in cochlea which is filled with perilymph
-width of basilar membrane and placement of hair cells proveids freq discrimination
-transduced sound waves vibrate basilar membrane. (low freq near apical end, high freq near basal end)
-pitch encoded by place of maximal vibration

*I go into detail of the organ of corti later*
How are hair cells used in the organ of cortii?
-mechanically coupled to basilar membrane via Tectorial membrane either directly (outer hair cells) or via viscous fluid (inner hair cells)
-most auditory input via afferent axons from inner hair cells
-movement of basilar membrane produces shearing forces on hair cells
-opens mechanically gated K channels, result is depolarizing RP
-hair cells release NT which produces an EPSP in afferent neuron
What is a camera eye?
-forms a single image
-has high spatial resolution (ie: can see the difference between 2 spaces in 2-D or 3-D
What is a compound eye?
-forms a mosaic image (can see multiple images with slightly different angles. Therefore better at seeing things that move quickly)
-has high temporal resolution

**our flicker fusion frequecy is about 15-30FPS, insects flicker fusion freq is about 80-120FPS**
What is the funcion of:
6)Outer segment
7)Inner segment
... in the vertebrate eye?
1)controls the amount of light

2)Terrestrial-changes shape to focus
Aquatic-changes position to focus

3)has phoreceptors and neurons

4)color vision, high accuity, continous with outer cell membrane

5)more sensitive to low light, no color, internalized flattened disks

6)photosenstive membranes

7)organelles and synaptic terminals

8)photopigment on membrane
What is the function of:
3)Apposition eyes
4)Superposistion eyes
... in the invertebrate compound eye?
1)The polygonal components that make up the eye. Each ommatidium has a set of lenses.

2)Composed of rhabdomeres on retinular cells. Contains rhodopsin.

3)has better temporal resolution (1 lens / 1 rhabdom)

4)better light gathering ability when dark adapted. Little less of a mosaic (many lenses / 1 rhabdom)
How does visual processing work in vertebrates?
-visual information comes from patterns of light and dark
-Retinal Ganglion Cells (RGC) receives input from many photoreceptors. Summed +'ve or -'ve inputs
-RGC's send info to the CNS
-RGC's project along parallel pathways to visual cortex
-specific postsynaptic neurons used to discriminate spatial and temporal properties
What's the difference between SPATIAL and TEMPORAL in terms of visual processing properties?
-Spatial: detects objects

-Temporal: detects movement
What is a receptive field?
-the area of fild of view that receptors or retinal ganglion cells are able to detect
What is DCMD?

**detects looming stimuli (ie: AP frequencies increase drastically when an object is close so that you know to react**
What is chemoreception?
4 Main Categories:
1)General chemical sensors-insensitive, nondiscriminating

2)Internal chemoreceptors- eg:blood glucose receptors

3)Contact chemoreceptors- high threshold (eg: taste)

4)Distance chemoreceptors- high sensitivity (eg: odor)
-respond to chemical stimuli
-oldest sensory system
-individual receptors discriminate seperate chemicals
-[chemical] encoded as AP frequency
-labelled line representation in brain
What is Gustation?
-vertebrate taste
-non-neuronal receptor cells grouped into taste buds
-each receptor has a preferred chemical sensitivity
-brain decodes taste via across fibre activity (important for complex chemicals)
What physiological processes are involved in salty and sour tastes?
*very simple*
-pos charge through cation channels
-closes K channels, depolarizes the cell and NT's are released
What physiological processes are involved in sweet, umami and bitter tastes?
**these tastes involve G-protein secondary messengers**

1)Sweet: cAMP activates protein Kinase A (PKA) which closes K channels

2)Umami: specific for monosodium glutamate (MSG). Ca release increases the release of NT

3)Bitter: directly blocks K channels. Secondary messenger, Ca is released
How does Olfactory Transduction(smell) work?
**2 described mechanisms, both use secondary messengers**

1)cAMP Pathways
-opens cation channels
-inward I(Na) and I(Ca)
-I(Na) causes depolarization
-I(Ca) enhances by opening Cl channels, creates outward I(Cl)

2)IP3 Pathway
-opens Ca channels - depolarizing
-also opens Cl channels
What are the 4 homeostatic mechanisms animals use to respond to environmental changes?
1)Change: internal/external

--sensory modality and quality--

2)Detection: sensory receptors

--afferent input and sensory neurons--

3)Integration: brain and spinal/nerve cord. (filtering, genetic/learned info, perception, response generator)

--efferent output and motor neurons--

4)Response: physiological or behavioural

--pos and neg--
What is neural integration?
-a generation of a motor output based on the sum of sensory inputs to a neuronal network
What are the 4 really important evolutionary stages of the nervous system?
1)Ability to control and respond to changes in membrane potentials:
-all organisms use membrane potentials to control behavior/physiology
-eg: locomotion in paramecium (dir and rate of cilia beating)

2)Developement of neurons and reflex arcs to conduct electrochemical sigs:
-first neurons appear as diffuse nerve nets of cnidarians

3)Organization of neurons into ganglia and developement of more complex reflex arcs, AKA Ganglia

4)Clustering of ganglia in a central region (brain; cephalization) and developement of most complex reflex arcs:
-a brain first appears in annelid worms
-brain reg centers exert control over rest of nervous system
-most highly organized in vertebrates
-brain is usually located at the anterior end
-with each stage, ability to control behavior and physiology increases because of the number of synaptic contacts increases
-in most developed nervous systems, very complex patterns and control mechanisms are seen
-ability to learn and remember are based on previous experiences also increases
Define reflex arcs.
-synaptic connections between one or more neurons
What is a ganglion?
-complex reflex arcs
-a cluster of nerve cell bodies organized around a tangle of nerve fibers called a neuropile
-ganglion allow for connections between nerves in a small space, more synapses=more integration
-ganglions perform specific functions whereas the brain is more varied
What are some characteristics of the vertebrate nervous system?
-shows the highes degree of complexity because has the highes # of neurons
-human cerebral cortex:
=>2E7 neurons/cc
=>whole brain has 10E12 neurons
=>whole brain has 10E13 glial cells
=>each neuron forms 50,000 synapses
-NS consists of brain, dorsal nerve cord, and zillions of neurons
-rudimentary segmentation exists in the cranial and spinal nerve roots
-where there is ganglia, there is integration
What are the 2 types of cells in the vertebrate CNS?
1)Neuroglia (Glial Cells)
-most numerous (5-10x more)
-fnct to support & protect(nurse cells)
-also use membrane potentials, but no AP's per se
-modulates NT's around the synapse
-several different types for diff fncts (ie: making myelin, cerebral spinal fluid, etc.)

-many different shapes
-3 fnct'l types (sensory, motor and interneurons)
-cell bodies in grey matter; fibers in white matter (myelin)
What are the 2 sub-systems that make up the vertebrate nervous system?
1)Central Nervous System (CNS):
-Higher Brain (cortical region)
-Lower Brain
-Spinal Cord

2)Peripheral Nervous System (PNS):
-efferent motor system
=>somatic nervous system
=>autonomic nervous system
->sympathetic NS
->parasympathetic NS
-afferent motor system
What is the structure of the vertebrate spinal cord?
-sensory neurons enter spine through dorsal root, then makes synaptic contact with spinal cord
-motor neurons exit spine through ventral root
-sensory neurons can extend up/down the spine, therefor spine can communicate along it's length
-grey matter inside, white matter outside
What is the vertebrate autonomic nervous system?
-describes motor nerves innervating smooth muscle, cardiac muscle and glands
Whats the difference between the somatic NS and the autonomic NS?
Somatic NS:
1)conscious control of skeletal muscle
2)only stimulates (ie: ACh)
3)directly innervates effectors

Autonomic NS:
1)involuntary control of viscera
2)Stimulates and inhibits
-uses at least 2 diff NT's (ACh and norepinepherine)
3)synapse first within autonomic ganglion
In the Higher Brain/Cortical Region, what is the function of the cerebral cortex?
-information storage (memory)
-conscious muscular movement (motor region)
-interpretation of sensory info (sensory region)
-reasoning, intelligence, judgement, thought, etc. (*the association region)
-speech and writing
-higher emotions

**most diverse in comparison evolutionarily**
In the Lower Brain Region, what is the function of medulla oblongata?
-involuntary relexes (heart rate, repiration, blood pressure)
In the Lower Brain Region, what is the function of pons?
-connects spinal cord to brain
In the Lower Brain Region, what is the function of the midbrain (mesencephalon)?
-auditory and reflexes
In the Lower Brain Region, what is the function of the thalamus?
-relay center to cortex; pain
In the Lower Brain Region, what is the function of the hypothalamus?
-controls autonomic NS: endocrine glands, body temp, food/water intake, sleep, rage
In the Lower Brain Region, what is the function of the cerebellum?
-unconscious motor control of posture and balance
What are the functions of the spinal cord?
-extension of the medulla
-2 way conduction path between periphery and brain
-segmental arrangement
-controls many unconscious motor reflexes
What are the 3 types of Autonomic Ganglia?
1)Sympathetic Trunk Ganglia
(Vertebral Chain):
-now on both sides of the vertebral column
-contains sympathetic Pre-G fibers and Post-G cell bodies
-preganglionic cell bodies in thoracic and lumbar regions of spinal cord

2)Prevertebral Ganglia:
-anterior to spine, usually near large abdominal artery
-Pre-G cell bodies in thoracic region of spinal cord

3)Terminal Ganglia:
-lie in or near affector organ
-preganglionic cell bodies in brain or sacral region
What are the NT's and receptors are used in the autonomic nervous system?
For Sympathetic:
-CNS->Ganglion - NT=ACh
- Receptor=nicotinic
-Ganglion->Effector - NT=norepinephrine
- Receptor=alpha(1-4)and
beta(1-3) adrenergic
For Parasympathetic:
-CNS->Ganglion - NT=ACh
- Receptor=nicotinic
-Ganglion->Effector - NT=ACh
- Receptor=Muscrinic
(M1, M2[heart], M3, M4[gut])
What are adrenergic NT's?
-a family of neurotransmitters
-includes norepinephrine, adrenaline, dopamine, etc.
-influences adrenergic receptor
L-DOPA->enzyme A->Dopamin->enzyme B->
Norepinephrine->enzyme C->Epinephrine

*since they are all derivatives of eachother, the can interact with diff receptors and vice versa*
What is the role of the Adrenal Medula in the Autonomic Nervous System?
-adrenal is an endocrine gland located at the apex of the kidney(hormone)

-consists of 2 endocrine portions:
1)adrenal cortex(inside)
-secretes various steroid hormones (eg: adrenalcorticoids, cortisol[stress buster])

2)adrenal medulla(outside)
-secretes catecholomine hormones (epinephrine and norepinephrine)
-adrenal medula directly innervated by sympathetic preganglionic fibres
-synapse directly on chromaffin cells
-chromaffin cells secrete EPI(75%) and NOR(25%) into blood stream
-EPI and NOR then act on most adrenergic receptors
-hormonal effects of EPI and NOR last longer (10x's) than that of NOR released at synapse
-amplifies effects of sympathetic nervous stimulation
What are the physiological actions of the autonomic nervous system?
-parasympathetic and sympathetic divisions are generally antagonistic
-precise effect depends on organ
-both are usually active simultaneously
-overall effect depends on the degree to which each division is activated (like a teeter-totter)
-sympathetic tends to be more active when body must mobilize energy reserves
-under severe conditions, adrenal gland augments sympathetic system
(ie: flight or fight response)
-parasympathetic tends to be activated to conserve or restore body energy
(ie: rest or repose response)
What effect does sympathetic activation and parasympathetic activation on the visceral effector have on:
5)Blood Vessels
7)Urinary bladder
8)Arrector pili
**Just look at the sheet... but here is a HUGE hine**

-Sympathetic activation dominates when being chased by a bear.

-Parasympathetic activation dominates when chillin out

**Use your common sense!!**
4)Fixed pattern behaviours
5)Adaptive behaviour
6)Categories of learning and memory
1)synthesis of an output based on the sum of the inputs to a neuron or neural network

2)change in behaviour as a result of experience

3)ability to restore and recall memory

4)'hard wired' neural circuits, instinct

5)based on learning and memory

6)non associative learning (eg: habitualization and sensitization)
-associative learning(eg: pavlov's dogs)
What are the features of the CNS that underlie integration?
1)Specific connections between enzymes
-determined during developement

2)Complex and varied neural circuits because of:
*****i)convergence & divergence
-allows signals to be sent to multiple levels
-synapses may be inhibitory or excitatory
-response of receiving all info depends on relative # of eachother
-tons of NT's
-NT's can be colocalized
-each NT can have >1 receptor
-some NT's may cross react with related receptors
-#'s of receptors on a cell may be modified
*****iii)Feed back loops
-Renshaw Cells can cause an inhibitory effect, preventing tetanic type contraction(-'ve feedback)
-Reverberating Circuit keeps loop going, may be good for memory(+'ve feedback)
-summation results from the addition of graded potentials in the dendrites
-may be temporal summation
-may be spatial summation (ie:convergence)
-combines effect of EPSP's and IPSP's

3)Synaptic plasticity (changes) because of:
For synaptic plasticity, what is the difference between facilitation, potentiation, and depression?
1)NT is released during tetanus

2)NT is released after tetanus

3)NT is inhibited during tetanus
What is behavioral habituation?
-getting used to certain stimulus therefor reaction decreases with time

-can become de habitualized by new stimulus
For the gill withdrawal reflex of aplysia, why does EPSP decrease with prolonged stimulus?
-inactivation is due to a decrease in Ca in the presynaptic terminal, therefore NT release decreases.

-allowing Ca to regenerate resets the graph
Why are granule cell EPSP's larger after tetanus than it is before tetanus?
-because repetitive stimuli from tetanus knocks Mg out of the NMDA receptor in the hippocampus, allowing more NT in
What is the Ideal Gas Law?
What is co-transport?
-when a protein moves 2 ions at the same time
-symport: same direction
-antiport: opposite direction
How is light phototransduced into the activity of rod and cone photoreceptors? 3 parts.
1)light activates rhodopsin photopigment

2)activated rhodopsin decreases the concentration of cGMP in the photoreceptor cytoplasm

3)the decrease in cGMP closes ion channels, decreasing Na influx and leading to hyperpolarization of the photoreceptor
What is rhodopsin?
-a photopigment conjugate of 2 parts:
1)Retinal (Vit A)
2)Opsin (a protein)

-rhodopsin is activated by light which in turn leads to conformational changes in the whole molecule

*Unstimulated: 11-cis conformation
*Stimulated: all trans conformation. When stimulated, causes an enzymatic degredation of cGMP to 5'-GMP, therefor [cGMP] decreases, Na channels close and it hyperpolarizes.
According to the text, what 4 steps are involved in phototransduction?
1)Rhodopsin molecules in the disc membrane absorb light and are activated

2)The activated rhodopsin stimuluates a G protein which activates a cGMP phophodiesterase

3)The phophodiesterase catalzyes the breakdown of cGMP to 5'-GMP

4)As [cGMP] decreases, cGMP detaches from the Na channels which will now close causing hyperpolarization. Graded potentials
Define electrotonic conduction.
-the very rapid passive spread of an electrical potential from one region to another basically due to attration of opposite charges
Define recruitment
-increased AP's because more nerve fibers are activated
dfine ismoteric contraction (prelab)
-length of muscle is constant, force of contraction varies
define isotoni contraction
-force of contraction is constant but the muscle is llowed to shorten
define rheobase
-represents the lowest possible stimulus, at long stimulus duration, whcih causes an AP
define chronaxie
-the stimulus duration, which occurs at 2x the reheobase stimulus
define active state
-the actural period of force fenerated by a sarcomere
define series elastic element
-the non contracting components of a muscle that are stretched during the initial shortening of a sarcomere; includes a variety of tissues
define the labelled line principle.
-sensory receptors encode the modality or quality of a sensory stimulus by having different sensory receptos respond to different stimuli, so that the CNS can decode the stimulus by monitoring which axons (lines) produce AP's
What is a rhabdom?
-the elongated zone of photosensitive microvilli in the ommatidium
How is phototransduction in arthropods different than phototransduction in vertebrates?
-in arthropods, photoreceptors are depolarized by light. Increases Na permeability.

-in vertebrates, photoreceptors are hyperpolarized by light. Decreasing Na permeability
What are Renshaw cells and reverberating circuits?
**Examples of complex loops**
-Renshaw Cells can cause an inhibitory effect, preventing tetanic type contraction(-'ve feedback)

-Reverberating Circuit keeps loop going, may be good for memory(+'ve feedback)
Why are neural circuits complex and varied?
1)convergence & divergence
-allows signals to be sent to multiple levels
-synapses may be inhibitory or excitatory
-response of receiving all info depends on relative # of eachother

-tons of NT's
-NT's can be colocalized
-each NT can have >1 receptor
-some NT's may cross react with related receptors
-#'s of receptors on a cell may be modified

3)Feed back loops
-Renshaw Cells can cause an inhibitory effect, preventing tetanic type contraction(-'ve feedback)
-Reverberating Circuit keeps loop going, may be good for memory(+'ve feedback)

-summation results from the addition of graded potentials in the dendrites
-may be temporal summation
-may be spatial summation (ie:convergence)
-combines effect of EPSP's and IPSP's

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