Pengantar Biolistrik Dan Sinaps

8/12/2019 Pengantar Biolistrik Dan Sinaps

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Pengantar Biolistrik dan Sinaps

M. Djauhari Widjajakusumah

Fakultas Kedokteran Universitas Indonesia


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Figure 41

Chemical compositions of extracellular

and intracellular fluids.


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Figure 42

Transport pathways through the cell membrane, and the basic mechanisms of

transport. Guyton and Hall: Textbook of Medical Physiology 11thEd, 2006


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Fig. 10.9. Facilitative transport. Although the molecule being transported must bind to the

protein transporter,the mechanism is passive diffusion, and the molecule moves from a

region of high concentration to one of low concentration.Passive refers to the lack of an

energy requirement for the transport.

Marks Basic Medical Biochemistry: A Clinical Approach, 2nd Edition, 2005


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Guyton and Hall: Textbook of Medical Physiology 11thEd, 2006


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7/80Guyton and Hall: Textbook of Medical Physiology 11thEd, 2006


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Guyton and Hall: Textbook of

Medical Physiology 11thEd,

2006


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Medical Physiology 11thEd, 2006


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Medical Physiology 11thEd, 2006


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Forces Acting on Ions and Their Equilibrium Potentials

The magnitude of the equilibrium potential for Cl(ECl), K+ (EK) and Na+

(ENa) can be calculated from the Nernst equation, as follows:

ENa = 61.5log[Na+ o] at 37C

[Na+ i]

= - 70 mv

= - 90 mv

= + 60 mv

WF Ganong: Review of Medical Physiology 22nded,

2005


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Figure 56

Typical action potential recorded by the

method shown in the upper panel of the

figure.


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Guyton and Hall: Textbook of Medical

Physiology 11thEd, 2006


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Changes in Na+ and K+ conductance during the action potential in giant squid axon. The dashed

line represents the action potential superimposed on the same time coordinate. Note that the initial

electrotonic depolarization initiates the change in Na+ conductance, which in turn adds to the

depolarization. (Modified from Hodgkin AL: Ionic movements and electrical activity in giant nervefibers. Proc R Soc Lond Ser B 1958;143:1.)


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Overshoot


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Figure 2-10 A sensory neuron transforms a physical stimulus (a stretch) into electrical

activity in the cell. Each of the neuron's four signaling components produces a characteristicsi nal.

Kandel: Principle

of Neural

Science 4thed,

2000


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Figure 213.

Compound action potential.The drawing shows the record obtained with

recording electrodes at various distances from the stimulating electrodes

along a mixed nerve.


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Receptors

The term receptorrefers to

sensory receptors

proteins that bind neurotransmitters, hormones, and othersubstances with great affinity and specificity as a first step ininitiating specific physiologic responses

The sensory receptor

Part of a neuron

A specialized cell (nonneural cells

sense organ) Generates action potentials in neurons.

The forms of energy converted by the receptors includemechanical (touch-pressure), thermal (degrees of warmth),electromagnetic (light), and chemical energy (odor, taste, and O2content of blood).

Adapted to respond to one particular form of energy at a muchlower threshold than other receptors respond to this form ofenergyadequate stimulus.(e.g. light for the rods and conesin the eye)

Receptors respond to forms of energy other than their adequatestimuli (nonspecific responses), but the threshold for these ismuch higher.


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Ganong: Review of Med Physiol 22nded , 2005

blocked cutdegenerates

no action potential

responses

dissapeared

connective tissue capsule removed

responses persisted, loss

of adaptation

graded potentials

action potential


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Sensory Receptors, Neuronal

Circuits for Processing Information

Types of Sensory Receptors and the Sensory Stimuli They

Detect

Five basic types of sensory receptors:

(1) mechanoreceptors,which detect mechanical compression or

stretching of the receptor or of tissues adjacent to the receptor

(2) thermoreceptors,which detect changes in temperature, somereceptors detecting cold and others warmth

(3) nociceptors(pain receptors), which detect damage occurring in thetissues, whether physical damage or chemical damage

(4) electrom agnet ic recepto rs,which detect light on the retina of the

eye

(5) chemoreceptors,which detect taste in the mouth, smell in the nose,

oxygen level in the arterial blood, osmolality of the body

fluids, carbon dioxide concentration, and perhaps other factors that

make

up the chemistry of the body.


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Classification of Sensory Receptors

I. Mechanoreceptors

Skin tactile sensibilities (epidermis and dermis)

Free nerve endings

Expanded tip endings

Merkels discs

Plus several other variantsSpray endings

Ruffinis endings

Encapsulated endings

Meissners corpusclesKrauses corpuscles

Hair end-organs


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I. Mechanoreceptors

Deep tissue sensibilities

Free nerve endings

Expanded tip endings

Spray endings

Ruffinis endings

Encapsulated endings

Pacinian corpuscles

Plus a few other variants

Muscle endingsMuscle spindles

Golgi tendon receptors


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I. Mechanoreceptors

Hearing

Sound receptors of cochlea

Equilibrium

Vestibular receptors

Arterial pressureBaroreceptors of carotid sinuses and aorta


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II. Thermoreceptors

Cold

Cold receptors

Warmth

Warm receptors

III. Nociceptors

Pain

Free nerve endings

IV. Electromagnetic receptors

Vision

Rods

Cones


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Generator Potentials

Generator potentialor receptor potentialis a non-propagateddepolarizing potentialwhen stimulus is applied to a receptorthe

receptor converts energy into an electrical response As the stimulus is increased, the magnitude of the receptor potential

increasesthe magnitude is proportionate to the intensity ofthe stimulus.

The generator potential depolarizes the sensory nerve at the firstnode of Ranvier, once the firing level is reached, an action potentialis producedthe node of Ranvier converts the gradedresponse of the receptor into action potentials

As the pressure is further increased,the generator potentialbecomes even larger and the sensory nerve fires repetitively, thefrequency of which is proportionate to the magnitude of the

applied stimuli. It continues to fire as long as the generator potential is large enough

to bring the membrane potential of the node to the firing level.



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Kandel: Principle of Neural Science 4thed, 2000


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Adaptation

When a maintained stimulus of constant strength is applied toa receptor, the frequency of the action potentials in its sensorynerve declines over time adaptation or desensitization

The degree to which adaptation occurs varies from one senseto another

rapidly adapting (phasic) receptors (light and touch) slowly adapting (tonic) receptors.

slow adaptation of muscle spindle input is needed tomaintain posture.

input from nociceptors provides a warning that wouldlose its value if it adapted and disappeared.



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Adaptation. The height of the curve in each case indicates the frequency of the discharge in

afferent nerve fibers at various times after beginning sustained stimulation. (Reproduced,

with permission, from Adrian ED: Basis of Sensation. Christophers, 1928.)


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Receptors That Bind ChemicalMessengers

Receptors That Bind Chemical


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Receptors That Bind Chemical

Messengers


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Vander et al.: Human Physiology: The

Mechanism of Body Function, 8th Ed 2001


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Guyton 11thed 2006


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Vander et al.: Human

Physiology: The

Mechanism of Body

Function, 8th Ed 2001


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Basic Functions of Synapses

Figure 451


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Figure 45 1

Structure of a large neuron in the brain, showing

its important functional parts. (Redrawn from

Guyton AC: Basic Neuroscience:

Anatomy and Physiology.

Philadelphia: WB Saunders Co, 1987.)


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Figure 4510

Excitatory postsynaptic potentials, showing that simultaneous firing of only a few synapses

will not cause sufficient summated potential to elicit an action potential, but that simultaneous

firing of many synapses will raise the summated potential to threshold for excitation and

cause a superimposed action potential.


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Pengantar Biolistrik Dan Sinaps

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