RMC Assignment

8/2/2019 RMC Assignment

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ASSIGNMENT

OF

PHYSIOLOGY

SUBMITTED BY:

SAFA

ROLL NO: 062

BATCH-B (3)

1stYEAR MBBS


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QUESTION# 1:

Define the following.PHYSIOLOGY:

Physiology explains the physical and chemical factors that are responsible for the origin,

development and progression of life.

OR

Physiology is thescienceof thefunction of living systems. This includes how organisms, organ

systems,organs,cells, and bio-molecules carry out the chemical or physical functions that exist in aliving system.

CELL:

The cell is the basic structural and functional unit of all known livingorganisms. It is the smallest

unit of life that is classified as a living thing, and is often called the building block of life

Types of cell

PROKARYOTES EUKARYOTES

BASIC FUNCTION OF CELL:

DIGESTION: Of food substances by lysosomes INGESTION: By diffusion, facilated diffusion, active transport and endocytosis SYNTHESIS: Of proteins, lipids, carbohydrates to form various enzymes and harmones. ENERGY PRODUCTION: In mitochondria. MOVEMENT: By amoeboid movement and ciliary movement. REPRODUCTION: Through genes.
http://en.wikipedia.org/wiki/Sciencehttp://en.wikipedia.org/wiki/Sciencehttp://en.wikipedia.org/wiki/Sciencehttp://en.wikipedia.org/wiki/Organshttp://en.wikipedia.org/wiki/Organshttp://en.wikipedia.org/wiki/Organshttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Organshttp://en.wikipedia.org/wiki/Science


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QUESTION#2

WRITE BRIEFLY ON:

Internal environment. Homeostasis. Feedback control mechanism with example. How feedback can be useful.ANSWER:

a) INTERNAL ENVIRONMENT: Definition: Internal environment is defined as the environment in which the cell actually

lives i.e. the extra cellular fluid. Extra cellular fluid is also called milieu interieur.

Explanation:The fluid outside the cell is called extracellular fluid. It is one third of the fluid present in the body. The

extracellular fluid maintains the ions and nutrient needed by the cells. Hence extracellular fluid(ECF)

is also called internal environment

COMPOSITION OF ECF: Large amount of NaCl Bicarbonate ions Nutrients for cells such as

Oxygen Glucose Fatty acids Amino acid

Carbon dioxide And other cellular waste.


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b) HOMEOSTASIS:Definition:

Homeostasis is defined as maintaining a constant or nearly constant internal condition.

Essentially all organs and tissues of the body perform function that help maintain these

relatively constant condition.For example, the lungs provide oxygen to the extracellular fluid to replenish the oxygen used

by the cell, the kidneys maintain constant ion concentrations and the gastrointestinal system

provides nutrients, hence all these systems contribute to the homeostasis.

It is essential that the physical and chemical processes of the body are controlled. Homeostasis

is the maintenance of the stable internal environment by regulation of these processes within

acceptable limits.

Homeostasis is maintained by the FEEDBACK CONTROL MECHANISM which usually involves

control by a combination of positive and negative feedback

c) FEEDBACK CONTROL MECHANISMFeedback control mechanism is defined as response to any change in the internal environment

Feedback control mechanisms are of two types:

Positive feedback Negative feedback

i. POSITIVE FEEDBACK MECHANISM:In positive feedback the response is in the direction of the initial stimulus.In the positive feedback the changed in the internal environment is increased in the direction

of the initial stimulus. Positive feedback can sometimes cause vicious cycle and death.

Positive feedback can sometimes be useful:

Blood clotting is an example of a valuable use of positive feedback. Childbirth is another instance in which positive feedback plays a valuable role. Positive feedback mechanism is used for the transmission of the nerve signals .

ii. NEGATIVE FEEDBACK MECHANISM:In negative feedback mechanism the response is in the opposite direction of the initial

stimulus.Most of the control system of the body act by negative feedback mechanism.

EXAMPLE:

Blood pressure is controlled by the negative feedback mechanism. Glucose level in the blood is controlled by the negative feedback mechanism. Carbon dioxide and oxygen concentration is maintained by the negative feedback. Thermoregulation Osmoregulation. Etc.


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For the survival of the cell constant or nearly constant internal environment is needed any

change in the internal environment can affect the cell adversely. Therefore, for the

maintenance of the constant internal condition feedback mechanism is needed.

QUESTION#3:

A. NAME THE ORGANELLES PRESENT IN THE HUMAN CELL.B. WHAT FUNCTION EACH ORGANELLE PERFORMS?C. WHAT IS PHAGOCYTOSIS AND PINOCYTOSIS?

ANSWER:

A. Organelles:i. Endoplasmic Reticulum

ii. Golgi Apparatusiii. Lysosomesiv. Peroxisomesv.

Mitochondria

vi. Cytoskeletonvii. Nucleus

viii. Secretory vesiclesix. Ribosomes

B. FUNCTIONS:

I. Endoplasmic Reticulum: Granular ER synthesizes proteins. Agranular ER synthesizes lipids. Agarnular ER also helps in enzymatic processes i.e. produces

enzymes for glycogen breakdown and enzyme to detoxify

harmful substances.

II. Golgi apparatus: Golgi apparatus modify or further process the substances

synthesizes by ER to form lysosomes, secretory vesicles,etc.


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III. Lysosomes: For digestion of food stuff contains hydrolytic enzymes. For destruction of harmful substances contain lysozymes and

lysoferrin etc.

IV. Peroxisomes:Contains oxidases that causes formation of hydrogen per oxide which

oxidizes poison and toxins into non harmful substances.

V. Mitochondria: Produces energy ATP via oxidative phosphorylation.

VI. Microfilaments and microtubules: Form cytoskeleton for the physical structure of the cell. Form cilia of the ciliated epithelium. Form flagella of sperm. Form centriole and mitotic spindles.

VII. Nucleus Transmits hereditary characters. Site for synthesis of the messenger RNA Controls functions and characteristics of the cell. Controls cell division.
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VIII. Secretory vesicles Store substances formed by cell

IX. Ribosomes Synthesizes proteins.

C. PHAGOCYTOSIS:

It is defined as the ingestion of the large particle such as bacteria or small degenerating tissues by

phagocytic cells.

PROCESS:

1) Phagocytosis is initiated by binding of the polysaccharides substances to a phagocyte (WBC)2) The cell membrane receptor of phagocyte recognizes this complex and attaches to it.3) The edges of the membrane around the points of the attachment evaginate outward to form a

pocket.

4) Actin and other contractile fibrils around the engulfed particle contract and close the pocketwith the particle inside.

5) This phagocytic vesicle is then pinched off and then floats out in the cell to be destroyed by thelysosome.

D. PINOCYTOSIS:It is defined as the ingestion of extremely small particle with some extracellular fluid.

PROCESS:

1) Substances to be ingested usually attaches to the on the surface of the cell membrane, thesereceptors are concentrated in the form of the small pockets called COATED PITS.
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2) Once the protein molecule has bound with receptors, the actin myosin present beneath the cellmembrane contract so that the entire pit invaginates inwards.

3) Immediately the boarders of the pit closes and it breaks away from the surface of the cell,forming a pinocytic vesicle. This process requires ATP.

QUESTION#4

Write short notes on

A. Genetic codeB. TranscriptionC. TranslationD. Messenger RNAE. ApoptosisF. DNA&RNA

ANSWER:

A. GENETIC CODE:The genetic code consists of successive triplets of bases, that is each three successive base is a

code word .

The successive triplets eventually control the sequence of the amino acids in a protein moleculethat is to be synthesized in the cell. The importance of the DNA lies in its ability to control the

formation of the protein in the cell. It does this by the means of the genetic code.

B. TRANSCRIPTION:Transcription is the process of creating a complementary RNA copy of a sequence of DNA.

During transcription, a DNA sequence is read by RNA polymerase, which produces a

complementary, antiparallel RNA strand. Transcription has three main stages 1) initiation, 2)

Elongation, 3) Termination.

The process of the transcription can described as follows:

1.RNA Polymerase moves the transcription bubble, a stretch of unpaired nucleotides, by

breaking the hydrogen bonds between complementary nucleotides.

2.RNA Polymerase adds matching RNA nucleotides that are paired with complementary DNA

bases.

3.RNA sugar-phosphate backbone forms with assistance from RNA polymerase.

4.Hydrogen bonds of the untwisted RNA+DNA helix break, freeing the newly synthesized RNA

strand.


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5.If the cell has a nucleus, the RNA is further processed (addition of a 3' poly-A tail and a 5'

cap) and exits through to the cytoplasm through the nuclear pore complex.

C. TRANSATION:The synthesis of proteins is known as translation. Translation occurs in the cytoplasm, wherethe ribosomes are located. Ribosomes are made of a small and large subunit that surrounds

the mRNA. In translation, messenger RNA (mRNA) is decoded to produce a specific polypeptide

according to the rules specified by the tri nucleotide genetic code. This uses an mRNA sequence

as a template to guide the synthesis of a chain of amino acids that form a protein. Translation

proceeds in four phases: activation, initiation, elongation, and termination (all describing the

growth of the amino acid chain, or polypeptide that is the product of translation).

D. MESSENGER RNA:A molecule of RNA that serves as a template for protein synthesis. mRNA is transcribed from a gene

and then translated by ribosomes in order to manufacture a protein. Each set of three bases, called

codons, specifies a certain protein in the sequence of amino acids that comprise the protein. The

sequence of a strand of mRNA is based on the sequence of a complementary strand of DNA

.

E. APOPTOSIS:It is defined as programmed cell death. A form of cell death in which a programmed sequence of events

leads to the elimination of cells without releasing harmful substances into the surrounding area.Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells,

unnecessary cells, and unhealthy cells. The human body replaces perhaps a million cells a second

F. DNA:DNA is defined as the nucleic acid that carries the genetic information in the cell and is capable of

self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a

double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or

cytosine and guanine. The sequence of nucleotides determines individual hereditary

characteristics.The DNA molecule consists of two polynucleotide chains in the form of a double helix,

containing phosphate and the sugar deoxyribose and linked by hydrogen bonds between thecomplementary bases adenine and thymine or cytosine and guanine. DNA is self-replicating, plays a

central role in protein synthesis, and is responsible for the transmission of hereditary characteristics

from parents to offspring.


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G. RNA (Ribonucleic acid)Ribonucleic acid (RNA) is a nucleic acid molecule similar to DNA but containing ribose rather than

deoxyribose. RNA is single stranded and contains uracil instead of thmine. RNA is formed upon a DNA

template. They play crucial roles in protein synthesis and other cell activities:

There are several classes of RNA molecules.

Messenger RNA (mRNA) is a type of RNA that reflects the exact nucleoside sequence of the genetically

active DNA. mRNA carries the "message" of the DNA to the cytoplasm of cells where protein is made in

amino acid sequences specified by the mRNA.

Transfer RNA (tRNA) is a short-chain type of RNA present in cells. There are 20 varieties of tRNA. Each

variety combines with a specific amino acid and carries it along (transfers it), leading to the formation

of protein with a specific amino acid arrangement dictated by DNA.

Ribosomal RNA (rRNA) is a component of ribosomes. Ribosomal RNA functions as a nonspecific site for

making polypeptides

QUESTION #5

Describe the mechanism of the active and passive transport across the cell membrane?

ANSWER:

Passive transport mechanisms Active Transport mechanisms
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Simple protein channels Gated channels

o primary active transporto secondary active transport

endocytosiso phagocytosiso pinocytosis

exocytosis

A. Passive transport mechanism:a. Diffusion:

It is defined as the movement of the molecules for the region of the higher concentration to the

region of the lower concentration due to the kinetic motion of the molecules.

Diffusion is of two types:

Simple diffusion(does not need protein carrier) Facilitated diffusion(carrier mediated)

b. Osmosis:Movement of the solvent particle from the region of the higher to the region of the lower

concentration through a semi permeable membrane.

B. Active transport mechanism:Active transport is the movement of molecules or ions across the cell membraneagainst the concentration gradient, using energy (ATP).

Two types:

Primary active transport Secondary active transporta) Primary active transport:

In this type of active transport energy is used, which is directly derived from

the breakdown of ATP

Example:

Sodium potassium pump Calcium pump

b) Secondary active transport:In this type of active transport there is indirect use of energy

Two types


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i. Co- transport (symport): molecules or ions move in same direction e.g.Na-glucose co-transport.

ii. Counter transport (antiport): molecules or ions move in oppositedirection. E.g. Na-Ca counter transport

QUESTION#6:

(A). What is facilitated diffusion?

ANSWER:

Facilitated diffusion is the movement or ions, through cell membrane towards concentration

gradient in combination with a carrier protein and without utilization of energy. Facilitated

diffusion is also called carrier mediated diffusion.

Example:

Transport of glucose and amino acid.

Facilitated diffusion takes place through:

Simple Proteins channels(watery pathways inside the protein molecule)

Gated protein channels(protein channels are gated providing a means for controlling thepermeability of channels)

Types of gated protein channels:

a. voltage gated channels(opening and closing of the gates respond to theelectrical potential across the cell membrane)

b. ligand gated channels (opening or closing of gates due the binding ofanother molecule with the protein channel)

(B). What factors affect diffusion?

ANSWER:

Factors affecting diffusion:

1. Permeability of membrane(greater the permeability greater the diffusion)2. Temperature (greater the temperature greater the more will be diffusion)3. Concentration difference(greater the conc. Difference, greater the diffusion)4. Electrical potential(+ve attracts the ve charge and vice versa)5. Pressure difference(increased movement of molecules occurs from high

pressure side towards low pressure side)

QUESTION#7:

Write brief note on

a) Energetics of active transportb) Diffusion of water and lipid insoluble molecules through protein channelsc) Na-K pump & its importance

ANSWER:

A) Energetics of active transport:


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The amount of energy required to transport a substance actively through a membrane is determined

by how much the substances is concentrated during transport. compared with energy required to

concentrate a substance for example from 10 folds to 100 folds is doubled and for 1000 folds requires

three times as much energy. In other words, the energy required is proportional to the logarithm of

degree that substance is concentrated, expressed by the formula

Energy (in calories per osmoles)=1400 log

B) Diffusion of water and lipid insoluble molecules through protein channels:Water is lipid insoluble, but it penetrates the cell membrane very rapidly, the reason

for this diffusion is its small size and high kinetic motion.

Protein channels and pores have tubular pathways from the extracellular fluid to the

intracellular fluid, therefore substances can pass through the pores and channels by

diffusion directly. Pores are composed of the integral cell membrane protein that formopen tubes through the membrane and are always open. However the diameter of the

pore and its electrical charge provide selectivity that permits only certain molecules to

pass through.

Example:

Aquaporins or water channels permits rapid passage of water through cell membrane

but exclude other molecules. The pores are very small thus permits passage of any

hydrated ions. While some protein channels and pores permits the movement of other

Substances. Example:

Potassium leak channels permits the movement of the potassium only.

Likewise sodium and calcium have their own protein channels

C) Na-K pump and its importance:It is the most important example of active transport. The pump transports

3Na+ ions out of the cell and 2K+ ions at the same time into the cell. The carrier protein of Na+_K+

pump is a globular protein having a larger and smaller protein. The larger protein part has got

three specific features i.e:

a) It has three receptors sites for Na+ ions on inside.b) Has two receptor site for K+ ions on outside.c) ATPase activity on inside portion.

IMPORTANCE:

1) It is an electrogenic pump. Since Na+-K+ pump sends 3 Na ions outside and 2K ions inside so itcreates an electrical potential across cell membrane.

2) Controlling cell volume, without function of this pump, most cells of the body would swell untilthey brust.

3) Maintance concentration gradient of Na&K


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QUESTION#8:

A) Define resting membrane potential?B) How is it created.C) Describe the changes occurring during the propagation of action potential in a nerve fibre.

ANSWER:

The electrical potential across the cell membrane while it is not transmitting signals or isin resting state it is called resting membrane potential(RMP). It is -90mv inside the cell.

Contribution of k+ diffusion in the RMP:There are protein channels in the cell membrane though which k+ leaks to outside

normally because inside k is 140meq/L while outside it is only 4meq/L. this leaks the k

outside the cell until the membrane potential become 94mv inside, this potential is also

called the Nernst potential for K because at this value further outflux of the K stops.

Contribution of Na diffusion in RMP:Sodium concentration outside is 142meq/L and inside is 10meq/L, so Na diffuses inside the cell until

the potential become +61mv inside. At this potential further influx of the Na stops this is known as the

Nernst potential for the Na.

Contribution of Na-K pump to RMP:Na-K pump is electrogenic pump, it takes 3 Na outside and 2K inside thus creating a negativity of -

4mv.

TOTAL RMP:

K diffusion contributes = -94mv Na diffusion contributes= +8mv Na-K pump contributes= -4mv Net RMP=-90mv
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Changes occurring in the nerve fiber during action potential: Na gated channel opens and influx of sodium takes place Due to the influx of sodium, inside the nerve fiber the positivity increases This increase in the positivity causes the other Na gated channels to open. When the potential value reaches the threshold action potential takes place. The depolarization takes place ie. Inside the membrane positivity increases The depolarization propagates along the nerve fibre At about +35mv the Na gated channels closes and the depolarization stops. At this state K channels open and causes the efflux of K , this state is known as the

repolarization

QUESTION#9

Write short note on

Interstitial fluid

Edema Excitation Contracting Coupling

ANSWER:

1) Interstitial fluidInterstitial fluid (or tissue fluid) is a solution that bathes and surrounds the cells of multicellular

animals. It is the main component of the extracellular fluid, which also includes plasma and

transcellular fluid. The interstitial fluid is found in the interstitial spaces, also known as the tissue

spaces.The fluid found in the intercellular spaces composed of water, amino acids, sugars, fatty acids,

coenzymes, hormones, neurotransmitters, salts, and cellular products. It bathes and surrounds the

cells of the body, and provides a means of delivering materials to the cells, intercellular

communication, and removal of metabolic waste. The interstitial fluid is the main component of the

extracellular fluid (other components are plasma and transcellular fluid).

2) EdemaEdema is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body

that produces swelling. Generally, the amount of interstitial fluid is determined by the balance of fluid

homeostasis, and increased secretion of fluid into the interstitial or impaired removal of this fluid may

cause edema

3) Excitation, Contracting and CouplingThis is the name given to the chain of processes coupling excitation of a muscle by the arrival of a

nervous impulse at the motor end plate to the contraction of the filaments of the sarcomere. The

crucial link is the release of calcium from the sarcoplasmic reticulum and the analogy is often drawn

between this and stimulus secretion coupling, that also involves calcium release into the cytoplasm.


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QUESTION#10:

Describe briefly

Saltotry conductionsaltatory conduction is the propagation of action potentials along myelinated axons from one node ofRanvier to the next node, increasing the conduction velocity of action potentials without needing to

increase the diameter of an axon.Because the cytoplasm of the axon is electrically conductive, and

because the myelin inhibits charge leakage through the membrane, depolarization at one node of

Ranvier is sufficient to elevate the voltage at a neighboring node. Thus, the voltage at the first node of

Ranvier extends spatially to the next node of Ranvier. At each successive node, the membrane potential

of the axon is thereby brought to the threshold potential to initiate an action potential. Ions need only

to cross the axon membrane to propagate the action potential at the nodes, but not anywhere under

the myelin along the axon. Thus in myelinated axons, action potentials do not propagate continuously

as waves, but instead recur at successive nodes

Action potential and propagationAction potential is defined as the rapid change in the resting membrane potential. It has the following

two stages:

Resting stage Depolarization stage Repolarization stage

Resting stage:

In resting stage the membrane is said to be polarized because of its large negative potential.

Depolarization stage:

In this stage membrane becomes permeable to Na, allowing large amount of Na influx. Because of this

normal RMP of -90mv is lost. Membrane potential approaches zero mv and then overshoot to +35mv

for complete depolarization.

Repolarization:

In this stage membrane potential changes from +35mv back to -90mv(RMP)


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Plateau in action potentialIn some instances, the excited membrane dose not repolarize immediately after depolarization;instead

the potential remains on plateau near the peak of the spike potential for milliseconds, and only then

repolarization begin. This type of action potential occurs in the heart muscles fibres, where the plateaulasts for as long as 0.2 to 0.3 second and causes contraction of heart muscles for this same long period.

Causes:

1) Voltage activated calcium-sodium channels which are slow to open andtherefore are called slow channels.

2) Na channel are the fast channels which opens and closes fast, Opening offast channels causes spike portion of the action potential whereas the

prolonged opening of the slow calcium-sodium channels mainly allows calcium

ions to enter the fiber, which is largely responsible for the plateau portion of

the action potential

OsmosisOsmosis is the passage of water from the region of high water concentration through a semi

permeable membrane to a region of low water concentration.

The semipermeable membrane must be permeable to the solvent, but not to the solute,

resulting in a pressure gradient across the membrane. Osmosis is a natural phenomenon.

However, it can be artificially opposed by increasing the pressure in the section of high solute
http://www.google.com.pk/imgres?q=PICTURE+OF+plateau+in+action+potential&hl=en&rlz=1R2ADFA_enPK447&biw=1366&bih=561&tbm=isch&tbnid=SvkmVpVs72sXqM:&imgrefurl=http://www.nursing-lectures.com/2011/04/cardiovascular-physiology-lecture-notes.html&docid=PjqVigWB785A_M&imgurl=http://lh6.ggpht.com/_TytbGNcfT0Q/Tas3d3jbAPI/AAAAAAAAEQ0/vgTLRN6RCTk/clip_image002_thumb[2].jpg&w=419&h=320&ei=BEMAT63nJoiGhQeM9IivAQ&zoom=1&iact=rc&dur=2&sig=104811670450287100261&page=5&tbnh=161&tbnw=211&start=58&ndsp=11&ved=1t:429,r:1,s:58&tx=143&ty=46http://www.google.com.pk/imgres?q=PICTURE+OF+action+potential&hl=en&rlz=1R2ADFA_enPK447&biw=1366&bih=561&tbm=isch&tbnid=fQeHYmu5Oy6r8M:&imgrefurl=http://www.answers.com/topic/action-potential&docid=OSyyY-CRnaz3cM&imgurl=http://content.answcdn.com/main/content/img/oxford/Oxford_Sports/0199210896.action-potential.1.jpg&w=525&h=392&ei=8kEAT4b0N4inhAesxYiWDA&zoom=1http://www.google.com.pk/imgres?q=PICTURE+OF+plateau+in+action+potential&hl=en&rlz=1R2ADFA_enPK447&biw=1366&bih=561&tbm=isch&tbnid=SvkmVpVs72sXqM:&imgrefurl=http://www.nursing-lectures.com/2011/04/cardiovascular-physiology-lecture-notes.html&docid=PjqVigWB785A_M&imgurl=http://lh6.ggpht.com/_TytbGNcfT0Q/Tas3d3jbAPI/AAAAAAAAEQ0/vgTLRN6RCTk/clip_image002_thumb[2].jpg&w=419&h=320&ei=BEMAT63nJoiGhQeM9IivAQ&zoom=1&iact=rc&dur=2&sig=104811670450287100261&page=5&tbnh=161&tbnw=211&start=58&ndsp=11&ved=1t:429,r:1,s:58&tx=143&ty=46http://www.google.com.pk/imgres?q=PICTURE+OF+action+potential&hl=en&rlz=1R2ADFA_enPK447&biw=1366&bih=561&tbm=isch&tbnid=fQeHYmu5Oy6r8M:&imgrefurl=http://www.answers.com/topic/action-potential&docid=OSyyY-CRnaz3cM&imgurl=http://content.answcdn.com/main/content/img/oxford/Oxford_Sports/0199210896.action-potential.1.jpg&w=525&h=392&ei=8kEAT4b0N4inhAesxYiWDA&zoom=1


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concentration with respect to that in the low solute concentration. The force per unit area

required to prevent the passage of solvent through a selectively-permeable membrane and

into a solution of greater concentration is equivalent to the turgor pressure. Osmotic pressure

is a colligative property, meaning that the property depends on the concentration of the solute

but not on its identity.


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