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Y1B2 (PPMIP & PPP) πŸ“— > Physiology 🫁 > Flashcards

Physiology 🫁 Flashcards

1
Q

Organization of the human body

A

οƒœ The human body is made up of different systems e.g. digestive system.
οƒœ Each system formed of many organs that are formed of many tissues with complementary functions.
οƒœ Each tissue formed of millions of cells.
οƒœ The cell is the basic unit of structure and function in the body.

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2
Q

What are cells considered as?

A

Cells are the basic unit of structure and function

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3
Q

What does plasma or cell membrane allow?

A

Allow Selective communication between IC & EC compartments.

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4
Q

What are the eukaryotic cells formed from?

A

-plasma or cell membrane: Allow Selective communication between IC & EC compartments.

-organelles:
οƒœ Cytoplasm.
οƒœ Nucleus.
οƒœ Ribosomes: protein synthesis.
οƒœ Mitochondria: energy production.

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5
Q

What is the definition of body fluids?

A

Solutions of water containing:
1. Organic molecules (carbon-containing molecules such as carbohydrates, lipids, proteins, and nucleic acids).
2. Inorganic molecules.
3. Ions (atoms with a net charge).

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6
Q

What is the value (amount) of body fluids?

A

65% i.e. 40-42 liters in an adult weighing 70 Kg.

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7
Q

What are the compartments of body fluids?

A

ICF:
The fluid inside the cell.
2/3 of total body fluids.
25-28 liters.

ECF:
Fluid Outside cell.
1/3 of total body fluids.
14-15 liters.

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8
Q

What does ECF consist of?

A

Plasma: Inside blood vessels - 3 or 3.5 liters
Interstitial fluid: in spaces between cells - 10 or 12 liters
Trans-cellular fluid: in body cavities e.g. GIT & CSF - 1liter

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9
Q

What is the composition of body fluids?

A

 ECF contains large amounts of Na+, Cl-, and HCO3 ions, while ICF contains large amounts of K+, Mg2+, and HPO4 ions.

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10
Q

What are the molecules that are more within the cell?

A

K - proteins - Mg - HPO4

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11
Q

What are the molecules with a high ratio in the ECF?

A

Na - Cl - Ca - HCO3

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12
Q

What is the TBW in females, males, children, and elderly people respectively?

A

50% as their body contains more fat
60%
70% so water loss leads to rapid dehydration.
Down to 40-45%

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13
Q

What is the function of body water?

A
  1. It is required for all chemical reactions inside the body.
  2. It acts as a powerful solvent that dissolves various substances to make them accessible to the body. So, it acts as a vehicle that carries nutrients and gases to the body cells and removes wastes from them.
  3. It is important in the regulation of body temperature as water has a high latent heat of evaporation (each gram H2O needs 0.58 β—¦C to evaporate from the body).
  4. It moistens tissues such as the mouth, eyes, and nose, and lubricates joints.
  5. Digestive function: water shares in the formation of digestive secretions and the action of enzymes.
  6. Absorption: at the venous end of capillaries.
  7. Filtration: at the arterial end of capillaries.
  8. At the kidney: water helps filtration, reabsorption, and secretion.
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14
Q

What does the increase in fat do to the ratio of water?

A

the increasing of the percentage of fat in the body decreases the percentage of water

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15
Q

What is the amount of water input?

A

2400 ml/day.

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16
Q

What are the sources of water input?

A

 Exogenous water :
ingested in form of water or liquid→ 2200 ml/day.

 Endogenous water :
Synthesized as a result of metabolism β†’ 200 ml/day.

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17
Q

What is the water input controlled by?

A

Thirst sensation which caused by stimulation of the thirst center in the hypothalamus.

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18
Q

What is the amount of water output?

A

2400 ml/day.

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19
Q

What are the sources of water output?

A

 Urine β†’ 1500 ml.
 Insensible (vapor & perspiration)β†’ 700ml.
 Sweating β†’100 ml.
 Feces β†’ 100ml.

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20
Q

What controls the water output?

A

Adjusting urine volume by antidiuretic hormone (ADH) secreted from the posterior pituitary gland

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21
Q

What is homeostasis?

A

Mechanisms keeping the internal environment constant.

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22
Q

What is the importance of homeostasis?

A

This is very important as the cells lie in the internal environment, This Keeps the normal cellular functions as body water, temperature, blood glucose, ions, pH, and arterial blood pressure (ABP).

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23
Q

What are the mechanisms of homeostasis?

A

A. Negative feedback mechanisms: These mechanisms keep the internal environment constant because the response inhibits the stimulus

B. Positive feedback mechanisms: The response increases the stimulus

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24
Q

What are examples of negative feedback mechanisms?

A
  • Increased CO2 (stimulus) β†’ hyperventilation (response) β†’ washout of excess CO2 β†’ decreased CO2 to normal.
  • Increased arterial blood pressure (ABP) (stimulus) β†’ reflex VD and decreased heart rate (response) β†’ decreased arterial blood pressure back to normal
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25
Q

What are the examples of positive feedback?

A
  • Usually, +ve feedback disturbs homeostasis e.g. death cycles:

In heart failure β†’ decreased cardiac output (stimulus) β†’ decreased arterial blood pressure β†’ decreased coronary blood flow (response) β†’ more heart failure

  • Some positive feedback cycles are useful

e.g.
During delivery of baby, cervix dilatation (stimulus) β†’ ↑ uterine contractionsβ†’ descent of baby β†’more cervical dilatation β†’ more uterine contractions (response) β†’ more descent of baby, till complete labor.

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26
Q

What is the cell membrane?

A

Very thin elastic semi-permeable membrane (allowing some substances to pass through it and prevent others) that surrounds the cell.

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27
Q

What is the thickness of the cell membrane?

A

: 7-9nm (70 - 90 Ao = Angstrom = 10-10 of meter)

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28
Q

What is the function of the cell membrane?

A

Β«STM GRCΒ»

  1. Separates the cytoplasm from ECF.
  2. Maintains the cell’s internal environment.
  3. Transports of macromolecules into and out of the cell.
  4. Controls distribution of ions e.g. Na, K extracellular ICF, and ECF.
  5. Contains receptors for hormones and transmitter substances.
  6. Generates transmembrane membrane potentials.
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29
Q

What is the structure of the cell membrane?

A

Lipids: 42%
Proteins: 55%
Carbohydrates: 3%

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30
Q

Lipids in the cell membrane

A

-They form the basic structure of the membrane.

Include:
1. Phospholipids.
2. Cholesterol.
3. Glycolipids.

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31
Q

What are the types of proteins in the cell membrane?

A
  1. Integral or intrinsic proteins
  2. Peripheral or extrinsic proteins
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32
Q

What is the site of integral or intrinsic proteins?

A

β€’ Bind to the hydrophobic center of the lipid bilayer.

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33
Q

What are the types and functions of integral or intrinsic proteins?

A

i) Transmembrane proteins β†’ span the entire bilayer which acts as:
➒ Channels β†’ for the diffusion of small ions
➒ Carriers transport substances e.g. glucose
➒ Pumps actively transport ions
➒ Receptors initiate
intracellular reactions when activated.

ii) Present only on one side of the membrane: act as enzymes e.g. adenyl cyclase that forms cyclic AMP from ATP

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34
Q

What is the site of peripheral or extrinsic proteins?

A

Bind to hydrophilic polar heads of lipids or to integral proteins.

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35
Q

What are the types of peripheral or extrinsic proteins?

A

i) Peripheral proteins: bind to the intracellular surface of the membrane & contribute to the cytoskeleton.

ii) Peripheral proteins: bind to the extracellular surface of membrane & contribute to glycocalyx or cell coat.

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36
Q

What are the protein ion channels?

A

They are protein channels that allow the passage of ions e.g. Na+ ion through the cell membrane.

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37
Q

What are the types of protein ion channels?

A

1- leak ion channel
2- chemical-gated ion channels
3- voltage-gated ion channels

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38
Q

What is the definition of leak ion channels?

A

Channels that are always open

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39
Q

What are examples of leak ion channels?

A

K channels

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40
Q

What is the importance of the leak ion channel?

A

Resting membrane potential

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41
Q

What is the definition of chemical-gated ion channels?

A

Channels open when a chemical substance bind to its receptor

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42
Q

What are examples of chemical-gated ion channels?

A

K & Na channel at NMJ.

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43
Q

What is the importance of chemical-gated ion channels?

A

Graded membrane potential e.g. motor endplate potential

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44
Q

What is the definition of voltage-gated ion channels?

A

Channels open by changes in cell membrane potential

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45
Q

What are examples of voltage-gated ion channels?

A

Na & K channels

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46
Q

What is the importance of voltage-gated ion channels?

A

Action potential

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47
Q

What is the definition of diffusion?

A

Movement of substances across the cell membrane down its electrochemical gradient due to the continuous random motion of its particles.

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48
Q

What are the types of transporting across the cell membrane?

A
  • Diffusion
  • Active transport
  • vesicular transport
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49
Q

What are the types of diffusion?

A

Simple, facilitated, and osmosis.

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50
Q

What is the definition of simple diffusion?

A

Movement of substances across cell membrane down its electrochemical gradient by simple movement without the necessity of binding with carrier proteins.

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51
Q

What are the characters of the simple diffusion?

A
  1. It occurs down an electrochemical gradient.
  2. Passive i.e. no external energy is required.
  3. Not rate-limiting i.e. linear with concentration gradients.
  4. The diffusion process is not saturable.
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52
Q

What are the mechanisms of simple diffusion?

A

-Interstices of the lipid bilayer e.g. diffusion of O2, nitrogen, CO2, and alcohol.

-Watery proteins channels e.g. diffusion of ions

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53
Q

What is the definition of facilitated diffusion?

A

As simple diffusion but it needs the presence of carrier proteins.

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54
Q

What are the examples of facilitated diffusion?

A

Transport of glucose into the cells.

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55
Q

What is the definition of osmosis?

A

The passive flow of water across a semi-permeable membrane down a concentration gradient of water

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56
Q

What are examples of osmosis?

A

from high concentration of water to low concentration of water or low concentration of solute to high concentration of solute.

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57
Q

What are the Factors affecting Net Rate of Diffusion
(Fick’s Law)?

A

a. Concentration gradient for the solute (Cin - Cout in mmol/L)

b. Diffusion Coefficient (D) or permeability coefficient of the membrane

c. Membrane surface area (A in cm2).
- The rate of diffusion is directly proportional to these factors.

d. Membrane thickness (X in cm) or distance, the rate of diffusion is inversely proportional to the thickness of the membrane.

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58
Q

What is the definition of active transport?

A

Movement of substances across cell membranes against an electrochemical gradient.

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59
Q

What are the characters of active transport?

A
  1. Occurs against the electrochemical gradient
  2. Active i.e. energy is required.
  3. Requires presence of a transport carrier protein, so its rate is limited,
    saturable, and shows competition and stereospecificity
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60
Q

What are the types of active transport?

A

Primary and secondary.

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61
Q

Primary active transport

A

Use energy directly from ATP hydrolysis

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62
Q

What are examples of primary active transport?

A

Na-K Pump, Ca ATPase Pump , H-k Pump

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63
Q

Sodium-potassium pump (Na+-K+ ATPase) :

A

➒ Transports 3 Na+ from ICF to ECF & 2 K+ from ECF to ICF.

➒ This maintains low intracellular Na and high intracellular K.

➒ It utilizes about 40% - 50% of energy

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64
Q

Secondary active transport

A

Use energy generated by sodium gradient created by Na-K pump e.g. Na-Ca exchanger and Na-glucose cotransport

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65
Q

What is the definition of vesicular transport?

A

The mechanism by which the large-sized substances can cross the cell membranes.

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66
Q

What are the types of vesicular transport?

A
  • Endocytosis and exocytosis
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67
Q

What is the definition of endocytosis?

A

The extracellular material is trapped within vesicles that are formed by the invagination of the cell membrane and pushed inside the cell.

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68
Q

What are the types of endocytosis?

A

Phagocytosis: Endocytosis of bacteria & dead tissue.

Pinocytosis: Endocytosis of substances in solution e.g. proteins.

Receptor-mediated endocytosis: The material to be transported first binds to a receptor e.g: Iron and cholesterol

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69
Q

What is the definition of exocytosis?

A

the intracellular material is trapped within vesicles, then the vesicles fuse with the cell membrane and release their contents to the ECF.

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70
Q

What are the examples of exocytosis?

A

release of hormones, digestive enzymes, and synaptic transmitters

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71
Q

What is the origin of Sympathetic Supply to the Head and Neck?

A

LHCs of first and second thoracic segments

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72
Q

What is the relay of the LHCs of the first and second thoracic segments?

A

Superior cervical ganglion (SCG)

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73
Q

What are the parts affected by the sympathetic supply to the head and neck?

A

-Eye
-Salivary glands
-Skin
-Cerebral blood vessels

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74
Q

Effect of sympathetic supply to the eye

A

a. Contraction of dilator pupillae ms→ dilatation of pupil (mydriasis)

b. Contraction of smooth ms in eyelids (Tarsal ms) leading to elevation of upper and lowering of lower eyelids→ widening of palpberal fissure.

c. Contraction of Muller ́s ms (behind eyeball) β†’ exophthalmos.

d. Relaxation of ciliary msβ†’ ↓ convexity of the lensβ†’ helps the eye to see far objects.

e. Vasoconstriction (V.C.) of blood vessels of lacrimal glands and trophic secretion.

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75
Q

Effect of sympathetic supply to the salivary glands

A

a. Vasoconstriction (V.C.) of salivary gland blood vessels.

b. Trophic secretions: little, viscous, concentrated secretion; poor in water and rich in enzymes.

c. Contraction of myoepithelial cells surrounding salivary acini leading to squeezing of salivary secretion outside.

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76
Q

Effect of the sympathetic supply to the skin

A

a. V.C or vasodilatation (V.D.) of skin blood vessels, but VC is more powerful.

b. Hair erection due to contraction of piloerector muscle.

c. Sweatsecretion.

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77
Q

Effect of the sympathetic supply to cerebral blood vessels

A

Mild vasoconstriction (V.C.).

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78
Q

What is the definition of Horner’s syndrome?

A

It is a group of signs which result from interruption sympathetic to the head and neck.

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79
Q

What are the causes of Horner’s syndrome?

A

a. Lesion in T1 and T2 segments.

b. Lesion in SCG disease or experimentally by section in the cervical sympathetic chain.

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80
Q

What is the site of Horner’s syndrome?

A

Manifestations occur at the same side of the lesion.

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81
Q

What are the signs of Horner’s syndrome?

A

a. Ptosis β†’ dropping of upper eyelids due to paralysis of superior tarsal ms.

b. Miosis β†’ constriction of the pupil due to paralysis of dilator pupillae ms.

c. Enophthalmos β†’ sinking of eye ball into orbit due to paralysis Muller’s ms.

d. Anhydrosis β†’ absence of sweat secretion leading to dryness affected side of the face.

e. Vasodilatation of skin blood vessels, due to loss of sympathetic vasoconstrictor tone, so the skin becomes red and warm.

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82
Q

What is the origin of sympathetic supply to the thorax?

A

β€’ LHCs of upper 4 or 5 thoracic segments of the spinal cord.

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83
Q

What is the relay o the sympathetic supply to the thorax?

A

β€’ 3 cervical ganglia and upper 4 thoracic ganglia.

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84
Q

What is the sympathetic supply to the thorax directed to?

A

Heart and lungs

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85
Q

What is the function of the sympathetic supply to the thorax?

A

1-Heart

A- It ↑ the heart rate, the force of contraction, conductivity, and excitability →↑ the effectiveness of the heart as a pump.

B- Coronary vessels:
β€’ Direct effect β†’ vasoconstriction. (For few seconds)
β€’ Indirect effect β†’ vasodilatation (due to accumulation of metabolites).

2-Lungs

a. Inhibition of the smooth ms of the bronchi β†’ bronchodilatation.

b. Inhibition of the mucus secretion of air passages.

c. Vasoconstriction of the pulmonary blood vessels.

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86
Q

What is the origin of the sympathetic supply to the abdomen?

A

LHCs of T6-T12 segments of the spinal cord (splanchnic nerves).

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87
Q

What is the relay of the sympathetic supply to the abdomen?

A

β€’ collateral (prevertebral) ganglia (celiac, superior mesenteric, aortico-renal).

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88
Q

What what are the organs that are affected by the sympathetic supply to the abdomen?

A

1- GIT
2- Liver
3- Gall bladder
4- Pancreas
5- Spleen
6- Blood vessels
7- Kidneys
8- SRM

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89
Q

What is the effect of sympathetic supply on the GIT?

A

(Stomach, small intestine, and proximal part of large intestine):

β€’ Relaxation of their walls and contraction of their sphincters β†’ inhibition of digestion and delayed evacuation of their contents.

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90
Q

What is the effect of the sympathetic supply on the liver?

A

β€’ Stimulation of glycogenolysis β†’ ↑ed blood glucose.
β€’ Stimulation of fibrinogen synthesis.( for blood clotting)

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91
Q

What is the effect of the sympathetic supply on the gall bladder?

A

β€’ Relaxation of its wall and contraction of sphincter of Oddi β†’ retention of bile and delayed emptying of gall bladder.

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92
Q

What what is the effect of the sympathetic supply on the spleen?

A

β€’ Contraction of smooth muscles in splenic capsule and trabeculae β†’ pouring of about 250 ml (especially in cases of hemorrhage) of stored blood into the general circulation.

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93
Q

What is the effect of the sympathetic supply on the pancreas?

A

β€’ It inhibits both endocrine and exocrine pancreatic secretion.

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94
Q

What is the effect of the sympathetic supply on the blood vessels?

A

β€’ Mixed supply (vasoconstriction and vasodilatation)

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95
Q

What is the effect of the sympathetic supply to the kidneys?

A

β€’ Stimulation of juxtaglomerular cells β†’ ↑ed renin secretion.
β€’ ↓es renal blood flow.
β€’ ↓es urine output.

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96
Q

What is the origin of the sympathetic supply to the SRM?

A

β€’ LHCs of T10 and 11segments of the spinal cord.

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97
Q

What is the relay of the sympathetic supply to the SRM?

A

β€’ SRM is supplied by sympathetic preganglionic nerve fibers (with no postganglionic nerve fibers) which relay directly with the SRM cells (chromaffin cells).

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98
Q

What is the function of the sympathetic supply to the SRM?

A

β€’ Stimulation of sympathetic nerves to SRM β†’releases adrenaline (80%) and noradrenalin (20%) into the circulating blood.

β€’ These hormones have prolonged action due to their slow clearance from the circulation.

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99
Q

What is the function of both adrenaline and noradrenaline?

A

‒ Adrenaline → acts more on metabolic actions of the body while noradrenalin→acts more on blood vessels.

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100
Q

What happens in stress conditions regarding SRM and the sympathetic nervous system?

A

In stress conditions, SRM acts together with the sympathetic nervous system (sympathoadrenal system).

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101
Q

What is the origin of the sympathetic supply to the pelvis?

A

LHCs of L1, L2, and L3 segments of the spinal cord.

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102
Q

What is the relay of the sympathetic supply to the pelvis?

A

β€’ Inferior mesenteric or hypogastric ganglia.

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103
Q

What are the organs affected by the sympathetic supply to the pelvis?

A

Urinary bladder, rectum, and sex organs.

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104
Q

What are the functions of the sympathetic supply to the pelvis on the Urinary bladder?

A

Relaxation of its wall and contraction of internal urethral sphincter β†’ urine retention.

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105
Q

What is the effect of sympathetic supply to the rectum?

A

‒ Relaxation of its wall and contraction of internal anal sphincter→ retention of feces.

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106
Q

What is the effect of the sympathetic supply on sex organs?

A

In male:

a) Contraction of smooth ms in the walls of the seminal vesicle, epididymis, vas deferens, and ejaculatory duct
β†’ ejaculation of semen.
b) VC of blood vessels of pelvic viscera including external sex organs β†’ shrinkage of the penis.

In female:

a) VC of blood vessels of external sex organs β†’ shrinkage of the clitoris.
b) Variable effects on the uterus, mainly inhibitory but may be excitatory in late pregnancy.

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107
Q

What is the origin of the sympathetic supply to the somatic structures?

A

􏰀 Upper limb from LHCs of T2-9.
􏰀 Lower limb from LHCs of T10-L2.
􏰀 Thoracic and abdominal walls from LHCs of T1-L2.

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108
Q

What is the function of the sympathetic supply to the somatic structures?

A

1- Skin
􏰀 VC of blood vessels.
􏰀 Hair erection.
􏰀 Sweat secretion.

2-Skeletal muscles
􏰀 VD of skeletal muscle blood vessels.

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109
Q

What is the Orbelli phenomenon?

A

-Better contraction, delayed onset of fatigue, early recovery after fatigue due to V.D. of blood vessels which supply O2 and nutrients to contracting muscles and remove CO2 and waste products from muscles so prevent or delay fatigue.

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110
Q

What provides most of the control function over our bodies?

A

The nervous system

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111
Q

What does the nervous system do?

A

It receives thousands of information from different sensory organs and analysis all of them to determine the response to be made by the body.

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112
Q

What is the neuron?

A

It is the structural or anatomical unit of the nervous system.

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113
Q

What is the neuron formed from?

A

It is formed from the cell body and cell processes.

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114
Q

What is the function of the cell body of the neuron?

A

Controls the activity of the whole neuron.

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115
Q

What are the processes of the neuron?

A

Axon: Single long process - the conducting part - conducts impulses away from the cell body

Dendrites: Multiple short processes that inc. the surface area of the cell body - the receptive part - conduct impulses towards the cell body

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116
Q

Near the termination of the axon, what does it join?

A

-Muscleβ€”-> neuro-muscular junction
-Glandβ€”β€”> neuro-epithelial junction
-Another neuronβ€”-> neuro-neural junction

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117
Q

What are the types of neurons?

A
  1. Afferent=sensory: carries impulses from receptors to CNS.
  2. Efferent=motor: carries impulses from CNS to effector organs like muscles
  3. Interneurons=associative: located inside CNS, Act as a link between neurons, 99% of nerve cells.
118
Q

What is reflex action?

A

Reflex action is the involuntary (programmed) response of a part of the body to a stimulus.

119
Q

How is reflex action carried out?

A
  • Reflex action is carried out through a pathway called the reflex arc.
120
Q

What is the functional or physiological unit of the nervous system?

A

Reflex action

121
Q

What are the components of the reflex pathway?

A
  1. Receptors.
  2. Afferent (sensory).
  3. Center (in CNS).
  4. Efferent (motor).
  5. Effectors (muscles or glands).
122
Q

What are the divisions of the nervous system?

A

-CNS
-PNS

123
Q

What is the definition of the central nervous system?

A

-It is the part of the nervous system which is protected by bone (skull and vertebral column).

124
Q

What are the parts of the CNS?

A

-It is consists of the brain and spinal cord.

A) Brain, which has 3 major subdivisions:

1-Cerebrum (2 cerebral hemispheres) which consists of:
a) Cerebral cortex.
b) Subcortical centers: thalamus, hypothalamus, and basal ganglia.

2-Brain stem: consists of 3 regions: midbrain, pons, and medulla oblongata.

3-Cerebellum.

B)Spinal cord: It is subdivided into 31 segments into the following regions:

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

  • Each spinal segment gives a pair of spinal nerves on both sides.
125
Q

What is the function of the peripheral nervous system?

A

The peripheral nervous system provides communication between the CNS and other tissues via nerves (PNS).

126
Q

What are the divisions of the PNS?

A

They are classified anatomically (cranial and spinal) and physiologically (somatic and autonomic)

127
Q

What are the divisions of the PNS according to anatomical classification?

A

1- 12 pairs of cranial nerves.
2- 31 pairs of spinal nerves.

128
Q

Cranial nerves

A
  • All of them (12 pairs) arise from the brain & they include:

I - OLFACTORY - SMELL (CEREBRUM)

II - OPTIC - VISION (CEREBRUM)

III - OCULOMOTOR - MOVING THE EYEBALL (MIDBRAIN)

IV - TROCHLEAR - MOVING THE EYEBALL (MIDBRAIN)

V - TRIGEMINAL - SENSORY TO FACE (PONS)

VI - ABDUCENT - MOVING THE EYEBALL (PONS)

VII - FACIAL NERVE - MOVING FACIAL MUSCLES (PONS)

VIII - AUDITORY - HEARING (PONS)

IX - GLOSSOPHARYNGEAL - TASTE SENSATION FROM TONGUE AND PHARYNX AND SECRETORY TO SALIVARY GLANDS (MEDULLA OBLONGATA)

X - VAGUS - SENSORY AND MOTOR TO MUSCLES OF THORATC AND ABDOMINAL VISCERA (MEDULLA OBLONGATA)

XI - ACCESSORY - MOVING MUSCLES OF THE BACK OF THE NECK (MEDULLA OBLONGATA)

XII - HYPOGLOSSAL - MOVING THE TONGUE (MEDULLA OBLONGATA)

129
Q

What are the purely sensory cranial nerves?

A

I - II - VIII Fiat β€œ128”

130
Q

What are the purely motor cranial nerves?

A

III - IV - VI β€œ346”

131
Q

What are the mixed cranial nerves?

A

Anything except 128 and 346

132
Q

Spinal nerves

A
  • they are 31 pairs
  • These are attached to the spinal cord.
  • Each spinal nerve arises from the sides of the spinal cord by two roots: dorsal and ventral.
  • All spinal nerves are mixed nerves (sensory and motor).
133
Q

What is the peripheral nervous system classified into physiologically?

A

Somatic and autonomic

134
Q

Somatic nervous system

A

Voluntary - Connected With (skin, Skeletal muscles, tendons, bones, and joints)

135
Q

Autonomic nervous system

A

Involuntary - Connected With (Smooth muscles, glands, and cardiac muscle).

136
Q

What is the origin of the sympathetic NS?

A
  • Originates from LHCs of all thoracic and upper 3 lumbar segments of the spinal cord.
137
Q

What is the origin of the parasympathetic NS?

A
  • Cranial and sacral
  • Cranial part:
     arises from cranial nerves: C III, VII, IX, and X (1973)

2- Sacral part:
 Arises from 2nd, 3rd, and 4th sacral segments of the spinal cord, their fibers unite to form the pelvic nerve.

138
Q

What is the origin and relay of the oculomotor nerve?

A

-Edinger Westphal nucleus in the midbrain
-Ciliary ganglion

139
Q

What is the origin and relay of the facial nerve?

A

-Superior salivary nucleus in the pons

-1. Greater superficial petrosal branch→ Sphenopalatine(petrosal) ganglion.
2. Chorda tympani branch β†’Submandibular ganglion

140
Q

What is the origin and relay of the glossopharyngeal nerve?

A

-Inferior salivary nucleus in the medulla oblongata.
-Otic ganglion

141
Q

What is the origin and relay of the vagus nerve?

A

-Dorsal motor nucleus of vagus in the medulla oblongata
-Terminal ganglion

142
Q

What is the origin and relay of the pelvic nerve?

A

-Sacral segments (S2,3,4) and preganglionic nerve fibers unit together to form pelvic nerve or nervous erogenous.

-Terminal ganglia

143
Q

What is the function of the parasympathetic supply by the oculomotor nerve?

A

a. Contraction of constrictor pupillae ms β†’ narrowing of the pupil (miosis)

b. Contraction of ciliary ms β†’ ↑ed convexity of the lens β†’ helps eyes to see near objectsβ†’ accommodation to near vision

144
Q

Why is parasympathetic stimulation important in near vision like reading?

A

to decrease the size of the pupil to decrease the amount of light entering the eye and increase the lens power to focus the image of the object on the retina of the eye

145
Q

What is the function of the parasympathetic supply by the facial nerve?

A

a- Greater superficial petrosal nerve: (GSP)
1. Lacrimal glands:
i) Vasodilatation.
ii)Secretion of tears from lacrimal glands
2. Mucus membrane of the nose, soft palate, and pharynx: i)Vasodilatation.
ii)Secretion of mucus. (nasal secretion with crying)

b- Chorda tympani nerve:
1. Submandibular and sublingual salivary glands:
i) Vasodilatation.
ii) True salivary secretion (large in volume, watery, rich in electrolytes, and poor in enzymes).
2. Mucus membrane of anterior 2/3 of tongue and floor of mouth→ vasodilatation and mucous secretion.

146
Q

What is the function of the parasympathetic supply by the glossopharyngeal nerve?

A
  1. Parotid salivary gland
    i) Vasodilatation.
    ii) True salivary secretion.
  2. Mucus membrane of posterior 1/3 of tongue and floor of mouth→ Vasodilatation
147
Q

What are the nerves responsible for parasympathetic supply to the head and neck?

A

i) Oculomotor nerve
ii) Facial nerve
iii) Glossopharyngeal nerve

148
Q

What are the organs affected by the parasympathetic supply of the vagus nerve?

A

-Thorax (heart and lungs)
-Abdomen (GIT, Glands, Liver, Gall bladder, and blood vessels)

149
Q

What is the function of the parasympathetic supply of the vagus nerve at the heart?

A

a. It ↓es the heart rate, the force of contraction, conductivity, and excitability →↓es the effectiveness of the heart as a pump.

b. Coronary vessels
οƒœ Direct effect β†’ vasodilatation
οƒœ Indirect effect β†’ vasoconstriction because it inhibits cardiac work with less production of metabolites

β€œ Vagus nerve supplies the atria only and does not supply the ventricles

150
Q

What is the function of the parasympathetic supply of the vagus nerve at the Lungs?

A

a. Contraction of smooth ms of the bronchi β†’ bronchoconstriction.
b. Stimulate the mucus secretion of the air passages.
c. Vasodilatation of the pulmonary blood vessels.

β€œThat’s why asthma happens casually at night”

151
Q

What is the function of the parasympathetic supply of the vagus nerve at the GIT ( esophagus, stomach, small intestine, and proximal part of the large intestine)?

A

Contraction of their walls and relaxation of their sphincters β†’ help both digestion and evacuation of GIT contents i.e. helps deglutition, gastric motility, and peristaltic movement.

152
Q

What is the function of the parasympathetic supply of the vagus nerve at the glands?

A

οƒœ Gastric glandsβ†’ ↑es gastric juice secretion (rich in HCL).
οƒœ Bruner’s glands in the duodenum→↑es alkaline mucus secretion.
οƒœ Pancreas: stimulates both endocrine and exocrine components pancreatic secretions

153
Q

What is the function of the parasympathetic supply of the vagus nerve at the Liver?

A

It ↑es hepatic bile flow.

154
Q

What is the function of the parasympathetic supply of the vagus nerve at the gall bladder?

A

Contraction of its wall and relaxation of the sphincter of Oddi β†’ help its evacuation.

155
Q

What is the function of the parasympathetic supply of the vagus nerve at the blood vessels?

A

Vasodilatation

156
Q

What is the function of the parasympathetic supply by the pelvic nerve at the urinary bladder?

A

Contraction of its wall and relaxation of internal urethral sphincter β†’ micturition.

157
Q

What are the organs affected by the parasympathetic supply of the pelvic nerve?

A

Urinary bladder, rectum, and sex organs

158
Q

What is the function of the parasympathetic supply by the pelvic nerve at the Rectum?

A

Contraction of its wall and relaxation of internal anal sphincter β†’ defecation.

159
Q

What is the function of the parasympathetic supply by the pelvic nerve at the Sex organs?

A
  1. Vasodilatation of the blood vessels of the pelvic viscera including that of sex organs β†’ erection of the penis, clitoris, and congestion of the labia.
    -So, the pelvic nerve is named the nervous erogenous.
  2. It ↑es the secretions from the seminal vesicles, prostate
160
Q

Are the external anal and urethral sphincters voluntary or involuntary?

A

They are voluntary ms supplied by the somatic spinal pudendal nerve.

161
Q

What are the organs that have sympathetic supply only?

A

1) Dilator pupillae muscle
2) Muller’s muscle.
3) Cutaneous effectors
4) Ventricles of the heart.
5) Spleen
6) Adrenal medulla

162
Q

What are the organs that are affected by the parasympathetic supply only?

A

1) Constrictor pupillae muscle
2) Upper esophagus.
3) Glands of stomach

163
Q

What are the types of relations between sympathetic and parasympathetic nervous systems?

A

-Antagonistic: one system increases the function and the 2nd decreases the functions e.g. heart rate, sympathetic NS increases HR, and parasympathetic N.S. decreases HR

-Synergistic: during salivary secretion (sympathetic secretes enzymes and parasympathetic secretes water and electrolytes)

-Cooperative: during sexual intercourse (parasympathetic NS causes erection and sympathetic NS causes ejaculation)

164
Q

What are the types of membrane potentials?

A

-RMP
-GRADED POTENTIAL
-ACTION POTENTIALv

165
Q

What is the graded potential?

A

-A local change in the resting membrane potential as a result of stimulation by an ineffective stimulus.

-The duration and magnitude of these changes are variable according to the stimulus

166
Q

What are examples of graded potential?

A

RSPML

a) Receptor potential, at the beginning of the sensory nerves.
b) Synaptic potential, in the synapses inside the CNS.
c) Pacemaker potential, in the heart.
d) Miniature endplate potential, at the neuromuscular junction.
e) Local excitatory state, at the cell bodies of neuron

167
Q

What is action potential?

A

-It is the electrical changes that occur in resting membrane potential as a result of stimulation by an effective stimulus

-These changes propagate along the nerve fibers and produce responses or actions.

168
Q

What is RMP?

A

It is the potential difference between the outside and inside of the nerve fiber during rest.

169
Q

Where is RMP present?

A

RMP is present in nerves, muscle fibers, and all cells of the body with the inside negative relative to outside.

170
Q

What are the values of RMP?

A

It varies according to the excitable tissue:

Nerves
-70 mV.
Skeletal muscles
-90 mV
Cardiac muscle
-90 mV
Smooth muscles
-60 mV

171
Q

How is RMP measured?

A

-By two microelectrodes connected with a special voltmeter.

-One of these microelectrodes is inserted inside the nerve fiber.

172
Q

What are the causes of RMP?

A

RMP is due to unequal distribution of ions on both sides of the cell membrane with excess cations outside and excess anions inside, which is produced as a result of 2 main factors:

(a) Selective permeability of cell membranes.
(b) Na+- K+ pump

173
Q

What are the substances that pass the membrane by selective permeability?

A

-proteins
-K+
-Na+
-Cl-

174
Q

Selective permeability of proteins

A

Cell membranes are impermeable to intracellular protein anions (because of their large size).

175
Q

Selective permeability of K+

A

K+ ions diffuse from inside the cell to outside due to:
1) Concentration gradient: (inside 30-40 times > outside).
2) High permeability of the membrane to K ions (their permeability to K+ is 50-100 times greater than their permeability to Na+).

οƒœ this is limited due to:
a) The electrical gradient is directed inwards.
b) Positive charge on the outside of membrane repels K+ ions inwards.
c) Na+- K+ pump actively drives K+ ions inwards.

176
Q

Selective permeability of Na+

A

Na+ ions tend to diffuse from outside to inside due to:
a) Concentration gradient (outside > inside 10 times)
b) Electric gradient (inside is negative).

But this is limited due to the low permeability of the cell membrane to Na+, Therefore, Na+ ions accumulate outside the membrane, helped by the Na+-K+ pump producing a positive charge.

177
Q

Selective permeability of Cl-

A

Cl-ions tend to diffuse from outside to inside due to: Concentration gradient (outside > inside 25 times).

However, this is limited because the interior of the cell has a great negative charge and therefore, they are expelled out of the cell.

178
Q

What is the concentration of ions inside and outside of the cell?

A

o ECF:ICF ratio for Na+ions is 10:1
o ECF: ICF ratio for K+ ions is 1:35
o ECF: ICF ratio for Cl-ions is 25:1

179
Q

What are the three basic types of ion channels?

A

1) Passive ion channels: the movement of ions through these channels is the cause of RMP.

2) Chemically activated ion channels.

3) Voltage-activated ion channels, open when they detect a certain voltage. They are responsible for the generation of action potential

180
Q

Na+-K+ Pump

A

 Na+ ions are not allowed to accumulate inside the nerves.

 They are pumped out by an active process (since it occurs against concentration and electrical gradients) which needs energy (provided from the breakdown of ATP by Na+-K ATPase enzyme).

 It helps to maintain the RMP since it pumps 3 Na+ ions outside the cells and 2 K+ ions inside the cell which produces a net movement of positive charges
out of the cell.

181
Q

What does Na- K Pump have?

A

a) ATPase property i.e. has the ability to split ATP.
b) 3 Na+ binding sites β†’ at ICF side.
c) 2 K+ binding sites β†’ at ECF side.
d) ATP binding sites β†’ at ICF side.

182
Q

What happens during equilibrium regarding the membrane potential?

A

At equilibrium and as a result of selective permeability of cell membranes and Na+- K+ pump, the outer surface of the nerve fibers will be positively charged (mainly due to Na) while inner surfaces will be negatively charged (mainly due to protein) producing a potential difference of about -70 mV (which is the RMP).

183
Q

What happens if a condition decreases metabolic activity like cooling?

A

inhibits Na-K pump, So, Na+ ions will accumulate inside the cell and neutralize the -ve charges of protein ions, and K ions that are held on the outer surface escape away, and RMP becomes progressively lost.

184
Q

What is the definition of a synapse?

A

It is the functional connection between a neuron and a second cell (neuron or muscle or glands)

185
Q

What is the structure of a synapse?

A

is formed of 3 parts:

a) Presynaptic portion→ transmits impulse towards the synapse
b) Postsynaptic portion→ transmits impulse away from the synapse.
c) Synaptic cleft β†’is full of interstitial fluid which separates the nerve ending from the next neuron or effector organ.

186
Q

What is the definition of the electrical synapse?

A

Is a gap junction between the presynaptic membrane
and postsynaptic membrane.

187
Q

Is the electrical synapse common or rare?

A

Rare

188
Q

What is the function of electrical synapses?

A

It allows direct transmission of the electrical depolarization waves from the presynaptic to the postsynaptic neuron

189
Q

What is the definition of chemical synapses?

A

It is a junction between the presynaptic and postsynaptic membrane which is chemically mediated.

190
Q

Are chemical synapses common or rare?

A

Common

191
Q

What is the function of chemical synapses?

A

A chemical substance is released at the nerve endings which allows the transmission of nerve impulses from one neuron to another neuron.

192
Q

What are the types of chemical transmitters?

A

-Types of chemical transmitters:

chemical transmitters released by autonomic nerve endings include :
a) acetylcholine. b) noradrenaline

193
Q

What are the types of nerve endings?

A

a) Cholinergic nerve fibers: secrete acetylcholine.
b) Adrenergic nerve fibers: secrete noradrenaline

194
Q

What are the sites of the release of acetylcholine?

A

a) All preganglionic sympathetic and parasympathetic nerve endings.

b) Preganglionic sympathetic nerve fibers to the suprarenal medulla.

c) All postganglionic parasympathetic nerve ending.

d) Sympathetic postganglionic fibers supplying skeletal ms blood vessels and sweat glands.

e) Somatic motor nerve ending to skeletal muscle (motor endplate).

f) Some synapses at CNS (brain and spinal cord).

195
Q

How is ach biosynthesized?

A

Ach is formed by a reaction between choline and acetyl CoA as follow;
ATP
Acetyl CoA + choline β€”β€”β€”β€”β€”β€”β€” > acetylcholine + CoA

NB:-

-CAT (choline acetyltransferase)
- ATP and glucose are required to form acetyl CoA.

196
Q

Where is ach stored?

A
  • Ach is stored inside the nerve terminals in minute vesicles
  • Each vesicle contains more than one thousand Ach molecules (5000-10000 molecules)
  • Some molecules of Ach are found free in the cytoplasm.
197
Q

How is ach released?

A

The arrival of action potential (depolarization) to nerve ending β†’ open Ca2+ channels →↑ed Ca2+ influx to inside nerve endings β†’ interact with the vesicles adjacent to the membrane causing them to fuse with the membrane β†’ rupture of vesicles emptying their contents outside the nerve fibers by exocytosis

  • Released Ach which passes rapidly over the gap (10-30 nm) between nerve terminals β†’ Ach binds to receptors on the effector organs.
198
Q

What is the mechanism of action of ach?

A

Ach binds with its receptors on the postsynaptic membrane which might be;

i) Ligand-gated ion channels β†’ Na+ and Ca2+ influx β†’ depolarization (stimulation) or K+ and Cl_ influx β†’ hyperpolarization (inhibition).

ii) G-protein coupled receptors β†’ activate membrane enzymes such as adenyl cyclase β†’ formation of 2nd messenger called cyclic AMP from ATP β†’ intracellular signal

199
Q

How is ach removed?

A

A-Hydrolysis of Ach by cholinesterase enzyme
B- Diffusion
C- Reuptake of Ach

200
Q

-Hydrolysis of Ach by cholinesterase enzyme:

A

Acetylcholine choline is hydrolyzed by cholinesterase to give acetic acid and Choline

201
Q

What is the action of choline?

A

Choline has a similar action to acetylcholine but is weaker.

202
Q

Which of choline and the acetate ion and choline is reputakable and which one diffuses?

A

Acetate ions diffuse into the blood, while the choline base is reuptake back into the nerve ending to be recycled to form new acetylcholine.

203
Q

-diffusion of ach

A
  • Small part of Ach escapes to the surrounding tissues→↓ed Ach concentration.
204
Q

-Reuptake of ach

A
  • is not yet definite
205
Q

What is the function of cholinesterases?

A

-is to keep the action of acetylcholine localized in the site of liberation, so prevent its diffusion to the blood causing generalized parasympathetic effects.

206
Q

What are the function of anticholinesterases and an example for them?

A

e.g. neostigmine are drugs that block the action of cholinesterase, so prolong the action of Ach and are used to treatment of some diseases such as myasthenia gravis

207
Q

What is the action of acetylcholine?

A

Ach has two main types of actions: Muscarinic and Nicotinic

208
Q

comparison between muscarinic and nicotinic actions

A

Acc to SSODA

-Similar to the action of
-Site
-Onset
-Duration
-Antagonist

209
Q

What is the muscarinic action of acetylcholine similar to?

A

Muscarine, an alkaloid, derived from poisonous Mushroom

210
Q

What is the site of the muscarinic action of acetylcholine?

A

On smooth ms and glands

  • supplied by parasympathetic and Sympathetic cholinergic nerve fibers
211
Q

What is the onset of their muscarinic action of acetylcholine?

A

Slow

212
Q

What is the duration of the muscarinic action of acetylcholine?

A

Prolonged

213
Q

What is the antagonist of the muscarinic action of acetylcholine?

A

Atropine

214
Q

What is the nicotinic action of acetylcholine similar to?

A

Nicotine which is derived from Tobacco

215
Q

What is the site of the nicotinic action of acetylcholine?

A
  • autonomic ganglia and neuromuscular junction
  • (contraction of skeletal ms, stimulation of ganglia, secretion of adrenaline and noradrenaline from
216
Q

What is the onset of the nicotinic action of acetylcholine?

A

Rapid

217
Q

What is the duration of the nicotinic action of acetylcholine?

A

Short

218
Q

What is the antagonist of the nicotinic action of acetylcholine?

A

ganglion and neuromuscular blockers

219
Q

What are cholinergic receptors?

A

They are the receptors that respond to Ach.

220
Q

Compare between muscarinic and nicotinic receptors

A

Acc to NSSAA

-Nature
-Site
-Subtypes
-Agonist
-Antagonist

Muscarinic:-

  • Ligand-gated ion channels

-Present on the effector organs at all postganglionic cholinergic nerve terminals.

-M1β†’ in the brain and autonomic ganglia.
M2β†’ in the heart
M3β†’ in the smooth ms and secretory glands.
M.4 β†’ in the pancreas. M5 β†’ under investigation

  • Muscarine alkaloid.
  • Atropine

Nicotinic:-

  • G-protein coupled receptors
  • Present in autonomic ganglia (either sympathetic or parasympathetic), suprarenal medulla, and motor endplate
  • i-Neuronal Nicotinic (Nn)
  • At autonomic ganglia.
  • At suprarenal medulla.
    ii-Muscle Nicotinic (Nm)
  • at motor end plated
  • Nicotine (small dose).
  • Nicotine (large dose).
221
Q

What is the definition of the action potential?

A
  • It Is the electrical changes that occur in the resting membrane potential as a result of stimulation by an effective stimulus.
  • In the case of nerve fibers, it is transmitted as a self-propagated disturbance known as the nerve impulse.
222
Q

What are the components of the action potential?

A

The AP consists of 2 main stages:
β€’ (depolarization and repolarization) that are followed by 2 other stages:
β€’ after-depolarization and after-hyperpolarization.

223
Q

What is the definition of depolarization?

A

It is a loss of the normal resting polarized state of the membrane.

224
Q

What is the ionic basis of depolarization?

A

-The stimulus increases the permeability of the cell membrane to Na+ ions, which diffuse inside causing the gradual change in the membrane potential from the resting potential (-70m.v) to the isoelectric line (zero) and exceeding it to +35 mv (overshot) by 2 steps separated by the firing level which equals –55 mv

-The first step is slow depolarization in which the membrane potential shifts from -70 mv to -55 mv (firing level) due to the opening of some Na+ channels

-The second step is Rapid depolarization in which the membrane potential shifts from -55 mv to +35 mv (overshot) due to the opening of all Na+ channels and it results in A.P. having a magnitude of
105 mV (from -70 to + 35mV).

  • In the resting state, only the inactivation gates of Na+ channels are open, so the membrane permeability to Na+ is low and When the nerve is stimulated, the Na+ activation gates also open thus the membrane permeability to Na+ and Na+ influx markedly increased
225
Q

Which Na+ Gates are open during resting state and what does this cause?

A

In the resting state, only the inactivation gates of Na+ channels are open, so the membrane permeability to Na+ is low.

226
Q

Which Na+ gates are open when the nerve is stimulated?

A

When the nerve is stimulated, the Na+ activation gates also open thus the membrane permeability to Na+ and Na+ influx markedly increased

227
Q

What is the definition of depolarization?

A

-It is the restoration normal resting polarized state of the membrane.

-It is recorded as a fall of the membrane potential in the negative direction from +35 to – 70, producing the descending limb of action potential

228
Q

What are the steps of repolarization?

A

1) RP proceeds immediately and rapidly after the overshoot is reached

2) When RP is 70% completed, its rate decreases by about 4 msec. (after-depolarization or (negative after-potential).

3) After RP is completed, the membrane potential overshoots to the negative side (by 1-2 mV) leading to hyperpolarization of the membrane (after-hyperpolarization or positive after-potential).

4) It lasts about 40 msec but its magnitude gradually declines till normal resting membrane potential is restored.

229
Q

What is the ionic basis of repolarization?

A

1-Stoppage of Na+ influx due to:-

A-Closure of Na+ inactivation gates.
B- Reversal of direction of the electrical gradient for Na+ (which becomes from inside to outside the membrane)

2-K+ efflux (exit):

A-occurs through specific K+ channels that contain a single gate located toward the inside of membrane.
B-The decrease in membrane polarity during depolarization leads to the opening of K+ gates and K+ efflux

3- The negative after-potential stage:

-is due to slowing of the rate of K+ efflux,
- while the positive after-potential is due to sow return of K+ channels to the closed state (which allows prolonged K+ efflux).

4- Following the AP, the normal distribution of Na+ and K+ ions across the cell membrane is restored by the action of the Na+-K+ pump

230
Q

What is the compound action potential?

A

This is the AP recorded from peripheral nerves when stimulated by maximal stimuli.

231
Q

In Which type of nerve fibers is the conduction the fastest?

A

-These nerves contain different types of nerve fibers that vary in their speeds of conduction (the thicker the nerve fiber, the more rapid is its rate of conduction of nerve impulses and vice versa.

-Thus, the activity in fast conducting fibers arrives at recording electrodes earlier than activity in slower nerve fibers resulting in a cAP that have multiple peaks

232
Q

What is noradrenaline?

A

The chemical transmitter of the sympathetic nervous system.

233
Q

What are catecholamines?

A
  1. Noradrenaline.
  2. Adrenaline.
  3. Dopamine.
234
Q

What are the sites of the release of catecholamines?

A

1- All postganglionic sympathetic fibers except those supplying skin, skeletal ms blood vessels, and sweat glands.

2- Some synapses in CNS.

3- Suprarenal medulla: adrenaline (80%) and noradrenaline (20%).

235
Q

How is catecholamine synthesized?

A
  • Noradrenaline is derived from tyrosine amino acids.
  • Synthesis begins in the cytoplasm of terminal nerve endings and is completed in vesicles present in adrenergic nerve fibers.
  • Synthesis occurs in the chromaffin cells of SRM and in the CNS neurons.

οƒœ In liver:
β€’ Phenylalanine - hydroxylation β€”β€”> tyrosine.

οƒœ In axoplasm of adrenergic nerve fiber:

β€’ Tyrosine - hydroxylation β€”β€”> DOPA - decarboxylation β€”β€”> dopamine

οƒœ In adrenergic vesicles at nerve ending: Transport of dopamine. β€’ Dopamine - +OH β€”β€”> Noradrenaline.

οƒœ In SRM and CNS neurons: this reaction goes one step to form adrenaline. Noradrenaline - +CH3 β€”β€”> Adrenaline

236
Q

Where is dopamine present in higher conc. Than noradrenaline?

A

In basal ganglia of the brain

237
Q

Where are catecholamines stored?

A
  • NA is stored inside the nerve terminals in tiny vesicles (1000 molecules or more).
  • But some molecules are found free in the cytoplasm.
  • In the adrenal medulla, adrenaline and NA are stored in the form of granules in the
    chromaffin cells.
238
Q

How is catecholamine released?

A
  • when the action potential reaches the axon terminal it opens the voltage-gated Ca+2 channels β†’ Ca2+ influx β†’increase Ca2+ level β†’ move the vesicles toward the membrane and fuse with it β†’ vesicles rupture and empty their content outside nerve fiber NA cross the cleft (10-30 nm) & bind to its receptors on effector organ.
  • Stimulation of Symp. preganglionic nerve fibers relaying on chromaffin cells in SRM causes adrenaline and NA release.
239
Q

What is the mechanism of action of Noradrenaline?

A

When NA binds with its receptors on the postsynaptic membrane, it leads to :

  1. change of cell membrane permeability to various ions. It either:
    ➒ ↑es membrane permeability to Na and Ca β†’ ↑ed Na and Ca influx β†’ depolarization (stimulation).
    ➒ ↑es membrane permeability to K and Cl β†’ ↑ed K and Cl influx β†’ hyperpolarization (inhibition)
  2. Activation of adenyl cyclase → conversion of ATP into cAMP→ initiates many intracellular activities.
240
Q

How is noradrenaline removed?

A

Once, NA produces its action, it is rapidly removed in three different ways:

  • Neuronal uptake (85 %)

β€’ NA is actively reuptaken into the adrenergic nerve end where it is stored in the vesicles or oxidized by monoamine oxidase (MAO).

  • Extra neuronal uptake (15 %)
    β€’ NA is inactivated by catechol-o-methyl transferase (COMT).
  • Excretion in urine
    β€’ Small amount of NA escapes enzymatic destruction and is excreted in urine (conjugated with glucuronic acid)
241
Q

Compare between MOA and COMT in terms of:

Name:
Site of uptake:
Type of process:
Amount removed:
Sites:

A

Mono-amino-oxidase
Catecholamine o- methyltransferase

Neuronal.
Extra –neuronal.

Produce oxidation
Produce methylation (then Excretion by glucuration)

Removal of 85% of adrenaline.
Removal of 15% of adrenaline.

-Present in mitochondria of
adrenergic fibers, liver, and kidney (ALK)
-Present in all tissues especially the kidney
and brain (KB)

242
Q

What is the definition of adrenergic receptors?

A

adrenergic receptors are receptors that respond to NA and adrenaline.

243
Q

What is the classification of adrenergic receptors?

A
  1. Ξ± adrenergic receptors: subclassified into (Ξ± 1: excitatory and Ξ± 2: inhibitory)
    β€’ They are equally sensitive to adrenaline and NA.
  2. Ξ² adrenergic receptors: subclassified into (Ξ² 1 , Ξ² 2 , Ξ² 3 , Ξ² 4 , Ξ² 5 )

β€’ Ξ²1:
o Are sensitive to both norepinephrine and epinephrine
o Are more sensitive than the Ξ±1 receptors

β€’ Ξ²2:
o Are more sensitive to epinephrine than to norepinephrine.
o Are more sensitive to epinephrine than the Ξ±1 receptors.

N.B
➒ Ξ²3 receptors: located in the adipose tissues β†’ increase lipolysis.
➒ β4 and β5 receptors: under research.

244
Q

What are the sites of alpha 1 receptors?

A

-Are postsynaptic receptors located on smooth ms of blood vessels in the skin and splanchnic regions, the GIT and bladder sphincters, and dilator pupillae ms of the iris and piloerector ms

245
Q

What is the mechanism of action of alpha 1 receptors?

A

Are G-protein coupled receptors that activate phospholipase C, and increase in inositol 1,4,5-triphosphate (IP3) and intracellular [Ca2+] to make contraction or excitation

246
Q

What are the physiological actions of alpha 1 receptors?

A

Mainly excitatory:-

➒ Vasoconstriction
➒ Contraction of piloerector muscle.
➒ Contraction of splenic capsule.
➒ Contraction of the seminal vesicle, ejaculatory duct.
➒ Contraction of bladder & intestinal sphincters.
➒ Adrenergic sweating in the palm.

-Inhibitory effects as
➒ Intestinal relaxation.
➒ Inhibition of insulin secretion.

247
Q

What are the sites of alpha 2 receptors?

A
  1. Presynaptic: On presynaptic sympathetic nerve ending and on ganglion cells (autoreceptors).
  2. Postsynaptic in some effector organs e.g. platelets, fat cells, and the walls of the GI tract (heteroreceptors)
248
Q

What is the MOA of alpha 2 receptors?

A

Inhibit or even block intracellular cAMP.

249
Q

What are the physiological actions of alpha 2 receptors?

A

-mainly inhibitory

a) Presynaptic
➒ negative feedback inhibition of more NA release.

b) Postsynaptic
➒ CNS inhibition.
➒ Peripheral platelet aggregation
➒ Vasoconstriction of some vessels.
➒ Decreased lipolysis.
➒ Decreased insulin secretion.

250
Q

What is the site of beta 1 receptors?

A

1- Heart.
2- Juxtaglomerular cells.
3- Intestine and fat cells

251
Q

What is the MOA of beta 1 receptors?

A

Activate adenyl cyclase →↑intracellular cAMP within the cell, initiating many intracellular activities.

252
Q

What are the physiological actions of beta 1 receptors?

A

-Mainly excitatory:-
➒ Increased all cardiac properties (increased heart rate, increased contraction force, increased conduction velocity, increased excitability).
➒ Increased renin secretion
➒ Increased lipolysis.
➒ Decreased platelet aggregation

253
Q

What are the sites of beta 2 receptors?

A

Widely distributed in the body.

254
Q

What is the MOA of beta 2 receptors?

A

Activate adenyl cyclase →↑intracellular cAMP within the cell, initiating many intracellular activities.

255
Q

What are the physiological actions of beta 2 receptors?

A

Mainly inhibitory (GIF)
➒ Smooth muscle relaxation e.g. intestinal, bladder, uterine relaxation, vasodilatation, bronchodilatation.
➒ Stimulation of liver and muscle glycogenolysis.
➒ Stimulation of pancreatic insulin secretion.
➒ Increased blood fibrinogen level

256
Q

what contributes to the vasoconstriction of vessels?

A

Alpha 1 and alpha 2 but alpha 1 mainly

257
Q

What dec and inc lipolysis respectively?

A

Alpha 2

Beta 1 and beta 3

258
Q

What affects platelet aggregation?

A

Alpha 2 inc

Beta 1 dec

259
Q

What is the effect of hyperkalemia on membrane potential?

A

i) Mild hyperkalemia: decrease K efflux β†’ decrease the negativity of RMP i.e. less than - 70 mV (e.g. – 60 mV)→↑ excitability of nerve fibers

ii) Marked hyperkalemia: make the resting membrane potential to be more negative β†’ inactivation of Na channels by h gates which close within 0.5 -1.0 m.sec of opening of m gate β†’ decrease membrane excitability

260
Q

What is the number of neurons?

A

1 trillion

261
Q

What is the function of neuroglia?

A

Support & protect neurons.

262
Q

What is the number of neuroglia?

A

10: 50 times more than neuron

263
Q

CHARACTERISTICS of interneurons

A

ο‚· Small size.
ο‚· Inside CNS.
ο‚· 99% of neurons.
ο‚· Integrative function
ο‚· Connect afferents with efferents.

264
Q

What are the characters of the cell body?

A

ο‚· Enlarged part of the nerve that contains Contain nucleus, microfilament, and microtubule.
ο‚· Control metabolism and nutrition of nerve fibers.

265
Q

What is a collection of cell bodies called?

A

ο‚· Collection of cell bodies inside CNS called: centre = synapse = nucleus
ο‚· Collection of cell bodies outside CNS called: ganglia.

266
Q

What are the cell processes?

A

a) Axon (axis cylinder).
b) Dendrites.

267
Q

What are the characters of myelin or medullary sheath?

A

ο‚· Lipoprotein complex.
ο‚· Electric insulator.
ο‚· White in color
ο‚· Envelop all axon except axon terminal and nodes of ranvier
ο‚· Interrupted at every (.1-1mm) which is the site of exchange of ions and water.

268
Q

What are the characters of Schwan or cellular sheath?

A

ο‚· Not found inside CNS.
ο‚· Glia like.
ο‚· Its outer layer is called neurolemma.
ο‚· Regenerate damaged nerve fiber by the formation of the myelin sheath, only outside CNS.

269
Q

What is the nerve trunk formed from?

A

οƒ˜ Formed of multiple nerve fibers.
οƒ˜ Bundles of nerve fibers are surrounded by perineurium
οƒ˜ Inside the bundles: each nerve fiber is surrounded by endoneurium.
οƒ˜ The nerve is surrounded by loose connective tissue called epineurium and supplied by blood vessels.

270
Q

What is the function of the nerve trunk?

A

a) Sensory nerve: carry sensation from receptor to CNS.
b) Motor nerve: carry motor orders from CNS to the effector organ.

271
Q

What happens to action potential after it is initiated?

A

After action potential is initiated, it propagates along the axon from the region of the initial segment down to the terminal ending, in order to transfer information from one place in the nervous system to the other.

272
Q

What is the function of action potential?

A

in order to transfer information from one place in the nervous system to the other.

273
Q

What are nerve fibres classified according to?

A

according to their diameter into:

-Type A
-Type B
-Type C

274
Q

What is the diameter of type A?

A

the largest diameter (3- 20 microns)

275
Q

What is the speed of type A nerve fibres?

A

οƒœ highest speeds of conduction (for quick actions)
οƒœ (15-120 meters/ second).

276
Q

What is An example of Type A nerve fibres?

A

somatic nerve fibers that transmit motor impulses and deep sensations

277
Q

What is Type A nerve fibres sensitive to?

A

Most sensitive to pressure (by surrounding tissue for example)(the conduction of impulses in these nerves blocked by pressure).

278
Q

What is the diameter of Group B nerve fibres?

A

smaller diameters (1.3-3 microns)

279
Q

What is the speed of Group B nerve fibres?

A

moderate speeds of conduction (3-15 meters/ second)

280
Q

What is the example of Group B nerve fibres?

A

myelinated preganglionic autonomic nerves

281
Q

What is Group B nerve fibres sensitive to?

A

Most sensitive to O2 lack.

282
Q

What is the diameter of Group C nerve fibres?

A

Have the smallest diameter

283
Q

What is the speed of Group c nerve fibres?

A

slowest speeds of conduction (0.5-3 meters/second) (as they are unmyleinated)

284
Q

What is an example of Group C nerve fibres?

A

unmyelinated postganglionic autonomic nerves

285
Q

What are Group c nerve fibres sensitive to?

A

Most sensitive to local anesthetic drugs

286
Q

What are Group A nerve fibres subdevided into?

A

Subdivided into alpha, beta, gamma and delta nerve fibers.

287
Q

What are the steps of Continous induction in unmyelinated nerve fibres?

A

 The initial stimulus causes reversal of polarity and action potential at point of stimulation.

 Local circular currents flow between the activated point and neighboring inactive areas

 + ve charges from inactive areas flow into initial area of negativity produced by action potential (AP). This decreases polarity at the inactive areas (electrotonic depolarization) which produces AP on reaching firing level.

 The latter areas, in turn, electrotonically depolarize the membrane in front of it through local circular currents, this sequence of events moves regularly along nerve fiber to its end.

 Therefore, nerve impulse is self-propagated and once it leaves a point, this point will soon repolarize (thus a repolarization wave starts after depolarization wave and is propagated in the same direction).

288
Q

What are the steps of salutatory conduction in myelinated nerve fibres?

A

 Myelin surrounds the nerve axon and is interrupted at regular intervals at nodes of Ranvier.

 It is an insulator to current flow (in contrast to nodes of Ranvier, which easily permit current flow because of their high permeability to Na+).

 Circular currents also flow in myelinated nerve fibers, but +ve charges jump from inactive nodes to active nodes (bypassing myelin segments because of their insulator effect) .

289
Q

What are the charachteristcs of salutatory induction?

A

(a) Increasing velocity of conduction.
(b) Conservation of energy (because excitation occurs only in the nodes
and not all over the nerve membrane

290
Q

What does β€œnerve block” mean?

A

o It means failure of conduction of nerve impulses from one place to another. o It also means failure of excitability of the nerve fibers i.e. there is no
generation or propagation of nerve impulses.

291
Q

What are the methods of nerve block?

A
  1. Physical methods: -Severe cooling.
  2. Mechanical methods:
     Application of pressure on the nerve
     Injury or crushing of the nerve fibers.
  3. Chemical methods:
    (a)Ionic changes that decrease nerve excitability: Increased Ca2+ and decreased Na+ or K+ concentration in extracellular fluid.

(b)Local anesthetic drugs (e.g. cocaine and novocaine): These drugs markedly decrease membrane permeability to Na+ (by preventing opening of Na+ channel activation gates), so depolarization process is inhibited and nerve impulses fail to be produced.

Y1B2 (PPMIP & PPP) πŸ“— (7 decks)

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