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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
What are the examples of positive feedback?
- 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.
26
What is the cell membrane?
Very thin elastic semi-permeable membrane (allowing some substances to pass through it and prevent others) that surrounds the cell.
27
What is the thickness of the cell membrane?
: 7-9nm (70 - 90 Ao = Angstrom = 10-10 of meter)
28
What is the function of the cell membrane?
« STM GRC » 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.
29
What is the structure of the cell membrane?
Lipids: 42% Proteins: 55% Carbohydrates: 3%
30
Lipids in the cell membrane
-They form the basic structure of the membrane. Include: 1. Phospholipids. 2. Cholesterol. 3. Glycolipids.
31
What are the types of proteins in the cell membrane?
1. Integral or intrinsic proteins 2. Peripheral or extrinsic proteins
32
What is the site of integral or intrinsic proteins?
β€’ Bind to the hydrophobic center of the lipid bilayer.
33
What are the types and functions of integral or intrinsic proteins?
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
34
What is the site of peripheral or extrinsic proteins?
Bind to hydrophilic polar heads of lipids or to integral proteins.
35
What are the types of peripheral or extrinsic proteins?
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.
36
What are the protein ion channels?
They are protein channels that allow the passage of ions e.g. Na+ ion through the cell membrane.
37
What are the types of protein ion channels?
1- leak ion channel 2- chemical-gated ion channels 3- voltage-gated ion channels
38
What is the definition of leak ion channels?
Channels that are always open
39
What are examples of leak ion channels?
K channels
40
What is the importance of the leak ion channel?
Resting membrane potential
41
What is the definition of chemical-gated ion channels?
Channels open when a chemical substance bind to its receptor
42
What are examples of chemical-gated ion channels?
K & Na channel at NMJ.
43
What is the importance of chemical-gated ion channels?
Graded membrane potential e.g. motor endplate potential
44
What is the definition of voltage-gated ion channels?
Channels open by changes in cell membrane potential
45
What are examples of voltage-gated ion channels?
Na & K channels
46
What is the importance of voltage-gated ion channels?
Action potential
47
What is the definition of diffusion?
Movement of substances across the cell membrane down its electrochemical gradient due to the continuous random motion of its particles.
48
What are the types of transporting across the cell membrane?
- Diffusion - Active transport - vesicular transport
49
What are the types of diffusion?
Simple, facilitated, and osmosis.
50
What is the definition of simple diffusion?
Movement of substances across cell membrane down its electrochemical gradient by simple movement without the necessity of binding with carrier proteins.
51
What are the characters of the simple diffusion?
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.
52
What are the mechanisms of simple diffusion?
-Interstices of the lipid bilayer e.g. diffusion of O2, nitrogen, CO2, and alcohol. -Watery proteins channels e.g. diffusion of ions
53
What is the definition of facilitated diffusion?
As simple diffusion but it needs the presence of carrier proteins.
54
What are the examples of facilitated diffusion?
Transport of glucose into the cells.
55
What is the definition of osmosis?
The passive flow of water across a semi-permeable membrane down a concentration gradient of water
56
What are examples of osmosis?
from high concentration of water to low concentration of water or low concentration of solute to high concentration of solute.
57
What are the Factors affecting Net Rate of Diffusion (Fick’s Law)?
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.
58
What is the definition of active transport?
Movement of substances across cell membranes against an electrochemical gradient.
59
What are the characters of active transport?
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
60
What are the types of active transport?
Primary and secondary.
61
Primary active transport
Use energy directly from ATP hydrolysis
62
What are examples of primary active transport?
Na-K Pump, Ca ATPase Pump , H-k Pump
63
Sodium-potassium pump (Na+-K+ ATPase) :
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
64
Secondary active transport
Use energy generated by sodium gradient created by Na-K pump e.g. Na-Ca exchanger and Na-glucose cotransport
65
What is the definition of vesicular transport?
The mechanism by which the large-sized substances can cross the cell membranes.
66
What are the types of vesicular transport?
- Endocytosis and exocytosis
67
What is the definition of endocytosis?
The extracellular material is trapped within vesicles that are formed by the invagination of the cell membrane and pushed inside the cell.
68
What are the types of endocytosis?
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
69
What is the definition of exocytosis?
the intracellular material is trapped within vesicles, then the vesicles fuse with the cell membrane and release their contents to the ECF.
70
What are the examples of exocytosis?
release of hormones, digestive enzymes, and synaptic transmitters
71
What is the origin of Sympathetic Supply to the Head and Neck?
LHCs of first and second thoracic segments
72
What is the relay of the LHCs of the first and second thoracic segments?
Superior cervical ganglion (SCG)
73
What are the parts affected by the sympathetic supply to the head and neck?
-Eye -Salivary glands -Skin -Cerebral blood vessels
74
Effect of sympathetic supply to the eye
a. Contraction of dilator pupillae msβ†’ dilatation of pupil (mydriasis) b. Contraction of smooth ms in eyelids (Tarsal ms) leading to elevation of upper and lowering of lower eyelidsβ†’ 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.
75
Effect of sympathetic supply to the salivary glands
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.
76
Effect of the sympathetic supply to the skin
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.
77
Effect of the sympathetic supply to cerebral blood vessels
Mild vasoconstriction (V.C.).
78
What is the definition of Horner’s syndrome?
It is a group of signs which result from interruption sympathetic to the head and neck.
79
What are the causes of Horner’s syndrome?
a. Lesion in T1 and T2 segments. b. Lesion in SCG disease or experimentally by section in the cervical sympathetic chain.
80
What is the site of Horner’s syndrome?
Manifestations occur at the same side of the lesion.
81
What are the signs of Horner’s syndrome?
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.
82
What is the origin of sympathetic supply to the thorax?
β€’ LHCs of upper 4 or 5 thoracic segments of the spinal cord.
83
What is the relay o the sympathetic supply to the thorax?
β€’ 3 cervical ganglia and upper 4 thoracic ganglia.
84
What is the sympathetic supply to the thorax directed to?
Heart and lungs
85
What is the function of the sympathetic supply to the thorax?
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.
86
What is the origin of the sympathetic supply to the abdomen?
LHCs of T6-T12 segments of the spinal cord (splanchnic nerves).
87
What is the relay of the sympathetic supply to the abdomen?
β€’ collateral (prevertebral) ganglia (celiac, superior mesenteric, aortico-renal).
88
What what are the organs that are affected by the sympathetic supply to the abdomen?
1- GIT 2- Liver 3- Gall bladder 4- Pancreas 5- Spleen 6- Blood vessels 7- Kidneys 8- SRM
89
What is the effect of sympathetic supply on the GIT?
(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.
90
What is the effect of the sympathetic supply on the liver?
β€’ Stimulation of glycogenolysis β†’ ↑ed blood glucose. β€’ Stimulation of fibrinogen synthesis.( for blood clotting)
91
What is the effect of the sympathetic supply on the gall bladder?
β€’ Relaxation of its wall and contraction of sphincter of Oddi β†’ retention of bile and delayed emptying of gall bladder.
92
What what is the effect of the sympathetic supply on the spleen?
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.
93
What is the effect of the sympathetic supply on the pancreas?
β€’ It inhibits both endocrine and exocrine pancreatic secretion.
94
What is the effect of the sympathetic supply on the blood vessels?
β€’ Mixed supply (vasoconstriction and vasodilatation)
95
What is the effect of the sympathetic supply to the kidneys?
β€’ Stimulation of juxtaglomerular cells β†’ ↑ed renin secretion. β€’ ↓es renal blood flow. β€’ ↓es urine output.
96
What is the origin of the sympathetic supply to the SRM?
β€’ LHCs of T10 and 11segments of the spinal cord.
97
What is the relay of the sympathetic supply to the SRM?
β€’ SRM is supplied by sympathetic preganglionic nerve fibers (with no postganglionic nerve fibers) which relay directly with the SRM cells (chromaffin cells).
98
What is the function of the sympathetic supply to the SRM?
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.
99
What is the function of both adrenaline and noradrenaline?
‒ Adrenaline → acts more on metabolic actions of the body while noradrenalin→acts more on blood vessels.
100
What happens in stress conditions regarding SRM and the sympathetic nervous system?
In stress conditions, SRM acts together with the sympathetic nervous system (sympathoadrenal system).
101
What is the origin of the sympathetic supply to the pelvis?
LHCs of L1, L2, and L3 segments of the spinal cord.
102
What is the relay of the sympathetic supply to the pelvis?
β€’ Inferior mesenteric or hypogastric ganglia.
103
What are the organs affected by the sympathetic supply to the pelvis?
Urinary bladder, rectum, and sex organs.
104
What are the functions of the sympathetic supply to the pelvis on the Urinary bladder?
Relaxation of its wall and contraction of internal urethral sphincter β†’ urine retention.
105
What is the effect of sympathetic supply to the rectum?
‒ Relaxation of its wall and contraction of internal anal sphincter→ retention of feces.
106
What is the effect of the sympathetic supply on sex organs?
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.
107
What is the origin of the sympathetic supply to the somatic structures?
􏰀 Upper limb from LHCs of T2-9. 􏰀 Lower limb from LHCs of T10-L2. 􏰀 Thoracic and abdominal walls from LHCs of T1-L2.
108
What is the function of the sympathetic supply to the somatic structures?
1- Skin 􏰀 VC of blood vessels. 􏰀 Hair erection. 􏰀 Sweat secretion. 2-Skeletal muscles 􏰀 VD of skeletal muscle blood vessels.
109
What is the Orbelli phenomenon?
-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.
110
What provides most of the control function over our bodies?
The nervous system
111
What does the nervous system do?
It receives thousands of information from different sensory organs and analysis all of them to determine the response to be made by the body.
112
What is the neuron?
It is the structural or anatomical unit of the nervous system.
113
What is the neuron formed from?
It is formed from the cell body and cell processes.
114
What is the function of the cell body of the neuron?
Controls the activity of the whole neuron.
115
What are the processes of the neuron?
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
116
Near the termination of the axon, what does it join?
-Muscleβ€”-> neuro-muscular junction -Glandβ€”β€”> neuro-epithelial junction -Another neuron----> neuro-neural junction
117
What are the types of neurons?
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
What is reflex action?
Reflex action is the involuntary (programmed) response of a part of the body to a stimulus.
119
How is reflex action carried out?
- Reflex action is carried out through a pathway called the reflex arc.
120
What is the functional or physiological unit of the nervous system?
Reflex action
121
What are the components of the reflex pathway?
1. Receptors. 2. Afferent (sensory). 3. Center (in CNS). 4. Efferent (motor). 5. Effectors (muscles or glands).
122
What are the divisions of the nervous system?
-CNS -PNS
123
What is the definition of the central nervous system?
-It is the part of the nervous system which is protected by bone (skull and vertebral column).
124
What are the parts of the CNS?
-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
What is the function of the peripheral nervous system?
The peripheral nervous system provides communication between the CNS and other tissues via nerves (PNS).
126
What are the divisions of the PNS?
They are classified anatomically (cranial and spinal) and physiologically (somatic and autonomic)
127
What are the divisions of the PNS according to anatomical classification?
1- 12 pairs of cranial nerves. 2- 31 pairs of spinal nerves.
128
Cranial nerves
- 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
What are the purely sensory cranial nerves?
I - II - VIII Fiat β€œ128”
130
What are the purely motor cranial nerves?
III - IV - VI β€œ346”
131
What are the mixed cranial nerves?
Anything except 128 and 346
132
Spinal nerves
- 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
What is the peripheral nervous system classified into physiologically?
Somatic and autonomic
134
Somatic nervous system
Voluntary - Connected With (skin, Skeletal muscles, tendons, bones, and joints)
135
Autonomic nervous system
Involuntary - Connected With (Smooth muscles, glands, and cardiac muscle).
136
What is the origin of the sympathetic NS?
- Originates from LHCs of all thoracic and upper 3 lumbar segments of the spinal cord.
137
What is the origin of the parasympathetic NS?
- 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
What is the origin and relay of the oculomotor nerve?
-Edinger Westphal nucleus in the midbrain -Ciliary ganglion
139
What is the origin and relay of the facial nerve?
-Superior salivary nucleus in the pons -1. Greater superficial petrosal branch→ Sphenopalatine(petrosal) ganglion. 2. Chorda tympani branch →Submandibular ganglion
140
What is the origin and relay of the glossopharyngeal nerve?
-Inferior salivary nucleus in the medulla oblongata. -Otic ganglion
141
What is the origin and relay of the vagus nerve?
-Dorsal motor nucleus of vagus in the medulla oblongata -Terminal ganglion
142
What is the origin and relay of the pelvic nerve?
-Sacral segments (S2,3,4) and preganglionic nerve fibers unit together to form pelvic nerve or nervous erogenous. -Terminal ganglia
143
What is the function of the parasympathetic supply by the oculomotor nerve?
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
Why is parasympathetic stimulation important in near vision like reading?
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
What is the function of the parasympathetic supply by the facial nerve?
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
What is the function of the parasympathetic supply by the glossopharyngeal nerve?
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
What are the nerves responsible for parasympathetic supply to the head and neck?
i) Oculomotor nerve ii) Facial nerve iii) Glossopharyngeal nerve
148
What are the organs affected by the parasympathetic supply of the vagus nerve?
-Thorax (heart and lungs) -Abdomen (GIT, Glands, Liver, Gall bladder, and blood vessels)
149
What is the function of the parasympathetic supply of the vagus nerve at the heart?
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
What is the function of the parasympathetic supply of the vagus nerve at the Lungs?
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
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)?
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
What is the function of the parasympathetic supply of the vagus nerve at the glands?
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
What is the function of the parasympathetic supply of the vagus nerve at the Liver?
It ↑es hepatic bile flow.
154
What is the function of the parasympathetic supply of the vagus nerve at the gall bladder?
Contraction of its wall and relaxation of the sphincter of Oddi β†’ help its evacuation.
155
What is the function of the parasympathetic supply of the vagus nerve at the blood vessels?
Vasodilatation
156
What is the function of the parasympathetic supply by the pelvic nerve at the urinary bladder?
Contraction of its wall and relaxation of internal urethral sphincter β†’ micturition.
157
What are the organs affected by the parasympathetic supply of the pelvic nerve?
Urinary bladder, rectum, and sex organs
158
What is the function of the parasympathetic supply by the pelvic nerve at the Rectum?
Contraction of its wall and relaxation of internal anal sphincter β†’ defecation.
159
What is the function of the parasympathetic supply by the pelvic nerve at the Sex organs?
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
Are the external anal and urethral sphincters voluntary or involuntary?
They are voluntary ms supplied by the somatic spinal pudendal nerve.
161
What are the organs that have sympathetic supply only?
1) Dilator pupillae muscle 2) Muller's muscle. 3) Cutaneous effectors 4) Ventricles of the heart. 5) Spleen 6) Adrenal medulla
162
What are the organs that are affected by the parasympathetic supply only?
1) Constrictor pupillae muscle 2) Upper esophagus. 3) Glands of stomach
163
What are the types of relations between sympathetic and parasympathetic nervous systems?
-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
What are the types of membrane potentials?
-RMP -GRADED POTENTIAL -ACTION POTENTIALv
165
What is the graded potential?
-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
What are examples of graded potential?
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
What is action potential?
-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
What is RMP?
It is the potential difference between the outside and inside of the nerve fiber during rest.
169
Where is RMP present?
RMP is present in nerves, muscle fibers, and all cells of the body with the inside negative relative to outside.
170
What are the values of RMP?
It varies according to the excitable tissue: Nerves -70 mV. Skeletal muscles -90 mV Cardiac muscle -90 mV Smooth muscles -60 mV
171
How is RMP measured?
-By two microelectrodes connected with a special voltmeter. -One of these microelectrodes is inserted inside the nerve fiber.
172
What are the causes of RMP?
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
What are the substances that pass the membrane by selective permeability?
-proteins -K+ -Na+ -Cl-
174
Selective permeability of proteins
Cell membranes are impermeable to intracellular protein anions (because of their large size).
175
Selective permeability of K+
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
Selective permeability of Na+
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
Selective permeability of Cl-
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
What is the concentration of ions inside and outside of the cell?
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
What are the three basic types of ion channels?
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
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Na+-K+ Pump
 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
What does Na- K Pump have?
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
What happens during equilibrium regarding the membrane potential?
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
What happens if a condition decreases metabolic activity like cooling?
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
What is the definition of a synapse?
It is the functional connection between a neuron and a second cell (neuron or muscle or glands)
185
What is the structure of a synapse?
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 →is full of interstitial fluid which separates the nerve ending from the next neuron or effector organ.
186
What is the definition of the electrical synapse?
Is a gap junction between the presynaptic membrane and postsynaptic membrane.
187
Is the electrical synapse common or rare?
Rare
188
What is the function of electrical synapses?
It allows direct transmission of the electrical depolarization waves from the presynaptic to the postsynaptic neuron
189
What is the definition of chemical synapses?
It is a junction between the presynaptic and postsynaptic membrane which is chemically mediated.
190
Are chemical synapses common or rare?
Common
191
What is the function of chemical synapses?
A chemical substance is released at the nerve endings which allows the transmission of nerve impulses from one neuron to another neuron.
192
What are the types of chemical transmitters?
-Types of chemical transmitters: chemical transmitters released by autonomic nerve endings include : a) acetylcholine. b) noradrenaline
193
What are the types of nerve endings?
a) Cholinergic nerve fibers: secrete acetylcholine. b) Adrenergic nerve fibers: secrete noradrenaline
194
What are the sites of the release of acetylcholine?
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
How is ach biosynthesized?
Ach is formed by a reaction between choline and acetyl CoA as follow; ATP Acetyl CoA + choline --------------------- > acetylcholine + CoA NB:- -CAT (choline acetyltransferase) - ATP and glucose are required to form acetyl CoA.
196
Where is ach stored?
- 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
How is ach released?
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
What is the mechanism of action of ach?
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
How is ach removed?
A-Hydrolysis of Ach by cholinesterase enzyme B- Diffusion C- Reuptake of Ach
200
-Hydrolysis of Ach by cholinesterase enzyme:
Acetylcholine choline is hydrolyzed by cholinesterase to give acetic acid and Choline
201
What is the action of choline?
Choline has a similar action to acetylcholine but is weaker.
202
Which of choline and the acetate ion and choline is reputakable and which one diffuses?
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
-diffusion of ach
- Small part of Ach escapes to the surrounding tissues→↓ed Ach concentration.
204
-Reuptake of ach
- is not yet definite
205
What is the function of cholinesterases?
-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
What are the function of anticholinesterases and an example for them?
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
What is the action of acetylcholine?
Ach has two main types of actions: Muscarinic and Nicotinic
208
comparison between muscarinic and nicotinic actions
Acc to SSODA -Similar to the action of -Site -Onset -Duration -Antagonist
209
What is the muscarinic action of acetylcholine similar to?
Muscarine, an alkaloid, derived from poisonous Mushroom
210
What is the site of the muscarinic action of acetylcholine?
On smooth ms and glands - supplied by parasympathetic and Sympathetic cholinergic nerve fibers
211
What is the onset of their muscarinic action of acetylcholine?
Slow
212
What is the duration of the muscarinic action of acetylcholine?
Prolonged
213
What is the antagonist of the muscarinic action of acetylcholine?
Atropine
214
What is the nicotinic action of acetylcholine similar to?
Nicotine which is derived from Tobacco
215
What is the site of the nicotinic action of acetylcholine?
- autonomic ganglia and neuromuscular junction - (contraction of skeletal ms, stimulation of ganglia, secretion of adrenaline and noradrenaline from
216
What is the onset of the nicotinic action of acetylcholine?
Rapid
217
What is the duration of the nicotinic action of acetylcholine?
Short
218
What is the antagonist of the nicotinic action of acetylcholine?
ganglion and neuromuscular blockers
219
What are cholinergic receptors?
They are the receptors that respond to Ach.
220
Compare between muscarinic and nicotinic receptors
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
What is the definition of the action potential?
- 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
What are the components of the action potential?
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
What is the definition of depolarization?
It is a loss of the normal resting polarized state of the membrane.
224
What is the ionic basis of depolarization?
-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
Which Na+ Gates are open during resting state and what does this cause?
In the resting state, only the inactivation gates of Na+ channels are open, so the membrane permeability to Na+ is low.
226
Which Na+ gates are open when the nerve is stimulated?
When the nerve is stimulated, the Na+ activation gates also open thus the membrane permeability to Na+ and Na+ influx markedly increased
227
What is the definition of depolarization?
-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
What are the steps of repolarization?
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
What is the ionic basis of repolarization?
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
What is the compound action potential?
This is the AP recorded from peripheral nerves when stimulated by maximal stimuli.
231
In Which type of nerve fibers is the conduction the fastest?
-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
What is noradrenaline?
The chemical transmitter of the sympathetic nervous system.
233
What are catecholamines?
1. Noradrenaline. 2. Adrenaline. 3. Dopamine.
234
What are the sites of the release of catecholamines?
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
How is catecholamine synthesized?
- 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
Where is dopamine present in higher conc. Than noradrenaline?
In basal ganglia of the brain
237
Where are catecholamines stored?
- 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
How is catecholamine released?
- 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
What is the mechanism of action of Noradrenaline?
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 β†’ conversion of ATP into cAMPβ†’ initiates many intracellular activities.
240
How is noradrenaline removed?
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
Compare between MOA and COMT in terms of: Name: Site of uptake: Type of process: Amount removed: Sites:
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
What is the definition of adrenergic receptors?
adrenergic receptors are receptors that respond to NA and adrenaline.
243
What is the classification of adrenergic receptors?
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 Ξ²4 and Ξ²5 receptors: under research.
244
What are the sites of alpha 1 receptors?
-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
What is the mechanism of action of alpha 1 receptors?
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
What are the physiological actions of alpha 1 receptors?
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
What are the sites of alpha 2 receptors?
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
What is the MOA of alpha 2 receptors?
Inhibit or even block intracellular cAMP.
249
What are the physiological actions of alpha 2 receptors?
-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
What is the site of beta 1 receptors?
1- Heart. 2- Juxtaglomerular cells. 3- Intestine and fat cells
251
What is the MOA of beta 1 receptors?
Activate adenyl cyclase →↑intracellular cAMP within the cell, initiating many intracellular activities.
252
What are the physiological actions of beta 1 receptors?
-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
What are the sites of beta 2 receptors?
Widely distributed in the body.
254
What is the MOA of beta 2 receptors?
Activate adenyl cyclase →↑intracellular cAMP within the cell, initiating many intracellular activities.
255
What are the physiological actions of beta 2 receptors?
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
what contributes to the vasoconstriction of vessels?
Alpha 1 and alpha 2 but alpha 1 mainly
257
What dec and inc lipolysis respectively?
Alpha 2 Beta 1 and beta 3
258
What affects platelet aggregation?
Alpha 2 inc Beta 1 dec
259
What is the effect of hyperkalemia on membrane potential?
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
What is the number of neurons?
1 trillion
261
What is the function of neuroglia?
Support & protect neurons.
262
What is the number of neuroglia?
10: 50 times more than neuron
263
CHARACTERISTICS of interneurons
ο‚· Small size. ο‚· Inside CNS. ο‚· 99% of neurons. ο‚· Integrative function ο‚· Connect afferents with efferents.
264
What are the characters of the cell body?
ο‚· Enlarged part of the nerve that contains Contain nucleus, microfilament, and microtubule. ο‚· Control metabolism and nutrition of nerve fibers.
265
What is a collection of cell bodies called?
ο‚· Collection of cell bodies inside CNS called: centre = synapse = nucleus ο‚· Collection of cell bodies outside CNS called: ganglia.
266
What are the cell processes?
a) Axon (axis cylinder). b) Dendrites.
267
What are the characters of myelin or medullary sheath?
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
What are the characters of Schwan or cellular sheath?
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
What is the nerve trunk formed from?
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
What is the function of the nerve trunk?
a) Sensory nerve: carry sensation from receptor to CNS. b) Motor nerve: carry motor orders from CNS to the effector organ.
271
What happens to action potential after it is initiated?
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
What is the function of action potential?
in order to transfer information from one place in the nervous system to the other.
273
What are nerve fibres classified according to?
according to their diameter into: -Type A -Type B -Type C
274
What is the diameter of type A?
the largest diameter (3- 20 microns)
275
What is the speed of type A nerve fibres?
οƒœ highest speeds of conduction (for quick actions) οƒœ (15-120 meters/ second).
276
What is An example of Type A nerve fibres?
somatic nerve fibers that transmit motor impulses and deep sensations
277
What is Type A nerve fibres sensitive to?
Most sensitive to pressure (by surrounding tissue for example)(the conduction of impulses in these nerves blocked by pressure).
278
What is the diameter of Group B nerve fibres?
smaller diameters (1.3-3 microns)
279
What is the speed of Group B nerve fibres?
moderate speeds of conduction (3-15 meters/ second)
280
What is the example of Group B nerve fibres?
myelinated preganglionic autonomic nerves
281
What is Group B nerve fibres sensitive to?
Most sensitive to O2 lack.
282
What is the diameter of Group C nerve fibres?
Have the smallest diameter
283
What is the speed of Group c nerve fibres?
slowest speeds of conduction (0.5-3 meters/second) (as they are unmyleinated)
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What is an example of Group C nerve fibres?
unmyelinated postganglionic autonomic nerves
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What are Group c nerve fibres sensitive to?
Most sensitive to local anesthetic drugs
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What are Group A nerve fibres subdevided into?
Subdivided into alpha, beta, gamma and delta nerve fibers.
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What are the steps of Continous induction in unmyelinated nerve fibres?
 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).
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What are the steps of salutatory conduction in myelinated nerve fibres?
 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) .
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What are the charachteristcs of salutatory induction?
(a) Increasing velocity of conduction. (b) Conservation of energy (because excitation occurs only in the nodes and not all over the nerve membrane
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What does β€œnerve block” mean?
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.
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What are the methods of nerve block?
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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