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Principles > Physiology > Flashcards

Physiology Flashcards

1
Q

What is homeostasis defined as?

A

The maintenance of steady states within our bodies by coordinated physiological mechanisms.

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2
Q

Explain the difference between the parasympathetic and the sympathetic nervous system

A

The parasympathetic nervous system (PNS) controls homeostasis and the body at rest and is responsible for the body’s “rest and digest” function. The sympathetic nervous system (SNS) controls the body’s responses to a perceived threat and is responsible for the “fight or flight” response.

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3
Q

Define blood pressure

A

The outwards pressure (hydrostatic) exerted by the blood on blood vessel walls.

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4
Q

Define Systemic Systolic Arterial Blood Pressure

A

The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts. This is normally <140 mm Hg under resting conditions.

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5
Q

Define Systemic Diastolic Arterial Pressure

A

The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes. This is normally <90 mm Hg.

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6
Q

What is hypertension defined as?

A

Clinic blood pressure of 140/90 mmHg or higher and day time average of 135/85 mmHg or higher. Patients may be asked to take a daily measure and average as could be anxious when they visit the clinic resulting in misrepresentation.

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7
Q

Define Pulse pressure

A

The difference between systolic and diastolic blood pressures. Normally between 30 and 50.

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8
Q

Define Mean Arterial Blood Pressure

A

The average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart.

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9
Q

How is MAP obtained and why not in another way?

A

MAP = [(2x Diastolic) + Systolic] divided by 3

It is not obtained by averaging the systolic and diastolic pressures because during a normal cardiac cycle, the relaxation (Diastolic) portion of the cardiac cycle is about twice as long as the contraction (Systolic) portion of the cardiac cycle.

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10
Q

Define Stroke Volume

A

The volume of blood pumped by each ventricle of the heart per heart beat.

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11
Q

Define the Cardiac Output

A

Simply the amount of blood pumped by each ventricle of the heart per minute.

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12
Q

Define Systemic Vascular Resistance

A

The sum of resistance of all vasculature in the systemic circulation.

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13
Q

What is the minimum MAP required to perfuse the brain, heart and kidneys?

A

60 mm Hg

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14
Q

What are acute changes in blood pressure controlled by?

A

The Baroreceptor reflex

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15
Q

Where is the cardiovascular control centre?

A

Medulla of the brain stem

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16
Q

What process happens if there is reduced blood pressure?

A

Reduction in blood pressure will result in a decrease in the number of afferent impulses from the baroreceptors. The sympathetic activity will increase and as a result, the SVR, HR and the stroke volume will all increase. Decrease in vagal activity (parasympathetic nerve). All these changes will result in increasing the blood pressure back to normal.

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17
Q

What happens if there is increased blood pressure?

A

This happens in situations like exercise or stress. Increased blood pressure will result in stretching of the stretch receptors. This increases the frequency of afferent impulses. Increase in vagal activity (parasympathetic nerve). Finally, the blood pressure is decreased back to normal.

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18
Q

What is meant by vasomotor tone

A

The muscles of blood need to be given constant nervous stimulation to maintain a resting level of contraction. This phenomenon is known as vasomotor tone.

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19
Q

What does pulse consist of?

A

Heart rate (normal resting HR 60-100 beats/min), rhythm, volume and character.

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20
Q

What is normal resting respiratory rate?

A

12-20 breaths/min

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21
Q

What is normal capillary refill time?

A

<2 seconds.

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22
Q

What is normal oxygen saturation?

A

> 95%.

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23
Q

What is normal core body temperature?

A

37.8 degrees celsius

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24
Q

What would extreme changes in core temperature result in?

A

Extreme increases in temperatures would cause protein denaturation, nerve malfunctions, convulsions and death. Extreme decreases would slow down cellular reactions to a fatal length.

25
Q

What types of thermometer are used in clinical practice and why?

A

Tympanic (ear drum) thermometers are commonly used in clinical practice. Rectal thermometers can be important in extremes of body temperature as they are more accurate.

26
Q

What are methods of heat gain?

A 
Metabolic heat (internal environment, main way)
Radiation (external environment, most important of external methods)
Convection (external environment)
Conduction (external environment)
27
Q

What are methods of heat loss?

A 
All to the external environment:
Convection 
Conduction
Radiation
Evaporation
28
Q

What is activated by cold and what is the response?

A

The posterior hypothalamic centre is activated by cold, the response is:
• Vasoconstriction- contraction of the arterioles’ smooth muscles means blood flow to the skin’s surface is reduced so less heat is lost.
• Shivering thermogenesis- skeletal muscles contract in synch in order to generate heat.
• Increased muscle tone- erector pili muscles contracted in order to trap a layer of warm air.
• Increased voluntary movement- to generate heat.
• Behaviour adaptions- warm clothing, postural changes to reduce surface area available to cold.

29
Q

What is activated by warmth and what is the response?

A

The anterior hypothalamic centre is activated by warmth:
• Vasodilation- arterioles’ smooth muscles relax resulting in increased blood flow to the skin surface and more heat being lost.
• Sweating- evaporation of sweat from skin surface results in increased heat loss.
• Skeletal muscles- decreased muscle tone, decreased voluntary movement.
• Behaviour adaptations- cool clothing.

30
Q

What happens in fever?

A

The hypothalamic temperature set point is raised.

31
Q

Define hyperthermia

A

Extreme uncontrolled increase in body temperature (temperature above 40)

32
Q

Define hypothermia

A

Drop in body temperature below that required for cellular metabolism and function (below 35)

33
Q

What does cholesterol do in the cell membrane?

A

Aids in stiffening the membrane and adds rigidity.

34
Q

How do phospholipids differ from one another and how are they similar?

A

They all have a glycerol backbone but differ in their fatty acid chains (level of saturation) and the composition of their head groups.

35
Q

Describe 3 functions of the lipid bilayer

A

1) It forms the basic structure of the membrane.
2) Its hydrophobic interior serves as a barrier.
3) It is responsible for the fluidity of the membrane (enabling cells to change shape).

36
Q

What are the possible roles of integral proteins?

A

1) Ligand binding receptors
2) Adhesion molecules- form physical contacts with the surrounding extracellular matrix or with cellular neighbours.
3) Pores/ Channels- provide route for specific molecules to passively cross the membrane.
4) Carriers- facilitate transport of molecules.
5) Pumps- use energy from ATP to drive active transport.
6) Enzymes
7) Participate in extracellular signalling.
8) Docking-marker acceptors- These are located on the inner membrane surface and interact with secretory vesicles leading to exocytosis of the vesicle contents.

37
Q

What do short carbohydrate chains on the outer surface of membranes act as?

A

Self-identity markers that enable cells to identify and interact with one another.

38
Q

What are two properties that influence whether a particle can cross the plasma membrane?

A

Size and solubility

39
Q

What forces are molecules passively driven across the membrane by?

A

Diffusion down a concentration gradient (AND OR)

Movement along an electrical gradient

40
Q

What are the factors that make up Fick’s law of diffusion?

A
  1. The magnitude of the concentration gradient (directly proportional, the greater the gradient the greater the rate).
  2. The surface area of the membrane across which diffusion is taking place (the greater the surface area, the greater the rate of diffusion).
  3. The lipid solubility of the substance (the greater the solubility, the more rapidly the substance will be able to diffuse across).
  4. The molecular weight of the substance (as weight increases, the rate of diffusion decreases).
  5. The distance through which diffusion must take place (the greater the distance the slower the rate of diffusion).
41
Q

What is normal blood pressure

A

More than 120 over 80 and less than 140 over 90

42
Q

What is an electrochemical gradient?

A

The net effect of simultaneous electrical and concentration gradients on an ion.

43
Q

Define osmosis

A

The net diffusion of water down its own concentration gradient through a selectively permeable membrane.

44
Q

Why can water molecules pass through the plasma membrane more readily than expected?

A

Due to gaps being created by the fluidity of the membrane.

45
Q

Define osmolarity

A

The concentration of osmotically active particles present in a solution. It can be calculated or measured and the units are osmoles (Osm) of solute per litre (Osm/l or osmol/l).

46
Q

What is tonicity?

A

The effect a solution has on cell volume

47
Q

What will happen if a cell is exposed to a hypotonic solution?

A

Cell volume will increase as the cell will gain water from its external environment.

48
Q

What will happen if a cell is exposed to a hypertonic solution?

A

Cell volume will decrease as the cell will lose water to its external environment.

49
Q

When are isotonic solutions used?

A

They are used to get drugs into patients as the drug then won’t affect osmolarity of the cell as they have the same osmolarity as the cell.

50
Q

What happens in carrier mediated transport and what two forms can it take?

A

Involves a substance binding onto a specific carrier which undergoes a conformational change which transports the substance. Can be active or facilitated.

51
Q

What are three important characteristics that describe carrier mediated transport?

A
  1. Specificity: Each carrier is specialised to transport a specific substance or a few closely related chemical compounds.
  2. Saturation: Transport maximum (Tm).
  3. Competition: Between substrates if carrier can transport more than one type.
52
Q

What is primary active transport?

A

Energy is directly required to move a substance against its concentration gradient.

53
Q

What is secondary active transport?

A

This does not split ATP but instead uses second hand energy stored in the form of an ion gradient (usually Na+). It can occur by:

1) Symport- the sodium and the solute move in the same direction.
2) Antiport- the sodium and the solute move in opposite directions.

54
Q

What are three important roles of the sodium-potassium pump?

A
  1. Helps establish Na+ and K+ concentration gradients across the plasma membrane of all cells.
  2. Helps regulate cell volume by controlling concentration of solutes inside the cell.
  3. The energy used to drive the pump indirectly serves as the energy source for secondary active transport.
55
Q

Describe vesicular transport

A
  • This requires energy for vesicle formation and movement within the cell (active).
  • Endocytosis involves the pinching off of membrane to engulf substance
  • Exocytosis involves a vesicle fusing with the plasma membrane, releasing its contents to the ECF.
56
Q

Describe the resting membrane potential of cells

A

Resting membrane potential is constant in non-excitable cells, and in excitable cells at rest. Usually inside negative, for typical human nerve cell is -70mV. the sign (+ or -) is the polarity of the excess charge on the inside of the membrane.)

57
Q

What are the equilibrium potentials for sodium and potassium?

A

For potassium -90mV

For sodium +60mV

58
Q

Explain why the membrane potential of cells is about -70mV

A

Greater movement of potassium as membrane is more permeable to it which will try and drive membrane potential towards its own. There is still a small but significant movement of sodium ions hence why it is -70 and not -90mV.

59
Q

Normal range of MABP is

A

70-105mmHg

Principles (14 decks)

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