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Gymnastics and tumbling > Chapter 29 (Homeostasis) > Flashcards

Chapter 29 (Homeostasis) Flashcards

1
Q

Definition of homeostasis?

A

The maintenance of a stable internal environment

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2
Q

Why is homeostasis important?

A
  • To ensure optimum conditions for enzyme controlled reactions - so control rate + efficiency of metabolic pathways
  • To ensure water potential of cells, blood + tissue fluid are kept within correct range to prevent cells shrinking/expanding due to water loss/gain.
  • Organisms aren’t as dependent on external temp, so mammals and birds can inhabit wider range of ecosystems.
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3
Q

Internal factors that must be controlled?

A

pH, temperature, plasma glucose conc, plasma water content, ion balance.

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4
Q

Environmental external factors that animals and plants respond to?

A

Humidity, air temperature, light intensity, new or sudden sound.

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5
Q

Definition of negative feedback

A

A mechanism where the response brings about a counter response to the initial change in environment
NF only works within certain limits - ie, if change is too large, then effectors can’t counteract change.

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6
Q

Definition of effector?

A

Target tissue/organ that brings about a response when stimulated - can be muscle or gland.

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7
Q

Definition of a receptor?

A

Specialised cell that detects a stimulus (change in environment) or deviation from the set point. Receptor transfers information to a neurone and converts information to a nerve impulse.

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8
Q

What is a controller?

A

(communication pathway) - coordinates information from receptors and sends impulses to the effectors. Ie, nervous system and hormonal system.

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9
Q

What is the set point

A

The desired value that the negative feedback mechanism operates around.

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10
Q

What is feedback loop?

A

Pathway which returns the altered factor back to its set point and informs the receptors of changes to the system

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11
Q

What is a response?

A

Secretion of a hormone from endocrine gland, or contractions of muscles.

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12
Q

What is a positive feedback mechanism

A

NOT IN HOMEOSTASIS!!!

Theses mechanisms amplify the change (enhance the original stimulus)
The effector triggers a response that moves the factor further from the initial level,
eg, hypothermia, hyperthermia
voltage gated NA+ ion channels + action potentials
Blood clotting cascade.

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13
Q

Specific example of PFM

A

Secretion of oxytocin controlled by PFM
Release of oxytocin (hormone) increases speed and intensity of uterine contractions
This increased frequency + strength of contractions FURTHER increased secretion of oxytocin.
PF continues until childbirth complete.
Birth of baby stops release of oxytocin + ends PFM.

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14
Q

Normal ranges for blood glucose?

A

3.6-7.8 mmoldm-3

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15
Q

Normal ranges for Na+

A

135 -145 mmoldm-3

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16
Q

Normal ranges for Osmolality (balance between electrolytes and water)

A

275-295 mOsm kg-1

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17
Q

Normal ranges for body temperature?

A

36.5 -37.5 degrees C. optimum = 37.4 degrees C

It varies between individuals - BMI, gender, age, time of day, stage of menstrual cycle for women, exercise level.

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18
Q

Normal ranges for blood pressure?

A

120/80- 140/90 mmHg

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19
Q

Definition of hypothermia?

A

Lowering body temperature below 35 degrees C.

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20
Q

Effects of hypothermia?

A

Rate of metabolic reactions reduce (as molecules possess less kinetic energy)
Generates positive feedback as less metabolic thermal energy released - body temp reduces further.

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21
Q

Symptoms of hypothermia?

A

Shivering
Inability to pay attention
Weak pulse
Shallow breathing

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22
Q

Treatment for someone with hypothermia?

A
  • Move person indoors and/or out of cold water.
  • Insulate person from cold ground
  • Remove wet clothing / replace with warm, dry clothing
  • Apply warm compresses to neck, groin, chest
    Do not heat arms and legs as this forces cold blood back to core of body to major organs.
    Provide EAR is breathing stops
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23
Q

Causes of hypothermia?

A
  1. Result of exposure to extreme cold
    - Extreme temp gradient between skin + environmental temps, so heat lost rapidly.
    Strong wind increases heat loss
    Heat is conducted from skin to warm air next to it. Wind takes warm air away. (also air is poor conductor of heat)
    As wind speed incr, depth of warm air layer reduces, so heat loss is increased.
  2. Getting wet or being immersed in water
    Wet clothes prevent warm layer of air being built up around skin, so heat lost by conduction
  3. Being elderly
    Many turn of heating appliances to save money
    Some are less mobile so sit in one place - don’t produce internal heat
    Some do not eat well enough to provide sufficient respiratory substrates.
  4. Fuel Poverty
    When household spends more than 10% household income on fuel to heat house to satisfactory temperature.
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24
Q

Definition of hyperthermia?

A

(pyrexia)
Raising body temperature above 38 degrees C.
Above 41 degrees C, heat stroke - nauseous + dizzy + maybe lose consciousness.

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25
Q

Effects of hyperthermia?

A

Rate of metabolic reactions increases (as all molecules possess more kinetic energy)
Generates positive feedback as more metabolic thermal energy released - temp increases even further.

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26
Q

Causes of hyperthermia?

A

Exposure to high environmental temperatures.
Infection in which toxins produced by bacteria or viruses affect hypothalamus.
Some medications
Over-exertion
High BMI

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27
Q

Symptoms of hyperthermia?

A

Headaches
Mental confusion
Muscle cramps
Vomiting

28
Q

Treatment for hyperthermia?

A

Move person to cool conditions and/or use a fan
Ensure person is kept hydrated with cold drinks
Apply cold water to skin
Expose skin so water can evaporate readily.

29
Q

Measuring core body temperature?

A

Can’t measure directly or routinely as it would require surgery. Instead use peripheral measurements as close to core body temp.

30
Q

Apparatus to measuring body temperature?

A

Standard mercury-in-glass thermometer

Nowadays more electronic infra-red sensors which are more accurate and rapid.

31
Q

Ways of measuring body temp?

A

Oral
Rectal
Axillary
Tympanic

32
Q

Oral temp measurements info?

A

Simplest peripheral measurement
Least accurate
Not suitable for unconscious person/uncooperative child.

Bulb placed under tongue, left in place for 7-8 mins.

33
Q

Rectal temp measurements info?

A

Most accurate temp - to around 0.5 degrees c above oral temp.
thermometer only needs to be kept in place for 2 mins.

Some say rectum takes longer to change to internal changes in body temp.
Thermometers used for this must be kept separate from thermometers used in other procedures.

34
Q

Axillary temp measurements info?

A

Skin temp taken under armpit
Thermometer left in place for around 9 mins
Technique least likely to cause trauma.

35
Q

Tympanic temp measurements info?

A

Ear.
Care taken to ensure no damage occurs to tympanic membrane (ear drum)
More accurate than oral or axillary measurements

36
Q

Why are tympanic measurements more accurate then oral or axillary measurements?

A

Tympanic measurements accurately reflect core body temp as eardrum shares blood supply with thermoregulatory centre in hypothalamus. Oral and axillary give readings lower than core body temp.

37
Q

Why are strip-type thermometers less accurate way of measuring body temp?

A

They measure skin temp (peripheral temp) which is likely to be different to core temp, so less accurate.

38
Q

Mechanisms to increase body temperature?

A
  • decrease in sweat secreted from sweat glands
  • Erector pilli muscles contract
  • Vasoconstriction of arterioles supplying skin
  • Increase in secretion of thyroxine (from thyroid gland)
  • Increase in secretion of adrenaline (from adrenal gland)
  • Shivering
39
Q

How does shivering increase body temp?

A

Muscles contract in spasms
Body shivers
More thermal energy released from increased respiration (exothermic)

40
Q

How does an increase in secretion of adrenaline from adrenal gland increase body temp?

A
  • Increases metabolic rate
  • Increases rate of respiration
  • More thermal energy released as respiration is exothermic.
    Increases body temp.
41
Q

How does no sweat increase body temp?

A

No heat lost through evaporation

No heat removed from body

42
Q

How do erector pili muscles increase body temp?

A 
Erector muscles contract
Hairs stand erect
Air pockets trapped between hairs and skin's surface
Air is a good insulator
Prevents heat loss.
43
Q

How does the increase in secretion of thyroxine from thyroid gland increase body temperature?

A
  • Hypothalamus secretes thyrotropin - releasing hormone (TRH)
  • TRH stimulates production of thyroid stimulating hormone (TSH) from anterior pituitary gland.
  • TSH stimulates secretion of thyroxine.
  • Thyroxine diffuses into nucleus + incr. transcription of specific genes.
  • Increases production of mitochondria and respiratory enzymes
  • Incr. metabolism of glucose and lipids - Incr., availability of respiratory substrates.
  • so increases rate of respiration.
  • More thermal energy released as respiration is exothermic, so incr. body temp.

Thyroxine regulates metabolic rate, so without it, rate of metabolism is reduced, so could cause weight gain.

44
Q

Why is it important to maintain core body temperature?

A

To ensure cells work efficiently. Below 37 degrees C, diffusion is too slow and kinetic energy is too low, so less frequent successful collisions between substrate and enzyme.

Above 37 degrees C, enzymes are less stable and at high temperatures denature.

The ability to maintain a constant internal temperature has allowed endotherms to inhabit a wide range of ambient temperatures.

45
Q

Definition of thermoregulation?

A

The ability to regulate internal body temperature, irrespective of external temperature changes.
Controlled by autonomic nervous system.

46
Q

What is the role of the hypothalamus in temperature regulation.

A

Body temperature is maintained at set point by thermoregulatory centre in hypothalamus.

Hypothalamus receives impulses from thermoreceptors in:

  • Hypothalamus which detect internal temp of blood plasma flowing through brain.
  • Skin (peripheral thermoreceptors) that detect external temperature of skin. Act as early warning system that core body temp is going to change if extremities are getting too cold/hot.
47
Q

Movement of thermoreceptors?

A 
Thermoreceptors send impulses along sensory neurones to hypothalamus. Impulse along motor neurones to effectors (skeletal muscles, erector pili muscles, sweat glands)
Effectors respond ( muscles contract or glands secrete sweat) to restore core body temp to normal.
48
Q

Definition of convection?

A

If fluid, like air is warmed, it becomes dense.

It rises through surrounding cooler air, and movements in fluid transport heat away quicker.

49
Q

Definition of conduction?

A

Heat passes from one particle to adjacent particle
Speed of transfer depends on ability of material to conduct heat.
Air is poor conductor, water is better conductor.

50
Q

Definition of radiation?

A

Infrared radiation emitted by all objects.
Hotter object emits more IRR.
IRR absorbed by solid objects and warms them.

51
Q

Mechanisms to reduce body temperature?

A

Increase in sweat secreted from sweat glands
Erector pili muscles relax
Vasodilation of arterioles supplying skin

52
Q

How does an increase in sweat from sweat glands reduce body temp?

A

More heat lost when sweat evaporates from skin’s surface.
Removes heat from body
Skin is cooled.

53
Q

How does the vasodilation of arterioles supplying the surface of the skin reduce body temp?

A

Lumen of arterioles widen
More blood flows through capillaries in surface layers of dermis.
More heat lost by radiation
As more energy required to change state of water from liquid to gas
Temperature of blood plasma reduced.

54
Q

How does erector pili muscles relaxing reduce body temperature?

A

Hairs lie flat
Less air trapped between hairs and skin’s surface.
Less insulation of skin.
More heat lost by convection and radiation.

55
Q

Effect of increased metabolic activity on heart rate.

A
  1. Increased muscular/metabolic activity
  2. More carbon dioxide produced by tissues from increased respiration
  3. Chemical receptors in carotid arteries increase frequency of impulses to SAN via sympathetic nervous system
  4. SAN increases heart rate
  5. Increased blood flow removes carbon dioxide faster
  6. Carbon dioxide level returns to normal.
56
Q

Role of medulla oblongata?

A

Part of ANS
Has two regions linked to SAN by motor neurones.
- One increases HR by sending impulses through sympathetic nervous system via accelerator nerve to SAN.
- One decreases HR by sending impulses through parasympathetic nervous system via vagus nerve to SAN.

Changes in heart rate controlled by cardiovascular centre within MO.

57
Q

Heart rate changes info?

A

Heart rate changed in response to internal stimuli, eg, to prevent fainting due to low blood pressure or to elevate HR when PO2 is low.

Electrical impulses sent from receptors to medulla oblongata via sensory neurones (via parasympathetic NS)
Electrical impulses sent along motor neurones to SAN
NEGATIVE FEEDBACK.

58
Q

How does vasoconstriction of arterioles supplying skin increase body temp?

A

Smooth muscle in arteriole wall contracts
Narrows lumen of arterioles
Shuts off blood flow through capillaries in surface layers of dermis.
Reduces heat lost by radiation.

59
Q

Nervous system control of heart rate.

A

SAN (found in wall of right atrium) generates electrical impulses - cardiac muscles contract.
Rate at which SAN sends impulses is unconsciously controlled by medulla oblongata.

60
Q

Importance of Fight, flight, fright response by nervous system?

A
  • Incr. HR - more blood pumped around body faster
  • Muscles around bronchioles relax - deeper breathing.
  • Glycogen hydrolysed to glucose - more respiratory substrate available for incr. aerobic respiration.
  • Vasoconstriction of arterioles supplying skin and gut.
  • Vasodilation of arterioles supplying heart, lungs, skeletal muscles - incr. delivery of O2, glc to… - incr, aerobic respiration, incr, energy release.
  • contraction of erector pills muscles in skin - hairs stand erect - increase appearance of size.
61
Q

Stimuli to alter HR are detected by:

A

Baroreceptors (pressure receptors) - detect pressure changes in walls of aorta, carotid arteries and vena cava.
Stimulated by both incr. and decr. in pressure.

Chemoreceptors - found in walls of aorta, carotid artery and medulla oblongata. Detect oxygen and carbon dioxide level of plasma and changes in plasma pH (which indicate blood oxygen levels)

  • Incr. in Co2, decr, in O2, decr. in pH, incr. in HR - blood flows to lungs more quickly - Incr. exhalation of CO2.
  • decr. in CO2, incr. in O2, incr. in pH, decr in HR (as frequency of impulses to SAN decr. )
62
Q

Info on adrenal glands?

A

Stimulated by Sympathetic nervous system
Endocrine glands that produce and secrete adrenaline
located just above kidneys.

63
Q

Info on adrenaline?

A

Secreted by medulla, in anticipation, excitement, shock or stress. It increases heart rate, helping to prepare body for activity.
Is a modified amino acid - catecholamine hormone.
Is hydrophilic hormone so can’t diffuse through CSM.
Responsible for flight, fright or fight response.

64
Q

How does adrenaline increase HR?

A
  1. Adrenaline binds to specific receptors in cells of SAN
  2. Causing G protein to be activated and initiates a secondary messenger system (G protein activation leads to activation of enzyme called adenyl cyclase which converts ATP into cAMP.
  3. This incr. cyclic AMP production
  4. This incr. permeability of Ca 2+ channels
  5. Which enables pacemaker cells to depolarise more quickly as threshold for action potentials is lowered.
  6. So cardiac muscle contracts more frequently and with more force, resulting in incr. HR, so heart pumps more blood.
65
Q

Vasoconstriction as example of cell signalling?

A
  • Thromboxane is cell signalling molecule released by platelets into blood plasma.
  • Smooth muscle cell is target cell for thromboxane.
  • Thromboxane binds to receptors on csm of smooth muscle by complementary binding.
  • the binding triggers internal change in smooth muscle cell. - eg, enzyme cascade
    This results in response - contraction of smooth muscle cell - vasoconstriction.
66
Q

Secretion of thyroxine in terms of immediate effect info?

A

Effect of thyroxine not immediate and takes time for transcription of genes and translation to occur to produce proteins.
Humans secrete more thyroxine when exposed to cold for few days, as body’s mechanisms adjust and become more active, less thyroxine made and we are ‘acclimatised’ to new low-temp environment.

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