Temperature Regulation & Diet and Nutrition

Humans are…

Homeothermic (warm-blooded)

What does Homeothermic mean?

Warm-blooded

Organism that will maintain stable internal body temp regardless of external influence

POIKILOTHERMIC:

cold blooded or ectoderm

What is the control of body temperature an example of? Why does the body temp need to be kept within a range?

* Homeostasis
* Essential for maintaining normal bodily processes (enzyme need specific shape)

What is the range body temperature need to be kept within?

Average 36.8 + or - degrees

What is body temperature affected by?

By camping site, age, gender and time of day (so normal body temp will differ)

Is body temperature the same throughout the body?

Outline how women’s body temperature changes during their menstrual cycle.

* Body temperature higher in second part of cycle
* Thought to be sure to the effects of progesterone or metabolic rate
* Used as an indicator of ovulation

Outline how temperature changes depending on age.

* Decrease with age
* Young children increase as increase metabolic rate
* Older decreases as more difficulty conserving heat

Body temperature balance=

a dynamic equilibrium between heat input and output

HEAT INPUT:

= internal production + external input

INTERNAL PRODUCTION:

Metabolism (breaking large molecules)

(using energy for physiological process)

(60% released as heat and muscle contraction)

EXTERNAL INPUT:

From the environment (convection, conduction and radiation)

HEAT OUTPUT:

Losses to the environment

What are the ways are body loses heat?

1. Convection
2. Evaporation (eg. sweating and respiration 25-30%)
3. Radiation (70% at rest)
4. Conduction

CONVECTION:

= moving air removes radiated heat

* Enhanced by bulk flow of air across the skin surface (wind chill factor)

EVAPORATION:

= loss of heat by evaporation of water

Occurs when liquid is heated to a gas

water → vapour (generated by heat)

RADIATION:

Emission of electromagnetic radiation

CONDUCTION:

= Direct transfer by contact 

Generally body T is…

larger than ambient (environmental) T

THERMONEUTRAL ZONE (TNZ):

Range of ambient T over which the body core T remains constant (25-30 degrees)

→ Range of environmental temps over which heat produced remains constant

(Basal rate of) Heat production

= heat output

Above TNZ there is

net bodily gain of heat

Below TNZ there is

net bodily loss of heat

It is more difficult to regulate body temp if you are too hot or cold?

Too cold

What regulates body temperature?

Thermoregulatory centre in the hypothalamus

(in the brain)

→ regulates thermoreceptor inputs

What is body temperature monitored by?

* Receptors in the skin (peripheral receptors in the skin dermis)
* AND brain (monitor temp of blood flowing through tissue)
* Receptors in abdominal vena cava and oesophagus and stomach which detect core body temperature

Draw a negative feedback loop to display how body temp it regulated.

What behavioural changes do we make when our body is too hot?

* Take of clothes
* Go into shade
* Drink cool drinks

What are the 2 main mechanisms used to cool down the body?

1. Vasodilation
2. Sweating

Explain what happen in vasodilation.

1. Pre capillary sphincter muscles in the arteriole relax. This results in increase blood flow to the capillaries
2. Heat can radiate out the blood from the capillaries across the dermis into the environment

→ Peripheral vasodilation: widening of the lumen

Explain what happen in sweating.

1. Take Na and H2O from blood and incorporate with sweat to body surface
2. Evaporates H2O (liquid) into vapour (latent heat of vaporisation)

→ Body will need to replenish Na and H2O after

What will reduce the effects of sweating?

* Tight clothes body → can’t seat efficiently
* Humid environment decrease or prevent evaporation so body can’t be cooled

Summarise the responses to increased temperature.

Maximise heat loss

* Vasodilation
* Increased Sweat
* Behavioural responses

→ use of fans to increase convective heat loss

→ Immersion in water to increase conductive heat loss

→ Staying out of the sun to prevent radiant heat gain

→ Removing clothes

Minimise heat production

* Diminished food intake to lessen obligatory heat production
* Behavioural responses - decrease physical activity

What are the behavioural responses when the body gets too cold?

* Putting on more clothes
* Sit near radiator to increase conduction
* Have a hot drink

What are the main thermoregulatory responses to the body being too cold?

1. Vasoconstriction
2. Shivering
3. Thermogenesis (non-shivering)
4. Heat conservation

Explain what happens in vasoconstriction.

1. pre capillary sphincters contract which reduces the amount of blood flowing through the capillaries at surface of skin
2. Less blood flow around beneath the epidermis (skin surface) (look pale) results in decreased heat loss

→ Peripheral vasoconstriction: Narrowing of lumen of blood vessel

Describe how shivering helps to increase body temperature.

→ Tone in muscle increase so more heat produced

* Involuntary muscular thermogenesis (shivering)
* 4-5 fold increase in heat output over basal level to increase body temp

→ Can have voluntary muscular movement such as jumping into produce a similar effect

NON SHIVERING THERMOGENESIS:

= Process that can increase metabolic rate that is NOT dependent on muscle contraction

Outline what happens in non-shivering thermogenesis.

* metabolism of brown fat (adipose tissue)
* Brown fat contains large no. of proteins which can uncouple oxidation from phosphorylation
* This makes fuel metabolism less efficient which generates lots of heat

→ heat generated as a result of insufficient metabolism

→ Minimal in adults more important in young children and babies as have lots of brown adipose tissue

How does the body try to conserve heat?

* Contraction of muscle to make hairs project upwards
* Trap a layer of air above the skin to insulate body
* Not very effective in humans

Summarise how the body responds to a decrease in temperature.

Minimise heat loss

* Vasoconstriction of cutaneous blood vessels
* Lack of sweating
* Behavioural responses

→ Adding layers of protective clothing

→ Curling up to minimise exposed surface

→ Standing near heat source to enhance radiant heat gain

Maximise heat production

* Shivering thermogenesis
* Non-shivering thermogenesis
* Behavioural responses

→ Increased voluntary activity (stamping feet etc)

HYPOTHERMIA:

= Dangerous drop in body temp

Below 35 degrees

What are the early signs of hypothermia?

* Shivering
* Cold skin
* Pale skin
* Slurred speech
* fast breathing
* Tiredness/confusion

What happens in severe cases of hypothermia?

32 degrees or less stop shivering may lose consciousness

If untreated lead to heart and respiratory system failure

Leads to death

HYPERTHERMIA:

= Body temp elevated from normal

Above 38 degrees

What is heat exhaustion? Can you list some symptoms.

Less severe form of hyperthermia

Symptoms: muscle weakness, nausea and vomiting and headaches

What are the different symptoms of hyperthermia?

* Confusion
* Mental changes
* Seizure
* Brain damage

= heatstroke

Extreme: Coma and death

HYPRYEXIA:

* very high fever
* Above 40 degrees
* Nee immediate medical attention

FEVER (PYREXIA):

* Result of a chemical resetting (increase) of thermal set point
* Failed thermoregulation the set point of 37 degrees has been altered changed due to disease
* 38 degrees or higher

Outline how fever occurs.

1. Bacterial infection: bacteria release endogenous pyrogens which cause fever
2. Body triggers thermoregulatory response to pyrogens: body WBC in immune systems are triggered to release pyrogens in form of cytokines eg. IL-1 TNF-alpha and IFN
3. Pyrogens inhibit heat sensing neurones in hypothalamus and excite cold sensing receptors in prostate glands and E2. This cause hypothalamus to think body temp is lower so body temp stabilises at a new elevated set point
4. Augmentation of immune response (innate and adaptive)
5. Body temp remains elevated until fever breaks

What is drugs can be used to treat fever?

Ibuprofen and paracetamol

They inhibit production of prostate gland and E2

DIET:

= food and drink consumed by individual

→ can be regulated by internal factors

NUTRITION:

= process of obtaining food necessary for health and growth

AQEQUATE (healthy) NUTRITION:

= an integral part of daily life that contributes to the physiological, mental and social well-being of individuals

… a balanced diet that contains adequate amounts of nutrients in relation to bodily requirements

MALNUTRITION:

= Any physical condition resulting either from an inappropriate or inadequate diet that either provides too much or too little of necessary nutrient

… Negatively affects the quality of life and learning as well as death and disease status

Total body energy =

energy stored + energy intake - energy output

Energy output =

heat + work

How much energy released in chemical reactions as heat?

About 50% and is NOT available for work

What are the different type of ‘work’ outputs in the body?

1. Active transport of molecules

* Into/out of the body, between compartments and across membranes


2. Mechanical

* Voluntary and involuntary movement of muscles


3. Chemical

* Synthesis for growth and maintenance (tissues and cells)
* Short/long term energy storage (ATP, glycogen, fat)

TOTAL ENERGEY EXPENDITURE (TEE):

= Basal metabolic rate + thermic effect food + Physical activity

THERMIC EFFECT:

= energy required to digest and absorb food

BASAL METABOLIC RATE (BMR):

= Minimum level of energy required to sustain vital functions

Eg. Metabolic actions to maintain blood circulation and respiration and gastrointestinal and liver functions

How is Basal Metabolic Rate measured and expressed?

* measured as the heat produced or oxygen consumed per unit time
* Measured at rest in a fasted state in a thermo-neutral environment
* Expressed as the calories released/kg of body mass or m squared of BSA/h (BSA= body area)

PHYSICAL ACTIVITY LEVEL (PAL):

* 24h index of energy expenditure due to physical activity

→ Estimated based on a list of physical activities a person carries out

→ characterised on intensity level

ESTIMATED AVERAGE REQUIREMENT (EAR):

= BMR x PAL

EAR values shown for moderately active individuals for healthy weight

How does UK estimated average requirement of individual change with age?

* Decrease with age due to reduction in both base and metabolic rate of individual
* Also reduction physical activity levels

Nutritional requirement

= Amount each nutrient that is needed

DIETARY REFERENCE VALUES (DRVs):

= quantitive reference values for nutritional intake

* Are developed for different life stages, gender groups and age ranges

What are dietary reference values derived from?

Derived from different population groups based on health criteria

REFERENCES NUTRIENT INTAKE (RNIs):

= the level of intake adequate for most people

→ optimum intake for population as a whole

ESTIMATED AVERAGE REQUIREMENT (EARs):

=level of intake adequate for half of the population

LOWER REFERENCE NUTRIENT INTAKE (LRNIs):

= level of intake below which almost all individuals would be considered to have an inadequate uptake

TOLERABLE UPPER INTAKE (UI):

= max level of daily intake of a nutrient likely to have no adverse health effects

→ As intake increase above UI, the risk of adverse effects increases

List the various Dietary Reference values.

* References Nutrient Intake (RNIs)
* Estimated Average Requirement (EARs)
* Lower Reference Nutrient Intake (LRNIs)
* Tolerable Upper Intake (UI)

What are Dietary Reference Values (DRVs) used for?

* Used when issuing national guidance
* Used in policy making, healthcare, food industry (basis of food labels dietary guidelines), academic research, dietary assessment, planning diets and developing dietary recommendations for individuals or groups

Who gives the advice on the estimated requirements for groups of populations?

The scientific Advisory Committee of Nutrition

What is the SACN Protein DRV for the UK population?

0.75g per kg of body weight per day

What changes SACN Protein DRV for the UK population?

Requirements increase during pregnancy/lactation

by 6g and 11g per day respectively

What are the DRVs for carbohydrates and fat as a percentage of energy intake?

What does the total carbs include?

* All starch sugars and dietary fibre
* Free sugars are sugars added to food and drinks (manufacturers/ consumers) plus sugars naturally present in honey, syrups and fruit juice

What are the total fat include?

All saturated and unsaturated fat (mono and polyunsaturated)

What are the recommended fibre and salt intake in the UK?

→ On average UK don’t co some enough fibre an have too much salt

What are the daily reference intakes for adults?

What is the problem of obesity?

* Increase risk of cardiovascular disease, cancer and type 2 diabetes
* Decrease mobility, quality of life and lifespan
* Current cost to the NHS in excess of £5 bn/annum and rising
* Incidence worldwide is increase (developed and developing nations)

OBESITY:

= excess body weight in the form of fat

→ Can lead to bp (strong connections with stokes)

→ Increased absence from work

What are the long term problems associated with malnutrition?

* Muscle and bone problems
* Loss of fertility
* Heart problems

What are the problems concerning eating disorders?

* Cost country £15 bn/annum
* Increases risk of muscle and bone problems and heart failure and seizures
* Decrease fertility, quality of life and lifespan
* Incidence is increased

→ important health and economic consequences

→ Anorexia 1/3 most common illness amongst teenagers

List some Macronutrients.

* Proteins
* Fats
* Carbohydrates

What are the energy innate of Macronutrients in the body?

* Daily requirements of 10g
* = required in large amounts in the diet

List some Micronutrients.

* Vitamins (organic): water soluble (not stored) and fat soluble (stored)
* Minerals (inorganic)

→ Macrominerals: Na, K, Ca, Mg, Cl and P

→ Trace elements: Fe, Zn, Se, Cu, Se, Mn, Mo

What are the daily requirements of Micronutrients in the body?

* Few micrograms or mg or g
* Needed for normal growth and development

MICRONUTRIENTS:

= chemical elements or substances that are required in trace amounts

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What are proteins required for?

* Structural and mechanical functions

→ regulation of tissue and organs of body eg. hair and nail formation

→ Important building block of bone, muscle, cartilage and skin

* Enzymes
* Hormones
* Antibodies
* Fluid balance
* Acid-base balance
* Channels and pumps
* Transport

What is the difference between essential and non-essential amino acids?

Essential amino acids cannot be synthesised within the body- have to be obtained through diet

Whereas nn-essential can be synthesised within the body

What are the essential amino acids?

Draw amino acid structure.

→ All contain alpha carbon where NH2 and COOH are attached

→ Side chain unique to each amino acid

List some different functions of amino acids.

* AA required for protein synthesis
* AA are precursor for other biomolecules

→ Nucleotides

→ Catecholamines

→ Neurotransmitters

* AA as neurontransmitters
* Formation of anti-oxidants

Describe how amino acids used to synthesis of proteins.

* Structural

→ Collagens (main components of connective tissue (proline and lysine)

→ Elastins (part of arterioles and cartilage (made of glycine, valine, alanine and proline)

→ Keratins

* Functional

→ Eg. Enzymes, antibodies, receptors, hormones

→ Eg. Tyrosine needed to synthesise thyroid hormones

CATECHOLAMINES:

= hormone produced by adrenal glands