Otitis media and thermoregulation

Question 1

define otitis media

Answer 1

Otitis media is an infection of the middle ear which causes inflammation and build up of fluid behind the tympanic membrane

Question 2

List the clinical features of otitis media

Answer 2

Earache
Fever
Vomiting 
Lack of energy 
Slight hearing loss
Dizziness
Loss of balance

Question 3

How is hearing reduced in otitis media?

Answer 3

Occurs when an infection leads to inflammation of mucus membranes in the nasopharynx and causes the Eustachian tube to become swollen or blocked.

As a result, the gas volume in the middle ear is trapped and partially absorbed by surrounding tissues. This leads to negative pressure and fluid from surrounding tissues can be sucked into the tympanic cavity. Bacteria from the nasopharynx can enter the middle ear space, infecting the fluid.

Question 4

Define thermoregulation

Answer 4

The ability of the body to maintain core temperature of 37.5 +/- 0.5 despite changes in external temperature

Question 5

Describe thermoregulation

Answer 5

Change to body temperature is detected by thermoreceptors: these can be either central (in deep body structures e.g. hypothalamus) or peripheral (in skin).

Heat promoting centre or heat loss centre in the hypothalamus is stimulated.

Impulses are sent to effectors

Increase/decrease in heat production

Temperature returns back to normal

Question 6

List some ways in which temperature loss can be prevented and temperate increase can be promoted

Answer 6

Minimise temp loss:
constriction of skin arterioles
reduction of surface area
behavioural response (put on warmer clothes)

Inc heat production:
shivering and increased voluntary activity
Increased muscle tone (tensing)
Increased secretion of adrenaline
increased food appetite
Increased thyroxine please which increases metabolic activity and produces heat

Question 7

What are some ways to decrease body temperature when body temperature is too high

Answer 7

Vasodilation of blood vessels
Sweating
Behaviour response (put on cooler clothing)

Decreased muscle tone and less voluntary activity
decreased secretion of adrenaline
decreased food appetite

Question 8

list the effectors involved in temperature regulation

Answer 8

Smooth muscle in arterioles
Adrenal gland
thyroid glands
Skeletal muscles 
Sweat glands
Errector Pilli muscles 
Behaviour

Question 9

Describe the response that is induced in smooth muscle in arterioles of skin in response to low and high temperature

Answer 9

Low temperature: Vasoconstriction of arterioles

High temperature:
Vasodilation

Question 10

Describe the response that is induced in arrector pilli muscles in response to low and high temperature

Answer 10

Low temperature:
arrestor muscles are contracted. This causes hairs to raise, trapping a layer of warm air.

High temperature:
arrector pilli muscles relax, hairs are lowered

Question 11

Describe the response that is induced in skeletal muscles in response to LOW temperature

Answer 11

Shivering: muscles contract and relax rapidly, generating heat

Question 12

Describe the response that is induced in sweat glands in response to HIGH temperature

Answer 12

Glands secrete sweat which evaporates

Question 13

Describe the response that is induced in thyroid and adrenal glands in response to low and high temperature

Answer 13

Low:
adrenaline and thyroxine are released which increase metabolic activity and generates heat

High:
glands stop secreting adrenaline and thyroxine

Question 14

Describe the response that change in behaviour can respond to low and high temperature

Answer 14

Low temperature:
putting on more clothes, curling up

high temperature:
removing layers, finding shade

Question 15

define a fever

Answer 15

An elevation in the core temperature caused by resetting of the hypothalamic thermostat

Question 16

list the common causes of a fever and describe the mechanism of a fever

Answer 16

Common causes:
bacterial or viral infections

Mechanism:
When phagocytes ingest pathogens, they are stimulated to secrete a pyrogen (interleukin-1).

It circulates to the hypothalamus and induces neurons in the pre-optic area to secrete prostaglandins.

Prostaglandins reset the hypothalamic thermostat to a higher temperature.

The body responds to increase temperature by heat conservation/promoting methods. This causes chills.

After the pyrogens disappear, the hypothalamic thermostat is reset back to its normal core temperature. The crisis phase occurs to reduce temperature (sweating)

Question 17

Describe qualities and the mechanism of action of paracetamol

Answer 17

Paracetamol is a mild analgesic and antipyretic.

It is a weak inhibitor of the synthesis of prostaglandins. Prostaglandins are needed to sensitise nerve endings so that pain may be felt when the area is stimulated.

It does this by inhibiting COX (1 and 2) enzymes which are needed for the synthesis of prostaglandins.

It does not directly binds to the active site of COX enzymes but reduces COX which needs to be oxidised for function.

Question 18

what are the side effects of paracetamol overdose and how can this be treated?

Answer 18

Liver toxicity

Treated with antioxidants or a liver transplant