Lecture 3

Question 1

What are the 5 different types of receptors?

Answer 1

Free nerve endings, tactile (Merkel) discs, tactile (meissner) corpuscles, lamellar (pacinian) corpuscles, bulbous corpuscles

Question 2

What are free nerve endings?

Answer 2

Most common receptor in skin, terminal branches extend up into layers of the epidermis, most cation channels

Question 3

What are tactile (Merkel) discs?

Answer 3

Deepest layer of dermis, detect stimuli in tactile epithelial cells and relays it to sensory nerve terminals itself via serotonin, abundant in fingertips (small receptive field)

Question 4

What are tactile (meissner) corpuscles?

Answer 4

Located in papillary layer of dermis, beaching unmyelinated sensory terminals surrounded by modified Schwann cells and enclosed in a thin oval fibrous connective tissue capsule, senses delicate touch

Question 5

What are lamellar (pacinian) corpuscles?

Answer 5

Scattered deep in dermis and hypodermis, single dendrite within layers of collagen fibres and specialised fibroblasts, jelly fluid in between, deformation of capsule opens na channels in axon, rests quickly

Question 6

What are bulbous corpuscles?

Answer 6

In dermis and subcutaneous tissue, network of nerve endings intertwined with a core of collagen fibres continuous with collagen in dermis, heavy / prolonged force on dermis transmits to bulbous corpuscles

Question 7

How is skin blood flow controlled?

Answer 7

Sympathetic nervous system - noradrenaline binds to alpha 1 receptor in skin, GPCR coupled to produce second messenger, more calcium, more cross bridge formation, contraction, constriction

Question 8

Eccrine sweat gland role in thermoregulation?

Answer 8

SNS - ACh released onto mAChRs produce watery salty sweat

Question 9

What is radiation?

Answer 9

Heat loss by infrared rays

Question 10

What is conduction?

Answer 10

Loose heat to air surrounding body (down gradient)

Question 11

What is convection?

Answer 11

Hot air rises and replaced with cool air around body restoring gradient

Question 12

What is evaporation?

Answer 12

Takes heat energy to cause water to evaporate which is taken from the body

Question 13

What is core body temperature?

Answer 13

Temperature of blood around organs like heart, brain, lungs (most efficient at 36.5-37.5)

Question 14

Mechanisms for heat loss?

Answer 14

Heat loss centre activated, decrease SNS activity for vasodilation, increase SNS cholinergic activation of mAChRs on sweat glands for more sweating, increase respiratory rate, behavioural changes

Question 15

Where is core body temperature regulated?

Answer 15

Pre-optic area of hypothalamus containing central thermoreceptors

Question 16

Mechanisms for heat generation?

Answer 16

Heat gain centre activated, heat transfer from arteries to veins, shivering (increased tone of muscles), non-shivering thermogenesis (glucagon beak down of brown fat into heat instead of ATP), increase thyroxine (TSH and TRH increase basal metabolic rate)

Question 17

What are arrector pili muscles?

Answer 17

Attach to hair follicle on underside of dermis, contraction pulls hair follicle so stands upright, simple / goosebumps, compressed sebaceous glands

Question 18

What is physiological feed forward in humans?

Answer 18

Peripheral thermoreceptors in skin telling you CBT will drop so can start taking action before this occurs

Question 19

Consequences of severe second and third degree burns?

Answer 19

Lost water proofing layer of epidermis, loose fluid, make capillaries leaky into burn area causing loss of water

Question 20

Fluid replacement for burn patients rules?

Answer 20

Rule of 9s

Need to know percentage of total body surface of area involved

Question 21

Potential complications of severe second and third degree burns?

Answer 21

Skin function - dehydration and hypovolemic shock (very low blood pressure), infection/sepsis and hypothermia