Lecture 3: Skin Physiology Flashcards
1
Q
What are the different types of Touch receptors of the skin?
5
A
- Free nerve endings
- Tactile discs
- Tactile corpuscles
- Lamellar corpuscles
- Bulbous corpuscles
2
Q
How are receptors adapted to different stimuli?
2
A
- Can often respond to several different stimuli
- Will be most sensitive to a particular type of stimulus
3
Q
What is the most common receptor in the skin?
A
Free nerve endings
4
Q
What is the structure of free nerve endings?
2
A
- Mostly unmyelinated/small diameter fibres
- some myelinated/small diameter fibres
5
Q
Where are Sensory Terminals found?
A
The distal ends of free nerve endings
6
Q
What are Sensory Terminals?
A
Small swellings at the end of free nerve endings
7
Q
What do sensory terminals possess?
A
Receptors that function as Cation channels leading to depolarisation and action potentials
8
Q
What do Free Nerve endings mainly respond to?
4
A
- Temperature
- Painful stimuli
- Some movement/pressure
- Some itch
9
Q
What are Peritrichial nerve endings?
A
Free nerve endings that wrap around hair follicles
10
Q
What do Peritrichial endings do?
A
Act as light touch receptors, by detecting the bending of hairs
11
Q
How do Free nerve ending sense itch?
A
Histamine receptors on sensory nerve endings detect histamine and alert your body
12
Q
What are Tactile discs?
A
Free nerve endings located in the deepest layer of epidermis
13
Q
What are Tactile discs associated with?
A
Large disc shaped epidermal (Merkel) cells
14
Q
What does a Merkel cell do?
2
A
- Detects stimulus
- Convert stimulus into a chemical message that is transmitted to sensory nerve endings
15
Q
What is the chemical messenger used by Merkel cells?
A
Serotonin
16
Q
Where are Tactile disks/Merkel cells most abundant in the body?
A
Finger tips
17
Q
Are the receptor fields of Tactile disks/Merkel cells small or big?
A
Small
18
Q
What are Tactile disks/Merkel cells good for?
A
Two point discrimination
19
Q
What are Tactile disks/Merkel cells sensitive to?
A
An objects physical features e.g. texture, shape and edges
20
Q
Where are Tactile Corpuscles located?
A
Papillary layer of the dermis
21
Q
Where are Tactile Corpuscles especially prevalent in the body?
A
Hairless skin e.g. - finger pads - lips - eyelids soles of feet
22
Q
What can the structure of Tactile Corpuscles be described as?
A
Encapsulated
23
Q
What are the structural features of an Encapsulated Tactile Corpuscle?
(3)
A
- Branching unmyelinated sensory terminals
- Terminals provided support by modified Schwann cells
- surrounded by a thin oval fibrous connective tissue capsule
24
Q
What do Tactile Corpuscles sense?
3
A
- Delicate/discriminative touch
- Light pressure
- Low frequency vibration (2-80 Hz)
25
Where are Lamellar Corpuscles located?
Scattered deep in the dermis/hypodermis
26
What are the structural features of Lamellar Corpuscles?
| 3
- Single dendrite
- Inside layers of collagen fibres/specialised fibroblasts
- Each layer separated by gelatinous interstitial fluid
27
What does deformation to the capsule of lamellar Corpuscles do?
opens pressure sensitive Na+ channels in sensory axons
28
What makes Lamellar Corpuscles rapidly adapting?
When inner layers covering the axon terminal are compressed they 'relax' quickly so action potentials are discontinued
29
What stimulates Lamellar corpuscles?
| 2
- Deep pressure
| - Vibration (around 250Hz)
30
Where are Bulbous Corpuscles located?
In the Demis/subcutaneous tissue
31
What are the structural features of Bulbous Corpuscles?
| 3
- Network of nerve endings
- Intertwined with a core of collagen fibres that are continuous with the dermis
- Capsule surrounding entire structure
32
What stimulates Bulbous Corpuscles?
| 2
- sustained deep pressure
| - stretching/distortion of the skin
33
What are Bulbous Corpuscles important for?
signalling continuous states of:
- deformation to tissue
- heavy prolonged touch/pressure signals
34
What are Bulbous corpuscles involved in at joint capsules?
Proprioception - degree of joint rotation
35
Where on the body is there a high density of Bulbous Corpuscles?
Around fingernails
36
What do Bulbous Corpuscles allow your grip to do?
Be modulated
37
What do Arteries do in context of the skin?
Supply blood to the skin and subcutaneous layer
38
Where do the branches of arteries extend?
They extend into the superficial layers of the dermis
39
What is the role of capillary loops?
| 2
- supply blood to the upper dermis/underside of the epidermis
- Drain blood into the venous plexus
40
Where is smooth muscle located?
In the walls of blood vessels
41
What controls smooth muscle in blood vessels?
Sympathetic nervous system
42
Where are Precapillary sphincters located?
At the start of capillary beds
43
What does Contracting smooth muscle of the Precapillary sphincter/Arteries do?
Restricts blood flow to the upper layers of the skin
44
What does Noradrenaline from the SNS act on in vascular smooth muscle in the skin?
Alpha 1 adrenergic receptors
45
What are Alpha 1 adrenergic receptors an example of?
G-protein coupled receptor (GPCR)
46
How do G-protein coupled receptors work?
They activate a secondary messenger system in the cell
47
How do GPCR's work on vascular smooth muscle tissue in the skin?
(3)
- Secondary messenger system leads to increased intracellular calcium
- Intracellular calcium leads to constriction
- Constriction leads to reduced skinflow
48
What is the result of less SNS activity in the skin?
| 2
- Relaxation/dilation of arteries to the skin
| - Increased skin bloodflow flow
49
What is the optimal body temperature?
37ºC
| Range of 36.5 - 37.5ºC
50
What happens to cells at 40 degrees?
| 2
- They become denatured
| - Lose ability to thermoregulate
51
What happens to cells when your body becomes too cold?
Nervous tissue lose function
52
What are the Primary mechanisms of heat transfer?
| 4
- Radiation
- Evaporation
- Convection
- Conduction
53
How is heat Transferred through radiation?
It is lost/gained through infrared rays
54
What % of heat loss is through Radiation?
60%
55
How is heat Transferred through Conduction?
Heat is transferred from/to objects that are in contact with the body
56
What % of heat loss to the air is due to Conduction?
15%
57
How is heat transferred through convection?
| 3
- Firstly by conduction
- Then warm air moves away and is replaced by cold air
- constant temperature gradient is maintained
58
How is heat lost through Evaporation?
Heat energy is transferred from the body to convert water from liquid to gas
59
What is the difference between water and air as a heat acceptor?
Water can absorb far more heat than air
60
What are Eccrine sweat glands innervated by?
Sympathetic cholinergic nerves
61
What are Sympathetic cholinergic nerves?
Nerves that release Acetylcholine
62
What is a muscarinic acetylcholine receptor?
Acetylcholine receptors that forms G protein-coupled receptor complex
63
What are only some Eccrine sweat glands stimulated by?
Adrenaline acting on Beta receptors
64
What is a results of Adrenaline acting on Beta receptors?
Nervous sweating
65
What are the bodily responses to temperature increase?
| 4
- Behavioural changes
- Vasodilation and shunting of blood to skin surface
- Sweat production
- Respiratory heat loss
66
What is the Preoptic area of the hypothalamus?
Area containing heat/cold sensitive receptors (central thermoreceptors)
67
What happens if blood temperature goes above set point?
Heat loss centre is activated
68
What are induced responses by the heat-loss centre?
| 2
- Decreased activation of SNS alpha 1 receptors leads to vasodilation
- Increase SNS cholinergic activation of mAChRs leads to sweating
69
Are radiation, conduction and convection effective heat loss mechanisms?
No
70
What happens when central thermoreceptors detect temperature below set point?
Heat gain centre is activated
71
What are induced responses by the heat-gain centre?
| 2
- Increased generation of body temperature
| - Conservation of body temperature
72
What are examples of Heat generating mechanism?
| 3
- Shivering
- Non-shivering thermogenesis
- increased thyroxine increase
73
What are the features of shivering?
| 3
- increased tone of skeletal muscles
- Above critical level shivering occurs due to oscillatory contractions between agonist and antagonist
- muscles are mediated by muscle spindles
74
What are the features of Non-Shivering Thermogenesis?
| 4
- Increased sympathetic nerve activity
- Increased circulating adrenaline/noradrenaline
- Increased cellular metabolism
- 'uncoupling' of oxidative phosphorylation
75
What are features of increased thyroxine in generating heat?
| 3
- Occurs in response to TRH/TSH
- Increased basal metabolic rate
- May take several weeks of cold exposure to ensue
76
What are Arrector Pili muscles innervated by?
Sensory nervous system Alpha 1 receptors
77
How do Arrector Pili muscles attach to hair follicles?
By linking the hair follicle to the upper Dermis
78
What happens when Arrector Pili muscle contracts?
| 4
- Pulls hair upright
- dimples the skin
- leads to goose bumps
- Compresses Sebaceous gland
79
What are examples of different types of burns?
| 4
- First-degree burn
- Second-degree burn
- Deeper Second-degree burn
- Third-degree burn
80
What layer(s) of skin do First-degree burns effect?
superficial, outer layer of the Epidermis
81
What are symptoms of First degree burns?
| 4
- Red/pink colouring
- Dry skin
- Pain
- Usually no blisters
82
What is the healing time of a First degree burn?
3-10 days
83
What layer(s) of skin do Second-degree burns effect?
Epidermis + varying amounts of dermis
84
What are symptoms of Second-degree burns?
| 4
- Red
- Blisters
- Moist
- Painful
85
What is required to aid healing a second-degree burn?
Good dressings, initially absorptive ones
86
What layer(s) of skin do Deeper second-degree burns effect?
Epidermis + dermis
87
What are symptoms of Deeper Second-degree burns?
| 5
- Red
- Blisters
- Moist
- Painful
- May include whiteish, waxy areas
88
What are effects of Deeper second-degree burns?
| 2
- Hair follicles/Sweat glands may remain intact
| - Some tactile receptors may be lost
89
What is the healing time of a Second-degree burn?
1-2 weeks
90
What is the healing time of a Deeper second-degree burn?
| 2
- One month
| - May have some loss of sensation/scarring
91
What layer(s) of skin do Third-degree burns effect?
Full thickness extending into the subcutaneous tissue
92
What are symptoms of Third-degree burns?
| 5
- Varied colour from waxy white to deep red or black
- Hard
- Dry
- Leathery
- No pain
93
Why is there no pain in the area of Third-degree burns?
Sensory nerve endings have been destroyed
94
What is the healing time of a Third-degree burn?
Weeks to regenerate skin and for scarring to occur
95
What may be an additional requirement to heal from a Third degree burn?
Skin grafting
96
What % of Total body surface area would the face be?
9%
97
What % of Total body surface area would each Upper limb be?
9%
98
What % of Total body surface area would the trunk (front and back) be?
36%
99
What % of Total body surface area would the Genitalia be?
1%
100
What % of Total body surface area would each Lower limb be?
18%
101
What are potential complications of Severe burns?
| 3
- Dehydration/Hypovolemic shock
- Infection/Sepsis
- Hypothermia
