Integument physiology Flashcards
What are some functions of the integument?
Protection, Immune defence, Sensing environment, Thermoregulation, Storage and excretion, Communication, Camouflage and selective permeability
Mechanoreceptors
detect stimuli such as touch, pressure and stretching
Ruffini’s end organ
detects skin stretching
Krauses end bulb
detects cold
Meisner’s corpuscle
detects vibrations
Pacinian corpuscle
detects pressure and fast vibrations
Nociceptors
Free nerve endings that can detect pain
Thermoreceptors
free nerve endings that can detect hot or cold
Homeostasis
Maintenance of constant conditions within the body’s internal environment
How much of an adults body mass is water
60-65%
What part of the brain controls homeostasis?
The Hypothalamus
Hypothalamus
Coordinates activities of autonomic nervous system (ANS).
* Sympathetic (fight or flight).
* Parasympathetic (rest and digest).
* Enteric nervous system.
Controls a major part of the endocrine system.
» Detects the osmolarity of the interstitial fluid in the brain via osmoreceptors.
» Monitors brain temperature
Why is thermoregulation important?
» Enzymes only work at optimum temperature.
» Below 34°C animals unable to regulate their own temperature.
» At 27 to 29°C cardiac fibrillation and death!
» An increase of temperature to 45°C can cause fatal brain lesions.
» Knowledge of this can improve patient safety
Hypothermia
below normal body temperature
Hyperthermia
above normal body temperature
Fever/Pyrexia
reset of hypothalamic set point to higher temperature, enhances leucocyte
Thermoregulation
negative feedback mechanism
How do animals produce heat?
» By-product of all metabolic processes.
* Eventually all food energy is converted to heat
either directly or…
» Exercise.
* Work done converted to heat energy.
» Eating.
* Supply of energy, but also digestion is work.
» Muscle contraction (shivering thermogenesis).
* As a means of increasing metabolic heat in
response to a drop in temperature where
antagonistic muscles produce no useful work.
» Brown adipose tissue (non-shivering
thermogenesis).
» (Fever
* Changing the hypothalamic set point to aid in
fighting infection).
Non-Shivering Thermogenesis
» Increased heat production via increased
metabolism.
» In response to chronic cold external factors
» Mediated via:
* Increased thyroxine secretion (hormone from
thyroid gland).
* Increased sympathetic (ANS) activity
(norepinephrine).
* Increased metabolism of lipids in response to
circulating catecholamines
(norepinephrine/epinephrine).
» Brown adipose tissue.
Where is Brown Adipose Tissue located?
subcutaneous region between scapulae and around kidneys and myocardium
Why are lipids near Mitochondria
facilitates rapid store of energy into heat energy
What stimulates Brown Adipose Tissue
circulating catecholamines and norepinephrine secreted from sympathetic nerve endings
What are the 3 ways animals lose heat?
Radiation, Conduction and Convection and Evaporation
Radiation
when the body is warmer than the environment they lose heat by emission on infra-red emission
Conduction and Convection
Directly from body surface to cooler objects in contact with the
animal.
* Transfer of heat by warm air to cooler air.
Evaporation
Only form of heat loss when ambient temperature equals or is
greater than body temperature.
* Evaporation of 1L of water requires 2.43 kJ.
* Panting.
* Sweating.
Brown Adipose Tissue
Specific to mammals (not present in other vertebrates species), predominantly in neonates, present in small hibernating mammals in adulthood, darker colour due to a higher density of mitochondria (smaller numerous lipid droplets)
Panting
Patterns to increase heat loss through evaporation
Turbinates
tiny structures inside the nose that become engorged along with respiratory and oral mucosa
Dead space in lungs
volume of air that is not used for gas exchange
Sweating
» Important means of thermoregulation in horses and cattle (from
apocrine sweat glands).
» Important means of thermoregulation in primates including
humans (from eccrine sweat glands).
Can cats sweat?
Yes but glands are confined to paws, lips, chin and perineum
Cutaneous arteries
volumes of skin and subcutaneous tissue supplied by branches of an artery that perforates the body fascia.
Three plexus in the skin
Deep or subcutaneous, Middle and Superficial
Heat Transfer within the body
Tissue is a poor conductor of heat. » Heat transported by the blood. » Heat produced primarily in muscles and the
liver.
» Heat lost through skin and respiratory tract as
very good blood supply with many small vessel
close to the body surface.
» Rise in core body temperature increases blood
flow to the skin.
» Drop in core body temperature decreases flow
and fur or plumage are raised
(piloerection/goose bumps) to trap more air as
insulation.
» Sympathetic nervous system regulates blood
flow and piloerection
Counter-Current Exchange
Peripheral vessels dilate and transfer heat to the environment
Carotid Rete
The carotid rete consists of a compact network of intertwined, freely anastomosing arteries, and is related to the branches of the trigeminal nerve. Seen in cats, pigs, chickens and dogs- not in horses and primates
Function of brain cooling
During selective brain cooling, cool
venous blood from the nasal mucosa
drains into the cavernous sinus via the
angularis oculi vein (as well as some
deeper veins).
» Can be bypassed in periods of high
sympathetic activity.
Guttural pouch
Air filled sac in the brain that cools down the blood- only found in horses
