Homeostasis Flashcards
Endotherm
Animal that maintains a constant body temperature (mammal that does homeostasis)
Ectotherm (definition)
Animal which regulates it’s temperature by exchanging heat with its surroundings (doesn’t do homeostasis) e.g. Reptiles
Temperature control:
When an endotherm becomes too cold, what happens?
- Thermoreceptors detect the fall in temperature
- sends an impulse to hypothalamus in the brain
- effector: arterioles muscles
- response: vasoconstriction of arterioles near skin surface so blood is kept away from surface preventing heat loss
- effector: hair erector muscles
- response: hairs stand up and trap warm air close to skin
- effector: skeletal muscles contract (shivering)
- response: generates heat by respiration
Temperature control:
When an endotherm becomes too hot, what happens?
- thermoreceptors detect rise in temperature
- sends an impulse to hypothalamus in brain
- effector: arterioles muscles
- response: vasodilation of arterioles near skin so blood flows close to surface allowing heat loss by radiation through the skin
- effector: sweat glands
- response: secretion of sweat so skin loses heat (from blood) by evaporation
- effector: salivary glands
- response: panting allows heat (from blood) to be lost by evaporation
Heart rate control:
Why and how does the heart rate increase?
- blood CO2 is high (due to respiration)
- detected by chemoreceptors in the aorta
- impulse sent to medulla oblongata
- impulse sent back to heart muscle
- SAN causes heart rate to speed up (via sympathetic nerves)
SOMETIMES: (in extreme situations)
-adrenal gland is stimulated to secrete adrenaline to speed up heart rate
Heart rate control:
Why and how does the heart rate slow down?
- blood CO2 is low
- detected by chemoreceptors in aorta
- impulse sent to medulla oblongata
- impulse sent back to heart muscle
- SAN causes heart rate to slow down (via parasympathetic nerves)
Which nervous system speeds things up?
Sympathetic nervous system
Which nervous system slows things down?
Parasympathetic nervous system
What does the sympathetic nervous system do?
Speed things up
What does the parasympathetic nervous system do?
Slows things down
What do endocrine glands do?
Secrete hormones into the blood
What kind of glands secrete hormones?
Endocrine glands
Hormone definition
A protein that is secreted into the blood, binds to target cells with the complementary receptor.
Can have a widespread (long term) effect and spread by diffusion
What do exocrine glands do?
Secrete a product via a duct onto the surface next to the gland (e.g. Saliva, sweat)
Stimulated by hormone secretion
E.g. Pancreatic secretions in small intestine
Is the pancreas an endocrine gland or an exocrine gland?
Both
Why is the pancreas an endocrine gland?
It secrete hormones
Insulin and glucagon to control blood glucose
Why is the pancreas an exocrine gland?
- enzymes are secreted (e.g. Amylase, trypsin)
- secretions are controlled by nerves and hormones
- pancreatic secretions go into small intestine
- pancreatic secretions make small intestine alkaline
Which two hormones regulate blood glucose?
Insulin and glucagon
Where are the alpha and beta cells?
In the islets of Langerhans in the endocrine tissue of the pancreas
When and where from is insulin secreted?
- secreted from Beta cells
- when blood glucose is too high
What happens when blood glucose is too high?
- high blood glucose is detected by beta cells
- insulin is secreted into the blood from beta cells in islets of Langerhans in pancreas
- insulin binds to receptors on liver cells
- activating carrier proteins, increasing membrane permeability to glucose
- allows glucose to be taken into cells
- activates enzymes involved in glycogenesis which converts glucose into glycogen
What happens when blood glucose is too low?
- low blood glucose is detected by alpha cells
- glucagon is secreted into the blood from alpha cells in the islets of Langerhans in the pancreas
- glucagon binds to receptors on liver cells
- activates enzymes used in glycogenolysis (converting glycogen to glucose)
- glucose diffuses into blood
What is Gluconeogenesis?
Making glucose from glycerol and fats when glucose is very low (in extreme situations)
How does adrenaline increase blood glucose concentration?
-adrenaline binds to a receptor on the cell membrane
(Adrenaline is too big to pass through cell membrane by diffusion)
(Adrenaline must use channel protein to pass into cell)
-inside cell, ATP is converted to cAMP
-cAMP activates the protein channel
-protein channel changes shape so adrenaline can pass through
-enzymes in the cell are activated
-glycogenolysis and Gluconeogenesis occur to make glucose
(Glycogenesis is inhibited)
