Homeostasis And Chemical Control In Mammals Flashcards
What is homeostasis?
The maintenance of a constant internal environment despite external change
What is negative feedback?
The reversal of a change to a steady state
Negative feedback flow diagram
Optimum condition Change away from op Receptor detects change Communication system informs effector Motor neurone Effector reacts to make change Negative feedback Back to optimum condition
The communication pathway
Stimulus Receptor Cell signalling Effector Response
What is positive feedback?
Increases change detected by receptors
Flow diagram of positive feedback
Optimum condition Change away from optimum Receptor detects change Communication system Effector reacts to increase change
The endocrine system: endocrine glands
Secrete hormones into the bloodstream
The endocrine system: exocrine glands
Secrete enzymes that are secreted outside the body
What is a hormone
Chemical messengers that act on particular target cells
What are the 2 types of hormones
Protein and peptide hormones
Steroid hormones
Protein and peptide hormones
Adrenaline insulin and glucagon
Not soluble in the lipid bilayer- can’t diffuse through so don’t enter the cell
Steroid hormones
Sex hormones
Can diffuse through the membrane and have direct effect on DNA
What does the adrenal gland do?
Secretes Adrenalin
What does adrenaline do?
Increase heart rate, stroke volume, vasoconstriction to non essential organs, relaxed smooth muscle in bronchioles and inhibit action of gut
Negative feedback loop for insulin control: Beta
Blood glucose levels up Beta cells as receptors and effectors Insulin released Body cells take up more glucose Blood glucose level declines
Negative feedback loop for insulin control: alpha
Blood glucose level drops
Alpha cells of pancreas release glucagon into blood
Liver breaks down glucagon and releases glucose
Blood glucose level rises
What does the hypothalamus do?
Monitors blood levels and hormones- responds by controlling the activity of the pituitary which secretes hormones
Pituitary gland: anterior lobe
Produces 6 hormones including FSH
Pituitary gland: posterior lobe
Stores and releases hormones from hypothalamus including ADH
Type 1 neurosecretory cells in the hypothalamus
Produce substances that stimulate the release of hormones from the anterior pituitary (which can be releasing factors or release inhibiting factors)
Type 2 neurosecretory cells in the hypothalamus
Produce secretions that are stored in the posterior pituitary gland which are released later as hormones
Hormones and the second messenger: protein and peptide hormones
Hormone binds to the receptor which is transmembrane as hormone cannot enter the cell. Enzyme/substrate complex= second messenger cAMP (Cyclic AMP.) Response. The second messenger is needed as the hormone can’t enter the cell
Hormones and the second messenger: steroid hormones
Receptor protein- diffusion into cell- hormone/receptor complex- can act as a transcription factor- protein synthesis
No need for second messenger
ATCH
Stimulates adrenal gland to secrete hormones
FSH
Stimulates ovaries to secrete oestrogen and development of ova
LH
Stimulates Ovulation
Prolactin
Stimulates milk production in mammary glands
ADH
Decrease urine volume to conserve water
Oxytocin
Stimulates contraction of uterus during childbirth
