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Define dynamic equilibrium
conditions remain stable within fluctuating limits
What are the 3 components of a homeostatic control system?
Monitor
Coordinating Centre
Regulator
What do negative feedback systems do?
make adjustments to bring the body back within the acceptable range or steady state; work to resist change
What do positive feedback systems do?
make adjustments to move system even further away from acceptable range; work to reinforce change
Why do we need excretion systems?
Some products of our metabolism can be harmful and need to be taken out of the system to avoid damage.
What is deamination?
removal of an amino group in protein metabolism resulting in ammonia
What is detoxification in the liver?
two molecules of ammonia are combined with carbon dioxide in the liver to form the less toxic urea, which can then be excreted by the kidneys
What supply blood to the kidneys?
Renal arteries
What is the general pathway of urine?
Aorta, renal arteries, kidney, ureters, urinary sphincter, urethra
What is urine?
filtrate of waste removed from blood in the kidneys
Label this diagram
What is the pathway of blood in the kidneys?
Afferent arteriole, glomerulus, Bowman's capsule, efferent arterioles, peritubular capillaries
What is the pathway of filtrate in the nephron?
Bowman's capsule, proximial tubule, loop of Henle, distal tubule, collecting duct
What are the 3 processes that produce urine?
Filtration
Reabsorption
Secretion
How does filtration of urine occur?
high pressure forces water and dissolved solutes out of blood at Bowman's capsule
How does reabsorption of urine occur?
In the proximal and distal tubules, there is selective reabsorption. The descending limb of the loop of Henle is permeable to water, and the ascending limb is permeable to salt.
How does secretion of urine occur?
Movement of waste into nephrons in the distal tubule via active transport.
What is ADH?
Anti-diuretic hormone - it controls the concentration of urine and is released into the bloodstream by the pituitary gland
What does increased ADH do?
More concentrated urine, less water output
What are osmoreceptors?
specialized neurons in the hypothalamus that detect changes in osmotic pressure
What is osmotic pressure?
The pressure required to prevent the flow of water across a semipermeable membrane via osmosis
What does a decrease in water intake do to blood?
Makes it more concentrated
How does the body know when to release ADH?
Osmoreceptors shrink as water enters the bloodstream, triggering a nerve response to the pituitary to send more ADH
What parts of the nephron are impermeable to water?
Distal tubule, collecting duct, ascending loop of Henle
What does ADH do?
causes the collecting ducts of the kidney to become permeable to water, reducing the volume of urine and concentrating the urine
How does the kidney regulate blood pressure?
Receptors in juxtaglomerular apparatus release renin, which converts angiotensinogen into angiotensin. Angiotensin stimulates release of aldosterone. Aldosterone causes the distal tubule and collecting duct, increasing osmotic gradient, more water moving out of nephron and increasing blood pressure.
How do kidneys help to maintain the carbonic acid-bicarbonate?
Carbon dioxide is actively transported from the peritubular capillaries to the nephron, where it combines with water to generate bicarbonate
What are hormones?
chemical regulators produced in one part of the body that affect cells in another part of the body
How are hormones classified?
According to their activation site, either target or nontarget
What are the properties of protein hormones?
amino acid chains of varying lengths
soluble in water
includes insulin
cyclic AMP
What are the properties of steroid hormones?
lipid compound
male & female sex hormones, cortisol
complex carbon rings
hydrophobic
lipid soluble
What happens in the posterior pituitary gland?
releases hormones such as ADH, oxytocin (produced by the hypothalamus)
What happens in the anterior pituitary gland?
Produces its own hormones, hypothalamus regulates release of them, like growth hormone and prolactin
How does the endocrine system react when blood sugar is high?
Insulin is released from beta cells in the pancreas, increasing permeability of organs to glucose, glucose converted to glycogen and used for storage
How does the endocrine system react when blood sugar is low?
Glucagon is released from alpha cells in the pancreas, causing liver to convert glycogen to glucose and release it into the bloodstream
Who are Frederic Banting and Charles Best?
Discovered insulin, linked it to diabetes
What is the body's short term stress response?
The adrenal medulla receives instruction to release adrenaline and noradrenaline, blood sugar rises, heart rate increases, blood vessels and irises dilate
What is the body's long term stress response?
Anterior pituitary releases ACTH, which travels to the adrenal cortex to release mineralocorticoids and glucocorticoids
What is a glucocorticoid?
associated with blood glucose levels (cortisol)
What is a mineralocorticoid?
associated with body fluid and blood pressure
What does thyroxine do?
T4 affects the rate at which glucose is converted into ATP and released as heat
What is hypothyroidism?
underactive thyroid
What is hyperthyroidism?
overactive thyroid
What is a goiter?
enlargement of the thyroid gland
How does the endocrine system regulate low metabolic rate?
Receptors in hypothalamus release TRH (thyroid releasing hormone), which stimulates pituitary to release TSH (thyroid stimulating hormone), which travels to thyroid and releases thyroxine, which increases metabolic rate.
How does the endocrine system regulate low calcium levels?
Low calcium levels stimulate the release of parathyroid hormone, which causes calcium levels to rise.
How does the endocrine system regulate high calcium levels?
Release of calcitonin takes up calcium from bones.
What are somatic nerves?
control skeletal muscles, bones and skin, voluntary
What are sensory vs motor somatic nerves?
sensory: relay information about environment to the CNS
motor: initiate appropriate response
What are autonomic nerves?
control internal organs, smooth muscle, involuntary
What are sympathetic vs parasympathetic autonomic nerves?
sympathetic: away from steady state
parasympathetic: return to steady state
What are glial cells?
cells in the nervous system that support, nourish, and protect neurons
What are sensory neurons?
sense and relay information from environment to CNS for processing, located in clusters outside of spinal cord
What are interneurons?
link other neutrons together, interpret and integrate sensory information
What are motor neurons?
relay information to effectors: muscles, organs and glands - produce responses
What are dendrites?
receive information, conduct nerve impulse toward the cell body
What is the cell body?
contains nucleus and organelles
What is the axon?
projects nerve impulses away from cell body
What is the myelin sheath?
white coat of fatty protein for insulation (like coating on conducting wires)
What are schwann cells?
specialized glial cells that form the myelin sheath
What are the nodes of ranvier?
areas between sections of myelin sheath where nerve impulse must jump
What is the neurilemma?
thin membrane surrounding all PNS neurons that promotes regeneration
What is the reflex arc?
Involuntary response to an external stimulus. Direct connection between sensory and motor neuron without connection to brain
What is an electrochemical impulse?
changes in charge that move through neutrons and stimulate other neurons or effectors
What is the resting membrane potential?
-70mV
What is an excited nerve potential?
40mV
What is action potential?
the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
Describe the permeability of the resting membrane
The resting membrane is more permeable to potassium than sodium. Potassium flows out more than sodium flows in
What is the charge of the inside of a nerve cell?
Negative relative to outside
When is a membrane polarized?
When it is in it's resting state, at -70mV
How does a membrane become depolarized?
An electrochemical impulse stimulates the sodium pumps to open and come rushing in, making the inside of the nerve cell positive relative to the outside
Which element does the sodium potassium pump favor?
The sodium, moving 2 potassium in and 3 sodium out per pump
How is the resting membrane potential restored?
The sodium-potassium pump pumps in 3 sodium and out 2 potassium, restoring polarization
How is the impulse transmitted?
The depolarization event moves along the membrane as a wave of depolarization
What is the refractory period?
a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation.
What is the threshold level?
the amount of stimuli required to create the action potential
How does intensity of an impulse vary?
Frequency
Different threshold levels
What are synapses?
Gaps between adjacent neurons.
What are neurotransmitters?
chemical messengers that cross the synaptic gaps between neurons
What is acetylcholine?
common excitatory neurotransmitter that acts by opening sodium ion channel
What is cholinesterase?
enzyme released from postsynaptic membrane - destroys acetylcholine and stops activity
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