homeostasis Flashcards
negative feedback
2
- Primary mechanism of homeostasis
- A stimulus (from change in internal/external environment) triggers a response that will compensate that change to maintain equilibrium
positive feedback
3
- A response of a system that acts to increase the effect of any changes made to the system
- Sets in motion a chain of events that intensify a change from an original condition
- Usually does not result in homeostasis; generally associated with system instability
stimulus
Change internal/external environment
sensor
located in the tissues and organs of the body. A signal is sent to the coordinating centre once an organ begins to operate beyond its normal limits
integrator
control/processing centre that compares existing conditions to optimal functioning conditions
effector
if the environmental condition is outside the set point, the effector makes a response to restore normal balance
urine
Fluid consisting of water and waste (NH3) formed in the kidneys
urine formation steps
filtration, reabsorption, secretion
filtration (urine)
movement of fluids from the blood in the glomerulus to the Bowman’s capsule through a selectively permeable membrane.
reabsorption (urine)
transfer of fluids from nephron into peritubular capillaries (return substances to the blood)
secretion (urine)
transfer of fluids (wastes/toxins) from peritubular capillaries (blood) and interstitial fluid into nephron.
deamination
- In situations of excess protein intake, deamination is used to break down amino acids for energy.
- The amino group is removed from the amino acid and converted to ammonia.
- Byproduct= NH3 (ammonia)
pituitary gland
- Located within the cranium, just below the brain
- Referred to as the “master gland” because it produces and secretes hormones that control most other endocrine glands and some bodily processes
two major lobes
anterior and posterior
anterior lobe
- produces its own hormones
- secretion of hormones is controlled by hypothalamus producing releasing or inhibiting hormones (neurohormones)
posterior lobe
stores and releases two hormones produced by the hypothalamus
oxytocin
Oxytocin is involved in reproduction. It stimulates the release of milk from mammary glands for nursing mothers. During birth, the hormone acts on the uterine and promotes contractions.
ADH( vasopressin)
Antidiuretic hormone (ADH) stimulates the kidney cells to absorb more water from the urine, which increases the volume of the blood. So, it controls the water reabsorption in the kidneys.
neuron
Specialized nerve cell that is the functional unit of the nervous system allowing for an organism to receive and respond to internal and external stimuli
cell body
- contains the nucleus
- synthesizes most of the neuron’s proteins, carbohydrates, and lipids
dendrites
highly branches projection of cytosol that carries signals from outside the neuron toward the cell body
axon
3
- an extension of cytosol that carries impulses away from the cell body and to another neuron or an effector
- usually branch at their tips that end in small button-like swellings called axon terminals
- form bundles that make up nerve fibres with connective tissue
axon terminals
points if connection that enable signals to be transmitted from one neuron to another neuron or an effector
schwann cells
a type of glial cell that wraps around the axon forming a myelin sheath
myelin sheaths
electrical insulators due to theie high lipid content
nodes of ranvier
2
- the gaps between sections of myelin sheaths; axons are directly exposed to extracellular fluid
- a combination of gaps and insulated portions speeds the rate at which electrical impulses move along the axons
steps involving synaptic transmission using a neurotransmitter
7
- Impulse reaches the synapse from the axon.
- Impulse stimulates synaptic vesicles to move to the presynaptic membrane.
- Synaptic vesicles dump neurotransmitter substances into the synaptic cleft.
- Neurotransmitter substance diffuses across the cleft.
- Neurotransmitter substance fits into receptor sites on postsynaptic membranes.
- An enzyme cleaves the neurotransmitter substance and clears out the synaptic cleft.
- An action potential is stimulated at the postsynaptic membrane and impulse travels down dendrite.
adrenal medulla
2
- Regulated by nervous system
- Adrenal medulla produces epinephrine (adrenaline) and norepinephrine
epinephrine
4
- glycogen breakdown into glucose -> increases blood sugar level and results in a sudden
burst of energy - increases heart rate and respiratory rate and cell metabolism
- vasodilation -> increases blood supply oxygen and nutrients to tissues (i.e., muscle)
- retinal dilation -> enhanced visual perception
norepinephrine
2
- has the same effects as epinephrine, also increases blood pressure
- affects the amygdala – an attention centre in the brain
function of adrenaline
Adrenaline (epinephrine) is a hormone your adrenal glands make to help you prepare for stressful or dangerous situations. Adrenaline rush is the name for the quick release of adrenaline into your bloodstream. This gets your body ready for a “fight or flight” response.
