45 1&2, 48 1-4, 49 2 Flashcards
endocrine system
chemical signalling by hormones: 1 of 2 communication systems
nervous system
neurons that transmit signals along dedicated pathways:
1 of 2 communication systems
4 types of cell signalling
endocrine, paracrine, autocrine, synaptic and neuroendocrine signalling
endocrine signalling
- reach target cells via blood stream (hemolymph)
- triggers response in target cells anywhere in the body
- maintains homeostasis, mediates response to environmental stimuli, regulates growth and development
local regulators
act over short distances and reach target cells solely by diffusion ex.cytokines either paracrine and autocrine
paracrine signalling
local regulators trigger a response in neighboring cells
autocrine signalling
local regulators trigger a response in the cells that diffuse them
synaptic signalling
neurons form specialized junctions called synapses with target cells ex. muscle cells and other neurons
neurotransmitters
produced at synapses, molecules secreted that diffuse a short distance to bind to receptors at target cells ex. sensation, memory, cognition, movement
neuroendocrine signalling
neurohormones secreted by specialized neurons that diffuse from nerve cell ending and enter the bloodstream hitting target cells anywhere in the body
pheromones
chemicals released into the external environment for communication
endocrine cells can be found in..
endocrine glands and dispersed in organs with other functions
endocrine glands
endocrine cells grouped in ductless organs ex. thyroid and parathyroid
exocrine glands
carry secreted substances on the surface of the body ex.saliva
list of endocrine glands
hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, testes
what are lipid soluble hormones + examples
diffuse across membranes of endocrine cells and outside cells they bind to transport proteins steroids: cortisol+thyroxine
what are water soluble hormones+examples
secreted by exocytosis polypeptides: insulin+epinephrine
signal transduction
the series of changes that converts the extra-cellular chemical signal to a specific intracellular response
epinephrine
due to short-term stressful situation secreted by adrenal glands also called adrenaline; causes liver to release glucose
many hormones elicit more than one
response
growth factors
stimulate cell proliferation and differentiation
nitric oxide
neurotransmitter and local regulator
prostaglandins
help sperms reach egg, help labor, regulate platelet aggregation, promotes fever and inflammation, and help maintain stomach lining
simple endocrine pathway
endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone
simple neuroendocrine pathway
stimulus is received by a sensory neuron which stimulates a neurosecretory cell which secretes a hormone into the bloodstream
negative feedback
a loop in which the response reduces the initial stimulus
positive feedback
reinforces a stimulus, leading to an even greater response
insulin
released when blood sugar is high and triggers cells to uptake glucose: made by beta cells
glucagon
released when blood sugar is low and triggers release of glucose into the blood from energy stores such as liver glycogen:made by alpha cells
diabetes mellitus
deficiency of insulin (type 1) or decreased response to insulin (type 2)
ganglia
simpler clusters of neurons
3 stages of information processing by the nervous system
sensory input, integration, and motor output
central nervous system (cns)
the neurons that carry out integration: includes the brain and the longitudinal nerve cord
peripheral nervous system (pns)
the neurons that carry infromation into and out of the cns
when bundled form nerves
sensory neurons
detect external stimuli or internal conditions
interneurons
form the local circuits connecting neurons in the brain, majority of the brain
motor neurons
transmit signals to muscle cells leading to contraction
membrane potential
the charge difference or voltage caused by opposite charges across plasma membrane
resting potential
membrane potential of a resting neuron
key ions in the formation of resting potential
potassium and sodium ions
sodium-potassium pumps
maintain potassium and sodium ion gradients
ion channels
allow ions to diffuse back and forth across the membrane
equilibrium potential (Eions)
the magnitude of the membrane voltage at equilibrium for a particular ion
nernst equation
Eion= 62mV(log [ion] outside/[ion] inside)
gated ion channels
ion channels that open or close in response to stimuli
hyperpolarization
the increase in the magnitude of the membrane potential which makes the inside of the membrane more negative
depolariztion
the reduction in the magnitude of the membrane potential
graded potential
magnitude varies with the strength of the stimuli
action potential
a massive change in membrane voltage
voltage-gated ion channels
opening or closing when the membrane potential passes a particular level, cause action potentials
threshold
when a depolarization increases the membrane voltage to a particular value where active potentials occur
5 stages of action potential
resting state,depolarization, rising phase ,falling phase, and undershoot
3.rising phase
depolarization opens sodium channels, potassium remains closed, inside positive
2.depolarization
stimulus opens sodium channels, depolarizing the membrane
1.resting state
all gated channels are closed, ungated channels maintain the resting potential
4.falling phase
most sodium channels inactivated, potassium channels are open, inside of the cell negative
5.undershoot
sodium channels close, some potassium open, membrane returns to resting state
refractory period
time when a second action potential cannot be activated
conductance speed is increased in axons by
width
myelin sheath
electrical insulation that surrounds axons
myelin sheaths are produced by-
2 types of glia: oligodendrocytes and Schwann cells
slatatory conduction
the mechanism for action potential propagation
electrical synapses
- contain gap junctions
- allow electrical current to flow directly from one neuron to another
chemical synapses
release of a chemical neurotransmitters y presynaptic neuron which packages them in synaptic vesicles which then diffuses along synaptic cleft
ligand-gated ion channel
also called an ionotropic receptor, in postsynaptic membrane; allows specific ions to diffuse
excitatory postsynaptic potential (EPSP)
a depolarization which brings the membrane potential toward threshold caused by ligand-gated ion channel
inhibitory postsynaptic potential (IPSP)
ligand-gated ion channel when selective
temporal summation
two EPSPs occur at a single synapse; they add together
spatial summation
simultaneous ESPS produced at different synapses
biogenic amines
neurotransmitters synthesized from amino acids; includes norpinephrine
neuropeptides
relatively short chains of amino acids
sleep
learning and memory
reticular formation
arousal and sleep
superchiasmatic nucleus
coordinates circadian rhythm, in hypothalamus
emotions controlled by
limbic system
amygdala
most important for emotion memory
