Exam 2 Flashcards
stressor
anything that disrupts homeostasis
stress response
what is it
physiological and behavioral responses that attempt to reestablish homeostasis
evolved to help with stressor and bring back to homeostasis
general adaptation syndrome
1 alarm reaction stage
2 resistance stage
3 exhaustion stage
what does stress response rely on
adrenal gland
what is the inside of the adrenal gland called
adrenal medulla
adrenal medulla
made up of modified neurons
inner
secretion of catecholamines
what is the outer part of adrenal gland called
adrenal cortex
adrenal cortex
outer
made up of endocrine tissue
secretion of glucocorticoid (steroid hormone)
neuroendocrinology of stress response
integration of 2 systems
1 sympathetic branch of autonomic nervous system
2 HPA axis- endocrine
1 alarm reaction stage
activated within seconds of stressor appearing
catecholamine secretion
fast acting
“fight or flight” response
what catecholamines are secreted with alarm reaction stage
1 norepinephrine
2 epinephrine
1 norepinephrine
from where
from adrenergic neurons throughout body
2 epinephrine
from where
from adrenal medulla derived from tyrosine
what does the sympathetic branch release
catecholamine
what does the HPA axis release
glucocorticoid
cortisol
corticosterone
what are additional hormones secreted when stress response is activated
1 beta- endorphins
2 vasopressin
3 prolactin
1 beta endorphins
function
pain suppresion
2 vasopressin
function
increases blood pressure
3 prolactin
function
unclear function
catecholamine functions
7
have a variety of effectors
1 increase blood glucose levels
2 increase alertness and memory retention
3 increase oxygen intake
4 increase free fatty acids
5 increase blood flow to muscles used in movement
6 increase HR and BP
7 inhibition of digestion and pain perception
2 resistance stage
activated within minutes to hours; if stressor continues
activation of hypothalamic pituitary adrenal axis
HPA axis
hypothalamic pituitary adrenal axis
stressor hypothalamus secretes corticotropin releasing hormone (CRH) travels to anterior pituitary secretes adrenocorticotropic hormone (ACTH) travels to adrenal gland adrenal cortex secretes glucocorticoids which includes cortisol, corticosterone
what are the target tissues for glucocorticoids that are secreted
liver, skeletal muscle
what happens when glucocorticoids reach appropriate level
negative feedback at hypothalamus and anterior pituitary
glucocorticoids
what are they
how is it moved through blood
what kind of receptors
corticosterone and cortisol (steroids)
moved through blood via carrier
intracellular receptors
what moves corticosterone and cortisol through blood
corticosterone binding globulin (CBG)
what happens when hormone binds to receptor
glucocorticoids
hormone binds to receptor
receptor hormone complex activates or suppresses gene transcription
alteration of protein leads to response
has variety of effects in the body
glucocorticoid effects
3
1 increase blood glucose
2 breakdown of protein and fats
3 suppress immune response and inflammation, reproduction, digestion
all these effects evolved to promote escape from stressor
what does increased blood glucose do in the stress response
induction of gluconeogenesis
reduction of cellular glucose uptake
3 exhaustion stage
if stressor continues for days, weeks, months, or years
long term or repeated
continued secretion of epinephrine, norepinephrine, and cortisol
( we did not evolve for this kind of thing, creates “wear and tear” on the body)
what kind of stress is alarm reaction and resistance stages
acute stress
what kind of stress is exhaustion stage
chronic stress
what are effects of acute stress 6
increased energy increased cardiac output inhibited digestion inhibited reproduction immunosuppression enhanced cognition
what are effects of chronic stress
6
fatigue, myopathy hypertension ulcers infertility loss of disease resistance neural degeneration
physical vs psychosocial stress response
we initiate stress response for psychosocial situations
same hormones secreted
same effects on body
but the stress response evolved for physical stress not psychosocial
parts of neuron
1 cell body 2 axon hillock 3 axon 4 axon terminal 5 dendrites
1 cell body
location of nucleus and organelles
2 axon hillock
where action potential or signal generated
high number of Na+ channels
3 axon
carries action potential
4 axon terminal
release of neurotransmitters
communication with other neurons/effectors
5 dendrites
where neurotransmitters bind from other neurons receive signals from other neurons
resting membrane potential
voltage (charge) difference across cell membrane when cell is at rest
slightly negative
what is resting membrane potential due to
gradient of Na+ and K+ between intracellular and extracellular environment
cell membrane is more permeable to K+ than Na+ leads to K+ leaking out
action potential
temporary reversal of voltage (charge) inside of the cell
voltage within cell becomes temporarily positive
“signal firing”
steps to an AP graph
1 RMP- all channels closed, Na+ and K+ 2 depolarization 3 repolarization 4 hyperpolarization 5 return to RMP
2 depolarization
Na+ channels open, Na+ rushes into cell, K+ channels closed
3 repolarization
Na+ channels closed, K+ channels open
K+ rushes out of cell
4 hyperpolarization
“overshoot” K+ rushes out
all or none principle
threshold must be reached to generate AP
if stimulus is able to depolarize the membrane to reach threshold, all the steps that lead to AP will happen without stopping
graded potentials
changes in membrane potential that vary with stimulus strength
can be summed to increase overall strength
what happens if graded membrane potential is strong enough
threshold may be passed and changed to AP
where do graded potentials occur
conducted only locally and then dies out (rather than propagating all along axon like AP
action potential propagation
a single AP involves only a small portion of plasma membrane but it propagates because each AP stimulates an AP in an adjacent area
where does propagation occur
from axon hillock to axon terminal
only goes in one direction
refractory period
unidirectional AP propagation due to refractory period
period of time where a cell is unable to generate another AP
what causes a refractory period
temporary inactivation of Na+ channels
1 absolute refractory period
interval of time where an AP cannot be generated no matter how large the stimulus
2 relative refractory period
interval of time where another AP “could” be initiated, but would require a greater stimulus
strength of signal
stronger signal result in a greater frequency of APs (not larger APs)
neural tissue
neuron
neuroglia
neuron
function
generate, send and receive neural signals
neuroglia
function
support and protection of neuron
myelin sheaths that surround axons of some neurons
transmission of neural signal
AP always propagates towards axon terminals
myelin sheath
surround axon
nodes of Ranvier
gaps between myelin sheath
neuroglia
types
oligodendrocyte (CNS) Schwann cell (PNS)
myelin is
lipid-rich and insulates axon, whitish
what does myelination of an axon do
speeds up AP conduction
saltatory conduction
from one node of Ranvier to the next one “jumps”
AP only occur at NoR
what is concentrated at NoR
voltage gated Na+ and K+ channels
do myelinated regions have Na+ and K+ channels
have almost none
where do unmyelinated axons have Na+ and K+ channels
along its length, no saltatory conduction, slower progagation
myelination and AP conduction speed
faster conduction in myelinated axons
thick myelin sheath means faster conduciton
axon diameter and AP conduction speed
greater axon diameter means faster conduction
greater surface area for Na+ channels
synapse
junction between 2 cells
types of synapse
neuron and neuron
neuron and effector (muscle or gland)
what does the presynaptic neuron do
send signal
what does the post synaptic neuron do
receives signal
1 electrical communication
gap junctions
allows ions to flow directly from one cell to another
what forms gap junction
connexons channels
2 chemical communcation
very common
conduct signal via neurotransmittors
neurotransmitters
6 types
1 acetylcholine 2 monoamines 3 amino acids- GABA 4 purines 5 neuropeptides 6 gases
types of chatecholamines
epinephrine
norepinephrine
dopamine
steps of NT release
1 AP arrives at the axon terminal
2 this causes voltage gated Ca++ channels to open, causing Ca++ to rush in
3 influx of Ca++ causes vesicles with Ach to release Ach into the synaptic cleft
4 Ach diffuses across the cleft
5 Ach binds to ligand gated Na+ channels on PSN
6 Na+ rushes into PSN which causes depolarization of PSN
responses to NTs: Excitatory vs Inhibitory post synaptic potential
what does it depend on
responses to PSN to a NT depends on NT secreted and receptors on PSN
excitatory PSP (EPSP)
results in depolarization of PSN due to influx of Na+
stimulatory/excitatory effect on PSN
inhibitory PSP (IPSP)
results in hyperpolarization of PSN due to influx of Cl- or efflux of K+
inhibitory effect on PSN
regulation of NT levels
rapid NT removal from cleft
NT must be inactivated or removed from the cleft for PSN to receive additional signals
reuptake proteins on PrSN axon terminal bring NTs back for breakdown and recycling
what does acetylcholinesterase breakdown
acetycholamine
what does monoamine oxidase breakdown
monoamines
blockage of NT uptake (drugs)
SSRIs
widely used as antidepressants and anxiety
blocks reuptake of serotonin which causes serotonin to spend more time in the cleft which means its able to produce longer lasting effects
other influences on neurons
neuromodulator
axoaxonic synapse
neuromodulator
do not cause EPSP or IPSP
instead depress or enhance effects of NTs
axoaxonic synapse
axon of neuron synapses with presynaptic neuron of another neuron
increase or decrease release of NT
summation of signals
graded potential summate at the trigger zone (axon hillock)
must reach threshold to propagate (AP) along axon
1 spatial summation
multiple stimuli at different spots
2 temporal summation
multiple stimuli at different times
grand postsynaptic potential (GPSP)
add all signals together to get a response
neural circuits
what is it
neurons linked through complex pathways
1 convergent neural circuit
a single neuron that has many other neurons synapsing on it
2 divergent neural circuit
axon has many branches of its terminals so it influences many other neurons
reflex
involuntary response to stimulation, homeostatic,
what is the goal of autonomic reflex
maintain BP
what is the goal of somatic reflex
moving away from a painful stimulus
reflex arc
basic functional unit of nervous system
pathway of reflex arc
reception of signal
production of response
receptor
detects stimulus
sensory/afferent neuron
conducts AP to CNS
interneuron
relays signal to motor neuron
motor/efferent neuron
conducts AP to effector
effector
carries out response
reflex arc varies in complexity
monosynaptic reflex arc
polysynaptic reflex arc
monosynaptic reflex arc
sensory neuron synapses directly with motor neuron
example of monosynaptic reflex arc
patellar reflex
polysynaptic reflex arc
involves interneuron within spinal cord
stretch reflex
contraction of muscle in response to stretch
patellar reflex
1 receptor- muscle stretch detected by muscle spindle, responds to stretch of quads
2 sensory neuron- carries signal to spinal cord
3 alpha motor neuron- sensory neuron synapses directly with alpha motor neuron, rapid contraction of opposing original stretch initiated
4 effector- quads
muscle spindle
bundle of skeletal muscle fibers
responses of reflex arc
excitatory
inhibitory
excitatory reflex arc response
muscle contraction
inhibitory reflex arc response
muscle relaxes
signal integration
ascending tracts within spinal cord carries signal to brain
descending tracts modify reaction
gamma motor neuron
gamma motor neuron
transmission from spinal cord
regulates sensitivity of muscle spindle
withdrawl reflex
removal of limb from painful stimulus
reciprocal innervation- excitatory interneurons, contraction of flexor muscles, inhibitory interneurons- relaxation of extensor muscles
