test 1 Flashcards
homeostasis
constant stable internal environment distinct from the changing external environment
how is homeostasis achieved?
regulatory mechanisms
disease
failure to maintain homeostasis
what types of regulatory mechanisms are possible?
positive feedback (amplifies stimulus); negative feedback (corrects the stimulus)
stimulus (input)
change of a variable in the environment
response (output)
result of the regulatory system
regulatory mechanism
response to stimulus
negative feedback mechanism
response corrects a stimulus
what are the components of negative feedback?
stimulus, receptor, control centre, effector, response
receptor
detects change
control centre (integration centre)
processes information, makes a descision, sends a command
effector
muscle or gland that performs the response
thermoregulation - negative feedback
stimulus: rise in temperature/drop in temperature
- receptors in skin detect change
- brain makes decision
- sweat glands and blood vessels dilate (sweat)/muscles contract and blood vessels constrict
reponse: decrease in body temp and maintain homeostasis or increase in body temp and maintain homeostasis
glucose - negative feedback
stimulus: low blood glucose
- alpha cells in pancreas act as receptor and control centre and secrete glucagon
- effectors are found in the liver
response depends on glucagon or insulin
- glucagon = break down glycogen and form glucose from proteins which are released into blood cells
- insulin = removes glucose from blood by increasing use by cells (ATP formation+ anabolic reactions + store glucose)
positive feedback mechanism
amplifies the stimulus, once started they must go to completion
examples of positive feedback
blood clotting, labour
what are the 2 types of nervous tissue cells
neuron and neuroglia
neuron function
receive and transmit electrical impulses (action potential)
what are the components of the cell body of the axon?
nucleus, cytoplasm, nissl bodies, neurofibrils, neurotubules, dendrites
nucleus (neuron)
contains DNA, sometimes nucleolus
cytoplasm (neuron)
occupies cellular space
nissl bodies
clusters of RER responsible for manufacturing proteins
neurofibrils
assembled neurofilaments, structural proteins
neurotubules
responsible for cellular transport, also structural proteins
dendrites
branch off cell body, highly specialized structures, processes that receive info
axon components
axon hillock, axoplasm, axon collateral, telodendria, neurotransmitters, myelin sheath, nodes of ranvier
axon
where the nerve impulse propagates down to be transmitted
axon hillock
where the cell body tapers to become the axon, integration area
axoplasm
cytoplasm in the axon
axon collateral
branch off the axon
telodendria
branches at the distal end of the axon
neurotransmitters
chemical signals released from the synaptic terminal
myelin sheath
multiple membrane layer that wraps around the axon; protects and insulates, increases speed of NT
node of ranvier
gaps along the myelin sheath, where collaterals arise and nerve impulse is transmitted
- PNS: composed of Schwann cells
- CNS: oligodendrocyte
saltatory conduction
jumping conduction
function of neuroglia
supports the neuron
how many neuroglias does the neuron need to function
about 10
components of neuroglia (CNS)
astrocyte, oligodendrocyte, microglia, ependymal
astrocyte
provides 3D framework & controls environment (forms BBB)
oligodendrocyte
myelin sheath
microglia
immune function
ependymal
epithelial-like cells that line fluid-filled canals and cavities, produces cerebrospinal fluid
components of neuroglia (PNS)
satellite cells, schwann cells
satellite cells
astrocytes of PNS
schwann cells
myelin sheath
3 structural neuron classifications
unipolar, bipolar, multipolar
unipolar
one processs, exclusive to sensory neurons
bipolar
one axon, one dendrite; only found in eye and ear
multipolar
most neurons are multipolar
3 functional neuron classifications
sensory, inter, motor
sensory neurons
deliver information
interneuron
only in CNS, make decision
motor neurons
sends information to muscles
membrane potential
unequal charge distribution across the membrane
where does nerve impulse start?
axon hillock
what contributes to formation of membrane potential?
membranes are barriers to charges, high potassium in cell, high sodium outside cell, negatively charged proteins inside cell
which cells have ion gated channels?
nerve and muscle cells
resting membrane potential
polarized, -70mV
opening of sodium channels
depolarized, -55mV
opening of potassium ion channels
hyperpolarized (graded potential); repolarized (action potential), +30mV
sodium potassium ATP-ase
pumps 3 sodium out, 2 potassium in, forming membrane potential
chemically gated ion channels
opened or closed by neurotransmitter or hormone
voltage gated channels
opened or closed by change in membrane potential
depolarization
potential moves to threshold, becomes more positive
hyperpolarization
moves away from threshold, becomes more negative
repolarization
returns to resting state
hyper-repolarization
more negative than resting, overshoot
threshold
depolarization event which triggers opening of sodium voltage gates, threshold occurs at -55mV
refractory period
membrane cannot response to stimulus while sodium gates are open
action potential
all or nothing
graded potential
varies in magnitude, fades over time, can be summated
propagation
transmission of nerve impulse
epsp: excitatory post synaptic potential
graded potential depolarization event
ipsp: inhibitory post synaptic potential
graded potential hyperpolarization event
how does nervous system detect changes in environment?
opening of gated ion channels creates change in membrane potential
steps of action potential:
resting membrane (-70mV), depolarization (sodium channels open, -55mV), repolarization (+30mV, sodium channels close and potassium channels open), hyperpolarization (potassium channels close, -70mV)
absolute refractory period
period in action potential when membrane cannot respond to second stimuli
relative refractory period
period in action potential when membrane CAN respond to second stimulus if strong enough when threshold is reached
what happens when chemically gated potassium channels open?
potassium moves out, hyperpolarixation, IPSP
what happens when chemically gated sodium channels open?
sodium moves in, membrane potential depolarizes, EPSP
chemically gated channels
found on dendrites and cell body, neurotransmitter driven, open and closes by gates, part of graded potential
voltage gated channels
part of action potential, open and closes by gates, found along the axon, threshold driven
3 functional regions of synapse
axon terminal of presynaptic neuron (neurotransmitters in vessicles), synaptic cleft (space across which NT is diffused), motor end plate (receptors for NT)
steps at the synapse
1- action potential arrives
2- voltage calcium gates open and calcium moves in
3- calcium triggers release of neurotransmitters from vessicles in axon terminal of presynaptic neuron
4- neurotransmitters bind to receptors on motor end plate (post synaptic neuron) and open chemically gated ion channels, producing EPSP or IPSP
5- EPSP may or may not create action potential in post synaptic neuron
three types of muscle tissue
skeletal, smooth, cardiac
skeletal muscle function
produce movements of skeleton, maintain posture, stabilize joints, generate heat, nutrient reserve
characteristics of skeletal muscle
excitable, extensible, contractible, elasticity
muscle (organ) component
muscle, connective, nerve, tissue
how are muscles are attached to bones?
epimysium fuses to the periosteum
how are muscles indirectly attached to bones?
connective tissue extending beyond bone forming a tendon or aponeurosis
sarcolemma
cell membrane
t tubules
enfoldings of sarcolemma which encircle sarcolemma
myofibrils
bundles of 4-20 myofilaments
myofilaments
actin & myosin
sarcoplasmic reticulum
wraps each myofibril (SER)
sarcoplasm
cytoplasm
cisternae
sac-like structures of SER, stores calcium, encircled by t tubules
triad
t tubules + 2 cisternae junction site, where electrical signal transfers
glycosomes
granules of glycogen
fasciles
bundle of myofibrils
sarcomere
contractile unit of muscle fiber, resting length of 2um, consists of alternating light and dark bands, reflects the ordered arrangement of myofilaments
A band
dark band, myosin (think filaments) plus overlapping actin
I band
light band; actin (thin filaments)
Z line
holds actin in place
M line
holds myosin in place
H zone
area of myosin with no overlap
myosin
bundles of rod-like tails with globular heads; contains cross-bridges/form cross-bridges with actin
titin
elastic filaments, return filaments to resting length
actin
provides binding sites for cross bridge formation
troponin
binds calcium shifting tropomyosin
tropomyosin
covers actin binding sites at rest
atp
activates the myosin
calcium
binds to troponin, stored in cisternae, released with electrical signal, pumped back into cisternae
muscle contraction steps
1- calcium is released into cytoplasm, trigerred by electrical impulse that travels down t tubules into cisternae. calcium binds to tropomyosin exposing actin binding sites
2- myosin heads are activated (hydrolyze atp) and bind to exposed actin sites, forming a crossbridge
3- myosin head changes shape (bend/flexes) when binded. as shape changes, myosin pulls actin with it. adp + p falls out of myosin head. POWER STROKE
4- atp binds to myosin head breaking cross bridges
5- cycle repeats as long as atp and calcium are available
rigormortis
occurs after death, cross bridges cannot detach because no more atp
muscle contraction (synapse)
1- electrical signal travels down the axon of neuron and reaches axon terminal
2- axon terminal forms a synapse with the muscle cell
3- signal is transferred, calcium gates open trigerring release of NT - acetyl choline (Ach)
4- NT binds to motor end plate
5- NT binding triggers opening of sodium channels, formation of electrical signal in muscle cell
6- acetyl choline esterase removes Ach from synapse
signal in muscle fiber
1- electrical impulse travels down sarcolemma
2- signal travels down t-tubules
3- signal opens calcium channels at triads and calcium moves into sarcoplasm
4- calcium binds to troponin, results in shape change pulling tropomyosin off binding sites
5- cross bridges form
tension in muscle
pull on tendon that overcomes resistance
wave summation
occurs when 2nd stimulus occurs before relaxation is complete (ex: muscle twitch)
stimulus-contraction cycle
latent period - 2ms: ca release
contraction phase - 15ms: increased tension (cross bridge formation)
relaxation phase - 225 ms: ca levels drop, tension returns to resting state
incomplete tetanus
quivering contraction
complete tetanus
sustained max
motor unit
group of muscle fibers controlled by one neuron (fine motor: 4-6 units, gross motor: 1000-2000 units)
epithelial tissue
function: cover
structure: thin (diffusion), smooth (friction), tight fitting cells with no spaces (creates boundary with environment; protection), many layers (wear and tear)
location: body surface, lining cavities
endocrine glands
secrete cell products into interstitial fluid; lack ducts
exocrine glands
cells products secreted onto cell surface via a duct
muscle tissue
function: contraction
structure: striated actin/myosin bands, parallel, elongated cells, highly cellular and vascularized
connective tissue
function: connect, support, protect (bind, wrap, cushion, insulate)
structure: few cells (lots of space), ground substance, extracellular fibers
matrix
ground substance and extracellular fibers, dominates
ground substance
material between cells, interstitial fluid and cell producits. determines if ECF are fluid/gel/solid
extracellular fibers
provide support (collagen: strength, elastic: stretch/recoil, reticular: net of collagen fibers)
characteristics of connective tissue
origin in embryo, matrix dominates, properties determined by matrix, vascularization varies, 3 structural elements
function of neural tissue
communication and regulation
cancer
loss of a cell’s ability to be a tissue
- loss of anchorage
- cells migrate and divide
- loss of specialization
- immortal and divide infinitely (normal cells can only divide 20-30 times)
- result of an accumulation of gene errors
tissue cells
specialized, anchored, connected by junction proteins, highly regulated cell cycle, act as a unit
membranes
sheets of epithelial and connective tissues which form protective layers
functions of nervous system
1- sense: detect change
2- integration: process information, make decision, send command
3- responds: effector organs respond
CNS
control centre, brain and spinal cord
PNS
provides link to and from outside; afferent and efferent paths, receptors, nerves, ganglia
gray matter
group of cell bodies; nucleus/centre, cortex
white matter
axon collection (nerves, tracts, columns)
sensory/afferent pathway
PNS to CNS
motor/efferent pathway
CNS to PNS
nucleus/centre (nerve)
cell bodies with common functions
cortex
outer layer of gray matter
ganglion
clusters of cell bodies in PNS
protection of neural tissues
bones (vertebrae, skull), meninges, CSF, glial cells, cellular barriers (BBB)
meninges function
protective wrappings, carry nerves and blood vessels, form attachment sites, forms spaces holding fats and fluids
dura mater
tough outer layer of meninges
arachnoid mater
middle layer with extending fibers
pia mater
innermost layer adhering to nervous tissue
subarachnoid
holds CSF
epidural
stores fat in spinal cord
subdural
small amount of fluid adhering dura & arachnoid through surface tension
dural spaces
sinuses, hold veins in the brain
glial cells
support neuron and form cellular barriers
blood brain barrier
foot processes of astrocytes and blood vessel wall. 2 layers thick. filters nutrients and ions through.
CSF function
“sink”, maintains environment, cushions, brain floats in CSF, provides nutrients to cells in path of circulation.
CSF structure
formed in blood by chloroid plexus - 2 cell layer that filters and adjusts blood plasma
arachnoid villi
one way valves in SAS that return CNS to vlood via dural sinuses
circulation of CSF
1- choroid plexus
2- ventricles (lateral, third, fourth) SAS
3- arachnoid villi
4- dural sinuses
reflex
rapid, involuntary response
reflex characteristics
predictable, rapid, maintains homeostasis, involuntary, innate or learned
autonomic reflex
smooth muscles, cardiac muscles, glands
somatix reflex
skeletal muscles
somatix reflex
skeletal muscles
reflex arc
receptor, afferent path, control centre, efferent path, effector
