multicellularity, nervous system, sensory system Flashcards
reoccuring themes of physiology
1) homeostasis
2) form and function
3) overcoming the limits of diffusion
simple multicellularity
- adhesion molecules that cause adjacent cells to stick together (colonies)
-no major specialization of communication between cells - every cell in contact with external environment
complex multicellularity
- specialized cell functions
- communication between cells
- take in info from environment -> signal -> craft response
pros of multicellularity
- longer life span
- greater efficiency of specialized cells
- sexual reproduction leads to more genetic diversity
- bigger better fit for survival
multicellularity cons
- increased energetic costs
- have to do more than just diffusion for survival
- takes longer to reach reproductive maturity
- possibility for infections
surface area: volume ratio
the smaller the animal = larger the SA: V ratio
* smaller organism -> faster molecular diffusion rate
4 types of tissues
connective, epithelial, muscular, nervous
connective tissues
fat, bone, cartilage
epithelial tissues
connectivity/ diffusion tissues
ex. gut epithelial tissues in GI tract
muscular tissue
skeletal, smooth (ex. digestive muscles), cardiac
nervous tissues
specialized cells that conduct signaling
organ
a collection of tissues that structurally form a functional unit specialized to perform a particular function
mechanisms of substance transport
diffusion and bulk transport
pathway for systems based in homeostasis
- communication of info to all different specialized cells
- translate signals into actions
- distribution of nutrients, energy and oxygen to muscles
- removal of waste
- defense immune system
homeostasis neg feedback ex
feel cold -> signal to hypothalamus -> muscles shiver -> stop signals once at right temp
nervous system
network of neurons that receive, process and transmit information
group of neurons
nerve
ganglia
collection of nerves
cephalization
concentrating sensory organs and sensory neurons at front/anterior of the body; helps sense the environment
convergent evolution
evolved independently several times
ex. cephalization
nervous system 3 step mechanism; input and output
1) sense (sensory input)
2) integrate/ process
3) coordinate response (motor output)
central nervous system
brain and spinal cord; sending and receiving messages to various parts of the body.
peripheral nervous system
part of your nervous system that lies outside your brain and spinal cord; sends info from different areas of your body back to your brain and carries out commands from your brain to various parts of your body
3 types of neurons
1) sensory neurons
2) interneurons
3) motor neurons
sensory neurons
carries sensed impulses from the receptor to the CNS
*structure: cell body can be along axon
interneurons
enables communication between sensory or motor neurons and the central nervous system; in CNS
motor neurons
carries a signal from the central nervous system (CNS) to an effector cell, which then carries out the desired response
pre synaptic neuron
sends signal
post synaptic neuron
receives signal
signal transduction steps
1) stimuli received by dendrites + cell body
2) signal goes to axon hillock to determine if signal is strong enough to fire action potential
3) signal through axon terminal -> release neurotransmitter
4) neurotransmitter bonds to post synaptic cell membrane -> new signal
axon hillock
the region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons or the environment; is signal big enough to fire action potential?
relative charges of inside and outside of cell
inside: neg
outside: pos
is there more potassium inside or outside of the cell
inside
is there more sodium inside or outside of the cell
outside
are there more sodium or potassium channels
potassium
sodium potassium pump
moves Na+ out of the cell and K+ into the cell against the concentration gradient (active transport)
K+ equilibrium potential
-90 mV
Na+ equilibrium potential
+60 mV
resting membrane potential
the electrical potential difference across the plasma membrane when the cell is in a non-excited state.; -70 mV
what dictates the resting membrane potential of a neuron
equilibrium potential
what is used to maintain resting membrane potenial
sodium potassium pump
action potential
the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell
action potential steps
1) threshold
2) depolarization
3) repolarization
4) refractory
action potential; threshold
positive ions come into cell increasing its voltage (more pos)
action potential; depolarization
large amounts of Na+ come into the cell; large increase in + V
action potential; repolarization
large amounts of K rush out of the cell through open pore decreasing cell voltage
*once potential gets to around +40
action potential; refractory
membrane potential drops below the resting membrane potential; have to build potential back up
how are the K+ and Na+ pores opened and closed
inactivation gates
Saltatory propagation
electrical impulses along axons is highly accelerated by the myelin sheath and produces saltating or “jumping” action potentials
node of ranvier
a gap in the myelin sheath of a nerve that allow the generation of a fast electrical impulse along the axon.
synapse
end of axon terminal where chemical signals released
presynaptic membrane
end of neuron that is sending the signal; has Ca2+ channel that is opened by depolarization, Ca2+ released moves vesicles to exocytosis with membrane
where are neurotransmitters released
synaptic cleft
how are signals recived
postsynaptic membrane has ligand/ signal receptors that take neurotransmitters from synaptic cleft
glial cells functions
- wrap axon in myelin sheath
-maintain the blood brain barrier
-structure/ stabilize neurons
-maintain homeostasis of interstitial fluid
-maintain ion conc
-release lactate for energy
how do signals flow down axons
bounce/jump from node (protein region)-> to node (no myelin sheath)
Astrocytes
type of glial cell (70% of CNS); functions
-maintain the blood brain barrier
-structure/ stabilize neurons
-maintain homeostasis of interstitial fluid
-maintain ion conc
-release lactate for energy
-clear neurotransmitters from synapse
how many kinds of neurotransmitters do most neurons release
only 1
how many kinds of neurotransmitters do most neurons accept at dendrites
many!
how many other neurons does 1 neuron synapse with
hundreds
ESPS
Excitatory postsynaptic potential;
2 types : non summation and temporal summation
non summation esps
increase in potential (excitatory) BUT not enough to set off action potential (not up to threshold)
temporal summation esps
potential sums up to threshold potential -> sets off action potenial
ISPS
Inhibitory postsynaptic potential; membrane potential goes below resting potential.
central nervous system
brain and spinal cord
peripheral nervous system
part of your ns that is not brain and spinal cord; somatic and autonomic
somatic nervous system
subcategory of PNS; controls voluntary, consciously controlled movement
ex. sensing the environment (sensory neurons) and controlled movement (motor neurons)
autonomic nervous system
subcategory of PNS; controls involuntary, unconsciously controlled movement
2 subcategories; sympathetic and parasympathetic
sympathetic nervous system
division of PNS autonomic NS; fight or flight response (increased heart rate, dilated pupils, inhibits intestinal system to focus on survival)
parasympathetic nervous system
division of PNS autonomic NS: rest and digest response (slows heart, stimulates intestinal systems/ digestion, constricts pupils)
thermo-sensitive sensory cells
constantly monitor temp and fire action potentials
- too cold -> signal muscles to shiver
- to hot -> signal for heat loss through sweat
*homeostasis
muscle contraction mechanism
- controlled by muscle neurons
- acetylcholine binds to muscle membrane receptors -> depolarization of muscle cell -> contraction
motor end plate
The specialized postsynaptic region of a muscle cell
afferent nerve
bring sensory information to CNS
efferent nerve
transfer info from CNS
sensory receptors
special proteins in sensory cells embedded in sensory organs that detect changes in our environment
sensory transduction
signal from environment taken in and processed (3 main types of receptors)
chemoreceptors
molecule in environment is specific to certain receptor; indirectly opens ion channel to depolarize cell
photoreceptors
signal into cell, ion channels close, cell is hyperpolarized
* how our eyes perceive light
mechanoreceptors
how we perceive tactile information; pressure deforms cuticle, physical change in the ion channel, channels open and cell is depolarized
what do mechanoreceptors detect
detect touch, pressure, vibration and tension
mechanoreceptor reactivity
*highly sensitive; low threshold of activation
*highly myelinated -> fast signal
action potential firing rate
depends on the strength of the signal
action potential firing rate; continuous stimuli
same high firing rate but less frequent as stimuli prolonges
lateral inhibition
enhances edge and boarder detection of signal by reducing extiment of adjacent interneurons
olfactory sensory neurons
neurons in nose that sense odors that bind to receptors on chemosensitive hairs
chemosensitive hairs
pick up signals from olfactory sensory neurons -> signal transduction pathway -> amplification
what do interneurons do for smell pathway
integrate info from olfactory receptor before sending info to brain
sense of smell and nose size
bigger nose -> more chemosensitive hairs (greater SA) -> better sense of smell
ex. chihuahua vs bloodhound
*evolution and genetics
how are sweet, savory and bitter flavors received
g protein coupled receptors
how are salty flavors received
Na+ depolarizes cell -> opens Ca2+ channel
how are sour flavors received
H+ ion channels depolarizes cell AND inhibits K+ channels
oral referral
causes you to perceive whats going on in the nose as if it is inside the mouth
what flavors detected by nose
menthol (mint), carbonation, spice/hot
stereocilia
hair-like protrusions on the surface of sensory cells that serve as mechanoreceptors; motion and gravity
statocyst
a small organ of balance and orientation in some aquatic animals that contain statolith; help perceive current direction
statolith
particle in statocysts that stimulates sensory receptors in response to gravity, so enabling balance and orientation
mechanoreceptor hair cell
Hair cells in the inner ear that detect sound and head movement.
support cell
mediators of hair cell development, function, death
vestibular system
functions to detect the position and movement of our head in space; moves faster than eyes
semicircular canal
fluid movements through semicircular canals cause disruption to sensory cells -> open ion channels -> signal transduction
* in inner ear
outer ear
collects sound waves and channels them into the ear canal;
auditory canal (pinna -> auditory canal -> eardrum)
middle ear
connects the sound waves from the external environment and transfers them to the inner ear for auditory transduction.
inner ear
transform the vibrations into electrical impulses that then travel along the eighth cranial nerve (auditory nerve) to the brain
malleus, incus, and stapes
3 bones in middle ear
Vestibulocochlear Nerve; 2 branches
- vestibular branch: balance and spatial sensation
-cochlear branch: special sensation of hearing
Cochlea
receiving and analyzing the sounds which are interpreted by hair cells or stereocilia.
entrance to cochlea
oval window and round window
eardrum
vibrates when sound hits it at same frequency of sound wave -> initiates hearing
3 step mechanism for hearing
1) sound wave directed into auditory canal by pinna
2)sound hits eardrum at same frequency as sound wave -> passed on
3) sound -> mechanical force -> fluid waves (inside cochlea)
hair cell activation in inner ear
disturbed by fluid wave -> open ion channels -> k+ flows into the cell -> depolarization and signal transduction
*once pathway is activated fluid wave goes opposite direction to depolarize cell
basilar membrane
membrane in cochlea that supports hair cells, serves as the base layer of the organ of Corti, and propagates sound vibrations that allow the brain to interpret sound
tectorial membrane
membrane above the hair cells; stimulates movement of hair cells
organ of Corti
transduction of auditory signals; mechanoreceptor hairs anchored at organ of corti
retinal
compound bound to the protein opsin; when light hits cis-retinal -> trans-retinal -> activation of protien
opsin
photoreceptor protein; signaling state regulated by activation of retinal -> G protein pathway cascade
fovea
part of retina that sharpens visions; (most cones in fovea)
retina
layer of photoreceptors and glial cells that capture the light that enters your eye and helps translate it into images
lens
focuses light for the retina
cornea
transparent shield
ciliary muscle
muscle in eye that allows you to focus; changes the shape of the lens when your eyes focus on a near object
iris
colored part of eye; adjusts the size of the pupil to control the amount of light that enters the eye.
optic nerve
nerves at back of eyes that relay visual info the the brain
rod and cone functions
rods: cells that allow us to see things in dim lighting
cones: help see color (red, blue, green or combo of both; dependent on nm of wavelength)
phototransduction cascade
G protein coupled pathway activated by opsin conformational change (retinal) -> cGMP PDE -> Na+ channels close -> HYPERPOLARIZATION
PDE function
closes Na+ channels to hyperpolarize the cell; at rest cGMP keeps channels open
bipolar cell
retinal interneurons; photoreceptor cells (rods and cones) -> ganglion cells
ganglion cell
neurons that connect the retinal input to the visual processing centres within the central nervous system.
horizontal cell
sharpen image; lateral inhabiton
amacrine cell
adjust motion and brightness; lateral inhibition
