stimulus + response Flashcards
stimulus
change in internal or external environment
receptor
a specific cell which detects change
coordinator
normally CNS - can also be a gland/organ - processes information from receptors
effector
usually muscle or gland - br
taxis
move towards or away from a stimulus (directional stimuli, directional movement)
kinesis
keeping moving in unfavourable conditions to remove itself from such conditions - non directional stimuli
myogenic
contracts without stimulation from brain
autonomic nervous system
controls involuntary responses
somatic nervous system
controls voluntary movements
peripheral nervous system made of
motor neurone
sensory neurone
2 divisions of autonomic nervous system
sympathetic
parasympathetic
how is heart rate controlled whilst exercising
- increase CO2 decreases pH of blood as it forms carbonic acid
- chemoreceptors in aorta detect drop in pH
- send impulse to medulla oblongata via sensory neurone
- frequency of impulses sent to SAN via sympathetic nervous system increase
- heart rate increases
dendron
part of nerve cell leading towards cell body
axon
part of nerve cell leading away from cell body
Schwann cells - function
- how does it carry out function
insulation, making impulses faster
as contains lots of lipid myelin, as it grows its wraps cell membrane around nerve cell
gap between Schwann cells
node of ranvier
how is a resting potential in a neurone established?
- sodium potassium ion pump pumps 3 sodium ions out of the cell for every 2 potassium ions it pumps in
- using energy from hydrolysis of ATP to ADP + Pi
- as sodium ion channels are closed, a resting potential is created
resting potential value
-70mv
refractory period
period after an action potential where no other action potentials can occur
How is action potential established/reached
- Na+ ions diffuse rapidly into cell through open voltage gates sodium channels
- if value is above threshold value, rapid depolarisation of the axon will occur as all the voltage gated sodium ion channels open
How Is resting potential established after an action potential?
- Na+ voltage gated channels close, reducing membrane permeability to Na+
- K+ channels open, allowing H+ ions to renter cell
- depolarising the membrane
- allowing repolarisation of the axon
- leading to hyper polarisation until Na+K+ pump resets resting potential
period where membrane potential is lower then resting potential
hyperpolarisation
d. resting membrane potential
difference in charge between interior and exterior of cell
action potential
moving depolarisation along the cell
reason action potential occurs (2)
- all Na+ channels closed
- resting potential not yet established
function of refractory period (2)
- ensures impulses travel in ONE direction along the axon
- produces discrete and separate action potentials - allows frequency to be detected
difference between myelinated cells and non-myelinated cells
- myelinated cells: action potentials jump from node of to node - meaning depolarisation only occurs at nodes of ranvier - via SALTATORY CONDUCTION - and not all the way along the cell = faster impulse
- sodium ion channels concentrated at nodes
pressure sensory =
Pacinian corpuscle
how are action potentials in Pacinian corpuscle initiated
- same but membrane of neurone is stretched, causing Na+ channels to open
3 factors affecting speed of conduction of action potentials
- myelination -
- axon diameter - less resistance to ion flow = depolarisation reaches other parts of the cell faster
- temp - as ions diffuse faster - past 40 degrees proteins denature
pressure sensing receptors
baroreceptors
where are….
- baroreceptors
- chemoreceptors
found?
- artery walls - carotid artery wall
- wall of aorta, wall of carotid artery
describe the process of a action potential being transmitted across a synapse
- AP arrives at pre-synaptic terminal
- causing voltage gated calcium ion channels to open
- diffusion of Ca2+ into neurone
- Ca2+ causes vesicles containing neurotransmitter (acetylcholine) to fuse with pre-synaptic membrane
- acetylcholine released into synaptic cleft
- diffuses across synaptic cleft
- binds to complimentary neuroreceptor
- if threshold value reached = rapid depolarisation of post synaptic neurone
- acetylcholine-esterase released into synaptic cleft
- hydrolysis of Ash into acetyl and choline (preventing continual depolarisation of axon)
- products diffuse back across the cleft and into knob
- hydrolysis of ATP provides energy for recombination of acetyl and choline -> acetylcholine
- back into vesicles ready for another AP
2 ways of reaching an AP
- spatial summation
- temporal summation
spacial summation
multiple synapses stimulated - combined effect of both APs
temporal summation
high frequency AP = high amounts of neurotransmitter - frequency of APs is determining factors
inhibitory synapses
ones which make it less likely for an AP to occur in the post synaptic neurone
how does an inhibitory synapse work
- presynaptic neurone released neurotransmitter that binds to chloride ion protein channels on post synaptic membrane
- causing them to open
- Cl- move into post synaptic membrane by facilitated diffusion
- binding of transmitter caused opening of nearby K+ protein channels
- K+ out of post synaptic neurone into synapse
∴ potential difference is more negative
∴ hyperpolarisation - less likely a new AP produced as more Na+ needed to meet threshold value
function of choroid layer of eye
stops light bouncing around - absorbs
resting potential value
70mv
features of RODS (3)
- cant distinguish between wavelengths of light - vision in low light intensities in B&W
- more numerous then cones
- multiple joined to a single bipolar neurone
- therefore achieve generator potential by RETINAL CONVERGENCE - SUMMATION increases change of threshold value being reached
how is a generator potential reached?
pigment is broken down by certain wavelengths of light
why is there low visual acuity with rods
- multiple joined to one bipolar cell (one sensory neurone) brain received one message for many rods stimulated - cut distinguish between 2 discrete items due to retinal convergence
features of CONES (2)
- each cone joined to its own bipolar neurone
- high visual acuity as each cone is connected to a single bipolar neurone therefore brain received separate impulses as no summation and can distinguish between 2 discrete items
greater conc of cones at…
fovea
