8 co-ordination in mammals Flashcards
what does the nervous system consist of?
the CNS, peripheral nerves and neurones
what are neurons?
cells that can carry rapid electrical impulses
what are Schwann cells?
cells that wrap around the axon
role of Schwann cells?
provide electrical insulation and protection
nerve regeneration
what is the myelin sheath made of?
Schwann cells (membranes)
role of the myelin sheath
electrical insulation
prevents generation of action potentials
faster transmissions
what are dendrites?
small extensions
role of dendrites
receives signals from neurones to cell body/area where signals are received
what are the nodes of ranvier?
gaps between the myelin sheaths
role of the nodes of ranvier
allow saltatory action(jumps between nodes)
role of axon
allows transmission across great distances
what is the soma?role?
contains nucleus and lots of RER- makes proteins and neurotransmitters
what neurone conducts nerve impulses from RECEPTORS to the CNS?
sensory neurons
what neurone conducts nerve impulses within the CNS?
relay
what neurone conducts nerve impulses from CNS to the effectors?
motor
what neurone has LONG dendrites and SHORT axons?
sensory
what neurone has SHORT dendrites and LONG axons? hint: MS.DLA
motor
what neurone has spider looking cell body?
relay
at rest what is the balance of K+ and Na+ ions INSIDE the membrane?
MORE K+ ions
less Na+ ions
value for resting potential?
-70 millivolts
high Na+ concentration can be maintained by a …./….. p…………. via ……………. …………….
Na+/K+ pump via active tranport
define neurotransmitter
hormone like substance released from pre-synaptic neurone and DIFFUSES ACROSS CLEFT to post-synaptic neurone
define synapse
junction between 2 neurones
what do synapses allow?
a single impulse to travel along a neurone to be transmitted to a number of different neurones
what is meant by cholinergic synapse?
uses ACETYLCHOLINE as its neurotransmitter
what is meant when a membrane is polarised?
there’s a difference in charge
order repolarisation, hyperpolarisation and depolarisation correctly
DE
RE
HYPE
what type of neurone is this?
sensory
what type of neurone is this?
motor
what type of neurone is this?
relay
what is the direction of an impulse along a motor neurone?
cell body -> AXON TERMINAL where the EFFECTOR cells are
what is the direction of an impulse along a sensory neurone?
receptor cells -> axon terminal -> CNS
what is the threshold for an AP to occur?
-55 mV
during hyperpolaristion (3) what ion channels are open?
NETHER K+ or Na+
define action potential.
when a stimulus triggers a rapid change in potential difference
reorganise: depolarisation, hyperpolarisation, stimulus, resting potential, repolarisation.
- stimulus
- depolarisation
- repolarisation
- hyperpolarisation
- resting potential
neurone cell membranes are _________ at rest.
polarised (difference in charge)
how is resting potential established.(5)
-sodium-potassium pump transports 3Na+ OUT 2K+ IN via active transport
-chemical gradient of 3Na+ and 2K+ cause diffusion
- K+ gates open but sodium gates shut, so K+ will diffuse out of cell DOWN conc. gradient
- this makes the overall charge inside more negative, creating an electrical gradient
- equilibrium is established
what does a voltage gated channel mean?
only open in dependency of cell membrane potential
what does a stimulus do?
excites cell and SODIUM ION CHANNELS OPEN
describe what happens for an AP to take place.(5)
- energy of stimulus causes sodium ion channels to OPEN, sodium diffuses into membrane = DEPOLARISATION
- change to electrical gradient to - 30 passes the threshold, allowing more Na+ channels to open causing a BURST OF DIFFUSION
- as cell membrane becomes less negative and now positive, pd of +40 mV is reached, Na+ channels CLOSE and POTASSIUM ION CHANNELS OPEN
- no electrical gradient so more K+ open and (leave high to low) more K+ outside = REPOLARISATION
- hyperpolarisation state reached when below -70 is reached so K+ close
- sodium-potassium pump will restore resting potential difference
what is the refractory period?
short period of time after an AP is generated, where the membrane CANNOT BE DEPOLARISED
what is the importance of the refractory period? 3
- ensures unidirectionality, forces AP down the axon
- AP are discrete (separate)
- limits how many can pass along axon at once
what is a synaptic vesicle?
membrane bound structures containing neurotransmitter substances
what is the synaptic cleft?
gap between 2 neurones
what do neurotransmitters do?trigger?
diffuse across cleft and bind to specific receptors, maybe triggering:
- AP
- muscle contraction in muscle cell
- hormone secretion from gland cell
how do synapses ensure unidirectionality?
receptors are only found on the POST-SYNAPTIC membrane
how do neurotransmitters transmit nerve impulses.(6)
- AP arrives at synaptic knob at end of neurone, AP stimulate Ca2+ channels to open, so INFLUX OF Ca2+ by diffusion
- influx causes the fusion of synaptic vesicle and presynaptic membrane
- vesicles release neurotransmitter into synaptic cleft- exocytosis
- neurotransmitter diffuses across cleft and BINDS TO SPECIFIC RECEPTORS on postsynaptic membrane
- this causes SODIUM ION CHANNELS TO OPEN
- INFLUX OF Na+ causes AP (if threshold is reached)
- neurotransmitter is removed by diffusing black so its doesn’t repeat
what is spatial summation?
many neurones share SAME cleft (one postsynaptic membrane) so all the neurotransmitter is enough to create an AP
what is temporal summation?
a single presynaptic neurone releases neurotransmitter many times over a short period of time, total will cause AP
what happens if an inhibitory neurotransmitter is released eg GABA?
- Cl- channels will open, causing an influx of negative chloride ions making the membrane more negative making it harder for an AP to be generated
- as the threshold is harder to reach
inhibitory or excitatory neurones will work ___________ at the same synapse. meaning?
- antagonistically
- summation will occur resulting in either overall inhibition or excitation
role of conjunctiva?
protects cornea
role of the cornea?
bends light
role of the lens ?
focuses light onto the retina
role of the iris ?
controls amount of light entering the eye
role of the sclera?
protective layer
role of the choroid?
a black layer preventing internal reflection of light
role of the retina?
contains light sensitive cells
role of the blind spot ?
lacks light sensitive cells, where the optic nerve leaves the eye
role of the fovea?
most sensitive part of the retina
role of the ciliary muscles?
controls the size of the pupil
role of the optic nerve ?
carries impulses
role of the vitreous humour?
jelly-like substance maintaining shape of eye
how do muscles in the iris respond to dim light.
radial muscles- contract
circular muscles- relax
overall = dilation
how do muscles in the iris respond to bright light.
radial muscles- relax
CIRCULAR muscles- CONTRACT
overall = CONSTRICTION
what are the two types of nervous system?
sympathetic and parasympathetic
features of a sympathetic nervous system. hint:F+F
- stimulates effectors speeding up activity
- heightened warrens to cope with stressful situations
features of a parasympathetic nervous system.
- rest and digest
- conserving energy
- controls activities under normal resting conditions
- INHIBITS EFFECTORS
the hormonal system is made up of ____ and ____ and sends information as ______ _______.
glands and hormones
CHEMICAL SIGNALS
rod cells contain a light-sensitive pigment called _______.
rhodopsin
organise these from outer to inner. choroid layer, retina and sclera
OUTSIDE EYE 1-sclera
2-choroid layer
-retina
what happens when light enters the eyed hits photoreceptors?
- light is absorbed by photo-sensitive pigments
- bleaching causes a chemical change
- triggers a nerve impulse along a bipolar neurone, which is connected to the optic nerve that will take impulses to the brain
rod cells allow _____ + ______ vision. cone cells allow _____.
- black and white
- COLOUR
how does light cause a change in voltage across the cell surface membrane?5
- light is absorbed by rhodopsin
- rhodopsin changes shape and breaks apart into retinAL and opsin
- opsin bind to the membrane causing sodium ion channels to CLOSE
- the pump will still pump 2 sodiums out for every three potassiums in via active transport but none can diffuse back into cell
- MORE sodium OUTSIDE- cell is hyperpolarised, very negative
- no inhibitory neurotransmitter released so bipolar neurone is not inhibited (depolarised) and doesn’t stop AP to reach brain via the optic nerve
what happens in rod cells when it’s dark?
- Na+ is pumped out using active transport and diffuse back as channels are open
- Inside membrane is slightly negative so depolarised
- triggers release of neurotransmitter
- neurotransmitter released will inhibit bipolar neurone so it cannot allow the AP to travel along optic nerve
