M5 C13: neuronal communiction Flashcards
what is an example of a change in the internal environment?
blood glucose conc
internal temperature
water potential
cell pH
what is an example of a change in the external environment?
humidity
external temperature
light intensity
how do animals respond to changes in the environment?
chemical responses (via hormones)
electrical responses (via neurones)
how do plant respond to changes in the environment?
chemical responses (via hormones)
why is coordination needed?
few body systems can work in isolation so organisms need to coordinate the function of different cells and systems to operate effectively
what is an example of coordination?
in order to contract muscle cells must respire and therefore need oxygen however they cannot get this oxygen themselves so rely on red blood cells. red blood cells rely on stem cells to replicate as they have no nucleus.
what is homeostasis?
maintaining a relatively constant internal environment
what is cell signalling?
one cell releasing a chemical that has an affect on another cell known as a target cell
what response transfers signals locally?
electrical response
between neurones at a synapse known as a neurotransmitter
what response transfers signals across large distances?
chemical response by using hormones
for example the pituitary gland secretes ADH which has an affect on the kidneys
how do plant respond to environmental changes?
by hormones (a chemical response)
what does the nervous system do?
detects changes known as stimuli and triggers an appropriate response
what does the motor neurone do?
transmit impulses from relay neurone or sensory neurone to an effector they have one long axon and many short dendrites. it also has a cell body and nucleus
what is the strucutre of the relay neurone?
has a cell body and a nucleus, with lots of axon and dendrons coming off of it. with axon terminals and dendrites
what does the sensory neurone do?
transmits impulses from receptor cell to a relay neurone, motor neurone or brain
what does the sensory neurone look like?
has a central cell body with axons going away towards axon terminals and dendron going towards it from dendrites
what are the gaps called between the myelin sheath?
node of ranvier
what is the myelin sheath?
schwann cells produce layers of plasma membrane around axons/ dendrons creating a myelin sheath to insulate neurone
what is saltatory conduction?
where signals jump from node to node
how does multiple sclerosis occur?
immune system sees schwann cells as foreign which triggers an immune response. this causes the myelin sheath to be destroyed making it longer for the impulse to travel.
what are sensory receptors?
they are located in sense organs. allows body to detect changes in the environment. they are specific to one type of stimulus and act as transducers.
what are transducers?
take stimulus and converts it into a generator potential. (electrical impulses)
what is the Pacinian corpuscle?
sensory receptors that detect pressure and touch
where is the pacinian corpuscle located?
deep within skin eg the end of fingertips, soles of feet
what is the resting membrane potential?
-70mv
how is the pacinian corpuscle depolarised?
an influx of positively charged sodium ions from outside the membrane through the stretch mediated sodium channels
how do the stretch mediated sodium channels open?
open due to pressure being applied near the receptors
what does the generator potential lead to?
action potential
how does the sodium- potassium pump work in the axon membrane?
it actively pumps sodium ions out of the axon and pottasium ions into the axon in the ratio 3:2. more positive on the outside
what does the sodium- potassium pump create?
the electrochemical gradient for sodium to diffuse into the axon and potassium back out
can potassium ions move back out after being pumped into the axon?
yes they can diffuse out through open potassium ions channels
can sodium ions move back in after being pumped out of the axon?
no because the sodium ion channels are closed
what does the excess of positive charge on the outside of the membrane create?
a negative charge so the resting potential of the membrane is -70mv
how is action potential created?
when the axon membrane is depolarised by the energy of the stimulus
what is the potential difference of the membrane after it has been depolarised?
+40mv
what happens after the impulse passes?
the membrane repolarises and and the charge goes from negative to positive. the neurone returns to rest
how is action potential propagated?
it starts at one end of the neurone and are propagated along the axon to the other end. depolarisation of one region acts as a stimulus for depolariastion of the next region
what does the energy of the stimulus trigger?
triggers some voltage gated channels to open. causing depolarisation as the charge changes
what does the change in charge from depolarisation cause?
more sodium ions to move as more channels are opened. this is an example of positive feedback
what happens at +40mv?
the voltage gated sodium ion channels close and the voltage gated potassium ion channels open
what happens after the voltage gated potassium ions open?
potassium ions diffuse out of the axon down the electrochemical gradient reducing the charge - repolarisation
how does hyperpolarisation occur?
lots of potassium ions diffuse out meaning the inside of the membrane is more negative at around -75mv
what happens after hyperpolarisation?
the volted potassium channels close and the axon returns to its resting state at -70mv
what is the refractory period?
a short period of time when the axon cant be excited as the voltage gated sodium channels are closed
why is the refractory period improtant?
so impulse only goes one way (unidirectional)
where can the action potential depolarise the neurone?
only at non- myelinated axon fibers, such as the nodes of Ranvier. this means only small amount of ATP is used as saltatory conduction is used
what speeds up action potential?
myelination
axon diameter- less resistance if axon is wider
temperature- apart from extreme temperatures denaturing the protein channels
what is the all or nothing principle?
threshold value must be reached to trigger a response. no matter the stimulus same action potential will be triggered
what will a stronger stimulus produce?
more impulses/ action potential fired
what is a synapse?
junction between 2 neurones
what do synapses do?
ensure impulses are unidirectional and allows impulses from one neurone to be transmitted ti many and vice versa
how do synapses work?
1- ap causes opening of volt gated ca+ channels to open
2- influx of ca+ down the electrochem gradient causes vesicles to fuse to the pre synaptic neurone
what happens after the vesicle fuse to the pre synaptic neurone?
neurotransmitters bind to the recepotrs by binding to the voltage gated sodium channels at the end of the receptors
what happens after the neurotransmitters bind to the receptor?
this opens the channel causing an influx of na+ ions down the electrochem gradient
what does the influx of the na+ ions do?
depolarisation which creates and action potential
what is acetylcholinesterase and what does it do?
an enzyme- work on na channels
binds to acetylcholine and breaks it down into acetyl and choline
what happens after acetyl and choline have been broken down?
they move back into the pre synaptic neurone by diffusion to be reused and there is a high conc of the in the synaptic cleft. it is binded back together by ATP
what is an excitatory neurotransmitter?
depolarises the post synaptic neurone if threshold is reached causing an action potential. eg acetylcholine
what is an inhibitory neurotransmitter?
hyperpolarization of the post synaptic neurone this prevents and action potential being triggered. eg GABA
what is spatial summation?
multiple synaptic neurones working together to reach threshold for action potential in post synaptic
what is temporal summation?
constant firing of neurotransmitters to reach a threshold
what is in the CNS?
brain, spinal cord, relay neurones
what is in the PNS?
pacinian corpuscle, motor neurone, sensory neurone
what are the 2 types of nervous system in the PNS?
somatic nervous system, autonomic nervous system
what is the somatic nervous system?
voluntary/ conscious control
what is the autonomic nervous system?
involuntary/ unconscious control
what are the 2 types of autonomic nervous system?
sympathetic- fight or flight, noradrenaline
parasympathetic- rest and digest, ach
what does the cerebrum control?
voluntary actions, is highly folded to increase activity, split into 2 hemispheres
contains all the lobes
what is the frontal lobe responsible for?
problem solving, memory, language, personality, judgement
what is the parietal lobe responsible for?
integrating sensory information/ input
what is the temporal lobe responsible for?
listening, perception, communication, emotion
what is the occipital lobe responsible for?
visual processing
what does the cerebellum do?
controls movement, posture and balance
COORDINATES movement
receives info from ears about balance
what is the medulla oblongata responsible for?
controls reflex activities such as heart rate and breathing. important in ANS controlling things like swallowing, coughing etc.
what does the hypothalamus do?
2 H’s- homeostasis and hormones
controls pituitary gland by triggering release of hormone in the endocrine system
what does the anterior pituitary gland do?
synthesizes and secretes hormones such as LH, FSH
what does the posterior pituitary gland do?
secretes hormones made in the hypothalamus such as oxytocin
what is a reflex action?
involuntary response to a sensory stimulus
why do we have reflexes?
avoid body being harmed, frees up mental capacity for more complex behaviours
what is the knee jerk reflex?
Doctors use a specialised hammer to hit a ligament between the knee cap and the tibia, and the leg of the patient will involuntarily straighten in a small kicking motion
what is the blinking reflex caused by?
caused by something travelling towards the eye at high speed, something contacting the cornea, or by drying of the cornea
how does the blinking reflex work?
Irritation or drying of the cornea sends impulses down the trigeminal sensory nerve to the medulla of the brain, where it connects with other neurones to transmit the signal to the effector muscles
what is skeletal muscle?
voluntary and striated
what is cardiac muscle?
involuntary
striated
myogenic (doesn’t need any other external electrical impulses)
doesn’t fatigue
what is smooth muscle?
involuntary
non striated
which muscle is multi-nucleated?
skeletal
what is the sarcolemma?
Plasma membrane enclosing muscle fibres
what is the sarcoplasm?
Shared cytoplasm within a muscle fibre.
what is t tubules?
Inward folds of the sarcolemma that help spread electrical impulses through the sarcoplasm.
what do the mitochondria do in muscle fibres?
Provide ATP needed for muscle contraction
what is the sarcoplasmic Reticulum?
Modified endoplasmic reticulum that contains calcium ions needed for muscle contraction.
what is the sacromere?
the functional region of the myofibril. When a muscle contracts, the sarcomere contracts.
where are myofivrils found?
in the muscle fibre
what is the thicker filament in myofibrils?
myosin
long rod shaped with bulbous heads projecting to one side
what is the thinner filament in myofibrils?
actin
2 strands twisted a round each other
what is the light band of the sarcomere?
(I band)
only actin present
what is the dark band of the sarcomere?
(A band)
both myosin and actin are present
what is the h zone in the sarcomere?
only myosin is present
where is the ‘z lines’ found in the sarcomere?
at the end of the light band
what is the main point of the sliding filament model?
in order to contract causing movement, actin and myosin filaments have to slide past each other
what is tropomyosin?
blocks the actin-myosin binding sites
what is troponin?
holds the tropomyosin in place
what is the sliding filament model?
An action potential causes calcium ions are released from the sarcoplasmic reticulum into the sarcoplasm by diffusion
these bind to troponin molecules, stimulating them to change shape
causing troponin and tropomyosin proteins to change position on the actin filaments
Myosin binding sites are now exposed on the actin molecules
The heads of the myosin molecules bind with these sites
The myosin heads bend and pull the actin filaments towards the centre of the sarcomere, causing the muscle to contract
When the myosin heads bend, it releases a molecule of ADP
ATP binds to the myosin head, allowing it to detach from actin
the energy released during this reaction allows the myosin head to return to its original position
The myosin head can now bind to a new binding site on the actin filaments this then repeats as long as troponin and tropomyosin are not blocking the myosin-binding sites and the muscle has a supply of ATP,
what is creatine phosphate?
a reserve supply of phosphate, which is available immediately to combine with ADP, reforming ATP.
this is used for short bursts of vigorous exercise, such as a tennis serve. When the muscle is relaxed, the creatine phosphate store is replenished using phosphate from ATP.
