Flashcards in 5.1 communication and homeostasis Deck (90)
How does a stimulus travel in the nervous system?
stimulus - receptors - central nervous system - effectors - response
what are sensory receptors and what do they do
convert energy of a stimulus (light or chemical energy) into electrical energy used to send nerve impulses
-act as transducers
describe the neurone when is at resting state
difference in charge across membrane, there is a voltage
also called potential difference
at rest resting potential
how is the difference in charge generated
by ion pump and ion channels
what does happen to the resting potential when the membrane is excited?
-membrane becomes more permeable
-more ions movement
-change in potential difference, GENERATOR PETENTIAL
what happens with a bigger generator potential?
-membrane more excited
-bigger ions movement
what happens when generator potential is big enough ?
triggers an action potential
what is a pacinian corpuscle
a mechanic receptor, detects mechanical stimuli (pressure and vibration)
structure of pacinian corpuscle
- contain end of sensory neurone, sensory nerve ending
-wrapped in layers of connective tissue; LAMELLAE
what happens when the pacinian corpuscle detects a stimulus?
-lamellae deform pressing on sensory nerve ending
-causing the deformation of stretch-mediated sodium channels (in neurone membrane)
-sodium channels open
-sodium ions diffuse into the cell
-generator potential is created
-if reaches the threshold potential it will trigger an action potential
three types of neurone
sensory, motor, relay
describe sensory neurone
-many short dendrites, one long dendron
-one short axon
-from receptor cells (cell body) to cns
describe motor neurone
- many short dendrites
-one long axon
-from cns (cell body) to effector cells
describe relay neurone
-many short dendrites
-many short axons
-from sensory neurones (cell body) to motor neurones
how is the membrane said to be when at rest
how much is the resting potential
how is the resting potential maintained
sodium potassium pump
potassium ion channel
how does the sodium potassium pump works
3 sodium ions are actively pumped out of the membrane which isn't permeable to sodium ions, they can't diffuse back in
-SODIUM ION ELECTROCHEMICAL GRADIENT is more positive inside
2 potassium ions are pumped in membrane which is permeable to potassium ion and they can diffuse out
how do potassium ion diffuse out of the membrane?
potassium ion channel
how is the charge of the membrane during resting potential
the outside of the membrane is positively charged compared to the inside
which are the 5 stages of an action potential?
5. resting state
what does a stimulus do to the neurones membrane
-sodium ions channels open
-membrane more permeable to sodium ions
-diffuse down sodium ion electrochemical gradient
-diffuse inside the neurone
-inside of the membrane becomes less negative
what happens during depolarisation
If potential difference reaches the threshold potential
voltage-gated sodium channels open
more sodium ions enter the cell, positive feedback
how much is the threshold potential
what happens during repolarisation
-when potential difference is around 33mV sodium channels close
-potassium channels open
-membrane becomes more permeable to potassium ions
-potassium ions diffuse out down the potassium ions concentration gradient
-membrane starts to enter in resting potential
what happens during hyperpolarisation
-potassium ions channels are slow to close
-for a bit too many potassium ions diffuse out
-potential difference is more negative than resting potential
what happens during the resting state
- membrane is at resting potential
what is the refractory period
when membrane can't be excited again yet because channels are recovering
when are the ions channel in refactory period?
sodium ions channels during repolarisation are closed
potassium ions channels are closed during hyperpolariasation
how does an action potential move along the neurone?
wave of depolarisation
-sodium ions enter and diffuse side ways
-causes sodium ions channel in next region to open
-moves away from parts in refractory
what does all-or-nothing mean?
-if threshold potential is reached action potential will always fire
-if not it won't
what does a bigger stimulus do to an action potentials
action potentials isn't bigger
will cause to fire action potentials more frequently
what are myelinated neurones, whats their structure?
-have a myelinated sheath made of Swann cells
-between Swann cells there are nodes of Ranvier (small gaps) where sodium ions channels are concentrated
how do action potential travel in myelinated neurones
-depolarisation only happens in nodes
-neurones cytoplasm conducts enough electrical charge to depolarise next node
-impulse 'jumps' from node to node - SALTATORY CONDUCTION
what are synapses
junctions between neurones or neurone and effector cells
what are synapses that use Ach called?
how is the gap called
how is the swelling at the end of presynaptic neurone called
how do cholinergic synapses work?
-action potential reaches ent of presynaptic neurone
-acetylcholine released in synaptic clef
-bind to cholinergic receptors
-trigger an action potential in postsynaptic neurone
what happens to neurotransmitters that remain in clef?
-go back in presynaptic neurone
-broken down by enzyme
how is acetylcholine removed from clef
an enzyme (acetylcholinesterase) it down
how do synapses work?
1. action potential arrives at the synaptic knob
-stimulates voltage gated calcium ion channels to open
-calcium ion diffuse in (pumped out afterwards - active transport)
2.influx of calcium ions move vesicle
-fuse with presynaptic membrane - exocytosis
-neurotransmitters in synaptic clef
3. bind to specific receptors in post synaptic membrane
-cause sodium ion channels to open
-sodium ions influx causes depolarisation
-action potential generated if threshold is reached
5. neurotransmitters removed from clef so that response doesn't keep happening.
how do synapses interact together
one neurone connects to many neurones
-info is dispersed in different parts of the body
many neurones connect to one
-information is amplified
what is summation?
combination of effect of neurotransmitters combined to reach the threshold potential.
how can summation be?
describe spatial summation
signals from different stimulus combined
describe temporal summation
2 or more impulses in quick succession from the same presynaptic neurone
-more neurotransmitters released in clef
-action potential is more likely to happen
how do synapses ensure that impulse travels in one direction
having receptors only in post synaptic membrane.
which are the components of the hormonal system?
endocrine glands and hormones
what are hormones
who are endocrine glands stimulated?
change in concentration of a substance
what happens what endocrine glands are stimulated?
hormones are secreted directly into the blood
and diffuse out all over the body, bind to specific receptors in target cells
they will give a response
what is hormone said to be and why
carries message from endocrine glands to receptors
what happens when an hormone binds to a receptor?
activates an enzyme in cell membrane that catalyses the production of a signalling molecule (inside cell)
(hormonal communication) what is the signalling molecule said to be?
(hormonal communication) what does the signalling molecule do
single mother parts to change how cell works
activates a cascade inside cell
adrenal gland, whats the first messenger
what does adrenaline do once released
binds to receptors and activates adenylyl cyclase (enzyme)
what does adenylyl cyclase do
catalyses the production of the second messenger
adrenal gland, what is the second messenger?
cyclic AMP from ATP
what does cyclic AMP do?
activate a cascade to break down glycogen into glucose, more energy
where are adrenal gland found?
structure of adrenal gland
2 parts, cortex and medulla
what does the cortex of adrenal gland secrete?
steroids hormones eg. cortisol / aldosterone
steroid hormones secreted by adrenal gland are a response to?
short term and long term stress
what is the body response to steroid hormones released by adrenal gland?
-stimulate the break down of proteins and fats, more glucose available
-increase blood volume and pressure by increasing the uptake of sodium ions and water by kidneys
-suppressing immune system
what does the medulla of adrenal gland secrete?
catecholamine hormones (adrenaline/ noradrenaline)
what does adrenaline cause in the body and how
make more energy in short-term
-increase heart and breathing rate
-cause break down of glycogen into glucose
-constricting some blood vessels, blood diverted into brain and muscles
what area of the pancreas contains endocrine tissue?
islets of Langerhans
where are islets of langerhans found?
around blood capillaries
where do islets of langerhans secrete the hormones
directly into the blood
what are the 2 type of cells is islets of langerhans &what do they secrete
alpha cells secrete glucagon
beta cells secrete insulin
disease where blood glucose concentration can't be controlled
describe type 1 diabetes
-auto-immune disease, body attack and destroys beta cells
-insuline isn't produced
-if blood glucose concentration increases it will stay high
-kidneys can't reabsorb all glucose, some is excreted in urine
-usually develops in children or young adults, links to family history
treatments for type 1 diabetes
monitor blood glucose concentration
describe insuline therapy
regular insulin injections during the day
or insuline pump, machine with a tube that releases insulin in body through a tube
describe islets transplantation
pancreas produces more insulin
how do we monitor blood glucose concentration
healthy and balanced diet
activity, regular exercise
describe type 2 diabetes
-beta cells don't produce enough insulin or insulin receptors don't work properly
-blood glucose concentration is higher than normal
-develops alter in life and is linked with obesity
-increased chances if African /asian/family history of disease
treatments for type 2 diabetes
life style changes
describe medication to treat type 2 diabetes
-metformin, acts on livers cells,
reduces the amount of glucose released
increase sensibility of cells to insulin, more glucose is taken up
-sulfonylureas stimulates production of insulin
-thiazolidinediones makes body cells more sensitive to insulin
where was insulin taken from for insulin therapy in the past?
where is insulin taken from for insulin therapy nowadays ?
made by genetically modified bacteria
what are the advantages of using genetically modified bacteria for insulin
larger quantities are produced
allergic responses or rejection are less likely
ethical religious reasons
what other therapy is being developed to treat diabetes
grown into beta cells
whats the normal blood glucose concentration?
90 mg per 100cm2
how does blood glucose concentration rises and fall
rises by eating carbohydrates
falls with exercise - more glucose used in respiration