Chapter 13,14&15 communication and homeostasis Flashcards
why do we need communication systems?
changing external environments
changing internal environments
co-ordinating different organs
how do changing external environments impact organisms
change places stress on the living organism
the environment change is a stimulus and the way the organism changes its behaviour or physiology is its response
abiotic - temperature
biotic - predator/prey interactions
why do we need a constant internal environment
all living things need to maintain a certain limited set of conditions inside cells to ensure optimum conditions for enzyme action
suitable temperature, pH, Aqueous environment, no toxins/ inhibitors
what are the features of a good communication system
whole body
cell communication
specific
rapid
short and long term
what are the two ways cells communicate with each other
neuronal - network of interconnecting neurones that produce rapid responses to changing stimuli
hormonal - uses the blood to transport hormones from endocrine glands to target organs. can be used to produce longer term responses
both systems utilise cell surface receptors, with specific shapes, to enable receipt of cell signals
define cell body
nucleus and large amounts of RER associated with production of proteins and neurotransmitter
what is the function dendrons (dendrites)
carry nerve impulses towards the cell body
define axon and its function
single long fibre that carries nerve impulses away from the cell body
define schwann cells
surround axon by wrapping around many times, protecting it and providing electrical insulation
phagocytosis and nerve regeneration
what is the function of the myelin sheath
forms covering of axon and made of membranes of the schwann cells.
rich in a lipid known as myelin
myelinated neurones transmit nerve impulses faster
define the “Nodes of Ranvier”
gaps between adjacent schwann cells where there is no myelin sheath. gaps 2-3um and occur every 1-3mm
what are the 3 types of neurone
sensory
relay
motor
what is the function and structure of sensory neurones
transmit impulses from a sensory receptor cell to a relay neurone, motor neurone or the brain.
They have one dendron, which carries the impulse to the cell body, and one axon which carries the impulse away from the cell body
sensory neurones are unipolar - one process coming off the cell body)
what is the function and structure of relay neurones
these neurones transmit impulses between neurones. E.g. between sensory neurones and motor neurones, they have many short axons and dendrons
what are the similarities and differences between motor and sensory neurones
similarities:
both have axon terminals
both have dendrites
both have cell bodies
differences:
s=unipolar, m=multipolar
s= has a dendron
s= connected to CNS/relay neurone, m=connected to motor end plate
motor’s axon is longer, s=shorter axon
what is the function and structure of motor neurones
neurones transmit impulses from a relay neurone or sensory neurone to an effector such as a muscle or a gland. they have one long axon and many short dendrites (multipolar)
what is the nervous response’s electrical impulse pathway
receptor -> sensory neurone -> relay neurone -> motor neurone -> effector cell
what is the function of the myelin sheath in myelinated neurones
electrical impulse “jumps” from one node to the next as it travels along the neurone. allows the impulse to be transmitted much faster
also the myelin sheath is made of lipoprotein (myelin) which means ions remain in the neurone - cannot diffuse out as not water soluble.
define ectotherm
an organism whose body temperature fluctuates with external temperatures
what are the advantages and disadvantages of ectotherms
advantages: use less food in respiration
need less food
greater energy proportion used for growth
disadvantages: less active in cooler temperatures
may not be capable of activity in winter months
define endotherms
organisms which use internal sources of heat to maintain body temperature.
many chemical reactions in the body are exergonic (release heat)
endotherms show behavioural and physiological adaptations
what are the physiological adaptations of endotherms to regulate temperature
too hot - secrete more sweat, panting, lie flat, vasodilation, reduce rate of metabolism
too cold - less sweat secreted, no panting, raised/ increased movement, vasoconstriction, increased rate of metabolism, spontaneous contractions/ shivering
what are endotherms’ behavioural adaptations to regulate temperature
too hot - move to shade, increased exposed surface area, remain inactive
too cold - move to sunlight, decreased exposed surface area, move to generate heat in muscles, roll into ball - decrease surface area
what are the advantages and disadvantages of endotherms
advantages - constant optimal body temperature
activity possible even when cold
inhabit colder parts of the planet
disadvantages - energy used up to maintain temperature
more food required
less energy used in growth
how do endotherms monitor the temperature of the blood
using the thermoregulatory centre in the hypothalamus of the brain
what are peripheral temperature receptors
receptors in the skin monitor the temperature in the extremities and feed information to the thermoregulatory centre
what are effector cells and what is their role in vasodilation/ constriction
smooth muscle in arterioles and pre-capillary sphincter muscles at the skin surface relax to dilate and contract to constrict
what is the purpose of increasing vessel diameter
increased blood flow to the skin and in turn the amount of heat lost by radiation to the air
how does sweating reduce body temperature
stimulated by motor neurones from hypothalamus
effector cells in sweat glands
as water has high latent heat of vaporisation, a significant amount of heat energy is lost
how do hairs and feathers regulate body temperature
too cold - erector muscles contract to raise hairs/ feathers
trapped air acts as an insulator reducing heat loss
too hot - erector muscles relax - hairs/ feathers lie flat
insulation reduced so more heat lost to air by radiation
how does metabolic activity change if temperature is too low
thyroid and adrenal glands release thyroxine and adrenaline to increase metabolic activity leading to more exogenic reactions and more heat released
involuntary muscle spasm (shivering) causing more respiration and therefore release more heat
what is the process of transmission of an action potential in UNmyelinated neurones
- Na+ ion diffuses into the neurone through a channel
- there is a localised high concentration of Na+ inside the neurone
- Na+ diffuses along the inside of the neurone
- Na+ gate, initially closed, opens due to depolarisation
- there is a series of ‘local circuits’ or ‘currents’
what is the process of transmission of action potential in myelinated neurones
- ionic changes can only occur at the “Nodes of Ranvier” as Na+ and K+ gated channels are found here
- Na+ and K+ ions cannot diffuse through myelin
- there are elongated total circuits/ currents
- action potential ‘jumps’ from one node to the next
- called saltatory conduction
what are the advantages of the myelin sheath in neurones
insulates
speeds up transmission
fewer channels needed (less protein, amino acid, ATP etc)
what effects the speed of an impulse in neurones
myelin sheath - increases speed
axon diameter - greater diameter= faster
temperature - higher temperature= faster speed
temperature also effects rate of diffusion of ions
what happens to an impulse in neurones of temperature is too high
channel denatures and impulse not transmitted
what is the synapse
the gap between the presynaptic and postsynaptic neurones
synaptic vesicles contain neurotransmitters to be transported across the synapse
what are the 5 examples of neurotransmitters
- Acetylcholine (ACh) - cholinergic synapse
- noradrenaline
- dopamine
- glutamic acid
- serotonin
what are the key features of synapses
synaptic cleft - gap which separates the axon of one neurone from the dendrite of the next (20-30nm across)
presynaptic neurone - neurone along which the impulse has arrived
postsynaptic neurone - neurone that receives the neurotransmitter
presynaptic knob - the swollen end of the presynaptic neurone - contains many mitochondria and ER to enable it to manufacture neurotransmitters
synaptic vesicles - vesicles containing neurotransmitters
neurotransmitter receptors - receptor molecules which the neurotransmitter binds with in the postsynaptic membrane
what are the types of neurotransmitter
excitatory - result in the depolarisation of the postsynaptic neurone. If the threshold is reached in the postsynaptic membrane an action potential is triggered. eg. acetylcholine
inhibitory - result in the hyperpolarisation of the postsynaptic membrane. preventing action potential from being triggered. eg. gamma-aminobutyric acid (GABA)
what are the 7 features of synapses
- several presynaptic neurones “converge” to one postsynaptic neurone
- one presynaptic neurone “diverges” into several postsynaptic neurones
- unidirectionality - message can only be sent from pre to post synaptic neurones
- filter out low level stimuli
- acclimatisation - background sounds or smells repeated stimulation results in “fatigued” synapse
- summation - pick up multiple stimuli for enough neurotransmitter to generate action potentials
(spatial or temporal) - inhibition - there are chloride ion channels on the postsynaptic membrane, if Cl- ions flood into the postsynaptic membrane, it can become hyperpolarised - unable to achieve an action potential
what are the two types of summation
spatial - different presynaptic neurones share the same synaptic cleft (convergent) - multiple neurones
temporal - a single presynaptic neurone releases many neurotransmitter over a short period of time (one neurone) - total amount exceeds the threshold value
state the:
stimulus
example of receptor
and example of sense organ
for a “mechanoreceptor”
stimulus = pressure and movement
receptor = Pacinian corpuscle
sense organ = skin
state the:
stimulus
example of receptor
and example of sense organ
for a “chemoreceptor”
stimulus = chemicals
receptor = olfactory receptor (detects smells)
sense organ = nose
state the:
stimulus
example of receptor
and example of sense organ
for a “thermoreceptor”
stimulus = heat
receptor = end-bulbs of Krause
sense organ = tongue
state the:
stimulus
example of receptor
and example of sense organ
for a “photoreceptor”
stimulus = light
receptor = cone cell (detects different light wavelengths)
sense organ = eye
what are the two features of sensory receptors
act as transducers - convert a stimulus into a nerve impulse
they are specific to a single type of stimulus
describe the basic structure of a Pacinian corpuscle
single nerve fibre surrounded by layers of connective tissue which are separated by viscous gel and contained by a capsule
stretch-medicated Na+ channels on plasma membrane
capillary runs along base layer of tissue
what stimulus does a Pacinian corpuscle respond to? and how?
pressure deforms membrane, causing “stretch-mediated Na+ ion channels” to open
if influx of Na+ raises membrane to threshold potential, a generator potential is produced.
action potential moves along sensory neurone
what are the 3 processes Schwann cells are involved in?
electrical insulation
phagocytosis
nerve regeneration
where are myelinated neurones found in the body
most in central and peripheral nervous systems
where are non-myelinated neurones found in the body
group C nerve fibres involved in transmitting secondary pain
name the stages in generating an action potential
- depolarisation
- repolarisation
- hyperpolarisation
- return to resting potential
explain the importance of the refractory period
no action potential generated
ensures unidirectional impulse
ensures discrete impulses
limits frequency of impulse transmission
larger stimuli have higher frequency
how do neurotransmitters pass across the synaptic cleft
simple diffusion
why is the pancreas both endocrine and exocrine?
exocrine - secretes digestive enzymes into pancreatic duct
endocrine - secretes hormones directly into blood (insulin and glucagon)
what is the islet of langerhans in the pancreas
cluster of beta and alpha cells that secrete hormones
what are acini in the pancreas
cluster of acinus cells surrounding a tubule in the centre
acinus cells secrete enzymes - exocrines
what do alpha cells do in the pancreas
manufacture and secrete glucagon
what do beta cells do in the pancreas
manufacture and secrete insulin
what is pancreatic juice made up of
amylase (type of carbohydrase)
trypsinogen (inactive protein)
lipase
define genesis
to make
define lysis
to break
define -neo
new
define glycogenolysis
the breakdown of glycogen into glucose
define glycogenesis
the formation of glycogen to glucose
how do beta cells manufacture insulin (8 steps)
- potassium and calcium ion channels on cell membrane
- K+ channels normally open so K+ diffuses out
- stimulus - causes blood glucose to rise, glucose diffuses into cell
- glucose metabolised into ATP
- ATP closes the K+ ion channels
- accumulation of K+ ions alters the potential difference - inside the cell is less negative
- change in P.D. causes voltage gated Ca+ channels to open
- Ca+ ions diffuse into cell and cause vesicles containing insulin to fuse with plasma membrane and insulin is released - exocytosis
what happens in the pancreas when blood glucose levels are raised
alpha cells decrease glucagon secretion
beta cells increase insulin secretion
target cells = Hepatocytes - liver cells
muscle cells
adipose (fat cells)
brain cells
action
1. more glucose channels on membrane
2. more glucose enters cell
3. glucose into glycogen (glycogenesis)
4. glucose converted into fats
5. more glucose used in respiration
blood glucose decreases
what is the non-steroid hormone mechanism
hydrophilic
the hormone is the FIRST MESSENGER
binds to receptors on the cell surface membrane (complimentary) - cannot pass directly through the cell membrane
G protein is activated - activates an enzyme ADENYL CYCLASE
adenal cyclase converts ATP to cAMP
cAMP = second messenger
cAMP acts directly on another protein, stimulate change and initiates a “cascade of enzyme controlled reactions”
what is the mechanism for steroid hormones
lipid soluble
pass through plasma membrane
bind to receptors in the cytoplasm or nucleus - forms hormone-receptor complex
complex acts as a transcription factor either facilitating or inhibiting the transcription of a specific gene
what are the 3 layers in adrenal glands - outer to inner
outer = capsule
middle = cortex
inner = medulla
what hormones are produced by the adrenal cortex and how?
- uses cholesterol to produce steroid hormones
ALSOSTERONE (mineralocorticoid) - controls Na+ and K+ levels via the kidney and impacts water retention and blood pressure
CORTISOL (glucocorticoid) controls metabolism in the liver decreasing the synthesis of glycogen from glucose
precursor molecules of the sex hormones also produced
what hormones are secreted by the adrenal Medulla and why
secretes adrenaline in response to stress - prepare body for “fight or flight”
how does adrenaline effect the body
relaxes smooth muscle in bronchioles - larger diameter for more air - O2 needed for respiration - more energy
increases stroke volume of the heart and heart rate- transports more O2 and glucose for more respiration
vasoconstriction (general) - increases blood pressure - restricts blood flow - sends blood to vital brain and muscles
stimulates breakdown of glycogen - more glucose more respiration
pupils dilate - more light enters eyes - increased vision
increased mental awareness - make faster decisions as more energy into the brain so more neurotransmitters firing action potentials
inhibits action of the gut - diverts blood away via vasoconstriction to more essential organs
what is the official name for diabetes
diabetes mellitus
what is the name for high blood glucose
hyperglycaemia
what is the name for low blood glucose
hypoglycaemia
what are the causes of type 1 diabetes mellitus
unable to produce insulin
may arise due to an autoimmune response - immune system destroys beta cells
usually developed during early childhood
what are the causes of type 2 diabetes mellitus
develops later in life
body stops responding to insulin or beta cells don’t produce enough
insulin resistance - receptors (glycoprotein) do not work
cells lose responsiveness to insulin therefore do not take up glucose, glucose left in the blood stream
“everyone will eventually get it as body deteriorates”
chances increased by:
excess body weight
physical inactivity
excessive overeating of refined carbohydrates
what is the treatment for type 1 diabetes mellitus
regular blood glucose monitoring - analysed by machine
insulin injections - increased glycogenesis
what is the treatments for type 2 diabetes mellitus
regulation of carbohydrate intake
exercise
weight loss
drugs - stimulate insulin production
insulin injections
what are the past, present and future sources for manufactured insulin
past: extracted from pancreas of animals eg. pigs
present: genetically engineered bacteria
future: stem cell therapies - promote embryonic stem cells to differentiate into beta cells
what are the advantages of using genetically engineered bacteria to produce insulin for injections
cost effective - higher quantities produced
removes ethical concerns over using animals or embryonic stem cells
pure form therefore less likely to produce allergic reactions/ rejection
what are the advantages and disadvantages of stem cell therapy for diabetes mellitus
advantages: donor availability wouldn’t be an issue
reduced likely-hood of rejection - less immune response
removal of need for patients to inject insulin
disadvantages: do not yet know how to control growth and differentiation - could cause tumours due to unlimited cell growth
embryonic stem cells - must destroy embryo - ethical obligations
what two hormones promote glycogenolysis
glucagon and adrenaline (during the fight or flight response)
where are the glands that secrete steroid hormones eg. Corticosteroids found?
in the cortex/ cortical region
describe the sequence of events leading up to the secretion of insulin by beta cells
- glucose respired (metabolized) to produce ATP.
- ATP closes potassium ion channels so K+ build up inside cell and cannot leave
- Voltage gated calcium ion channels open and calcium ions enter cell by diffusion
- More calcium ions result in movement of vesicles to membrane/ exocytosis - insulin leaves cell - is secreted
after an initial release of insulin, why does insulin secretion continue even when there is no further glucose intake?
- Because as long as blood glucose concentration remains higher than normal,
- sufficient ATP is still present and so K+ channels remain closed
- exocytosis still being triggered by calcium ions
describe two similarities in the action of plant and animal hormones in cell signalling
- hormone binds to receptor causing cascade of events/ enzyme reactions
- hormones only needed in small quantities/ concentrations to have an effect.
explain why plants are more able to form natural reproductive clones than animals
most plant cells retain ability to differentiate - totipotent
plants have meristematic tissue
plants can de-differentiate then differentiate into a different cell type
most animal cells are differentiated/ not totipotent or pluripotent - only able to differentiate into the same type of cell - multipotent
define saltatory conduction
where action potential jumps from one node of Ranvier to the next
