14) Communication and Homeostasis Flashcards
Why do animals need to respond to their environment
Increase chance on survival
How does communications occur between adjacent and distant cells
-Cell signaling
In nervous system , secrete neurotransmiters
In hormonal system , secrete hormones
Define homeostasis
Maintaining internal body coditions within constant limits
Why is it vital maintaining homeostasis
To allow cells to function normaly and stop them being damaged
Why is it important to maintain
Temperature
Glucose
1) Temperature affects enzyne activity , and they control the rate of metabolic reactions
2)So there is enough available for respiration
What is negative feedback
Mechanism where the body restpres level to normaal
what is positive feedback?
Give eg.
Amplifies the change , increase the level away from the normal level
eg. Platelets
Why is positive feedback not involved in homeostasis
It doesn’t keep internal environment constant
What is the CNA
The brain and spinal chord
Process information and decides what to do about it
What is a transducer
Converts one form of energy into another
What is a potential difference
Where there is a difference in charge between inside and outside of the cell
What causes a change in potential difference>
Cell membrane becomes excited, more permeable
allow more ions in and out of cell
What is the change in potential difference called?
Generator potential
Describe how pacinian corpuscles work
Mechanoreceptors - detect pressure and vibrations
Found in skin , contain end of sensory neurone.
When is stimulated , lamellae is deformed and cause deformation of stretch-mediated sodium channel.
Sodium ions channel open and sodium ions diffuse into the cell , creating a generator potential .
WHen generator potential reach a limit, it triggers an action potential
Whaat is the structure of a sensory neurone
Short dendrites
one long dendron
receptor to cell body
short axon carfy impulse from cell body to cns
Describe the structure of the motor neurone
Many short dendrites
Impulse from CNA to cell body
1 long axon
Cell body to effector cell
Describe the structure of a relay neurone
Many short dendrites
carry nerve from sensory to cell body
1 axon carry impulse from cell body to motorneurone
What is a neurone’s resting state
the outside of membrane is postively charges than the inside
What is the value of resting potential
-70
what created and mantain restinig potential
SOdium-potassium pumps
potassium ion channels
what created and mantain restinig potential
SOdium-potassium pumps
potassium ion channels
What is the function of sodium potassium pumps
Move sodium ions out ,so they cannot diffuse back in.
Creates an electrochemical gradient
Move potassium ions into neurone . permeable to potassium so able to diffuse back out
What happens to the cell membrane when there is a stimulus
Excites neurone
sodium ions channel open
sodium ions diffuse in down electrochemical grad
Inside is less negative
What happens in cell membrane when depolarisation occur
when potential difference reach the threshhold (-55mv)
Voltage-gated sodium channels open
more sodium ions diffuse in
eg. of positive feedback
What happens in cell membrane when repolarisation occurs
Potential difference of +30mv
Sodium ions close
Voltage-gate potassium ions open
Permeable to potassium so ions move out
back to resting potential
What happens to cell membrane when hyperpolarisation occurs
Potassium ions close too slowly
becomes more negative than resting potential
what happens to cell membrane when at resting potential
sodium-potassium pump returns membrane to resting potention and maintain until membrane’s excited by another stimulus
Why cannot the cell membrane be excited again
ion channels are recovering and can’t be mmade to open .
Refractory period
Describe why and how action potentials go faster in myelinated neurones
Myelin sheath - electrical insulator
High number of sodium ion channels at Nodes of ranvier
Depolarisation occurs at the nodes of ranvier
Hence allows saltatory conduction and is fasr
non-mylenated => slower
What happens when an action potential triggers calcium influx
AP arrive at synaptic knob of presynaptic neurone
Stimulate calcium ion channels to open
Ca ions diffuse into synaptic knobe
What does the release of calcium ions cause
Cause synaptic vesicles to move into presynapti membrane
fuse to presynapticc membrane
release neurotransmitter into synaptic cleft by exocytosis
How does the neurotransmitter trigger an AP on post-synaptic neurone
Bind to specific receptors of post-synaptic membrane
cause sodium ions to open
influc of sodium ions cause depolarisation
neurotransmitter removed from synaptic cleft so response don’t keep happening
What is an excitatory synapse
neurotransmitter depolarise post-synaptic membrane make an AP
What is an inhibitory synapse
Neurotransmitter hyperpolarise post-synaptic membrane
preventing AP
What is a synaptic divergence
one neurone connect to many neurones
What is synaptic convergence
When many neurones connect to one neurone , info can be amplified
What is spatial summation
Many neurones release excitatory neurotransmiters to a single neurone.
What is temporal summation
2 or more impulses arrive right after eachother on the same neurne
How does hormones bind to receptors and trigger second messenger
Hormone binds to receptor and actives enzyme in cell membrane
Catalyses a signalling molecule ( known and secondary messenger )
activate cascare inside the cell
What happens when adrenaline acts as a first messenger
binds to cell membrane
activates adenylyl cyclase
cause production of secondary messenger - cAMP from ATP
What happens in the Adrenal cortex
Secrete steroid hormones
Cortisol + aldosterone
breakdown proteins + fats into glucose
Inc blood volume + pressure
supress immune system
what happens in the Adrenal Medulla
Protein hormones
**adrenaline + noradrenaline **
SHort term
inc heart/ breathing rate
glycogen-> glucose
Blood diverted to brain and musckes
What hormone do alpha cells secrete
(pink cells )
glucagon
What hormone do Beta cells screte
(purple cells)
insulin
Describe how Ectotherms control temperature
Control by changing their behaviour
Internal temp depends on external temp
Activity level depends on external temp
Variable metabolic rate generate little heat
Describe how Endotherms
Control by homeostasis
activity level independent when temp is wihtin limits
Constantly high metabolic rate so generate a lot of heat
Summarise Type 1 Diabetes
No insulin is produced
Auto-immune disease
Destroy Beta Cells
Kidneys are unable to reabsorb glucose
How can we treat Type 1 Diabetes
Insulin therapy
- REgular injections , insulin pump
-ISlet cell transplantation
-Diet , regular excersise
Summarise Type 2 Diabters
Beta cells don’t produce enough insulin or body cannot respond to insulin
Often linked to obesity
How can we treat type 2 diabetes
manage lifestyle changes
Medication
Insulin therapy
Why is using GM bacteria to produce insulin better?
CHeaper
Larger quantities can be made
Less likely to trigger an allergic response
