5.1.1&Chapter 13 neuronal communication Flashcards
What is homeostasis?
What is homestasis controlled by?
Hormonal and neuronal commnication
Nervous pathway
receptor- sensory neuron -CNS (relay neuron)- motor neurons- effect
Genenrla structures of the neurones
Dendron
Cell body
Axon
Myelin sheath
What is a dendron
sends impulses to cell body
What is a cell body
releases neurotransmitters
What is axon
long straight structure after cell body, sends impulses away from cell body
What is a myelin sheath
Layers of plasma membranes (lipids), actas as a insulation layer, speads up rate of nervous trasnmission
SENSORY NEURONE STRUCTURE
small cell body in the middle
What is a node of Ranvier
gaps between the myelin sheath
what part of the neuron can action potential happen
action potential can only happen in the node of Ranvier so it speeds up reaction quicker
MOTOR NEURONE STRUCTURE
large cell body at the start
REALY NEURONE
a lot smaller and cell body in the middle, branches on either side , dendrites receiving info from sensory neurone , axon giving information to the next
MYELIN SHEATH
-acts as a insulating layer
-speeds up nerve impulse transmission (saltatory conduction) at nodes of Ranvier
What cell produces myelin sheath
Schwann cell (purple)
Why don’t motor neurons have dendrons
What are neurotransmitters
What are sensory receptors
specific , 1 receptor = 1 stimulus
Types of sensory receptors
-chemoreceptor (chemicals EG: smell or taste)
-osmoreceptors
-mechanoreceptors (pressure and movement)
-thermoreceptors (on tongue and skin - temp)
-photoreceptors (lights Eg:retena )
Receptors act as transducers, What are transducers
turn stimulus to a electrical impulse, this is known as a generator potential , impulse is generated and initiated , now action potential can happen
What type of receptor is a pasilian corpuscle
mechanoreceptor
PC
sensory neuron ending inside , surface of sensory neuron we have stretch mediated sodium ion channels (sensitive towards any changes in their physical structure and only sodium can diffuse across)
resting potential
stretched mediated sodium ion Channels are closed
What is polarized?
More positive on the outside than the inside (NA+)
AFTER pressure on PC
when pressure applied, physically changing shape of PC, neuromembrane is naturally stretched, sodium channels are stretched open , NA+
diffuse into the neuron this depolarized the membrane and initiates a generator potential), when enough NA+ are in, it will trigger an action potential along the sensory neuron
Resting potential
Every single cell in our body has a polarized membrane (uneven distribution of ions in our cell membrane),
What is a resting potential
state at ehich the cell mebrane can be stimulated
What does the membrane do to matinaing a resting potential
What does the membrane do to maintaining a resting potential
1- sodium - potassium ion pump, carrier protein, requires energy , 3NAout and 2K in
2- Voltage gated sodium channel is closed
3- K+ channel is open (mainly non voltage)
4- Negative ions stay permanently with cell, this results in a generally negative charge inside cell hence the membrane is generally at a -70mV
active transport
Action potential
cell is being used
Parts to action potential
depolarization
- Before negative charge inside and constantly removal of + charge
-Receptors receive a single, sodium channels will detect that, get energy from the stimulus ,
once channels open, NA+ channels open and sodium come back in
increase of NA+ inside and reaches threshold potential -55, stimulate more voltage gated sodium channels to open, a lot more sodium come in
now we have a positive charge inside and a negative charged outside (+40Mv) - this is depolarization, sodium channels now close , voltage gated K+ channels open at +40mv
we can now regenrated the concnetartion of the ions across the mebrane
Now it has to repolarize for another signal coming in
What is hyperpolarization
potential difference is lower than resting potential (lower than -7mv)
Synapses
What is a synapse?
Junction between two neuron, transmit signal by neurotransmitters…. load of vesicles of neurotransmitters
Types of neurotransmitters
-Excitatory
-Inhibitory
Structures of a presynaptic neurone
pre synaptic neuron (where the impulse comes in)
they have voltage gated calcium ion(2+) channels
have vesicles that contain ACH
ACH first diffuses then
bind to receptors which causing the postsynaptic NA+ channels open, nA+ diffuse into the neuron
A new action potential now occurs on the post synaptic neuron
How does the ACH travel through the middle
diffusion across the gap
We do not ACH to stay stuck on the receptors, we dont want a contiuos relfux, sesiures , what do we do to stop?
We need to break ACH down, relies on a enzyme called AchE, one of the most efficient enzymes, fast reaction rate, broken down into do parts , choline and acetate, diffuse back to the pre synaptic where there are mitochondria, these mitochondria would do areboic repsiraion to relases ATP , ATP can combine A and C back to ACH
Roles of synapses
-Unidirectional transmission = nerve impulses is always one direction
-can cause multiple responses from one stimulus
-can receive multiple stimuli for one response
NEW 5.1.1
the need for communication systems in multicellular organisms:
responding to their enviornment
How do animals increase there chance of survival by responding to changes in their external environment?
by avoiding harmful environment places such as places that are too hot or too cold
How do animals increase there chance of survival by responding to changes in their internal environment?
to make sure that their conditions are always optimal for their metabolism
what is the definition of a stimulus?
Any change in the internal or external environment
How do plants increase their chance of survival by responding to changes in the environment?
1- They sense the direction of light and grow towards it to maximize light absorption
2- They can sense gravity so their roots and shoots grow in the right direction
3- Climbing plants have a sense of touch so they can find things to climb and reach the sunlight
What do receptors do?
detect stimuli
What do effectors do?
cells that produce a response to a stimulus
What are the 2 different types of receptors we can have?
1- some receptors are cells- that connect to the nervous system
2- some receptors are proteins- found in the cell membranes
Example of a receptor cell
Photoreceptors
Example of a receptor protein
glucose receptors
What communication happens to produce a response?
To produce a response, receptors need to communicate with effectors and effectors need to communicate with other cells
How does the communication between receptors and effectors happen?
via cell signaling
What does the communication between receptors and effectors make sure about organs?
Makes sure that the activities of different organs are coordinated to ensure that the organism is working effectively.
What are adjacent cells?
Nearby cells
What can cell signaling occur between?
between adjacent or between distant cells depending on the “system”
Example of signaling between adjacent cells
cells in the nervous system communicate by secreting chemicals called neurotransmitters which send signals to adjacent cells such as other nerve cells or muscle cells
Example of signaling between distant cells
The hormonal system works by cells releasing chemicals called hormones which travel in the blood and act as signals to distant cells
What do cell surface receptors do?
Allows cells to recognize the chemicals involved in cell signaling
What is negative feedback?
The mechanism that stores the level to normal is called a negative feedback mechanism
does homeostasis respond by negative feedback or positive and why?
Negative feedback because it restores levels in our body to normal level EG: water , glucose and temperature
What do homeostatic systems involve?
receptors, communication system and effectors
How does communication happen (the order)?
Receptors detect when a level is too high or too low, then the information is communicated via the nervous or hormonal system to effectors
What does an effectors response do?
It counteracts the change bringing levels back to normal
What limits does negative feedback have?
Negative feedback only works between certain limits , if the change is too big then the effectors may NOT be able to counteract the change
What does positive feedback do?
amplifies the change
What happens during positive feedback to do with the effectors?
The effectors respond to further increase the level away from the normal level
Is positive feedback involved in homeostasis and why?
Positive feedback is not involved in homeostasis because it doesn’t keep your internal environments constant
What can positive feedback be used for?
Useful to rapidly activate something EG: a blood clot after an injury
Ex
What are the 2 terms animals can be classed as depending on how they control their body temperature?
- Ectotherms
- Endotherms
What are examples of an ectotherm?
Reptiles and fish
What are examples of an endotherm?
Mammals and birds
What is one difference between ectotherms and endotherms in how they control their body temperature?
Ectotherms can not control their body temperature internally
Endotherms can control their body temperature internally
What is one similarity between ectotherms and endotherms in how they control their body temperature?
Ectotherms and endotherms can control their temperature by behavior Eg: by finding shade or reptiles can gain heat by basking in the sun
What does ectotherms internal temperature depend on?
Depends on the external temperature (their surroundings)
What does ectotherms activity level depend on?
The external temperature , they’re more active at high temperatures and less active at lower temperatures
What is ectotherms metabolic rate like and how does that effect how they generate heat and how much heat?
Have a variable metabolic rate and generate very little heat themselves
What does endotherms internal temperature depend on?
Their temperature is less affected by the external environment (within certain limits)
What does endotherms activity level depend on?
largely INDEPENDANT of the external temperature, they can be active at any temperature (within certain limits)
What is endotherms metabolic rate like and how does that effect how they generate heat and how much heat?
They have a constantly high metabolic rate and generate a lot of heat from metabolic reactions
What part of the brain is used to control body temperature in mammals?
Hypothalamus
mechanisms that mammals have to REDUCE body temp (body temp is too hot)
1- sweating
2- Hairs lie flat
3- vasodilation =
mechanisms that mammals have to INCREASE body temp (body temp is too cold)
1- Shivering
2- Hairs stand up
3- Vasoconstriction
4- Hormones
5- Much less sweat
How does the hypothalamus control body temperature?
Receives information about temperature from thermoreceptors (temperature receptors)
What are the two different types of thermoreceptors and what is the difference between the 2 and where can they be found ?
1- Thermoreceptors in the hypothalamus detect the internal temperature (temperature of the blood)
2- Thermoreceptors in the skin (called PERIPHERAL TEMPERATURE RECEPTORS) detect external temperature (temperature of the skin)
*PERIPHERAL meaning = located near a surface
What happens when thermoreceptors detect a stimulus?
Thermoreceptors send impulses along sensory neurons to the hypothalamus which sends impulses along motor neurons to effectors
