Nervous Coordination- Paper 2 Flashcards
What are the three things that the nervous system involves
- Detection of stimuli by receptors
- Transmission of nerve impulses by neurones
- Response by effectors
Provide a definition for what the nervous system entails
It provides a rapid response to stimuli and involves the transmission of electrical impulses along neurones, and chemical transmission across synapses between the neurones
What are the two major divisions of the nervous system
Central nervous system- the brain and spinal chord
Peripheral nervous system- nerves that originate from brain and spinal chord
What other two systems can the nervous system be divided into in terms of response
Voluntary nervous system, under voluntary conscious control and includes muscular and skeletal system
Autonomic nervous system which is involuntary or subconscious
What are the two parts of the autonomic system
Sympathetic- fight or flight, speeds up heart rate or blood pressure
Parasympathetic- slows down heart rate or blood pressure
What is a neurone and list the three different types
Specialised cells that are adapted to their function which is to carry electrical impulses from one part of the body to the next
Sensory, ralay and motor neurone
explain what a dendrite is
many thin extensions that carry impulses towards the cell body- receive impulses towards the cell body- receive impulses from other nerve cells
explain what a cell body is
groups of ribosomes which form neurotransmitters (proteins that transmit signals across from one neurone to the next)
explain what an axon is
very long extension from the cell body that transmits impulses away from the cell body to the axon endings
explain what the myelin sheath is
formed by the folding of shwann cells- protects axon and provides electrical insulation
explain what a schwann cell is
associated with an axon and is a specialised cell
peripheral neurones are surrounded and supported by Schwann cells in vertebrate. neurones are myelinated- they grow around the axon of the nerve cells to form a multi-layered myelin sheath
forms the myelin sheath which insulates the axon- increases the speed of electrical impulses along the axon
explain what a terminal branch is
ending of axons divide into branches which form synapses with other neurones
explain what a node of ranvier is
gaps between myelination of axons. intervals along the myelin sheath which are important for speeding up the nerve impulse transmission
what is resting potential
- electrical impulse
nerve cells are able to transmit an electrical impulse because there is a difference in electrical potential across the membrane, something which can be measured using a voltmeter
At rest the potential difference in -70mV across the axon membrane
the membrane is polarised as it is maintaining a potential difference between two different sides
when the axon is at rest the difference in voltage is referred to as a resting potential
how is a resting potential established
There is a higher concentration of sodium on the outside of the neurone
there is a higher concentration of potassium on the inside of the neurone
the difference maintained by many Na+/K+ pumps that moves 3Na+ out of the cell and 2K+ in to the cell requires energy released by ATP
There are also voltage gated channel proteins for both K+ ions and Na+ ions embedded within the axon membrane
in a resting neurone the Na+ voltage gated channel proteins are closed
Na+ ions pumped out of the cell cannot diffuse back in by FD
some of the K+ ion channel proteins are open as the membrane is more permeable to K+ ions
some of the K+ ions can diffuse back out
more positive ions on the outside of the membrane than inside the neurone so the inside is slightly negative compared to the outside
how is a nerve impulse transmitted
the resting potential is maintained until the membrane is disturbed or stimulated
an action potential happens when the membrane reaches threshold and becomes depolarised
an action potential is the reversal of resting potential
the membrane potential goes from -70mV to 40mV in a short period of time
explain the process of depolarisation
the stimulus causes the membrane to become more permeable to Na+ ions
if the membrane potential reaches threshold, all the voltage gated Na+ channel proteins open
because there is a higher concentration of Na+ ions outside the cell, the Na+ diffuse rapidly into the cell
the higher concentration of positive Na+ ions inside the cell now reverses the resting potential and causes the inside to become positive in relation to the outside. this process is called depolarisation
the K+ voltage gated proteins remain closed
the high concentration of positive ions inside the cell is the action potential
explain repolarisation
once the internal potential difference reaches +40mV the Na+ voltage gated channel proteins close and the K+ ion voltage gated channel proteins open
there are more K+ on the inside of the axon than the outside of the axon membrane and therefore the K+ ions diffuse out of the cell down a concentration gradient
explain hyperpolarisation
the K+ ion channel proteins remain open longer than needed to reach resting potential, making the inside of the cell even more negative at -90mV. this process is called hyperpolarisation
the sodium potassium pump restores the resting potential back to -70mV
explain the all or nothing response
an action potential will only occur when the membrane is stimulated so that all the local Na+ voltage-gated channel proteins open
the minimum intensity of stimulus is called the threshold
sub threshold no action potential will occur
above the threshold a full size action potential is given regardless of the increase in the size of the stimulus
explain what a refractory period is
after transmitting an electrical impulse an exon has to recover before it can transmit another impulse
a period of inactivation following the transmission of an impulse is the refractory period
another action potential cannot be formed at that point until the period is over
define refractory period
the time taken to restore the resting potential
explain the impulse transmission along the axon
the nerve impulse is the movement of an action potential along the neurone. action potential act as a stimulus to ajacent polarised areas of the membrane and this causes the action potential to be passed along
explain how the myelin sheath and saltatory conduction lead to conduction of impulses
the impulse travels by jumping from one node of ranvier to the next node of ranvier - this is known as saltatory conduction
it occurs because the myelin sheath provides electrical insulation along the axon and depolarisation can only occur at the nodes of ranvier
the electrical impulse depolarise the next node and the impulse is passed along by jumping from node to node
this increases the rate of transmission as depolarisation only occurs at the nodes/ less of the axon membrane needs to be depolarised
