Nervous System, Flashcards
(28 cards)
Describe stage1 of action potential
Resting potential:
-the NaK pump actively transports 3 Na+ ions out and 2 K+ ions into the axon
-there are more Na+ ions outside the membrane which causes a negative gradient and a voltage of -70mv
Describe stage 2 of action potential
Depolarisation:
-Na channels open and Na+ ions diffuse into the axon
-the membrane becomes more +ve and has a voltage of +40mv
Describe stage 3 of action potential
Repolarisation
-Na Channels close and K channels open
-K+ ions diffuse out of the axon
-the membrane becomes more negative
Describe stage 4 of action potential
Hyperpolarisation/ refractory period
-the membrane voltage goes below resting potential
-this ensures only one action potential can be transmitted at any one time
Features of the endocrine system
-releases hormones secreted by endocrine glands
-they travel in the bloodstream to target cells
-responses are slow long lasting and widespread
What are two Local chemical mediators and what do they do
-Local chemical mediators are released by cells,has local effect and quick response
-Histamine is usually released in response to an injury or allergen during an inflammatory response
Prostaglandins are produced by most body cells, and respond to: inflammation, pain sensation and change in blood pressure
Draw nervous system nervous system
Nervous system —> central nervous system +peripheral nervous system
PNS —> voluntary nervous system +autonomic nervous system
ANS —> sympathetic and parasympathetic
what are peptide hormornes
-large polar molecules that cant pass through cell membrane
-has a specific tertiary structure which is complimentary to specific protein receptors
-activates enzyme activity in cells e.g insulin and glucagon
what are steriod hormornes
-they can rapidly pass through cell membrane as theyre lipid soluble e.g oestrogen
what is a reflex
-a rapid and autonomic response to a stimulus by transmission of electrical impulses along nuerones.
-they are fast short and localised
explain the process of a reflex
-stimulus is applied (change in environment)
-receptors detect stimulus
-impulses travel alomg the sensory neurone
-sensory neurone synapses with relay neurone
-relay neurone then synapses with motor neurone
-impulses travel along motor neurone
-impulse arrives at muscle or brain and they move to respond (contract/relax)
what are three factors that affect transmission speed of nerve impulses
-temperature ( inc temp = inc speed)
-axon diameter (inc diameter = inc speed)
-myelination (inc saltatory conduction = inc speed)
what is a synapse
a functional unit gap between two neurones
describe synaptic transmission process
-an action potential arrives at the synaptic knob
-which causes Ca2+ channels to open and Ca2+ ions diffuse into the synaptic knob
-this causes the vesicles containing Ach to fuse with the presynaptic membrane
-Ach is released and diffuses across the post synaptic membrane
-ACh binds to the Acg receptors on the post synaptic membrane
-this causes Na+ channels to open and Na+ ions diffuse in -which causes depolarisation (EPSP’s -excitatory post synaptic potentials)
describe the process of recycling acetylcholine
-acetylcholinerase breaks down acetylcholine into acetyl and choline
-acetyl and cholin are taken back into the pre-synaptic knob by active transport
-acetylcholine is resynthesised and packaged into vesicles
why is there mitrochondria in the synapse
during the process of recycling acetylcholine ATP is required. and mitrochondria provides ATP
What are the features of neurons
cell body: contains nucleus and other cell organelles
dendrons: conduct impulses towards cell body. theyre small and break into small branches at the ends (dendrites)
axons: conduct nerve impulses
myelin sheath: consists of mainly lipids and surrounds the axon. is formed from schwaan cells and provides electrical insulation
-node of ranvier: gaps in the myelin sheath along the axon
synaptic knobs: allows communication with other neurons or with effectors
what is summation and compare the two types
summation: addirive effect of several EPSPs causing depolarisation of the post synaptic membrane.
1.spatial summation (SS)
2.temporal summation (TS)
differences: in SS 2 presynaptic knobs synapse with 1 post synaptic knob. but in TS only 1 pre synaptic knob synapses with 1 post synapticc knob.
in SS impulses arrive from the 2 synaptic knobs at different places on the same neuron but on TS impulses arrive at the same place on the neurone one after the other.
simalarities: enough Ach is released and enough Na+ ions enters so threshold is passed for both.
the four types of effects of chemicals on synapses
-they can enhance transmission by binding to the receptors as they have similiar structure to normal transmitter and have the same effect. (e.g nicotine/ectasy/nerve gases)
-they can prevent transmission as they have the similiar structure but different effects as they fit into the receptors but dont allow normal transmitter from entering (curine)
-some can prevent the release of the transmitter from pre synaptic membrane so transmission is prevented (botox / tetanus toxins)
-some drugs inhibit the action of the enzyme, so transmission is enhanced
what are pacinian corpuscle
-they occur deep in the skin and are responsible for sensitivity to pain and pressure
-theyre found mostly in fingers, soles of feet, joints, ligments and tendons
explain the importance of reflex actions
-automatic/involuntary and fast
-prevents injury
-maintains homeostasis
explain how movements of potassium and sodium ions are involved in producing an action potential
-sodium ions diffuse in
-causing depolarisation
-potassium ions then diffuse out to start repolarisation
what is meant by the term ‘refractory period’
no new action potential/nerve impulse be produced in this time
the binding of GABA to receptors on postsynaptic membranes causes negatively charged chloride ions to enter postsynaptic neurones. explain how this will inhibit transmission of nerve impulses by post synaptic neurones
-inside becomes more negatively charged/hyperpolarised
-stimulation does not reach threshold level/ action potential not produced
-depolaristaion does not occur/ reduces effect of sodium ions entering
