Nervous system Flashcards
nervous system 2 division
- Central nervous system
- Peripheral nervous system
PNS division
Afferent division
- to bring to
- sensory info to the CNS
Efferent division
- to bring out
- motor commands from the CNS
- Somatic nervous
- Autonomic nervous system (ANS)
system
CNS to PNS to motor efferent divison to somatic nervous system or Autonomic nervous system (no control over) to sympathetic division or parasympathetic division
neuroglia
support, connect, protect neurons
How do neurons communicate with each other?
through synpases
- A junction that allows information to transfer from one cell to another
what does synapses occur between?
- Two neurons- presynaptic neuron and postsynaptic
- A neuron and ‘effector cell’ (which carries out an action)
e.g. Neuron to muscle (the neuromuscular junction)
What are two types of synapses and which one is rear
- Electrical synapses (rare)
- Chemical synapses
Neurotransmitters and examples
- Vary from synapses
- same neurotransmitter is always released at a particular synapses
- Acetylcholine
- noradrenaline
- Adrenaline
post-synaptic potentials meaning and two types
- Binding of neurotransmitter to a post-synaptic receptor will cause graded potentials, which can either be
- EPSP: excitatory postsynaptic potentials- depolarising
- IPSP: inhibitory postsynaptic potentials- hyper polarising
Excitatory post-synaptic potentials (EPSP)
- Causes depolarisation
- cation channels open, which allow movement of both Na+ and K+
- some k+ moves out of the cell, but more Na+ moves into the cells causing depolarisation - Brings the membrane close to threshold
Inhibitory post-synaptic potentials (IPSP)
- causes hyperpolarisation
- Opening of channels causes either k+ to leave or Cl- to enter
- membrane moves further away from threshold
summation by the post-synaptic neuron and two types
- 1 post synaptic neuron can receive input from 1000’s of neurons
- summation takes in all information and decides what to do
- Summation is the addition of all EPSP and OPSP that a neuron receives
=> Determines whether an action potential will occur or not - two types of summation
=> temporal- one causing multiple close in time
=> spatial- two or more presynaptic
no summation
An EPSP only lasts a few ms. if EPSPs are too far apart in time, they wont add together
Temporal summation
A presynaptic neuron has action potentials in close succession
- First action potential produces EPSP, and before it can dissipate another EPSP is triggered, adding on top of first
Spatial summation
- Two or more presynaptic neurons simultaneously have action potentials
- EPSPs generated by neurons at different locations on the post-synaptic neuron
cancellation summation
EPSPs and IPSPs can also summate, and they will cancel each-other out
like fire and dont fire
Graded potentials vs action potentials
location of events
stimulus for event
Distance travelled
Amplitude (size)
Direction of potential change (+ve or -ve)
Direction of conduction
location of events
Graded: cell body and dendrites
Action: Axon hillock to …?
stimulus for event
Graded: Chemical (neurotransmitters)
Sensory stimulus (pressure)
Action:
Voltage (depolarisation)- must reach threshold
Distance travelled
Graded: short- to the axon hillock
Action: long entire length of axon-mm’s to over a meter
Amplitude (size)
Graded: can vary (graded); decays with distance
Action: Always the same size; does not decay with distance
Direction of potential change (+ve or -ve)
Graded: depolarisation or hyperpolarisation
Action: Always same direction
Direction of conduction
Graded: Either direction
Action: One direction (towards terminals)
steps involved in a synapse
ability to draw it
presynaptic cell
synaptic cell
postsynaptic neuron
voltage gated Ca^2+
bubble in membrane
exocytosis
ways to get rid of neurotransmitter
reuptake
enzymatic degradation
diffusion away from synapse
build a neuron
Graded potential Receptive segment
- chemically grated cation channel, k+ channel and Cl-
Axon hillock
- Voltage gated Na+ channel
Voltage gated K+ channel
Conductive segment
- Voltage-gated Na+ channel
Voltage gated K+ channel
transmissive segment
voltage-gated
What is refractory period? and two types
Time in which a region of a neuron cannot trigger another action potential
Absolute and relative refractory period
what is absolute refractory period
- Time from opening of Na+ channels until resetting of the channels- activation gates are closed
- enforces one-way transmission of action potentials
What is relative refractory period
Follows absolute refractory period
- most Na+ channels have returned to their reseting state
- some K+ channels still open
- Action potential can occur, but requires a stronger stimulus to reach
Autonomic nervous system two types
Sympathetic- fight or flight
Increase metabolic rate, heart rate, blood pressure, sweating ect.
Parasympathetic- rest and repose- decrease metabolic rate, heart rate, blood pressure ect.
what are preganglionic neurons synapse with neurons in three groups of ganglia including?
Sympathetic chain ganglia, collateral ganglia and adrenal medullae
Adrenal medullae supplement the sympathetic NS
- Large quantities of epinephrine and norepinephrine into the blood
- When it is released from the adrenal medullae, it is called hormone
- Reaches all tissues of the body - Same effect as direct sympathetic stimulation but lasts 5-10% longer
- Strong effect on metabolism reaching every cell of the body
- 100% increase in metabolic rate
Parasympathetic division
- The cell bodies of preganglionic neurons are in the brain stem and sacral segment of the spinal cord
- Synapse with ganglionic neurons in ganglia that are close to or within the target organ
Neurotransmitters of the ANS
All ANS preganglionic fibres release acetylcholine (Ach)
- Parasympathetic postganglionic fibres
- all release Ach
- Neuroendocrine cells of adrenal medullae release epinephrine/adrenaline (80%) and norepinephrine (20%)
Cholinergic receptors two types and where they are found
1) Nicotinic receptors
- All ganglionic neurons
- The binding is always excitatory
2) Muscarinic
All parasympathetic target organs- smooth muscle, cardiac muscle and glands
- Binding to muscarinic receptors can be excitatory or inhibitory
Adrenergic receptors
- Bind epinephrine and norepinephrine with differing affinities
- Found on sympathetic target organs
- Receptor types
- Alpha (a1 & a2)
- beta (B1, B2 & B3) - Binding of NE or E is excitatory or inhibitory depending on the receptor and target organ
