Neurons Flashcards
Function of Nervous System
Taking in and interpreting sensory info, determining response and signalling appropriate effector to respond
What does a neuron do
Conducts impulses between pns and cns
What does a glial cell do
Non conducting
Nourish
Removes waste
Defends again infection
Dendrite
Branching nerve fiber
Received impulse from other neurons and relays it to soma
Soma
Has nucleus and site of metabolism
Axon
Nerve fiber projection that carry impluses away from soma
Myelin Sheath
Insulating coat around axon made of lipids (white fatty)
Speeds up impulse transmission
Nucleus of Schwann cell
Glial cell
Forms myelin
Protects and supports neuron
Nodes of ranvier
Spaces between Schwann cell along myelin sheath
Impulses jump node to node= High speed transmission
Saltatory conduction
Neurilemma
Membrane around myelin
In PNS ONLYYY
Allows regeneration of damaged axons by guiding broken ends together
Synaptic terminals
Specialized endings of branched axon
Release neurotransmitters (chemical) to relay signals between neurons l
Synapse
Area between neurons
Neuromuscular junction
Where neuron and muscle meet
Identify the 3 types of neurons and compare and contrast
Sensory- PNS, myelinated, detect environment changes, carry impulse to CNS, soma in center of neuron, long dendrites and axons
Interneurons- CNS, Not always myelinated, connect motor and sensory neurons, cell body at end, short dendrites w/ branches in axon
Motor- PNS, always myelinated, carry impulses from CNS to muscle, soma at DENDRITE end, short dendrite long axons
Reflex Arc
Involuntary
1 Sensory receptors detects stimuli
2 Sensory neuron tells CNS
3 Interneuron (Spinal Cord)
4 Motor neuron relays info to effector which responds
Migration of Neurons
Immature neurons must migrate to final position before forming circuits
Mature neurons are stationary but their axons and dendrites grow
Development of Axons
Chemical stimulus causes axon to grow from immature neuron
Nerve impulse and Cole and Curtis discovery
NI- Electrochemicla msgs due to ion movement
Cole and Curtis- Giant squid axon and found inside of axon was more negative then outside when unstimulated (resting potential- more Na outside and less K+ inside so outside more positive)
Explain Action Potential and the voltage gated channels involved
Initial Concentration Gradient- More Na outside, more k+ inside
Resting potential- (-70mV) when unstimulated (membrane more permeable to K+ and leaky k+ channel allow more K+ to go out then Na to come in= + charge leaving makes inside negative)
Depolarization- Stimulus causes voltage gated Na channel to open. Bcz more Na outside then inside, Na rush into axon= Inside bcz + and keeps rising to 40mV
Repolarization- Na channels close once Na at equilibrium and K+ channel opens. More K+ inside then outside so K+ leave. Positive charge leaving= inside becomes negative
Hyperpolarization- K+ channel close slowly so K+ keep leaving so inside membrane potential becomes more negative then resting potential (-75)
Refractory Period- Na and K are at equilibrium now so to return to initial concentration gradient, sodium potassium pump uses ATP to pump 3Na out:2 K in
Propagation of Action Potential
AP at one point on axon triggers AP on next axon (Domino effect)
Ion movement that causes depolarizion in one part of axon will cause it in the next
Threshold in Action Potential
Minimum level of stimulus to cause response
Presynaptic vs Postsynaptic Neuron and Synaptic Cleft (Synapse)
Pre- Where impulse comes from
Post- Received impulse
SC- Space between 2 neurons or neuromuscular junction
Steps in Neurotransfer
- AP arrived at axon terminal
- Ca+ channels open and calcium enters (more Ca outside then inside)
- Increase in membrane potential causes proteins to release vesicles which release neurotransmitters via exocytosis
- NeuroTM diffuse across cleft and bind to ligand receptor on postsynaptic neuron
- Postsynaptic neuron changes permeability
- After NeuroTM transmits msg, it’s broken down by enzymes and reabsorbed into pre synaptic neuron (no longer in cleft)
Types of NeuroTM
Excitatory- Allow Na into neuron (depolarization)
Inhibitory- Allow K out (hyper polarization)
Integration
Summation of excitatory and inhibitory NeuroTM
When total integration>threshold=AP
Development of Synapses in CNS and PNS
CNS- neuron synapses w another axon, dendrite or soma
PNS- Synapse w muscle or gland
Some form synapse with capillaries
