Neurons

Taking in and interpreting sensory info, determining response and signalling appropriate effector to respond

Conducts impulses between pns and cns

Non conducting Nourish Removes waste Defends again infection

Branching nerve fiber Received impulse from other neurons and relays it to soma

Has nucleus and site of metabolism

Nerve fiber projection that carry impluses away from soma

Insulating coat around axon made of lipids (white fatty) Speeds up impulse transmission

Glial cell Forms myelin Protects and supports neuron

Spaces between Schwann cell along myelin sheath Impulses jump node to node= High speed transmission Saltatory conduction

Membrane around myelin In PNS ONLYYY Allows regeneration of damaged axons by guiding broken ends together

Specialized endings of branched axon Release neurotransmitters (chemical) to relay signals between neurons l

Area between neurons

Where neuron and muscle meet

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

Involuntary 1 Sensory receptors detects stimuli 2 Sensory neuron tells CNS 3 Interneuron (Spinal Cord) 4 Motor neuron relays info to effector which responds

Immature neurons must migrate to final position before forming circuits Mature neurons are stationary but their axons and dendrites grow

Chemical stimulus causes axon to grow from immature neuron

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)

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

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

Minimum level of stimulus to cause response

Pre- Where impulse comes from Post- Received impulse SC- Space between 2 neurons or neuromuscular junction

• 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)

Excitatory- Allow Na into neuron (depolarization) Inhibitory- Allow K out (hyper polarization)