Neurons

Question 1

Function of Nervous System

Answer 1

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

Question 2

What does a neuron do

Answer 2

Conducts impulses between pns and cns

Question 3

What does a glial cell do

Answer 3

Non conducting
Nourish
Removes waste
Defends again infection

Question 4

Dendrite

Answer 4

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

Question 5

Soma

Answer 5

Has nucleus and site of metabolism

Question 6

Axon

Answer 6

Nerve fiber projection that carry impluses away from soma

Question 7

Myelin Sheath

Answer 7

Insulating coat around axon made of lipids (white fatty)

Speeds up impulse transmission

Question 8

Nucleus of Schwann cell

Answer 8

Glial cell
Forms myelin
Protects and supports neuron

Question 9

Nodes of ranvier

Answer 9

Spaces between Schwann cell along myelin sheath

Impulses jump node to node= High speed transmission

Saltatory conduction

Question 10

Neurilemma

Answer 10

Membrane around myelin

In PNS ONLYYY

Allows regeneration of damaged axons by guiding broken ends together

Question 11

Synaptic terminals

Answer 11

Specialized endings of branched axon

Release neurotransmitters (chemical) to relay signals between neurons l

Question 12

Synapse

Answer 12

Area between neurons

Question 13

Neuromuscular junction

Answer 13

Where neuron and muscle meet

Question 14

Identify the 3 types of neurons and compare and contrast

Answer 14

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

Question 15

Reflex Arc

Answer 15

Involuntary

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

Question 16

Migration of Neurons

Answer 16

Immature neurons must migrate to final position before forming circuits

Mature neurons are stationary but their axons and dendrites grow

Question 17

Development of Axons

Answer 17

Chemical stimulus causes axon to grow from immature neuron

Question 18

Nerve impulse and Cole and Curtis discovery

Answer 18

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)

Question 19

Explain Action Potential and the voltage gated channels involved

Answer 19

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

Question 20

Propagation of Action Potential

Answer 20

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

Question 21

Threshold in Action Potential

Answer 21

Minimum level of stimulus to cause response

Question 22

Presynaptic vs Postsynaptic Neuron and Synaptic Cleft (Synapse)

Answer 22

Pre- Where impulse comes from
Post- Received impulse

SC- Space between 2 neurons or neuromuscular junction

Question 23

Steps in Neurotransfer

Answer 23

1. AP arrived at axon terminal
2. Ca+ channels open and calcium enters (more Ca outside then inside)
3. Increase in membrane potential causes proteins to release vesicles which release neurotransmitters via exocytosis
4. NeuroTM diffuse across cleft and bind to ligand receptor on postsynaptic neuron
5. Postsynaptic neuron changes permeability
6. After NeuroTM transmits msg, it’s broken down by enzymes and reabsorbed into pre synaptic neuron (no longer in cleft)

Question 24

Types of NeuroTM

Answer 24

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

Question 25

Integration

Answer 25

Summation of excitatory and inhibitory NeuroTM

When total integration>threshold=AP

Question 26

Development of Synapses in CNS and PNS

Answer 26

CNS- neuron synapses w another axon, dendrite or soma

PNS- Synapse w muscle or gland

Some form synapse with capillaries