Unit 9 - Nervous System Flashcards by Mackenzie Fuller

What are neurons?

Specialized cells that conduct nerve impulses (nerve cells)

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What is a neuron composed of?

Dendrites
Cell body
Axon

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What is a neuron composed of?

Dendrites
Cell body
Axon

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What are dendrites?

Short processes that conduct an impulse towards the cell body. Usually branches

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What is the cell body?

Contains the nucleus and maintains the cell

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What is the axon?

Long process conducts an impulse away from the cell body

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What is information flow in the neurons?

One directional. It only flows from dendrites to the axon

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What are the three types of neurons?

Sensory neurons
Inter neurons
Motor neurons

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What do the three neurons make up?

The reflex arc

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What do receptors do?

Detects stimuli that surpasses a threshold
Initiates impulse in the sensory neuron

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What does the receptor do?

Detects stimuli that surpasses a threshold
Initiates impulse in the sensory neuron

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What are some examples of receptors?

Stretch receptor in the alveoli of the lungs
Pain receptor in the skin
Photo receptor in the eyes - light
Chemo receptors in heart and brain - chemicals ex. Tastebuds

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Describe a sensory neuron

Long dendrite
Nucleus in the dorsal root ganglion (cell body) on the side
Takes sensory info from the receptor to the interneuron

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Describe an interneuron

Short dendrite and short axon
Entirely in the spinal cord or cns
Connects sensory neuron with the correct motor neuron to get correct response

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Describe a motor neuron

Short dendrites and long axon (up to 3cm)
Dendrites are in the cns, axon is outside the spinal cord
Takes the impulse to an effector

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What is an effector?

A muscle or gland
When stimulated, muscle will contract
When stimulated, gland will release a hormone

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Why can the dendrite of a sensory neuron be in?

Thé sans nerve as the axon of a motor neuron

What do long fibres of neurons make up?

Mixed nerves

What is in mixed nerves?

Hundreds of long fibres from different neurons taking messages, electrical impulses in both directions to different places.

What is a nerve?

A bundle of long fibres from neurons

What are long fibres covered with?

A fatty sheath called The myelin sheath

What is the myelin sheath composed of?

Schwann cells that wrap around the nerve fibre

What are the two functions of a Myelin sheath?

It insulated the neurons from each other as they pass through the nerve

It helps to speed up the impulse

What are the points between Schwann cells called?

Nodes of ranvier

What do the nodes of ranvier do?

Speed the impulse as it jumps from node to node

What is the location and function of a sensory neuron?

Throughout the body Connects receptors to interneuron

What is the location and function of an interneuron?

Nerve cord Connects sensory to motor neurons Has no Schwann cells

What is the location and function of a motor neuron?

Throughout the body Connects the interneuron to effector

What is a reflex arc?

Fast reaction. Nerve impulse passes the brain

Examples of a reflex arc

Pinprick on finger Spider crawling on leg

Are nerve pulses electrical in nature?

Yes

When a nerve impulse travels along a nerve fibre what is there a wave of?

Ionic charges that occur which creates a very small shift in the electrical nature of the fibre

What does an axon look like at rest?

-20mV SODIUM IONS (+ve): concentrated on the outside of the axon POTASSIUM IONS (+ve) and negative organic ions are concentrated on the inside of the axon The outside of the neuron is slightly positive The membrane is not permeable to these ions The sodium and potassium gates are closed Ions can not move in or out of the nerve cell

Axon during depolarization (at peak)

+30mV If a stimulus is strong enough and surpasses threshold (-55mV), the membrane is suddenly made permeable to sodium Sodium gates open Sodium ions go inside of the axon

Axon during repolarization (lowest point)

-70mV When the voltage reaches +30mV, it causes the potassium gates to open, and the potassium goes to the outside Causes the initial polarity or be restored (-70mV), the ions are in reverse positions The sodium gates close

Axon during recovery phase (refractory period)

At -70mV all gates close The sodium potassium pump (help from ATP) actively pumps the sodium and potassium ions back to their original condition During recovery the neuron cannot fire

What is the all or none response?

Each impulse is equal to all other impulses A stronger stimulus does not mean a bigger impulse, but it means a greater number of impulses will give bigger results

What makes integration?

Excitatory signals + inhibitory signals

What allows the impulse to move faster?

The myelin sheath. It surrounds the long fibres

What allows the impulse to move faster?

The myelin sheath. It surrounds the long fibres

What is action potential?

The ionic nature of the fibre associated with the movement of the impulse

What is the small space between neurons called?

The synaptic gap