2t Bricks 1 par. 5.9 Neurons

• Biologie
• Middelbare school
• vwo
• Leerjaar 2

5.9 Neurons

The Nervous system

The nervous system controls your muscles 

-walk / write / exercise 

-swallowing / blinking / breathing

-Central nervous system vs. 

-Peripheral nervous system

Which parts belong to the central nervous system?

The central nervous system (CNS)

Nerve cells / neurons 

• Sense organs (receptors) send messages: electric impulses --> to the CNS via Sensory neurons

• CNS send electric impulses --> to muscles and glands (effectors)  telling them wat to do via Motor neurons

• Interneurons  are the connections between sensory and motorneurons.(in the spinal cord and the brain)

Electric impuls

The message is:

- is super fast 

- called impulses (electrical signals)

- goes via the axon of the nerve cell

- has fatty sheat: myelin sheath around axons make the impuls travel faster

Responding to a stimulus

1. Receptor		Sensory cells in sense organ
2. Sensory neuron		Gathers and sends impulses from the senses
3. Inter neuron		Communicates between the different parts of the CNS
4. Spinal cord / brain
5. Motor neuron	->	Sends impulses to effector cells
6. Effector		Muscles, glands

You get an itch in your elbow. What is the stimulus in this reaction?

1. Receptors in your skin
2. The itch itself
3. muscles that move your arm to scratch
4. The brain that decides to scratch the elbow

You get an itch in your elbow. What is the response in this reaction?

1. Receptors in your skin
2. The itch itself
3. muscles that move your arm to scratch
4. The brain that decides to scratch the elbow

Which will send an impulse along sensory neurons?

1. Receptors in your skin
2. The spinal cord
3. The muscles in your arm
4. The brain

Which will receive an impulse by motor neurons?

1. Receptors in your skin
2. The spinal cord
3. The muscles in your arm
4. The brain

Sensory neurons carry information

1. away from the brain.
2. both to and from the brain.
3. towards the brain.
4. within the brain

True

False

Motor (efferent) neurons carry messages to the central nervous system.

The nucleus of a neuron is found outside the cell body (soma)

Motor Neuron

Inter neuron

Sensory neuron

Found in visual system, brain, and spinal cord, pass informatiion on

carry electrical impulses away from the brain and spinal cord

Take information from sense organs to the brain and spinal cord

Normal situation

In a soccer match a player kicks the ball to the goal.

The goal keeper sees the ball and he jumps and catches it.

Describe the pathway in the goal keeper's nervous system.

Describe the pathway in the goal keeper's nervous system.

First:

Light from the ball –> 

sensory receptors of the eye –>  

impulses by sensory neurones –> 

impulses by interneurons in spinal cord + brain stem –> 

brain (vision area).

Now the keeper is aware of the ball

Now the keeper is aware of the ball 😜

After that:

Brain (motor area) creates impulses -> 

impulses by interneurons in brain stem + spinal cord –> impulses by motor neurons –> 

muscles in legs and arms

Now the keeper jumps and catches the ball!

Dendrite

Cell body

Nucleus

Axon

Fatty sheath

Synapse

Nerves and neurons

spinal cord - grey and white matter

When you touch an hot object... you take away your hand very fast
It goes automatically, why?

Reflex arcs

• When you touch an hot object... you take away your hand very fast
  It goes automatically, why? 
  
  
• Reflexes protect you 
• Why do you think a reflex is unconscious? 
  
  

Why do you think a reflex is unconscious?

Reflex arcs

•  Why do you think a reflex is unconscious? 

• Impulses do not go to the brain immediately

• They go to the spinal cord and back (short circuit) 

Reflex arcs

W

1. Stimulus= 

2. Receptor= 

3. Effector= 

4. Response= 

1. stimulus is: ..... 2. receptor is: .....
3. effector is: ..... 4. effector is: .....

Reflex arcs

1. Stimulus = hot flame     2. Receptor = heat sensor in the skin 

3. Effector = muscles in your arm 

4. Response = moving your hand away from the hot object. 

How do reflexes work?

• Reflexes are involuntary.
  
• Don’t ‘think’ about them: it just happens
  
• So fast they don’t go to the brain!
  
• Controlled by the spinal cord.
  

Refelex arc

warmth from the flame –> sensory receptors of the skin –> impulses by sensory neurones –> impulses by interneurons in spinal cord –> impulses by motor neurons -> muscles in the arm contract

Without knowing you raised your arm!

Reflex arc: diagram

Reflex or not???

Reflex

Reflex

concious

trained reflex