Download The Nervous System and Neurons

Mr. E Murphy
Strange fact
A newborn baby's brain grows almost 3
times during the course of its first year.
Objectives
 Identify the importance of the nervous system in
humans
 Know the difference between the CNS and the PNS
 Structure of the neuron
The nervous system
 Nervous system and
the endocrine allow
animals to respond to
stimuli
CNS vs PNS
CNS = Central nervous system
Brain and spinal cord
PNS = Peripheral nervous system
Network of nerves that carry
messages from CNS to the body
Response to a stimulus
1.

2.

3.

4.

Reception
Stimulus is detected
Transmission
Message is transferred
Integration
What does the message say??
Response
The effect of the message
Neurons
A neuron is a nerve cell

1.
2.
3.
Three types of
neurons:
Sensory
Motor
Interneuron
Summary
 Identify the importance of the nervous system in
humans
 Know the difference between the CNS and the PNS
 Structure of the neuron
Mr. E Murphy
Objectives
 Explain the role of the different parts of the neuron
 Describe the movement of a nerve impulse
 Illustrate the transfer of a message at a synapse
Keywords
 Resting Neuron
 Threshold
 ‘All or nothing law’
Neuron
 Cell body
 Dendrites
 Axon
 Myelin sheath
 Schwann cell
 Neurotransmitter
vesicles
Copy diagram into your note copy
Neuron Structure
 Cell Body: Nucleus of the neuron is contained in the
cell body
 Dendrites: Carry messages towards the cell body
(sensory)
 Axons: Carry messages away from the cell body
(motor)
 Myelin sheath: acts as an insulator around the axon,
speeds up the transport of messages
Neuron structure
 Schwann cells: Produce the myelin sheath
 Nodes of Ranvier: Gaps in the neuron.
Nerve
impulse
 Refractory period: 5/1000 of a second delay
 Speed of an impulse:
 With myelin sheath 120 m/sec
 Without myelin sheath 2 m/sec
Synapse
Passage of an impulse along a neuron
Cell
body
+++++++++++++++
----------------------------------------+++++++++++++++
Resting
Neuron
Stimulus changes the
charge
Stimulus
-------++++++++++
+++++-------------+++++-------------- - - - - - -+ + + + + + + + + +
This change triggers the next
section
axon
Charge is restored
+++++-------+++++
-------+++++-------------+++++------+++++-------+++++
Charge travels along the axon
 When the threshold is reached the axon changes its permeability to




ions
This causes a chain reaction
Inside +ve, Outside –ve
Requires energy ( ATP)
Once the impulse has passed the area behind returns to resting state
Synapse
Functions of synapses
1.
2.
3.
4.
Transmit impulses from one neuron to another or to
an effector
Control the direction of an impulse
Prevent over stimulation of effectors
Impulse can be blocked, important in controlling
pain
Summary
 Explain the role of the different parts of the neuron
 Describe the movement of a nerve impulse
 Illustrate the transfer of a message at a synapse
Mr. E Murphy
Objectives
 Central nervous system: Brain and Spinal cord
 Location and function of the different brain parts
 Illustrate the cross section of the spinal cord
 Peripheral Nervous System
 Reflex action
CNS
 Brain and the spinal cord
Brain parts
 Cerebrum:
• Largest part of the brain
• 75% of the neurons in the brain
• Two halves (right and left cerebral hemispheres)
• Voluntary movements, interpreting results from
the sense organs, intelligence etc.
• Left hand side = hand use, language, maths
• Right hand side = art, music, emotion
• Cerebral cortex (outer part of cerebrum)
• ........4 lobes, control different functions
Brain Parts
 Cerebellum:
• Controls muscular coordination and balance
• Involuntary
 Medulla oblongata
• Connects spinal cord with the brain
• Involuntary actions (breathing, coughing)
Brain Parts
 Thalmus
• Sorting centre for brain, relaying messages
 Hypothalmus
• Regulates the internal environment of the body
(homeostasis)
• Link between mind (brain) and the body??
Brain Parts
 Pituitary gland
• Not part of the brain
• Produces hormones
Mr. E Murphy
Objectives
 Brain structure and function
 Parkinson’s disease
 Spinal cord
CNS
 Brain and the spinal cord
Meninges
Cerebrum
gland
Oblongata
The brain
 12,000 million neurons
 Cell bodies and synapses form the grey matter of the
brain, with the nerve fibres forming the white matter
 Brain and spinal cord are protected by bone and are
covered by three membranes called meninges
 Meningitis is the inflammation of the meninges
Brain parts
 Cerebrum:
• Largest part of the brain
• 75% of the neurons in the brain
• Two halves (right and left cerebral hemispheres)
• Voluntary movements, interpreting results from
the sense organs, intelligence etc.
• Left hand side = hand use, language, maths
• Right hand side = art, music, emotion
• Cerebral cortex (outer part of cerebrum)
• ........4 lobes, control different functions
Brain Parts
 Cerebellum:
• Controls muscular coordination and balance
• Involuntary
 Medulla oblongata
• Connects spinal cord with the brain
• Involuntary actions (breathing, coughing)
Brain Parts
 Thalmus
• Sorting centre for brain, relaying messages
 Hypothalmus
• Regulates the internal environment of the body
(homeostasis)
• Link between mind (brain) and the body??
Brain Parts
 Pituitary gland
• Not part of the brain
• Produces hormones
Parkinson’s disease
 Nervous system disorder
Cause:
 Failure to produce a neurotransmitter called
dopamine in a part of the brain
Effect: Inability to control muscle contraction
Symptoms:
 Trembling of the hands and legs
 Later muscles and body become stiff and rigid
 Facial expression can become fixed and has an
unblinking stare
 Everyday activities become difficult
 Thought process not affected until late in the
disease
Prevention: No way to prevent or cure
Treatment:
 Initial treatment exercise
 Home help
 Drugs can reduce symptoms, but not stop the
degeneration of the brain
Mr. E Murphy
Objectives
 Spinal Cord
 Peripheral Nervous System
 Reflex action
Parkinson’s disease
 Nervous system disorder
Cause:
 Failure to produce a neurotransmitter called
dopamine in a part of the brain
Effect: Inability to control muscle contraction
Symptoms:
 Trembling of the hands and legs
 Later muscles and body become stiff and rigid
 Facial expression can become fixed and has an
unblinking stare
 Everyday activities become difficult
 Thought process not affected until late in the
disease
Prevention: No way to prevent or cure
Treatment:
 Initial treatment exercise
 Home help
 Drugs can reduce symptoms, but not stop the
degeneration of the brain
Spinal cord
 Made up of nerve tissue
 Protected by bony vertebrate
 The spinal cord transmits messages to and from
the brain
 Location: Neural canal of vertebrate
 Neural canal is lined by meninges
 Dorsal root carries sensory neurons into the spinal
cord, ventral neurons carry motor neurons out
 Dorsal root swellings contain ganglia (groups of
cell bodies of sensory neurons)
Peripheral
Nervous
System
(PNS)
 Mainly nerve fibres outside the brain and spinal cord
 Consists of long dendrites or axons taking impulses to
or from the CNS
 Nerve fibres do not contain cell bodies
Peripheral Nervous System (PNS)
Cell bodies of sensory nerves are located in ganglia
in the PNS (Dorsal root ganglia)
Cell bodies of motor neurons are found in the CNS
(Grey matter of the brain and the spinal cord)
Reflex Action
The simplest form of activity in the nervous system is a
reflex action
 Automatic, involuntary, unthinking response to a
stimulus
 Neurons which make up the pathway taken by nerve
impulses in a reflex action make up a reflex arc
Reflex Action
 E.g. grasp reflex in
babies, movement of the
iris in the eye, blinking
our eyes for protection,
and protecting ourselves
when we fall
 Fast reaction, allowing us
to protect our body
Withdrawal reflex
1.
2.
3.
4.
5.
Receptors in the fingers are stimulated by the hot flame
Sensory neurons carry an impulse into the spinal cord
a) An interneuron carries the impulse across the spinal
cord to a motor neuron
b) Another neuron takes the impulse up to the brain
Motor neurons take the impulse straight out of the
spine to the effector (i.e. muscle)
This causes the hand to pull back
At the same time as the hand is withdrawn, the impulse
reaches the brain. Then we feel pain
Activity
 Complete exam questions
 2010 Q 11 a, b
 2009 Q 15 c ii
 2008 Q 4
 2006 Q 14 b
 2005 Q 3b, Q 14 c) ii
 2004 Q 15 a
Solutions
2012 Q 13
Solutions
2012 Q 13
Solutions
2010 Q 11 a, b
Solutions
2009 Q 15 c ii)
2008 Q 4
Solutions
2006 Q 14 b)
Solutions
2005 Q 3 b), 14 c) ii
Solutions
2004 Q 15 a)
Solutions
2012 OL Q 15 b)
Solutions
2007 OL Q 15 a)