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Nervous System. Nervous System. Made up of nerve cells called neurons found in the: Brain Spinal Cord All of the nerve cells connected to all other parts of the body. Nervous System. The nervous system can be divided into the: Central Nervous System – brain and spinal cord - PowerPoint PPT Presentation
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Nervous SystemNervous SystemNervous SystemNervous System Made up of nerve Made up of nerve
cells called cells called neurons neurons found in the:found in the:
BrainBrain
Spinal CordSpinal Cord
All of the nerve cells All of the nerve cells connected to all connected to all other parts of the other parts of the body body
Nervous SystemNervous SystemNervous SystemNervous System The nervous The nervous
system can be system can be divided into the:divided into the:– Central Nervous Central Nervous
SystemSystem – brain and – brain and spinal cordspinal cord
– Peripheral Nervous Peripheral Nervous SystemSystem – neurons – neurons outside the spinal outside the spinal cord/braincord/brain
PNSPNSPNSPNS
The PNS is made up of:The PNS is made up of:
– Sensory neurons (affector neurons) Sensory neurons (affector neurons) – detect – detect changes in the external and internal changes in the external and internal environment and sends information environment and sends information toto the the CNSCNS
– Motor neurons (effector neurons) Motor neurons (effector neurons) – send – send information information away fromaway from the CNS to muscles the CNS to muscles and other effector organsand other effector organs
PNSPNSPNSPNS The motor neurons of the The motor neurons of the
PNS can be further divided PNS can be further divided into 2 categories:into 2 categories:
Autonomic nervous Autonomic nervous system system – involuntary, – involuntary, transmits messages to transmits messages to internal organsinternal organs
cannot be consciously cannot be consciously controlled by thoughtscontrolled by thoughts
Somatic nervous Somatic nervous system system – voluntary, – voluntary, transmits messages to transmits messages to skeletal muscleskeletal muscle
can be consciously can be consciously controlledcontrolled
CNSCNSCNSCNS The CNS acts as the control centre The CNS acts as the control centre
of the entire nervous system:of the entire nervous system:
– It processes the information received It processes the information received by the sensory neurons in the PNS; by the sensory neurons in the PNS; and and
– sends messages back through motor sends messages back through motor neurons in the PNS to the effector neurons in the PNS to the effector organs, initiating a response.organs, initiating a response.
SummarySummarySummarySummaryNervous Nervous systemsystem
CNSCNS PNSPNS
SensorSensoryy
MotorMotor
AutonomiAutonomic c
SomaticSomatic
BrainBrainSpinal Spinal CordCord
VoluntaryVoluntary
InvoluntaryInvoluntary
Nerve cells, NeuronsNerve cells, NeuronsNerve cells, NeuronsNerve cells, Neurons These are the basic units of the These are the basic units of the
nervous systemnervous system There are 3 main types:There are 3 main types:
– SensorySensory (affector) (affector)– Motor (effector) (effector)– Interneurons Interneurons (connecting neurons)(connecting neurons)
When many neurons are When many neurons are connected together in a bundle, connected together in a bundle, they are called a nervethey are called a nerve
Typical motor neuronTypical motor neuronTypical motor neuronTypical motor neuron
Reflex arcReflex arcReflex arcReflex arc
NeuronsNeuronsNeuronsNeurons Neurons are able to pass Neurons are able to pass
messages onto other neurons and messages onto other neurons and cells by sending electrical cells by sending electrical impulses called impulses called action potentialsaction potentials
Electrical impulses are created by Electrical impulses are created by a rapid change in a rapid change in positive/negative charges across positive/negative charges across the membrane of the neuronthe membrane of the neuron
Electrical impulses are generated Electrical impulses are generated when a stimulus is detectedwhen a stimulus is detected
Action PotentialsAction PotentialsAction PotentialsAction Potentials There are 4 main phases in an There are 4 main phases in an
action potential:action potential:
1.1.Resting potentialResting potential – when neuron – when neuron is not active/stimulated - there is not active/stimulated - there is a difference in charge across is a difference in charge across membrane, called potential membrane, called potential More + outside membrane More + outside membrane
compared to insidecompared to inside
2.2. Depolarisation Depolarisation – when the neuron is – when the neuron is stimulated the potential reverses stimulated the potential reverses and this change in potential is and this change in potential is carried along the axon to the axon carried along the axon to the axon terminal, causing a signalling terminal, causing a signalling molecule called a molecule called a neurotransmitterneurotransmitter (within the secretory vesicles) to be (within the secretory vesicles) to be releasedreleased
• This neurotransmitter then diffuses This neurotransmitter then diffuses across a very short distance (called a across a very short distance (called a synapsesynapse) to the neighbouring ) to the neighbouring ((postsynapticpostsynaptic neuron, causing it to be neuron, causing it to be stimulatedstimulated
Action PotentialsAction PotentialsAction PotentialsAction Potentials
Action PotentialsAction PotentialsAction PotentialsAction Potentials3.3.RepolarisationRepolarisation – The potential – The potential
returns to resting statereturns to resting state More + outside membrane More + outside membrane
compared to insidecompared to inside
4.4.Refractory period Refractory period – For a brief – For a brief period after repolarisation, the period after repolarisation, the neuron cannot be stimulated neuron cannot be stimulated againagain
http://www.learner.org/channel/courses/http://www.learner.org/channel/courses/biology/archive/animations/hires/biology/archive/animations/hires/a_neuro1_h.htmla_neuro1_h.html
http://www.learner.org/channel/courses/biology/archive/animations/hires/a_neuro2_h.html
Resting potential
Depolarisation – stimulus reached threshold
Repolarisation
Na+ comes into neuron
K+ flows out of neuron
AnimationsAnimations
http://http://outreach.mcb.harvard.edu/outreach.mcb.harvard.edu/animations/actionpotential.swfanimations/actionpotential.swf
– Toxins and venoms produced by Toxins and venoms produced by animals such as snakes and animals such as snakes and spiders can cause paralysisspiders can cause paralysis
– This is because they can:This is because they can: interfere with the release of interfere with the release of
neurotransmitters neurotransmitters Prevent transmission of electrical Prevent transmission of electrical
impulses from travelling along the impulses from travelling along the axonaxon
Damage the presynaptic or post-Damage the presynaptic or post-synaptic membranessynaptic membranes
Toxins and venomToxins and venomToxins and venomToxins and venom