35-2 the nervous system - san dieguito union high school...
TRANSCRIPT
End Show
Slide
1 of 38
Copyright Pearson Prentice Hall
35-2 The Nervous System
There are about 13,500,000
neurons in the human spinal cord
The human brain has about
100billion neurons while an octopus
has about 300 million
Velocity of a signal transmitted
through a neuron= 1.2 to 250 mph
What do you call a skull without
a hundred billion nerves?
End Show
35-2 The Nervous System
Slide
2 of 38
Copyright Pearson Prentice Hall
Neurons
#4Neurons are classified according to the direction in which an impulse travels.
• Sensory neurons (receptors) carry impulses from the sense organs to the CNS. 5 main types -
• Motor neurons (effectors) carry impulses from CNS to muscles and glands.
• Interneurons connect sensory and motor neurons and carry impulses between them.
End Show
35-2 The Nervous System
Slide
3 of 38
Copyright Pearson Prentice Hall
Neurons are the basic functional
unit of the Nervous System!
#5 Structures of a Neuron
Axon
terminals
Myelin
sheath
Cell body
Nodes Axon
Dendrites
Nucleus
Interprets informationReceive
information
carry to the cell
body
Carry impulses away
from cell body
Convert electrical
signal to chemical
to cross synapse
Protects/insulates axon and
helps speed up impulse
transmission
Regenerate nerve
impulse
End Show
35-2 The Nervous System
Slide
4 of 38
Copyright Pearson Prentice Hall
The Nerve Impulse
How do neurons communicate?
ANIMATED BIOLOGICAL CONCEPTS - -
Let’s see it!
End Show
35-2 The Nervous System
Slide
5 of 38
Copyright Pearson Prentice Hall
The Nerve Impulse
The Resting Potential
At rest the outside of the neuron
has a net positive charge.
The inside of the neuron has a
net negative charge.
When stimulated by another neuron or
the environment, Sodium
channels/gates open and Sodium ions
(+) flood in.
Membrane becomes positively charged. If it
becomes positive enough – reaches threshold –
and action potential generated
As impulse passes by, K+ gates open and
K+ flows out of cell – making it negative
inside again (resting potential)
End Show
35-2 The Nervous System
Slide
6 of 38
Copyright Pearson Prentice Hall
The Nerve Impulse
Threshold
A stimulus must be of adequate strength to cause a neuron to transmit an impulse.
The minimum level of a stimulus that is required to activate a neuron is called the threshold.
A stimulus that is stronger than the threshold produces an impulse.
A stimulus that is weaker than the threshold produces no impulse.
THINK: Why different levels of Pain?
What did the stimulus do to the neuron after
they got married?
End Show
35-2 The Nervous System
Slide
7 of 38
Copyright Pearson Prentice Hall
The Synapse
A Synapse
End Show
35-2 The Nervous System
Slide
8 of 38
Copyright Pearson Prentice Hall
The Synapse
The synaptic cleft
separates the axon
terminal from the
dendrites of the
adjacent cell.
Synaptic cleft
End Show
35-2 The Nervous System
Slide
9 of 38
Copyright Pearson Prentice Hall
The Synapse
Terminals contain
vesicles filled with
neurotransmitters.
Neurotransmitters
are chemicals used by
a neuron to transmit
an impulse across a
synapse to another
cell.
Vesicle
Neurotransmitter
End Show
35-2 The Nervous System
Slide
10 of 38
Copyright Pearson Prentice Hall
The Synapse
As an impulse
reaches a terminal,
vesicles send
neurotransmitters
into the synaptic
cleft.
These diffuse across
the cleft and attach
to membrane
receptors on the
next cell.
Receptor
End Show
35-2 The Nervous System
Slide
11 of 38
CLASS IMPULSE TIME
maybe . . .
Copyright Pearson Prentice Hall
End Show
35-2 The Nervous System
Slide
12 of 38
Copyright Pearson Prentice Hall
Basic interaction of the 3 types of neurons
• Reflex Arc
#7,8,9
(35-3)
Sensory
receptors
Effector (responding
muscle)
Interneuron Spinal cord
Sensory neuron
Motor
neuron
What about Pain?