Transcript Nervous System - mr-youssef-mci

Vertebrate Nervous Systems
Two major subsystems:
1. central nervous system
(CNS) – brain and spinal
cord
2.
peripheral nervous system
(PNS) – nerves outside of
the brain and spinal cord
Brain
Spinal Cord
Miami Project – Spinal Cord Injury Research
Peripheral Nervous System
Contains two main nerve types:
1. somatic nerves
 involved with voluntary movement
senses / movement
2. autonomic nerves
 involved with involuntary movement
sympathetic / parasympathetic systems
Cells of the Nervous System
Two major cell types:
1. neurons
 conduct electrical
signals
2. glial cells
 structural & insulating
support for neurons
Neuron Structure
dendrites
axon terminal
soma
node of Ranvier
axon
nucleus
glial cell
Dendrites
Cell body
Nucleus
Synapse
Signal
Axon direction
Axon hillock
Presynaptic cell
Postsynaptic cell
Myelin sheath
Figure 48.5
Synaptic
terminals
Glial Cells
Sensory input
Integration
Sensor
Motor output
Effector
Figure 48.3
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
Neuron Signalling
How do electrical signals pass through cells?
Membrane Potential
 glial cells provide insulation for electrical
impulses to pass through axon
 glial cell membrane has a lot of lipid molecules
 called a myelin sheath
 neurilemma - myelin sheaths wrapped around
each other
Glial Cell
Node of Ranvier
Layers of myelin
Axon
Schwann
cell
Axon
Figure 48.8
Myelin sheath
Nodes of
Ranvier
Schwann
cell
Nucleus of
Schwann cell
0.1 µm
Grey / White Matter
Why are brains said to be made of grey and white
matter?
 white matter – neurons with neurilemma
 grey matter – neurons without neurilemma
Grey / White Matter
Neuron Types
Dendrites
Axon
Cell
body
Figure 48.6a–c (a) Sensory neuron
(b) Interneurons
(c) Motor neuron
Neuron Types
ganglia
Sensory Neuron
 also known as afferent neurons
 carries signals from sensory receptors to the CNS for
processing
 photoreceptors (eyes)
 chemoreceptors (nose)
 thermoreceptors (skin)
 found in clusters of neurons—ganglia
Ganglia
Neuron Types
Interneuron
 also known as association neurons
 receives incoming signals from sensory neurons
 delivers outgoing signals to neurons responsible for
responses
Neuron Types
Motor Neuron
 also known as efferent neurons
 connected to tissues that respond according what
was detected
 muscle contraction
 gland secretion
Neuron Responses
Does all information detected by your senses go
through your brain?
 reflex arc – connects sensory and motor neurons
without going to the brain
Reflex Arc
gure 48.4
2 Sensors detect
a sudden stretch in
the quadriceps.
3 Sensory neurons
convey the information
to the spinal cord.
Cell body of
sensory neuron
in dorsal
root ganglion
4 The sensory neurons communicate with
motor neurons that supply the quadriceps. The
motor neurons convey signals to the quadriceps,
causing it to contract and jerking the lower leg forward.
Gray matter
5 Sensory neurons
from the quadriceps
also communicate
with interneurons
in the spinal cord.
Quadriceps
muscle
White
matter
Hamstring
muscle
Spinal cord
(cross section)
Sensory neuron
Motor neuron
1 The reflex is
initiated by tapping
the tendon connected
to the quadriceps
(extensor) muscle.
Interneuron
6 The interneurons
inhibit motor neurons
that supply the
hamstring (flexor)
muscle. This inhibition
prevents the hamstring
from contracting,
which would resist
the action of
the quadriceps.
Neuron Repair
Do neurons regenerate?
Yes. Peripheral system neurons will repair faster than
central system neurons.
http://www.ted.com/talks/ed_boyden.html
http://www.ted.com/talks/alan_russell_on_regenerating
_our_bodies.html
Homework Section 9.1 p. 417# 1 – 8