Download Nervous System

Nervous System
Copyright © 2010 Pearson Education, Inc.
2 types of cells
1. Neurons (nerves) –
receive & transmit
biochemical &
electrical signals
2. Glial cells – provide
support for neurons
CNS
Anatomy of the Brain
Brain – 3 main parts
• Cerebrum
– largest part
– controls conscious functions (reasoning,
sight, speech, touch, hearing, etc)
• Cerebellum
- coordinates body movement (linked to motor
neurons)
• Brain stem (midbrain, pons, medulla)
– connects brain & spinal cord
– Controls unconscious functions (heart rate,
breathing, blood pressure, vomiting, etc)
Sensory and Motor Areas of the Cerebral Cortex
homunculus
Brain Dysfunctions
• Traumatic Brain Injuries
– Concussion – brain impact
– Contusion – tissue destruction
– Cerebral edema - swelling
• Cerebrovascular Accidents
– Ischemic stroke – blood clot
– Hemorrhagic stroke – brain bleed
• CNS Degenerative Diseases
– Alzheimer’s Disease – shortage of ACh/brain atrophy,
results in dementia
– Parkinson’s Disease - dopamine-releasing neurons in
midbrain, results in persistent tremors, overstimulation
– Huntington’s Disease – cerebral cortex, inhibition of motor
reflexes
Spinal Cord
• Long, thin bundle
of nervous tissue
(~ 18 in long)
• Passes message
from brain to body
and body to brain
• Surrounded by
vertebrae
Spinal Cord Structure
Cord
– Outside: white
matter (myelin
sheaths)
– Inside: gray matter
(cell bodies w/no
myelin sheaths)
Meninges
- dura mater
- arachnoid mater
- pia mater
PNS
Figure 11.23 A simple reflex arc.
Stimulus
1 Receptor
Interneuron
2 Sensory neuron
3 Integration center
4 Motor neuron
5 Effector
Spinal cord (CNS)
Response
Copyright © 2010 Pearson Education, Inc.
Structure of a motor neuron
Dendrites
(receptive regions)
Cell body
(biosynthetic center
and receptive region)
Nucleolus
Axon
(impulse generating
and conducting region)
Nucleus
Nissl bodies
Axon hillock
(b)
Copyright © 2010 Pearson Education, Inc.
Impulse
direction
Node of Ranvier
Schwann cell
Neurilemma (one interTerminal
node)
branches
Axon
terminals
(secretory
region)
Figure 11.4a Structure of a motor neuron.
Neuron cell body
(a)
Copyright © 2010 Pearson Education, Inc.
Dendritic spine
Figure 11.16 Synapses.
Axodendritic
synapses
Dendrites
Axosomatic
synapses
Cell body
Axoaxonic synapses
(a)
Axon
Axon
Axosomatic
synapses
(b)
Copyright © 2010 Pearson Education, Inc.
Cell body (soma) of
postsynaptic neuron
Nerve Transmission
Neurotransmission(NIH):
https://www.youtube.com/embed/XfeaMbT
KdV8?modestbranding=1
3-D neurotransmission:
http://www.youtube.com/watch?v=90cj4N
X87Yk
Chemical Synapse
Ion movement
Graded potential
Binding of neurotransmitter
opens ion channels, resulting in
graded potentials.
Copyright © 2010 Pearson Education, Inc.
Figure 11.15a Action potential propagation in unmyelinated and myelinated axons.
Stimulus
Size of voltage
(a) In a bare plasma membrane (without voltage-gated
channels), as on a dendrite, voltage decays because
current leaks across the membrane.
Copyright © 2010 Pearson Education, Inc.
Figure 11.15b Action potential propagation in unmyelinated and myelinated axons.
Stimulus
Voltage-gated
ion channel
(b) In an unmyelinated axon, voltage-gated Na+ and K+
channels regenerate the action potential at each point
along the axon, so voltage does not decay. Conduction
is slow because movements of ions and of the gates
of channel proteins take time and must occur before
voltage regeneration occurs.
Copyright © 2010 Pearson Education, Inc.
Figure 11.15c Action potential propagation in unmyelinated and myelinated axons.
Myelin
sheath
Stimulus
Node of Ranvier
1 mm
Myelin sheath
(c) In a myelinated axon, myelin keeps current in
axons (voltage doesn’t decay much). APs are
generated only in the nodes of Ranvier and appear
to jump rapidly from node to node.
Copyright © 2010 Pearson Education, Inc.
How do drugs affect
neurotransmission?
https://www.youtube.com/watch?v=7VUlKP4
LDyQ