Download Chapter 10-11 PowerPoint Notes

PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter
10
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10-1
Chapter 10
Nervous System I
Purpose To generates and conducts electrical impulses
!!! Coordinates all body systems by !!!
electrochemical current
The structural and functional unit of the
nervous system is a NEURON (nerve cell)
Functions of Nervous System
Sensory Function
• sensory receptors gather
information
• information is carried to the
Central Nervous System (CNS)
Integrative Function
• sensory information used to
create
• sensations
• memory
• thoughts
• decisions
Motor Function
• decisions are acted
upon
• impulses are
carried to effectors
through the
Peripheral Nervous
System (PNS) 10-6
Two Major Systems of the
Nervous System
1. Central Nervous System (CNS)
• brain
• spinal cord
2. Peripheral Nervous System (PNS)
• peripheral nerves (43 nerves)
• cranial nerves (12 pair)
• spinal nerves (31 Pair)
10-1
Two Divisions of Nervous
System
1. Sensory Division
• INPUT INTO CNS (afferent neurons)
•picks up sensory information and delivers
it to the CNS.
2. Motor Division (made up of two divisions)
• OUTPUT FROM CNS to PNS (efferent neurons)
•carries information to muscles and glands
10-4
Two Division of the Motor Division
1.Somatic
– carries information to skeletal muscle.
2. Autonomic (made up of two divisions)
– carries information to smooth muscle,
cardiac muscle, and glands
Two Divisions of the Autonomic Division
1. PARASYMPATHETIC
- Usually promotes those activities associated
with a normal state.
HOMEOSTASIS!!!
2. SYMPATHETIC
- Effects are generally associated with
emergency situations
FIGHT OR FLIGHT!!!
Divisions Nervous System
10-5
Histology of Nervous Tissue
• Two principal cell types
1. Neurons—excitable cells that transmit electrical
signals
2. Neuroglia (glial cells)—supporting cells:
•
•
•
•
•
•
Astrocytes (CNS)
Microglia (CNS)
Ependymal cells (CNS)
Oligodendrocytes (CNS)
Satellite cells (PNS)
Schwann cells (PNS)
Histology of Nervous Tissue
2. Neuroglia (glial cells)—supporting cells:
•
•
•
•
•
•
Astrocytes (CNS)
Microglia (CNS)
Ependymal cells (CNS)
Oligodendrocytes (CNS)
Satellite cells (PNS)
Schwann cells (PNS)
Neuron Structure
10-7
Types of Neurons
Bipolar
• two processes
• eyes, ears, nose
Unipolar
• one process
• ganglia
Multipolar
• many processes
• most neurons of
CNS
10-9
Classification of Neurons
Sensory Neurons
• afferent
• carry impulse to CNS
• most are unipolar
• some are bipolar
Interneurons
• link neurons
• multipolar
• in CNS
Motor Neurons
• multipolar
• carry impulses away
from CNS
• carry impulses to
effectors
10-10
STOP HERE!!!!
Types of Neuroglial Cells
Schwann Cells
• peripheral nervous
system
• myelinating cell
Oligodendrocytes
• CNS
• myelinating cell
Microglia
• CNS
• phagocytic cell
Astrocytes
• CNS
• scar tissue
• mop up excess ions, etc
• induce synapse formation
• connect neurons to blood
vessels
Ependyma
• CNS
• ciliated
• line central canal of spinal cord
• line ventricles of brain 10-11
Types of Neuroglial Cells
10-12
Regeneration of A Nerve Axon
10-13
Resting Membrane Potential
• inside is negative
relative to the outside
• polarized membrane
• due to distribution of
ions
• Na+/K+ pump
10-14
Potential Changes
• at rest membrane is
polarized
• threshold stimulus
reached
• sodium channels
open and membrane
depolarizes
• potassium leaves
cytoplasm and
membrane repolarizes
10-15
Local Potential Changes
• occur on membranes of dendrites and cell bodies
• caused by various stimuli
• chemicals
• temperature changes
• mechanical forces
• if membrane potential becomes more negative, it has
hyperpolarized
• if membrane potential becomes more positive, it has
depolarized
• graded
• summation can lead to threshold stimulus that starts an action
potential
10-16
Action Potentials
• nerve impulse
• occur on axons
• all-or-none
• refractory period
• absolute - time when threshold stimulus does not start another
action potential
• relative – time when stronger threshold stimulus can start
another action potential
10-17
Nerve Impulse (NI)
• The transmission of an action potential along
a neuron.
• NI is an electrical impulse.
• This is similar to a row of dominos (one falls,
they all fall)
• NI begins on a dendrite run towards the cell
body, through the cell body, and then down
the axon
Action Potentials
10-18
Impulse Conduction
10-19
Impulse Conduction
•
The manner in which the NI runs down the neuron.
1. Unmyelinated Neurons – NI must travel the length of
the neuron.
2. Myelinate Neurons – Jump from Node of Ranvier to
Node of Ranvier.
SALTATORY CONDUCTION!!!
*VERY FAST TRANSMISSION*
Saltatory Conduction
10-20
The Synapse
Nerve impulses pass
from neuron to
neuron at:
Synapses – the
junction between two
neurons where a
nerve impulse is
transmitted
10-21
Synaptic Cleft
• Occurs between the
axon of one neuron
and the dendrite of a
second neuron.
NOTE!!!
The two neurons DO
NOT TOUCH!!!
This is called the
synaptic cleft
10-22
Synaptic Potentials
EPSP
• excitatory postsynaptic potential
• graded
• depolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes more
likely
IPSP
• inhibitory postsynaptic potential
• graded
• hyperpolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes less likely
10-23
Summation of
EPSPs and IPSPs
• EPSPs and IPSPs are
added together in a
process called
summation
• More EPSPs lead to
greater probability of
action potential
10-24
Neurotransmitters
10-25
Impulse Processing
Neuronal Pools
• groups of interneurons that make synaptic connections
with each other
• interneurons work together to perform a common
function
• each pool receives input from other neurons
• each pool generates output to other neurons
10-26
Convergence
• neuron receives input from
several neurons
• incoming impulses represent
information from different
types of sensory receptors
• allows nervous system to
collect, process, and respond
to information
• makes it possible for a
neuron to sum impulses from
different sources
10-27
Divergence
• one neuron sends
impulses to several
neurons
• can amplify an
impulse
• impulse from a
single neuron in
CNS may be
amplified to
activate enough
motor units
needed for muscle
contraction
10-28
Clinical Application
Multiple Sclerosis
Symptoms
• blurred vision
• numb legs or arms
• can lead to paralysis
Treatments
• no cure
• bone marrow transplant
• interferon (anti-viral drug)
• hormones
Causes
• myelin destroyed in
various parts of CNS
• hard scars
(scleroses) form
• nerve impulses
blocked
• muscles do not
receive innervation
• may be related to a
virus
10-29