Nervous Tissue & Homeostasis excitable characteristic of
nervous tissue allows for generation of nerve impulses (action
potentials) that provide communication & regulation of most
body tissue. together with endocrine system: responsible for
maintaining homeostasis
Slide 3
Differences in Nervous & Endocrine Control of Homeostasis
NERVOUS ENDOCRINE rapid responder action potentials slow, prolonged
response releases hormones
Slide 4
Structures of the Nervous System total mass of 2 kg (~3% of
total body mass) Skull Spinal Cord Spinal Nerves Cranial Nerves
Ganglia Enteric Plexus Special Senses & other Sensory
Receptors
Slide 5
Major Structures of the Nervous System
Slide 6
Functions of the Nervous System 3 basic functions: 1. Sensory
2. Integrative 3. Motor
Slide 7
Sensory Function sensory receptors detect internal &
external stimuli sensory (afferent) neurons carry this sensory
information to spinal cord & brain thru cranial & spinal
nerves
Slide 8
Integrative Function integrate: process nervous system takes
information from sensory neurons & processes that information,
analyzes it, stores some of it & makes decisions for
appropriate responses served by interneurons (connect 1 neuron to
another neuron Perception : conscious awareness of sensory stimuli
occurs in brain
Slide 9
Motor Function served by motor (efferent) neurons carry info
from brain/spinal cord effectors (muscle or gland) thru cranial or
spinal nerves results in muscles contraction or gland
secreting
Slide 10
Quick Quiz What terms are given to neurons that carry input
spinal cord & brain? What terms are given to neurons that carry
output out of the brain & spinal cord?
Slide 11
Organization of the Nervous System
Slide 12
Histology of the Nervous System 2 cell types 1. Neurons 2.
Neuroglia
Slide 13
Neurons nerve cells that possess electrical excitability :
ability to respond to a stimulus & convert it into an action
potential stimulus: any change in environment that is strong enough
to initiate an action potential
Slide 14
Direction Action Potential Travels
Slide 15
Action Potential electrical signal that propagates along
surface of neurolema (membrane) begins & travels due to
movement of ions between interstitial fluid & inside of neuron
thru specific ion channels once begun it travels rapidly @ constant
strength
Slide 16
Parts of a Neuron
Slide 17
Parts of Neuron: Cell Body contains nucleus, cytoplasm, typical
organelles, + Nissl bodies clusters of RER make materials for:
growth of neuron regenerate damaged axons in PNS
Slide 18
Dendrites little trees input portion of neuron usually, short,
tapering, highly branched their cytoplasm contains Nissl bodies,
mitochondria
Slide 19
Axon propagates action potentials another neuron muscle fiber
gland cell
Slide 20
Parts of an Axon joins cell body @ cone-shaped elevation: axon
hillock part of axon closest to hillock = initial segment jct of
axon hillock & initial segment where action potential arises so
is called the trigger zone
Slide 21
Parts of an Axon axoplasm: cytoplasm of an axon axolemma:
plasma membrane of axon axon collaterals: side branches along
length of axon (most @ 90) axon terminals: axon divides into many
fine processes
Slide 22
Synapse site of communication between 2 neurons or between a
neuron & effector cell synaptic end bulbs: tips of some axon
terminals swell into bulb-shaped structures synaptic vesicles:
store neurotransmitter many neurons have >1 neurotransmitter,
each with different effects on postsynaptic cell
Slide 23
Slide 24
Types of Neurons Functional Classification Structural
Classification Sensory Interneurons Motor use # processes extending
from cell body 1. Multipolar neurons 2. Bipolar neurons 3. Unipolar
neur ons
Slide 25
Multipolar Neurons several dendrites with 1 axon includes most
neurons in brain & spinal cord
Slide 26
Bipolar Neuron 1 main dendrite & 1 axon retina, inner ear,
olfactory area of brain
Slide 27
Unipolar Neuron are sensory neurons that begin in embryo as
bipolar during development axon & dendrite fuse then divide
into 2 branches (both have characteristic structure & function
of an axon) 1 branch ends with dendrites (out of CNS) 2 nd branch
ends in axon terminal (in CNS) cell bodies of most found in
ganglia
Slide 28
Unipolar Neuron
Slide 29
Purkinje Cells found in cerebellum
Slide 30
Pyramidal Cells in cerebral cortex of brain
Slide 31
Neuroglia (Glia) ~50% vol of CNS glue do not generate or
propagate action potentials multiply & divide in mature nervous
systems glioma : brain tumors derived from glial cells very
malignant, grow rapidly
Slide 32
Glial Cells of the CNS 1. ASTROCYTES 2. OLIGODENDROCYTES 3.
MICROGLIA 4. EPENDYMAL CELLS
Slide 33
Astrocytes star-shaped largest & most numerous of glial
cells functions: 1. physically support neurons 2. assist in
blood-brain-barrier (bbb) 3. in embryo: regulate growth, migration,
&interconnections between neurons 4. help maintain appropriate
chemical environment for propagation of action potentials
Slide 34
Slide 35
Oligodendrocytes few trees smaller & fewer branches than
astrocytes Functions: 1. form & maintain myelin sheath on axons
in CNS 2. 1 oligo. myelinates many axons
Slide 36
Microglia small cells with slender processes giving off many
spine-like projections function: 1. phagocytes remove cellular
debris made during normal development remove microbes & damaged
nervous tissue
Slide 37
Ependymal Cells single layer of cuboidal to columnar cells
ciliated & have microvilli function: 1. line ventricles of
brain & central canal of spinal cord 2. produce, monitor, &
assist in circulation of cerebrospinal fluid (CSF) 3. form bbb
Slide 38
Slide 39
Neuroglial Cells of the PNS Schwann cells Satellite cells
Slide 40
Schwann Cells functions: 1. myelinate axons in PNS 1 Schwann
cell myelinates 1 axon 2. participate in axon regeneration
Slide 41
Satellite Cells flat cells that surround cell bodies of neurons
in PNS ganglia functions: 1. structural support 2. regulate
exchange of materials between neuronal cell bodies &
interstitial fluid
Slide 42
Myelination myelin sheath: made up of multilayered lipid &
protein (plasma membrane) covering function: 1. electrically
insulates axon 2. increases speed of nerve impulses
Slide 43
Myelinated & Unmyelinated Axons
Slide 44
Nodes of Ranvier gaps in myelin sheath 1 Schwann cell wraps
axon between nodes of Ranvier
Slide 45
Myelin amount increases from birth to maturity infants
responses slower & less coordinated as older child or adult in
part because myelination is a work in progress thru infancy
Slide 46
Slide 47
Demyelination loss of myelin sheath see in disorders: multiple
sclerosis Tay-Sachs side effect of radiation therapy &
chemotherapy
Slide 48
Gray Matter of the Nervous System contains: neuronal cell
bodies dendrites unmyelinated axons axon terminals neuroglia
Slide 49
White Matter of the Nervous System composed of: myelinated
axons