Nerve tissue File

Nerves mp3
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Test
Muscles of the Forearm: Anterior Compartment
 These muscles are primarily flexors of the wrist
and fingers
Palmar aponeurosis
Flexor retinaculum
Flexor digitorum
superficialis
Flexor carpi ulnaris
Palmaris longus
Flexor carpi radialis
Medial epicondyle
of humerus
Table 10.11.1
Muscles of the Anterior Compartment
 These muscles are the
primary toe extensors
and ankle dorsiflexors
 They include the
tibialis anterior,
extensor digitorum
longus, extensor
hallucis longus, and
fibularis tertius
Tibia
Tibialis anterior
Extensor digitorum longus
Extensor hallucis longus
Fibularis tertius
Superior and inferior
extensor retinacula
 Fill in the blanks.
Muscles of the Forearm: Anterior Compartment
 These muscles are primarily flexors of the wrist
and fingers
Palmar aponeurosis
Flexor retinaculum
Flexor digitorum
superficialis
Flexor carpi ulnaris
Palmaris longus
Flexor carpi radialis
Medial epicondyle
of humerus
Muscles of the Forearm: Anterior Compartment
 These muscles are primarily flexors of the wrist
and fingers
Palmar aponeurosis
And, they all attach to……
Flexor digitorum
superficialis
Flexor carpi ulnaris
Palmaris longus
Flexor carpi radialis
Medial epicondyle
of humerus
Flexor retinaculum
Muscles of the Anterior Compartment
 These muscles are the
primary toe extensors
and ankle dorsiflexors
Tibia
Tibialis anterior
Extensor digitorum longus
Extensor hallucis longus
Fibularis tertius
Superior and inferior
extensor retinacula
Nerves
These four guys and frontgirl Minnie
Satellite create punkrock songs which
are garage-y, fast, loud, and tricky.
Less catchy than what most other folks
would label punk, but still with very
well crafted songs.
Fundamentals of the
Nervous System and
Nervous Tissue
Part A
11
Nervous System
 The master controlling and
communicating system of
the body
 Thoughts, actions,
emotions
 Communicate by
electrical and chemical
signals
 Rapid, specific responses
Nervous System
 Functions
 Sensory input – monitoring stimuli occurring inside
and outside the body
 Integration – interpretation of sensory input
 Motor output – response to stimuli by activating
effector organs
Nervous System
Sensory input
Integration
Motor output
Or,
Nervous System
You see that your shoulder is on fire
You yell, “Ouch”
look for the water
And, throw it on your shoulder
Organization of the Nervous System
 Central nervous system (CNS)
 Brain and spinal cord
 Integration and command center
 Peripheral nervous system (PNS)
 Paired spinal and cranial nerves
 Spinal nerves carry messages to and from the spinal
cord
 Cranial nerves carry messages to and from the brain
Cranial nerves
Peripheral Nervous System (PNS): Two
Functional Divisions
 Sensory (afferent - arriving) division
 Transmits impulses from the receptors to the CNS
 Motor (efferent - exit) division
 Transmits impulses from the CNS to effector
organs
Sensory Division: Two Main Parts
 Sensory (somatic (soma = body)) afferent fibers
 Carry impulses from skin, skeletal muscles, and
joints to the brain
 Visceral afferent fibers
 Transmit impulses from visceral organs to the brain
Motor Division: Two Main Parts
 Somatic nervous system (aka, voluntary NS)
 Conscious control of skeletal muscles
 Autonomic nervous system (ANS) (aka,
INvoluntary NS) (think of it as the automatic NS)
 Regulates smooth muscle, cardiac muscle, and
glands
 Divisions – sympathetic and parasympathetic
Components of nervous system
Histology of Nerve Tissue
 The two principal cell types of the nervous system
are:
 Supporting cells – cells that surround and wrap
neurons (aka = neuroglia or glial cells)
 Neurons – excitable cells that transmit electrical
signals
Supporting Cells: Neuroglia
 The supporting cells (neuroglia or glial cells):
 Provide a supportive scaffolding for neurons
 Segregate and insulate neurons
 Guide young neurons to the proper connections
 Promote health and growth
Neuroglia or glial cells
 CNS
 Astrocytes
 Microglia
 Ependymal cells
 Oligo-dendro-cytes
 PNS
 Satellite cells
 Schwann cells
Astro-cytes
Astrocytes
Most abundant,
versatile, and highly
branched glial cells
They cling to
neurons and their
synaptic endings,
and cover capillaries
Figure 11.3a
Astrocytes
Figure 11.3a
Astrocytes
 Functionally they:
 Support and brace neurons
 Anchor neurons to their nutrient supplies
 Guide migration of young neurons
 Control the chemical environment
Microglia and Ependymal Cells
Microglia – small, ovoid
cells with spiny processes.
Phagocytes that
monitor the health of
neurons (other immune
cells cannot enter CNS)
Ependymal cells – range in
shape from squamous to
columnar
They line the central
cavities of the brain
and spinal column
csf
Figure 11.3b, c
Oligodendrocytes
Oligodendrocytes: branched cells
that wrap CNS nerve fibers
creating an insulated cover
Myelin sheath
Process of
oligodendrocyte
Nerve
fibers
 PNS
 Satellite cells
 Schwann cells
Satellite Cells so named because they circle like
a satellite around a planet
What do you call a glia when it’s happy?
Schwann cells
(forming myelin sheath)
Smyelin = smylin = smiling, get it?
What do you call a group of brains who form a
singing group at school?
A glia club
Neurons (Nerve Cells)
 What do neurons use to talk to each other?
 Billions of cell phones
Neurons (Nerve Cells)
 Structural units of nervous system (billions of ‘em)
 Composed of a body, axon and dendrites
 Long-lived (~100 yrs), amitotic (we know what that
means, right?) and have a high metabolic rate (need
lots of O2 and glucose)
 Their plasma membrane functions in:
 Electrical signaling
 Cell-to-cell signaling during development
Neurons (Nerve Cells)
Dendrites
(receptive
regions)
Cell body
(biosynthetic center
and receptive region)
Nucleolus
Nucleus
Nissl bodies
Axon
(impulse
Impulse
generating
and conducting direction
region)
Axon hillock
Neurilemma
Node of Ranvier
Schwann cell
(one internode)
Terminal
branches
Axon terminals
(secretory
region)
Nerve Cell Body (Perikaryon or Soma)
 Contains the nucleus and a
nucleolus
Dendrites
(receptive
regions)
Cell body
(biosynthetic center
and receptive region)
 Has well-developed Nissl
bodies (rough ER)
 Is the focal point for the
outgrowth of neuronal
processes (embryonic)
 Contains an axon hillock –
cone-shaped area from
which axons arise
Nucleolus
Axon
Nucleus
Nissl bodies
Axon hillock
 Part of the receptive region
Nerve Cell Body (Perikaryon or Soma)
 Has no centrioles (Why not?)
 Which cliche would a neuron not use
 Let’s make like a tree and leave
 Let’s get the flock out of here
 Let’s bounce
 Let’s split
Processes are
 Armlike extensions from the soma (cell body)
 CNS contains cell bodies and processes
 PNS contains chiefly processes (why?)
 There are two types: dendrites and axons
 Bundles of axons are called
 Tracts in the CNS and nerves in the PNS
Processes are axons and dendrites
Dendrites
(receptive
regions)
Axon
Dendrites of Motor Neurons
Dendrites
 Short, tapering, and
diffusely branched
processes
(receptive
regions)
 One neuron usually has
many dendrites, up to
10,000
 They are the receptive, or
input, regions of the neuron
 Convey info toward the cell
Axons: Structure
 Slender processes of uniform diameter arising from the
hillock, carrying information away from the cell
 Long axons are called nerve fibers
 One leads from the big toe up the leg, past the cell body near
the spinal cord, into the cord and up to the brainstem, a couple
meters or more.
 Usually there is only one unbranched axon per neuron
 Axonal terminal – branched terminus of an axon (aka
telodendria)
 ~10,000 or more terminal branches
Axons: Structure
Axon
(impulse
generating
and conducting
region)
Neurilemma
Impulse
direction
Schwann cell
(one internode)
Axon terminals
Node of Ranvier (secretory
region)
Terminal
branches
Axons are the conducting region leading to the secretory region
Aka
axon terminals
synaptic knobs
or boutons
Myelin Sheath
 Whitish, fatty (protein-lipoid), segmented sheath
around most long AXONS
 NEVER found on dendrites
Myelin Sheath and Neurilemma: Formation
 Formed by Schwann cells in the PNS
 Who does this in the CNS?
Oligodendrocytes
 A Schwann cell:
 Envelopes an axon in a trough
 Encloses the axon with its plasma membrane
 Has concentric layers of membrane that make up
the myelin sheath
 Neurilemma – remaining nucleus and cytoplasm of
a Schwann cell
Myelin Sheath and Neurilemma: Formation
Schwann cell
plasma membrane
Schwann cell
cytoplasm
Axon
1
A Schwann cell
envelopes an axon.
Schwann cell
nucleus
2
The Schwann cell then
rotates around the axon,
wrapping its plasma
membrane loosely around
it in successive layers.
Neurilemma
Myelin sheath
(a) Myelination of a nerve
fiber (axon)
3
The Schwann cell
cytoplasm is forced from
between the membranes.
The tight membrane
wrappings surrounding
the axon form the myelin
sheath.
Myelin Sheath and Neurilemma: Formation
Myelin
sheath
Schwann
cell
cytoplasm
Axon
Neurilemma
(b) Cross-sectional view of a myelinated axon
(electron micrograph 24,000X)
Nodes of Ranvier (Neurofibral Nodes)
 Gaps in the myelin sheath between adjacent
Schwann cells
Myelin Sheath
Node of Ranvier
Schwann cell
Neurilemma (one interTerminal
node)
branches
Axon
terminals
(secretory
region)
Unmyelinated Axons
 A Schwann cell surrounds nerve fibers but coiling
does not take place
 Schwann cells partially enclose 15 or more axons
Axons of the CNS
 Both myelinated and unmyelinated fibers are present
 Myelin sheaths are formed by oligodendrocytes
 Nodes of Ranvier are widely spaced
 There is no neurilemma, one oli covers many axons
Regions of the Brain and Spinal Cord
 White matter – dense collections
of myelinated fibers
 Gray matter – mostly soma and
unmyelinated fibers
Neuron Classification
One nerve
Two nerve
Red
nerve
Blue
nerve
Neuron Classification
 Structural:
 Multipolar — three or more processes
 Bipolar — two processes (1 axon and 1 dendrite)
 Unipolar — single, short process
Neuron Classification
 Functional:
 Sensory (afferent) — transmit impulses toward the
CNS
 Motor (efferent) — carry impulses away from the
CNS
 Interneurons (association neurons) — shuttle
signals through CNS pathways
Common as cars
Rare as glass eyes
I feel that these
are just in between
Bad drivers in
California are
as common as
cars
multipolar
neurons
Having a sixth
sense is
as rare as
glass eyes
bipolar cells
I feel that these
are just in between
Neuron animation