Download Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal

Outline
• Introductions
• Syllabus, Textbooks, etc.
• Gross anatomy of sensory and motor
systems
• Reflex anatomy and physiology
• Case of autonomic regulation (handout
to be used throughout term)
Next Time:
• Chapters 13 and 14
• Prepare to answer the following questions:
1. How are somatic reflexes and autonomic
reflexes different? How are they similar?
2. What is the connection between cranial
nerves and reflexes? …between spinal
nerves and reflexes?
Biology 232
Human Anatomy and Physiology II
Dieterich Steinmetz
(503)977-4226
E-mail: [email protected]
Web: http://my.pcc.edu
Lab:
http://www.spot.pcc.edu/anatomy/lab.htm
Separation of Structure and Function
General Organization
of the Nervous System
• Highly organized, very efficient
Figure 13–1
Motor-Sensory Strip of the Cerebral Cortex
Quick Questions
• What is the somatic nervous system?
• What is the autonomic nervous system?
– Examples:
• What are receptor molecules?
– Examples:
• What are ligands?
– Examples:
Quick Answers
• What is the somatic nervous system?
– Voluntarily controllable (eg., skeletal muscle control)
• What is the autonomic nervous system?
– Sympathetic ANS  fight/flight
– Parasympathetic ANS  rest/repose (or rest/digest)
• What are receptor molecules?
– Examples: adrenoceptors (alpha1, alpha2, beta1, or beta2),
cholinergic receptors (muscarinic or nicotinic)
• What are ligands?
– Examples: catecholamines (adrenaline, noradrenaline),
ACh, muscarine, nicotine
Case of the Woman with HT
• Name the two parts of the ANS
• Describe the two major groups of receptors
and their subtypes (and their usual ligands.)
• Distinguish between receptor stimulation
and cell stimulation.
• Explain what “specificity” means when we
are referring to a ligand’s specificity for
receptors.
• Provide a background for studying examples
of somatic and autonomic reflexes.
Specialization of the Human
Nervous System
• The CNS is not homogenous.
• Review
–
–
–
–
Gray matter and white matter
CNS vs. PNS
Brain vs. Spinal Cord
Cranial Nerves vs. Spinal Nerves
Motor-Sensory Strip of the Cerebral Cortex
Motor-Sensory Strip
Somatosensory Map of Postcentral Gyrus
• Relative sizes of
cortical areas
– proportional to number
of sensory receptors
– proportional to the
sensitivity of each part
of the body
• Can be modified with
learning
Primary Motor Cortex
• The precentral gyrus
initiates voluntary
movement.
• Cells are called upper
motor neurons.
• Muscles are
represented unequally
(according to the
number of motor
units)
A Somatic Reflex
Figure 13–14
Sectional Anatomy
of the Spinal Cord
Figure 13–5a
Peripheral Distribution
of Spinal Nerves
• Sensory fibers
Figure 13–7b
5 Steps in a Neural Reflex
Figure 13–14
Video of Human Nervous System
• Meninges
• Gross brain
• 12 cranial nerves ….. Don’t fall asleep!
• Gross spinal cord
• Examples spinal nerves
What are the basic
structural and organizational
characteristics of
the nervous system?
General Organization
of the Nervous System
• Highly organized, very efficient
Figure 13–1
In lab this week:
Spinal Reflexes
• Rapid, automatic, predictable response
triggered to a specific stimulus
• Controlled by spinal cord alone; not
the brain
What are the structures and
functions of the spinal cord?
Spinal Cord: Gross Anatomy
• Note variations
in cross sections.
Figure 13-2
Spinal Cord Protection
the vertebral column, meninges, cerebrospinal fluid,
and vertebral ligaments.
1. dura
2. arachnoid (transparent)
3. cerebral veins in subarachnoid space,
over pia matter
Spinal Cord Enlarged
Coverings of the Spinal Cord
Three “meninges”:
Dura Mater
Arachnoid Mater
Ce re bro spi nal
Pia Mater
spinal cord (or brain)
.
.
.
Flu id
.
.
The Adult Spinal Cord
• About 18 inches (45 cm) long
• 1/2 inch (14 mm) wide
• Ends between vertebrae L1 and L2
Enlargements of the Spinal Cord
• Caused by:
– amount of gray matter in segment
– involvement with sensory and motor
nerves of limbs
• Cervical enlargement:
– nerves of shoulders and upper limbs
• Lumbar enlargement:
– nerves of pelvis and lower limbs
Spinal Cord
• Cervical Enlargement
• Conus Medularis
• Cauda Equina
– pia matter
• Filum Terminale
The Distal End
• Conus medullaris:
– thin, conical spinal cord
below lumbar enlargement
• Filum terminale:
– thin thread of fibrous tissue
at end of conus medullaris
• Cauda equina:
– nerve roots extending
below conus medullaris
31 Spinal Cord
Segments
• Based on vertebrae
where spinal
nerves originate
• Relationships of
segments to
vertebrae change
with age because
spine grows longer
than spinal cord.
Naming Spinal Nerves
• Superior SEVEN spinal nerves:
– are named for #___ inferior vertebra
• All other nerves:
– are named for superior vertebra
• Where is spinal nerve C8? ________
Roots
• 2 branches of spinal nerves:
– ventral root:
• contains axons of motor neurons
– dorsal root:
• contains axons of sensory neurons
• Dorsal root ganglia:
– contain cell bodies of sensory neurons
White Matter of the Spinal Cord
Dorsal
Ventral
• Anterior median “fissure” is clearer than the
Posterior median “sulcus”
What are the structures and
functions of the three
meningeal layers that surround
the central nervous system?
Spinal Meninges
Figure 13–3
Inter-Layer Spaces
• Subdural space:
– between arachnoid mater and dura mater
• Subarachnoid space:
– between arachnoid mater and pia mater
– contains collagen/elastin fiber network
(arachnoid trabeculae attach to arachnoid
membrane of arachnoid mater)
– filled with cerebrospinal fluid (CSF)
Cerebrospinal Fluid (CSF)
• Is found in subarachnoid space
• Carries dissolved gases, nutrients, and
wastes
• Spinal tap:
– withdraws CSF
The Spinal Cord
Figure 13–4
Gray Matter
–The amount of ventral gray
matter at a given level of the
spinal cord is proportional to
the amount of skeletal muscle
innervated.
Gray Matter of the Spinal Cord
Note: colors in
reverse due to
staining of tissue
(common stains)
What are the roles of
white matter and gray matter
in processing and relaying
sensory information and
motor commands?
Sectional Anatomy
of the Spinal Cord
Figure 13–5a
Back
Front
Spinal Cord
Ventral Roots
(Motor)
Dorsal Roots
(Sensory)
Spinal Nerve
(this is where sensory and motor mix)
Dorsal
Ramus
(mixed)
Ventral
Ramus
(mixed)
Nerve Plexuses
Rami
communicantes
(mixed)
Sympathetic ganglia
Sectional Anatomy
of the Spinal Cord
Figure 13–5b
Nuclei
• Nuclei:
– functional groups of cell bodies
• Sensory nuclei:
– dorsal (posterior)
– connect to peripheral receptors
• Motor nuclei:
– ventral (anterior)
– connect to peripheral effectors
Tracts
• Tracts or fasciculi:
– in white columns
– bundles of axons
– relay same information in same direction
• Ascending tracts:
– carry information to brain
• Descending tracts:
– carry motor commands to spinal cord
Descending
Motor Tracts
• Corticospinal
(Pyramidal) Tract:
Carry motor signals
from the primary
motor cortex of the
brain to the skeletal
muscles of the body
Descending Motor Tracts
• Medial Pathways (vestibulospinal,
tectospinal, reticulospinal):
– muscle tone and gross movements of the neck,
trunk and proximal limb muscles
• Lateral Pathway (rubrospinal tract):
– muscle tone and precise movements of the
distal parts of the limbs.
• Anterior Spinothalamic
Tract:
– crude touch and
pressure
– sensations from the
body to
the thalamus
• Lateral Spinothalamic
Tract:
– pain and temperature
sensations from the
body to the thalamus
Ascending Sensory
Tracts
Ascending Sensory Tracts
• Posterior columns
(gracile fasciculus and
cuneate fasciculus)
– fine touch, vibration,
pressure and
proprioception from the
body to the thalamus
KEY CONCEPT (1 of 3)
• Spinal cord has a narrow central canal
– surrounded by gray matter
– containing sensory and motor nuclei
• Sensory nuclei are dorsal
• Motor nuclei are ventral
KEY CONCEPT (2 of 3)
• Gray matter:
– is covered by a thick layer of white matter
• White matter:
– consists of ascending and descending
axons
– organized in columns
– containing axon bundles with specific
functions
KEY CONCEPT (3 of 3)
• Spinal cord is so highly organized:
– it is possible to predict results of injuries
to specific areas
More on this later…
continues with part 2