Outline Introductions Syllabus Textbooks etc Gross anatomy of

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: dsteinme@pcc. edu 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 (alpha 1, alpha 2, beta 1, or beta 2), 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– 5 a

Peripheral Distribution of Spinal Nerves • Sensory fibers Figure 13– 7 b

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 L 1 and L 2

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 C 8? ____

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– 5 a

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– 5 b

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