A&P Ch. 13

Filum terminale

-"terminal thread" -is a delicate strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris. -extension of pia mater -tail after conus medullaris

Fissure

-Anterior -indent on front -a narrow split or groove that divides an organ such as the brain, lung, or liver into lobes

Reflexes

-Integration is in the spinal cord, not the brain. -Let's the brain 'know' what it did -*Allows for faster response time* -*Reflex arc* -Flexor reflex-Contraction of flexors due to pain receptors stimulated -Uses multiple spinal cord segments Ipsilateral Receptor - pain-receptors Effector - muscle -Crossed extensor reflex Contraction of extensors Gives stability/balance to the flexor reflex Uses multiple spinal cord segments Contralateral - sensory crosses spinal cord to communicate to motor Receptor - pain-receptors Effector - muscle

Reflex arc

-It is a process that bypasses the brain because sending the neurons to the brain takes longer than to the spinal cord. -the nerve pathway involved in a reflex action including at its simplest a sensory nerve and a motor nerve with a synapse between.

Sulcus

-Posterior -indent on back -a groove or fissure, especially a fissure between two convolutions of the brain.

Dorsal horn

-Sensory

Dorsal root

-Sensory -Always goes through here 1st

External Anatomy

-Starts at medulla oblongata to second lumbar vertebra -Cervical and lumbar enlargements -*Conus medullaris* - spinal cord terminates here -*Filum terminale* - extension of pia mater Nerves within the spinal cord are called ganglion Roots - connect spinal nerve to spinal cord Posterior (dorsal) root - sensory Posterior (dorsal) root ganglion - collection of cell bodies Anterior (ventral) root - motor Cauda equina - horse tail - collection of roots

Coccygeal plexus

-Supplies skin of this region

Sacral plexus

-Supplies the buttocks, perineum, and part of the lower limbs. -Nerves: >*Gluteal n.* - gluteus muscles >*Sciatic n.* - tibial + fibular - hamstrings >*Tibial n.* - posterior leg >*Fibular n.* - anterior leg

Cervical plexus

-Supplies the head, neck and diaphragm -Nerve: >*Occipital*- head >*Auricular*- ears >*Ansa cervicalis* - anterior neck muscles >*Supraclavicular*-above >*Phrenic* - diaphragm

Lumbar plexus

-Supply the abdominal wall, external genitalia, and part of the lower limbs. -Nerves: >*Femoral n.* - flexor hip extensor of knee >*Obturator n.* - adductor muscles

Sensory & Motor Tracts

Tracts that carry information to and from the CNS Afferent = blue, efferent = red Naming of tracts is the origin and termination Ex: corticospinal - cortex of brain to spinal cord

Distribution of spinal nerves

Ventral and dorsal roots spinal nerve Spinal nerve rami *Dorsal rami* *Ventral rami* *Meningeal branch* - innervate vertebra and associated structures *Rami communicantes* - ANS

Internal anatomy

White matter Gray matter

Arrangement & CT of Spinal nerves

*Epineurium* -surrounds nerves -outer or above *Fascicle* -contains axons *Perineurium* -surrounds the fascicles -in between or Middle *Endoneurium* -surrounds the individual axons

Branches from anterior rami

*Plexuses* - combination of anterior rami spinal nerves >Cervical >Brachial >Lumbar >Sacral *Intercostal (*Ribs*) nerves* - AKA thoracic nerves

Know the plexuses as well as the nerves (and what they innervate)

*Plexuses* - combination of anterior rami spinal nerves >Cervical >Brachial >Lumbar >Sacral *Intercostal (*Ribs*) nerves* - AKA thoracic nerves

Gray commissure

- connect - contains Central Canal >Filled with CSF

Roots

- connect spinal nerve to spinal cord -Dorsal -Sensory -Afferent

Posterior (dorsal) root ganglion

- is a cluster of nerve cell bodies in a posterior root of a spinal nerve. -contain the cell bodies of sensory neurons (afferent). -collection of cell bodies

Posterior (dorsal) root

- is one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. -Dorsal - sensory

Contralateral

- neurons on opposite sides

Ventral horn

- somatic motor nuclei

Lateral horn

- thoracic and lumbar; -autonomic motor nuclei

Brachial plexus

-Supply the shoulders and upper limbs. -It is divided into: >roots → trunks → divisions → cords → nerves. -Nerves: >*Musculocutaneous n.* - ant arm muscles >*Axillary n.* - deltoid >*Radial n.* - posterior arm >*Median n.* - lateral anterior forearm >*Ulnar n.* - medial anterior forearm >*Pectoral n.* - pectoralis

What is the pathway of the Reflex arc?

-The path taken by the nerve impulses in a reflex is called a reflex arc. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. -Must contain: >Sensory receptor >Sensory neuron >Integration (at the spinal cord) >Motor neuron >Effector (skeletal or smooth/cardiac)

Sensory Tracts

-The spinothalamic tract -(also known as anterolateral system or the ventrolateral system) -is a sensory pathway from the skin to the thalamus. -From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus.

Motor Tracts

-The term pyramidal tracts refers to upper motor neurons that originate in the cerebral cortex and terminate in the spinal cord (corticospinal) or brainstem (corticobulbar).

The spinal cord (and brain)protective layers (wiki)

-are protected by three layers of tissue or membranes called meninges, that surround the canal . >Dura mater- outermost layer -forms a tough protective coating. *Between the dura mater and the surrounding bone of the vertebrae is a space called the epidural space* The epidural space is filled with adipose tissue, and it contains a network of blood vessels. >Arachnoid mater is the middle layer -spiderweb-like appearance. *Between the arachnoid and the underlying pia mater is subarachnoid space* The subarachnoid space contains cerebrospinal fluid (CSF). The medical procedure known as a lumbar puncture (or "spinal tap") involves use of a needle to withdraw cerebrospinal fluid from the subarachnoid space, usually from the lumbar region of the spine. >Pia mater is the innermost protective layer. -very delicate and it is tightly associated with the surface of the spinal cord.

Commissure

-connect each side -a band of nerve tissue connecting the hemispheres of the brain, the two sides of the spinal cord, etc.

Denticulate ligaments

-helps hold the the spinal cord in place - a band of fibrous pia mater extending along the spinal cord on each side between the dorsal and ventral roots

Cauda equina

-is a bundle of spinal nerves and spinal nerve roots -consisting of: the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord. -horse tail -collection of roots

Cerebrospinal fluid (CSF)

-is a clear, colorless body fluid found in the brain and spine. -It is produced in the choroid plexuses of the ventricles of the brain. -It acts as a cushion or buffer for the brain's cortex, providing basic mechanical and immunological protection to the brain inside the skull.

Ganglion

-is a cluster of nerve cell bodies

Spinal cord

-is a long, thin, tubular bundle >of nervous tissue >that support cells >that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column.

Anterior (ventral) root

-is the efferent motor root of a spinal nerve. At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.

Ipsilateral

-neurons on same side

Conus medullaris

-spinal cord stops here -the conical lower extremity of the spinal cord.

Ventral, dorsal and lateral column

-tracts of the CNS Ascending and descending

The paths of the spinal cord.

1. Dorsal root 2. 3 possible paths +White matter via dorsal column to brain +Dorsal horn to white matter to brain -Gray Matter +Dorsal horn to ventral horn [bypass brain] >REFLEX 3. From brain to ventral horn (motor) ->skeletal muscle 4.From brain to lateral horn (auto) -> smooth/cardiac muscle

3 Protective Layers of the Spinal Cord

1. Dura Mater 2. Arachnoid Mater 3. Pia Mater

3 reflexes (Technically 4)

1. Ipsilateral 2. Contralateral 3. Stretch relfex 4. Flexor reflex

Gray Matter within the spinal cord

=in (deep) Gray commissure - connect Central canal - filled with CSF Dorsal horn - sensory Ventral horn - somatic motor nuclei Lateral horn - thoracic and lumbar; autonomic motor nuclei

White Matter within the spinal cord

=outside (superficial) Anterior median fissure & posterior median sulcus Anterior and posterior commissure - connect each side Ventral, dorsal and lateral column - tracts of the CNS Ascending and descending

Stretch relfex

>Contraction due to stretch of muscle >Purpose: to not 'overstretch' our muscles >Excitatory and inhibitory reaction >Ipsilateral >Receptor/effector - muscle >Ex: Patellar reflex or weight lifting

Crossed extensor reflex

>Contraction of extensors >Gives stability/balance to the flexor reflex >Uses multiple spinal cord segments >Contralateral - sensory crosses spinal cord to communicate to motor >Receptor - pain-receptors >Effector - muscle

Flexor reflex

>Contraction of flexors due to pain receptors stimulated >Uses multiple spinal cord segments >Ipsilateral >Receptor - pain-receptors >Effector - muscle

Tendon reflex

>Relaxation due to muscle tension >Feedback mechanism to control muscle tension (allow muscle to relax) >Excitatory and inhibitory reaction >Ipsilateral >Receptor - tendon >Effector - muscle >Ex: Patellar reflex

*Reflex arc must contain:*

>Sensory receptor >Sensory neuron >Integration (at the spinal cord) >Motor neuron >Effector (skeletal or smooth/cardiac)

Spinal Nerves of the internal anatomy

AKA peripheral nerves 31 pairs 8 cervical- C1-C8 12 thoracic- T1-T12 5 lumbar- L1-L5 5 sacral- S1-S5 1 coccygeal

Lateral

Always Motor

Ventral

Always Motor

Dorsal

Always Sensory

Dermatomes

Area of skin that is innervated

All layers of the spinal cord

Meninges 1. *Dura mater* >Superficial >Composed of dense irregular CT >Continuous with the epineurium 2. Subdural Space 3. *Arachnoid mater* 'spider web-like' >Middle >Composed of collagen and elastin 4. Subarchanoid space >CSF 5. *Pia mater* >Innermost >Contain CSF >Composed of this CT, vascular >*Denticulate ligaments* - help suspend the spinal cord

Spinal Nerves of the External Anatom

Roots Posterior (dorsal) root Posterior (dorsal) root ganglion Anterior (ventral) root Cauda equina

What is the purpose of Ipsilateral and Contralateral?

ipsilateral reflex-response happens on the same side of the stimulus contralateral reflex-response happens on the oppiste side of the body

What happens from sensory to movement?

reflexes travel from stimuli through the motor neuron to relay neuron and is send right back through sensory neurons to produce immediate response Stimuli -> sensory Receptor -> sensory neurons -> Spinal cord ->relay neuron ->brain -> interpretation -> back through motor neuron -> response, such as muscle contraction ect.

Meninges

the three membranes (the dura mater, arachnoid, and pia mater) that line the skull and vertebral canal and enclose the brain and spinal cord.