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.
