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IB 131 midterm 2 > Topic 10: CNS structures > Flashcards

Topic 10: CNS structures Flashcards

1
Q

Rostral

A

towards the nose

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2
Q

Caudal

A

toward the tail

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3
Q

Spinal cord functions

A
  1. Sensory and motor innervation of body below head
  2. 2 way conduction pathway for signals between the body and brain
  3. Center for reflexes
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4
Q

Spinal cord location

A

Successive vertebral foramina from foramen magnum to L3 in infants and L1/L2 in children and adults

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5
Q

Conus medullaris

A

Inferior end of spinal cord

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6
Q

Filum terminale

A

Long filament of connective tissue extending from the conus medullaris down to coccyx inferiorly anchoring the spinal cord in place

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7
Q

Cauda equina

A

Collection of spinal nerve roots in inferior end of vertebral canal

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8
Q

Cervical and lumbar enlargements

A

where nerves for upper and lower limbs arise

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9
Q

Spinal nerves

A

31 pairs of spinal nerves PNS attach to spinal cord through dorsal and ventral nerve roots and lie in intervertebral foramina

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
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10
Q

Spinal cord segments

A

Indicates the region of spinal cord where nerve fiber emerges. Spinal cord segment T5 emerges above T5 but is located at the level of vertebrae T4; Spinal cord segment S1 is located at the level of vertebrae L1.

Since spinal cord does not extend to the end of the spinal column, the spinal cord segments are located superior to where their corresponding spinal nerves emerge through the intervertebral foramina

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11
Q

Spinal cord deep grooves

A

Spinal cord is wider laterally than anteroposteriorly

Two deep grooves run the length of the cord and partly divide it into the right and left halves:
DORSAL (posterior) MEDIAN SULCUS
the wider VENTRAL (anterior) MEDIAN FISSURE

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12
Q

White matter of spinal cord

A

outer region of spinal cord
composed of mainly myelinated axons as well unmyelinated axons (fibers) which allows communication within the spinal cord and brain

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13
Q

White matter funiculi

A

White matter on each side of the spinal cord is divided into funiculi (long ropes)

Dorsal (posterior) funiculus

Ventral (anterior) funiculus

Lateral funiculus

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14
Q

Fiber classification in white matter:

Ascending fibers

A

Carry sensory information from sensory neurons up to brain

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15
Q

Fiber classification in white matter:

Descending fibers

A

Carry motor information from the brain to the spinal cord to stimulate muscle contraction or gland secretion

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16
Q

Fiber classification in white matter:

Commissural fibers

A

Carry information from one side of the spinal cord to the other

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17
Q

Fiber classification in white matter:

Commissure

A

Bundle of axons that crosses one side of the CNS to the other

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18
Q

Gray matter of spinal cord:

Gray commissure

A

Cross bar of the H

composed of unmyelinated axons and contains the narrow central cavity (central canal)

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19
Q

Gray matter of spinal cord:

Dorsal horns

A

Posterior arms of H

connected to ventral horns

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20
Q

Gray matter of spinal cord:

Ventral horns

A

Anterior arms of H

connected to dorsal horns

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21
Q

Gray matter of spinal cord:

Lateral horns

A

Small lateral columns in the thoracic and superior lumbar segments of spinal cord

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22
Q

Dorsal root ganglia

A

Outside the spinal cord, where sensory neuron cell bodies reside

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23
Q

Dorsal roots

A

Sensory neuron axons reach the spinal cord via the dorsal roots

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24
Q

Ventral and lateral horns of the gray matter in spinal cord

A

Contain cell bodies of motor neurons and interneurons

Motor neurons send their axons out of the spinal cord via the VENTRAL ROOTS to supply muscles and glands

Ventral horns are largest in the cervical and lumbar segments of the cord as they innervate the upper and lower limbs

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25
Regions of the gray matter of spinal cord
Dorsal to ventral: Dorsal sensory half of gray matter SS somatic sensory VS visceral sensory Ventral motor half of gray matter: VM visceral autonomic motor SM somatic motor
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Paralysis
Damage to the ventral horn or ventral motor roots destroys the motor neurons and causes paralysis of skeletal muscles served
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Parathesia
Damage to the dorsal horn or sensory neuron cell bodies in dorsal root ganglia can lead to parathesia, loss of sensory function
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Protection of the spinal cord
1. Vertebrae 2. Meninges 3. CSF
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Meninges
Three connective tissue membranes that lie just external to the brain and spinal cord Cover and protect the CNS Enclose and protect blood vessels that supply CNS Contains the CNS
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Meninges external to internal
Dura mater Arachnoid mater Pia mater
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Meninges and associated spaces | external to internal
Epidural space: fat-rich cushioning space external to dura mater Dura mater: strongest layer of meninges, single leathery layer of dense fibrous tissue surrounding CNS Subdural space: fluid-filled space between dura mater and arachnoid mater Arachnoid mater: layer lies deep to the dura mater Dura and arachnoid extend to level of S2 Subarachnoid space: filled with CNF and large blood vessels that supply the neural tissue; space is spanned by web-like threads that anchor the arachnoid mater to the pia mater Pia mater: innermost layer of meninges
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Meninges pia mater
Innermost later of meninges Clings tightly to the surface of the spinal cord Delicate layer of connective tissue, richly vascularized with small blood vessels Extends to coccyx covering the filum terminale DENTICULATE LIGAMENTS: lateral extensions of pia mater anchor the spinal cord laterally to the dura mater throughout the length of the cord
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Cerebrospinal fluid
Watery fluid that fills the subarachnoid space and hollow cavities of the brain and spinal cord Provides a liquid cushion and buoyancy for spinal cord and brain Nourishes brain and spinal cord Removes wastes produced by neurons Carries chemical signals between parts of the CNS
34
Lumbar puncture | Spinal tap
Adult spinal cord ends at L1-L2, spinal tap must be done below this A needle is inserted between L4-L5 vertebrae into the subarachnoid space to obtain CSF or inject medicine
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Brain protection
Skull Meninges Cerebrospinal fluid Blood-brain barrier
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Brain protection: | Two-layered dura mater
Strongest part of meninges Two-layered sheet of fibrous connective tissue PERIOSTEAL LAYER, outer layer which attached to internal surface of the skull bones MENINGEAL LAYER, deeper layer which forms external covering of brain and continuous with dura mater that surrounds the spinal cord
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Meninges: dura sinuses
Two layers of dura mater are fused except where they separate to enclose the blood-filled sinuses DURAL SINUSES: collect blood from the brain and conduct it to the large internal jugular veins of neck SUPERIOR SAGGITAL SINUS, largest dural sinus and is positioned in the superior midline
38
Falx cerebri
Dura mater extends inward to form flat partitions to subdivide the cranial cavity and stabilize the brain large sickle shaped vertical sheet in the medal plane in the longitudinal fissure between the cerebral hemispheres; attaches anteriorly to crista galli of ethmoid bone
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Falx cerebelli
Dura mater extends inward to form flat partitions to subdivide the cranial cavity and stabilize the brain Vertical partition extends inferiorly from posterior part of falx cerebri and runs along vermis of cerebellum in the posterior cranial fossa
40
Tentorium cerebelli
Almost horizontal sheet lies in the transverse fissure between the cerebrum and cerebellum; encloses transverse sinus
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Arachnoid villi | Arachnoid granulations
Arachnoid mater forms knoblike projections Project through dura mater over the superior part of brain into superior sagittal sinus and other dural sinuses Villi act as valves that allow CSF to pass from subarachnoid space into dural blood sinuses
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Pia mater of brain
Delicate vascularized connective tissue | Clings tightly to surface of brain following contours of the gyri, sulci, and fissures of brain's surface
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Meningitis
Inflammation of meningeal tissues from infecion
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Encephalitis
Inflammation of brain or spinal cord from infection
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Brain general facts
1500 grams Intelligence, consciousness, memory, sensory-motor integration, cranial nerves innervate head Maintains autonomic nervous system and endocrine system
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Embryonic development of brain: week 4
Arises from rostral part of neural tube in, caudal portion becomes spinal cord PROSENCEPHALON- forebrain MESENCEPHALON- midbrain RHOMBENCEPHALON- hindbrain
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Embryonic development of brain: week 4
Primary brain vesicles develop into 5 secondary brain vesicles Prosencephalon (forebrain) divides into TELENCEPHALON and DIENCEPHALON Mesencephalon (midbrain) remains undivided Rhombencephalon (hindbrain) divides into METENCEPHALON and MYELENCEPHALON
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Secondary brain vesicles develop into adult brain structures: Telencephalon
Cerebral hemispheres
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Secondary brain vesicles develop into adult brain structures: Diencephalon
Thalamus, hypothalamus, epithalamus
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Secondary brain vesicles develop into adult brain structures: Mesencephalon
Midbrain
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Secondary brain vesicles develop into adult brain structures: Metencephalon
Pons and cerebellum
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Secondary brain vesicles develop into adult brain structures: Myelencephalon
Medulla oblongata
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Brain structure from rostral to caudal
Cerebrum: two cerebral hemispheres Diencephalon: thalamus, hypothalamus, epithalamus Cerebellum Brain stem: midbrain, pons, medulla oblongata
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Basic parts and organization of brain
Central gray matter contains neuron cell bodies called BRAIN NUCLEI, and interneurons that process info External white matter is rich in interneurons Unlike spinal cord, cerebrum CEREBRAL CORTEX and cerebellum CEREBELLAR CORTEX have additional layer of gray matter called CORTEX external to white matter
55
Ventricles of the brain general information
Expansion of the brain's central cavity, filled with CSF, lined with ependymal cells, continuous with each other and with the central canal of the spinal cord
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Ventricles of the brain
Telencephalon: lateral ventricles Diencephalon: 3rd ventricle Midbrain: cerebral aqueduct Pons, cerebellum, medulla oblongata: 4th ventricle
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Paired lateral ventricles
Located in cerebral hemispheres Horseshoe-shaped from bending of the cerebral hemispheres Each ventricle has anterior horn, posterior horn, and inferior horn Anterior horn of each lateral ventricle is separated by a SEPTUM PELLUCIDUM
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3rd ventricle and cerebral aqueduct
Third ventricle lies in diencephalon Anteriorly, 3rd ventricle is connected with lateral ventricles by interventricular foramina CEREBRAL AQUEDUCT in the midbrain connects 3rd and 4th ventricles
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4th ventricle of brain
Lies in hindbrain brainstem dorsal to pons and superior half of medulla oblongata Caudally, 4th ventricle connects central canal of inferior medulla and spinal cord Three openings in the walls of the 4th ventricle are the PAIRED LATERAL APERATURES in the side walls and the MEDIAN APERATURE in the roof Apertures connect ventricles with the subarachnoid space which allows CSF to fill both ventricles and the subarachnoid space CHOROID PLEXUS lies in roofs of 4th ventricle, 3rd ventricle and lateral ventricles
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Choroid plexuses
Capillary rich membranes located in rood of all 4 brain ventricles Most CSF is formed in choroid plexus Each choroid plexus consists of a know of porous capillaries surrounded by single layer of ependymal cells joined by tight junctions and have cilia CSF continually forms from blood plasma by filtration from porous capillaries and passage through the ependymal cells into the ventricles Waste products move from CSF to capillaries
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Components in CSF formed by choroid plexus
Glucose Oxygen Vitamins Ions (Na, Cl, Mg)
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CSF movement
1. CSF is produced from blood plasma by choroid plexus of each ventricle 2. CSF enters ventricles 3. Most CSF enters subarachnoid space through the lateral and median apertures in walls of 4th ventricle; some CSF enters the central canal of the spinal cord 4. CSF flows through subarachnoid space and bathes outer surface of brain and spinal cord 5. CSF passes through arachnoid villi and is absorbed into the blood through the venous dural sinuses
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Hydrocephalus
Excessive accumulation of CSF in ventricles and/or subarachnoid space
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Blood brain barrier
Tight junctions joins the endothelial cells in the brain capillaries making them the least permeable capillaries in the body Prevents some blood-borne toxins and some drugs from entering the brain Vital nutrients such as O2 pass through and fat soluble molecules (alcohol, nicotine, and anesthetics) pass through
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Brainstem from rostral to caudal
Midbrain Pons Medulla oblongata Each is about an inch long, making up 2.5% of brain mass together
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Brain stem functions
Passage way for all fiber tracts running between the cerebrum and spinal cord Heavily involved with innervation of face and head 9 of 12 cranial nerves are associated with brain stem Generates autonomic behaviors necessary for survival
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Brain stem | Medulla oblongata
Conical Continuous with spinal cord at magnum foramen Most caudal Part of 4th ventricle lying dorsal to rostral half of medulla
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Medulla oblongata Externally visible landmarks Inferior cerebellar peduncles
Fiber tracts connecting medulla and cerebellum
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Medulla oblongata Externally visible landmarks Olive
Contains inferior olivary nucleus
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Medulla oblongata Externally visible landmarks Pyramids of the medulla
2 longitudinal ridges which lie on ventral surface Formed by PYRAMIDAL TRACTS, large fiber tracts that extend through the brainstem and spinal cord carrying voluntary motor output from cerebrum to spinal cord
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Medulla oblongata Externally visible landmarks Dessucation of the pyramids
Crossing over of motor tracts Caudal part of medulla, pyramidal fibers cross over to opposite side of the brain to enable each cerebral hemisphere to control the voluntary movements of the opposite side of the body
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Medulla oblongata | Inferior olivary nucleus
Each olive lies just lateral to a pyramid and contains a brain nucleus called the inferior olivary nucleus which is a large wavy fold of gray matter it acts as a relay station for sensory information traveling to cerebellum especially for PROPRIOCEPTIVE INFORMATION ascending from the spinal cord (sense of relative position of neighboring parts)
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Reticular formation
Loose cluster of brain nuclei that run through the core of the brain stem Stimulate cerebral alertness and regulates muscles Mostly present in medulla 3 columns that extend the length of the brainstem: 1. midline raphe nuclei 2. medial nuclear group 3. lateral nuclear group
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Visceral motor nuclei in medulla
Cardiac center regulates force and rate of heart beat Vasomotor center regulates blood pressure Respiratory center regulates breathing Centers for hiccups, sneezing, swallowing, coughing PART OF RETICULAR FORMATION
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Medulla oblongata | Gray matter vs. white matter
``` Gray: Cranial nerve nuclei: VIII-XII nucleus cuneatus & nucleus gracilis Inferior olivary nucleus Reticular formation nuclei ``` White: Pyramidal motor tracts Inferior cerebellar peduncles
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Pons of brainstem
A bulge in the brainstem between midbrain and medulla oblongata forming a ventral bridge between the two Dorsally, it is separated from the cerebellum by the 4th ventricle Ventral to cranial nerve nuclei lies part of the reticular formation Ventral to the reticular formation lies the thick pyramidal motor tracts descending from the cerebral cortex Interspersed among the fibers of these motor tracts are numerous PONTINE NUCLEI
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Pontine nuclei
Are relay brain nuclei in a path that connects a portion of the cerebral cortex with the cerebellum which contributes to coordination of voluntary movements Pontine nuclei send axons to the cerebellum in thick MIDDLE CEREBELLAR PEDUNCLES
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Pons | Gray matter vs. white matter
Gray matter Cranial nerve nuclei V, VI, VII Pontine nuclei Reticular formation nuclei White matter Pyramidal motor tracts Middle cerebellar peduncles
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Midbrain of brainstem
Most rostra region of brainstem Between pons and diencephalon Central cavity of midbrain: CEREBRAL AQUEDUCT Ventral surface: CEREBRAL PEDUNCLES contain PYRAMIDAL (CORTICOSPINAL) TRACTS descending from the cerebrum to spinal cord; ventral part od each peduncle is called the CRUS CEREBRI Dorsally a PAIR OF SUPERIOR CEREBELLAR PEDUNCLES connect midbrain to cerebellum
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Midbrain | Periaqueductal gray matter
Surrounds cerebral aqueduct Involved in sympathetic (fight/flight) reaction; midbrain link between part of brain that perceives fear and autonomic pathway that triggers the sympathetic reaction Mediates response to visceral pain
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Brain nuclei in midbrain: | Corpora quadrigemina
Brain nuclei make up gray matter that is embedded in midbrain white matter Corpora quadrigemina is largest of these brain nuclei which make up the tectum (roof) of dorsal midbrain and form four bumps on dorsal surface of midbrain Divided into: 2 superior colliculi: nuclei that act in visual reflexes 2 inferior colliculi: nuclei that act in auditory reflexes
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Brain nuclei in midbrain: | Substantia nigra
Gray matter is embedded in midbrain white matter Contain neuronal cell bodies with melanin in band-like distributions Positioned deep to pyramidal tracts of cerebral peduncle Functionally linked to the basal nuclei and deep gray matter od cerebrum Degeneration of neurons in substantia nigra contribute to Parkinson's disease
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Brain nuclei in midbrain: | Red nucleus
Gray matter embedded in midbrain white matter Lies deep to substantia nigra Reddish hue due to rich blood supply presence of iron pigment in neuron cell bodies Associated with cerbellum
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Cerebellum general facts
Dorsal to pons, separated by 4th ventricle 11% of brain mass Smoothes and coordinates body movements directed by other brain regions Helps maintain posture and equilibrium Consists of two cerebellar hemispheres connected medially by the VERMIS Surface folded into ridges called FOLIA separated by grooves called FISSURES Each hemisphere subdivided into: Anterior lobe Posterior lobe Flocculondular lobe (tiny)
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Regions of cerebellar hemispheres | Cortex
Outer gray matter | Neuron rich calculator that smooths out body movements
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Regions of cerebellar hemispheres | Arbor vitae
Internal white matter | Rich in axons which carry information to and from cortex
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Regions of cerebellar hemispheres | Deep cerebellar nuclei
Deeply situated gray matter | Gives rise to axons that relay instructions from cerebellar cortex to other parts of the brain
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How does the body coordinate movements?
Cerebellar cortex receives three types of information: Information on equilibrium: relayed from receptors in inner ear through VESTIBULAR NUCLEI in medulla to FLOCCULONODULAR LOBE Information on current movements of the limbs and trunk: travels from PROPRIOCEPTORS up the spinal cord through OLIVARY NUCLEI in the medulla to the medial portions of anterior and posterior lobes Information from the cerebral cortex: from cerebral cortex through pontine nuclei in the pons to the LATERAL PORTIONS OF ANTERIOR AND POSTERIOR LOBES
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Cerebellar peduncles | Superior cerebellar peduncles
Three thick tracts of nerve fibers connect the cerebellum to the brain stem Connect midbrain and carry instructions away rom cerebellum to the cerebral cortex Fibers to and from the cerebellum are ipsilateral
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Cerebellar peduncles | Middle cerebellar peduncles
Three thick tracts of nerve fibers connect the cerebellum to the brain stem Connect to pons and carry information into the cerebellum from cerebral cortex through pontine nuclei Fibers to and from the cerebellum are ipsilateral
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Cerebellar peduncles | Inferiror cerebellar peduncles
Three thick tracts of nerve fibers connect the cerebellum to the brain stem Arise from medulla and carry fibers from VESTIBULAR NUCLEI (equilibrium) and from spinal cord (proprioception) through olivary neclei in the medulla into the cerebellum Fibers to and from the cerebellum are ipsilateral
92
Coordinating movement by cerebellum
1. Cerebellum receives info on movement from motor cortex of cerebrum 2. Cerebellum compares intended movement with body position 3. Cerebellum sends instructions back to cerebral cortex to continuously coordinate, adjust fine-tune motor commands and sending it to the spinal cord
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Higher cognitive functions of cerebellum
Refines movements when learning a new motor skill and establish a motor memory Participates in cognition of language, problem-solving, task-planning
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Injury to cerbellum
Damage to anterior/posterior lobes: disorders in coordination Damage to flocculondular lobe: disorders in equilibrium
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Diencephalon
``` Center core of forebrain Surrounded by cerebral hemispheres Composed of 3 paired structures: -Thalamus -Hypothalamus -Epithalamus Border third ventricle Mostly gray matter ```
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Thalamus of diencephalon
Form superolateral walls of third ventricle Contains ~12 major brain nuclei each of which send axons to regions of cerebral cortex Thalamic nuclei act as relay stations for incoming sensory images Regions of the body communicating with cerebral cortex relay signals through thalamic nuclei Gateway to cerebral cortex Nuclei organize and amplify or scale down signals
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Nuclei in thalamus
Afferent impulses from all conscious sense except olfaction converge on thalamus and synapse in at least one of its nuclei Ventral posteriolateral nuclei: relay station for sensory information ascending to the primary sensory areas of the cerebral cortex Medial geniculate body receives auditory input Lateral geniculate body receives visual input
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Hypothalamus of diencephalon general facts
Inferior to thalamus Forms inferolateral walls of third ventricle LIES BETWEEN OPTIC CHASM AND POSTEIRO BORDER OF MAMMILLARY BODIES Pituitary gland projects inferiorly from hypothalamus Contains ~12 brain nuclei Main visceral control center of body
99
Sleep-wake cycles
Regulated by hypothalamus SUPRACHIASMATIC NUCLEUS in hypothalamus is body's biological clock regulating the circadian rhythm in response to daylight-dark cycles sensed via the optic nerve PREOPTIC NUCLEUS in hypothalamus responds to signals from suprachiasmatic nucleus to induce sleep
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Mammillary bodies
Mediate arousal from sleep Located on undersurface of brain as part of diencephalon Closely associated with hypothalamus Part of limbic system Act as a relay of impulses coming from the amygdala and the hippocampus
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Functions of hypothalamus
Control endocrine system, autonomic nervous system, Body temperature, hunger, thirst, Feeding-initiating centers are in lateral part of hypothalamus Feeding-inhibition centers are in ventromedial part of hypothalamus Control of emotional responses: pleasure, sex drive, rage Control motivational behavior Formation of memory: brain nucleus in the mammillary body receives abundant inputs from hippocampal formation Sleep
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Epithalamus of diencephalon
Most dorsal part, forming roof of third ventricle One tiny group of brain nuclei Contain PINEAL GLAND - influenced by hypothalamus - secretes melatonin contributing to circadian rhythm
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Functions of hypothalamus
Control endocrine system, autonomic nervous system, Body temperature, hunger, thirst, Feeding-initiating centers are in lateral part of hypothalamus Feeding-inhibition centers are in ventromedial part of hypothalamus Control of emotional responses: pleasure, sex drive, rage Control motivational behavior Formation of memory: brain nucleus in the mammillary body receives abundant inputs from hippocampal formation Sleep
104
Epithalamus of diencephalon
Most dorsal part, forming roof of third ventricle One tiny group of brain nuclei Contain PINEAL GLAND - influenced by hypothalamus - secretes melatonin contributing to circadian rhythm

IB 131 midterm 2 (6 decks)

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