Topic 10: CNS structures Flashcards Preview

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Flashcards in Topic 10: CNS structures Deck (104)
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1
Q

Rostral

A

towards the nose

2
Q

Caudal

A

toward the tail

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
4
Q

Spinal cord location

A

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

5
Q

Conus medullaris

A

Inferior end of spinal cord

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

7
Q

Cauda equina

A

Collection of spinal nerve roots in inferior end of vertebral canal

8
Q

Cervical and lumbar enlargements

A

where nerves for upper and lower limbs arise

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
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

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

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

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

14
Q

Fiber classification in white matter:

Ascending fibers

A

Carry sensory information from sensory neurons up to brain

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

16
Q

Fiber classification in white matter:

Commissural fibers

A

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

17
Q

Fiber classification in white matter:

Commissure

A

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

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)

19
Q

Gray matter of spinal cord:

Dorsal horns

A

Posterior arms of H

connected to ventral horns

20
Q

Gray matter of spinal cord:

Ventral horns

A

Anterior arms of H

connected to dorsal horns

21
Q

Gray matter of spinal cord:

Lateral horns

A

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

22
Q

Dorsal root ganglia

A

Outside the spinal cord, where sensory neuron cell bodies reside

23
Q

Dorsal roots

A

Sensory neuron axons reach the spinal cord via the dorsal roots

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

25
Q

Regions of the gray matter of spinal cord

A

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

26
Q

Paralysis

A

Damage to the ventral horn or ventral motor roots destroys the motor neurons and causes paralysis of skeletal muscles served

27
Q

Parathesia

A

Damage to the dorsal horn or sensory neuron cell bodies in dorsal root ganglia can lead to parathesia, loss of sensory function

28
Q

Protection of the spinal cord

A
  1. Vertebrae
  2. Meninges
  3. CSF
29
Q

Meninges

A

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

30
Q

Meninges external to internal

A

Dura mater
Arachnoid mater
Pia mater

31
Q

Meninges and associated spaces

external to internal

A

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

32
Q

Meninges pia mater

A

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

33
Q

Cerebrospinal fluid

A

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
Q

Lumbar puncture

Spinal tap

A

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

35
Q

Brain protection

A

Skull
Meninges
Cerebrospinal fluid
Blood-brain barrier

36
Q

Brain protection:

Two-layered dura mater

A

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

37
Q

Meninges: dura sinuses

A

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
Q

Falx cerebri

A

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

39
Q

Falx cerebelli

A

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
Q

Tentorium cerebelli

A

Almost horizontal sheet lies in the transverse fissure between the cerebrum and cerebellum; encloses transverse sinus

41
Q

Arachnoid villi

Arachnoid granulations

A

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

42
Q

Pia mater of brain

A

Delicate vascularized connective tissue

Clings tightly to surface of brain following contours of the gyri, sulci, and fissures of brain’s surface

43
Q

Meningitis

A

Inflammation of meningeal tissues from infecion

44
Q

Encephalitis

A

Inflammation of brain or spinal cord from infection

45
Q

Brain general facts

A

1500 grams
Intelligence, consciousness, memory, sensory-motor integration, cranial nerves innervate head
Maintains autonomic nervous system and endocrine system

46
Q

Embryonic development of brain: week 4

A

Arises from rostral part of neural tube in, caudal portion becomes spinal cord

PROSENCEPHALON- forebrain
MESENCEPHALON- midbrain
RHOMBENCEPHALON- hindbrain

47
Q

Embryonic development of brain: week 4

A

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

48
Q

Secondary brain vesicles develop into adult brain structures:
Telencephalon

A

Cerebral hemispheres

49
Q

Secondary brain vesicles develop into adult brain structures:
Diencephalon

A

Thalamus, hypothalamus, epithalamus

50
Q

Secondary brain vesicles develop into adult brain structures:
Mesencephalon

A

Midbrain

51
Q

Secondary brain vesicles develop into adult brain structures:
Metencephalon

A

Pons and cerebellum

52
Q

Secondary brain vesicles develop into adult brain structures:
Myelencephalon

A

Medulla oblongata

53
Q

Brain structure from rostral to caudal

A

Cerebrum: two cerebral hemispheres

Diencephalon: thalamus, hypothalamus, epithalamus

Cerebellum

Brain stem: midbrain, pons, medulla oblongata

54
Q

Basic parts and organization of brain

A

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
Q

Ventricles of the brain general information

A

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

56
Q

Ventricles of the brain

A

Telencephalon: lateral ventricles

Diencephalon: 3rd ventricle

Midbrain: cerebral aqueduct

Pons, cerebellum, medulla oblongata: 4th ventricle

57
Q

Paired lateral ventricles

A

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

58
Q

3rd ventricle and cerebral aqueduct

A

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

59
Q

4th ventricle of brain

A

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

60
Q

Choroid plexuses

A

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

61
Q

Components in CSF formed by choroid plexus

A

Glucose
Oxygen
Vitamins
Ions (Na, Cl, Mg)

62
Q

CSF movement

A
  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
63
Q

Hydrocephalus

A

Excessive accumulation of CSF in ventricles and/or subarachnoid space

64
Q

Blood brain barrier

A

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

65
Q

Brainstem from rostral to caudal

A

Midbrain
Pons
Medulla oblongata
Each is about an inch long, making up 2.5% of brain mass together

66
Q

Brain stem functions

A

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

67
Q

Brain stem

Medulla oblongata

A

Conical
Continuous with spinal cord at magnum foramen
Most caudal
Part of 4th ventricle lying dorsal to rostral half of medulla

68
Q

Medulla oblongata
Externally visible landmarks

Inferior cerebellar peduncles

A

Fiber tracts connecting medulla and cerebellum

69
Q

Medulla oblongata
Externally visible landmarks

Olive

A

Contains inferior olivary nucleus

70
Q

Medulla oblongata
Externally visible landmarks

Pyramids of the medulla

A

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

71
Q

Medulla oblongata
Externally visible landmarks

Dessucation of the pyramids

A

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

72
Q

Medulla oblongata

Inferior olivary nucleus

A

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)

73
Q

Reticular formation

A

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
74
Q

Visceral motor nuclei in medulla

A

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

75
Q

Medulla oblongata

Gray matter vs. white matter

A
Gray:
Cranial nerve nuclei: VIII-XII
nucleus cuneatus & nucleus gracilis
Inferior olivary nucleus
Reticular formation nuclei

White:
Pyramidal motor tracts
Inferior cerebellar peduncles

76
Q

Pons of brainstem

A

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

77
Q

Pontine nuclei

A

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

78
Q

Pons

Gray matter vs. white matter

A

Gray matter
Cranial nerve nuclei V, VI, VII
Pontine nuclei
Reticular formation nuclei

White matter
Pyramidal motor tracts
Middle cerebellar peduncles

79
Q

Midbrain of brainstem

A

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

80
Q

Midbrain

Periaqueductal gray matter

A

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

81
Q

Brain nuclei in midbrain:

Corpora quadrigemina

A

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

82
Q

Brain nuclei in midbrain:

Substantia nigra

A

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

83
Q

Brain nuclei in midbrain:

Red nucleus

A

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

84
Q

Cerebellum general facts

A

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)

85
Q

Regions of cerebellar hemispheres

Cortex

A

Outer gray matter

Neuron rich calculator that smooths out body movements

86
Q

Regions of cerebellar hemispheres

Arbor vitae

A

Internal white matter

Rich in axons which carry information to and from cortex

87
Q

Regions of cerebellar hemispheres

Deep cerebellar nuclei

A

Deeply situated gray matter

Gives rise to axons that relay instructions from cerebellar cortex to other parts of the brain

88
Q

How does the body coordinate movements?

A

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

89
Q

Cerebellar peduncles

Superior cerebellar peduncles

A

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

90
Q

Cerebellar peduncles

Middle cerebellar peduncles

A

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

91
Q

Cerebellar peduncles

Inferiror cerebellar peduncles

A

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
Q

Coordinating movement by cerebellum

A
  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
93
Q

Higher cognitive functions of cerebellum

A

Refines movements when learning a new motor skill and establish a motor memory

Participates in cognition of language, problem-solving, task-planning

94
Q

Injury to cerbellum

A

Damage to anterior/posterior lobes:
disorders in coordination

Damage to flocculondular lobe:
disorders in equilibrium

95
Q

Diencephalon

A
Center core of forebrain
Surrounded by cerebral hemispheres
Composed of 3 paired structures:
-Thalamus
-Hypothalamus
-Epithalamus
Border third ventricle
Mostly gray matter
96
Q

Thalamus of diencephalon

A

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

97
Q

Nuclei in thalamus

A

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

98
Q

Hypothalamus of diencephalon general facts

A

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
Q

Sleep-wake cycles

A

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

100
Q

Mammillary bodies

A

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

101
Q

Functions of hypothalamus

A

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

102
Q

Epithalamus of diencephalon

A

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
103
Q

Functions of hypothalamus

A

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
Q

Epithalamus of diencephalon

A

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