Brain and Cranial Nerves

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96 Terms

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Brain volume

1200 ml (750-2100 ml range)

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Brain Weight

around 3 pounds (1.4 kg)

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How many neurons and connections in brain?

100 Billion neurons, 500 trillion connections

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Female and male differences

Males have greater volume, females have more connections

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Gyri

rounded elevations

<p>rounded elevations </p>
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Sulci

Shallow grooves

<p>Shallow grooves </p>
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Fissues

deeper grooves

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Four “regions” of brain

Cerebrum

Cerebellum

Diencephalon

  • Thalamus

  • hypothalamus

Brainstem

  • Midbrain

  • pons

  • medulla oblongata

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During embryonic development, the CNS develops from

neural tube

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Ventricular system of brain

  • Lateral ventricles (2)

  • Third ventricle

  • fourth ventricle

  • cerebral aqueduct

  • intraventricular foramen

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<p>A</p>

A

lateral ventricles

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<p>B</p>

B

interventricular foramen

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<p>C</p>

C

third ventricle

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<p>D</p>

D

cerebral aqueduct

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<p>E</p>

E

Fourth ventricle

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<p>F</p>

F

central canal

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<p>G</p>

G

Spinal cord

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<p>H</p>

H

Medulla oblongata

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<p>I</p>

I

Pons

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<p>J</p>

J

Cerebral hemispheres

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Ventricles of the brain

  • fluid filled spaces/ openings

  • continuous with spinal cord

  • contain CSF fluid, ependymal cells

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Cerebrospinal Fluid Function

  • support (our brain floats)

  • cushioning (absorbing impact)

  • transport (nutrients, hormones, waste)*

    • still remember that brain is vascularized

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What three structures (aside from scalp and skull) protect the brain?

  • Cranial meninges (DAP)

  • Blood Brain Barrier (BBB)

  • CSF

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CSF produced each day

500 ml/2 cups, but sometimes 150ml every moment

*Replaced every 8 hours

**Extra CSF absorbed into venous circulation (veins)

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<p>1</p>

1

Periosteal cranial dura

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<p>2</p>

2

Dural sinus

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<p>3</p>

3

Meningeal cranial dura

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<p>4</p>

4

Subdural space

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<p>5</p>

5

Arachnoid mater

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<p>6 </p>

6

Dura Mater

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<p>7</p>

7

Subarachnoid space

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<p>8</p>

8

Pia Mater

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<p>9</p>

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Cerebral Cortex

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Dura Mater

  • outermost, fused to periosteum of cranial bones

  • Subdural space (below it)

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Arachnoid Mater

  • “spiderlike”, has subarachnoid space

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Pia Mater

  • anchored by processes of astrocytes, sticks to surface of brain

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Blood Brain Barrier (BBB)

  • formed by capillary endothelial cells connected by tight junctions

  • prevent materials from diffusing between endothelial cells

  • Small capillaries that are 1 cell thick

  • NOT fenestrated (no holes/apertures)

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What glial cell maintains BBB?

  • Astrocytes

    • ends “endfeet” of astrocytes surround blood vessel (capillary) that produces substance, which supports thigh junctions

    • regulates interstitial environment (between tissue)

      • determining ions, neurotransmitters needed for homeostasis, etc….

      • ex. not eating until 12, but brain uses glucose storage while thinking

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What provides nutrients for astrocytes?

Pericytes

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Transport across BBB

  • lipid soluble (Oxygen, alcohol, CO2)

  • lipid based sterol hormones (insulin, leptin, viruses)

  • **NOT glucose, needs active transport

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Circumventricular Organs

  • have fenestrated capillaries

    • Hypothalamus (which secretes neurohormones ADH and Oxytocin)

    • Posterior Pituitary Gland (where ADH and Oxytocin move around)

    • Pineal Gland (melatonin)

    • Choroid Plexus (in each of the ventricles)

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Choroid Plexus

  • network of blood vessels, exchange between blood and CSF takes place here

  • lines all ventricles of brains

<ul><li><p>network of blood vessels, exchange between blood and CSF takes place here</p></li><li><p>lines all ventricles of brains</p></li></ul><p></p>
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Medulla Oblongata

  • Cranial nerves 8-12

  • Three groups of nuclei

    • Reflex center for autonomic activity

    • sensory and motor nuclei of cranial nerves

    • relay stations for sensory, motor pathways

<ul><li><p>Cranial nerves 8-12 </p></li><li><p><strong>Three groups of nuclei</strong></p><ul><li><p>Reflex center for autonomic activity</p></li><li><p>sensory and motor nuclei of cranial nerves</p></li><li><p>relay stations for sensory, motor pathways</p></li></ul><p></p></li></ul><p></p>
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Brainstem

  • processes and relays info from spinal cord to higher brain (cerebellum, cerebrum)

    • two way street (sensory info goes up, motor info goes down)

      • thalamus, pons, medulla*

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Medulla Oblongata Reflex Center (1st nuclei group’s automatic activity)

  • cardiovascular

    • adjust HR, cardiac contractility, peripheral resistance in <3, blood vessels

  • Respiratory Rhythmic

    • Set basic pace for respiration**

      • **pons also regulate breathing

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Reticular Formation (a part of medulla)

  • gray and white matter, relay station

<ul><li><p>gray and white matter, relay station </p></li></ul><p></p>
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Pons

  • Largest part of brainstem, medial to midbrain and medulla oblongata

  • 5-8 cranial nerve, no. 8 is shared

  • also regulates breathing

    • Apneustic and pneumotaxic centers in gray matter region of pons

<ul><li><p>Largest part of brainstem, medial to midbrain and medulla oblongata </p></li><li><p>5-8 cranial nerve, no. 8 is shared </p></li><li><p>also regulates breathing </p><ul><li><p>Apneustic and pneumotaxic centers in gray matter region of pons</p></li></ul></li></ul><p></p>
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Apneustic and pneumotaxic centers

  • respiratory rhythmicity centers, control respiration (shared task between pons and medulla)

<ul><li><p>respiratory rhythmicity centers, control respiration (shared task between pons and medulla)</p></li></ul><p></p>
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Midbrain

  • Most superior

  • cranial nerves 3-4

  • hand eye coordination, connect to cerebellum

  • auditory and visual processing

  • Substantia nigra is here

<ul><li><p>Most superior </p></li><li><p>cranial nerves 3-4 </p></li><li><p>hand eye coordination, connect to cerebellum </p></li><li><p>auditory and visual processing </p></li><li><p><strong>Substantia nigra is here </strong></p></li></ul><p></p>
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Substantia nigra

  • Regulates basal nuclei activity in midbrain

  • dopamine producing nuclei here

  • production of neuromelanin

    • maintain consciousness

  • controls body movements

  • controls learning, mood, judgement decision-making

    • Diminished SN —> Parkinson’s disease

<ul><li><p>Regulates basal nuclei activity in midbrain</p></li><li><p>dopamine producing nuclei here</p></li><li><p>production of neuromelanin</p><ul><li><p><u>maintain consciousness </u></p></li></ul></li><li><p>controls body movements </p></li><li><p>controls learning, mood, judgement decision-making </p><ul><li><p>Diminished SN —&gt; Parkinson’s disease </p></li></ul></li></ul><p></p>
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Cerebellum

  • 10% of brain volume, 50% of total brain neurons found here

  • posterior to brainstem, inferior to cerebrum

  • Rich in Purkinje Cells (branched, dense, highly connected)

    • found in cerebellar cortex

    • axons are myelinated

<ul><li><p>10% of brain volume, 50% of total brain neurons found here </p></li><li><p>posterior to brainstem, inferior to cerebrum </p></li><li><p>Rich in <strong>Purkinje Cells </strong><em>(branched, dense, highly connected)</em></p><ul><li><p>found in cerebellar cortex</p></li><li><p>axons are myelinated </p></li></ul></li></ul><p></p>
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Gray matter of Cerebellum

  • Cerebellar cortex

  • cerebellar nuclei

<ul><li><p>Cerebellar cortex</p></li><li><p>cerebellar nuclei </p></li></ul><p></p>
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White Matter of Cerebellum

  • Arbor Vitae (tree of life striations)

  • cerebellar peduncles

<ul><li><p><strong>Arbor Vitae </strong>(tree of life striations) </p></li></ul><ul><li><p>cerebellar peduncles </p></li></ul><p></p>
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<p>A</p>

A

Anterior

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<p>D</p>

D

Posterior

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<p>B</p>

B

Primary fissure

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<p>C</p>

C

Folia

  • more folia, more neurons

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<p>E</p>

E

Vermis

  • separates cerebellum into 2 lat. hemispheres

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<p>F</p>

F

Intermediary zone

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<p>G</p>

G

Horizontal fissure

  • creates superior and inferior areas

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<p>H</p>

H

Flocconobular lobe

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<p>A</p>

A

Midbrain

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<p>B</p>

B

Choroid plexus

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<p>C</p>

C

Flocculonodular lobe

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<p>D</p>

D

Medulla Oblongata

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<p>E</p>

E

Posterior Lobe

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<p>F</p>

F

Pons

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<p>G</p>

G

White matter/arbor vitae

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<p>1</p>

1

Superior Peduncle

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<p>2</p>

2

Middle peduncle

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<p>3</p>

3

Inferior peduncle

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Cerebellum Functions

  • hand eye coordination (guitar)

  • rehearsing learned movements/ learning

  • balance (muscle “tone”)

    • Coordination, tone, balance

      • relate back to somatic nervous system controlling skeletal muscle

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Spinocerebellar pathways (tracks)

  • cerebellum doesn’t work in isolation

  • afferent/efferent (arrive/sensory and exit/motor)

  • enter and exit through peduncles

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Ataxia

  • disturbance in muscle coordination

  • temporary cause: alcohol

  • slurred speech, awkward gait, trouble with fine motor movements

    • Dysmetria: type of ataxia

      • inability to control distance, speed, range of motion

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Diencephalon (3 areas)

  1. epithalamus

  1. thalamus

  2. hypothalamus

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Epithalamus

  • roof of dienceph, superior to 3rd ventricle

  • anterior side has choroid plexus of 2 lat. ventricles

<ul><li><p>roof of dienceph, superior to 3rd ventricle </p></li><li><p>anterior side has choroid plexus of 2 lat. ventricles </p></li></ul><p></p>
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Pineal Gland

  • near posterior portion of epithalamus

  • melatonin production

<ul><li><p>near posterior portion of epithalamus </p></li><li><p>melatonin production </p></li></ul><p></p>
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Circadian rhythm and melatonin cycle

  • body adjusts

  • can be impacted/rewired with drugs

  • blue light inhibits melatonin prod

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Thalamus

  • major part of diencephalon

  • central relay****

  • made of many nuclei

<ul><li><p>major part of diencephalon </p></li><li><p>central relay****</p></li><li><p>made of many nuclei </p></li></ul><p></p>
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Nuclei is

cluster of nerve cell bodies in CNS

  • analogous to PNS’s ganglia/ganglion

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Hypothalamus

  • floor of diencephalon

  • has mamillary bodies (memory?)

<ul><li><p>floor of diencephalon </p></li><li><p>has mamillary bodies (memory?)</p></li></ul><p></p>
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Funct of Hypothalamus

  • produce and secretes ADH (antidiuretic), oxytocin

    • sends to posterior pituitary gland

  • Thermoregulation

  • “Internal Thermostat”

    • Homeostasis

    • neg. feedback

  • circadian rhythm

  • auto centers: regulating blood pressure and heart rate

  • Subconscious control of skeletal muscle

    • direct motor patterns associated with emotions

  • Emotional, Behavioral drive

    • Feeding, thirst, satiety center

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Limbic (“border”) Center

Emotion Center, basic emotional states

  • works with hypothalamus

  • link conscious funct of cerebrum to automatic functs of brainstem

  • memory, storage, retrieval

<p>Emotion Center, basic emotional states</p><ul><li><p>works with hypothalamus </p></li><li><p><strong>link conscious funct of cerebrum to automatic functs of brainstem </strong></p></li><li><p>memory, storage, retrieval </p></li></ul><p></p>
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Hippocampus

memory

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Amygdala

“Fight or flight response, freeze”

  • interface between limbic system & cerebrum & sensory organs

  • sympathetic NS stimulated (typically)

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Cerebrum

  • Surface a: 2200

  • largest part of brain

  • highest level of thinking

    • somatosensory info

  • cerebral cortex: outermost portion

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What splits the cerebrum into 2 hemispheres?

Longitudinal Fissure

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Basal Nuclei

  • masses of gray matter, UNmyelinated neurons

  • function via feedback loop with cerebral cortex

  • constantly adjusting muscle tone

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Commissural Fibers

White Matter connecting lobes of brain

  • Fibers connecting 2 hemispheres

    • best example of c.fibers is Corpus Callosum

      • C.C. is cut to prevent seizures (epilepsy)

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Frontal Lobe

  • its anterior contains prefrontal cortex (developed by 25, last part to fully develop)

  • motivation, planning, exec. funct, attention and focusing

  • short term mem

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What’s in the frontal lobe?

  • Prefrontal Cortex

  • Precentral gyrus

  • Broca’s area

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Parietal lobe

  • posterior and dorsal to frontal lobe

    • proprioceptive (where body is in space)

    • mechanoreceptive (touch)

  • language processing

  • contains post-central gyrus

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Post central gyrus

  • contains somatosensory cortex (AFFERENT info, goes up to brain to be processed)

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Temporal Lobe

  • Inferior, posterior to frontal lobe

  • Auditory complex (hearing), and some visual input

  • Wernicke’s area

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Wernicke’s area

  • temporal lobe

  • for comprehension of language (written and spoken)

  • unilateral, dominant hemisphere

    • If Rightie, left side of brain

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Occipital Lobe

Vision