Anatomy & Physiology Chapter 13 - Brain & Cranial Nerves

Gyri (gyrus)

Folds of the cerebum

Sulci (sulcus)

Shallow depressions of the cerebum

Fissures

Deep groves of the cerebum

Collections of nerve tissue

1. Ganglion

2. Nucleus

3. Nerve

4. Tract

Ganglion

Group of cell bodies in the PNS

Nucleus

Group of cell bodies in the CNS

Nerve

A bundle of axons in the PNS

Tract

A bundle of axons in the CNS

a) ascending tracts

b) descending tracts

Ascending tracts

Go up the spinal cord & carry sensory information

Descending tracts

Go down the spinal cord & carry motor information

Protection of the central nervous system (CNS)

1. Bones

2. Meninges

3. Brain Ventricle

4. Cerebrospinal Fluid

5. Blood-brain barrier (BBB)

Bones (Protection CNS)

Cranium & vertebrae

Meninges (Protection CNS)

3 layers of tough connective tissue coverings around CNS

1. Pia mater (inner layer)

2. Arachnoid mater (middle layer)

3. Dura mater (outer layer)

Dura mater SPACES

1. Subarachnoid space

2. Subdural space

3. Epidural space

Subarachnoid space

1. Space between the arachnoid & pia mater

2. Lumbar puncture is taken here

Subdural space

Thin space beneath dura mater

Epidural space (only around spinal cord)

1. Space between dura mater & vertebral canal

2. Pain medication can be given here

Subdural hematoma

Subarachnoid hemorrage

Bleeding, usually around brain

Meningitis

Inflamation of the meninges due to an infection

Brain Ventricale

Define: Cerebrospinal fluid-filled cavities/spaces within the brain

1. Two lateral ventricles

2. Third ventricle

3. Cerebral aqueduct

4. Fourth ventricle

Two lateral ventricle (Brain)

One in each half of cerebum

Third ventricle (Brain)

Between halves of thalamus

Cerebral aqueduct (Brain)

Connects third and fourth ventricles

Fourth ventricle (Brain)

Between pons & cerebellum

Cerebrospinal Fluid (CSF)

1. Colorless fluid that protects brain & spinal cord

2. Circulates through subarachnoid space, central canal, & ventricles of brain; gradually reabsorbed into blood

Functions of CSF (Cerebrospinal fluid)

1. Buoyancy

2. Protection

3. Eviromental stability

Enviromental stability

1. Exchanges nutrients & wastes

2. Creates optimum chemical environment

CSF (Cerebrospinal fluid) is formed by the __________?

Chorid Plexus

Chorid Plexus

1. Located in the walls of the ventricles

2. Composed of Ependymal cells & blood capillaries

3. Arachnoid villi

Arachnoid villi do what?

Return exess CSF (Cerebrospinal Fluid) to the blood

Hydrocephalus

1. Condition of excessive CSF (Cerebrospinal)

2. Pressure builds up in the ventricles, can damage the brain

Blood-brain barrier (BBB)

1. Protects the brain from harmful substances by preventing many substances in the blood from passing through to brain

2. Formed by astrocytes

Principal Parts of the Brain

1. Cerebrum

2. Diencephalon

a) thalamus & hypothalamus

3. Cerebellum

4. Brainstem

a) medulla, pons, & midbrain

Cerebral Functions

1. Receives sensory information & interprets it

2. Initiates movement

3. Generates thoughts & emotions

4. Stores memories

5. Responsible for personality traits & intelligence

Cerebral cortex

Thin outer layer of gray matter

Longitudinal Fissure

Separates cerebrum into right & left hemispheres (halves)

Corpus callosum

Band of white matter that connects the cerebral hemispheres together

Central sulcus

Separates frontal from parietal lobes

Lateral sulcus

Separates temporal lobes from rest of the cerebrum

Frontal lobe functions

1. Precentral gyrus of frontal lobe - primary motor cortex (voluntary control of skeletal muscle)

2. Broca area - speech; usually in left frontal lobe

a) injuries result in aphasia (inability to speek) or speech difficulties

3. Concentration, decision - making, personality, planning

Parietal lob functions

Postcentral gyrus of parietal lobes - primary somatosensory cortex (sense of touch)

Temporal lobe functions

1. Hearing

2. Smell

Occipital lobe function

Vision

Insula fuction

1. Taste

2. Memory

Wernicke area

Language interpretaton

Association areas

1. Fuction: Integrate and store information

2. Each lobe has one or more association areas

Hemispheric lateralization

1. Left hemisphere

2. Right hemisphere

Left hemisphere controls?

1. Language, math, & reasoning

2. Controls right side of body

Right hemisphere controls?

1. Musial, artistic & spatial skills

2. Controls left side of body

Basal Nuclei (AKA basal ganglia)

1. Function: Influence complex automatic movements, affects short-term memory

2. Damage to basal nuclie

a) tremors in Parkinson's disease

b) muscular rigidity (stiffness) in Parkinson's disease

Parts of the Diencephalon

1. Epithalamus

2. Thalmus

3. Hypothalamus

Epithalamus

Contains pineal gland which produces MELATONIN (regulates sleep-wake cycles)

Thalamus

Main relay station for sensory and motor signals

Hypothalmus

1. Major regulator of homeostasis

2. Functions

a) Controls ANS (Autonomic Nervous System)

b) Produces hormones & controls pituitary gland

c) Controls body tempeture

d) Hunger & thirst centers

e) Controls sleep patterns

Parts of the Brain Stem

1. Midbrain

2. Pons

3. Medulla Oblongata

Parts of Midbrain

1. Cerebral peduncles (anterior)

2. Substantia nigra

3. Superior colliculi

4. Inferior colliculi

Cerebral peduncles (anterior)

Transmit / relay information

Substantia nigra

Controls automatic skeletal muscle movements

Superior colliculi

Visual reflex center

Inferior colliculi

Auditory reflex center

Pons

Helps control breathing & relays information

Medula Oblongata

1. Continuous with spinal cord

2. Contains all ascending (sensory) & descending (motor) tracts

3. Pyramids (2 anterior bulges where motor tracts pass through)

4. Decussaton

Decussation

1. Motor tracts cross over

2. This is why the left side of brain controls the right side of the body (and vice versa)

Functions of the Medulla Oblongata

1. Passes/relays information between brain and spinal cord

2. Cardiac center

a) regulates heart rate & force of contraction

3. Vasomotor center

a) regulates blood pressure

4. Respiratory center

a) regulates respiratory rate

5. Controls centers for vomiting, coughing, sneezing, swallowing

Cerebellum

1. Has 2 lobes or hemispheres

2. Functions (Movement)

a) coordinates movements

b) regulates posture and balance

c) corrects movement errors

d) stores movement patterns

Ataxia

Problems with muscle coordination, slurred speech, & staggering caused by damage to cerebellum (like being drunk)

Functional brain systems

1. Limbic System

2. Reticular Formation

3. Brain Waves

Limbic System Functions

1. Emotions (pain & pleasure center)

2. Memory

3. Smell

Reticular Formation

1. Maintains consciousness & waking up (from sleep)

2. Regulates muscle tone

Brain waves (or patterns)

1. Created by nerve impulses

2. Measured by an EEG (elecroencephalogram)

3. Used to diagnose sleep disorders, brain disorders, brain death

Cranial Nerves

1. 12 pairs of cranial nerves

2. Branch off of the brain & brainstem

3. 3 types of cranial nerves

3 Types of cranial nerves

1. Sensory - receives information (from senses)

2. Motor - causes muscle contraction

3. Mixed - has both sensory & motor functions

CN I - Olfactory nerves

Smell

CN II - Optic nerves

Vison

CN III - Oculomotor nerves

Eye movements

CN IV - Trochlear nerves

Eye movements

CN V - Trigeminal nerves

1. Has 3 branches

2. Major facial nerve

3. Touch, chewing

CN VI - Abducens nerves

Eye movements

CN VII - Facial nerves

Facial expression, taste

CN VIII - Vestibulocochlear nerves

1. Has 2 branches

2. Cochlear branch - hearing

3. Vestibular branch - balance (equilibrium)

CN IX - Glossopharyngeal nerves

Taste, swallowing

CN X - Vagus nerves

Parasympathetic responses

CN XI - (Spinal) Accessory nerves

Head & shoulder movement

CN XII - Hypoglossal nerves

Tongue movement

O,O,O,T,T,A,F,V,G,V,A,H mnemonic 1

Oh (olfactory)

once (optic)

one (oculomotor)

takes (trochlear)

the (trigeminal)

anatomy (abducens)

final (facial)

very (vestibulocochlear)

good (glossopharyngeal)

vacations (vagus)

are (accessory)

heavenly! (hypoglossal)

O,O,O,T,T,A,F,V,G,V,A,H mnemonic 2

Oh (olfactory)

oh (optic)

oh (oculomotor)

to (trochlear)

touch (trigeminal)

and (abducens)

feel (facial)

very (vestibulocochlear)

green (glossophryngeal)

vegetables (vagus)

A (accessory)

H (hypoglossal)

O,O,O, T,T,A,F,V,G,V,A,H mnemonic 3

On (olfactory)

occasion (optic)

our (oculomotor)

trusty (trochlear)

truck (trigeminal)

acts (abducens)

funny, (facial)

very (vestibulocochlear)

good (glossophryngeal)

vehicle (vagus)

any (accessory)

how (hypoglossal)

Interruption of blood flow/oxygen to brain

1. For 1-2 minutes, impairs brain function

2. For 4 or more minutes, causes brain damage/permanent injury or brain death

Traumatic brain injuries/head injuries

1. #1 cause of accidental death in US

2. Two major types

a) Open head injury

b) Closed head injury

Open head injury

Happens when an object (like a bullet or bone) penetrates the brain

Closed head injury

Happens when the head collides with an object (like a windshield)

Head injury can result in

1. Concussion

2. Contusion

3. Contrecoup

4. Laceration

5. Brain edema

6. Hemorrhage and/or hematoma

Concussion

Temporary loss of consciousness; confusion; memory loss

Contusion

Bruising of the brain

Contrecoup

Brain damage on side opposite the trauma

Laceration

Tearing of the brain

Brain edema

Swelling

Hemorrhage and/or hematoma

Bleeding

Spina bifida

Birth defect that results when the caudal portion of the neural tube fails to close

Stroke or Cerebrovascular Accident (CVA)

Blocked/broken blood vessel in the brain (can cause paralysis, brain damage)