PHS 3105 - Ch 14 (NO Cranial Nerves)

Chapter 14 - The Brain and Cranial Nerves (In depth Cranial Nerves Knowt in a different flashcard set)

Adult Brain

• __% of body’s nervous tissue

• Average weight: __ kg (__ lb)

• “Typical” volume: __ mL

  • Volume range: __ to __ mL

• 97% of body’s nervous tissue

• Average weight: 1.4 kg (3 lb)

• “Typical” volume: 1200 mL

  • Volume range: 750 to 1200 mL

• Brains of males are about 10% larger than those of females

Regions of the brain

1. __

2. __

3. __

4. __

1. Cerebrum

2. Cerebellum

3. Diencephalon

4. Brainstem

Red nucleus (midbrain)

Recieves input from the cerebrum and cerebellum and issues subconsious motor commands.

Cerebellum: Balance

Walking and talking subconsiously

Substantia nigra (midbrain)

Produces dopamine (pleasure) that inhibits activity of the basal nuclei of cerebrum.

Affected by Parkinson’s disease

Cerebrum

• Largest part of adult brain

• Controls sensation and complex movement

• Controls higher mental functions such as conscious thoughts, intellect, memory, etc.

Divided into left and right cerebral hemispheres

• Cerebral cortex: Highly folded superficial layer of gray matter

• Gyri, sulcus, fissures

Structure of the cerebrum (lobes + sulci)

1. __

2. __

3. __

4. __

5. __

6. __

1. Occipital lobe

2. Parietal lobe

3. Central sulcus: Divides parietal lobe from frontal lobe

4. Frontal lobe

5. Lateral sulcus: Divides frontal lobe from temporal lobe

6. Temporal lobe

Not listed: Parieto-occipital sulcus: Divides parietal lobe from occipital lobe

Gyri (cerebrum)

Rounded elevations that increase the surface area

Sulci (cerebrum)

Shallow depressions between gyri

☆ Sulci, sulk, sinking/depressions

Fissures (cerebrum)

Deeper grooves

Cerebellum

Maintain balance and equilibrium of body. conscious and subconscious movements; and perception (coordinates)

• Second-largest part of brain

• Automatic processing and coordinating center (multitask)

• Two hemispheres

  • Covered by gray matter (cerebellar cortex)

    • Cerebellar cortex & cerebellar nuclei control body movement

  • Split by vermis

• Cerebellar peduncles

Cerebellar peduncles (+ 3 peduncles)

Tracts that link the cerebellum to other brain structures

1. Superior cerebellar peduncles: link to midbrain, diencephalon and cerebrum

2. Middle cerebellar peduncles: link to the pons

3. Inferior cerebellar peduncles: link to the medulla oblongata and spinal cord

Ataxia (cerebellum)

Disturbance in musclar coordination caused by damage from trauma or stroke

Alcohol intoxication can cause temporary ataxia

Diencephalon

Integrates sensory information with motor commands at the subconscious level

Contains:

• Epithalamus

• Thalamus

• Hypothalamus

Lateral geniculate body: Receives visual information, sends to visual centers

Medial geniculate body: Receives auditory information, sends to auditory centers

Epithalamus (diencephalon)

Roof of diencephalon, superior to third ventricle

Anterior: Choroid plexus of the lateral ventricles

Posterior: Pineal gland secretes melatonin which regulates day-night cycles (circadian-rhythm) and reproductive function

Thalamus (diencephalon)

Relays and processes sensory information

Anterior: Limbic system controls emotion

Medial: Provides emotional awareness and understanding. Connects hypothalamus to cerebrum

Ventral: Sensory information about touch,(motor) pressure, pain, temperature, and proprioception to cerebral cortex

Hypothalamus (diencephalon)

Controls emotion, autonomic functions, hormone production, and visceral regulation

Infundibulum: Narrow stalk that connects the hypothalamus to the pituitary gland

Secretes ADH (supra-optic nucleus) and oxytocin (periventricular nucleus)

Regulates body temperature (pre-optic area)

Emotional and behavioral drives:

• Feeding center: sensation of hunger

• Thirst center: sensation of thirst

• Satiety center: regulates food intake

• Drives: unfocused “impressions” originating in the hypothalamus

Brainstem

1. __

2. __

3. __

Processes and relays information between the spinal cord and the cerebrum and cerebellum.

Includes:

• Midbrain

• Pons

• Medulla oblongata

Midbrain (brainstem)

Processes visual and auditory information and associated reflexes and helps maintain consciousness

Superior colliculi: Process visual sensations and reflexes in response to visual stimuli

Inferior colliculi: Process auditory sensations and reflexes in response to auditory stimuli

☆ Eyes are slightly superior to ears, visual is superior.

Pons (brainstem)

Contains tracts (collections of CNS axons), relay centers, and nuclei involved in somatic and visceral motor control

Transverse Connects the cerebellum to the brainstem

• Ascending tract: Sensory

• Descending tract: Motor

Medulla oblongata (brainstem)

Relays sensory information to the thalamus and contains centers that regulate autonomic functions, such as heart rate, breathing, and blood pressure.

Cardiovascular centers: Adjust heart rate, peripheral blood flow, and reflex activity

Connects the brain to the spinal cord

Inferior portion has a narrow central canal

Ventricles (4 Ventricles)

Chambers in the brain lined with ependymal cells

• Two lateral ventricles: One in each hemisphere, separated by medial partition

• Third ventricle: In the diencephalon. Communicates with lateral ventricles via an interventricular foramen

• Fourth ventricle: Extends into the medulla oblongata. Joins central canal of spinal cord.

  • Connects with third ventricle via a narrow canal in midbrain called cerebral aqueduct

Label the Ventricular System (Lateral View)

1. __

2. __

3. __

4. __

5. __

1. Lateral ventricles

2. Interventricular foramen

3. Third ventricle

4. Cerebral aqueduct

5. Fourth ventricle

Label the Ventricular System (Anterior View)

1. __

2. __

3. __

4. __

5. __

1. Lateral ventricles

2. Interventricular foramen

3. Third ventricle

4. Cerebral aqueduct

5. Fourth ventricle

How is the brain protected

Physical (3) and Biochemical (1)

Physical protection

• Bones of the skull

• Cranial meninges

• Cerebrospinal fluid

Biochemical protection

• Blood brain barrier

Cranial meninges (three layers)

• Dura mater

• Arachnoid mater

• Pia mater

Continuous with the spinal meninges

Dura mater (cranial meninges)

Outermost meningeal layer

• Outer fibrous layer (periosteal cranial dura)

• Fuest to the periosteum of cranial bones

• Inner fibrous layer (meningeal cranial dura)

Dura folds: Extensions of he meningeal cranial dura into the cranial cavity that stablize and support the brain

Dural venous sinuses: Large veins located within the dural folds. Drains head of used blood

☆ Dura, durable, outermost layer

Dura folds (dura mater)

1. __

2. __

3. __

Dural folds drain cerebrospinal fluid (CSF) and holds the brain in position to protect from damage.

1. Falx cerebri: Projects between the cerebral hemispheres. Contains the superior sagittal sinus and the inferior sagittal sinus

2. Tentorium cerebelli: Separates cerebrum from cerebellum. Contains transverse sinus

3. Flax cerebelli: Divides the cerebellar hemispheres below tentorium cerebelli

Arachnoid mater (cranial meninges)

Middle meningeal layer that resembles a spider web

Attaches to the dura mater

• Subdural space: Narrow gap between dura mater and arachnoid mater that forms as a result of trauma or disease

• Subarachnoid space: Lies between the arachnoid mater and pia mater

Pia mater (cranial meninges)

Innermost meningeal layer which attaches to the surface of the brain

Anchored by astrocytes (form blood brain barrier)

Cerebrospinal fluid (CSF)

Surrounds all exposed surfaces of the CNS

• Supports the brain: the brain floats in CSF inside the cranium

• Cushions brain and spinal cord

• Transports nutrients, chemical messengers, and wastes

CSF cushions brain against sudden jolts and makes it buoyant

Formation of CSF

Choroid plexus: Area in ventricles that secretes (produces) CSF and removes waste from CSF

• Specialized ependymal cells

Circulation of CSF

Circulates from choroid plexus → ventricles → central canal (of spinal cord) → materials diffuse → subarachnoid space → fourth ventricle → circulates subarachnoid space → nutrients brought in, waste products taken out.

Cranial trauma

Head injury resulting from impact with an object

Epidural hemorrhage

Blood is forced between the dura mater and the skul; pressure distorts the brain tissue

Subdural hemorrhage

Bleeding beween the dura mater and the arachnoid mater; less pressure, but still can damage the brain tissue

• More space, takes longer for pressure to build up, less pressure

Blood supply to the brain

Internal carotid arteries and vertebral arteries deliver nurients and oxygen to the brain

Blood removed from the dural venous by the internal jugular veins

Cerebrovascular diseases

Disorders that interfere with blood supply to the brain

Cerebovascular accident (CVA) / Stroke

Two types:

1. __

2. __

☆ Most frequent artery that strokes: __

Stops blood flow to a portion of the brain. Affected neurons begin to die within minutes

1. Hemorrhagic

2. Obstructive

☆ Middle meningeal artery

Hemmorrhagic (CVA)

Quicker onset and severe symptoms

☆ Like a burst of a tire; blood is going to shoot out very suddenly

Obstructive (CVA)

Blockage, blood clot; blood can’t get from one spot to another spot.

Blood-brain barrier (BBB)

A bunch of interconnected capillary epithelial cells tightly wound together that isolates CNS from general circulation and protects the brain.

Astrocytes regulate chemical control in the BBB so not everything can penetrate the brain.

Antibiotics to/for the brain:

• Need to be lipophilic (fat-type) antibiotic and injected directly

Only lipid-soluble compounds can diffuse through BBB. Ex/ Oxygen, CO2, ammonia, steroids, prostaglandins, small alcohols

Break in blood-brain barrier

Around pituitary gland, directly behind your nose.

Label the cranial nerves

I: __

Pons:

II: __

III: __

IV: __

V: __

VI: __

VII: __

Between:

VIII: __

Medulla Oblongata:

IX: __

X: __

XI: __

XII: __

I: Olfactory bulb

Pons:

II: Optic nerve

III: Ocularmotor nerve

IV: Trochlear nerve

V: Trigeminal nerve

VI: Abducens nerve

VII: Facial nerve

Between:

VIII: Vestibucochlear nerve

Medulla Oblongata:

IX: Glossopharyngeal nerve

X: Vagus nerve

XI: Accessory nerve

XII: Hypoglossal nerve

Gracile nucleus and Cuneate nucleus

Pass somatic sensory information to the thalamus.

Somatic sensory: Muscles

Solitary nuclei

Receive visceral sensory information, integrate it, and relay it to autonomic centers.

Visceral sensory: Internal organs

Inferior olivary complex

Relays information to the cerebral cortex about somatic motor commands

Cerebral cortex: Brain

Limbic system

Establishes emotional states. Links conscious functions of the cerebral cortex with the autonomic functions of the brainstem. Memory storage and retrieval.

• Limbic lobe

• Hippocampus: long-term memory

• Amygdaloid body (amygdala): sensory and emotional response

• Fornix

• Hypothalamus

Fornix (limbic system)

Tract of white matter that connects hippocampus with the hypothalamus.

• Anterior nuclei of the thalamus

Primary motor cortex (cerebrum)

Controls voluntary skeletal muscles via somatic motor neurons. Found in precentral gyrus in the frontal lobe

• Pyramidal cells: neurons of primary motor cortex

Primary somatosensory cortex (cerebrum)

Receives somatosensory information for touch, pressure, pain, vibration, and temperature. Found in postcentral gyrus of parietal lobe

Special sensory cortices (cerebrum)

Visual cortex: Visual, Occipital lobe

Auditory cortex: Auditory, Temporal lobe

Olfactory cortex: Smell, Temporal lobe

Gustatory cortex: Taste, Insula (middle of brain)

Wernicke’s area (Cerebrum)

Responsible for language comprehension. Back of temporal lobe.

Coordinates visual and auditory memories

Patients are not aware of their problem. Words these patients using are not real words.

☆ Wernike’s, w, words

Broca’s area (cerebrum)

Motor speech area, responsible for speech production. Front of brain (left cerebral hemisphere)

Regulates patterns of breathing and vocalization

Damage results in:

• Aphasia: inability to speak or read

• Dyslexia: inability to comprehend or use written words

☆ Broca’s, b, broken speech

Hemispheric lateralization

Left cerebral hemisphere: __

Right cerebral hemisphere: __

Left cerebral hemisphere

• Reading, writing, and math

• Speech and language

• Decision making

Right cerebral hemisphere

• Analyzes sensory information: touch, smell, sight, taste

• Recognition of faces and voice inflection

Electrocephalogram (EEG)

• Pet scan or MRI

Alpha waves: Healthy, awake adults at rest with eyes closed

Beta waves: Intense concentration or mentally stressed adults. High-frequency

Theta waves: Children or intensely frustrated adults; may indicate brain disorder

Delta waves: Asleep infants or awake adults with brain damage. Low-frequency

Seizure

A temporal cerebral disorder accompanied changes in the pattern of electrical activity in the brain and by uncontrolled movements and unusual sensations.

☆ SA node - AV node (Heart: lub-dub) Signal stays in AV node for 0.003 miliseconds