Unit 6 Neurologic Disease

What systems are main components of the nervous system?

Central and Peripheral nervous system

What does the central nervous system consist of?

Brain and spinal cord

What does the peripheral nervous system consist of?

• Cranial and spinal nerves

• Sensory neurons

• Neuromuscular junctions

What is the brain and what does it do?

It is the communication and control center of the body

• Receives, processes, evaluates input

• Decides which action to be taken

• Initiations response

  • Involuntary action

  • Voluntary actions

  • Reflex activities

What are the involuntary actions for? What is it regulated by?

To maintain homeostasis

• It’s regulated by the autonomic nervous system (ANS)

What are the layers of protection in the brain?

• Meninges

  • Dura mater (Outer layer; closest to the bone)

  • Subdural space

  • Arachnoid (Middle layer)

  • Subarachnoid space (Contains CSF)

  • Pia mater (Adheres to the surface of the brain)

What are ventricles?

Four internal chambers within the brain

Where are the first two lateral ventricles?

There’s one in each cerebral hemisphere

What is the interventricular foramen?

A tiny pore that connects to the third ventricle

Where is the third ventricle located?

It’s in a single narrow media; space beneath corpus callosum

What is the significance in the cerebral aqueduct?

It runs through midbrain and connects third to fourth ventricle

Where is the fourth ventricle located?

Small triangular chamber between pons and cerebellum

• Connects to central canal runs down through spinal cord

Define Choroid plexus

Spongy mass of blood capillaries on the floor of each ventricle

Define Ependyma

Neuroglia that lines the ventricles and covers choroid plexus

• Produces CSF

What does CSF do?

Provides cushion for brain and spinal cord

• Change in characteristics can be a diagnostic tool!

• Flows through ventricles to subarachnoid space

• Equal amounts of CSF need to be produced and reabsorbed to maintain intracranial pressure (ICP)

What are some characteristics of CSF?

• Appearance: Clear and colorless

• Pressure: 9-14 mmHg or 150 mm H2O

• Protein: 15-45 mg/dL

• Glucose: 45-75 mg/dL

• Potassium: 3 mEq/L

• pH: 7.32-7.35

How often is there RBCs and WBCs in CSF?

RBCs: None

WBCs: Occasionally

What does the blood-brain barrier do?

• Limits passage of materials into the brain

• Controls balance of electrolytes, glucose, and proteins in the brain

Can Lipid soluble substances easily pass through the blood-brain barrier?

Yes

Where is the blood brain barrier?

Capillaries in the brain

What does the blood-CSF barrier do? And where is it located?

• Controls constituents of CSF

• Located at choroid plexus

What are the three major divisions of the brain? What does each consist of?

• Forebrain: 2 cerebral hemispheres

• Midbrain: Corpora quadrigemina and cerebral peduncles

• Hindbrain: Cerebellum, pons, and medulla

What does the brainstem consists of?

• Midbrain, medulla, pons

• Connects hemispheres of brain, cerebellum and spinal cord

What is the percentage of the cerebrum?

• 83% of brain volume

• Cerebral hemispheres, gyri and sulci, longitudinal fissure, corpus callosum

How much neurons do the cerebellum contain?

50% of the neurons

• Second largest brain region

• Located in posterior cranial fossa

Function of prefrontal area

Intellectual function and personality

Function of premotor cortex

Skilled movements

Function of motor cortex

Voluntary movements

Function of Broca’s area

Speech

Function of somatosensory area

Sensation (touch, pain)

Function of Visual cortex

Vision

Function of Auditory cortex

Hearing

Function of Olfactory cortex

Smell

Functions of Wernicke’s area

• Comprehension of speech

• Memory

Function of Cerebellum

Body balance and position, coordinated movement

• Receives input from proprioceptors in muscles and joints

• Receives input from visual and vestibular pathways

Function of Medulla Oblongata

• Control and coordination centers for respiration and cardiovascular activity

• - Swallow reflex center, vomiting reflex, cough reflex

• Nuclei of five cranial nerves

Function of Hypothalamus

• Autonomic nervous system

• Link with endocrine system

• Control of body temperature, fluid balance

• Centers for thirst, hunger

• Maintaining homeostasis

• Regulates sleep cycles, stress response, emotional responses, sex drive

Function of Thalamus

Sensory sorting and relay center for incoming sensory impulses

Function of Basal nuclei

Coordination and control of body movement

Function of reticular activating system

Arousal or awareness

Function of Limbic system

Emotional responses

What’s in the cortex?

“Gray matter” —> Nerve cell bodies

What’s in the corpus callosum?

“White matter” —> Myelinated nerve bundles (Connect the hemispheres)

What does the Diencephalon consist of?

• Thalamus

• Hypothalamus

• Epithalamus

What is the midbrain?

Most superior portion of the brain stem

• Reticular formation, reticular-activating system (RAS)

• Network of nuclei and neurons

• Connected to parts of the brain

  • Determines the degree of awareness of the crebral cortex

  • Drugs can affect the activity of the RAS—increasing or decreasing input to cerebral cortex and diencephalon

What is pons?

• Bundles of afferent and efferent fibers

• Bridge between cerebellum and cerebrum

• Several nuclei of cranial nerves

What does the anterior cerebral artery supply?

The frontal lobe

What does the middle cerebral artery supply?

The lateral part of the cerebral hemispheres

What are the Basilar arteries formed by?

Vertebral arteries

• Supplies branches to brainstem and cerebellum

What is the Circle of Willis?

An arrangement formed by anastomoses between the major arteries

• Provided by:

  • Anterior communicating artery between the anterior cerebral arteries

  • Posterior communicating arteries between the middle cerebral and posterior cerebral arteries

What happens with autoregulation in the brain?

• Increased carbon dioxide levels, decreased blood pH, decreased blood pressure—all result in immediate local vasodilation

  • Baroreceptors and chemoreceptors

• Venous blood from brain collects in dural sinuses

  • Drain into the right and left internal jugular veins

What do cranial nerves consists of?

• Motor fibers only

• Sensory fibers only

• Both motor and sensory fibers

What are the 12 Cranial nerves?

1. Olfactory (Sensory fiber): Smell

2. Optic (Sensory): Vision

3. Oculomotor (Motor): Eye movement

4. Trochlear (Motor): Eye movement

5. Trigeminal (BOTH): General sensory

6. Abducens (Motor): Eye movements

7. Facial (BOTH): Special sensory, muscles of facial expression, scalp muscles

8. Vestibulocochlear (Sensory): Hearing and balance

9. Glossopharyngeal (BOTH)

10. Vagus (BOTH)

11. Spinal accessory (Motor)

12. Hypoglossal (Motor): Muscles of tongue

What is the spinal cord protected by?

• Vertebral column

• Meninges

• CSF

What does gray matter consist of?

• Anterior horns

  • Cell bodies of motor neurons

• Posterior horns

  • Interneurons (association neurons)

• Lateral horns

  • Visceral motor neurons