A&P: ch 12 CNS Brain,Spinal Cord, Reflexes & Meninges, Ventricle

3 PARTS

Brain Regions and Organization

What are the four major brain regions?

• Cerebral hemispheres

• diencephalon

• brain stem

• cerebellum

Cerebral Hemispheres: Structural Regions

• What is the cerebral cortex?

  • How thick is the cerebral cortex?

• What is internal white matter composed of?

  • What are basal nuclei?

• Outer region of gray matter

  • 2–4 mm thick

• Myelinated nerve tracts

  • Pockets of gray matter located within white matter

Frontal Lobe

• What is the major function of the frontal lobe?

  • What area of the frontal lobe is associated with higher thinking?

• Higher intellectual processes

  • Prefrontal cortex

Primary Motor Cortex

• Where is the primary motor cortex located?

  • What is the function of the primary motor cortex?

• Precentral gyrus of the frontal lobe

  • Precise, skilled voluntary movements

Broca’s Area

• In which hemisphere is Broca’s area usually found?

  • What is the function of Broca’s area?

• What is another name for Broca’s area?

  • When is Broca’s area active?

• Left hemisphere

  • Controls muscles involved in speech

• Motor speech area

  • When planning to speak

Parietal Lobe: Primary Somatosensory Cortex

• Where is the primary somatosensory cortex located?

• What does the primary somatosensory cortex receive input from?

  • What is proprioception?

    • What is an important function of the primary somatosensory cortex?

• Postcentral gyrus of the parietal lobe

• Sensory receptors in skin and proprioceptors in muscles, joints, and tendons

  • Awareness of body position and movement

    • Spatial discrimination

Somatosensory Association Cortex

• Where is the somatosensory association cortex located?

  • What is the function of the somatosensory association cortex?

• Posterior to the primary somatosensory cortex

  • Integrates sensory information and identifies objects by touch

Occipital Lobe: Primary Visual Cortex

1. What is the function of the primary visual cortex?

Visual Association Area

2. What is the function of the visual association area?

1. Receives visual information from the retina

2. Uses previous visual experiences for recognition

Temporal Lobe: Primary Auditory Cortex

• What is the function of the primary auditory cortex?

  • What sound characteristics are interpreted by the primary auditory cortex?

• Receives auditory information from the inner ear

  • Pitch, loudness, and location

Auditory Association Area

1. What is the function of the auditory association area?

Wernicke’s Area

2. What is the function of Wernicke’s area?

1. Stores memory of sounds

2. Understanding speech and choosing words

Basal Nuclei

• What structures make up the basal nuclei?

  • What are the functions of the basal nuclei?

• Caudate nucleus, lentiform nucleus, and amygdala

  • Regulate voluntary motor movements

  • motor skill learning, habits, & inhibition of unwanted movements

Limbic System

• What structures are included in the limbic system?

  • What are the functions of the limbic system?

• Hippocampus and related structures

  • Emotional responses

  • autonomic responses

  • endocrine responses

  • memory

  • reinforcing behavior

Reticular Activating System (RAS)

• What structures form the reticular activating system?

  • What is the function of the reticular activating system?

• Brainstem and thalamus

  • Maintains consciousness

Diencephalon: Thalamus

• What is the function of the thalamus?

  • What does the thalamus contain?

    • How are thalamic nuclei named?

      • Thalamic nuclei project nerve fibers into what structure?

• Integration and relay of sensory and motor information

  • Many nuclei

    • Based on location

      • Specific parts of the cerebrum

Hypothalamus

• What is the hypothalamus the center for?

  • What functions are regulated by the hypothalamus?

    • Why is the hypothalamus called the endocrine master gland?

• Homeostasis

  • Body temperature, osmolarity, and food intake

    • It controls the pituitary gland

• Which parts of the pituitary are controlled by the hypothalamus?

  • What role does the hypothalamus play in the limbic system?

    • What major nervous system center is located in the hypothalamus?

• Anterior and posterior pituitary

  • Emotions

    • Prime integration center for the autonomic nervous system

Pituitary Gland

• What is the function of the anterior pituitary?

  • What is the function of the posterior pituitary?

• Hormone release

  • Neurohormone release

Pineal Gland

• What hormone does the pineal gland release?

• The pineal gland is part of which brain region?

• Melatonin

• Epithalamus

Brain Stem: Cranial Nerves

• How many cranial nerves are associated with the brain stem?

• What information do cranial nerves carry?

  • Which cranial nerves are associated with the midbrain?

    • Which cranial nerves are associated with the pons?

      • Which cranial nerves are associated with the medulla?

• 12 cranial nerves

• Sensory and motor information for the head and neck

  • CN III and IV

    • CN V, VI, VII, and VIII

      • CN IX, X, XI, and XII

Midbrain: Superior Colliculi

• What is the function of the superior colliculi?

  • What movements are coordinated by the superior colliculi?

• Visual reflex center

  • Head and eye movements

Inferior Colliculi

• What is the function of the inferior colliculi?

  • What movements are coordinated by the inferior colliculi?

• Auditory reflex center

  • Movements in response to sound

Pons

• Where is the pons located?

  • What is the function of the pons?

• Between the medulla and midbrain

  • Relay between cerebrum and cerebellum and helps control breathing

Medulla Oblongata

• What involuntary functions are controlled by the medulla oblongata?.

  • What does CVCC stand for?

• Cardiovascular, respiratory, digestive, and upper respiratory functions

  • Cardiovascular control center

Decussation of the Pyramids

What occurs at the decussation of the pyramids?

Crossover of corticospinal nerve tracts

Cerebellum

• What is the cerebellum responsible for?

• What is the cerebellum the second largest structure of?

• What are cerebellar peduncles?

  • What does the superior cerebellar peduncle connect to?

    • What does the middle cerebellar peduncle connect to?

      • What does the inferior cerebellar peduncle connect to?

• Coordination of movement, balance, and posture

• The brain

• Fiber tracts connecting the cerebellum to other CNS structures

  • Thalamus and brainstem

    • Pons

      • Spinal cord

Cerebral White Matter: Association Fibers

1. What do association fibers connect?

Commissural Fibers

2. What is the function of commissural fibers?

Projection Fibers

2. What is the function of projection fibers?

1. Different parts of the same hemisphere

2. Coordinate functions of the two hemispheres

3. Enter or leave the brain from other areas of the body

CNS: Spinal Cord & Reflexes: The Spinal Cord

Spinal Nerves

What happens to spinal nerves before they connect to the spinal cord?

They split into dorsal and ventral roots

Dorsal Root

• What type of information is carried by the dorsal root?

  • What is located in the dorsal root ganglion?

• Sensory (afferent) information

  • Cell bodies of sensory neurons

Ventral Root

What type of information is carried by the ventral root?

Motor (efferent) information

Cross Section of the Spinal Cord: Dorsal Horns

What occurs in the dorsal horns of the spinal cord?

Sensory fibers synapse with interneurons

Ventral Horns

What is located in the ventral horns?

Motor neuron cell bodies

White Matter Columns

What is found in the white matter columns?

Ascending tracts and descending tracts

Ascending Pathways

• What is the function of ascending pathways?

  • Where do first-order neuron cell bodies reside?

  • First-order neurons carry what type of signals?

• Carry sensory (afferent) signals toward the brain

  • In ganglia

  • Afferent signals

• Where are second-order neurons located?

  • Where are third-order neuron cell bodies located?

• In the spinal cord

  • In the thalamus

Descending Pathways

What is the function of descending pathways?

Carry motor information from the brain

• Where are upper motor neurons located?

  • Where are lower motor neurons located?

• Motor cortex and subcortical motor nuclei

  • Ventral horn

Neuronal Integration

What are the five components of a reflex arc?

• Receptor

• sensory neuron

• integration center

• motor neuron

• effector

Reflex Arcs General Reflex Arc

What is a reflex arc?

A rapid automatic response pathway

Components of a Reflex Arc

1. What detects the stimulus in a reflex arc?

2. Which neuron carries signals toward the CNS in a reflex arc?

3. Where does processing occur in a reflex arc?

4. Which neuron carries signals away from the CNS in a reflex arc?

5. What structure performs the response in a reflex arc?

1. Receptor

2. Sensory neuron (afferent)

3. Integration center

4. Motor neuron (efferent)

5. Effector

Monosynaptic Reflexes

• What is a monosynaptic reflex?

• What is the classic example of a monosynaptic reflex?

  • What receptors are involved in monosynaptic reflexes?

  • Does a monosynaptic reflex involve an interneuron?

• A reflex involving one synapse

• Knee-jerk reaction

  • Stretch receptors

  • NO

Monosynaptic Reflex Pathway

What is the pathway of a monosynaptic stretch reflex?

Sensory receptor → sensory neuron → motor neuron → effector organ

Polysynaptic Reflexes

• What is a polysynaptic reflex?

  • What is a common example of a polysynaptic reflex?

    • Does a polysynaptic reflex involve interneurons?

What is the pathway of a polysynaptic withdrawal reflex?

• A reflex involving one or more interneurons

  • Withdrawal reflex

    • Yes

Sensory receptor → sensory neuron → interneuron → motor neuron → effector organ

Neuronal Circuits Diverging Circuit

• What is a diverging circuit?

  • What is a converging circuit?

• Single input with multiple outputs

  • Multiple inputs with a single output

• What is a reverberating circuit?

  • What is serial processing?

• A circuit that repeatedly stimulates itself

  • One-to-one neuronal connections

What is parallel processing?

Simultaneous processing creating multiple perceptions

Brain Support and Protection: Meninges Overview

What are the meninges?

• What are the functions of the meninges?

Three layers of connective tissue surrounding the brain and spinal cord

• Separate the brain from the cranium

• contain blood vessels

• contain/circulate CSF

What are the three meningeal layers from superficial to deep?

• Dura mater

• arachnoid mater

• pia mater

Dura Mater

• What type of tissue forms the dura mater?

  • What are the two layers of the dura mater?

    • What is located between dural layers?

• Thick irregular dense connective tissue

  • Periosteal layer and meningeal layer

    • Dural venous sinuses

Cranial Dural Septa

What are cranial dural septa?

Flat partitions formed by double layers of dura mater

Falx Cerebri

What does the falx cerebri separate?

Left and right cerebral hemispheres

Falx Cerebelli

What does the falx cerebelli separate?

Left and right cerebellar hemispheres

Tentorium Cerebelli

What does the tentorium cerebelli separate?

Cerebellum from the occipital and temporal lobes

Diaphragma Sellae

What is the diaphragma sellae?

Roof over the sella turcica

Potential Spaces

• Why are epidural and subdural spaces called potential spaces?

• What are the two potential spaces associated with the meninges?

• They are not actual spaces unless filled with fluid from injury

• Epidural and subdural spaces

Arachnoid Mater

• What is the arachnoid mater made of?

  • What are arachnoid trabeculae?

• Web of collagen and elastic fibers

  • Web-like fibers of the arachnoid mater

Subarachnoid Space

• Where is the subarachnoid space located?

  • What is found in the subarachnoid space?

• Between the arachnoid mater and pia mater

  • Large blood vessels and CSF

Pia Mater

• What type of tissue forms the pia mater?

  • Is the pia mater heavily vascularized?

    • How closely does the pia mater adhere to nervous tissue?

• Thin layer of areolar tissue

  • Yes

    • Very tightly

Blood-Brain Barrier

• What structures form the blood-brain barrier?

  • What do tight junctions do in the blood-brain barrier?

• Tight junctions, basement membrane, and astrocytes

  • Restrict movement between cells

• What role does the basement membrane play in the blood-brain barrier?

  • What role do astrocytes play in the blood-brain barrier?

• Provides structural support and filtration

  • Help regulate passage of substances

Brain Ventricles: Ventricles Overview

• What are ventricles?

  • What are ventricles continuous with?

• Four chambers filled with CSF

  • Each other and the central canal of the spinal cord

Lateral Ventricles

• Where are the lateral ventricles located?

  • What separates the lateral ventricles?

• Left and right cerebral hemispheres

  • Septum pellucidum

Third Ventricle

• Where is the third ventricle located?

  • What connects the lateral ventricles to the third ventricle?

• Diencephalon

  • Interventricular foramen

Fourth Ventricle

• What is the shape of the fourth ventricle?

  • Where is the fourth ventricle located?

• What connects the third ventricle to the fourth ventricle?

  • What does the fourth ventricle connect to inferiorly?

• Tetrahedral

  • Between the brain stem and cerebellum

• Cerebral aqueduct

  • Central canal of the spinal cord

Cerebrospinal Fluid (CSF): CSF Overview

What is CSF?

• What are the functions of CSF?

Clear fluid circulating through ventricles and around the brain/spinal cord

• Floats the brain

• cushions the CNS

• maintains homeostatic chemical environment

Formation of CSF

• Where is CSF formed?

  • What structures make up the choroid plexus?

• Choroid plexus

  • Ependymal cells and pia mater capillaries

Circulation of CSF

• What structures drain excess CSF?

  • What are arachnoid granulations?

• Arachnoid villi

  • Clusters of arachnoid villi

What is the pathway of CSF circulation?

Lateral ventricles → interventricular foramen → third ventricle → cerebral aqueduct → fourth ventricle → central canal/subarachnoid space → arachnoid villi → venous blood