The Brain

1.3.1

Located within the skull

mushroom shaped organ composed of 100 billion neurons and 10-25 trillion neuroglia

weighs 1300 or almost 3lbs

Consists of cerebrum, cerebellum and brainstem

The Spinal Cord

1.3.1

Located within the canal of the vertebral column

Mass of nerve tissue ranging from 42"-45" in adults

Consists of the spinal cord itself, the cauda equina (aka the horsetail) and filum terminale

What are the attributes of the Brain in the CNS?

1.3.2

The portion of the CNS responsible for:

Interpreting sensory impulses

Controlling muscular movement and muscle tone

associating intellectual processes

emotional aspect of behavior

What is the function of the left brain?

1.3.2

Recieves sensory signals from and controsl right side of body.

Receives images from right half of visual field

reasoning

numerical and scientific skills

spoken and written language

ability to use and understand sign language

What is the function of the right brain?

1.3.2

Receives sensory signals from and controls the left side of the body

Receives images from left half of visual field

music and artistic awareness

recognition of faces and emotional content of facial expression

emotional content of language

space and pattern perception

identifying and discriminating among odors

mental imaging of various senses to compare spatial relationships

What is the function of the spinal cord?

1.3.2

Passing of nerve impulses (propagation)

collecting information from external sources for transmission (information intergration)

31 pairs of spinal nerves, emerging at regular intervals

contains distinct bundles of axons called tracts

(ascending tracts = sensory nerves)

(descending tracts = motor nerves)

What is the function of the cerebrosinal fluid?

1.3.2

protecting the brain and spinal cord against injury

transports oxygen, glucose and needed chemicals from blood to neural tissues

continuously circulates through cavities in brain and spinal cord

contains 80 to 150ml(3-5oz) o fluid

What does the body use to protect the brain?

1.3.3

How does the cranium protect the brain?

1.3.3

Bones of the skull that protect the brain, and organs of sight, hearing and balance

Cranial vault - consists of frontal, parietal, temporal, occipital, sphenoid and ethmoid bones

What are the meninges?

1.3.3

Cranial meninges: encircle the brain

Spinal meninges: surrounds the spinal brain

Cranial Meninges continous with the spinal meninges

What do the layers of the meninges consist of?

1.3.3

 Dura Mater(tough mother) - outermost layer composed of strong, white fibrous tissue

Arachnoid(spider membrane) - middle layer contains a large spider's web distribution of blood vessels

Pia Mater(delicate mother) - innermost layer composed of a transparent membrane that adheres to the brain and spinal cord

Subarachnoid space - space between the pia and arachnoid layer containing CSF

How does the cerebrospinal fluid protect the brain and contribute to homeostasis?

1.3.3

Acting as a shock absorber to help protect against trauma (mechanical protection)

Creating an optimal chemical environment for accurate neuronal signaling (chemical protection)

Providing a medium for exchange of nutrients and waste between blood and nervous tissue

how does the blood brain barrier protect the brain?

1.3.3

Specialized brain capillaries and astrocytes

protects brain cells by preventing passage of harmful substances and pathogens from the blood to the cerebrospinal fluid and brain

What substances can cross the blood brain barrier, are allowed to pass at much slower rates and what can't pass?

1.3.3

Substances that cross the barrier are soluble in water or lipids and require active transport

-water: gluclose, amino acids, sodium, nicotine

-lipid: oxygen, carbon dioxide, alcohol, anesthetic agents

substances allowed to pass, but at much slower rates: creatinine, urea, most ions

Substances that cannot pass at all into the brain:

proteins, most antibiotics

What are the principle structures of the CNS

1.3.4

The Brain stem: medulla oblongata, pons, midbrain

Cerebellum

Diencephalon: thalamus, hyperthalamus, epithalamus, subthalamus, circumventrical organs

Cerebrum

What are the principal structures of the Brain Stem

1.3.4

Begins at the Foramen Magnum as a continuation of the spinal cord

Forms inferior part of the brain stem

Pons: Superior to medulla oblongata and anterior to the cerebellum

Midbrain(Mesencephalon): extends from the pons to the diencephalon. Has two portions; anterior and posterior

Substantia Nigra

Reticular Formation

What are the principal structures of the Cerebellum?

1.3.4

Second largest part of the brain

The cerebellar hemisphere

Cerebellar cortex

Arbor Vitae

Cerebellar peduncles

What are the principal structures of the Diencephalon?

1.3.4

Extends from the brain stem to the cerebrum and surrounds the third ventricle.

Thalamus

Hypothalamus

epithalamus

subthalamus

circumventricular organs

What are the principal structures of the Cerebrum?

1.3.4

The cerebral cortex

Gyri or convolutions

Four lobes: Frontal, parietal, temporal, occipital

cerebral white matter

cerebral hemispheres: longitudinal fissure, corpus callosum

basal ganglia

limbic system

What are the characteristics of the medulla oblongata?

1.3.5

What are the characteristics of the pons?

(Brain stem)

1.3.5

Superior to the medulla and anterior to the cerebellum (1.3.4)

A bridge that connects parts of the brain with one another via:

1. Transverse Fibers - connect the right and left sides of the cerebellum

2. Longitudinal fibers - parts of ascending sensory tracts and descending motor tracts

What are the characteristics of the substantia Nigra?

(Midbrain>Brain stem)

1.3.5

Located in midbrain

large, darkly pigmented nuclei

What are the characteristics of the Reticular Formation?

(Midbrain>Brain Stem)

1.3.5

A netlike arrangement of gray and white matter

Located from the spinal cord through the brain stem to the lower diencephalon

Has sensory and motor functions

What is the function of the Medulla Oblongata?

1.3.6

Vital reflex centers of the Medulla

1)Cardiovascular center - regulates the rate and force of heartbeat and the diameter of blood vessels

2)Medullary Rhythmicity area of the respiratory center adjusts the basic rhythm of breathing

3)other nuclei control reflexes for vomiting, coughing and sneezing

4) Pyramids - bulges on the anterior aspect of the medulla, formed by the largest motor tracts that pass from the cerebrum into the spinal cord

-Decussation of pyramids - 90% of the axons cross from left to right and vice-versa

What is the function of the Pons?

(Brain stem)

1.3.6

Contains the:

Pontine Nuclei - sites at which signals for voluntary movements that originate in the cerebral cortex are relayed into the cerebellum

Together with medullary rhythmicity area, the pneumotaxic area and apneustic areas help control breathing

What is the function of the Midbrain?

(Brain stem)

1.3.6

Anterior portion - contains a pair of tracts called cerebral penduncles, which are responsible for conducting nerve impulses from medulla to thalamus and from cerebrum to lower areas

Posterior(called tectum) - Two superior colliculi: serves as the reflex centers for visual activities

Two inferior colliculi: part of the auditory pathway

What is the function of the Substantia Nigra

(Midbrain>brain stem)

1.3.6

Neurons that release dopamine extend from the substantia nigra to basal ganglia and help control subconsious muscle activities.

Deterioration or loss is associated with Parkinsons.

What is the function of the Reticular formation?

(midbrain>brain stem)

1.3.6

Helps regulate muscle tone

the reticular activating system (RAS) helps maintain consciousness and arousal from sleep

Alerts the cortext to incoming sensory signals

What are the characteristics of Cerebellum?

1.3.5

Occupies the inferior/posterior aspects of the cranial cavity

Posterior to the medulla and pons

separated from the cerebrum by the transverse fissure and the tentorium cerebelli

vermis - central constricted area

the cerebral hemisphere

a) left and right "wings"

b)Anterior and Posterior lobes

Cerebellar cortex - Superficial layer of cerebellum gray matter

Arbor Vitae - deeper white matter tracts, have a tree like appearance

Cerebellar penduncles: inferior, middle superior

What are the Cerebellar penduncles?

(cerebellum)

1.3.5

Three paired bundles of fibers that attach the cerebellum to the brain stem:

Inferior cerebellar penduncles - connects the medulla

middle cerebellar penduncles - connects the pons

superior cerebellar penduncles - connects the midbrain

What is the function of the Cerebellum?

1.3.6

Evaluates how well movements intiated by motor areas in the cerebrum are actually carried out

Coordinates subconscious movements of skeletal muscles

Regulates posture and balance

What are the characteristics of the Thalamus?

(Diencephalon)

1.3.5

Intermediate mass: a bridge of gray matter that crosses the third ventricle, joining the right and left halves

What are the characteristics of the Hyopthalamus?

(diencephalon)

1.3.5

Located below the Thalamus

composed of nuclei in four major regions, including the mamillary region and relay stations for reflexes related to the sense of smell

What are the characteristics and functions of the epithalamus?

(Diencephalon)

(1.3.4 -1.3.6)

What are the characteristics of the Subthalamus?

(diencephalon)

1.3.5

Includes tracts and the paired subthalamic nuclei, which connect to motor areas of the cerebrum

Contains the red nucleus and substantia nigra

What are the characteristics of the Circumventricular Organs?

(diencephalon)

1.3.5

Lie in the walls of the 3rd and 4th ventricles

thought to be the sites of entry of HIV into the brain

What is the function of the Thalamus?

(diencephalon)

1.3.6

Major relay station for most sensory impulses that reach the cerebral cortex from the spinal cord, brain stem, and midbrain

Provides crude perception of touch, pressure, pain, and temperature. Includes nuclei involved in movement planning and control

Contributes to motor function by transmitting information from the cerebellum and basal ganglia to the primary motor area of the cerebral cortex

contributes to regulation of autonomic activities

contributes to maintenance of conciousness

What is the function of the hypothalamus?

(diencephalon)

1.3.6

controls many body activities and is one of the major regulators of homeostasis

1) Control of the autonomic nervous system

2) production of hormones

3) regulation of emotion and behavioral patterns

4) regulation of eating and drinking

5)control of body temperature

6)regulation of circadian rhythms and states of consciouness

What is the function of the Subthalamus?

(diencephalon)

1.3.6

What is the function of the circumventricular organs?

(diencephalon)

1.3.6

monitor chemical changes in the blood because they lack the blood brain barrier

coordinate homeostatic activities of the endocrine and nervous systems

What are the characteristics of the Cerebrum?

1.3.5

Seat of intelligence

Forms the bulk of the brain

Gyri or convolutions - folds on the cerebrum

Characteristics of the cerebral cortex?

(cerebrum)

1.3.5

What are the characteristics of the Cerebral hemispheres?

(cerebrum)

1.3.5

Longitudinal Fissure - The most prominent fissure; separates the cerebrum into right and left halves

The hemispheres coordinate the control of ipsilateral motor movement

Corpus Callosum - A large transverse commisure of white matter that connects the hemispheres.

What are the characteristics of the Lobes of Cerebrum(4)

(Cerebrum)

1.3.5

Frontal Lobe:

Central Sulcus(rolando fissure): separates the frontal lobe from the parietal lobe

Lateral cerebral sulcus (Sylvian fissure): separates the frontal lobe from the temporal lobe

Parietal Lobe:

Parieto-occipital sulcus separates the parietal lobe from the occipital lobe

Temporal Lobe: responsible for complex functions such as memory and emotion

Occipital lobe: analysis of visual information for orientation, position and movement.

What are the characteristics of Cerebral white matter?

(cerebrum)

1.3.5 - 1.3.6

Consists of myelinated and unmyelinated axons in three types of tracts:

Association tracts: conduct nerve impulses between gyri in the same hemisphere

commisural tracts: conduct nerve impulses from gyri in one hemisphere to the corresponding gyri in the opposite hemisphere

projection tracts: conduct nerve impulses from the cerebrum to lower parts of the CNS or vice versa.

What are the characteristics of the Basal Ganglia?

(cerebrum)

1.3.5

What are the functions of the cerebral lobes(4)

(Cerebrum)

1.3.6

Frontal Lobe:

Ability to form words and communicate

Ability to express emotions

Parietal Lobe:

Correlation of sensory information into recognizable form

perception of orientation in time and space

parieto-occipital sulcus separates the parietal lobe from the occipital lobe

Temporal lobe: responsible fro complex functions such as memory and emotion

Occipital lobe: analysis of visual information for orientation, position and movement.

What are the function of the basal ganglia?

(Cerebrum)

1.3.6

Helps regulate initiation and termination of movement

Controls subconcious contractions of skeletal muscles

Helps initiate and terminate some cognitive processes

What are the functions of the Limbic system?

(cerebrum)

1.3.6