a&p: brain and cranial nerves

gray matter

the seat of neurosomas, dendrites, and synapses

• Forms surface layer over cerebrum and cerebellum

• Forms nuclei deep with brain

little myelin

Gray matter is dull in color due to what?

white matter

Bundles of axons

Where white matter

Lies deep to cortical gray matter, opposite relationship in the spinal cord

• Composed of tracts, or bundle of axons that connect one part of the brain to another and to the spinal cord

White matter has a pearly white color from what?

myelin around nerve fibers

ventricles of the brain

four internal chambers within brain

Lateral Ventricles

• two; one in each cerebral hemisphere

• Interventricular foramen- tiny pore that connects to third ventricle

Third ventricle

Narrow medial space beneath corpus callosum

• Cerebral aqueduct runs through midbrain and connects third to fourth ventricle

Fourth ventricle

small triangular chamber between pons and cerebellum

• Connects to central canal that runs through spinal cord

choroid plexus

spongy mass of blood capillaries on the floor of each ventricle

Ependymal

type of neuroglia that lines ventricles and covers choroid plexus

• Produces cerebrospinal fluid

Cerebrospinal fluid (CSF)

clear, colorless liquid that fills the ventricles and canals of CNS

What initiates the production of cerebrospinal fluid (CSF)?

Filtration of blood plasma through capillaries of the brain

What type of cells modify the filtrate to produce cerebrospinal fluid?

Ependymal cells

Functions of CSF?

buoyancy, protection, and chemical stability

Buoyancy

This function of the CSF allows brain to attain considerable size without being impaired by its own weight.

• If it rested heavily on floor of cranium, the pressure would do what to the nervous tissue would kill it

protection

Protects the brain from striking the cranium when the head is jolted

• shaken child syndrome and concussions do occur from severe jolting

chemical stability

flow of CSF rinses away metabolic wastes from nervous tissue and homeostatically regulates its chemical environment

Brain is only ___% of adult body weight, but receives ___% of the blood

2%; 15% (750mL/min)

Neurons have a high demand for what?

ATP

Because of neurons high demand for ATP they have a constant...

blood supply to provide oxygen and glucose

A 10-second interruption of blood flow may cause?

loss of consciousness

A 1 to 2 minute interruption can cause?

significant impairment of neural function

Going 4 minutes without blood causes?

irreversible brain damage

brain barrier system

regulates what substances can get from bloodstream into tissue fluid of the brain

• blood can contain harmful agents

in the brain barrier system two points of entry must be guarded by?

Blood capillaries throughout the brain tissue

and capillaries of the choroid plexus.

Blood-brain barrier

protects blood capillaries throughout brain tissue

blood-brain barrier

Consists of tight junctions between endothelial cells that form the capillary walls

perivascular feet

In the blood-brain barrier astrocytes reach out and contact capillaries with their what?

through

Anything leaving the blood must pass _________ the cells, and not between them

passing to the brain tissue while allowing necessary ones to pass

in the blood-brain barrier endothelial cells can exclude harmful substances from what?

Blood-CSF barrier

protects brain at the choroid plexus

blood-CSF barrier

Forms tight junctions between the ependymal cells and tight junctions are absent from ependymal cells elsewhere

blood-CSF barrier

Tight junctions are important to allow exchange between brain tissue and CSF in what barrier?

water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics

The brain barrier system is highly permeable to what substances?

sodium, potassium, chloride, and the waste products urea and creatinine

What substances is the brain barrier system slightly permeable to?

medications such as antibiotics and cancer drugs

The brain barrier system (BBS) can be an obstacle for delivering what?

pathogens to enter brain tissue

Trauma and inflammation can damage BBS and can allow what?

Circumventricular organs (CVOs)

places in the third and fourth ventricles where the barrier is absent

Brain

in Circumventricular organs (CVOs) blood has direct access to the...

fluctuations in blood glucose, pH, osmolarity, and other variables

Circumventricular organs (CVOs) enables the brain to monitor and respond to what?

human immunodeficiency virus (HIV)

CVOs afford a route for invasion by what virus?

the reticular formation

Loose web of gray matter that runs vertically through all levels of the brainstem

the reticular formation

Occupies space between white fiber tracts and brainstem nuclei

reticular formation

Has connections with many areas of cerebrum with more than 100 small neural networks without distinct boundaries

somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation

functions of networks

Adjust muscle tension to maintain tone, balance, and posture, especially during body movements.

What is the role of somatic motor control in muscle tension?

Relay signals from eyes and ears to cerebellum.

What type of signals does somatic motor control relay to the cerebellum?

Integrate visual, auditory, balance and motion stimuli into motor coordination.

What does somatic motor control integrate for motor coordination?

Allow eyes to track and fixate on objects.

What are gaze centers responsible for?

Neural pools that produce rhythmic signals to the muscles of breathing and swallowing.

What are central pattern generators?

Cardiac and vasomotor centers of medulla oblongata

What is one function of networks related to cardiovascular control?

Some pain signals ascend through the reticular formation

How does the reticular formation relate to pain modulation?

In the reticular formation

Where do some descending analgesic pathways begin?

They end in the spinal cord where they block transmission of pain signals

What is the endpoint of descending analgesic pathways?

It plays a central role in consciousness, alertness and sleep

What role does the reticular formation play in sleep and consciousness?

Irreversible coma

What can injury to the reticular formation result in?

It modulates activity in cerebral cortex so that it ignores repetitive, inconsequential stimuli

What is habituation in the context of the reticular activating system?

the cerebellum

What is the largest part of the hindbrain and second largest part of the brain as a whole?

Right and left cerebellar hemispheres

What are the two main parts of the cerebellum?

vermis

What connects the right and left cerebellar hemispheres?

Gray matter with folds (folia)

What type of matter makes up the superficial cortex of the cerebellum?

Arbor vitae

What is the branching white matter in the cerebellum called?

About 100 billion

How many neurons does the cerebellum contain?

Small granule cells

What type of cells are abundant in the cerebellum?

Purkinje cells

What are the large cells in the cerebellum that have axons synapsing on deep nuclei?

Cerebellum

_________________ has long been known to be important for motor coordination and locomotor ability

cerebellum

What part of the brain works for comparing textures of objects, perceiving space, recognizing objects from different views

cerebellum

What part of the brain works for keeping judge of elapsed time and maintaining tapping rhythm and helping direct eye movements that compensate for head movements

cerebellum

What part of the brain works for judging the pitch of tones and distinguishing between similar spoken words, helping in verbal association tasks, and planning, scheduling, and emotion control

cerebellum

Many hyperactive children have small what?

diencephalon and telencephalon

What are the two parts that make up the forebrain?

diencephalon

part of the forebrain that encloses the third ventricle and most rostral part of the brainstem

telencephalon

Develops chiefly into the cerebrum

thalamus, hypothalamus, epithalamus

What three parts make up the diencephalon

thalamus

ovoid mass on each side of the brain perched at the superior end of the brainstem beneath the cerebral hemispheres

thalamus

Constitutes about four-fifths of the diencephalon

thalamus

Two thalami are joined medially by a narrow intermediate mass

thalamus

Composed of at least 23 nuclei within five major functional groups

The thalamus acts as a gateway to the cerebral cortex.

What is the role of the thalamus in relation to the cerebral cortex?

Nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei.

How does information pass to the cerebral cortex?

The thalamus filters information on its way to the cerebral cortex.

What does the thalamus do with incoming information?

It relays signals from the cerebellum to the cerebrum.

What is the role of the thalamus in motor control?

It provides feedback loops between the cerebral cortex and the basal nuclei.

How does the thalamus contribute to feedback loops?

Involved in memory and emotional functions.

What is the function of the thalamus?

The limbic system.

What complex of structures includes the thalamus?

Temporal and frontal lobes.

Which lobes of the brain are part of the limbic system?

Some anterior thalamic nuclei.

What are some components of the limbic system?

Hypothalamus

forms part of the walls and floor of the third ventricle

optic chiasm; mammillary bodies

The hypothalamus extends anteriorly to ________ __________ and posteriorly to __________________ _________

three

Each mammillary body contains ____ or four mammillary nuclei

hypothalamus

Relay signals from the limbic system to the thalamus

Infundibulum

stalk attaching pituitary to hypothalamus

hypothalamus

The major control center of autonomic nervous system and endocrine system

hypothalamus

Part of the diencephalon that plays essential role in homeostatic regulation of all body systems

Controls anterior pituitary, thereby regulating growth, metabolism, reproduction, and stress responses.

What is one function of the hypothalamic nuclei related to hormone secretion?

Hormones for labor contractions, lactation, and water conservation.

What hormones does the hypothalamus produce for the posterior pituitary?

They serve as a major integrating center for autonomic nervous system functions.

What role do hypothalamic nuclei play in the autonomic nervous system?

They influence heart rate, blood pressure, gastrointestinal secretions, motility, etc.

How do hypothalamic nuclei influence heart rate and blood pressure?

Thermoregulation

What is one function of the hypothalamus?