Unit 5 Anatomy ch.14

Capillaries

-- in the CNS are impermeable to many compounds because of the blood-brain barrier

4 ventricles in the brain

-two lateral ventricles -interventricular foramen -third ventricle -fourth ventricle

functions of the CSF

1. Cushioning delicate neural structures 2. supporting the brain the brain floats in CSF; in air, the brain weight ~3lbs, suspended in CSF, the brain only weighs ~1.8oz 3. Transporting nutrients and waste products spinal tap, or lumbar puncture

functions of the medulla

1.Autonomic reflex centers - vital control of autonomic visceral functions like cardiac, vasomotor, and respiratory centers that regulate heart rate, vessel diameter, and respiration, respectively. 2.Controls cranial nerves for muscles of pharynx, neck, and ventral body cavity (vagus nerve) and sensations of hearing and equilibrium. 3.Relays sensory information to the thalamus.

functions of cerebellum

1.Controls posture and balance by making rapid, automatic adjustments of skeletal muscle contractions for activities like standing and walking. This allows voluntary motor responses to function subconsciously. Ex: Once the cerebrum (motor cortex) initiates the motor commands to walk, the cerebellum coordinates the muscle contractions so walking occurs without falling. 2.Stores learned muscle memory patters like dancing, playing a musical instrument, throwing a ball, etc. The cerebellum compares motor commands with proprioception (sense of body position) and makes adjustments in muscle activity. Repeating the patterns lead to muscle memory (learning a dance routine or a song on piano).

thalamus functions

1.Relay station for all sensory information except smell and proprioception. Filters out unnecessary information and relays important information to the appropriate regions of the cerebral cortex 2.Interpretation center for sensory impulses of pain, temp, touch, pressure (gives us a crude sense of awareness) 3.Passes information from the limbic system to the cerebral cortex so that we become consciously aware of our emotions.

hypothalamus functions

1.Secretes hormones (at the posterior pituitary) 2.Coordinates activities of the nervous and endocrine systems (at ant. pituitary) 3.Regulates autonomic function 4.Initiates emotions and behavioral drives 5.Regulates body temperature 6.Subconscious control of skeletal muscle contractions 7.Coordinates somatic and autonomic functions ("mind over body" phenomena).

Pons functions

1.contains sensory and motor nuclei for cranial nerves of face and ears 2.passes sensory and motor information to and from spinal cord and medulla to cerebellum and thalamus 3. controls respiration- centers work with the medulla for breathing

functions of the limbic system

1.establish out emotional state 2.link conscious intellectual functions with subconscious autonomic functions, as well as with our unconscious brain 3.facilitate conversion of short-term memory into long-term memory 4.storage of long-term memory 5.retrieval of memory

Circulation of CSF

CSF formed in lateral ventricles → interventricular foramen → 3rd ventricle → cerebral (mesencephalic) aqueduct → 4th ventricle, then fills central canal of spinal cord → lateral apertures and median aperture → subarachnoid space → arachnoid granulations → superior sagittal sinus

blood stream and lack the blood-brain barrier

Certain areas of the brain that help maintain homeostasis must direct have access to the

cerebellum

Coordination of somatic motor patterns, balance, coordination, proprioception

meningeal layers

Dura mater arachnoid mater pia mater

cerebrum function

Largest region of the human brain Processes sensory and motor information that we are consciously aware of Performs intellectual functions like thinking and problem solving

limbic system

Limbus means border and the limbic system is a group of nuclei that lies at the border between the cerebrum and the diencephalon. The --------- is spread out and is more of a collection of nuclei that function together rather than form an anatomical structure.

Pons

Located superior to the medulla and anterior to the cerebellum the pons is literally a bridge to the cerebellum. The cerebellar peduncles (myelinated axons) pass through the pons and connect the cerebellum to the rest of the brain.

Cortical Specialization

Olfactory cortex - temporal lobe Visual cortex - occipital lobe Auditory cortex - temporal lobe Gustatory cortex - insula and frontal lobe

hippocampus

One of the major structures of the limbic system is the

Medulla oblongata

Part of brain stem; control of visceral organs such as heart and lungs

pons

Part of brain stem; control of visceral organs, sensory relay to thalamus

speech area and prefrontal cortex

Specific regions of the cortex perform special functions

diencephalon

Thalamus-sensory filter and relay to cerebrum Hypothalamus-controls emotions, autonomic function, hormone production

internal jugular vein

The ----- drains most of the deoxygenated blood from the brain.

postcentral gyrus

The ----- is the primary sensory cortex and receives sensory information regarding touch, temperature, vibration, pressure, and pain from specific areas of the body.

precentral gyrus

The ------ is part of the frontal lobe and contains the primary motor cortex The primary motor cortex contains neurons that control voluntary (somatic) motor movements. Stimulating a specific region of the precentral gyrus will cause a contraction in a specific skeletal muscle.

Cerebrospinal Fluid (CSF)

The CSF is a clear fluid that is produced by specialized capillary beds in each ventricle called the choroid plexus. CSF delivers glucose, other nutrients, and ions necessary to keep neurons functioning properly. It also washes away wastes and debris to be reabsorbed back into the blood stream. CSF is produced at a rate of 500mL/day. The total volume of CSF at any time is 150mL; this means that the entire volume of CSF is replaced every 8 hours.

hemispheres

The Cerebrum is divided in to two halves called--which are covered with the cerebral cortex.

60

The brain has a very high metabolic rate. The 3.5lb brain burns as much oxygen as about ?lbs of muscle

neurons and neuroglia

The brain is comprised of

internal carotid and vertebral arteries.

The brain is supplied with blood rich in oxygen and nutrients by the

cerebellum

The cerebellum sits posterior to the pons and medulla and just inferior to the occipital lobe. The cerebellum loosely resembles a miniature version of the cerebrum in that it has folds of gray matter (folia) providing a layer of cortex that surrounds or encapsulates the highly branched white matter (arbor vitae). The cerebellum also has several cerebellar peduncles that connect the cerebellum to the pons and other brain structures.

motivational system

The cerebral cortex and association areas perform complex tasks, but the limbic system makes you want to perform them. That is why it is also called the .

superior colliculi and inferior colliculi

The corpora quadrigemina are two pairs (4) sensory nuclei that coordinate our "startling" reflexes.

stabilization

The dura mater extends into the brain for

3.5lbs

The human brain weighs about ---- and is housed in and protected by the skull

Midbrain (Mesencephalon)

The mesencephalon extends from the superior border of the pons to the inferior border of the diencephalon. The cerebral (mesencephalic) aqueduct of the ventricular system passes through the midbrain to connect the third and fourth ventricles. Corpora Quadrigemina

longitudinal fissure

The two hemispheres are separated sagittally by a very deep groove called the

blood-brain barrier

This barrier is maintained by astrocytes and the tight junctional complexes they form between blood vessels and neural tissue.

cerebrum

Thought and intellectual functions, memory, voluntary muscle contractions, special senses

gyri (singular gyrus) sulci or sulcus

To increase surface area for more neurons the cortex is folded, creating elevated folds (hills) called and shallow grooves called

precentral and postcentral gyri,

Two major landmarks in the cerebrum are the---which are separated by the central sulcus.

lateral sulcus

a groove that separates parietal from temporal lobes

pineal gland

an endocrine organ that hangs off the posterior edge of the diencehpalon. It secretes a hormone called melatonin that controls our circadian rhythm of the body's sleep-wake cycles

The brain

and is considered to be the command and control center for most of the body. It is similar to a CPU of a computer. It receives input from sensory pathways, neurons carry out action potentials and process this information to decide what to do about it, and then the brain sends out motor commands to skeletal muscle (via the somatic nervous system) and to smooth and cardiac muscle (via the autonomic nervous system) to meet the body's demands and needs.

frontal lobe

anterior, sits below the frontal bone of the skull

ventricles

are chambers in the brain where cerebrospinal fluid (CSF) is produced and circulates to protect and help nourish the brain.

mammillary bodies

are hypothalamic centers for chewing, licking and sucking.

cerebral peduncles

are myelinated axons that connect the forebrain, cerebral nuclei, and thalamus to the brainstem. It appears on the brain as a series of lines or grooves that run up from the pons to the thalamus. It carries sensory information to the higher brain from the brain stem and spinal cord, and it carries motor commands from the primary motor cortex to the spinal cord.

meninges

are specialized membranes that surround the brain and spinal cord. They protect the brain and spinal cord from injury, debris, and pathogens, as well as serve to contain the CSF to the brain and spinal cord.

hypothalamus pituitary gland pineal gland choroid plexus

areas of the brain that help maintain homeostasis

fourth ventricle

by the cerebral aqueduct (also called the mesencephalic aqueduct, or aqueduct of Sylvius). The fourth ventricle lies between the brain stem and the cerebellum. The fourth ventricle is continuous with the central canal of the spinal cord and the subarachnoid space.

Homunculus

commonly used to describe the distorted human figure drawn to reflect the relative space human body parts occupy on the somatosensory cortex (sensory homunculus) and the motor cortex (motor homunculus

projection fibers

connect and transmit impulses between the cortex and the brain stem. Projection fibers pass through the thalamus and form the internal capsule of the cerebral nuclei.

commisural fibers

connect and transmit impulses between the right and left hemispheres. Commisural fibers make up the corpus callosum and anterior commissure.

Association (arcuate) fibers

connect and transmit impulses from one gyrus to another, or from one lobe to another within the same hemisphere.

Central White Matter

connects different brain regions. The axons are often called fibers and connect brain structures 1.association (arcuate) fibers 2.commisural fibers 3.projection fibers

hippocampus function

converts short-term memories into long-term memories. also stores long-term memories and functions in memory recall. It is connected to the thalamus and hypothalamus via the fornix.

inferior colliculi (2)

coordinate auditory reflexes (turning the head towards a loud sound)

superior colliculi (2)

coordinate visual reflexes (head, neck, and eye movement to follow a moving object or to turn the head towards something moving in the periphery)

white matter

deep to the cortex, consists almost entirely of myelinated axons that connect one area of the cortex to others, and to the lower structures of the brain like the nuclei, limbic system, and brain stem

dural folds

falx cerebri, falx cerebelli and tentorium cerebelli

Speech area (Broca's area)

found in the area that lies just anterior to the precentral gyrus called the premotor cortex. It receives sensory information from the interpretive area and coordinates contraction of muscles necessary to vocalize (speak). Damage to Broca's area results in a condition known as expressive aphasia

arachnoid mater

he middle layer and lies deep to the dura mater. It is held up off of the pia mater by collagenous structures called arachnoid granulations and arachnoid villi. This provides a space, the subarachnoid space, for CSF to flow along the outer surface of the brain.

insula

hidden lobe that is deep and medial to temporal lobes

basal nuclei function

in subconscious control of voluntary skeletal muscle movement. They do not initiate the movement, but once the thought to initiate movement forms these nuclei coordinate subconscious patterns and rhythms of your movements. A good example is the turning of the trunk of the body and swinging of the arms during walking, or stabilizing the shoulder and upper arm while you consciously control your hand and fingers while writing.

Hypothalamus

inferior to the thalamus, it comprises the floor and lower walls of the third ventricles.

gustatory cortex

insula and frontal lobe

Basal Ganglia (Nuclei)

is a collective term to describe the major cerebral nuclei. Remember that within the CNS a collection of somata is called a nucleus or center. There are two basal ganglia, one in each hemisphere that lie just superior to the thalamus. The basal ganglia form the floor of the lateral ventricles. The basal ganglia contain the caudate nucleus, internal capsule, and putamen.

third ventricle

is sandwiched between the two halves of the thalamus. It is connected to the fourth ventricle

medulla oblongata

is the most inferior brain structure and is continuous with the spinal cord. It sits in the cranium just inside the foramen magnum. It carries all the ascending (sensory) and descending (motor) axons from the spinal cord to all structures of the brain. Decussation, or crossing over, of motor fibers occurs in the medulla and forms thick bands of tissue called pyramids. Since nerve tracts cross, the right primary motor cortex controls muscles on the left side of the body, and vice versa.

parietal lobes

just posterior to frontal lobe sits below parietal bones

temporal lobes

lateral, sits below temporal bones

Hemispheric Specialization

left and right

Hydrocephalus

literally means "water on the brain"; occurs when there is an abnormal accumulation of cerebrospinal fluid in the ventricles, leading to increased intracranial pressure.

prefrontal cortex

located at the most anterior area of the frontal lobe. It receives and interprets information from many other areas of the brain to perform intellectual functions. It does a tremendous amount of "thinking" about sequential events (what happens first, next, and then last) and cause and effect situations (if I do this, then that happens). The prefrontal cortex controls the mental option to delay immediate gratification for a better or more rewarding longer-term gratification result. This ability to wait for a reward is one of the key pieces that define optimal executive function of the human brain.

Landmarks of the Cortex

longitudinal fissure central sulcus frontal lobe parietal lobe lateral sulcus temporal sulcus occipital lobe insula

thalamus

made up of two oval masses separated by the third ventricle. They are connected across that ventricle by the intermediate mass (like a dumbbell with the weights one each end with a handle in the middle).

Major brain regions

medulla oblongata, pons, midbrain, diencephalon, cerebellum, cerebrum

hypothalamus

monitors electrolytes (salts) and water concentrations

occipital lobe

most posterior lobe, sits below occipital bone

visual cortex

occipital lobe

A stroke or cerebrovascular accident (CVA)

occurs when blood flow is disrupted to a part of the brain. CVAs occur when a vessel narrows and flow is reduced, or a vessel ruptures and bleeds into the spaces surrounding the brain causing compression of delicate neural tissues. A CVA can also be caused by an embolus (a traveling blood clot or piece of plaque) becoming lodged in a small artery or arteriole.

two lateral ventricles

one in each hemisphere just above the thalamus. They are separated from each other by a thin membrane called the septum pellucidum. In the floor of each lateral ventricle is a small hole called an interventricular foramen that connects them to the third ventricle

cerebral cortex

outer gray matter, consists of cell bodies of neurons

dura mater

outermost layer that is thick and tough due to numerous collagen fibers. The dura mater has an endosteal layer that is adhered to the skull and an inner meningeal layer. The gap between the two layers, called the subdural space) contains blood vessels, including two large viens called sinuses (superior and inferior sagittal sinuses).

midbrain

part of the brain stem; visual and auditory reflexes

choroid plexus

produces CSF

diencephalon

s made up of the pineal gland, thalamus, and hypothalamus, and a few associated structures.

pineal gland

secreted a hormone called melatonin into the blood

pituitary gland

secretes a number of hormones into the blood

central sulcus

separates frontal and parietal lobes

longitudinal fissure

separates right and left hemispheres

right hemi

specializes in interpreting non-verbal sounds (music, bird chirps, barking dogs) and visual information (shapes, colors, forms). People who are good at these subjects (painting, drawing, music) are said to be right-brain people. The right hemisphere deals with images and sounds that represent something and is often called the representational hemisphere.

left hemi

specializes in interpreting speech, reading, and writing, as well as analytical tasks like math, logic, and science. People who are good at these subjects (writers, mathematicians, accountants, scientists) are said to be left-brain people. The left hemisphere deals with quantitative processing and organization and is also called the categorical hemisphere.

auditory cortex

temporal lobe

olfactory cortex

temporal lobe

cranial meninges, CSF, and blood brain barrier

the brain is protected by

pia mater

the deepest of the three layers and is tightly adhered to the surface of the brain. It is the most delicate.