THE HUMAN BRAINTHE HUMAN BRAIN

THE AMAZING BRAIN!!!THE AMAZING BRAIN!!!

- the brain contains about 35 billion neurons!- the brain contains about 35 billion neurons!

- - all of our dreams, passions, memories, and all of our dreams, passions, memories, and plans are the result of brain activityplans are the result of brain activity

- the brain contains about 98% of the neural - the brain contains about 98% of the neural tissue of the bodytissue of the body

- - average brain weighs about 3 pounds average brain weighs about 3 pounds

- male brains are about 10 percent larger than - male brains are about 10 percent larger than female brains, but larger brains don’t indicate female brains, but larger brains don’t indicate more intelligence!more intelligence!

DIVISIONS OF THE BRAINDIVISIONS OF THE BRAIN

There are 6 major regions of the adult brain:There are 6 major regions of the adult brain:

1. Cerebrum1. Cerebrum

2. Diencephalon2. Diencephalon

3. Midbrain3. Midbrain

4. Pons4. Pons

5. Medulla oblongata5. Medulla oblongata

6. Cerebellum6. Cerebellum

SOME QUICK FACTS:SOME QUICK FACTS:

1. CEREBRUM1. CEREBRUM

- - Can be divided into paired CEREBRAL Can be divided into paired CEREBRAL HEMISPHERESHEMISPHERES

- conscious thoughts, sensations, intellectual - conscious thoughts, sensations, intellectual functions, memory storage and retrieval, functions, memory storage and retrieval, and complex movements originate hereand complex movements originate here

2. DIENCEPHALON2. DIENCEPHALON

- hollow, connected to cerebrum- hollow, connected to cerebrum

- - its sides form the THALAMUS, which its sides form the THALAMUS, which contains relay and processing centers for contains relay and processing centers for sensory infosensory info

- HYPOTHALAMUS (floor of diencephalon) is - HYPOTHALAMUS (floor of diencephalon) is connected to the pituitary glandconnected to the pituitary gland

- hypothalamus contains centers involved with - hypothalamus contains centers involved with emotions, autonomic function, and hormone emotions, autonomic function, and hormone productionproduction

- - pituitary gland links the nervous and pituitary gland links the nervous and endocrine systemsendocrine systems

3. MIDBRAIN3. MIDBRAIN

- - along with pons and medulla oblongata, along with pons and medulla oblongata, forms the BRAIN STEMforms the BRAIN STEM

- nuclei in the midbrain process visual and - nuclei in the midbrain process visual and auditory info and generate involuntary motor auditory info and generate involuntary motor responsesresponses

- - also contains centers that maintain also contains centers that maintain consciousnessconsciousness

4. PONS4. PONS

- - acts like a bridge to connect the cerebellum acts like a bridge to connect the cerebellum to the brain stemto the brain stem

- contains nuclei involved with somatic and - contains nuclei involved with somatic and visceral motor controlvisceral motor control

- also connected to medulla oblongata- also connected to medulla oblongata

5. MEDULLA OBLONGATA5. MEDULLA OBLONGATA

- attached to spinal cord- attached to spinal cord

- - relays sensory info to thalamus and other relays sensory info to thalamus and other brain stem centersbrain stem centers

- contains centers that regulate heart rate, - contains centers that regulate heart rate, blood pressure, respiration, and digestive blood pressure, respiration, and digestive activitiesactivities

6. CEREBELLUM6. CEREBELLUM

- adjusts voluntary and involuntary motor - adjusts voluntary and involuntary motor activities on the basis of sensory info and activities on the basis of sensory info and stored memories of previous movementsstored memories of previous movements

Ventricles Ventricles

The brain has a central passageway that The brain has a central passageway that expands to form 4 chambers- VENTRICLESexpands to form 4 chambers- VENTRICLES

- - Each hemisphere contains a large Each hemisphere contains a large LATERAL VENTRICLELATERAL VENTRICLE

* there is no direct connection between the * there is no direct connection between the 2, but an opening called the 2, but an opening called the interventricular interventricular foramenforamen allows each to communicate with allows each to communicate with the THIRD VENTRICLEthe THIRD VENTRICLE

- The midbrain has a slender canal called the - The midbrain has a slender canal called the mesencephalic aqueductmesencephalic aqueduct which connects which connects the third ventricle with the FOURTH the third ventricle with the FOURTH VENTRICLEVENTRICLE

* in the medulla oblongata, the fourth * in the medulla oblongata, the fourth ventricle narrows and becomes continuous ventricle narrows and becomes continuous with the central canal of the spinal cordwith the central canal of the spinal cord

Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)Surrounds and bathes exposed surfaces of CNSSurrounds and bathes exposed surfaces of CNS

- - cushions delicate neural structurescushions delicate neural structures

- supports- the brain floats in CSF- supports- the brain floats in CSF

- - can be drawn to diagnose injury, infection, or can be drawn to diagnose injury, infection, or diseasedisease

- produced at CHOROID PLEXUS, a network of - produced at CHOROID PLEXUS, a network of capillaries that extend into each ventriclecapillaries that extend into each ventricle

- - entire volume of CSF is replaced every 8 entire volume of CSF is replaced every 8 hourshours

CerebrumCerebrum

The cerebrum is the largest region of the The cerebrum is the largest region of the brain, and the site where conscious thought brain, and the site where conscious thought and intellectual functions originateand intellectual functions originate

- - contains gray and white mattercontains gray and white matter

STRUCTURE OF CEREBRUMSTRUCTURE OF CEREBRUMCEREBRAL CORTEX- CEREBRAL CORTEX- covers superior and covers superior and

lateral surfaces of cerebrumlateral surfaces of cerebrum

- this outer surface forms a series of elevated - this outer surface forms a series of elevated ridges or GYRI, which are separated by shallow ridges or GYRI, which are separated by shallow depressions called SULCI, or deeper grooves depressions called SULCI, or deeper grooves called FISSUREScalled FISSURES

The 2 HEMISPHERES are separated by a deep The 2 HEMISPHERES are separated by a deep longitudinal fissurelongitudinal fissure

- extending laterally from the longitudinal fissure is - extending laterally from the longitudinal fissure is a deep groove called the CENTRAL SULCUSa deep groove called the CENTRAL SULCUS

Each hemisphere can be divided into lobes Each hemisphere can be divided into lobes

- - named after overlying bones of skullnamed after overlying bones of skull

- in each lobe, some regions are concerned - in each lobe, some regions are concerned with sensory info. and others with motor with sensory info. and others with motor commandscommands

Each hemisphere receives sensory info. from Each hemisphere receives sensory info. from and sends motor commands to opposite and sends motor commands to opposite sides of the bodysides of the body

MOTOR AND SENSORY MOTOR AND SENSORY AREAS OF CORTEXAREAS OF CORTEX

The central sulcus separates motor and sensory The central sulcus separates motor and sensory portions of the cortexportions of the cortex

- PRECENTRAL GYRUS- - PRECENTRAL GYRUS- surface is the surface is the primary motor cortexprimary motor cortex

* here neurons direct voluntary movements by * here neurons direct voluntary movements by controlling somatic motor neurons in the brain controlling somatic motor neurons in the brain stem and spinal cordstem and spinal cord

- POSTCENTRAL GYRUS- - POSTCENTRAL GYRUS- contains primary contains primary sensory cortexsensory cortex

* neurons here receive somatic sensory * neurons here receive somatic sensory information from touch, pressure, pain, and information from touch, pressure, pain, and temperature receptorstemperature receptors

Other sensations arrive at other portions of the Other sensations arrive at other portions of the cortex:cortex:

- - visual cortexvisual cortex

- - gustatory cortex (taste)gustatory cortex (taste)

- - auditory cortexauditory cortex

- - olfactory cortex (smell)olfactory cortex (smell)

ASSOCIATION AREAS OF THE ASSOCIATION AREAS OF THE CORTEXCORTEX

Sensory and motor regions of the cortex are Sensory and motor regions of the cortex are connected to association areas that interpret connected to association areas that interpret incoming data or coordinate a motor incoming data or coordinate a motor responseresponse

SOMATIC SENSORY ASSOCIATION AREASOMATIC SENSORY ASSOCIATION AREA

- - monitors activity in the primary sensory monitors activity in the primary sensory cortexcortex

- allows you to recognize a very light touch- allows you to recognize a very light touch

SOMATIC MOTOR ASSOCIATION AREASOMATIC MOTOR ASSOCIATION AREA

- - responsible for coordinating learned responsible for coordinating learned movementsmovements

CORTICAL CONNECTIONSCORTICAL CONNECTIONS

Regions of cortex are interconnected by the Regions of cortex are interconnected by the white matter belowwhite matter below

- the white matter interconnects areas within a - the white matter interconnects areas within a single cerebral hemisphere and links the 2 single cerebral hemisphere and links the 2 hemispheres across the CORPUS hemispheres across the CORPUS CALLOSUMCALLOSUM

PROCESSING CENTERS OF PROCESSING CENTERS OF CORTEXCORTEX

There are “higher-order” integrative centers that There are “higher-order” integrative centers that receive information through axons from many receive information through axons from many different association areasdifferent association areas

- - these areas control extremely complex motor these areas control extremely complex motor activities and perform complicated analytical activities and perform complicated analytical functionsfunctions

1. GENERAL INTERPRETIVE AREA1. GENERAL INTERPRETIVE AREA

- - receives info. from all sensory association areasreceives info. from all sensory association areas

- is present only in 1 hemisphere (usually left)- is present only in 1 hemisphere (usually left)

- - damage to this area effects ability to damage to this area effects ability to interpret what is read or heardinterpret what is read or heard

2. SPEECH CENTER2. SPEECH CENTER

- - regulates patterns of breathing and regulates patterns of breathing and vocalization needed for normal speechvocalization needed for normal speech

- damage can cause difficulty speaking even - damage can cause difficulty speaking even when you know which words to use; or when you know which words to use; or talking constantly but using the wrong wordstalking constantly but using the wrong words

3. PREFRONTAL CORTEX3. PREFRONTAL CORTEX

- - coordinates info. from association areas coordinates info. from association areas of the entire cortexof the entire cortex

- performs abstract functions like predicting - performs abstract functions like predicting future consequences of events or actionsfuture consequences of events or actions

- - damage leads to problems in estimating damage leads to problems in estimating time relationships between eventstime relationships between events

A QUICK LESSON ON MEMORY….FACT MEMORIES are specific bits of info.- such as the color of a stop signSKILL MEMORIES are learned behaviors- such as tying your shoes2 Classes of memories: 1. SHORT–TERM- do not last long, but

can be recalled immediately- Ex: phone number

2. LONG-Term- remain for much longer* the conversion from short to long is called MEMORY CONSOLIDATION* most long-term memories are stored in the cerebral cortex

AMNESIA- loss of memory from disease or trauma

- type of memory loss depends on the regions of the brain affected

Basal NucleiBasal NucleiThe basal nuclei direct activities that are outside of our The basal nuclei direct activities that are outside of our

conscious awarenessconscious awareness

- they are masses of gray matter that lie below the lateral - they are masses of gray matter that lie below the lateral ventricles and within the white matter of each cerebral ventricles and within the white matter of each cerebral hemispherehemisphere

COMPONENTS:COMPONENTS:

1. 1. Caudate NucleusCaudate Nucleus

2. Lentiform Nucleus- lies below caudate nucleus2. Lentiform Nucleus- lies below caudate nucleus

* * globus pallidusglobus pallidus

* * putamenputamen

3. Amygdaloid body- 3. Amygdaloid body- lies below the lentiform lies below the lentiform nucleusnucleus

The basal nuclei are involved with the The basal nuclei are involved with the subconscious control of skeletal muscle tone subconscious control of skeletal muscle tone and coordination of learned movement and coordination of learned movement patternspatterns

- - they do NOT begin a movement, but they do NOT begin a movement, but provide pattern and rhythm once a provide pattern and rhythm once a movement is startedmovement is started

http://www.colorado.edu/kines/Class/IPHY3730/image/figure5-31.jpghttp://www.colorado.edu/kines/Class/IPHY3730/image/figure5-31.jpg

Limbic SystemLimbic System

The LIMBIC SYSTEM includes the olfactory The LIMBIC SYSTEM includes the olfactory cortex, several basal nuclei, gyri, and cortex, several basal nuclei, gyri, and tracts along the border of the cerebrum tracts along the border of the cerebrum and diencephalonand diencephalon

FUNCTIONS: FUNCTIONS:

1. 1. Establishing emotional states and Establishing emotional states and related behavioral drivesrelated behavioral drives

2. Linking conscious functions of cerebral 2. Linking conscious functions of cerebral cortex with unconscious functions of brain cortex with unconscious functions of brain stemstem

3. Long-term memory storage and retrieval3. Long-term memory storage and retrieval

* * damage to HIPPOCAMPUS that occurs damage to HIPPOCAMPUS that occurs in Alzheimer’s interferes with memory in Alzheimer’s interferes with memory storage and retrievalstorage and retrieval

The limbic system also includes hypothalamic The limbic system also includes hypothalamic centers that control: centers that control:

- - emotional states- rage, fear, sexual emotional states- rage, fear, sexual arousalarousal

- reflex movements that can be consciously - reflex movements that can be consciously activated (chewing, swallowing)activated (chewing, swallowing)

http://general.rau.ac.za/psych/Resources/Honours/Neuropsych/Downloads/downloadstr/http://general.rau.ac.za/psych/Resources/Honours/Neuropsych/Downloads/downloadstr/Lect2-opt/limbic%20system.jpgLect2-opt/limbic%20system.jpg

DiencephalonDiencephalonThe DIENCEPHALON provides switching and relay The DIENCEPHALON provides switching and relay

centers that integrate conscious and centers that integrate conscious and unconscious sensory info. and motor commandsunconscious sensory info. and motor commands

3 COMPONENTS:3 COMPONENTS:

1. EPITHALAMUS1. EPITHALAMUS

- - forms roof of diencephalonforms roof of diencephalon

- contains PINEAL GLAND- - contains PINEAL GLAND- endocrine structure endocrine structure that secretes the hormone MELATONINthat secretes the hormone MELATONIN

2. THALAMUS2. THALAMUS

- final relay point for all ascending sensory info. - final relay point for all ascending sensory info. other than olfactory that will reach our other than olfactory that will reach our conscious awarenessconscious awareness

- acts as a filter, passing on to the primary - acts as a filter, passing on to the primary sensory cortex only a small portion of arriving sensory cortex only a small portion of arriving sensory info.sensory info.

- - also plays a role in coordinating voluntary also plays a role in coordinating voluntary and involuntary motor commandsand involuntary motor commands

3. HYPOTHALAMUS3. HYPOTHALAMUS

- contains important control and - contains important control and integrative centers in addition to those integrative centers in addition to those associated with the limbic systemassociated with the limbic system

MANY DIVERSE FUNCTIONS:MANY DIVERSE FUNCTIONS:

- - subconscious control of skeletal subconscious control of skeletal muscle contractions associated muscle contractions associated with rage, pleasure, painwith rage, pleasure, pain

- adjusting activities of autonomic - adjusting activities of autonomic centers of pons and medulla oblongata centers of pons and medulla oblongata (heart rate, blood pressure)(heart rate, blood pressure)

- - secreting hormonessecreting hormones

- producing behavioral drives involved in - producing behavioral drives involved in hunger and thirsthunger and thirst

- - regulating normal body regulating normal body temperaturetemperature

MidbrainThe MIDBRAIN contains 2 pairs of sensory nuclei or

COLLICULI dealing with processing of visual and auditory sensations

- SUPERIOR COLLICULI- controls reflex movements of eyes, head, and neck in response to visual stimuli (flash of light)

- INFERIOR COLLICULI- control reflex movements of head, neck and trunk to

auditory stimuli (loud noise)

Descending bundles of nerve fibers make up the CEREBRAL PEDUNCLES

The midbrain contains the RETICULAR FORMATION, which regulates many involuntary functions

- contains the reticular activation system (RAS) which directly affects the activity of the cerebral cortex

- when RAS is inactive, so are we

http://www.stanford.edu/group/hopes/rltdsci/trinuc/f_f10midcereb.jpg

Pons

The PONS links the cerebellum with the midbrain, diencephalon, cerebrum, and spinal cord

Cerebellum

The CEREBELLUM is an automatic processing center

2 IMPORTANT FUNCTIONS:

1. Adjusting postural muscles of body to maintain balance

2. Programming and fine-tuning movements controlled at conscious and subconscious levels

- the cerebellum compares motor commands with proprioceptive info. (position sense) and performs adjustments needed to make movement smooth

- tracts that link the cerebellum with these different regions are the CEREBELLAR PEDUNCLES

- cerebellum can be permanently damaged by trauma, stroke, and drugs- produce ATAXIA (disturbance in balance)

Medulla OblongataMedulla Oblongata

The MEDULLA OBLONGATA connects the brain The MEDULLA OBLONGATA connects the brain with the spinal cordwith the spinal cord

- all communication between the brain and - all communication between the brain and spinal cord involves tracts that ascend or spinal cord involves tracts that ascend or descend through the medulla oblongatadescend through the medulla oblongata

* CARDIOVASCULAR CENTERS- * CARDIOVASCULAR CENTERS- adjust heart adjust heart rate, strength of cardiac contractions, rate, strength of cardiac contractions, and flow of blood and flow of blood

* RESPIRATORY RHYTHMICITY CENTERS- set * RESPIRATORY RHYTHMICITY CENTERS- set basic pace for respiratory movementsbasic pace for respiratory movements

PEREPHERAL NERVOUS SYSTEM

PNS

The PERIPHERAL NERVOUS SYSTEM (PNS) is the link between the neurons of the central nervous system (CNS) and the rest of the body

- all sensory information and motor commands are carried by axons of the PNS

- these axons, bundled together and wrapped in connective tissue, form PERIPHERAL NERVES

Cranial nerves originate from the brain and spinal nerves connect to the spinal cord

- the PNS also contains both the cell bodies and the axons of sensory neurons and motor neurons of the autonomic nervous system

Cranial Nerves

There are 12 pairs of CRANIAL NERVES that connect to the brain

- they are numbered according to their position along the longitudinal axis of the brain

- you will label and identify the functions of these nerves

Spinal Nerves

There are 31 pairs of spinal nerves that can be grouped according to the region of the vertebral column from which they originate

- 8 pairs of cervical nerves- 12 pairs of thoracic nerves- 5 pairs of lumbar nerves - 5 pairs of sacral nerves- 1 pair of coccygeal nerves

Each pair of spinal nerves monitors a specific region of the body surface known as a DERMATOME

- dermatomes are clinically important because damage or infection of a spinal nerve or dorsal root ganglia will produce a characteristic loss of sensation in specific parts of the skin

http://anatomy.med.umich.edu/modules/spinal_cord_module/Files/SC_cnspnsimg.jpg

http://www.stephblog.com/dermatomes.jpg