THE HUMAN BRAIN

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THE HUMAN BRAIN
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THE AMAZING BRAIN!!!

• - the brain contains about 35 billion neurons!
• - all of our dreams, passions, memories, and
  plans are the result of brain activity
• - the brain contains about 98 of the neural
  tissue of the body
• - average brain weighs about 3 pounds
• - male brains are about 10 percent larger than
  female brains, but larger brains dont indicate
  more intelligence!

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DIVISIONS OF THE BRAIN

• There are 6 major regions of the adult brain
• 1. Cerebrum
• 2. Diencephalon
• 3. Midbrain
• 4. Pons
• 5. Medulla oblongata
• 6. Cerebellum

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SOME QUICK FACTS

• 1. CEREBRUM
• - Can be divided into paired CEREBRAL HEMISPHERES
• - conscious thoughts, sensations, intellectual
  functions, memory storage and retrieval, and
  complex movements originate here
• 2. DIENCEPHALON
• - hollow, connected to cerebrum

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• - its sides form the THALAMUS, which contains
  relay and processing centers for sensory info
• - HYPOTHALAMUS (floor of diencephalon) is
  connected to the pituitary gland
• - hypothalamus contains centers involved with
  emotions, autonomic function, and hormone
  production
• - pituitary gland links the nervous and endocrine
  systems

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• 3. MIDBRAIN
• - along with pons and medulla oblongata, forms
  the BRAIN STEM
• - nuclei in the midbrain process visual and
  auditory info and generate involuntary motor
  responses
• - also contains centers that maintain
  consciousness

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• 4. PONS
• - acts like a bridge to connect the cerebellum to
  the brain stem
• - contains nuclei involved with somatic and
  visceral motor control
• - also connected to medulla oblongata
• 5. MEDULLA OBLONGATA
• - attached to spinal cord
• - relays sensory info to thalamus and other brain
  stem centers

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• - contains centers that regulate heart rate,
  blood pressure, respiration, and digestive
  activities
• 6. CEREBELLUM
• - adjusts voluntary and involuntary motor
  activities on the basis of sensory info and
  stored memories of previous movements

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Ventricles

• The brain has a central passageway that expands
  to form 4 chambers- VENTRICLES
• - Each hemisphere contains a large LATERAL
  VENTRICLE
• there is no direct connection between the 2,
  but an opening called the interventricular
  foramen allows each to communicate with the THIRD
  VENTRICLE

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• - The midbrain has a slender canal called the
  mesencephalic aqueduct which connects the third
  ventricle with the FOURTH VENTRICLE
• in the medulla oblongata, the fourth ventricle
  narrows and becomes continuous with the central
  canal of the spinal cord

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Cerebrospinal Fluid (CSF)

• Surrounds and bathes exposed surfaces of CNS
• - cushions delicate neural structures
• - supports- the brain floats in CSF
• - can be drawn to diagnose injury, infection, or
  disease
• - produced at CHOROID PLEXUS, a network of
  capillaries that extend into each ventricle
• - entire volume of CSF is replaced every 8 hours

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Cerebrum

• The cerebrum is the largest region of the brain,
  and the site where conscious thought and
  intellectual functions originate
• - contains gray and white matter

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STRUCTURE OF CEREBRUM

• CEREBRAL CORTEX- covers superior and lateral
  surfaces of cerebrum
• - this outer surface forms a series of elevated
  ridges or GYRI, which are separated by shallow
  depressions called SULCI, or deeper grooves
  called FISSURES
• The 2 HEMISPHERES are separated by a deep
  longitudinal fissure
• - extending laterally from the longitudinal
  fissure is a deep groove called the CENTRAL SULCUS

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• Each hemisphere can be divided into lobes
• - named after overlying bones of skull
• - in each lobe, some regions are concerned with
  sensory info. and others with motor commands
• Each hemisphere receives sensory info. from and
  sends motor commands to opposite sides of the body

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MOTOR AND SENSORY AREAS OF CORTEX

• The central sulcus separates motor and sensory
  portions of the cortex
• - PRECENTRAL GYRUS- surface is the primary motor
  cortex
• here neurons direct voluntary movements by
  controlling somatic motor neurons in the brain
  stem and spinal cord
• - POSTCENTRAL GYRUS- contains primary sensory
  cortex

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• neurons here receive somatic sensory
  information from touch, pressure, pain, and
  temperature receptors
• Other sensations arrive at other portions of the
  cortex
• - visual cortex
• - gustatory cortex (taste)
• - auditory cortex
• - olfactory cortex (smell)

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ASSOCIATION AREAS OF THE CORTEX

• Sensory and motor regions of the cortex are
  connected to association areas that interpret
  incoming data or coordinate a motor response
• SOMATIC SENSORY ASSOCIATION AREA
• - monitors activity in the primary sensory cortex
• - allows you to recognize a very light touch

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• SOMATIC MOTOR ASSOCIATION AREA
• - responsible for coordinating learned movements

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CORTICAL CONNECTIONS

• Regions of cortex are interconnected by the white
  matter below
• - the white matter interconnects areas within a
  single cerebral hemisphere and links the 2
  hemispheres across the CORPUS CALLOSUM

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PROCESSING CENTERS OF CORTEX

• There are higher-order integrative centers that
  receive information through axons from many
  different association areas
• - these areas control extremely complex motor
  activities and perform complicated analytical
  functions
• 1. GENERAL INTERPRETIVE AREA
• - receives info. from all sensory association
  areas
• - is present only in 1 hemisphere (usually left)

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• - damage to this area effects ability to
  interpret what is read or heard
• 2. SPEECH CENTER
• - regulates patterns of breathing and
  vocalization needed for normal speech
• - damage can cause difficulty speaking even when
  you know which words to use or talking
  constantly but using the wrong words

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• 3. PREFRONTAL CORTEX
• - coordinates info. from association areas of the
  entire cortex
• - performs abstract functions like predicting
  future consequences of events or actions
• - damage leads to problems in estimating time
  relationships between events

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A QUICK LESSON ON MEMORY.

• FACT MEMORIES are specific bits of info.
• - such as the color of a stop sign
• SKILL MEMORIES are learned behaviors
• - such as tying your shoes
• 2 Classes of memories
• 1. SHORTTERM- do not last long, but can be
  recalled immediately
• - Ex phone number

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• 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

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Basal Nuclei

• The basal nuclei direct activities that are
  outside of our conscious awareness
• - they are masses of gray matter that lie below
  the lateral ventricles and within the white
  matter of each cerebral hemisphere
• COMPONENTS
• 1. Caudate Nucleus
• 2. Lentiform Nucleus- lies below caudate nucleus
• globus pallidus
• putamen

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• 3. Amygdaloid body- lies below the lentiform
  nucleus
• The basal nuclei are involved with the
  subconscious control of skeletal muscle tone and
  coordination of learned movement patterns
• - they do NOT begin a movement, but provide
  pattern and rhythm once a movement is started

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/figure5-31.jpg
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Limbic System

• The LIMBIC SYSTEM includes the olfactory cortex,
  several basal nuclei, gyri, and tracts along the
  border of the cerebrum and diencephalon
• FUNCTIONS
• 1. Establishing emotional states and related
  behavioral drives
• 2. Linking conscious functions of cerebral cortex
  with unconscious functions of brain stem

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• 3. Long-term memory storage and retrieval
• damage to HIPPOCAMPUS that occurs in
  Alzheimers interferes with memory storage and
  retrieval
• The limbic system also includes hypothalamic
  centers that control
• - emotional states- rage, fear, sexual arousal
• - reflex movements that can be consciously
  activated (chewing, swallowing)

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europsych/Downloads/downloadstr/Lect2-opt/limbic2
0system.jpg
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Diencephalon

• The DIENCEPHALON provides switching and relay
  centers that integrate conscious and unconscious
  sensory info. and motor commands
• 3 COMPONENTS
• 1. EPITHALAMUS
• - forms roof of diencephalon
• - contains PINEAL GLAND- endocrine structure that
  secretes the hormone MELATONIN

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• 2. THALAMUS
• - final relay point for all ascending sensory
  info. other than olfactory that will reach our
  conscious awareness
• - acts as a filter, passing on to the primary
  sensory cortex only a small portion of arriving
  sensory info.
• - also plays a role in coordinating voluntary and
  involuntary motor commands

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• 3. HYPOTHALAMUS
• - contains important control and integrative
  centers in addition to those associated with the
  limbic system
• MANY DIVERSE FUNCTIONS
• - subconscious control of skeletal muscle
  contractions associated with rage, pleasure, pain

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• - adjusting activities of autonomic centers of
  pons and medulla oblongata (heart rate, blood
  pressure)
• - secreting hormones
• - producing behavioral drives involved in hunger
  and thirst
• - regulating normal body temperature

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Midbrain

• The 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)

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• 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

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http//www.stanford.edu/group/hopes/rltdsci/trinuc
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Pons

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

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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

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• - 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)

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Medulla Oblongata

• The MEDULLA OBLONGATA connects the brain with the
  spinal cord
• - all communication between the brain and spinal
  cord involves tracts that ascend or descend
  through the medulla oblongata
• CARDIOVASCULAR CENTERS- adjust heart rate,
  strength of cardiac contractions, and flow of
  blood
• RESPIRATORY RHYTHMICITY CENTERS- set basic pace
  for respiratory movements

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PEREPHERAL NERVOUS SYSTEM
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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

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• 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

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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

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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

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• 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

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http//anatomy.med.umich.edu/modules/spinal_cord_m
odule/Files/SC_cnspnsimg.jpg
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http//www.stephblog.com/dermatomes.jpg