The Human Brain
• Ranges from 750 cc to 2100 cc
• Contains almost 98% of the
body’s neural tissue
• Average weight about 1.4 kg (3
lb)
Motor Cortex
1
2
Sensory Cortex
3
Frontal Lobe
Parietal Lobe
4
5
Temporal Lobe 6
Occipital Lobe
7
Reticular Activating System 8
9
Cerebellum
Spinal Cord
three layers of meninges around the brain and spinal cord.
• 1. Cerebrum
–
–
–
–
Largest part of brain
Controls higher mental functions
Divided into left and right cerebral hemispheres
Surface layer of gray matter (neural cortex)
• Neural Cortex
– Also called cerebral cortex
– Folded surface increases surface area
– Elevated ridges (gyri)
– Shallow depressions (sulci)
– Deep grooves (fissures)
• 2. Cerebellum
–
–
–
–
Second largest part of brain
Coordinates repetitive body movements
2 hemispheres
Covered w/ cerebellar cortex
• 3. Diencephalon
– Located under cerebrum and cerebellum
– Links cerebrum with brain stem
4. Mesencephalon
Also called midbrain
Processes sight, sound, and associated reflexes
Maintains consciousness
The Diencephalon
• Thalamus, epithalamus, and hypothalamus
• Integrates sensory information and motor
commands
• Pineal Gland in posterior
epithalamus
– Secretes hormone melatonin
• Thalamus Post Office
– Filters ascending sensory
information for primary
sensory cortex
Figure 14–5a
thalamus(80 % of diencephalon), hypothalamus, & epithalamus.
Brain Structure: Hindbrain
• Hindbrain (Old Brain)
• (Reptilian Brain)
– Spinal cord, lower brain
stem, and cerebellum
• Medulla Oblongata
– Located where the spinal
cord enters the skull
– Breathing, posture
Brain Structure: Hindbrain
• Cerebellum
– Extends from rear of
hindbrain
– Motor control
• Pons
– Bridge in hindbrain
– Sleep and arousal
Brain Structure: Midbrain
• Midbrain
– Between midbrain & forebrain
– Relays information between the
brain and eyes/ears
• Reticular Activation System
•
RAS
– Stereotyped patterns of
behavior
– Walking, sleeping, automatic
functions
Basal ganglia
Starting and stopping voluntary moveme
Brain Structure: Limbic System
Instinctual Brain
• Limbic system
– Plays an important role in
both memory and emotion
• Amygdala
– Discrimination of objects and
emotion Angry Amy
• Hippocampus
– Storage of memories
–
BIG Campus Library!
Brain Structure
• Hypothalamus
– Monitors eating,
drinking, sex,
temperature
– Helps direct the
endocrine system
through the pituitary
gland
– Involved in emotion,
stress, and reward
8 Functions of the Hypothalamus
1.
2.
3.
Provides subconscious control of skeletal muscle
Controls autonomic function
Coordinates activities of nervous and endocrine systems
4.
Secretes hormones: ADH(Antidiuretic) & OT (Oxytocin)
5.
Produces emotions and behavioral drives:
– the feeding center (hunger)
– the thirst center (thirst)
6.
7.
Coordinates voluntary and autonomic functions
Regulates body temperature:
8.
Controls circadian rhythms (day–night cycles):
Sensory Areas
• Postcentral gyrus of parietal lobe:
– receives somatic sensory information (touch, pressure,
pain, vibration, taste, and temperature)
• Primary sensory cortex:
– surface of postcentral gyrus
• Visual cortex:
Central sulcus
separates motor
and sensory areas
– information from sight receptors
• Auditory cortex:
– information from sound receptors
• Olfactory cortex:
– information from odor receptors
• Gustatory cortex:
– information from taste receptors
Neocortex..NEWBRAIN
• Occipital lobe
..SIGHT
– Back of the head
– Vision
• Temporal lobe
– Just above the ears
– Hearing,Speech
• Frontal lobe
Neocortex
– Behind the forehead
– Purposeful control of
voluntary muscles
– Intelligence, Cognition
• Parietal lobe
– Top of the head, toward the
rear
– Processing bodily
sensations
– Motor Cortex
– Somatosensory Cortex
Left
Hemisphere
Language,
Linear,
Logical
Corpus
Callosum
Right
Hemisphere
Radical,
Religious,
Random,
Roundabout
ways
Brain Protection and Support
• Physical protection:
– bones of the cranium
– cranial meninges
– cerebrospinal fluid
• Biochemical isolation:
– blood–brain barrier
• Cranial Meniges - 3 layers:
– dura mater
– arachnoid mater
– pia mater
• Is continuous with spinal meninges
• Protects the brain from cranial trauma
4 Breaks in the BBB
1. Portions of hypothalamus:
–
secrete hypothalamic hormones
2. Posterior lobe of pituitary gland:
–
secrete hormones ADH and oxytocin
3. Pineal glands:
–
pineal secretions
4. Choroid plexus:
–
where special ependymal cells maintain blood–CSF
barrier
Brain Damage
• Plasticity
– The brain’s capacity to
modify and reorganize itself
following damage
• Collateral sprouting
– Axons of healthy neurons
adjacent to damaged cells
grow new branches
• Substitution of function
– Damaged region’s function
is taken over by another
area, or areas, of the brain
Phineas Gage
Studying the Brain
• Electroencephalograph (EEG)
– Records the electrical activity of the brain
• Computer-assisted axial tomography (CAT
scan)
– 3D imaging obtained from X rays of the head
• Magnetic resonance imaging (fMRI)
– Magnetic field around the body
• PET Positron Emission Tomograpy
Color images of “hot & cold” actions
The Endocrine System
Endocrine Glands
Release their chemical
products, called hormones,
directly into the
bloodstream
Pituitary gland
– Controls growth and
regulates other glands
Adrenal glands
– Play an important role in
our moods, energy level,
and ability to cope with
stress
Thyroid Gland –Growth
Gonads – Sex Characteristics
Autonomic nerves (in
blue)--sympathetic and
parasympathetic--regulate
much of the body without
our conscious knowledge.
Sympathetic nerves
branch from spinal nerves
(in white) and form a chain
of ganglia that sends
fibers to the organs.
Parasympathetic nerves,
including the important
vagus, usually reverse the
action of sympathetic
ones.