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 Sensory Cortex

Frontal LobeParietal Lobe

Temporal Lobe

Occipital Lobe

Cerebellum

Reticular Activating SystemSpinal Cord

1 2

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5

6 7

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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 midbrainProcesses sight, sound, and associated reflexesMaintains consciousness

Figure 14–5a

The Diencephalon

• Integrates sensory information and motor commands

• Thalamus, epithalamus, and hypothalamus

• Pineal Gland in posterior epithalamus– Secretes hormone melatonin

• Thalamus Post Office

– Filters ascending sensory information for primary sensory cortex

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 gangliaStarting and stopping voluntary movements

Brain Structure: Limbic SystemInstinctual 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. Provides subconscious control of skeletal muscle

2. Controls autonomic function

3. 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. Coordinates voluntary and autonomic functions

7. 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: – information from sight receptors

• Auditory cortex: – information from sound receptors

• Olfactory cortex: – information from odor receptors

• Gustatory cortex: – information from taste receptors

Central sulcus separates motor and sensory areas

Neocortex..NEWBRAIN

• Occipital lobe ..SIGHT– Back of the head

– Vision

• Temporal lobe– Just above the ears

– Hearing,Speech

Neocortex• Frontal lobe

– 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 HemisphereLanguage,

Linear, Logical

Right Hemisphere

Radical, Religious, Random,

Roundabout ways

Corpus Callosum

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 BBB1. 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.