C H A P T E R 2

THE BRAIN

2 NERVOUS SYSTEMS

• Central Nervous System (CNS)- Made up of the nervous tissue of the brain and spinal cord.

• Peripheral Nervous System (PNS)- Includes all nervous tissue in the periphery of the body.

PERIPHERAL NERVOUS SYSTEM

• Nerves are unidirectional (only move one way).• 2 types of nerve fibers in the periphery:• Afferent- Nerves carry sensory info. from the environment in towards the CNS. (input)• Efferent- Nerves carry processed info. out from the CNS to the muscles. (output)

DIVISIONS OF THE PNS

• 2 divisions of the PNS:• Autonomic nervous system (ANS)• Somatic nervous system (SNS) soma means

body

ANS- includes nerves that originate in the CNS and stop at the heart, blood vessels, smooth muscle tissue and glands. Runs on autopilot.SNS- Includes the afferent and efferent nerves that bring sensory info in and motor info out of the CNS

CENTRAL NERVOUS SYSTEM (CNS)

• Spinal Cord- Contains nerves that “short circuit” sensory info and motor info allowing rapid spinal reflexes.

•Most motor behavior involves the action of efferent nerves originating in the spinal cord

CROSS SECTION OF THE SPINE

SPINAL CORD

• White Matter- Fat coated nerve tissue. Helps neurons work better. Myelin wraps the neurons to protect them and make them work faster (like an insulator).

• Gray Matter- Nerve tissue found wrapped inside white matter. Not coated by myelin. More fragile and slow.

GRAY MATTER

•Not as durable as white matter.• The color difference between white and gray matter has to do with the myelin making the white matter brighter.•Multiple Sclerosis- Immune system starts stripping away the white matter and destroying it.

THE BRAIN

BRAIN COMPARISONS

BRAIN

•Aside from spinal reflexes, all behavior involves the brain.

•The brain has evolved through the process of Natural Selection.

3 PARTS OF THE BRAIN

•The Hindbrain- The oldest part of the brain•The Midbrain•The Forebrain- The wrinkled part• Subcortical• Cortex

THE HINDBRAIN

THE HINDBRAIN

• Controls basic bodily functions that any living thing need to survive.• The oldest part of the brain.• 3 Major Parts:• Medulla Oblongata- blood circulation, breathing,

muscle tone, salivation, gagging, coughing, sneezing.• Pons- sleep and arousal, connects brainstem

and cerebellum.• Cerebellum- Coordinated movement and

balance.

THE MIDBRAIN

THE MIDBRAIN

• Home to the Superior and Inferior Colliculi• Superior- Helps you know where things are

located in space (vision).• Inferior- Processes spatial info for the auditory

system (hearing).Substantia nigra (black substance): Critical to control fine motor coordination.

- Destruction of black substance causes Parkinson’s Disease.

THE MIDBRAIN

•Reticular Formation: Sleep and arousal, attention, muscle tone, movement.•Connected to the Pons.

THE FOREBRAIN

THE FOREBRAIN (WRINKLED PART)

• The newest evolutionary development and is most highly developed in primates (especially humans).

• Incredibly complex, it has many structures and interconnections and is the locus (center) of planning and decision-making.

STRUCTURES OF THE FOREBRAIN

• Thalamus- Main pathway for sensory information.• Hypothalamus- Regulates biological drives

(i.e. Hunger)• Limbic system- Seat of emotionality (fear,

aggression)• Houses the hippocampus (memory

storage and retrieval)

THE CORTEX (FOREBRAIN)

•Divided into 4 lobes• Occipital Lobe: Visual center (ocular)• Temporal Lobe: Sound center• Parietal Lobe: Body senses• Frontal Lobe: Motor skillsThe prefrontal lobe is the only part of the human brain that is different than other species. This is likely why that part set us off from other species.

LOBES OF THE CEREBRAL CORTEX