Chapter 2 - The Brain & The Nervous System

Phrenology

Pseudoscience that attributed the moral character of a person to the shape/bumps on their skull

Brain Size in Humans

Compared to our close evolutionary relatives, our cortex is much larger and more layered relative to brain size

The Central Nervous System (CNS)

Brain and Spinal cord

The Peripheral Nervous System (PNS)

Everything Else

The Peripheral Nervous System’s Divisions

Somatic Nervous System and Autonomic Nervous System

Purpose of the Somatic Nervous System

Sensing and musculoskeletal output (motor control; voluntary and involuntary reflexes)

Part 1 of the Somatic Nervous System

Cranial Nerve: 12 nerves that are directly connected to our brain; generally transmit motor and sensory info from the head/face - vagus nerve is the exception that involves internal organ signaling and sensing

Part 2 of the Somatic Nervous System

Spinal Nerves: 31 pairs of nerves that act as the communication pathway between the CNS and the rest of the body - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

Purpose of the Autonomic Nervous System

Controlling involuntary bodily functions (internal organs; regulatory processes)

Part 1 of the Autonomic Nervous System

Sympathetic Division: “fight or flight”

• releases noradrenaline/norepinephrine;

• signals via a ganglion near the spinal cord

Part 2 of the Autonomic Nervous System

Parasympathetic Division: “rest and digest”

• releases acetylcholine

• signal via a ganglion near target organ

Anatomical Planes of the Brain

Horizontal Plane, Sagittal Plane, and Coronal Plane

Anat Term: Medial

towards the middle

Anat Term: Lateral

towards the outside

Anat Term: Rostral

towards the front

Anat Term: Caudal

towards the back

Anat Term: Dorsal

towards the top

Anat Term: Ventral

towards the bottom

Brain Organization: Cortex

Thick outermost layer of gray matter on the brain;

Contains two hemispheres connected by the corpus callosum, with each hemisphere carrying 4 lobes

Cortex Surface features

Gyri (gyrus): rounded ridges of the cortex;

Sulci(sulcus): furrowed grooves between the gyri

Cortex: red lobe

Frontal Lobe

Cortex: blue lobe

Parietal Lobe

Cortex: green lobe

Temporal Lobe

Cortex: purple lobe

Occipital Lobe

Brain Organization: Diencephalon

Thalamus: sensory processing unit with over 50 individual regions;

Hypothalamus: maintains internal body balance (homeostasis)

Brain Organization: Brainstem

Midbrain: aids in motor control and sensory processing;

Pons: regulates circadian rhythm, arousal, and basic sensory functions;

Medulla: involves critical involuntary function that support life (breathing, heart rate, etc.)

Brain Organization: Cerebellum

Coordinates voluntary movement and balance;

Contains more neurons than the cortex

Brain Organization: The Cerebral Ventricles

4 empty, fluid-filled venticles;

Lateral ventricles (2), third ventricle, and fourth ventricle;

Keeps the brain cushioned in cerebral spinal fluid

Brain Organization: The Cerebrovascular System

3 major arteries (anterior, middle, and posterior) supply blood to the brain;

Blood flow to the brain is tightly regulated by the blood brain barrier

Stroke

Occurs when flood flow to the brain is disrupted;

Hemorrhagic Stroke: a vessel has burst to let blood leak;

Ischemic Stroke: a clog has blocked blood flow

Brain Organization: The Glymphatic System

Brain’s drainage system to clear waste and debris