Anatomy of the Brain

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Overview

• Size: ~ 3 pounds (~size of 2 fists)

• Appearance: pinkish gray & wrinkled with a texture of cold oatmeal

• # of Neurons: ~100 billion

Miscellaneous Facts

• Brain = organ

• Mind = abstract mental activity

• Most of what we know of brain & mind learned through animal experiments and studying people with disease or head trauma

• The brain has no pain receptors

Basic Definitions

• Ventricles - cavities in the brain that contain CSF

• Gyri (“twisters”) - elevated ridges of

brain tissue• Sulci (“furrows”) - shallow grooves in

brain tissue• Fissures - deep grooves that separate large

regions of the brain

Basic Definitions (cont.)• Center - group of functionally related neurons

that may or may not be closely grouped

• Tract - a bundle of axons in the CNS that have the same origin & function

• Basal nuclei - “islands” of gray matter located deep within the white matter of the cerebral hemispheres; help regulate voluntary motor areas

4 Major Parts of the Brain

• There are 4 major parts: cerebrum, diencephalon (interbrain), brainstem, & cerebellum

Parts of the Brain

1. Cerebrum - largest part of brain ~2 lbs.

a. Consists of right & left

hemispheres, separated by a

longitudinal fissure

Parts of the Brain

1. Cerebrum - largest part of brain ~2 lbs.

b. Contains the corpus callosum:

a large fiber tract that connects

the right & left hemisphere

(Split-brain experiments)

Parts of the Brain

c. Lobes of each cerebral hemisphere

1. Frontal - speech, voluntary

movement, & personality

Video Clip

• Phineas Gage Story

Parts of the Brain

c. Lobes of each cerebral hemisphere

2. Parietal - interprets sensory functions such as touch (hot, cold, pain, pressure, & position of other body parts)

Parts of the Brain

c. Lobes of each cerebral hemisphere

3. Occipital - interpretation of vision

4. Temporal - interpretation of hearing,

smell, & taste

Parts of the Brain

d. Cerebral cortex: - layer of gray matter that covers the cerebrum - highly wrinkled to increase surface area

-main area of judgment, intelligence, creativity, memory, learning, & reasoning

(Contains Broca’s area & Wernicke’s area - important speech centers)

Parts of the Brain

2. Diencephalon (Interbrain) - enclosed by the cerebral hemispheres and sits on top of the brain stem

a. Thalamus - relay station for sensory impulses (recognize whether a sensation being passed along is pleasant or unpleasant)

Parts of the Brain b. Hypothalamus (“under the thalamus”)

-responsible for autonomic/visceral control such as regulating body temperature, water balance, & metabolism

-Limbic system “emotional-visceral brain”: controls hunger, thirst, sex, pain, & pleasure centers

-Also allows for physical expression of

emotion-Regulates the pituitary gland

Parts of the Brain

c. Epithalamus - contains the pineal body (part of endocrine system) and a choroid plexus (helps form CSF)

Parts of the Brain3. Brainstem - ~3 inches long & thumb size in diameter

a. Midbrain - contains visual & auditory centers

& nerve pathway crossing

b. Pons (“bridge”) - responsible for autonomic functions such as respiration, jaw movement, & facial senses

Parts of the Brainc. Medulla oblongata - enlarged continuation of

spinal cord; respiratory & cardiac control; autonomic reflexes such as sneezing, coughing, blinking, swallowing, & vomiting

*Reticular Activating System (RAS) - sleep/wake cycle

Lack of dreams = heading for severe psychological disturbanceLack of sleep = may result in insanity &/or death

Parts of the Brain4. Cerebellum - 2nd largest part of brain; cauliflower-like structure

-is also divided into right & left hemispheres

-controls balance, posture, muscle tone, & coordination of movement

Parts of the Brain

*Ataxia - damage to cerebellum (blow to head, tumor, stroke); movements are clumsy & disorganized; victims appear drunk due to loss of muscle coordination; cannot touch finger to nose with eyes closed

Review Song

• Parts of the Brain Song

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