The Brain and Cranial Nerves

The Brain –Introduction –Development of brain  Embryology –Anatomy of brain  Parts and functions

The Brain

Introduction to the Brain –Weighs about 3 lbs. in adults –Structures  Divided into 3 general areas –Functions  Controls the bare necessities of life  Location for primal drives and emotions  Intellectual thought, imagination, perception, interpretation, etc.

Human Development –First two weeks – neural tube forms –4 th week - anterior end of the neural tube forms the  forebrain  midbrain  hindbrain

Embryology – 3-4 Weeks

Embryology – 4 Weeks

Embryology – 5 Weeks

Embryology – 11 Weeks

A Child’s Brain

Adult Brain –Forebrain  Cerebrum  Thalamus & hypothalamus –Midbrain –Hindbrain  Cerebellum & pons  Medulla oblongata

Adult Brain

Protections and Coverings –Cranial bones – strong support –Cranial meninges – shock absorbers  Dura mater  Arachnoid  Pia mater

The Cranial Meninges

The Ventricles of the Brain –Hollow areas within the brain  Connect to spinal canal and space around the brain –Cerebrospinal fluid circulates around the brain, down through the ventricles, and into the spinal cord.

Ventricles of the Brain

Cerebrospinal Fluid –Composition  Clear, colorless, watery  Contains proteins, glucose, urea, salts  Contains white blood cells –Functions  “Floats” the brain  Medium of transport

Circulation of Cerebrospinal Fluid

Problems Associated with CSF –Hydrocephalus –Meningitis –Headaches

Hydrocephalus

Blood-Brain Barrier –A function of glial cells  Secrete chemicals that maintain the BBB  Absorb materials from blood  Extract materials from brain –Cells of capillaries form tight junctions –Differential rates of passage of certain materials

Blood-Brain Barrier

The Parts of the Brain Forebrain Cerebrum, Hypothalamus, Thalamus

Cerebrum – Gray & White Matter –Outer layer – cerebral cortex  Gray matter –Inner portion  White matter  Masses of gray matter – cerebral nuclei

Cerebrum – Gray & White Matter

Cerebral Cortex –Gyri are separated by grooves (sulci)  Fissures – deeper grooves –Divided into cerebral hemispheres

Gyri & Sulci

Cerebral Cortex –Divided into lobes –Well mapped  Decision-making, planning, personality  Primary motor cortex  Primary sensory cortex

Cerebral Lobes

Homunculus Primary Motor CortexPrimary Sensory Cortex

Cerebral Nuclei –Collections of cell bodies (gray matter) –Mostly control the movement of skeletal muscles

Cerebral Nuclei

Limbic System –Functional unit (not anatomical) –Emotional part of the brain  Feelings of fear, loss, love, rage, etc. –Includes parts of several anatomical structures  Cerebrum  Hypothalamus  Thalamus

Limbic System

Hypothalamus –Initiates primal drives  Hunger, thirst, sex, rage, etc.  Controls autonomic nervous system –“fight or flight” sympathetic response. –Controls pituitary gland (“master gland” of endocrine system)  Infundibulum (“funnel”) funnels secretions to the pituitary gland

Hypothalamus –Location – under thalamus –Structure  Clusters of nerve cell bodies –Autonomic centers  Infundibulum

Hypothalamus

Thalamus –Functions as a relay station between the body and the cerebral cortex  Inform us of our emotional state  Relay information concerned with motor requirements & actions  Integrate visual and auditory reflexes

The Thalamus

Thalamus

Epithalamus –Location  Above thalamus –Contains the pineal body  Secretes melatonin

Midbrain

Midbrain –Relay station –Tracts of motor and sensory neurons –Contains nuclei  Substantia nigra secretes dopamine –Modifies muscle tone & motor activity –Parkinson’s disease

Midbrain

Hindbrain Cerebellum, Pons, & Medulla Oblongata

Cerebellum –2 nd largest structure of the brain –Divided into 2 lateral hemispheres –Cortex – gyri & sulci  Gray matter –Interior  White matter –Cerebellar nuclei – deep within white matter  Gray matter

Cerebellum –Functions – controls subconscious movements in skeletal muscle  Coordination  Posture  Balance

Cerebellum, Pons, Medulla Oblongata

Pons –Pons = “bridge”  Connects the spinal cord with the brain and parts of the brain with each other  Consists mostly of white fibers –Functions  Controls respiration rate (with medulla)

Medulla Oblongata –Continuation of spinal cord –Functions  Maintains wakefulness and alertness  Contains reflex centers –Cardiac center, vasomotor center, respiratory rythmicity center –Other nonvital centers

Medulla Oblongata

Cranial Nerves

Introduction to Cranial Nerves –12 pairs –Leave the skull through foramina –Types  Mixed  Sensory  Motor –Part of the somatic nervous system –Innervate organs in head, neck and upper thorax

The Cranial Nerves