Nervous Part 2

Neural Tube

Secondary Primary

PRIMARY SECONDARY

Forebrain (Prosencephalon)• Telencephalon = Cerebrum• Diencephalon

Midbrain (Mesencephalon)Hindbrain (Rhombencephalon)

• Metencephalon = Pons & Cerebellum

• Myelincephalon = Medulla Oblongata

Ventricles

4 Ventricles2 lateral ventricles

• 1st ventricle in left cerebrum• 2nd ventricle in right cerebrum

• 3rd ventricle surrounds diencephalon• 4th ventricle within brainstem

• Filled with CSF- Cerebral Spinal Fluid

Reflex Arc

Reflex Arc• 1. Receptor• 2. Afferent neuron – through dorsal root

(Sensory)• 3. Interneuron- within CNS• 4. Efferent neuron – through ventral root

(Motor)• 5. Effector

Medulla Oblongata (Myelincephalon)a. Descrete nuclei

i. Cardiac center – regulates heart rateii. Vasomotor center – regulates blood pressureiii. Respiratory center – regulates rate of breathing

Medullary Pyramids

PYRAMIDS

Site of decussation (crossing over) for 90% of motor or descending neuronsa. Right brain controls movement in left hand

Olives = Passage for neuron fibers to cerebellum

Pons

“bridge” – (ventral portion of metencephalon)• a. Ventral aspect = pontine nuclei that

connect cerebellum to cerebrum• b. Dorsal aspect = connects cerebellum to

cerebrum

Cerebellum(dorsal portion of metencephalon)

a. Over 10 trillion neurons in cerebellar cortex, more than cerebral cortexb. Functions:

1. Balance & Posture2. Coordinates motor activity3. Learning & Practicing, such as playing an instrument

Cerebellum

1. Purkinje cellsa. Largest cells in CNSb. Over 200,000 synapses per cellc. Gateway out of cerebellum

Dentate nucleia. Proprioception & balance

1. Middle peduncle a. cerebral impulses send motor impulses to body for voluntary movementsb. A copy of cerebral impulse is sent to dentate nucleus in cerebellum

2. Inferior pedunclea. Sensory impulses of body’s position, following movements, is sent to dentate nucleus from medullab. Dentate nucleus compares actual movements and “desired position”

3. Superior peduncle a. If actual movement is different from “desired position” the dentate nuclei send corrective impulses into midbrain towards cerebral cortex

IV. Midbrain (mesencephalon)a. Posterior Surface

i. Corpora quadrigemina (body of 4 twins)1. Superior colliculi

a. visual reflexesb. eg. tracking a tennis ball or turning to see a lightning flash

2. Inferior colliculi

a. Auditory reflex b. Transmits auditory signals to thalamus

ii. Substantia nigra 1. involved in coordinating voluntary movements & muscle tone2. Secretes dopamine (inhibitory effect)3. Communicates with Basal Nuclei of cerebrum4. Parkinson’s disease = degeneration of substantia nigra

a. Tremors at rest

Diencephalon

DIENCEPHALONDiencephalon = Thalamus, Epithalamus, Hypothalamusa. Thalamus

i. Structure = yo-yo like shape. Surrounded by 3rd ventricleii. Functions

1. Sensory relay centera. All sensory neurons (except olfaction) synapse in thalamusb. Thalamus relays impulses to appropriate areas of cerebrumc. Example:

i. Lateral geniculate nucleus relays visual impulses to visual cortex.Influences moods, such as fear & rage

Hypothalamusi. Highly dense population of nucleiii. Functions

1. Regulates body temperature2. Regulates heart rate3. Hunger4. Thirst5. Sex drive6. Affects mood & emotions7. Produces hormones

Epithalamus- Pineal Gland

Epithalamusi. Pineal Gland1. Secretes Melatonin – regulates sleep/wake cycle

Cerebrum

Cerebrum (Telencephalon)

a. Basal Nuclei (deep cerebrum)1. Caudate nucleus2. Putamen3. Globus pallidus

 ii. Functions of Basa Nuclei

1. Controls voluntary movement2. Produces dopamine = inhibitory effect3. Interacts with substantia nigra

Corpus Callosum•i. Bridge of nerve fibers that connects left & right cerebral hemispheres

Surface of Cerebrum1. Structure

a. Gyri (gyrus = sing.) – bumpsb. Sulci (sulcus – sing.)- grooves

2. Cerebral cortexa. Outer layerb. Grey matter = cell bodiesc. Contains 75% of all cell bodies in nervous system

3. Cerebral Medullaa. Deeper layerb. White matter = myelinated axonsc. Connects cortex to rest of CNS

Frontal Lobe

1. Frontal Lobea. Voluntary motor movementsb. Broca’s Area – coordinates mouth, tongue, and pharynx = motor speechc. Frontal eye field – voluntary movements of eyesd. Prefrontal cortex

i. Planningii. Complex problem solvingiii. Judgmentiv. Decision making

Parietal Lobea. Receives & evaluates most sensory information

i. Includes: taste, touch, pain, temperature, posture, pressure, ect.ii. Excludes: hearing, smell, and vision

b. Wernike’s Areai. Relays input from visual & auditory cortexii. Important for understanding written or spoken language

Occipital Lobea. Receives, integrates, and interprets visual inputVisual association area- such as recognizing a person

Temporal Lobea. Input for smell & hearingb. Role in auditory & visual memory

Limbic System

Limbic System

a. Functionsi. Memoryii. Reproductioniii. Emotions (anger, fear, pleasure, sorrow)iv. Hunger & feeding

Structures of the Limbic System

Cingulate Gyrus

Satisfaction center –a. feeling satisfied after a meal or sexual intercourseb. damaged = voracious appetite or high sex drive

Hippocampus

Hippocampus “Seahorse”

1. Within deep temporal lobe2. Retrieving short-term memory & spatial cognition

a. Remembering a person you metb. Remembering where you placed your keys3. Hippocampus is first to deteriorate in Alzheimer’s disease

Amygdala “almond-shaped”

Amygdala1. Involved in emotions 2. Emotional memory

a. Hippocampus helps you remember a person, and the amygdala attaches emotions to that memory (like or dislike a person)b. Feeling of fears such as heights, or when hearing a smoke detector alarmc. Amydala triggers emotions, and the cerebral cortex must override the emotions (rational thought) d. Example: Walking across a bridge

Amygdala triggers a sense of fear from the heightCerebral cortex rationalizes that it’s safe to cross the bridge

3. Disordersa. Depressionb. Anxietyc. Obsessive-compulsive disordersd. Phobias

Cranial NervesI. olfactory Nerves = smellII. optic Nerves = visionIII. oculomotor Nerves = eye movementIV. trochlear Nerves = eye movementV. trigeminal nerves= sensory & motor to faceVI. abducens nerves= eye movementVII. facial nerves = sensory & motor to faceVIII.vestibulocochlear nerves = hearing & balanceIX. glossopharyngeal nerves = pharynx & tongueX. vagus nerves = lungs, heart, blood vessels, stomach, ect.XI. accessory nerves = muscles of shoulders & neck, pharynx & larynxXII. hypoglossal nerves = movement of tongue