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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