Central nervous system (CNS) brain and spinal cord enclosed in bony coverings

Functions of the spinal cord spinal cord reflexes integration (summation of inhibitory and

excitatory) nerve impulses highway for upward and downward travel of

sensory and motor information Brain functions

sensations, memory, emotions, decision making, behavior

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Respond to stimuli: nerve endings (dendrites of neurons) sense organs (taste)

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Afferent neurons somatic and visceral sensory neurons

Sensory Pathway (PNS)

Efferent neurons Stimulate and control effectors

somatic motor neurons visceral motor neurons

Autonomic Nervous System (ANS)• Sympathetic• Parasympathetic

They both control the same effectors (with few exceptions) but have opposite responses in the effectors

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Information highway between brain and body Each pair of spinal nerves receives sensory

information and issues motor signals to muscles and glands

Spinal cord is a component of the CNS while the spinal nerves are part of the PNS

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Conduction bundles of fibers passing information up and

down spinal cord Locomotion

repetitive, coordinated actions of several muscle groups

central pattern generators are pools of neurons providing control of flexors and extensors (walking)

Reflexes involuntary, stereotyped responses to stimuli

(remove hand from hot stove) involves brain, spinal cord and peripheral nerves14-5

Cylinder of nerve tissue within the vertebral canal (thick as a finger) vertebral column grows faster so in an adult the

spinal cord only extends to L1 31 pairs of spinal nerves arise from cervical,

thoracic, lumbar and sacral regions of the cord each cord segment gives rise to a pair of spinal

nerves

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3 Fibrous layers enclosing spinal cord Dura mater

tough collagenous membrane surrounded by epidural space filled with fat and blood vessels

epidural anesthesia utilized during childbirth

Arachnoid mater layer of simple squamous epithelium lining dura

mater and loose mesh of fibers filled with CSF(creates subarachnoid space)

Pia mater delicate membrane adherent to spinal cord

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Central area of gray matter shaped like a butterfly and surrounded by white matter in 3 columns

Gray matter = neuron cell bodies with little myelin White matter = myelinated axons

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Pair of dorsal or posterior horns dorsal root of spinal nerve is totally sensory fibers

Pair of ventral or anterior horns ventral root of spinal nerve is totally motor fibers

Connected by gray commissure punctured by a central canal continuous above with 4th ventricle

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White column = bundles of myelinated axons that carry signals up and down to and from brainstem

3 pairs of columns or funiculi dorsal, lateral, and anterior columns

Each column is filled with named tracts (fibers with a similar origin, destination and function)

Ascending and descending tract head up or down Contralateral means origin and destination are on opposite sides

while ipsilateral means on same side

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Automatic response to change in environment Integration center for spinal reflexes is gray

matter of spinal cord Examples

somatic reflexes result in skeletal muscle contraction autonomic (visceral) reflexes involve smooth &

cardiac muscle and glands. heart rate, respiration, digestion, urination, etc

Reflexes can be: simple

involve peripheral nerves and the spinal cord spinal reflexes

learned (acquired) involve peripheral nerves and the brain

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Specific nerve impulse pathway 5 components of reflex arc

Receptor Registers stimuli

Sensory neuron Transmits stimuli to the CNS

Integrating center Part of the CNS that processes the information and

generates response Motor neuron

Transmits the response to the effector Effector

Muscle or gland 4 important somatic spinal reflexes

stretch, tendon, flexor(withdrawal) & crossed extensor reflexes

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Longitudinal fissure - cerebral hemispheres. gyri = folds; sulci = grooves cortex = surface layer of gray matter nuclei = deeper masses of gray matter tracts = bundles of axons (white matter)

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Gray matter = neuron cell bodies, dendrites, and synapses forms cortex over cerebrum and

cerebellum forms nuclei deep within brain

White matter = bundles of axons forms tracts that connect parts of brain

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Internal chambers within the CNS lateral ventricles in cerebral hemispheres third ventricle = single vertical space under

corpus callosum cerebral aqueduct runs through midbrain fourth ventricle = chamber between pons

and cerebellum central canal runs down through spinal

cord Lined with ependymal cells Choroid plexus produce CSF 14-20

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Fills ventricles and subarachnoid space Brain produces and absorbs 500 ml/day

choroid plexus creates by filtration of blood Functions

floats brain so it is neutrally buoyant cushions from hitting inside of skull chemical stability -- rinses away wastes

Escapes (4th ventricle) to surround brain Absorbed into venous sinus by arachnoid

villi14-22

Cardiac center adjusts rate and force of heart

Vasomotor center adjusts blood vessel diameter

Respiratory centers control rate and depth of breathing

Reflex centers for coughing, sneezing, gagging,

swallowing, vomiting, salivation, sweating, movements of tongue and head

Most of the fibers are crossing over Left cortex controls right side of body

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Bulge in brainstem, superior to medulla

Ascending sensory tracts Descending motor tracts Pathways in and out of

cerebellum

Nuclei concerned with posture, sleep,

hearing, balance, taste, eye movements, facial expression, facial sensation, respiration, swallowing, and bladder control

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Two hemispheres connected by vermis

Cortex = surface folds called folia

Output comes from deep gray nuclei granule and purkinje cells

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White matter (arbor vitae) visible in sagittal section

Evaluation of sensory input coordination and locomotor

ability spatial perception

Timekeeping center predicting movement of

objects

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Tegmentum connects to cerebellum

and helps control fine movements through red nucleus

Substantia nigra sends inhibitory signals

to basal ganglia and thalamus (degeneration leads to tremors and Parkinson disease)

Central gray matter = pain awareness

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Scattered nuclei in medulla, pons & midbrain

Reticular activating system alerts cerebral cortex to sensory

signals (sound of alarm, flash light, smoke or intruder) to awaken from sleep

maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles

Motor function is involvement with maintaining muscle tone

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Thalamus Functions Relays signals from cerebellum

to motor cortex Emotional and memory functions

Hypothalamus Functions hormone secretion autonomic NS control thermoregulation food and water intake (hunger

and satiety) sleep and circadian rhythms memory (mammillary bodies) emotional behavior

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Cerebral cortex - 3mm layer of gray matter extensive folds increase surface area - divided into lobes

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Frontal voluntary motor functions planning, mood, smell and social judgement

Parietal receives and integrates sensory information

Occipital visual center of brain

Temporal areas for hearing, smell, learning, memory,

emotional behavior 14-31

Most of cerebrum is white matter

Types of tracts projection tracts

from brain to spinal cord, forms internal capsule

commissural tracts cross to opposite hemisphere

corpus callosum anterior and posterior

commissures association tracts

connect lobes and gyri within a hemisphere

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Loop of cortical structures amygdala, hippocampus and cingulate gyrus

Role in emotion and memory pleasure and aversion centers 14-33

Information management requires learning, memory and forgetting

Amnesia anterograde amnesia - no new memories retrograde amnesia – can’t remember old

ones Hippocampus

organizes sensory and cognitive information into a new memory

Cerebellum – helps learn motor skills Amygdala - emotional memory

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Visceral motor neurons control heart rate breathing rate digestion blood pressure salivation

Nerve impulses of these motor neurons start in the CNS (medulla oblongata and pons) Pathway through:

Spinal cord Cranial nerves

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The sympathetic division is called the “fight or flight” system when the body needs to generate energy

exercise, excitement, emergency, and embarrassment

Fight or flight response increases heart rate, blood pressure, respiration

rate, blood flow to skeletal muscles, glucose metabolism

decreases the activities that are not essential at the moment (digestive system organs are subdued- decreased blood flow to that system

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The parasympathetic division is called the “rest and digest” activated when the body needs to conserve

energy digestion, defecation, and diuresis (urination)

Promotes necessary changes during these activities decreases heart rate, blood pressure, respiration

rate, blood flow to skeletal muscles, glucose metabolism

increases the activity of and blood flow to the digestive system organs

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The cells of each organ controlled by the ANS have both ACh and NE receptors organs are dually controlled

The response of the organ is determined by the identity of the neurotransmitter released the binding of ACh to its receptor will cause the

effector to respond in one way the binding of NE to its receptor will cause the

effector to respond in the opposite way The effect of ACh and NE is effector specific

NE increases heart rate, ACh decreases heart rate NE decreases the secretion of saliva, ACh increases

the secretion of saliva

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