A&p Chapters 11-13

1. Sensory input

2. Motor output

3. Integration

Brain and spinal cord. Integration and command center.

Paired spinal and cranial nerves. Carries messages to and from the spinal cord and brain.

Collection of nerve cell bodies outside the CNS

1. Sensory (afferent) division

•somatic sensory division - carry

impulses from skin, skeletal

muscles, and joints to the brain

•visceral sensory division -

transmit impulses from visceral

organs to the brain

2. Motor (efferent) division

•transmits impulses from the CNS

to effector organs

Supporting cells. Function as scaffolding for neurons.

1. Oligodendrocytes - CNS

2. Ependymal cells - CNS

3. Microglia - CNS

4. Astrocytes - CNS

5. Schwann cells - PNS

6. Satellite cells - PNS

Branched cells that wrap CNS nerve fibers (form myelin sheath in the CNS)

Line the central cavities of the brain and spinal column. These cells produce cerebrospinal fluid in the choroid plexus and contains cilia that help with the flow of CSF.

Small, ovoid cells with spiny processes that function as phagocytes that monitor the health of neurons. Clusters of microglia may indicate the site of an injury.

Most abundant. Act as scaffolding. Cover, support, and brace neurons. Astrocytosis - replaces damaged neurons with scar tissue or sclerosis.

Surround nerve fibers in PNS - myelin. (Same function as oligodendrocytes in CNS)

Surround neuron cell bodies in ganglia in PNS

Whitish, fatty, protein lipid segmented sheath around long axis. Formed by Schwann cells in the PNS and oligodendrocytes in CNS. Functions to protect axon, electrically insulate fibers, and increase speed of nerve impulse transmission.

Remaining nucleus and cytoplasm of a Schwann cell

The myelin covered segments

Gaps in myelin sheath between adjacent Schwann cells.

1. Excitability (irritability) - able to respond to stimuli

2. Conductivity - passing electrical signals to other cells at distant locations

3. Secretion - neurotransmitters are chemical messengers in axon terminals

1. Sensory (afferent) - transmit impulses toward the CNS

2. Interneurons (association neurons) - shuttle signals through CNS pathways

3. Motor (efferent) - carry impulses always from the CNS

1. Composed of a body (soma), axon, and dendrites

•Dendrites bring info in, axons

send info out.

2. Long-lived, amitotic, and have a high metabolic rate.

Contains nucleus and nucleolus and is the major biosynthetic center.

Armlike extensions from the soma. Called tracts in the CNS and nerves in the PNS. There are two types: axons and dendrites.

Long axons

1. Multipolar - three or more processes (most common - 99% of all neurons)

2. Bipolar - two processes (axon and dendrite) (found in special senses)

3. Unipolar - single, short process sensory neurons (found in sensory pathways)

4. Anaxonic - multiple dendrites but no axon. Do not produce action potentials - found in brain, retina, and adrenal medulla.

1. generate and transmit action potentials

2. secrete neurotransmitters

3. movement occurs in two ways

•anterograde (toward axon

terminal)

•retrograde (away from axonal

terminal- a way that some

pathogens are able to invade the

nervous system)

1. Axon diameter (the larger the diameter the faster the impulse)

2. Presence of a myelin sheath

1. Na+ permeability increases, membrane potential reverses

2. Na1 gates are opened, K1 gates are closed

Occurs as potassium gates open which returns the resting membrane potential.

Occurs as K gates remain open. Shuts brain down, suppresses the limbic system. GABA is released.

1. Follow the all or none law.

2. Are nondecremental

3. Are irreversible

Myelinated fibers. Much faster than unmyelinated fibers .

Chemicals used for neuronal communication. 60 different ones have been identified.

Conducts impulses toward the synapse

Transmits impulses away from the synapse

1. Axodendritic- synapses between the axon of one neuron and the dendrites of another. (Common)

2. Axosomatic- synapses between the axon of one neuron and the soma if another (common)

3. Axoaxonic - axon to axon (uncommon)

Dura mater, arachnoid mater, pia mater

1. Acetylcholine - Best understood. Released at neuromuscular junction by all neurons that stimulate skeletal muscles and some neurons in the autonomic nervous system.

2. Amino acids - found only in the CNS. GABA is important - quiets everything down.

3. Biogenic amines (imbalances can cause mental illness)

•catecholamines (dopamine,

norepinephrine, and epinephrine

•indolamines (serotonin and

histamine)

4. Neuropeptides - act as natural opiates

1. Excitatory neurotransmitters cause depolarization

2. Inhibitory neurotransmitters cause hyperpolarizations (e.g. GABA)

3. Some neurotransmitters have both excitatory and inhibitory effects (determined by the receptor type of the postsynaptic neuron) (e.g. acetylcholine)

1. EPSP - excitatory postsynaptic potentials

2. IPSP - inhibitory postsynaptic potentials

Use G proteins coupled to receptors and are slower.

When a neuron cannot respond to another stimulus

Lined by ependymal cells. Includes paired C-shaped lateral ventricles, the third ventricle found in the diencephalons, cerebral aquaduct connecting third and fourth ventricle, fourth ventricle found in hindbrain dorsal to the pons.

Lateral ventricles --> interventricular foramina --> third ventricle --> cerebral aquaduct --> fourth ventricle --> central canal & pores of the 4th ventricle --> subarachnoid space on the brain & spinal cord surface --> CSF is reabsorbed by arachnoid villi --> CSF mixes with the blood in the superior saggital sinus.

The "executive suite" of the nervous system, where out conscience mind is found. All neurons are interneurons.

The choroid plexuses

Archnoid villi

1. Watery solution similar in composition to blood plasma

2. Forms a liquid cushion that gives buoyancy to CNS organs.

3. Prevents the brain from crushing under it's own weight

4. Protects the CNS from blows and other traumas

5. Nourishes the brain and carries chemical signals throughout it

6. Should be clear, cloudy usually means infection, blood means hemorrhage.

In CNS they are called tracts. In PNS they are called nerves.

1. Three types of functional areas

•motor areas - control voluntary

movement

•sensory areas - conscious

awareness of sensation

•Association areas - integrate

diverse areas

2. Each hemisphere concerned with contralateral side of the body

3. Lateralization of cortical function in hemispheres

4. Conscious behavior involves entire cortex in some way

1. Primary (somatic) motor cortex - all the muscles

2. Premotor cortex - fine motor skills

3. Broca's area - moving muscles to produce sound (speech)

4. Frontal eye field - help you move the eyes

Speech area - ability to speek

Responsible for recognition of spoken and written language

The part of the mind that allows communication between the two hemispheres of the brain. It is responsible for transmitting neural messages between both the right and left hemispheres.

Grey matter embedded in the white matter. Involved in motor control. Control of highly practiced behaviors such as writing, typing, driving, etc. Lesions here can result in dyskinesias. Characteristic of Parkinson's and Huntington's.

Direct pathways that control skilled voluntary movements. Axons descend without synapsing from the pyramidal cells to the spinal cord.

- decussation center (links between higher and lower brain and spinal column)

- relay sensory info - pyramids

- regulate autonomic function (rate and force of heartbeat, blood pressure, rate and depth of breaths)

10% of brain by volume, but has over 50% of total neurons. Cerebellar peduncles link to cerebrum through medulla, pons, and midbrain. Important in motor coordination.

Thalamus, hypothalamus, and epithalamus.

Thalamus is the relay station for info coming into the cerebral cortex. Hypothalamus is the main visceral control center of the body and is important to body homeostasis. Epithalamus is where the pineal gland is located (which makes Melatonin).

Consists of midbrain, pons, and medulla oblongata.

Pons = chiefly composed of conduction tracts

Medulla oblongata = decussation of the pyramid

Send continuous stream of impulses to the cerebral cortex, and also filters the flood of sensory input. Between the RAS and the cerebral cortex, 99% of sensory stimuli are disregarded as unimportant.

Composed of cingulate gyrus, hippocampus, and amygdala. The cingulate gyrus helps you act out emotions with gestures. The hippocampus is for long term memory storage. The amygdala is tied to fear and rage.

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Olfactory, optic, occulomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal.

Sensory, Motor or Both

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A progressive degenerative disease of the brain that results in dementia. Unlike straight dementia, Alzheimer's wull make people forget concepts, not just memories.

Degeneration of the dopamine releasing neurons of the substantia nigra. Cause unknown.

A fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei.

1. Alpha waves - regular and rhythmic, low amplitude, slow, synchronous waves indicating an idling brain. Absent during deep sleep.

2. Beta waves - rhythmic, more irregular waves iccieing during the awake and mentally alert state.

3. Theta waves - more irregular than alpha waves, common in children but abnormal in adults. Can I dictate stress or brain disorders.

4. Delta waves - high amplitude waves seen in deep sleep and when reticular activating system is damped. Predominance of these waves can indicate serious brain damage.

Pain receptors

Types:

1. Fast pain - myelinated pain receptors. Sharp, localized pain receptors.

2. Slow pain - unmyelinated pain receptors. Longer lasting dull, diffuse feeling.

Phasic= adaptable (touch, smell, taste. Will phase out so you can stop experiencing stimulus.)

Tonic= adapt more slowly (proprioceptors. E.g. pain receptors)

The master controlling and communicating system of the body

Composed of pyramidal cells whose axons make up corticospinal tracts. Allows conscious control of precise skilled movements.

Controls learned, repetitious, or patterned motor skills.

Personality

1. Projection fibers: extend vertically between higher and lower brain and spinal cord centers. Carry info between cerebrum and body.

2. Commissural tracts: cross from one cerebral hemisphere to the other

3. Association tracts: connect different regions within the same hemisphere. Allow multiple responses to sensory input.

Connect cerebellum to cerebrum

•1.8 cm thick, 45 cm long

•31 pairs spinal nerves attach by paired roots

•cervical and lumbar enlargements (sites where nerves serving upper and lower limbs emerge)

•conus medullaris - terminal portion of spinal cord

•cauda equina - collection of nerve roots at the inferior end of the vertebral canal

1. Conduction - provides two way communication to and from the brain.

2. Locomotion

3. Reflexes - involuntary stereotyped responses to stimuli. Involves brain, spinal cord, and peripheral nerves.

Bone, meninges, cerebrospinal fluid, and the epidural space (fat filled)

1. Gracile fasciculus - (dorsal column and decussates in medulla) sensations of limb and trunk below level T6

2. Cuneate fasciculus - (dorsal column and decussates in medulla) same as gracile fasiculus except operates from level T6 and up

3. Spinothalamic tract (lateral & ventral column - some fibers decussate in the spinal cord) sensations of pain, temp, pressure, tickle, itch, and touch sensations.

4. Spinoreticular tract (lateral & ventral column - some fibers decussate in the spinal cord) sensations of pain from tissue injury

5. Spinocerebellar tracts - deal with proprioceptive signals from the limbs and trunk to the cerebellum

1. Corticospinal tracts - fine control of limbs

2. Superior colliculi and tectospinal tracts mediate head movements

3. Reticulospinal tracts maintain balance

4. Vestibulospinal (lateral) balance, posture & (ventral) control of head position

Paraplegia= transection between T1 and L1

Quadriplegia= transection in the cervical region.

Area of skin innervated by the cutaneous branches of a single spinal nerve

8 cervical (C1-C8)

12 thoracic (T1-T12)

5 Lumbar (L1-L5)

5 Sacral (S1-S5)

1 coccygeal

-Formed by ventral rami of C1-C4

-most branches are cutaneous nerves of the neck, ear, back of head, and shoulders

-most important is phrenic nerve (Major motor and sensory nerve of the diaphragm)

-formed by C5-C8 and T1

-gives rise to the nerves that innervate the upper limb

-five major nerves

•axillary

•musculocutaneous

•median

•ulnar

•radial

•Arises from L1-L4 and innervates the thigh, abdominal wall, and psoas muscle

•Major nerves are femoral and obturator

•Arises from L4-S4 and serves the buttock, lower limb, pelvic structures, and the perineum

•Major nerve is the sciatic. Sciatic nerve is the longest and thickest in body and is composed of the tibial and common fibular (peroneal) nervesm

1. Receptor (site of stimulus)

2. Sensory neuron (transmits the affected impulse to the CNS)

3. Integration center - either monosynaptic or polysynaptic region within the CNS

4. Motor neuron - conducts efferent impulses from the integration center to an effector (muscle or gland)

5. Effector - muscle fiber or gland that responds to the efferent impulses

1. By stimulus modality (chemoreceptors, thermoreceptors, nociceptors, mechanoreceptors, photreceptors)

2. By the origins of stimuli (interoceptors, proprioceptors, exteroceptors)

3. By the distribution of receptors in the body (General or somesthetic senses or special senses)

Phasic receptors for light touch and pressure (upper part of dermis)

Phasic receptors for deep pressure (lamellar - lower part of dermis)

Only in the soma and only if the myelin sheath is intact. Damaged nerve fibers in the CNS cannot be regenerated.

Endoneurium, perineurium, and epineurium.

Collection of nerve cell bodies

Inborn (intrinsic)

Learned (acquired)

Involve only peripheral nerves and spinal cord

1. Modality

2. Location

3. Intensity

4. Duration

Stretch reflex

Motor output

1. Flaccid paralysis - severe damage to ventral root or anterior horn. No voluntary or involuntary control of muscles. Leads to atrophy.

2. Spastic paralysis - only upper motor neurons of the primary motor cortex are damaged. Muscles stimulated irregularly by reflex, no voluntary control. Movement but no control.

-Gray matter consists of soma, unmyelinatrd processes, and neuroglia.

-white matter: myelinated bundles of axons called tracts

•Dorsal (posterior) horns - interneurons

•ventral (anterior) horns - interneurons and somatic motor neurons

•Gray commissure - connects masses of gray matter and encloses central canal.

•Dorsal half - sensory roots and ganglia

•Ventral half - motor roots

•dorsal and ventral roots fuse laterally to form spinal nerves

•lateral horns - contain sympathetic nerve fibers

•four zones are evident within gray matter - somatic sensory (SS) visceral sensory (VS), visceral Motor (VM), and somatic motor (SM)

- somatic sensory (SS) visceral sensory (VS), visceral Motor (VM), and somatic motor (SM)

1. Fibers run in 3 directions, ascending, descending, transversely

2. Divided into 3 funiculi (columns) - posterior, lateral and anterior

3. Each funiculus contains several fiber tracts

Includes cerebrum, cortex, white matter, amd basal nuclei. Lateral ventricles.

Thalamus, hypothalamus, and epithalamus. Third ventricle.

Brain stem, mid brain. Cerebral aquaduct.

Brain stem, pons. Fourth ventricle.

Brain stem, medulla oblongata. Central canal.