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102 terms

A&P 1 Test 4

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astrocytes
-most abundant, versatile, and highly branched glial cell
-cling to neurons, synaptic endings, and capillaries
-support and brace neurons
-help determine capillary permeability
-guide migration of young neurons
-control the chemical environment
-participate in information processing in the brain
-most abundant CNS neuroglia
ependymal cells
-range in shape from squamous to columnar
-may be ciliated
-line the central cavities of the brain and spinal column
-seperate the CNS interstitual fluid from the cerebrospinal fluid in the cavities
-secrete CSF
-line the cerebrospinal fluid-filled cavities
neurilemma
peripheral bulge of schwann cell cytoplasm
neuron
special characteristic:
-long lived ( 100 +)
-amitotic: with few exceptions
-high metabolic rate: depends on continuous supply of oxygen and glucose
-plasma menbrane functions in:
-electrical signaling
-cell to cell interactions during development
ANS function
-visceral motor nerve fibers
-regulates smooth muscle, cardiac muscle, and glands
-two functional subdivisions:
1. sympathetic
2. parasympathetic
sympathetic
mobilize body system during activities
parasympathetic
-conserves energy
-promotes housekeeping functions during rest
chemical classes of neurotransmitters
-acetylcholine (Ach)
-biogenic amines include
-amino acids include
-peptides (neuropeptides)
-purines such as ATP
-gases and lipids
chemical classes of neurotransmitters: achtylcholine
-released at neuromuscular junctions and some ANS neurons
-synthesized by enzyme choline acetyltransferase
-degraded by the enzyme acetylcholinesterase
chemical classes of neurotransmitters: biogenic amines include
-catecholamines
-dopamine, norepinephrine (NE), and epinephrine
-indolasmines
-serotonin and histamine

-broadly distributed in the brain
-play roles in emotional behaviors and the biological clock
chemical classes of neurotransmitters: amino acids include
-GABA: Gamma- aminobutyric acid
-glycine
-aspartate
-glutamate
chemical classes of neurotransmitters: peptides (neuropeptides) include
-substance P
-mediator of pain signal
-endorphins
-act as natural opiates; reduce pain perception
-gut-brain peptides
-somatostatin and cholecystokinin
chemical classes of nerotransmitters: purines such as ATP
-act in both the CNS and PNS
-produce fast or slow responses
-induce Ca^2+ influx in astrocytes
-provoke pain sensation
chemical classes of nerotransmitters: gases and lipids
-nitric oxide (NO)
-synthesized on demand
-activates the intracellular receptor guanylyl cyclase to cyclic GMP
-involved in learning and memory

-carbon monoxide (CO) is regulator of cGMP in the brain

-endocannabinoids
-lipid soluable; synthesized on demand from menbrane lipids
-bind with G protein-coupled receptors in the brain
-involved in learning and memory
Action potential (nerve impulse)
-briefly reversal of membrane potential with a total amplitude of ~100mV
-occurs in muscle cells and axon of neurons
-does not decrease in magnitude over distance
-principal means of long distance neural communication

-resting rate:
-only leakage channels for Na+ and K+ are open
-all gated Na+ and K+ channels are closed
synapse
-a junction that mediates information transfers from one neuron
-to another neuron, or
-to an effector cell
synapse
-presynaptic neron
-postsynaptic neron
presynaptic neuron
conducts impulses toward the synapse
postsynaptic neuron
transmits impulses away from the synapse
types of synapes
-axodentritic
-axosomatic
-less common types: axoaxonic (axon to axon)
dedrodentritic (dendrite to dendrite)
dendrosomatic (dendrite to soma)
axodentritic
between the axon of one neuron and the dendrite of another
axosomatic
between the axon of one neuron and the soma of another
electrical synapses
-less common than chemical synapses
-neurons are electrically coupled (joined by gap junctions)
-communication is very rapid, and may be unidrectional or bidirectional
-are important in: embryotic nervous tissue
some brain regions
chemical synapses
-specialized for the release and reception of neurotransmitters
-typically composed of two parts:
-axon terminal of the presynaptic neuron, which contains synaptic versicles
-receptors region on the postsynaptic neuron
schwann cells (neurolemmocytes)
-surrounds peripheral nerve fibers and form myelin sheaths
-vital to regeneration of damaged peripheral nerve fibers
oligodendrocytes
-branched cells
-processes wrap CNS nerve fibers, forming insulating myelin sheaths
Action potential: depolarizing phase
-depolarizing local currents open voltage-gated Na+ channels
-Na+ influx causes more depolarization
-at threshold (-55 tp -50 mV) positive feedback leads to opening of all Na+ channels, and a reversal of membrane polarity to +30mV (spike of action potential)
Action potential: repolarizing phase
-Na+ channel slow inactivation gates close
-membrane permeability to Na+ declines to resting levels
-slow voltage-sensitive K+ gates open
-K+ exits the cell and internal nagativity is restored
sensory input
information gathered by sensory receptors about internal and external changes
motor output
activation of effector organs (muscles and glands) produces a response
peripheral nervous system (PNS): sensory (afferent) division
-somatic afferent fibers: convey impulses from skin,skeletal muscles, and joint
-visceral afferent fibers:convey impulses from visceral organs
peripheral nervous system (PNS): motor (efferent) division
-transmits impulses from the CNS to effector organs
sensory (afferent) nerves
those that carry impulses only toward the CNS
sensory (efferent) nerves
those carry impulses only away from the CNS
cranial nerves
-12 pair of nerves
-arise from brain
-exit through foramina leading to muscles, glands and sense organs in head and neck

-input and output ipsilateral except CN II and IV
olfactory nerve
I. (1)
-sense of smell
-damage causes impaired sense of smell
optic nerve
II. (2)
-provide vision
-damage causes blindness in visual field
oculomotor nerve
III. (3)
-eye movement, opening of eyelid, constriction of pupil, focusing
-damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in certain directions
trochlear nerve
IV. (4)
-eye movement (superior oblique muscle)
-damage causes double vision and inability to rotate eye inferolaterally
trigeminal nerve
V. (5)
-sensory to face (touch, pain, and temperature) and muscles of mastication
-damage produces loss of sensation and impaired chewing
abducens nerve
VI. (6)
-provides eye movement (lateral rectus m)
-damage results in inability to rotate eye laterally and at rest eye rotates medially
facial nerve
VII. (7)
-motor: facial expressions; salivary glands and tears, nasal and palatine glands
-sensory: taste on anterior 2/3 of tongue
-damage produces sagging facial muscles and distributed sense of taste (no sweet or salty)
vestibulocochlear nerve
VIII. (8)
-provides hearing and sense of balance
-damage produces deafness, dizziness, nausea, loss of balance and nystagmus
glossopharyngeal nerve
IX. (9)
-swallowing, salivation, gagging, control of BP and respiration
-sensations from posterior 1/3 of tongue
-damage results in loss of bitter and sour taste and impaired swallowing
vague nerve
X. (10)
-swallowing, speech, regulation of viscera
-damage causes hoarseness or loss of voice, impaired swallowing and fatal if both are cut
accessory nerve
XI. (11)
-swallowing, head, neck, and shoulder movement
-damage causes impaired head, neck, shoulder movement; head turns towards injured side
hypoglossal nerve
XII. (12)
-tongue movements for speech, food manipulation and swallowing
-if both are damaged-can't protrude tongue
-if one side is damaged- tongue deviates towards injured side; see ipsilateral atrophy
arbor vitae
the distinctive pattern of white matter in the cerebellum resembles a branching tree, pattern fancifully
brain stem
-three regions: midbrain, pons, medulla oblongata
-similar structure to spinal cord but contains embedded nuclei
-control automatic behaviors necessary for survival
-contains fiber tracts connecting higher and lower neural centers
-associated with 10 of the 12 pairs of cranial nerves
Primary auditory cortex
-located in the superior margin of the temporal lobe abutting the lateral sulcus
primary auditory cortex
-sound energy exciting the hearing receptors of the inner ear causes impulses to be transmitted to the primary auditory cortex, where they are interrupted as pitch, loudness and locomotion
meninges
-dura mater: outermost, tough membrane
-arachnoid and pia mater: as in spinal cord
dura mater
-outer periosteal layer against bone
-where seperated from innter meningeal later forms dural venous sinuses draining blood from brain
-supportive structures formed by dura mater
-falx cerebri, falx cerebelli and tentorium cerebelli
-epideral space filled with fat in low back
-epidural anaesthesia during childbirth
arachnoid and pia mater
subarachnoid and subdural spaces
medulla oblongata
-3 cm extension of spinal cord
-ascending and desending nerve tracts
-nuclei of sensory and motor CNS (IX, X, XI, XII)
-pyramids and olive visible on surface
hypothalamus
walls and floor of 3rd ventricle
hypothalamus
functions:
-hormone secretion
-autonomic NS control
-thermoregulation
-food and water intake (hunger and satiety)
-sleep and circadian rhythms
-memory (mammillary bodies): contain 3-4 nuclei that relay signal from limbic system to thalamus
-emotional behavior
wernicke area
permits recognition of spoken and written language and creates plan of speech
-can speak but cant understand language
broca area
-generates motor signals for larnx, tongue, cheeks and lips
-transmits to primary motor cortex for action
-can understand language but difficult speaking
blood brain barrier
-is endothelium
-permeable to lipid-soluble materials
-alcohol, O2, nicotine and anesthetics
-circumventricular organs
-in 3rd and 4th ventricles are breaks in the barrier where blood has direct access
- motors glucose,pH,osmolarity, and others
-route for HIV virus to invade the brain

-at choriod plexus is ependymal cells joined by tight junctions
memory
-information management
-requires learning, memory and forgetting
memory: amnesia
-anterograde amnesia- NO new memory
-retrograde amnesia-can't remember old ones
memory: hippocampus
organizes sensory and cognitive information into a new memory
memory: cerebellum
helps learn motor skills
memory: amygdala
emotional memory
Non-REM sleep: Stage 1
drifting sensation (claim not sleeping)
Non-REM sleep: Stage 2
light sleep
Non-REM sleep: Stage 3
vital sign change-BP, pulse and breathing rates drop
-reached in 20 mins
Non-REM sleep: Stage 4
deep sleep
-difficult to arouse
REM sleep
repid eye movement under eyelids, vital signs increases, EEG resembles awake person, dreams and penile erections occur
beta
eyes open, performing mental tasks
alpha
occur when awake, resting with eyes closed
theta
sleep or emotional stree
delta
deep sleep
meningitis
-inflammation of the meninges
-disease of infancy and childhood
-b/w 3 months to 2 years old
-bacterial and virus invasion of the CNS by way of the nose and throat
-signs include high fever, stiff neck, drowsiness and intense headache and may progress to coma
-diagnose by examining the CSF
-lumbar puncture (spinal tap)
dorsal ramus
supplies dorsal body muscle and skin
ventral ramus
to ventral skin and muscles and limbs
phrenic nerve
-receives fibers from C3-C5
-run inferiorly through the thorax and supply both motor and sensory fibers to the diaphragm, which is the chief muscle causing breathing movement
Encephalo means
brain
Which of the following areas of the brain controls voluntary movement of the eyes
frontal eye field
Which of the following areas of the brain is responsible for spatial discrimination?
Primary somatosensory cortex
Which of the following is not a function of the hypothalamus?
Secretion of the hormone melatonin
Patients who have lesions involving Broca's area
can understand language, but have difficulty speaking.
Which part of the brain is the "executive suite" for all brain activity?
cerebral cortex
Which part of the brain is the gateway to the cerebral cortex?
thalamus
Which of the following best describes the hypothalamus?
visceral control center of the body
Which part of the brain stem houses the reflex centers for respiration and cardiovascular functioning?
medulla oblongata
Which part of the brain is the motor command center?
cerebellum
Sensory neurons enter the spinal cord via the ________ horn.
dorsal
There are ____ pairs of cranial nerves
12
The phrenic nerve serves the
diaphragm
Which of the following cranial nerves carries only sensory information?
olfactory
Which cranial nerve transmits information about our sense of equilibrium?
vestibulocochlear
The abducens nerve ________.
supplies innervation to the lateral rectus muscle of the eye
The trochlear nerve conveys proprioceptor impulses from the ________ to the brain.
superior oblique muscle
Problems in balance may follow trauma to which nerve?
vestibulocochlear
The ________ nerve is the largest of the cranial nerves.
trigeminal
Which of the following is not one of the chemical classes into which neurotransmitters fall?
Chlorides
What type of stimulus is required for an action potential to be generated?
a threshold level stimulus
Which of the following types of glial cells produce the myelin sheaths that insulate the neural fibers in the CNS?
Oligodendrocytes
Which of the following types of neurons carries impulses away from the CNS?
motor
Which of the following PNS neuroglia help to form myelin sheaths around larger nerve fibers in the PNS?
Schwann cells