Human Physiology Exam 2 (new)

Five brain regions formed during embryonic development

• telencephalon

• diencephalon

• mesencephalon

• metencephalon

• myelencephalon

forebrain

constituted of the telencephalon and diencephalon

midbrain

mesencephalon

hindbrain

composed of the metencephalon and myelencephalon

how does the CNS begin

as a hollow tube

ventricles

the cavities of the brain

cerebrum

consists of two hemispheres connect by a large fiber tract called the corpus callosum

cerebral cortex

the outer part of the cerebrum, consists of gray matter

basal nuclei (basal ganglia)

nuclei of gray matter that lie deep within the white matter of the cerebrum

electroencephalogram (EEG)

synaptic potentials within the cerebral cortex produce the electrical activity

cerebral lateralization

specialization of function of the two cerebral hemispheres

left hemisphere

dominant in language and analytical ability

right hemisphere

important for pattern recognition, musical composition, singing, and the recognition of faces

aphasias

difficulty of speech

werenicke’s area

involved in speech comprehension, whereas the motor speech area is required for the mechanical performance of speech

believed to control the motor speech area by means of the arcuate fasciculus

angular gyrus

believed to integrade different sources of sensory information and project to Wernicke’s area

emotional centers of the brain

limbic system and hypothalamus

categories of memory

long term

short term

medial temporal lobes (specifically hippocampus and amygdaloid body)

required for the consolidation of short-term memory into long-term memory

long term potentiation (LTP)

a phenomenon that may be involved in some aspects of memory

diencephalon

the region of the forebrain that includes the thalamus, epithalamus, hypothalamus, and pituitary gland

thalamus

serves as an important relay center for sensory information, among its other functions

epithalamus

contains a chloroid plexus, where cerebrospinal fluid is formed

the pineal gland, which secretes the hormone melatonin is also part

hypothalamus

forms the floor of the third ventricle, the main control center for visceral organs

contains centers for the control of thirst, hunger, body temperature, and various emotions

regulates the secretions of the pituitary gland, controls the posterior pituitary by means of a fiber tract, and it controls the anterior pituitary by means of hormones

midbrain

contains the superior and inferior colliculi, which are involved in visual and auditory reflexes, respectively, and nuclei that contain dopaminergic neurons that project to the corpus striatum and limbic system of the forebrain

metencephalon

contains the pons and cerebellum

pons

contains nuclei for four pairs of cranial nerves

cerebellum

plays an important role in the control of skeletal movements

medulla oblongata

contains centers for the regualtion of such vital functions as breathing and the control of the cardiovascular system

reticular activating system (RAS)

an ascending arousal system consisting of interconnected neurons of the reticular formation that extend from the pons to the midbrain

how is arousal promoted

by different neural tracts of the RAS that release ACh, different monoamine neurotransmitters, and a polypeptide neurotransmitter known as orexin (or hypcretin-1)

how is arousal inhibited

by GABA-releasing neurons, and this activity is necessary for sleep

ascending tracts

carry sensory information from sensory organs up the spinal cord to the brain

descending tracts (motor tracts) groups

pyramidal and the extrapyramidal systems

pyramidal tracts

the corticospinal tracts

they begin in the precentral gyrus and descend, without synapsing, into the spinal cord

where do corticospinal fibers decussate

the pyramids of the medulla oblongota

how do regions of the cerebral cortex, basal ganglia, and the cerebellum control movements

by indirectly synapsing with other regions that rive rise to descending extrapyramidal fiber tracts

reticulospinal tract

the major extrapyraidal motor tract, has its origin in the reticular formation of the midbrain

spinal nerves

there are 31 pairs and each pair contains both sensory and motor fibers

dorsal root

contains sensory fibers and the cell bodies of these neurons are contained in the dorsal root ganglion

ventral root

a spinal nerve that contains motor fibers

reflex arc

a neural pathway involving a sensory neuron and a motor neurons. One or more association neurons may also be involved in some reflexes

preganglionic autonomic neurons

originate in the brain or spinal cord

postganglionic neurons

originate in ganglia located outside the CNS

Which structures receive autonomic innervation

smooth muscle, cardiac muscle, and glands

involuntary effectors

somewhat independent of their innervation and become hypersensitive when their innervation is removed

effects of autonomic nerves

either excitatory or inhibitory effects on their target organs

where do preganglionic neurons of the sympathetic division originate

in the spinal cord, between the thoracic and lumbar levels

collateral ganglia

where some preganglionic fibers synapse, these are the celiac, superior mesenteric, and inferior mesenteric ganglia

adrenal medulla

where some preganglionic fibers innervate, secretes epinephrine (and some norepinephrine) into the blood in response to stimulation

preganglionic parasympathetic fibers

originate in the brain and in the sacral levels of the spinal cord

contribut to cranial nerves 3, 7, 9, and 10

where do the long preganglionic fibers of the vagus nerve synapse?

in terminal ganglia located next to or within the innervated organ, short postganglionic fibers then innervate the effector cells

vagus nerve

provides parasympathetic innervation to the heart, lungs, esophagus, stomach, liver, small intestine, and upper half of the large intestine

parasympathetic outflow from sacral levels of the spinal cord

innervates terminal ganglia in the lower half of the large intestine, in the rectum, and in the urinary and reproductive systems

sympathetic division

activates the body to “fight or flight”

parasympathetic division

exerts antagonistic actions through cholinergic effects

all preganglionic autonomic nerve fibers are ______________

cholinergic (use ACh as a neurotransmitter)

Most preganglionic sympathetic fibers are _____________

cholinergic (use ACh as a neurotransmitter)

sympathetic fibers that innervate sweat glands and those that innervate blood vessels in skeletal muscles are ____________

cholinergic

Adrenergic effects

stimulation of the heart, vasoconstriction in the viscera and skin, broncdilation, and glycogenolysis in the liver

classes of adrenergic receptors

alpha and beta

which adrenerigic receptors does the heart have?

both alpha and beta receptors

cholinergic effects of parasympathetic nerves

are promoted by the drug muscarine and inhibited by atropine

what are the effects of sympathetic and parasympahtetic divisions in organs with dual innervation

antagonistic, complementary, or cooperative

where are antagonistic effects

heart and pupils of the eyes

where are complementary effects

regulation of salivary gland secretion and are cooperative in the regulation of the reproductive and urinary systems

how do organs without dual innervation regulate

regulation is achieved by variation in sympathetic nerve activity

medulla oblongata

the area that most directly controls the activity of the autonomic system, influenced by sensory input and by input from the hypothalamus

hypothalamus influences

influenced by input from the limbic system, cerebrellum, and cerebrum

these interconnections provide an autonomic component to some of the visceral responses that accompany emotions

how are sensory receptors categorized

the basis of their structure, the stimulus energy the transduce, or the nature of their response

tonic receptors

continue to fire as long as the stimulus is maintained; they monitor the presence and intensity of a stimulus

phasic receptors

respond to stimulus changes; they do not respond to a sustained stimulus, and this partly accounts for sensory adaptation

law of specific nerve energies

says that each sensory receptor responds with the lowest threshold to only one modality of sensation (that stimulus modality is called the adequate stimulus)

adequate stimulus modality of the receptor

stimulation of the sensory nerve from a receptor by any means

generator potentials

graded changes (usually depolarizations) in the membrane potential of the dendritic endings of sensory neurons

magnitiude of potential change and strength of stimulus

the magnitude of the potential change of the generator potential is directly proportional to the strength of the stimulus applied to the receptor

what happens after the generator potential reaches a threshold value

increases in the magnitude of the depolarization result in increased frequency of action potential production in the sensory neuron

somatesthetic information pathway

comes from cutaneous receptors and proprioceptors, its carried by third-order neurons to the postcentral gyrus of the cerebrum

proprioception and pressure sensation pathway

ascend on the ipsilateral sidde of the spinal cord, synapse in the medulla and cross to the contralateral side, and then ascend in the medial lemiscus to the thalamus; neurons in the thalamus, in turn, project to the postcentral gyrus

sensory neurons from cutaneous receptors pathway

synapse and cross to the contralateral side in the spinal cord and ascend in the lateral and ventral spinothalamic tracts to the thalamus; neurons in the thalamus then project to the postcentral gyrus

receptive field of a cutaneous sensory neuron

the area of the skin that, when stimulated, produces responses in the neuron

greater density of cutaneous receptors

receptive fields are smaller

two-point touch threshold

reveals that the fingertips and tip of the tongue have a greater density of touch receptors, and thus a greater sensory acuity, that other areas in the body

lateral inhibition

acts to sharpen a sensation by inhibiting the activity of sensory neurons coming from areas of the skin around the area that is most greatly stimulated

modalities of taste

salty, sour, weet, bitter, umami (stimulated by glutamate, more recently recognized)

salty and sour taste mechanism

produced by the movement of sodium and hydrogen ions, respectively, through membrane channels

sweet and bitter taste mechanism

produced by binding of molecules to protein receptors that are coupled to G-proteins

olfactory receptors

neurons that synapse within the olfactory bulb of the brain

odorant molecules

bind to membrane protein receptors (there may be as many as 1,000 different receptor proteins responsible for the ability to detect as many as 100,000 different odors)

odorant molecule mechanism

binding to its receptor causes the dissociation of large numbers of G-protein subunits. the effect is therefore amplified, which may contribute t the extreme sensitivity of the sense of smell

vestibular apparatus

the structure involved in equilibrium, consists of the otolith organs (utricle and saccule) and the semicircular canals

utricle and saccule

provide information about linear acceleration

semicircular canals

provide information about angular acceleration

hair cells

the sensory receptors for equilibrium that support numerous sterocilia and one kinocilium

when is the plasma membrane depolarized for hearing

when the stereocilia are bent in the direction of the kinocilium

when is the plasma membrane hyperpolarized

when the sterocilia are bent in the opposite direction of the kinocilium

projection of the sterocilia of the hair cells in the utricle and saccule

project into the endolymph of the membranous labrynth and are embedded in a gelatinous otolith membrane

upright position : steriocillia

when a person is upright, the sterocilia of the utricle are oriented vertically; those of the saccule are oriented horizontally

linear acceleration

produces a shearing force between the hairs of the otolith membrane, thus bending the stereocilia and electrically stimulation the sensory endings

cupula

a gelatinous membrane where hair cells of the semicircular canals are embedded, projects into the endolymph