Lecture Exam 4

what’re the 3 major portions of the brain?

forebrain (cerebrum), cerebellum, & brainstem

what separates the cerebellum from the cerebrum?

the transverse cerebral fissure

what percent of the brain’s neurons are located in the cerebellum?

50%

what’re the components of the brainstem?

diencephalon, midbrain, pons, medulla oblongata

where is the white and gray matter in the brain?

gray matter goes around white matter (opposite of spinal cord)

what’re the components of white matter in the brain?

• deep in the brain

• composed of tracts/ bundles of axons which connect one part of the brain to another and to the spinal cord

what’re the components of gray matter in the brain?

• cortex OVER cerebrum/cerebellum

• set of neurosomas, dendrites, and synapses

how many pairs of spinal nerves are there?

31

what do the ascending tracts of the spinal cord carry?

sensory info to the brain

what do the descending tracts of the spinal cord carry?

motor impulses DOWN

what’re the meninges of the nervous system?

lie btwn nervous tissue and bone; protect the brain and provide structural framework for arteries and veins

what does the brain barrier system (BBS) do & what is is comprised of?

• it is the “gate” that anything leaving the blood must past through protecting the brain

• consists of tight jxns btwn endothelial cells that form capillary walls which stimulate the endothelial cells to form tight junctions

what percentage of the body’s blood goes to the brain?

15%

why is the blood blain barrier so important?

because damages brain tissue is irreplaceable

what’re spinal taps?

procedures that’re also known as lumbar punctures

how is a spinal tap done?

pt leans forward, separating vertebral laminae, skin anesthetized, needle inserted btwn spinous process of L3 + L4 (sometimes L4+5)--(safest to obtain CSF bc spinal cord doesn’t extend this far; injury not a concern); @ a depth of 4-6 cm, puncturing the dura mater ENTERING the lumbar cistern

what meninge is punctured during a spinal tap?

the dura mater, entering the lumbar cistern

what are spinal taps done?

to obtain CSF from lumbar cisterns

what’re lumbar punctures/spinal taps used for?

to diagnose neurological disease by examining the CSF for bacteria, blood, WBC, or abnorm. of chem comp.

what *is* the brainstem?

a vertical stalk that supports the large cerebellum and rear of head as well as the cerebral hemi.

what’re the different structured of the brainstem?

medulla oblongata, pons, midbrain

where are “pyramids” located?

in the brainstem ; medulla oblongata; baseball-looking

what’s the largest group of descending fibers that goes through the medulla oblongata?

corticospinal - carry motor signals from cerebral cortex → spinal cortex ULTIMATELY stimulating skeletal muscles

what’s a major role/characteristics of the medulla oblongata?

any time you move below the neck, the signals → muscles and come through here (90% decussate) ; adult myencephalon - part of brainstem

what’s a major role/characteristics of the pons?

• part of brainstem, developed from metencephalon

• formed by 2 thick stalks: cerebellar penduncles connecting the cerebellum to the midbrain

• sensory roles in hearing equilibrium and tatse, face sensations, touch/pain, motor roles in eye movmnt, face expressions, chewing, swallowing, urination, a secretion of saliva…

• nuclei controls sleep, respiration, and posture

what’s a major role/characteristics of the midbrain?

• part of brainstem

• control of extrinsic muscles, enable directed gaze, track movement, turn head & eyes in response to stimuli, other eye controls, relaying sound signals, relays signals

what structures lie within the midbrain?

• cerebral aqueduct, involved w reticular formation in cntrling pain awareness

• motor nuclei of 2 cranial nerves, cntl eye mvmnts (cranial nerves III (oculomotor) + IV (trochlear))

• tectum,

• protectal nuclei, cntrl pupillary diameter & focusing lens

• both colliculi, help to LOCATE where sound is coming from, processes pitch & helps us understand speech

• cerebral peduncles, 2 stalks that anchor cerebrum to brainstem (tegmentum, substantia nigra, cerebral crus)

what’re the different structures of the cerebral lobe?

frontal, parietal, occipital, temporal, & insula

what’s the fxn of the frontal lobe?

abstract thought, explicit/declarative memory, cognitive & emotional processes (mood, motivation, foresight, planning, decision making, emo control, & judging social appropriateness), & speech production/voluntary motor control

what’s the fxn of the parietal lobe?

taste, somatic sensation (touch, heat, & pain), visual processing, multisensory integration (correlated sight & sound to holistically comprehend sensory world), spacial perception, body orientation awareness (sense of physical quanitities)

what’re the fxns of the occipital lobe?

principle visual center of the brain; where we 1st become aware of visual stimuli & process this info to identify what we see

what’re the fxns of the temporal lobe?

concerned w/ hearing, smell, emo, learning, language comp, memory of grammar & vocab. of languages we speak, memory consolidation - formation of long-term mems, storage of visual, verbal, and auditory memories

what’re the fxns if the insula?

roles in taste, pain, visceral sensation, consciousness, emo responses & empathy; cardiovascular homeostasis (responses to exercise)

what’re the important functions of the limbic system?

• imp center for emotion and learning

• allows for circular patterns of feedback among its nuclei and cortical neurons

• EMOTION & MEMORY

• has centers for gratification (pleasure/reward) & aversion (fear/sorrow)

what are the different parts of the limbic system?

cingulate gyrus, hippocampus, amygdala

what’s the cingulate gyrus a part of and what’s its fxn?

• limbic system

• arches over top of corpus callosum in frontal & parietal

what’s the hippocampus a part of and what’s its fxn?

• limbic system

• memory forming (not strong), organizes sensory & cognitive experiences into LONG-TERM mems, learns from a sensory input while it’s happening but this is SHORT term, during sleep is replays mems repeatedly “slow-learner”, but forms the long-term

• “the Netflix of the brain”

what’s the amygdala a part of and what’s its fxn?

• limbic system

• dominated by aversion centers; memory; receives processed info from general senses (vision, hearing, taste, & smell) & correlates that smell/sense to WHAT IT IS (good odor, pretty view, etc.)

• output from here is imp in somatic and visceral motor systems (emo response too) as well as conscious control & expression of emotions

what’re brainwaves?

rhythmic voltage channels resulting from synchronized postsynaptic potentials (NOT action potentials) in superficial layers of cerebral cortex

what’re EEGs used for?

* useful for studying normal brain fxns (sleep & consciousness) as well as diagnosing degenerative brain diseases, metabolic abnormalities, brain tumors, trauma, etc.
* consciousness/high alertness → deep sleep are correlated w EEG changes

when are alpha waves present & in what region of the brain?

• when pt is awake, relaxed, eyes open, mind wandering; suppressed when a person opens eyes, receives stimulation/engages in a mental task,

• ABSENT during deep sleep

• parieto-occipital area

when are beta waves present & in what region of the brain?

• accentuated during mental activity & sensory stimulation; concentrating; eyes open and performing mental tasks

• frontal to parietal region

when are theta waves present?

• normal in children/drowsy sleeping adults

• if they’re present in awake adults suggests stress/brain disorders

when are delta waves present?

• high amplitude “slow waves”

• infants exhibit when awake

• adult deep sleep

• present in awake adult = serious brain damage

what’re the names of the different brian waves?

alpha, bets, theta, delta

what’s meningitis?

• inflammation of meninges

• serious disease of infancy

• bacteria invades CNS through orifices

• cerebral swelling & death

what happens with a stroke?

brain tissue death to half of normal blood supply

what’s Parkinson’s disease?

• degeneration of substantia nigra (motor center characterized w melaninated nucleus)

• dopamine related

what’s narcolepsy?

• autoimmune disease characterized by onset REM sleep

• antibody-mediated destruction of orexin-producing neurons

what’s the autonomic nervous system (ANS) also known as?

the visceral motor system

what’re some ANS disorders?

horner syndrome & raynaud disease

what’s Horner syndrome?

• ANS disorder

• chronic unilateral pupil constriction

• eyelid sagging, withdrawal of eye into orbit, skin flushing, & lack of facial perspiration, …

what’s Raynaud disease?

• ANS disorder

• intermittent paleness, cyanosis, & phalange pai caused form cold/emotional triggers

• digital vasoconstriction

what does the autonomic nervous system (ANS) do/what is it?

• it’s a motor nervous system that controls, glands, cardiac muscle and smooth muscle

• responsible for body’s VISCERAL REFLEXES (unconscious and involuntary responses to stimuli, which involve visceral receptors and effectors

what are the visceral reflexes of the ANS?

1. receptors - nerve endings that detect stretch, tissue damage, blood chemistry, body temp., and other internal stimuli

2. afferent neurons - lead to integrating centers in the CNS

3. efferent neurons - carry motor signals AWAY from CNS

4. effectors - carries out end response

are the actions of the ANS typically voluntary or involuntary?

involuntary

what’re the divisions of the ANS?

sympathetic & parasympathetic

what transmitters & receptors are involved in a parasympathetic fiber?

LONG preganglionic neuron + ACh → nicotinic receptor on SHORT postganglionic neuron + ACh → muscarinic receptor on target cell

what transmitters & receptors are involved in a sympathetic adrenergic fiber?

SHORT preganglionic neuron + ACh → nicotinic receptor on LONG postganglionic neuron + NE → adrenergic receptor on target cell

what transmitters & receptors are involved in a sympathetic cholinergic fiber?

SHORT preganglionic neuron + ACh → nicotinic receptor on LONG postganglionic neuron + ACh → muscarinic receptor on target cell

what’re the 2 different categories of sense receptors?

unencapsulated & encapsulated

what type of sense receptors are free nerve endings & what do they sense?

• unencapsulated ; widespread across epithelia and connective tissue

• pain, heat, & cold

what type of sense receptors are tactile discs & what do they sense?

• unencapsulated ; stratum basale of epidermis

• light touch and pressure

what type of sense receptors are hair rceptors & what do they sense?

• unencapsulated

• light touch & mvmnt of hairs

what type of sense receptors are tactile corpuscles & what do they sense?

• encapsulated ; dermal papillae of sensitive areas

• light touch, texture

what type of sense receptors are end bulbs & what do they sense?

• encapsulated ; mucous membs

• similar to tactile corpuscles

what type of sense receptors are bulbous corpuscles & what do they sense?

• encapsulated ; dermis/subcu. tissue & joint caps

• heavy continuous touch/pressure & joint mvmnts

what type of sense receptors are lamellar corpuscles & what do they sense?

* encapsulated
* deep pressure, strecth, tickle, & vibration

what type of sense receptors are muscle spindles & what do they sense?

* encapsulated
* muscle stretch (proprioception)

what type of sense receptors are tendon organs & what do they sense?

• encapsulated

• tension on tendons (proprioception)

what’re the unencapsulated sense receptors?

• free nerve endings

• tactile discs

• hair receptors

what’s the primary sense cortices for vision?

the primary visual cortex in the occipital lobe

where’s the primary sense cortices for spacial perception?

in the inferior temporal lobe, also where we recognize faces and objects

what’s the primary sense cortices for hearing?

the primary auditory cortex in the superior portion of the temporal lobe near the insula

where’s the primary sense cortices for equilibrium?

signals go from the inner ear to the cerebellum (& several other brainstem nuclei) making its way to the central sulcus which is the seat of consciousness of body movements and orientation in space

what’s the primary sense cortices for taste & smell?

taste - received by primary gustatory cortex in the postcentral gyrus

smell - primary olfactory cortex in the medial temporal lobe/inferior frontal lobe

both - orbitofrontal cortex, important for liking/disliking food and drinks

what’re olfactory cells and why is this unique?

• neurons

• they’re the only neurons directly exposed to the external environment AND replaceable

what’re the binding sites for odor molecules called (they lie in a thin layer of mucous)?

olfactory hairs

roughly, what’re the steps of smelling?

odorant molec binds to receptor on one of olfactory hairs → hydrophilic go straight through mucous & bind directly to the receptor whereas hydrophobic have a transporter (odorant-binding protein in mucous)→ G protein becomes activated → cAMP (2nd messenger system) which ultimately opens ion channels in plasma memb admitting cations Na & Ca into the cell DEPOLARIZING it CREATING a RECEPTOR POTENTIAL

what’s the pathway of smelling past the nose?

• in the olfactory bulbs where the olfactory fibers synapse w dendrites of neurons (mitral & tufted cells)

• olfactory cell axons reach UP; mitral and tufted cell dendrites reach DOWN to meet in the glomeruli -- each glomeruli is dedicated to a unique odor

• tufted and mitral cells carry OUTPUT from glomeruli

what’re the olfactory tracts composed of?

tufted and mitral cell axon bundles, which run caudally along the underside of the frontal lobe the

where do most fibers of olfactory tracts end and is also where we first become conscious of odor?

the primary olfactory cortex

how can olfactory cells reach the cerebral cortex directly?

via spinoreticular pain pathways

what does the orbitofrontal cortex do with the signals it receives from the primary olfactory cortex?

it uses signals to identify and discriminate btwn odors and interprets/inspects food for desirability

where are olfactory signals relayed to other than the primary olfactory cortex?

* amygdala, hippo., insula, and hypothalamus
* these work to associate odor w/olfactory mems and emo response

what’re granule cells in olfaction?

neurons that send olfactory cortex info BACK to the olfactory bulbs

what’re the 3 purposes of CSF?

buoyancy- makes brin lighter in skull, protection - stops brain from striking the cranium, & chemical stability - rinses waste from nervous tissue and regulates brain’s chemical environment

what structures are involved in CSF containment?

2 lateral ventricles, 3rd ventricle, & 4th ventricle

what’s the “flow” of CSF in the cranium?

• lateral ventricles→ interventricular foramina → 3rd ventricle → down cerebral aqueduct → 4th ventricle (some lost via 3 pores here) → central canal

• choroid plexuses add more CSF along the way

where is the CSF made/sourced?

• mainly choroid plexus & ependymal cells

• 40% is formed by subarchnoid space (external to brain); 30% in general ependymal lining of brain ventricles; & 30% choroid plexus

what/where are the choroid plexuses?

• produces CSF ; blood capillaries

• on the floor/wall of each ventricle

what do the ependymal cells do to CSF?

they modify the filtrate as it passes through, making sure it has more NaCl, but less K, Ca, glucose, (a little protein) than the blood plasma

what’s the main job of the cerebellum?

• motor coordination, locomotor ability

• non-motor activities: time, planning, and emo control

what’s the 2nd largest region of the brain and what % of neurons in the brian does it hold?

• cerebellum (10% of entire brain)

• 50% of brain’s neurons

where does all of the cerebellum’s output come from?

* the deep nuclei- 4 masses of gray matter (4 on each side of cerebellar hemisphere) VIA superior peduncles

how is the cerebellum connected to the brainstem & how does most spinal input enter the cerebellum?

via cerebellar peduncles - enters the cerebllum via inferior peduncles

how does the cerebellum receive input from rest of brain?

via middle peduncles

what’s the main fxn of the thalamus?

limbic system/emotion, relay of visual signals

what does the thalamus act as an important gateway to?

the cerebral cortex: all input to cerebrum passes by synapses in the thalamic nuclei

why does the thalamus act as a gateway?

because it screens out info, only sending a SMALL amount to the cerebral cortex