Physiol Psych Exam 1

Golgi and Ramon y Cajal

Golgi: in 1873 he discovered the black reaction known today as the golgi stain; shows the entire body of a nerve cell including dendrites, cell body, and axon

Ramon y Cajal: perfected Golgi's staining technique; observed that axons didn't touch the neighboring dendrites and cell bodies of cells nearby; Cajal used his observations to lay down the pillars of the Neuron Doctrine

technique: Golgi

structural insight: Ramon y Cajal

Neuron Doctrine pillars

1. the neuron is the basic structural and functional unit of the nervous system

2. neurons are discrete cells, not a continuous network

3. law of dynamic polarization: transmission of electrical signals is undirectional; signals travel from the dendrites to the axons in a neuron

what makes neurons unique from other cell types?

neurons are specialized for information processing; they receive info, integrate it, carry it, then transfer it

each of the 4 functional zones of a neuron & their primary roles

1) Input Zone

- the dendrites

- receive info

- where neurons collect & process information either from the environment or other cells

2) integration zone

- cell body

- integrate info

- where the decision to produce a neural signal is made

3) conduction zone

- axon

- carry info

- where information can be electrically transmitted over great distances

4) output zones

- axon terminals

- transfer info

- where the neuron transfers information to other cells

multipolar neuron

- multiple dendrites, single axon

- stereotypical neuron

- likely found in the CNS & PNS

bipolar neuron

- single dendrite, single axon

- cell body found somewhere in between dendrites & axons

- found in special sensory organs such as the nose, eye, & ear

unipolar neuron

- single process the splits

- input zone (dendrites) & output zone

- cell body in the middle; kind of off to the side

- limited to embryonic stage; found in spinal nerve ganglia, cranial nerve ganglia, & sensory pathways

presynaptic vs. postsynaptic

presynaptic: side of the synapse that sends information (found at the axon terminal)

postsynaptic: other side of the synapse that receives information (found at dendrites)

information flow goes from:

presynaptic (axon terminal) -> synaptic gap -> postsynaptic neuron (dendrites)

synaptic cleft

the gap that separates the pre- and post-synaptic membranes; ~20-40 nm

synaptic vesicles

- contain neurotransmitters

- in response to electrical signals, the vesicle fuses with pre-synaptic membrane & releases neurotransmitters into cleft

neural communication

neurotransmitters cause changes in the neuron!

- receptors on dendrites & soma bind neurotransmitters that were released from synaptic terminals of other neurons

- these neurotransmitters cause changes in the neuron

- the axon hillock determines if these changes should trigger an action potential

- the action potential travels down the axon to the synaptic terminals

- once the action potential reaches the terminals, it causes a release of neurotransmitters into the synaptic cleft

- the neurotransmitters bind to receptors on another neuron & repeat

myelin

a fatty, insulated sheath / protein that wraps around the axons on neurons

- covers & insulates axons

- increases transmission speed & improves energy efficiency of action potentials along the axons

produced by the glial cells: oligodendrocytes & schwann cells

- oligodendrocytes: form myelin sheath in brain & spinal cord (CNS)

- schwann cells: form myelin sheath for cells outside the brain & spinal cord (PNS)

nodes of ranvier

points on axons without myelin; these allow the action potential to regenerate

2 factors that determine conduction & velocity in axons

axon & myelin:

wider axon + more myelin = faster conduction

axon hillock

determines if neurotransmitters should cause changes in the neuron

- located between the cell body and the axon

- it's the site of integration because it's the decision maker that determines whether a neuron will be changed or not

motor proteins involved in axonal transport

kinesin & dynein

- kinesin: from soma to terminal; anterograde

- dynein: from terminal to soma; retrograde

they transport vesicles along microtubules in the axons between the some & terminals

kinesin & dynein use _____ as "tracks" for transport

microtubules

neural plasticity

- the continual remodeling of neural connections

- dendritic spines facilitate neural plasticity as they are bumps that increase the surface area of dendrites

axons often divide into _____ _____

axon collaterals

when they divide into axon collaterals, they allow a neuron to innervate more than one postsynaptic cell

glial cells

- almost as much glia as neurons

- various forms of support

- contributes to information processing

types of glial cells

there are 4 types:

1) astrocytes - involved with formation & pruning; regulate blood flow; involved in many processes that receive neuronal input & monitor activity of nearby synapses

2) microglial cells - small cells; activate processes which continuously extend & contract; remove debris from injured cells; neuronal remodeling; pain reception

3) oligodendrocytes - form myelin sheath in brain & spinal cord (CNS)

4) schwann cells - form myelin sheath everywhere outside the brain & spinal cord (PNS)

issues that occur with astrocyte dysfunction

edema (swelling); epilepsy

issues that occur with microglial cell dysfunction

inflammation; neurodegeneration

if glial cells keep dividing, _____ can form

tumors

multiple sclerosis

autoimmune disease that attacks oligodendrocytes; demyelinates axons of CNS

collective term for the caudate and putamen

striatum

gross neuroanatomy

the study of the structure & organization of the nervous system that can be seen with the naked eye

why gross neuroanatomy is important for understanding nervous system organization

establishes where functions live (organization), how distant regions talk to each other (white matter highways like the corpus collosum), and how the brain protects itself structurally (the ventricular system)

2 main divisions of the nervous system & how they're anatomically distinguished

CNS: brain and spinal cord

PNS: everything else that isn't the brain and spinal cord; connects the CNS to the rest of the body

somatic vs autonomic nervous system in terms of control & consciousness

somatic nervous system

- connect brain & major muscle and sensory systems

- voluntary & conscious (mostly)

- motor nerves transmit information from the CNS to muscles, organs, and glands (controlled by cortex) (efferent = exit)

- sensory nerves convey information from the body to the CNS (goes to cortex) (afferent = arrive)

- consists of cranial and spinal nerves

- acetylcholine & norepinehphrine

autonomic nervous system

- 3 major divisions

1) sympathetic: prepares the body for action; fight or flight

2) parasympathetic: rest and digest

3) enteric: local network of neurons that govern function of the gut

- has components located centrally & peripherally

- acetylcholine only

- not conscious or voluntary

the cranial sensory and motor nerves involved in the PNS

cranial nerves: 12 pairs

5 motor, 3 sensory, 4 both

sensory

I: olfactory (smell)

II: optic (sight)

VIII: vestibulocochlear (inner ear; hearing & balance)

motor

III: oculomotor (muscle that moves the eyes)

IV: trochlear (muscle that moves the eyes)

VI: abducens (muscle that moves the eyes)

XI: spinal accessory (neck muscles)

XII: hypoglossal (tongue muscles)

both

V: trigeminal (sensory - face, sinuses, teeth) (motor - jaw muscles)

VII: facial (sensory - tongue, soft palate) (motor - facial muscles, salivary glands, tear glands)

IX: glossopharyngeal (sensory - taste & other mouth senses) (motor - throat muscles)

X: vagus (sensory - information from internal organs) (motor - internal organs)

3 major diviions of the autonomic nervous system

sympathetic nervous system: fight or flight (acetylcholine & norepinephrine)

parasympathetic nervous system: rest & digest (acetylcholine)

enteric nervous system: local network of neurons that govern the function of the gut (acetylcholine but many others used)

where preganglionic vs. postganglionic neurons are located in the autonomic system

preganglionic neurons: run from the CNS to the autonomic ganglia (groups of neurons located outside the CNS; located in the brain & spinal cord

postganglionic neurons: run from the autonomic ganglia to targets in the body (everywhere else)

directional terms

dorsal / superior: top

ventral / inferior: bottom

medial: down the midline

lateral: to the sides

contralateral: opposite sides

ipsilateral: same side

rostral: to the front

caudal: to the back

proximal: near the center/trunk

distal: away from the center/trunk

nerve vs. tract

nerve: a group of fibers (axons) traveling together in the PNS

tract: a group of fibers (axons) traveling together in the CNS

nucleus vs. ganglion

nucleus: a collection of cell bodies in the CNS

ganglion: a collection of cell bodies in the PNS

gray vs white matter

gray matter: cell bodies and dendrites (lack myelin)

white matter: comprised of axons with white myelin sheaths made of glia

gyri vs. sulci vs. fissure

gyri: ridges; bumps; convolution of the cortex of the cerebral hemisphere, separated by sulci or fissures

sulci: furrows; cracks; grooves in the surface of the cerebral hemisphere between gyri; smaller than a fissure

fissure: major groove in the surface; larger than a sulcus

neural tube 3 subdivisions

1. forebrain (prosencephalon)

2. midbrain (mesencephalon)

3. hindbrain (rhombencephalon)

the 5 subdivisions the neural tube's 3 subdivisions turn into

telencephalon; diencephalon; mesencephalon; metencephalon; myelencephalon

1. forebrain (prosencephalon)

- telencephalon: cerebral hemisphere with cortex and subcortical structures

- diencephalon: thalamus & hypothalamus

2. midbrain (mesencephalon): subcortical motor & sensory components

3. hindbrain (rhombencephalon)

- metencephalon: becomes the cerebellum and pons

- myelencephalon: also called the medulla

corpus callosum

a bundle of axons (white matter) that connects the two cerebral hemispheres

primary lateralized specializations of the left vs right hemisphere

left: analysis of information

- recognizing serial events

- controlling sequences of behavior

- language (production & understanding)

right: synthesis of information

- putting isolated elements together to perceive a whole (spatial awareness)

- language (prosody)

4 primary cortical areas, their locations, & their primary functions

primary motor cortex (M1)

- posterior frontal lobe

- contains neurons that control movements of skeletal muscles

primary somatosensory cortex (S1)

- anterior parietal lobe

- primary input is from the somatosensory system

primary auditory cortex (A1)

- superior temporal lobe

- primary input is from the auditory system

primary visual cortex (V1)

- posterior occipital lobe

- primary input is from the visual system

insular cortex

- the primary taste cortex

- also emotion and reward processing

- location: hidden from the cortical surface; normally covered by the rostral superior temporal lobe and caudal inferior frontal lobe

which primary cortical areas correspond to each type of topographic organization

somatotopic (M1 - primary motor cortex; S1 - primary somatosensory cortex)

tonotopic (A1 - primary auditory cortex)

retinotopic (V1 - primary visual cortex)

gustotopic (taste)

chemotopic (smell)

sensory association cortex vs. motor association cortex

sensory association cortex

- location: parietal lobe

- receive information from the regions of the primary sensory cortex

motor association cortex

- location: region of the frontal lobe rostral to the primary motor cortex

- also known as the premotor cortex

columnar organization

- neurons in the cortex are organized into cortical columns

- each column perpendicular to cortical layers & serves as a unit to process information

how cortical columns relate to the laminar organization

laminar organization: the rows; horizontal; the 6 layers of the cortex that determine where information comes from & where it goes (input & output)

cortical columns: columns; vertical; determine what specific feature is being processed (local computation)

- the relationship: cortical columns are vertical computational units that slice down through 6 horizontal laminar layers

- layers dictate the flow of information; columns cluster neurons together that care about the exact same sensory feature

- the bridge: pyramidal cells use their vertical apical dendrites & horizontal basal dendrites to physically link the layers and columns together

pyramidal cells

- pyramid-shaped cell body in layers

- apical dendrite extends to outermost cortex

- basal dendrites spread horizontally from the cell body

- use their vertical apical dendrites & horizontal basal dendrites to physically link the laminar layers and cortical columns together

basal ganglia main components

- a cluster of nuclei

- important in motor control

- reciprocally connected with the cortex

- gray matter structures within the white matter of the cortex

what is the basal ganglia made up of ____ and ____, _____ ____, and interacts with the _____ _____ and the _____ _____

caudate and putamen, the globus pallidus; subthalamic nucleus and the substantia nigra

clinical conditions associated with basal ganglia dysfunction

parkinson's disease, huntington's disease, tourette syndrome, dystonia, hemiballismus, OCD, addiction

primary function of the basal ganglia in relation to the cortex

motor control

limbic system

includes structures important for learning & memory, cognitive functions, emotional regulation, and sense of smell

- combines sensory information from external and internal environments to help control the internal environment

- structures: amygdala, hippocampus, cingulate gyrus, fornix, mammillary bodies, septal nuclei, olfactory bulb, stria terminalis

amygdala vs. hippocampus

amygdala: fear, emotion, threat, social situations

hippocampus: memory, mood; consolidation of explicit & spatial memory

mammillary bodies

memory circuits (hippocampal fibers project here); involved in Korsakoff's syndrome

diencephalon: what are the 3 main types of thalamic nuclei & how do they differ in their cortical connections

diencephalon: the thalamus & hypothalamus

thalamus: a cluster of nuclei that relay information

the 3 main types of thalamic nuclei

1. relay nuclei: transmit information to and from specific regions of the cerebral cortex

2. intralaminar nuclei: connect diffusely to large areas of cortex

3. reticular nucleus: wraps around the other nuclei & regulates their activity

how does the hypothalamus control the pituitary gland & why is this relationship important?

how it controls the posterior pituitary

- controlled neurally

- hypothalamic axons tunnel directly into it to release oxytocin & ADH

how it controls the anterior pituitary

- controlled chemically/vascularly

- hypothalamus secretes releasing/inhibiting hormones into the

how it controls the anterior pituitary

- controlled chemically/vascularly

- the hypothalamus secretes releasing/inhibiting hormones into the hypophyseal portal system

this is important because it's the ultimate bridge between the nervous system (brain) and the endocrine system (hormones), allowing the brain to scale up tiny electrical signals into massive, body-wide homeostatic responses via negative feedback loops

the two main structures of the epithalamus

the pineal gland and the habenula

pineal gland

- located on the posterior roof of the the third ventricle, dorsal to the thalamus

- circadian rhythms and melatonin production

habenula

- located just anterior to the pineal, also on the roof of the diencephalon

- limbic system connections, reward/aversion processing

structures included in the brainstem vs the hindbrain & how they overlap

brainstem

- midbrain (mesencephalon)

- pons (metencephalon)

- medulla (myelencephalon)

hindbrain

- cerebellum (metencephalon)

- pons (metencephalon)

- medulla (myelencephalon)

they overlap at the pons (metencephalon) and the medulla (myelencephalon)

midbrain: what does the word "tectum" mean and what are the two main structures it contains?

tectum is the midbrain sensory systems; when you see tectum, think "roof"

the 2 regions of the tectum process visual & auditory information

- superior colliculi (vision)

- inferior colliculi (audition)

what is the periaqueductal gray & what types of behaviors does it influence?

involved in pain & influences complex behaviors such as defense, aggression, or reproduction

what does "tegmentum" mean and what are the main motor-related structures it contains?

tegmentum: midbrain motor centers; think "floor"

motor-related structures:

- substantia nigra: has neurons that release dopamine; interacts with basal ganglia

- red nucleus: communicates with motor neurons in the spinal cord

- reticular formation: involved with sleep & arousal, temperature control, and motor control; stretches from the midbrain to the medulla

- ventral tegmental area: has neurons that release dopamine; involved in reward pathway

which two midbrain structures contain dopamine-releasing neurons, and how do their functions differ?

the substantia nigra & the ventral tegmental area release dopamine

substantia nigra: interacts with the basal ganglia

ventral tegmental area: involved in reward pathway

what is the reticular formation and through which brainstem regions does it extend?

involved with sleep & arousal, temperature control, and motor control

begins in the midbrain but descends into the pons into the medulla

the pons

- the word pons means "bridge"

- it contains an area for coordination of REM sleep

- it contains a nucleus called the locus coeruleus which makes norepinephrine

what vital functions are regulated by the medulla?

contains cranial nerve nuclei and nuclei that regulate breathing and heart rate

what significant axonal pathways through the medulla

all axons from the brain to the spinal cord passes through the medulla

what does cerebellum mean

cerebellum means "little brain"

what is the primary function of the cerebellum

it's involved in motor coordination and learning

what anatomical structures connect the cerebellum to the brainstem

it's connected to the brainstem by cerebellar peduncles (large band of white matter composed of multiple tracts)

what is the "connectome" and why is mapping it important for neuroscience research?

it's a comprehensive, high-resolution map of all the neural connections within an organism's nervous system

why it's important

- shifts from the focus of an isolated brain to integrated network computing

- helps identify connectopathies

- shows how plasticity rewires physical circuits during learning

what is DTi and what aspect of brain structure does it visualize

diffusion tensor imaging

- MRI where a signal is detected by the movement of water molecules

- detects how water travels along white matter tracts

- different colors indicate direction/trajectory of axons

what is the function of the corpus callosum & what type of neural tissue comprises it?

the corpus callosum is a bundle of axons (white matter) that connects the 2 cerebral hemispheres; connects the two hemispheres across the midline

how do the anterior and posterior commissures compare to the corpus callosum?

- connect hemispheres to each other

- smaller than the corpus callosum

the functional hierarchy from the spinal cord through the telencephalon main concept

telencephalon: cerebral hemispheres with cortex & subcortical structures

functional hierarchy

1. spinal cord

2. brainstem (medulla, pons, midbrain)

3. diencephalon (thalamus, hypothalamus)

4. telencephalon (cerebral cortex, basal ganglia

the 3 meninges in order from outermost to innermost & their characteristics and functions

dura mater: tough outermost sheet

arachnoid: substance between the dura matter and pia mater that cushions the brain in cerebrospinal fluid (CSF)

pia mater: delicate innermost layer

2 main functions of cerebrospinal fluid

- acts as a shock absorber

- provides an exchange between blood and brain

the production & flow of cerebrospinal fluid (CSF) through structures

CSF is produces in the choroid plexus

- choroid plexus: highly vascular tissue that lines the lateral ventricle & produces CSF

- ~500 mL per day

- the brain/spinal cord contains 120-150 mL

CSF flow pathway:

lateral ventricles -> third ventricles -> fourth ventricle -> subarachnoid space -> absorption sites -> central canal of spinal cord

1. lateral ventricles: via interventricular foramina / foramina of monro

2. third ventricles: via cerebral aqueduct / aqueduct of sylvias

3. fourth ventricle: via 3 openings: 2 lateral foramina of luschka & the median foramen of magendie

4. subarachnoid space: around brain & spinal cord; CSF flows down the spinal cord

5. absorption sites: primarily arachnoid granulations in sagittal sinus

6. central canal of spinal cord: connects with the subarachnoid space around the cord

what tissue produces most of the CSF & in which ventricles is it primarily made?

most of the CSF is produced in the choroid plexus

- choroid plexus: highly vascular tissue that lines the lateral ventricles and produces CSF

- primarily made in the lateral ventricles

what type of glial cells line the lateral ventricles & help move the CSF?

ependymal glial cells line the lateral ventricles & help move the CSF

what is the function of the arachnoid layer in relation to cerebrospinal fluid?

the arachnoid layer in the meninges cushions the brain in CSF

what are arachnoid granulations & where are they located?

arachnoid granulations: small projections of the arachnoid membrane through the dura mater into the superior sagittal sinus; the CSF flows through them to be reabsorbed into the blood supply

the location and function of the superior sagittal sinus in CSF circulation

- located in the midline just dorsal to the corpus callosum, between the 2 cerebral hemispheres

- the primary site where old CSF drains out of the brain & back into the venous circulatory system

what causes hydrocephalus & how does it affect the brain's ventricles?

hydrocephalus

- a condition where all or some of the brain's ventricles are enlarged

- caused by an obstruction that impedes the flow of CSF

- causes the brain's ventricle to pathologically widen and dilate

what are the major arteries that supply blood to the brain?

the carotid arteries

stroke & the two main types

a stroke is caused by the rupture or blockage of blood vessels, leading to insufficient blood supply

- hemorrhagic stroke: occurs when a rupture in an artery allows blood to leak into the brain

- ischemic stroke: clots or other debris prevent blood from reaching a certain region of the brain

what is the penumbra in the context of stroke treatment?

salvageable, but threatened, tissue

what is the circle of willis & which major structures form it?

circle of willis: all major cerebral arteries are joined via communication arteries to form the circle; the joining of arterial paths provides a possible alternative route for blood flow if any of the main arteries should be damaged or blocked

formed by: anterior cerebral artery, middle cerebral artery, posterior cerebral artery

why is the circulatory arrangement of arteries in the body advantageous for brain blood supply?

the circle of willis

what types of cells and structures create the blood-brain barrier?

BBB: higher resistance in brain capillaries restrict passage of large molecules from the blood into brain tissue

made of endothelial cells with tight junctions; some support by astrocytes

3 types of molecules that can cross the BBB & 3 types that cannot

can cross the BBB:

- small, uncharged molecules (O2, CO2)

- fat-soluble molecules (some vitamins; psychotropic drugs)

- essential polar nutrients

cannot cross the BBB

- viruses and bacteria

- chemicals

- other nutrients (vitamins, hormones)

how do nutrients like glucose get across the BBB if it's selective

active transport is required to get nutrients into the brain

what are circumventricular organs and why is the BBB incomplete in these regions?

circumventricular organs: regions around the ventricles where the BBB is incomplete, allowing direct contact between blood and brain tissue for sensing and regulatory function

the BBB is incomplete in these regions because it's leaky

what is the glymphatic system & what does it help clear from the brain?

glymphatic system: a recently lymphatic system found in the brain; provides a flow of CSF through the inferior of the brain that helps to clear cellular debris, proteins, and other waste

how does the CSF flow through the brain's interior in the glymphatic system?

1. CSF flows from the CSF-filled subarachnoid space into the periarterial space surrounding fine arterioles that penetrate the brain, and is propelled along by the pulsing of the artery walls

2. CSF enters the brain tissue via specialized channels called aquaporin in the end feet of astrocytes surrounding the arterioles, and then flows through the brain, accumulating waste material as it goes

what is the fundamental difference between electrical and chemical signaling in neural communication?

electrical signaling: information flows within a neuron

chemical signaling: information passes between neurons

what causes the threshold to be reached at the axon hillock?

synaptic activity on the neuron itself

what is synaptic delay and when does it occur in neural transmission?

synaptic delay: delay between action potential reaching the axon terminal and creating a postsynaptic potential

it occurs after an action potential has traveled down the axon & arrived at the presynaptic axon terminal, but before a new electrical change - a postsynaptic potential - is successfully generated in the receiving dendrite

EPSP: excitatory postsynaptic potential

produces a small local depolarization, pushing the cell closer to threshold