biopsych exam 1

in vivo studies

within the living; includes experiments performed on or in a living organism

ex vivo studies

outside the living

in vitro studies

experiments with biological substrates that are performed far outside their normal biological context (think in vitro fertilization)

in silico studies

studies performed using computer models/simulations

afferent fibers

carry sensory info about environment to CNS (smell, sound, taste, touch, proprioception)

efferent fibers

send info from CNS to “effectors” that effect the external environment

PNS: somatic nervous system

sensing and moving muscles

afferent fibers

efferent fibers

PNS: autonomic nervous system

regulates body’s internal environment

carries info from organs and glands to CNS

carries info from CNS to internal organs and glands

contains sympathetic and parasympathetic nervous systems

sympathetic nervous system

fight or flight

activation prepares for whole body action

increases: energy distribution (heart rate, respiration), alertness (stress hormone release (adrenaline), pupil dilation)

decreases: energy storage (digestion, hunger)

parasympathetic nervous system

rest and digest

activation prepares for whole body deactivation

increases: energy storage, digestion (intestinal motility), fat storage, hunger

decreases: energy distribution (heart rate, blood pressure, respiration, alertness)

physical protection of brain and spinal cord

skull, spinal column, meninges, fluid buffer

structures of skull

frontal bone

parietal bone

sphenoid bone

temporal bone

occipital bone

ethmoid bone

meninges

dura mater

arachnoid mater

subarachnoid space

pia mater

dura mater

tough outer layer that is closest to the skull; contains large blood vessels

arachnoid mater

middle-layer that is a web-like, fibrous structure

contains smaller blood vessels

subarachnoid space

CSF filled space

provides cushion and nutrients for the brain

contains smaller blood vessels

pia mater

delicate inner layer that firmly adheres to the brain

contains capillaries that nourish the brain

Physical protection of CNS

cerebrospinal fluid

ventricles

cerebrospinal fluid

fills subarachnoid space

fills spaces within brain and spinal cord (ventricles in brain, central canal in spinal cord)

all inter-connected

produced by choroid plexus

choroid plexus

network of small blood vessels (capillaries) in ventricles

ventricles

hollow voids in brain filled with CSF, lined with choroid plexus tissue that continually secretes CSF

blood-brain barrier

astrocytes wrap around blood vessels and selectively filter contents from blood and transport those contents into the brain

allows small molecules to pass through (nutrients)

blocks most large molecules (toxins, drugs, most bacteria)

some large molecules are carried through manually

anterior

front

posterior

back

ventral

bottom

dorsal

top

lateral

outside

medial

inside

sagittal section

divides specimen into left and right portions (like cutting a sandwich)

coronal section

divides specimen into posterior and anterior (like loaf of bread)

horizontal section

divides specimen into top and bottom (like a bagel)

white matter

fibers of passage/tracts

move info from one region to another

little processing of info

myelinated (insulated)

grey matter

much shorter axons

not myelinated

does most of the processing

internal anatomy of CNS

white matter and grey matter

gyrus

hills

sulcus

valleys

dendrites

receive information from other neurons

cell body

houses nucleus of cell (genes) and metabolic machinery

axon

carries information over distance

can be myelinated for speed

terminal/button

end of axon branch

communicated with other neurons across synapses

astrocytes

form blood brain barrier

oligodendrocytes

myelination in CNS

Schwann Cells

myelination in PNS

radial glia

scaffolding and support

microglia

immune function and signaling

cranial nerves

can have both sensory afferent connections to the brain and motor efferent connections to specific muscle groups, or just one

olfactory nerve

sensory

sense of smell

optic nerve

sensory

sense of vision

oculomotor nerve

motor

control of extraocular muscles that allow movement of eyeballs

constriction of pupils

changing of lens shape

trochlear nerve

motor

control of the superior oblique muscle of the eye that moves the eyeball down and lateral

trigeminal nerve

sensory and motor

tactile and pain sensory info from face and mouth

control of muscles used in chewing

abducens nerve

motor

control of the lateral rectus muscle of the eye that moves the eyeball outward laterally

facial nerve

sensory and motor

control of the muscles that allow for facial expressions

taste sensation on the anterior 2/3 of the tongue

vestibulocochlear nerve

sensory

detection of sound information and head positional (vestibular) info

glossopharyngeal nerve

sensory and motor

detection of somatic sensory in the middle ear and posterior 1/3 of the tongue

taste sensation on the posterior 1/3 of the tongue

controls the stylopharyngeal muscle that allows swallowing

vagus nerve

sensory and motor

control of internal organs by ANS using parasympathetic activity

accessory nerve

motor

control of sternocleidomastoid and trapezius muscles of the neck and shoulders

hypoglossal nerve

motor

control of the muscles of the tongue

communication between CNS and PNS

spinal cord nerves travel through separate pathways depending upon what info they carry

dorsal root or ventral root

sensory afferent and motor efferent fibers decussate (cross to other side of body) before reaching target

right hemisphere controls left sided muscle movements and vise versa (contralateral)

dorsal root

carries sensory afferent fibers

ventral root

carries motor efferent fibers

communication between CNS and PNS

regeneration of nerve in spinal cord is rare

trauma to spinal cord can damage nerve fibers

damage to nerve fibers can render them unable to transmit info to and from CNS

loss of peripheral function depends on where trauma occurred

cranial nerves usually unaffected by spinal cord injury

neuronal membrane

lipids have polar and non-polar groups associated with them

hydrophobic: water fearing

hydrophilic: water loving

arrangement prevents free-flow of molecules across cell membrane

resting membrane potential

separation of ions between intracellular and extracellular space allows for a difference in electrical charge to exist across cell membrane

typical resting potential -70mV

inside of cell is more negative relative to the outside of the cell by 70mV

neuron membrane potential

separation of charge

measured using electrodes

electrophysiology

Hodgkin and Huxley

first to record membrane potential

won 1963 Nobel Prize

resting potential

differences in ion concentration across the membrane

outside: Na+, Cl-

inside: K+, proteins(-)

net total = -70mV

ion channels

span lipid bilayer of neuronal membranes

permit select molecules to cross from outside of the neuron to the inside (cation vs anion)

some highly specific to one ion

permeability depends on membrane potential and their concentration gradient

concentration gradient

occurs due to separation of charges

when an element is in high concentration in one place it tends to move to an area of lower concentration

electrostatic pressure

occurs due to separation of charges

when charge of one kind accumulates in one place it tends to move away to an area of different charge

forces on sodium

higher concentration of sodium outside cell

very small amount of sodium enters the cell at rest

concentration equilibrium and electrostatic gradient both move into cell

forces on potassium

higher concentration of potassium within the cell

very small amount of potassium leaves the cell at rest

concentration equilibrium flows out, electrostatic gradient flows in

channel highly permeable at rest = leak channel

leak channels

causes ionic balance to fail

sodium-potassium pump

restores ionic balance (Na+-K+ ATPase)

exchanges 3 Na for 2 K

Na+ out, K+ in

Na+ and K+ being moved against their gradients (opposite to concentration gradient and electrostatic pressure)

process requires energy expenditure (ATP)

synapses

space between the axon terminal of one neuron and the dendrite of its neighbor

presynaptic neuron and postsynaptic neuron

neurotransmitters

chemical released by presynaptic neuron when it is activated

interact with receptors that ultimately cause closed ion channels to open and permit flow of ions

depolarization

occurs when channels open and permit positive (cations) ions to flow into the cell

more positively charged

hyperpolarization

occurs when channels open and permit negative ions to flow into the cell

more negatively charged

post-synaptic potentials

changes in the potential of the cell receiving the neurotransmitter

excitatory (Na+) and inhibitory (K+, Cl-)

excitatory post-synaptic potential (EPSP)

depolarization of the neuron

positive ion channel opens

inhibitory post-synaptic potential (IPSP)

hyperpolarization of the neuron

negative ion channel opens

Post-synaptic potentials

can differ in magnitude; different voltage changes depending on how many channels opened in response to the neurotransmitter

type depends on the neurotransmitter received

begin at synapse

move passively along dendrites and cell body (diffusion, nearly instantaneous)

magnitude of the signal lessens with distance (ion concentration decreases over space)

Post-Synaptic potential summation

how these PSPs add together determines whether that cell will pass the signal on

signal passed via action potential

occurs everywhere, critically at axon initial segment; if voltage at this spot is depolarized past certain value, action potential is generated

PSP summation: spatial

EPSPs add together

two identical EPSPs (double the depolarization)

two identical IPSPs (double the hyperpolarization)

one EPSP + one IPSP (cancel each other out)

PSPs that occur proximally to each other will impact voltage more strongly and vise versa

timing matters

PSP Summation: temporal

PSPs summate over time

PSPs generated more closely together in time will summate more strongly

action potential generation

summation required for a cell to reach it’s threshold (-65mV)

many PSPs required

like a sparkler (must hold match to it until it lights)

starts at axon initial segment; caused by opening and closing of ion channels

changes in voltage

due to passage of ions through channels

non-gated ion channel

always open (leak)

Na, K

critical for establishing the resting membrane potential

ligand-gated ion channels

open in response to neurotransmitters

critical for generating EPSP and IPSPsvol

voltage-gated ion channels

open when neuron’s membrane potential has reached a certain value

when EPSP summation at the AIS exceeds threshold, an action potential occurs

step 1 is opening of these channels

voltage-gated Na+ channels

when these channels reach a certain voltage, the channels open and Na+ flows into the cell

electrostatic pressure: interior of cell is highly negative relative to the outside (about -65mV at this point)

concentration gradient: at rest (-65mV) Na+ is more concentrated outside the cell than inside

Na+ flows into the cell and membrane potential depolarizes further

rising phase

Na+ continues to flow into cell via open voltage-gated Na+ channels

step 2: voltage increase due to influx of Na+, K+ starts moving out

K+ concentration gradient high inside cell and cell is more positive due to Na+ entry during rising phase of AP

peak voltage

step 3: once cell reaches +50mV, voltage-gated Na+ channels close due to property of channel

K+ continues to flow out of cell

K+ channels still open

neuron is highly positive relative to outside of the cell

repolarization

step 4: Na+ channels are closed, no more positive ions into the cell

cell decreases in voltage because K+ is still flowing out of the cell

K+ driven out due to concentration gradient and electrostatic pressure, membrane potential is now positive relative to the outside

hyperpolarization

step 5: as membrane potential falls, K+ channels begin to close

slow process, voltage-gated potassium channel kinetics are slow

so many K+ ions are leaving the cell that it becomes slightly hyperpolarized

membrane potential drops below resting potential value

action potential propagation

begins at axon initial segment

changes in local voltage influence the neighboring section of axon which has tons of channels (trigger voltage-gated Na+ channels to open there, each set of events that occurred at the adjacent piece of axon will now occur)

action potential passed down the length of the axon to the terminals

propagation in detail

as Na+ enters the cell, it doesn’t stay in one place (flows away from the channel as well, increases in voltage in nearby areas (if this exceeds threshold, the next voltage-gated Na+ channel will open)

hyperpolarization stops this backwards process

myelination

as action potentials travel through myelinated axons, they become passive and decrease in magnitude

myelinated neurons: action potential skips from node to node

research that is performed within or on an living organism is referred to as:

in vivo

research using tissue or cells that have been removed from a living organism and experiments performed under conditions that are as close to biologically relevant as possible is referred to as:

ex vivo