BIO 312 exam 2 pt 1

CNS Structure

consists of the brain and spinal cord

CNS function

acts as control center for nervous system; processes information; provides short-term control over activities of other systems

PNS structure

cranial nerves and spinal nerves

PNS function

communication lines between the CNS and the rest of the body

4 supporting cells of CNS

1. Astrocytes
2. Microglia
3. Ependymal cells
4. Oligodendrocytes

2 supporting cells in the PNS

1. Satellite cells
2. Schwann cells

Astrocyte Function (CNS)

maintains blood brain barrier, structural support, regulate ion, nutrient, helps anchor things to the CNS, recycle and absorb neurotransmitters, form scar tissues

Microglia function (CNS)

remove cell debris, wastes, and pathogens by phagocytosis

ependymal cells (CNS)

lines ventricles (brain) and central canal (spinal cord), circulation, monitoring of cerebrospinal fluid

oligodendrocytes (CNS)

myelinate CNS axons, provide structural framework

Satellite cells (PNS)

surround neuron cell bodies in ganglia, regulation O2, CO2, nutrient and neurotransmitter levels around neurons in ganglia

Schwann cells (PNS)

create myelin sheath in PNS, surround all axons in PNS, responsible for myelination of peripheral axons, participate in repair process after injury

oligodendrocytes vs schwann cells

Oligo - in CNS, work on many axons; Schwann - in PNS, work on one axon, wrap around many times

neuron

a nerve cell; the basic building block of the nervous system

synaptic cleft

The narrow gap that separates the presynaptic neuron from the postsynaptic cell.

presynaptic neuron

neuron that sends the signal

postsynaptic neuron

the neuron on the receiving end of the synapse

axolemma

cell membrane of axon

perikaryon (soma)

cell body of a neuron

dendrites

Branchlike parts of a neuron that are specialized to receive information.

axons

a part of a neuron that carries impulses away from the cell body

Telodendria

Series of fine, terminal extensions branching from the axon tip.

terminal boutons

Branched endings of an axon that transmit messages to other neurons

anaxonic neuron

many dendrites but no axon, help in visual processes

bipolar neuron

a nerve cell that has a single dendrite at one end and a single axon at the other end

unipolar neuron

a neuron with one process extending from its cell body

multipolar neuron

A neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system.

myelinated

has multiple wrappings of schwann cells or oligodendrytes

unmyelinated

does NOT have multiple wrappings of schwann cells or oligodendrytes

sensory neuron

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

motor neuron

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

interneuron

Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs

gray matter

Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and unmyelinated axons

white matter

Whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths.

gyri

ridges of the brain (brain convolutions)

sulci

shallow grooves (brain convolutions)

nerves

nerves are collections of neurons in the PNS and may contain multiple diff types of info (sensory or motor) with cell bodies in ganglia

Tracts

collections of neurons in the CNS with only one type of info; cell bodies in nuclei

cortex of brain

outer layer of gray matter; Formed from neuronal cell bodies; Located in cerebrum and cerebellum;

nuclei of brain

clusters of cell bodies within the white matter of the central nervous system

ganglia

clusters of neuron cell bodies in PNS

afferent pathway

Sensory pathway that relays information to the central nervous system.

efferent pathway

A motor pathway that relays information from the central nervous system to the rest of the body.

excitable cells

cells that are able to respond to certain stimuli by producing electric signals; can conduct/propagate electrical charges

basic neuron characteristics

highly differentiated, amitotic, incapable of regeneration, long-lived, high metabolic rate, dependence on glucose and O2

4 regions of the brain

1. Cerebral hemispheres; 2. Diencephalon; 3. Brain stem; 4. Cerebellum

cerebral hemispheres function

The "thinking parts" and the fiber tracts connecting those to each other and to brain-stem

diencephalon function

memory processing and emotional response

brain stem

Connects the brain and spinal cord

cerebellum function

process and store information, coordinates voluntary movements (posture, balance, speech)

kinetic energy

energy due to motion

potential energy

Energy that is stored and held in readiness

what is the charge of inside the cell

70mV

Where is K+ more concentrated?

inside the cell

Where is Na+ more concentrated?

outside the cell

Where is Cl- more concentrated?

outside the cell

where is ca2+ more concentrated?

outside the cell

Ohm's law

V \= IR: V: voltage; I: current; R: resistance

what is the definition of current?

flow of charged ions in body fluids

how does diameter affect resistance of flow?

the larger the diameter the less resistance there is to flow

reference electrode

located outside of the cell membrane

recording electrode

recording tip inside the neuron

in to out convention

describe the membrane potential from the perspective of the recording electrode

voltmeter

A device used to measure voltage, or electrical potential energy difference

what 3 things does the resting membrane depend on?

1. the gradients for Na+ and K+ between cytosol and ECF; 2. Permeability of the membrane to Na+ and K+; 3. Activity of the 3Na+ 2K+ ATPase

depolarization

becomes less negative than rest (more positive); Na+ or Ca2+ channels are open and flowing into cell

hyperpolarization

becomes more negative than rest Cl- or K+ channels are openelectrical potential opposes this chemical potential favors this

Repolarization

returns to rest

chemically (ligand) gated channels

open or close depending on the presence or absence of a specific chemical that binds to the channel protein

location of ligand gated channels

dendrites and soma membrane

voltage gated channels

open or close in response to changes in membrane potential

location of voltage gated channels

axonal membrane

Graded potential

fizzle out along membrane; result form opening ligand fated channesl; amplitude caries with stimulus intesisty; 2 types (EPSP, IPSP)

Action potential

at axonal membranes allow transmission over long distances

EPSP

Excitatory postsynaptic potential; a slight depolarization of a postsynaptic cell, bringing the membrane potential of that cell closer to the threshold for an action potential; Na+ channels open

IPSP

Inhibitory postsynaptic potential; a slight hyperpolarization of the postysynaptic cell, moving the membrane potential of that cell further from threshold; K+ channels open

Temporal summation

Summation by a postsynaptic cell of input (EPSPs or IPSPs) from a single source over time; one channel opens multiple times

Spatial summation

The sum of multiple synapses firing at different locations at one time to create a net effect.

threshold potential

The minimum membrane potential that must be reached in order for an action potential to be generated.

threshold stimulus

stimulation level that must be exceeded to elicit a nerve impulse or a muscle contraction

absolute refractory period

the period immediately following the firing of a nerve fiber when another action potential cannot be stimulated no matter how great a stimulus is applied

relative refractory period

A period after firing when a neuron is returning to its normal polarized state and will fire again only if the incoming message is much stronger than usual

continuous conduction

the step-by-step depolarization and repolarization of each adjacent segment of the plasma membrane; nmyelinated axons; slow

saltatory conduction

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials; jumping of action potentials from node to node

why does an action potential occur?

b/c of summation of graded potentials at trigger zones

Substrates of metabolism

glucose + O2 ; aerobic metabolism ; Fatty acids -\> TCA cycle(liver) -\> TCA cycle (brain) ; get glutamate, glutamine and GABA (neurotransmitters)

choroid plexuses function

produce cerebrospinal fluid

ependymal cells function

produce and circulate cerebrospinal fluid

three layers of membrane that protect the brain?

meninges

inner layer of meninges

pia mater (very delicate)

middle layer of meninges

arachnoid mater

Outer layer of meninges

dura mater (tough mother)

ventricles of the brain

canals in the brain that contain cerebrospinal fluid

hydrocephalus

accumulation of fluid in the cavities deep within the brain

cerebrospinal fluid (CSF)

plasma-like clear fluid circulating in and around the brain and spinal cord

Blood Brain Barrier (BBB)

physiological barrier between the circulatory system and the central nervous system that establishes a privileged blood supply, restricting the flow of substances into the CNS

axon hillock (trigger zone)

initial segment of axon where the action potential is initiated

4 phases of action potential

1) depolarization; 2) overshoot; 3) repolarization; 4) undershoot

2 periods of action potential

1) absolute refractory period; 2)relative refractory period

Hodgkin positive feedback cycle

occurs when inward and capacitive current through voltage-gated Na+ channels bring the next patch of axonal membrane to threshold potential; triggers the opening of more voltage-gated Na+ channels