a&p exam 4

the human nervous system is a network of ___,___,__ that works together to control all body activities (voluntary and unvountary)

nerves, brain, spinal cord

homeostatic response: receptor

receives information

detects changes or stimuli in the environment

homeostatic response: control center

process the information and decides how to respond

usually the brain or spinal cord

homeostatic response: effector

carries out response restore homeostasis

universal properties of neurons

excitability (irritability)

conductivity

secretion (chemical neurotransmitter)

excitability

respond to stimuli

a pain receptor detects a pinprick

excitability

send signals to other cells

single travels from skin to spinal cord

secretion

release neurotransmitters

motor neuron releases ACh to contract a muscle

the nervous system is divided into

central nervous system CNS - brain and spinal cord

peripheral nervous system PNS- nerves and ganglia

what are the 3 types of neurons

sensory (afferent) PNS

interneurons CNS

motor (efferent) PNS

sensory/ afferent neurons definiton

carries information to the CNS from sensory receptors

PNS

motor/efferent neurons

carry commands form the CNS to effectors (muscles or glands) or produce a response

interneurons

connect sensory and motor neurons within the CNS; integrate, process, and interpret information

structure of a neuron ADD IN PICTURE AND LABEL DENTRITES, NUCLEUS, TRIGGER ZONE, AXON, MYELIN SHEATH, SCHWANN CELL

neurosoma (cell body/soma)

lots of rough ER (Nissl body) and cytoskeleton; no centrioles

multipolar neuron

most common type in the CNS

has one axon and two or more dendrites extending from opposite ends of the soma

function: integrates lots of information and send commands to muscles or glands

bipolar neurons

has one axon and one dendrite extending from opposite ends of the soma

rare - found in special sense organs

function: relay sensory information

ex: retina of eye. olfactory mucosa (smell), inner ear (hearing and balance)

unipolar neuron

has a single process that splits into two branches

one branch acts like a dendrite (receive information form sensory receptors)

the other branch acts like an axon (sends impulse to the CNS)

cell body is off to the side

found mainly in sensory neurons of the PNS

ex: touch and pain sensory neurons (tactile)

anaxonic neuron

rare

no true axon , only dendrites

cannot generate an action potential because it does not have an axon hillock where impulses are sent and received from

found in brand and retina

function: for communication, local processing and integration of information

dendrite function

receives information

axoplasm

cytoplasm of axon

axolemma

plasma membrane of axon

what is a nucleus

cluster of somas (cell bodies) in CNS

what is a gangliion

cluster of somas in PNS

what is a nerve

bundle of axons in PNS

neuroglia : neurons ratio

10:1

neuroglia (glial cells/supportive cells) are

non-neuronal cells in the nervous system that support, protect, and nourish neurons

glial cells in the CNS

oligodendrocytes

ependymal cells

microglia

astrocytes

glial cells in the PNS

Schwann cells

satellite cells

Oligodendorcytes (CNS neuroglia)

form myelin sheaths in CNS

insulates nerve fibers; speed signal conduction

ependymal cells (CNS neuroglia)

lines internal cavities of the brain and spinal cord

secretes and circulate cerebrospinal fluid (CSF)

microglia (CNS neuroglia)

migrating macrophages (immune system cells)

clean up microorganism and dead neurons

astrocytes (CNS neuroglia)

most abundant glial cells in CNS, covering brain surface and most nonsynaptic regions in the gray matter

• support an anchor neurons to nutrient supply lines

• control chemical environment around neuron

• stimulate capillaries to forth blood-brain barrier (BBB)

Schwann cells forms ___ ____ around axon

myelin sheath

Schwann cells assist in axon _____ after injury

regeneration

surrounds neuron cell bodies in PNS ganglia; regulate nutrient and waste exchange; provides protection and structural support

satellite cells

what is myelin

• composed of 80% lipid, 20% protein

• fatty, white substance

• wraps around axon

CNS- oligodendrocytes

PNS- Schwann cell

myelination begins at

week 14 of fetal development and completed in late adolescence

what does myelin do

prevents signal loss and allows faster impulses/communication between neurons

• speed up reaction

the outer most layer of myelin is called (PNS)

neurilemma

steps of regeneration in PNS

1. axon injury

2. Schwann cell activation

3. formation of regeneration tube

4. axon regrowth

5. reconnection and remyelination

regeneration can only occur in the PNS because regeneration requires what

neurilemma and myelin

why can’t nerve fibers in the CNS regenerate

oligodendrocytes have growth inhibiting proteins

brain tumors arise from

glial cells because they can divide

what is metastasis

the process. by which cancer cells spread frothier original (primary) site to other parts of the body and form secondary tumors

why do gliomas (tumor) grow rapidly and are highly malignant

• blood brain barrier (astrocyte) decreases effectiveness of chemotherapy

• treatment consists of radiation or surgery

multiple sclerosis

• oligodendrocytes and myelin sheaths replaced by hardened scar tissue

• nerve conduction disrupted (double vision, tremors, numbness, speech defects)

• cause may be autoimmune triggered by virus

tay-sachs disease

hereditary disorder of infants of Eastern European jewish ancestry

• defective gene on chromosome 15

• accumulation of glycolipid, GM2, in myselin sheath

• blindess, loss of coordination, and dementia

• fatal before age 4

in neuron electrophysiology, potassium has an RMP of

-70mV

what is the initial phase in the action potential of neurons

local potential

once the ___ has been passed in action potential it cannot go back down, but the impulse can stay in between resting membrane potential and local potential

threshold

axon hillock is another word for

threshold

Action potential request high density of voltage gated channels

what is a refractory period

• after a neuron fires an action potential, it goes through two short recovery phases during which it cannot or can barely fire another AP

• ensures one-way signal conduction and control how often a neuron can fire

absolute refractory period

• start of depolarization to the middle of repolarization

• prevents backward propagation of the AP along the axon

• ensures one-directional signal transmission (axon hillock to terminals)

relative refractory period

• end of repolarization to hyperpolarization

• a new AP can be triggered

• prevents neurons from firing too rapidly and controls frequency of AP

signal conduction occurs on the surface of a fibers so speed depends on two factors

• diameter of fiber

• presence or absence of myelin

in unmyelintated fibers there are multiple gates along the myelin, these gates create a refractory period to

ensure that information flows in one direction

in myelinated fibers there is saltatory conduction where

the action potential jumps from one node of ranvier to the next to produce rapid transmission of nerve impulses along a myelinated axon

what is a synapse

junction where a neuron communicated with a mother neuron, a muscle cell, or a gland cell

what is a chemical synapse

junction between two neurons were neurotransmitters are related to transmit signals across a synaptic cleft

• most common type of synapse in the nervous system

what are the 3 steps of a chemical synapse

1. presynaptic neuron (axon terminal)

2. synaptic cleft

3. postsynaptic neuron

what is a neurotransmitter

chemical messengers that transmit sinters across synapses from one neuron to another

what are the 4 classes of neurotransmitters

acetylcholine

amino acids

• GABA

• glutamic acid

monoamines

• epinephrine

• norepinephrine

• dopamine

• seretonin

• histamine

neuropeptides

• Enkephalin

• Substance P

what does GABA do

stops neuron excitability

acts as a break

inhibitory

what does glutamic acid do

enhances neuron excitability

what is serotonin

mood stabilizer

what is dopamine

key role: reward

what is enkephalin

(5 chain)

stress dampener

internal pain reliever

what does substance P do

(11 chain)

transmits pain

ex: touching a hot object

what does acetylcholine do

muscle contractor

cocaine release an increased amount of

dopamine

what is cholinergic synapse

primary neurotransmitter : ACh

uses ligand gated channel

causes excitatory postsynaptic potential EPSP

what is adrenergic synapse

primary neurotransmitter: norepinephrine (NE/noradrenaline)

uses second messengers like cyclic AMP (cAMP)

second messenger opens Na channels

what is neural integration

the ability to process, store, and recall information and use it to make decisions

• based on postsynaptic potentials occurring in a cell receive chemical signals

how does neural integration work

summation

epsp+ipsp

• depolarization (EcitatoryPSP) and hyperpolarization (InhibitoryPSP)

temporal

spatial

at axon hillock/threshold

what is an engram

a pathway through the brain that forms a memory; aka a memory trace

what is synaptic plasticity

the ability of synapses to hcange

what is synaptic potentiation

reposted use of synapse makes transmission easier

what are the kinds of memory

immediate, short and long term

immediate memory

ability to hold something in your thoughts for a few seconds

• essential for reading ability

• senes of the present

may depend on reverberating circuit

short term memory

lasts few seconds to hours

• working memory

what is tetanic stimulation (STM)

rapid, repetitive signals causes build up of Ca; postsynaptic cell easier to fire

what is posttetanic potentiation

‘jogging’ memory form a few hours earlier

• Ca in axon terminal stays elevated

what is long term memory

may last days to years

what is explicit (LTM) (declarative)

events you can put into words

what is implicit (LTM)

reflexive or unconscious memory

• includes procedural (motor skill) and emotional

how do we forget

long term depression

• low frequency stimulation of a synapse results in low levels of intracellular Ca

  • low Ca activates enzyme which degrade dendrites and remove surpasses that aren’t used

Alzheimer's Disease

• deficiency of ACh and nerve growth factor (glial cells)

• diagnoses is confirmed at autopsy

treatment: ways to clear beta-amyloid or halt its production

modest results w/ NGF or cholinesterase inhibitors

what is hyperthymesia

where you can recall past memories

how complex our brain can be

brain functions when it is alive

motor control, sensation, emotion, and thought

rostral

toward the forehead

caudal

toward the spinal cord

what are the 3 major portions of the brain

• cerebrum 83%

• cerebellum 50% of neurons

• brainstem: midbrain, pons, medulla oblongata

label the brain

midbrain, pons, medulla oblongata

label the brain

cerebrum, cerebellum, brainstem

what does the brainstem do

acts as an anchor of cerebellum and cerebrum

sensory neurons (ascending) and motor neurons(descending) and perceived at the brainstem first

medulla oblongata functions

functions: respiration, heart rate, blood pressure, cough/swallowing/vomiting reflex

all sending and descending fibers connecting brain and spinal cord pass through medulla

pons functions and roles

bridge for communication between cerebrum and cerebellum

cranial nerves 5-8

sensory roles: hearing, taste

motor: eye movement

breathing rhythms and sleep centers

midbrain functions

anchors cerebrum to brainstem and relays impulses

substantia nigra