Kaarten: Neuropsychologie - primer to the nervous system

nervous system

reception and processing of sensory information from external and internal environments

2 major divisions nervous system

- central nervous system (CNS)

- peripheral nervous system (PNS)

CNS

brain and spinal cord

By what is the brain protected?

skull

By what is the spinal cord protected?

vertebral column

PNS

consists of nerves, outside the CNS

2 divisions PNS

- somatic nervous system

- automatic nervous system

3 specific functions of the nervous system

1. sensory input

2. information processing and integration

3. motor output

neurons

transmit nerve impulses between parts of the nervous system

types of neurons

- sensory neuron

- interneuron

- motor neuron

sensory neuron

long axon in myelin sheath, impulses dendrites to CNS

interneurons

short axon, not covered in myelin (not all of them)

withing CNS, sum up all information from other neurons before they communicate with motor neurons

motor neuron

long axon, in myelin sheath, CNS --> nerve impulses away from the CNS to an effector

neuroglia

glial cells = support and nourisch neurons (many more than neurons)

types of neuroglia

- microglia

- astrocytes

- Schwann cells

- oligodendrocytes

microglia

phagocytic cells that help remove bacteria and debris

astrocytes

metabolic and structural support directly to the neurons

Schwann cells

forming a myelin sheath in PNS, leaving gaps = nodes of Ranvier

oligodendrocytes

form the myelin sheath in CNS

sensory receptors

special structures that detect changes in the environment

effectors

carry out out responses to environmental changes (external / internal)

3 distinct structures of neurons

- cell body

- dendrites

- axon

cell body

nucleus and other cell organelles

dendrites

short extensions, receive signals from sensory receptors or other neurons

axon

conduct nerve impulses, can be quite long

individual axons

nerve fibers

collectivly all nerve fibers of axons

nerve

myelin sheath

developed when Schwann cells (PNS) or oligodendrocytes (CNS) wrap their membranes around an axon many times

nodes of Ranvier

gaps between myelin sheaths

role myelin sheath

rate at which signals move through the neuron

gray matter of CNS, myelinated or not

no myelinated axons

white matter of CNS, myelinated or not

myelinated axons

Multiple sclerosis (MS)

myeline breaks down, more difficult for neurnos to transmit information, myelin sheath also plays an important role in nerve regeneration within the PNS

resting potential

potassium (K) diffuses out of the cell to joing sodium ions (Na)

inside of the cell positive / negative (resting potential)

negative: large, negatively charges proteins that remain in the cell

resting potential charge

-70mV

sodium potassium pump

Na+ out of the neuron and K+ back into the neuron --> recharges the cell

treshold charge for action potential

-55mV

depolarization charge

35mV

depolarization

treshold is reached, protein channels in plasma open and sodium ions rush into the cell, inside of the cell becomes positive

repolarization

immediately after depolarization channels close, potassium flow outs of the cell, inside becomes negative again

sodium-potassium pump completes action potential

action potential unmyelinated axon

action potential at one locale stimulates and adjacent part of the axon membrane to produce an action potential (1m/s)

action potential myelinated axon

action potential at nodes of Ranvier, jumping over myeling-coated portion of tha axon

= salutatory conduction (100m/s)

self-propagating

each action potential generates another, along the length of the axon

intensity of action potential

determinated by how many action potentials are generated within a given time

refractory period

after action potential, unable to conduct an action potential

= ensures a one-way direction of a signal from the cell body down the length of the axon

axon terminal

ending of axon, small swelling

synapse

close proximity between dendrites and other dendrites / cell bodies

synaptic cleft

separates the sending neuron from the receiving neuron

neurotransmitters

transmission across a synapse, stored in synaptic vesicles in the axon terminals

role of calcium in synaptic transmission

stimulating synaptic vesicles to merge with the sending membrane

excitation

neurotransmitter has caused the sodium gate to open = sodium ions diffuse into the receiving neuron

inhibition

neurotransmitter caused potassium ions to exit the receiving neurons

How are neurotransmitters removed from the cleft?

- enzymes inactivate neurotransmitter

- reabsorption: repackaging / molecular breakdown

acetylcholine (ACh)

in PNS: excites skeletal muscle, inhibits cardiac muscle, excitatory or inhibitory effect on smooth muscle or glands dependent on location

(also in CNS)

norepinephrine

excites smooth muscle in CNS: important in dreaming, waking and mood

(also in PNS)

serotonin

thermoregulation, sleeping, emotions and perception

excitatory neurotransmitter

opening sodium gates at a synapse: closer to threshold

inhibitory neurotransmitter

opening gates for potassium: further from trehshold

meninges

protective membranes of brain and spinal cord

menginitis

infection of meninges: by bacterial or viral pathogens

spinal tap

small amount of fluid is withdrawn from around spinal cord for testing

hydrocephalus

brain enlarges due to cerebrospinal fluid accumulation in children

gray matter

cell bodies and short, non-myelinated fibers

white matter

myelinated axons that run together in bundles called tracts

4 ventricles

2 lateral on each side, join at the 3th ventricle, connects with the 4th ventricle, central canal of the spinal cord joins the fourth ventricle inferiorly

foramen magnum

large opening in the skull, for the spinal cord

intervertebral foramina

small opening where spinal nerves go through

fibrocartilage intervertebral disks

separate the vertebrae

gray matter of spinal cord

centrally located (H) contains sensory, motor and interneurons

white matter of spinal cord

reas around gray matter, contains ascending tracts taking information to the brain & ascending tracts taking information from the brain

dorsal root of spinal nerve

sensory fibers entering gray matter

ventral root of spinal nerve

motor fibers exiting the gray matter

gate controle theory of pain

"gates" control the flow of pain messages from the peripheral nerves to the brain

paralysis

if the spinal cord is severed, loss of sensation and loss of voluntary movement

paraplegia

cut in the thoracic region, lower body and legs are paralyzed

quadriplegia

injury in the neck, all four limbs are usually affected

In which part of the brain are the 2 lateral ventricles?

cerebrum

In which part of the brain is the 3th ventricle?

diencephalon

In which part of the brain is the 4th ventricle?

brain stem and cerebellum

corpus callosum

connects left and right cerebral hemispheres

cerebrum

telencephalon

last center to receive sensory input and carry out integration before commanding voluntary motor responses, coordinates the activities of the other parts of the brain

deep groove

longitudinal fissue divides the left and right cerebral hemispheres

gyri

thick folds

sulci

shallow grooves

4 lobes

frontal, parietal, temporal and occipital

frontal lobe

movement and higher reasoning, smell sensation

parietal lobe

somatic sensing

temporal lobe

sound information

occipital lobe

visual information

cerebral cortex

thin, highly convoluted outer layer of gray matter that covers the cerebral hemispheres, 1 billion cell bodies: voluntary movement, thought processes: consciousness, motor, sensory and association areas

primary somatosensory area

posterior to central sulcus in parietal lobe, each part of body is sequentially represented

primary tast area

parietal lobe

taste sensation

primary visual cortex

occipital lobe

visual information

primary auditory area

temporal lobe

information from our ear

primary olfactory area

deep surface of frontal lobe

smell sensations

association areas

places where integration occurs, memories

2 associetion areas

- premotor area

- primary motor area

premotor area

organized motor functions for skilled motor activities

primary motor area

sends signals to cerebellum, which integrates them