UNIT 7: NERVOUS SYSTEM

nervous system

fast channel, body's main control and communication network

5 major functions of the nervous system

receiving sensory inputs

integrating information

controlling muscles and glands

maintaining homeostasis

establishing and maintaing mental activity

central nervous system

a division of the nervous system that consists of the brain and spinal cord

peripheral nervous system

a division of the nervous system that consists of the nerves outside the brain and spinal cord, subdivided into the motor (somatic and autonomic) and sensory division

somatic nervous system

conscious, voluntary motor responses

central nervous system to skeletal muscles

autonomic nervous system

involuntary body movement

central nervous system to cardiac and smooth muscles and glands

sympathetic nervous system

responsible for the fight or flight response

parasympathetic nervous system

responsible for rest and digest

enteric nervous system

sensory and motor neurons in the gastrointestinal tract

neuron

cell of the nervous system

accepts stimuli, sends action potentials, and trasmit signals to other nurons or effector glands

parts of the neuron

cell body, processes (dendrites, axons)

cell body

part of the neuron

contains the nucleus, primary site of protein synthesis

dendrites

part of the neuron

receives information from the cell body, shorter

axons

sends information away from the cell body, longer

nerve

multiple axons surrounded by various layers of connective tissue

these are bundled axons outside the brain and spina cord

plexus

bundle of nerves outside the brain and spinal cord

3 layers of connective tissue surrounding the nerves

endoneurium

perineurium

epineurium

endoneurium

a layer of connective tissue surrounding the nerves

surrounds each axon or nerve fiber

perineurium

a layer of connective tissue surrounding the nerves

heavier connective tissue that surrounds nerve fascicles

epineurium

a layer of connective tissue surrounding the nerves

surrounds the whole nerve, dense connective tissue that binds nerve fascicles together to form a nerve

multipolar neuron

many dendrites with one axon, such as interneurons and motor neurons

bipolar neuron

one dendrite and one axon, components of sensory organs

pseudo-unipolar neuron

single process from cell body and subdivides with an axon that splits into sensory receptors and CNS, most sensory neurons are this kind

glial cells of the central nervous system

astrocytes, ependymal cells, microglia, oligodendrocytes, myelin sheath, node of ranvier

astrocytes

provide structural support for neurons and blood vessels

form blood-brain barrier function and inhibit other signals from nearby neurons

ependymal cells

produce cerebrospinal fluid

microglia

immune defense cells that phagocytize

oligodendrocytes

provide insulation and cover axons, produce mlyelin sheath

myelin sheath

covers axons, not continuous

node of ranvier

gaps in myelin sheath

glial cells in the periphereal nervous system

schwann cells, satellite cells

schwann cells

enclose unmyelinated axons of PNS

has the neurilemma which is the outermost layer

satellite cells

surrounds cell bodies in sensory and autonomic ganglia, encompass work, support neurons, nutrients, protection from heavy metal

types of nervous tissue

gray matter, white matter

gray matter

group of neurons cell bodies and their dendrites, minimal myelin sheath

cns: cortex in brain surfaces, nuclei in deeper areas

pns: swelling cell bodies called ganglia

white matter

bundles of parallel axons with myelin sheath

cns: nerve tracts or conduction pathways propagating action potentials

pns: bundles of axon and connective tissue forming nerve bundles

action potential

electrical signals produced by the nervous system

membrane potential

measure of electrical properties by the nervous system

resting membrane potential

energy difference across the membrane of a resting cell

flow of ions across cell membrane

based on concentration and electrical charge

leak or nongated channels

flow of ions, always open, ion moves down their concentration gradient

gated channels

chemical, voltage-gated

sodium

outside the cell membrane, positive proteins

potassium

inside the cell membrane, negative proteins

nervous communication stages

stage 1: generation of action potential

stage 2: action potential conduction

stage 3: synapse

stage 1: generation of action potential

resting membrane potential

depolarization

repolarization

return to resting conditions

stage 2: action potential conduction

action potential is generated and propagated along the cell membrane through continuous conduction and saltatory conduction

continuous conduction

an action potential conduction

slow conduct of action potential in unmyelinated aons by activating local currents in adjacent parts of cell membrane

saltatory conduction

an action potential conduction

rapid transmission in myelinated axons through node of ranvier

stage 3: synapse

known as the neuromuscular junction, neuron to neuron, neuron to muscle, neuron to cells of effector organs, pass action potentials

3 major parts: presynaptic terminal, postsynaptic membrane, synaptic cleft

conditions to release neurotransmitters

reach action potential to presynaptic terminal

opening of calcium-gated channels

synaptic vescicles

contains neurotransmitters

na channels open

postsynaptic cleft is depolarized and action potential will result

k and ca channels open

postsynaptic cleft is more hyperpolarized, action potential is inhibited

types of neurotransmitters

cholinergenic, biogenic amines, amino acids, peptides

acetylcholine

a cholinergenic

excitatory at neuromuscular junctions (muscle contracts), can be both inhibitory and excitatory in autonomic nervous system

norepinephrine

a biogenic amine

excitatory effect at some cns and ans synapses

dopamine

a biogenic amine

excitatory at cns, inhibitory to ans, rush of adrenaline

serotonin

a biogenic amine

inhibitory effect at cns synapse

gamma-aminobutryic acid (GAMMA) and glycine

am amino acid

inhibitory effect at cns

endorphin

a peptide

blocks pain pathways, endogenous morphine

neuronal pathways

converging pathways, diverging pathways, local summation, temporal summation

converging pathways

a neuronal pathway

2+ neurons synapse with the same postsynaptic neuron (multipolar)

diverging pathways

a neuronal pathway

axon of one neuron divides and synapses with 1+ postsynaptic neuron (pseudo-unipolar)

spatial summation

a neuronal pathway

multiple local current potential synapse into 1 postsynaptic neuron

temporal summation

a neuronal pathway

local potential overlaps in time

major regions of brain

cerebrum, diancephalon, cerebellum, brain stem

cerebrum

largest, subdivided into left and right hemispheres

seperate hemispheres through longitudinal tissue

gyri

part of the cerebrum

folds on the surface that increseases surface area at cerebral cortex

sulci

part of the cerebrum

intervening grooves or tumors on the surface, small hills

corpus callosum

part of the cerebrum

white matter, connects the cerebral hemispheres

lobes of cerebral hemisphere

frontal love, parietal love, occipital love, temporal lobe

frontal lobe

controls voluntary and motor functions, motivation, aggression, mental action, mood, and olfactory

parietal lobe

main center for sensory info like touch, pain, temperature, and balance

central sulcus

part of the parietal lobe

separates the frontal and parietal lobes

insula

part of the parietal lobe

deep in the lateral fissure

perception of taste

independent

occipital lobe

receiving signal, responding visual inputs, not distinctly separate from other lobes

temporal lobe

olfactory and auditory

psychic cortext

part of the temporal lobe

anterior and inferior areas

lateral tissue

separates most of temporal lobe from other lobes

diencephalon

between cerebum and brain stem

thalamus

part of the diencephalon

largest, 2 large lateral parts, sensory input, passageway for cns to brainstem, autonomic response, influence mood, regulate all sensory inputs

epithalamus

part of the diencephalon

superior and inferior, emotional and visceral responses to odors, also influence pineal gland (puberty development)

hypothalamus

part of the diencephalon

controls body temperature, hunger, satiety, thirst mechanism, emotional response

cerebellum

attached to brain stem by cerebral peduncles

maintain balance, muscle tone, and coordinating fine motor movements

communicate with propioceptive neurons (position sets)

brain stem

connects brain and spinal cord

midbrain

part of the brain stem

above the pons, coordinate eye movement, pupil size, and lens shape

contains ascending tracts from spinal cord → cerebrum

descending tracts from cerebrum → spinal cord of cerebellum

substantia nigra

part of the brain stem (midbrain)

black nuclear mass that regulates general body movement

pons

part of the brain stem

bridging cerebrum and cerebellum, bridge between major brain regions and contain pathways responsible for breathing

medulla oblongata

part of the brain stem

important for 3 vital parts (heart, vessels, breathing)

pyramid decussation

descending nerve tracts that cross and go to somatic motor neurons of the spinal cord

the crossing of descending motor fibers in the medulla

foramen magnum

passageway of the medulla oblongata to the spinal cord

reticular formation in brainstem

group of nuclei scattered in brainstem

regulates cyclical motor function: respiration, walking, chewing

major part in reticular activating system: role in arousing and maintaining consciousness, regulates sleep-wake cycle

reticular activating system

maintaining consciousness and sleep-wake cycles

basal nuclei

group of functionally-related nuclei

responsible for planning, organizing, maintaining posture

ex. corpus striatum, substantia nigra

basal ganglia

founded deep, has 2 circulators (stimulatory, inhibitory)

stimulatory circuits

a basal ganglia

leads to voluntary muscle activity

inhibitory circuits

a basal ganglia

activate the opposite muscles, antagonist muscles, of the muscles

sensory input

travel to cerebrum, cerebellum, and provides info

allow cns to control motor and voluntary functions

brainstem and diencephalon helps maintain homeostasis

perception

conscious awareness of stimuli from sensory input

ascending tracts

transmit info from periphery to various parts of the brain

consists of: spinothalamic tract, dorsal column, sensory tract, spinocerebellar tract