functions of nervous system
- Sensory input
- integration
- motor input
Sensory input
gathers sensory info form outside and inside the body
integration
responsible for processing & interprets sensory input and decides how to respond
motor input
causes a response called motor output, by activating muscle & glands
Central Nervous System
- CNS
- includes the brain & the spinal chord-control center, interprets sensory input & dictates motor response
Peripheral nervous System
- PNS
- cranial and spinal nerves, communicating between CNS and the rest of the body
2 subdivisions of PNS
a. sensory (afferent) fibers
b. motor (efferent) fibers
Sensory afferent division
arrival, info coming in, somatic and visceral sensory nerve fibers (axons) take info from receptors to CNS
- somatic afferent fibers
- Visceral afferent fibers
somatic afferent fibers
take signals from your skin, skeletal, muscles and joints
visceral afferent fibers
conducts signals from your organs
Motor efferent division
(going away) include motor nerve fibers , they take information away from effectors
- somatic nervous system
- Autonomic nervous system(sympathetic, parasynpathetic)
Somatic nervous system
take impulses from CNS to skeletal muscles
-voluntary
Autonomic nervous system-CH 14
includes visceral or involuntary - CNS to smooth cardiac muscles & glands, sending signals from CNS to involuntary
Sympathetic division
fight or flight
- involuntary
- speed things up
Parasympathetic division
- resting & digesting
- maintaining day to day activities
nervous system
master controlling and communicating system of the body.
Graded potential
Short-lived, localized change in membrane potential; often occurring from the dendrites to the cell body. Membranes here have lots of leaky channels , so signals don’t get far
Hyperpolarization
Some K+channels remain open, while Na+ channels reset; inside of the cell is temporarily more negative than usual
chemical synapses
- much more common, release and receive chemical neurotransmitters
1) AP arrives at axon terminal, open volt gated channels Ca2+
2) Ca2+ release, releases neurotransmitter crosses synaptic cleft
3) Binding of nrtmters to the postsynaptic membrane opens ion channels, result GP
4) Nrtmters effects are terminated by reuptake via astrocytes, degradation by enzymes, or diffusion away from the synapse
action potential
Long distance signals generated by nerve or muscle cells; brief reversal of membrane potential pf about 100mV (from -70 to +30 mV)
- these signals do not decrease with distance.
- travel whole length of axon
3 functions of nervous system
1) sensory input- gathers sensory info from outside & inside body
2 )integration- responsible for processing & interprets, sensory input and decides how to respond
3) motor output- causes a response called MO, by activating muscles and glands
divisions of nervous system
CNS & PNS
- CNS
- PNS
a. sensory(afferent) division -(somatic & visceral afferent fibers)
b. motor (efferent) division -(somatic & autonomic–sympathetic & parasympthetic–nervous system)
neuroglia
much more common than neurons, support neurons by producing chemicals to help neurons find connections, promoting neuron health and growth, and speeding up action potential conduction
-found in CNS & PNS
6 Types of Neuroglia
1) CNS- Astrocytes- starshaped , abundant, help with synapse formation, participate in information processing in the brain
2) CNS- Microglia- small ovoid thorny process, monitor health of nearby neurons, turn into macrophages
3) CNS- Ependymal cells- squamous to columnar shaped, cilia, they split the CSF(Cerebrospinal fluid) from the cavities around the cells
4) CNS- Oligodendrocytes- branching, form myelin sheaths
5) PNS- Satellites cells- like Astrocytes
6) PNS- Schwann cells-srround neuron cell bodies-form myelin sheaths- they can help with regeneration of damaged nerves
structural classification -sensory (afferent)
taking signals from skin or internal organs to CNS
-cell bodies are outside the CNS
structural classification- motor (efferent)
-transmit signals from CNS to effectors(muscle/glands)- multi-polar- cell bodies are inside the CNS
structural classification- interneurons (association neurons)
between sensory & motor neurons, most in CNS, most multi-polar
resting membrane potential
difference in voltage across the cellular membrane (40-90mV)
-inside of the cell is negatively charged, usually polarized
leakage channels
always open
chemical(ligand)-gated channels
this opens when the appropriate chemical binds
voltage-gated channels
open or close in response to changes in membrane potential
mechanically gated channels
open in response to physical deformation
ex. touch and pressure receptors
What 2 things can produce a change in membrane potential?
1) changes in ion concentration on either side
2) changes in membrane permeability
what two factors do the speed of nerve signal conduction depend on?
1) axon diameter
2) degree of myelination
continuous conduction
this occurs on unmyelinated axons and its slow
saltatory(jumping) conduction
this is in myelinated axons, the signal jumos from one node of Ranvier to the next very fast, prevents very little signal to be lost
Excitatory synapses and EPSPs
Binding at these synapses opens chemically gated channels, lets NA+ in and K+ out; net flow of Na+ in- depolarization (inside more positive)
Inhibitory synapses and IPSPs
This opens chemically gated channels lets K+ out or Cl- in. More polarized, more negative, less likely to create an action potential
spatial summation of postsynaptic neuron
-if you have enough pre-synaptic neurons stimulating the post synaptic neuron
temporal summation of postsynpatic neuron
summation of one or more of pre-synaptic neurons transporting EPSP on rapid succession , summation over time.
synaptic potentiation
repeated or continuous use of synapse enhances the excitability of the post synaptic neuron
presynaptic inhibition
occurs when a release of an excitatory neurotransmitter by one neuron is inhibited by activity of another
Acetylcholine Ach
-nrtmter-stimulates skeletal muscles, also used by subneurons
Biogenic Amines
- nrtmter- dopamine, norepinephrine, epinephrine, serotonin and histamine
- these play a role in emotions and regulate the biological clock
Amino Acids
- nrtmters- GABA(drinking alcohol), glycine, aspartate and glutamate
- usually act as inhibitory
Peptides
Substance P-mediates pain signals; as well as endorphins which reduce pain perception
Purines
ATP is a nrtmter in both CNS and PNS; produces fast excitatory response at certain receptors. Adenosine also acts outside of cells as an inhibitor, caffeine blocks adenosine receptors
nitric oxide and carbon monoxide
nrtmters that pass quickly into cells binding to intracellular receptors
- NO involved in formation of new memories, sends signals to increase synaptic strength, excessive can lead to brain damage
- CO performs similar function in mempry, but different pathway
excitatory nrtmters
excitatory causes depolarization and by depolarization- makes cell membrane more positive, makes it closer to initiating AP
inhibitory neurotransmitters
causes hyperpolarization
ex. Ach is excitatory at neuromuscular junctions but inhibitory at cardiac muscle.
direct neurotransmitter
nrtmter bind to and open ion channels directly, cause rapid responses in postsynaptic
indirect neurotransmitter
-“second messenger”-slower but causes longer lasting responses , neurotransmitter works through 2nd messenger
divergent neuronal circuit
- one signal triggers response signal on to increasing numbers of others(neurons)
ex. signals from the brain to thousands of muscle fibers.
converging neuronal circuit
you have input from several signals going into one area
ex. when different sensory stimuli, sight, sound, smell have same effect
reverberating/oscillating neuronal circuit
creates a chain of neurons, signal going through a chain over and over (continuous)
ex. sleep wake cycle
parallel after-discharging
incoming signal segregated into many pathways, and info delivered by each pathway is dealt with simulltaneously by different parts of neural activity
-signal from many neurons to one, but occurs one at a time in short bursts(as opposed to coverging)
serial processing
the whole system works in a predictable all or nothing manner with one neuron stimulating the next and so on
-reflexes- rapid automatic responses to stimuli, they go to the spinal chord and back out bypassing the brain
parallel processing
integrating input from many pathways and information dealt with by different neuronal circuits
dorsal horn (posterior horn)
-gray matter-has sensory function and all are interneurons
ventral horn ( anterior horn)
-gray matter- somatic motor
what kind of info does dorsal and ventral roots carry?
a. dorsal root-sensory
b. ventral root- motor info
gyri
- singular-gyrus
- ridgges
sulci
- singular- sulcus
- grooves - they separate the gyri
fissures
-deep grooves - these separate regions of the brain
5 lobes of each cerebral hemisphere
- frontal
- temporal
- parietal
- occipital
- insula
gray matter
contains mostly nerve cell bodies, dendrites, neuroglia , blood vessels and unmyelinated
white matter
regions of the brain and spinal chord containing dense collections of myelinated fibers(insulation for nerve cells), they’re white becuase they are fatty and function as insulation for axons
nucleus (nuclei)
-cluster of cell bodies in the CNS
ganglion
- ganglia
- in PNS , cluster of cell bodies
tract
- axons in CNS
- bundles of axons
nerve
- axons in the PNS
- bundles of axons
primary motor cortex
- in cerebrum- located in precentral gyrus of frontal lobe
- voluntary skeletal muscle control-motor homunculus
Broca’s area
- left hemisphere of frontal lobe
- motor speech area- directs lips, tongue, mouth for speech
primary somatosensory cortex
- postcentral gyrus of parietal lobe
- receives sensory input from the body
- sensory homunculus
prefrontal cortex
- anterior association area
- involved with things like intellect, complex learning and personality
posterior association area
- includes parts of Temporal, Parietal, and occipital
- known as Wernicke’s area or the “sensory speech area” because it enables you to understand written and spoken language
basal nuclei
- AKA basal ganglia
- function: start, stop and monitor intensity of movements ordered by the cortex and coordinate several movements occuring at once ( swinging your arms as you walk)
thalamus
- inner room- gateway to cerebral cortex
- function: relay station for info coming into the cortex
- relay afferent (arriving) impulses from all senses to the sensory cortex for interpetration
- all other inputs ascending to the cerebral cortex go through thalamic nuclei
- involved in memory
hypothalamus
-below thalamus
- connects pituatary gland by the infundibulum
-function: as the main visceral control center of the body, it helps to maintain homeostasis
7 functions:
1) autonomic control center
2) center of emotional response
3) body temp regulation
4) regulate food intake
5) regulate water balance, thirst
6) regulate sleep/wake cycle
7) control endocrine system functioning
epithalamus
- most dorsal portion of diencephalon
- pineal gland: endocrine gland that secretes melatonin which controls sleep/wake cycles; involved in mood and jet-lag
- choroid plexus- forms the CSF
superior and inferior colliculi
-are nuclei that are visual and auditory reflex centers that make us do things such as turn our head toward a loud noise
substantia nigra
- associated with (part of ) basal nuclei of cerebrum
- looks dark because of melatonin
- is a precursor for the nrtmter dopamine
pons
- middle area pons= bridge
- composed of conduction tracts
- some muclei help medulla regulate normal rythym of breathing
medulla oblongata
- most inferior AKA “primitive brain”
- continuous with spinal cord
- decussatioin of pyraminds:crossing over of fibers so right motor cortex controls left side of body
- visceral motor nuclei found here:
1. cardiac center
2. vasomotor center
3. respiratory center
4. vomiting, hiccupping, swallowing, coughing, sneezing
functions of cerebellum
- receives input from : motor areas , sensory input from proprioceptors in skeletal muscle, tendons and joints, allows you to know your body position and how you’re moving
- cognitive function: sends information to the brain stem nuclei, word association and puzzle solving
- symptoms resulting from damage to cerebellum : loose muscle tone-become clumsy
function of limbic system
-function: emotional brain
function of reticular formation
- function:
- contains the Reticular Activating System (RAS)
- governs arousal & awareness of the brain as a whole
- filters out 99% of all sensory input
what are the 3 meninges
- Dura mater- outermost-tough mother
- Arachnoid mater- thin middle layer-means spider
- Pia mater-innermost means gentle mother
why is blood brain barrier important?
- living protective barrier between blood and CNS that maintain a stable environment for the brain
- no other body tissue is dependent on a constant internal environment as the brain
- if brain is exposed to such chemical variations(in the blood) the neurons would fire uncontrollably
Huntington’s disease
is a hereditary disease with degeneration of basal nuclei (coordinated movements)
- symptoms: chorea(wild, jerky movements, cannot control)
- occurs in middle age
- due to defective mitochondria so lactic acid builds up
Parkinson’s disease
- symptoms: are rigidity , shuffling gate, inability to communicate
- this disease is caused by degeneration of the neurons in the substantia nigra, preventing them from releasing dopamine
meningitis
inflammation of the meninges- cause pressure on the brain
encephalitis
inflammation of the brain itself
hydrocephalus
- “water in the brain”
stroke
- cerebrovascular accident (CVA)
- AKA stroke
- 3rd leading cause of death
Alzheimer’s disease
progressive degenerative disease of the brain