Nervous System
Respond & act to environment
Memory, thinking, feeling, reasoning
Biochemical
Network of nerve cells
Function to receive assimilate & transport information
Sensory neurons
Come from sense organs
Go to the central nervous system (CNS)
Afferent
Internuerons
Evaluate signal from sensory
Motornuerons
Carry instructions back to effector organ for action
Efferent
CNS = Brain & spinal cord
PNS = 31 paired spinal nerves & 12 paired cranial nerves
Afferent = sensory
Efferent = motor
Somatic NS = skeletal muscle
Autonomic = glands & smooth muscles
Sympathetic = response to stress (fight or flight reaction)
Parasympathetic = Normal functions
Neuron
transport information
excitable
conductive
Neuroglia
support & nourish neurons
dendrites
carry info to the neuron
axons
carry info away from neuron
nerve fiber
axon unless otherwise specified
mylinated axons
have schwan cells wrapping the axon
much faster data transport
white matter
has nodes of Ranvier
small gap between each schwan cell
unmylinated
slower
grey matter
synapse
a region between nerves
synaptic end bulb
small encapsulated bodies at the end of a nerve
synaptic vesicle
release ACh (begins synaptic transmission)
or AChE (ends synaptic transmission)
axons running same direction are bundled
white matter = mylinated axons
grey matter = unmylinated axons & cell bodies
Nerves
Bundle of axons outside of CNS
Mylinated or unmylinated
Tract
Bundle of axons inside the CNS
Ganglion (grey)
Collection of cell bodies outside the CNS
Nucleus
Collection of cell bodies inside the CNS
Spinal Cord
Starts just as brain stem leaves foramen magnum
End at L1~L2
Lower it degrades as Conus medularis
Non nervous tissue from conus to coccyx
Filum terminale
delicate strand of fibrous tissue
gives longitudinal support to the spinal cord
Cauda equinae
within the lower end of the spinal column
consists of nerve roots and rootlets from above
The space in which the cerebrospinal fluid is present is actually an extension of the subarachnoid space
Cross section of the cord
Anterior median fissure
Posterior median fissure
Grey matter appears “H” shapped
Opening on the crossbar of the H is for the canal
Divides posterior/anterior commissure
Canal is cerebrospinalfluid (CSF)
White matter fills in spaces around the grey matter
White matter tracts
Too brain
Afferent/sensory
Away from brain
Efferent/motor
Spinal nerves
Common nerve
Anterior root = motor
posterior root = sensory
The meninges
the system of membranes which envelopes the central nervous system
Dura mater
Tough outer membrane covers roots and extends the length of the cord
Sub Dural Space
Between dura mater and arachnoid
For serous fluid to lubricate
Arachnoid
Spider like webbing covers roots and extends the length of the cord
Sub arachnoid space
Contains CSF
Pia mater
Outer layer of the brain, delicate, attaches by roots of nerves
Attaches with denticulate ligaments
Bone lined with epidural fat
Spinal Nerves
31 pairs
8 cervical
1st nerve comes off before 1st CSpine
12 thoracic
5 lumbar
5 sacral
1 coccyx
Nerves leave between the vertebrae
plexus
Regrouping of the nerves
Cervical plexus
For shoulders and neck
Brachial plexus
Arm
Lumbar plexus
Down to lower extremities
Sacral
1st 3 join to form sciatic nerve (the largest nerve)
Skin & posterior thigh
Seat of reflex actions
Automatic & involuntary
Simple reflex arc
Sensory receptor
Dorsal root
Association neuron
Ventral root
Effector
Not all stimuli cause a response
Ex. Inhibition response
Brain
In the cranial cavity
Ends at foramen magnum
Dominates rest of NS
Billions of neurons
More neurological
1300grams 3pounds
Females smaller
Smaller with age
Neurons only undergo mitosis in prenatal & slightly postnatal
Roughly full size at age 18
Rapid growth during that first half
4 principal regions
Cerebrum
Cerebellum
Diacephalon
Thalymus + hypothalymus
Brain stem
Medulla oblongata + pons + mesencephalon (midbrain)
Dura mater
Periosteal layer
Meningeal layer
CSF
140ml total
Mostly water
Protein, glucose, salts, urea
Produced in choroid plexuses
Which then goes to
4 ventricles
Spaces within the brain
1 & 2 are lateral
3 slit
4 diamond shaped
CSF then goes to central canal & subarachnoid space
Circulates
Brain Stem
Continuous with the spinal cord
Structurally the same
Just a slightly different location
Medulla oblongata
White matter traces
Reticular formation
Interlacement of white and grey mater
Pyramids
Moving laterally on each side of the medulla oblongata
Decussion of the pyramids
Crossing of fibers
Why left brain controls right side of body & vice versa
VITAL control center
Respiratory
Medullary rhythmicity
Keeps breathing in rhythm
Vasomotor
Vasoconstriction & dilation
Controls blood pressure
Cardiac center
Controls rate and strength of contractions
NONvital controls
Coughing
Sneezing
Vomiting
Swallowing
Hiccups
has 9th 10th 11th & 12th cranial nerves
Pons
Horizontal groove separates from medulla oblongata
Bridge in structure & function
Connects forebrain to spinal cord & midbrain
Pnuemotaxic
Apnuetaxic
Has 5th 6th 7th & 8th cranial nerves
Midbrain
Below cerebrum
Above pons
Mostly white matter
Ventral surface
Cerebral peduncle
Rope like structures
Has 3rd 4th and part of 5th cranial nerves
Cranial nerves
Named by distribution or function
Can be motor sensory or mixed
Most are mixed
Cerebellum
2nd largest
Posterior & inferior
Deep fissures separate into lobes
Vermis hold the 2 hemispheres together
Grey outside
White inside (arbor vitae
3 functions related to skeletal muscle
Skilled movements
Posture
Coordination/equilibrium/balance
Diencephalon
Deep within cerebrum
Midbrain
Thalamus & hypothalamus
Thalamus
Circular
Major relay for sensory input
Grey Mater
Lateral walls of 3rd ventricle
Large axons enter
Sensory input
Large axons leave
Leave to cerebral cortex
1 exception is olfactory nerve
Pain temperature & touch (sensory inputs)
Hypothalamus
Below thalamus
Link between mind and body
Links nervous & endocrine systems
via the pituitary gland
Pleasure & reward center
Maintains homeostasis
Coordinator of autonomic (involuntary) activities
Causes bodily functions to shown as expressions
Produces ADH (antidiuretic hormone) or vasopressin
Produces oxytocin
Plays a central role in the waking state
controls body temperature, hunger, thirst, fatigue, sleep, rage, aggression
also controls circadian cycles
A circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological, or behavioural processes of living entities
Cerebrum
Surface is convoluted
Gyris
Raised area
Sulci
Fissures
Divides right and left hemispheres
Corpus callosum connects
External grey mater
Internal white mater
Deeper has grey islands
Cortex is thin
Yet has 6 layers
Made of billions of axons and cell bodies
4 lobes
Parietal, temporal, frontal, and occipital
Tracts of white mater
Association tracts
Connect 1 gyrus to another gyrus in the same hemisphere
Commissure tract
Connect 1 gyrus of the right hemisphere to the homologous gyrus on the left hemisphere
Found in the corpus callosum
3 functions
Sensory, motor, integrated
Displays lateralization
Example is that speech center of the brain is found is the left hemisphere
Cortex
Responsible for awareness of self, environment, feelings, and other beings
Conscious
Higher mental processes
Memory
Logic
Limbic system
Wishbone shaped
Surrounds upper end of brain stem
Emotional aspects
Behavior of survival
Autonomic nervous system (ANS)
Subconscious
Part of peripheral nervous system (PNS)
Efferent
Regulates smooth muscle, cardiac muscle & glands
Examples
Dilation of pupil
Vasoconstriction
Vasodilation
Heart rate
2 axons involved
1st preganglionic
2nd postganglionic
Can be ACh or NE (norepinephrine)
Dual innervation
Sympathetic & parasympathetic
Sympathetic
Near spinal cord
So 1st axon is short
2nd axon is long
Parasympathetic
Near organ
1st axon is long
2nd axon is short
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