Transcript The Nervous system

The Nervous system
The nerve cell is the basic unit of
communication in the vertebrate
nervous system
Three Classes of neurons
• The Neural circuit consists of
– Sensory neurons
• receptor for stimulus
– Interneuron
• integrate signals
– Motor neuron
• transfer signal to effector (muscle)
Anatomy of a Neuron
• Cell body: functional
portion
• Dendrites: short
extensions that receive
signals
• Axon: long extension
that transmits impulses
How does a neuron hold and
move info?
• A neuron at rest has a voltage difference
across the plasma membrane called a resting
voltage potential
• An action potential is when this charge across
the membrane is briefly switched
• The action potential moves down the
membrane at a rapid pace.
• Ap can move faster over mylenated portions
is called saltatory conduction
How does a signal move from
one neuron to another?
• A synaptic cleft divides 2 neurons
• The AP will not move across the synaptic
cleft
• Neuro transmitters are released by the
signal cell to the receiver cell
• Move by diffusion
Types of chemical synapse
• Acetylcholine: neuromuscular junctions,
glands, brain and spinal cord
• Norepinepherine: affects brain regions
concerned with emotions, dreaming
Paths of information flow
• Signals between the
brain and spinal
cord move to the
body regions by
nerves
• Sensory nerves
move a signal
towards the brain
and spinal cord
• Motor neurons move
a signal from the
brain or spinal cord
to the body
Divisions of the nervous
System
• Central nervous
system
• Peripheral nervous
system
• CNS
• PNS
• Is the brain and
spinal cord
• all nerves that carry
signals to and from
the CNS
Parts of the PNS
• Sensory Division carries info to the
brain and spinal cord.
• Motor Division carries info from the
brain to the bodies effectors (things that
do the work)
The Motor division of the PNS
has 2 divisions
• Somatic nerves
relay commands to
and from skeletal
muscle
• Voluntary control
• Autonomic nerves
send signals to and
from smooth
muscles
• Involuntary control
• Sympathetic
• Parasympathetic
The autonomic divisions
• Parasympathetic
• Sympathetic
• slow down the body
activity when the
body is not under
stress
• increase overall body
activity during times
of stress, excitement
or danger
• fight or flight
response
• Rest and digest
• hormone epinephrine
Sympathetic and
Parasympathetic
• Are Antagonistic
• Work towards the automatic,
subconscious maintenance of
homeostasis.
Components of the CNS
• Spinal cord
– 31 pair of spinal
nerves
– Grey matter
– White matter
– Controls some reflex
actions like bladder
emptying
• Brain parts
– Hindbrain
• medulla oblongata
• cerebellum
• pons
– Midbrain
– Forebrain
• cerebrum
• thalamus
• hypothalamus
Other parts of the CNS
• The two cerebral hemispheres communicate
through the corpus collosum
– left verbal skills
– right nonverbal skills such as music math, abstract
• Brain cavities and Canals
– cerebrospinal fluid surrounds and fills in cavities in
the brain
– Blood Brain barrier- controls what moves into the
brain. Will prevent infections.
Our state of consciousness
• The CNS governs sleeping, dozing,
daydreaming and full alertness
• neurons of the reticular activating
system control the changing levels of
consciousness by releasing serotonin.
Limbic system
• Involved in both memory and emotion.
• Is involved with behavior.
• Odors pass through this system and
may influence or behavior and
emotions.
Memory
• Association is the
linkage of information to
structural and chemical
changes
• short term- few bits
lasts a couple of hours
• Long term- permanent
and limitless
• The most important
info goes rapidly into
long term storage
• memory is stored in
a form resistant to
degradation
• Possibly caused by
changes in
synapses.
Tips on studying
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Concentrate on what you study.
Minimize interference.
Study takes time.
Break material into smaller portions.
Rephrase materials in your own words.
Test yourself to see what you know.
Disorders of the nervous
system
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Trauma
Infections
Transmission and synaptic defects.
Abnormal growth
Sensory Reception
If a tree falls in the woods with no
one to listen does it make a
sound?
Receptors
• Are the actual structures that respond to
our environment.
• Each receptor will respond to a different
signal.
• Essentially translators, they translate an
energy into one that can be perceived
by the brain.
Sensory systems consist of
• Each system has 3 parts
– 1) sensory receptors.
– 2) pathway to the brain.
– 3) region of the brain that recognizes this
section.
Types of sensory Receptors
• Chemoreceptors
• olfaction and taste
• Mechanoreceptors • touch, stretch, hearing,
equilibrium
• Thermoreceptors • radiant energy, infared
• pain receptors
• Nociceptors
• Photoreceptors
• light
Sensory Pathways
• If a receptor is stimulated enough it results in
an action potential.
• The action potential reaches the brain.
• The stronger the stimulus the greater number
of action potentials reach the brain.
• Sensory adaptation is when the action
potentials are reduced by a constant
stimulus.
• Certain receptors will not adapt.
Somatic sensations
• Touch & Pressure • Mechanoreceptors that respond to
changes or constant pressure
• Temperature
• Pain
• Muscle sense
• Increase in temperature causes and
increase in AP
• Respond to intense stimulus on other
receptors, cannot be ignored
• Mechanoreceptors give
measurement as to the location of all
the muscles and bones in a given
moment.
Limb position, length and
tension
• How do we know
where we are at?
Referred pain
Taste and Smell
• Gustation: Taste
• Receptors located on
tongue, roof of mouth,
throat and palate
• Four tastes
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sweet
sour
bitter
salty
• Olfaction: smell
• detect chemicals
• olfactory bulbs in
brain interpret smell
• smell is often
combined with
emotion
Taste
• Taste Bud 25 cells
• Taste hairs project into
mouth
• Hairs contain receptors
• Categories
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Sweet
Sour
Salty
bitter
Hearing
• Acoustical receptors
detect vibrations
• The ear
• In the organ of corti
loudness is determined
by The total number of
cells that are stimulated
• Pitch depends on
frequency of vibration
Balance
• Vestibular apparatus
• Closed system of
fluid filled sacs
• Contain otoliths that
detect changes in
orientation as well
as acceleration
• Overstimulation of
the hair cells of the
vestibular apparatus
results in motion
sickness
Vestibular apparatus
The Eye
Structure of the eye
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Outer sclera (white) (is all the way around)
Cornea (clear)
Pupil (opening to the back)
Lens (transparent)
Retina (back side has photoreceptors and
support material)
• Fovea has highest concentration of
photoreceptors.
Regulating light amount
• The iris adjusts to amount of light
entering the eye.
• The lens goes through accommodation
to adjust lens curvature (as we age the
lens cannot buldge enough to focus on
a close object)
Light must reach the sensors
by going through neurons.
• Outermost layer is pigmented to absorb
light not absorbed by the sensors
• Photoreceptors are in middle layer
• Translucent neurons and ganglions are
on top of the photoreceptors.
Production of Action Potentials
by Rods and Cones
• Within these cells flattened disks
contain photopigment
• When this protein absorbs light it
changes conformation, if enough are
activated they cause an action potential.
• Rods contain rhodopsin and are most
sensitive to dim light
• Cones contain different pigments
Rods and Cones
• Bright light tends to use more cones,
300x more sensitive
• Dim light uses Rods and Rhodopsin, it
is broken apart by light and must be
remade (hence the 5-10 minute wait to
see in darker areas)
Signaling to visual perception
• Photoreceptors are
in the retina
• When rods or cones
are stimulated they
send a signal to the
brains visual cortex.
• In the brain the final
interpretation makes
sense of sight
Problems with the Eyes
• Retinal detachment: retina separates
form choroid
• Cataracts: lens becomes opaque
• Color blindness: Inability to distinguish
colors, is a genetic disease, lacks
specific types of cones
The Endocrine system
The oldest method of control is
using a signal molecule that
moves from one part of the body
to the other
The Endocrine System
Regulates
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Salt and water balance
Blood pressure
Stress responses
Digestion
Cellular metabolism
Production of RBC’s
Growth and development
Location of Endocrine Glands
Hormones and other signal
molecules
• Hormones: molecules secreted by glands
into the blood that move to a nonadjacent
target
• Neurotransmitters: act on a directly adjacent
cell
• Local signaling molecule: act quickly and
degrade quickly
• Pheromones: secreted by glands and target
cells in other organisms
Signaling Mechanisms
• Requirements
– Cells that secrete the signal molecule are
either within a gland or nervous tissue
– The signal molecule
• Steroid hormone (fat soluble will move
through the plasma membrane)
• Non steroid hormone (peptides and other
molecules must bind to a receptor on the
cell)
– Target cell
Target cell activities
• Different hormones activate different
cellular response mechanisms
• No all cells have receptors for all
hormones:
Does
not fit
bind,
Good
rx
occurs
reaction
A cell with aNo
single
receptor on it
Three possible hormones
Characteristics of the
Endocrine system
• Each hormone acts only on certain cells
• Cells respond only when they have
receptors
• Is slower than nervous system control
• Endocrine and nervous system to
interact with one another.
Interaction of Endocrine
System and Nervous System
Negative Control using
Hormones
The pancrease an endocrine
and an exocrine gland
• Glucagon: raises blood sugars, release
of stores and AA metabolism
• Insulin: lowers blood sugars opposes
glucagon
• Somatostatin: inhibits secretion of the
above enzymes
Bracketing using hormones
Regulation of Blood Calcium
concentration
• Increase Calcium
– Parathyroid Hormone: removes calcium
and phosphate from bone, increase
absorption, retention of calcium in kidneys
• Decrease of Calcium
– Calcitonin
Oxytocin and nursing, a
cascade of events
• At the end of pregnancy, Estrogen rise.
• Uterus produces more oxytocin receptors
• Fetus produces oxytocin, starts a cycle of
material production of oxytocin
• Oxytocin is a part of the neuroendocrine
reflexes and will help in the smooth muscle
contractions which cause the release of milk.