Nervous and Endocrine System Flashcards
Central Nervous System
includes spinal cord and brain. In the “center” of the body
Peripheral Nervous System:
includes autonomic and somatic nervous systems
Somatic Nervous System
connects to skeletal muscle
Autonomic Nervous System
connects to
smooth (involuntary) muscles
Autonomic Nervous System is further divided into the…
Sympathetic
Nervous System (usually causes effects associated with emergency situations) and the Parasympathetic
Nervous System (promotes activities associated with a normal state).
SENSORY NEURON:
afferent neuron - takes a message from a sense organ to CNS. has long
dendrite and short axon
MOTOR NEURON:
efferent neuron- takes
message away from CNS to a muscle fiber or gland. Short dendrites, long axon.
INTERNEURON:
association neuron or
connector neuron): completely contained within CNS. Conveys messages between parts of the system. Dendrites, and axons, may be long or short.
Nerve Conduction is…
an ELECTROCHEMICAL CHANGE that moves in one direction along the length of a nerve fiber. It is electrochemical because it involves changes in voltage as well as in the concentrations of certain ions.
Resting Potential
When not conducting impulses, there is a voltage difference across the
membrane of the axon of about -60 mV. The negative charge on the
inside of the axon is due to the presence of large negative ions. There are more sodium ions on the outside of the axon compared to the inside of the axon, and more potassium ions on the inside compared to the outside.
ACTION POTENTIAL:
POTENTIAL: if a nerve is stimulated by electric shock, pH change, or mechanical stimulation, a nerve impulse is generated, and a change in potential can be seen.
RECOVERY PHASE:
between transmissions, K+ ions are returned to the inside of the axon, Na+ to the outside. This is done actively
The speed of nerve impulses is?
quite rapid. due to the structure of the nerves. Specifically, the MYELIN SHEATH of most nerve fibers (this sheath is formed by tightly packed spirals of the cell membrane of Schwann cells) and the interruptions or gaps of the sheath called the NODES OF RANVIER.
Myelinated or non-myelinated neurons transmit info faster?
Myelinated because impulse can “skip” over the sheath where as non-myelinated has to go step by step each time
Synapse:
the region between end of an axon and the cell body or dendrite to which it is attached.
Synaptic Endings:
swollen terminal knobs on the ends of axon terminal branches.
Presynaptic Membrane:
the membrane of the axon synaptic
ending.
Postsynaptic Membrane:
the membrane of the next neuron just beyond the axon’s synaptic membrane.
Synaptic Cleft:
the space between the presynaptic and the postsynaptic membranes
Neurotransmitter Substances (neurotransmitters):
chemicals that transmit the nerve impulses across a synaptic cleft.
Synaptic Vesicles:
contain the neurotransmitters. Contained near the surface of synaptic endings.
Transmission across a synapse is — because only the – have synaptic vesicles that
are able to release – to affect the potential of the next neurons.
one-way, ends of axons, neurotransmitters
Sequence of events for synapes
- neurotransmitters take nerve impulses across synapses.
Neurotransmiters are small molecules. They can be single amino
acids, short chains of amino acids, or derivatives of protein. - proper brain and nervous system function depends on the proper
balance of excitatory and inhibitory synaptic transmitters.
Excitatory transmitters: include ACETYLCHOLINE (ACh),
ADRENALIN (epinephrine), NORADRENALIN (norepinephrine),
SEROTONIN (derived from the amino acid tryptophan), and
DOPAMINE. - A single neuron may receive
information from thousands of
neighbouring neuron through
thousands of synapse. Some of the
messages are excitatory (i.e. they tell
the neuron to “fire”) while others may
be inhibitory (i.e. they tell the neuron
not to fire). - Whether or not a neuron “fires” off an action potential at any particular
instant depends on its ability to
integrate these multiple positive and
negative inputs.
Reflexes
automatic, involuntary responses to changes occurring inside or outside the body. Can
involve the brain (e.g. blinking) or not involve brain (e.g. withdraw hand from hot stove).
Reflex arc
main functional unit of the nervous system. It allows us to react to internal and
external stimuli.
Path of a simple Reflex Arc:
Receptor (e.g. in skin) - generates a nerve impulse
2. Sensory Neuron - takes message to CNS. Impulses move along dendrite, proceed to cell body (in
dorsal root ganglia) and then go from cell body to axon in gray matter of cord.
3. Interneuron - passes message to motor neuron
4. Motor neuron - takes message away from CNS to axon of spinal nerve
5. Effector - receives nerve impulses and reacts: glands secrete and muscles contract
AUTONOMIC NERVOUS SYSTEM
made of motor neurons that control the internal organs AUTOMATICALLY (usually unconsciously).
SYMPATHETIC NERVOUS SYSTEM:
is especially important during EMERGENCY SITUATIONS and is associated with “FIGHT OR FLIGHT” reaction.
PARASYMPATHETIC NERVOUS SYSTEM
The parasympathetic System promotes all the
internal responses associated with a RELAXED
state. For example:
* causes the pupils to contract
* energy diverted for digestion of food
* heart rate slows
CENTRAL NERVOUS SYSTEM
consists of the BRAIN and SPINAL CORD. The CNS lies in the mid-line of the body and is the place where sensory information is received and
motor control is initiated.
Spinal Cord:
contains central canal filled with cerebrospinal fluid and the highway of neurons
GRAY MATTER
(inner layer) containing cell bodies of neurons and short fibers.
Looks kind of like the a butterfly with open wings.
* in grey matter, dorsal cell bodies function primarily in receiving sensory
information, and ventral cell bodies send along primarily motor information.
WHITE MATTER
(outer layer) containing long fibers of interneurons that run
together in bundles called tracts that connect the cord to the brain.
* within white matter, ascending tracts take information to the brain, descending tracts in the ventral part
carry information down from the brain.
MEDULLA OBLONGATA
Lies closest to spinal cord. Controls heart rate, breathing, blood pressure,
reflex reactions like coughing,
sneezing, vomiting, hiccoughing,
swallowing. An “ancient” part of
brain. The Pons also participates in
some of these activities, having
ganglia that regulate the breathing
centers in the medulla, for example.
THALAMUS
receives sensory
information from all parts of the body
and channels them to the cerebrum.
It is the last portion of the brain for
sensory input before the cerebrum.
Serves as a CENTRAL RELAY
STATION for sensory impulses coming up spinal cord and other parts of brain to the cerebrum. Receives
all sensory impulses (except for smell) and sends them to appropriate regions of the cortex for
interpretation.
CEREBELLUM
controls balance and complex muscular movement. It is the second largest portion
of the brain. Butterfly-shaped. Functions in muscle coordination and makes sure skeletal muscles
work together smoothly. Responsible for maintaining normal muscle tone, posture, balance. It
receives sensory information from the inner ear (which senses balance).
HYPOTHALAMUS
one of the most important sites for the regulation of homeostasis. It maintains
internal environment, contains centers for hunger, sleep, thirst, body temperature, water balance,
blood pressure.
PITUITARY GLAND
(serves as a link between the nervous system and
the endocrine systems).
CORPUS CALLOSUM
(Y)- horizontal connecting piece between the two hemispheres of the brain.
Transmits information between the two cerebral hemispheres. It has been noted that severing the
corpus callosum can control severe epilepsy (which is thought to be caused by a disturbance of the normal
communication between the RAS and the cortex), but also means the two halves of brain don’t
communicate with each other normally and will function separately. Each half has its own memories and
“style” of thinking. Sometimes you’ll hear this discussed as “right brain” versus “left brain” thinking.
CEREBRUM
largest, most prominent, most highly developed portion of the brain.
* Consciousness resides only in this part of the brain.
FRONTAL
movement, higher intellectual processes (e.g. problem solving, concentration, planning,
judging the consequences of behavior, moving your tongue and mouth to speak (left side only).
PARIETAL
sensations e.g. touch, temperature, pressure, pain. Understanding speech, using words
TEMPORAL
hearing, smelling, interpretation of experiences, memory of visual scenes, music, and
complex sensory patterns.
OCCIPITAL
vision, combining visual experiences with other sensory experiences.
5 ways a drug can act with synapses
- drug stimulates release of neurotransmitter.
- drug blocks release of neurotransmitter
- drug combines with neurotransmitter preventing its
breakdown - drug mimics neurotransmitter
- drug blocks receptor so neurotransmitter can’t be
received
* These drugs can be as common as the caffeine found
in coffee, theophylline in tea (both block the action of
adenosine, a chemical that inhibits the release of
neurotransmitters).
* Nicotine enhances the action of acetylcholine. Some
drugs (e.g. Thorazine) also affect cognitive or thinking
processes. Mood-altering drugs particularly affect the
RAS.
- Drugs either promote or decrease the action of neurotransmitters, either stimulating or inhibiting the
action of excitatory transmitters or inhibitory transmitters. Stimulants either enhance excitatory
transmitters or block the action of inhibitory transmitters. Depressants either enhance the action of an
inhibitory transmitter or block the action of an excitatory transmitter.
