Nervous System Test 1
Neuron Physiology [2] --GRADED POTENTIALS
short-lived, localized change in membrane potential in response to stimulus; Occurs at the CELL BODIES and dendrites--light, heat, mechanical pressure, or neurotransmitters are stimuli that may generate a graded potential
Graded Potential is....
similar to action potential (electrical impulse) BUT is not as strong
***Acetycholine
stimulates muscle contractions and causes glands to secrete hormones
List two characteristics of neuroglia cells
unable to transmit impulses and never lose the ability to mitotically divide
**STUDY Neuron structure diagram in section B
!!!!!!!
What are the charges on a POLARIZED membrane?
(+) outside, (-) inside [@ rest]
NeuRoNS
(in CNS and PNS)--cells that CONDUCT IMPULSES; exhibit extreme longevity--can live 100 years or more. They are AMITOTIC (can't divide) and have a high metabolic rate--require continuous supply of oxygen and gluscose. Processes extend from the cell body of all neurons--the dendrites and axons. Bundles of processes are tracts in the CNS and nerves in the PNS. --"mature overtime"
What is the function of the Na+/K+ pump?
--Reinstates K+ and Na+ inside/outside cells --restores the initial concentrations of Na and K to rest ??check these
The motor pathway carries information___________ the CNS
AWAY from
Cell Death
About 2/3 of neurons die before birth if they do not form Synapse with target cells; many cells also die due to apoptosis (programmed cell death) during development
Neuron Physiology [5]
Action potential is created--impulse travels through neuron jumping from node to node
Neuron Physiology [4]
Action potential travels down the axon as opened Na+ gates stimulate neighboring Na+ gates to open
The PNS is further divided into.....
Afferent (Sensory) Division and Efferent (Motor) Division
Anchors and braces neurons with cellular projections
Astrocyte cells
Cells serve as a medium for diffusion between capillaries and neurons
Astrocyte cells
Cells only in CNS:
Astrocyte, Microglia, Ependymal, Oligodendrocytes
Neuron Physiology [9]
At axon terminal, impulse causes Ca+ ions to enter cell triggering vesicles to release neurotransmitters
Neuron Physiology [3]
At the axon, stimulus changes permeability of membrane and Na+ diffuse into cell to change polarity--this is DEPOLARIZATION. --for axon to "fire," depolarization must meet threshold causing ACTION POTENTIAL
Long fiber that extends from the soma and conducts impulses away from the soma
Axon
Part of the soma that connects to the axon
Axon Hillock
Where do action potentials usually originate in a neuron?
Axon Hillock
impulses accumulate at the......
Axon Hillock
Axon Terminal
Axon endings that contain neurotransmitter storage vesicles
End branches that contain neurotransmitter storage vesicles
Axon terminal
The ANS is commonly referred to as the involuntary division--why would it be called this?
Bc the fibers involuntarily SEND IMPULSES from the CNS to actions of smoot/cardiac muscles and glands --We cannot control these functions!
Schwann Cells
Cells form the myelin sheaths in PNS
Satellite Cells
Cells protect and cushion neurons in PNS
What is the functions of neurons?
Cells that conduct impulses (CNS and PNS) --"electrical impulses"
Peripheral Nervous System (PNS)
Consists of nerves extending from the brain and spinal cord to the body. Functions=Sensory Input and Motor Output.
Phagocytes that dispose of debris such as dead brain cells and bacteria...
Microglia cells
What is the function of efferent neurons?
Motor Output-->take impulses away from CNS
Neuron Physiology [10]
Neurotransmitters bind to receptors on dendrite of next neuron--process occurs again on next neuron.
Gaps found between the myelin sheaths
Nodes of Ranvier
Myelin
White, fatty material that protects and insulates fibers; speeds up impulse transmission
The Action Potential is an __________. When the stimulus fails to produce depolarization that exceeds threshold, no action potential results. When threshold potential is exceeded, complete depolarization occurs.
all-or-nothing
***Glutamate
an excitatory neurotransmitter which plays a role in memory (excessive amounts of glutamate due to brain damage will kill neurons. ALS results from excessive glutamate production)
***Endorphins
an inhibitory neurotransmitter involved in pain reduction and pleasure
***Dopamine
controls mood, motivation, reward/pleasure drives (cocaine and alcohol increase the levels of dopamine)
What happens to create an action potential?
depolarization of membrane @ Hillock
What is threshold stimulus?
electrical impulse in dendrites and soma
Cells that produce the myelin in the CNS....
oligodendrocytes
Integration
process and interprets sensory input and makes decisions about what to do --"pathway"--->ACTION
Sensory Input
receptors monitor changes occurring inside and outside the body --pain, pressure, sight, smell, etc....Inside brain and spinal cord (CNS)
Sympathetic
regulates actions in STRESSFUL situations (ie. exercising, danger, etc.) "Fight or Flight"
Parasympathetic
regulates actions in nonstressful situations (ie. when body is at rest) "Rest and Digest"
***Norepinephrine
released to stimulate our sympathetic nervous system (exercise increases the release of norepinephrine)
integration.....
CNS
Organization of Nervous System (2 subdivisions)
CNS and PNS
Brain
CNS, Integration
Processing
CNS, Integration
What is the function Ca+ ?
Ca+ causes vesicles to release neurotransmitters
Slender fibers that conduct impulses toward the soma
Dendrite
Neuron Anatomy
Dendrite, Soma, Axon, Axon Hillock, Axon terminal, Myelin, Nodes of Ranvier, Synapse, Synaptic Cleft
Where are the sensory receptors located on a neuron?
Dendrites
Cells have cilia that help circulate the cerebrospinal fluid
Ependymal cells
Cells line cavities of the brain and spinal cord
Ependymal cells
Axon
Fiber extension that generates and conducts impulses AWAY from the Soma. Transmit impulses along AXOLEMMA (cell membrane) to AXON TERMINAL (secretory region). Initial region of axon is called the AXON HILLOCK.
Somatic (SNS)
Fibers send impulses from CNS to control VOLUNTARY action of skeletal muscle
Autonomic (ANS)
Fibers send impulses from CNS to regulate INVOLUNTARY actions of smooth muscle, cardiac muscle, and glands.
Afferent (Sensory) Division
Fibers transmit impulses from the skin, skeletal muscles, joint, and visceral organs to the CNS
Compare the conduction rate of an electrical impulse on an unmyelinated fiber and a myelinated fiber.
Fibers w/ myelin will have faster electrical impulses
Nodes of Ranvier
Gaps between myelin sheaths
What's the difference between graded potential and action potential?
Graded potential-->electrical impulse @ dendrite & soma; Action Potential--> stronger electrical impulse @ axon
What is the functions of the brain?
INTEGRATION (double check answer?)
Neuron Physiology [6]
In response to the inflow of Na+, K+ channels open. K+ diffuses out of the cell to restore the electrical conditions--this is called REPOLARIZATION. --->soon after the K= gates open, the Na+ gates close. Repolarization must occur to conduct another impulse.
What are the functions of neuroglia cells?
Insulate, support, protect
What is the function of interneurons?
Integration
Synapse
Junction of two neurons; space at Synapse is called Synaptic Cleft --Neurons don't touch each other!
What causes REPOLARIZATION?
K+ rushes out of cell
What is the function of Motor Neurons?
MOTOR OUTPUT: activates muscles or glands
Fatty material that protects fibers and speeds up impulse transmission
Myelin
Neuron Physiology [7]
Na/K pump restores the initial concentrations of Na and K to resting conditions--refractory period.
Sam was diagnosed with a brain tumor. Which type of cells would be dividing uncontrollably by mitosis to form the tumor--neurons or neuroglia?
Neuroglia
NeRvoUs TisSuE--
Neuroglia and neurons
Motor Output, Sensory Input.....
PNS
The __________ is made up of the the nerves that lead to and from the brains and spinal cord
PNS
Getting "chill bumps"
PNS, Motor Output
Glands secrete substances
PNS, Motor Output
Picking up an object
PNS, Motor Output
Sweating
PNS, Motor Output
Hearing a noise
PNS, Sensory Input
Tasting something
PNS, Sensory Input
The _____________ division of the nervous system regulates your body's activities under "normal"/stable conditions (ie. times when your emotional state is regular)
Parasympathetic
Microglia Cells
Phagocyte cells in the CNS that DISPOSE OF DEBRIS including dead brain cells and bacteria; needed bc the immune system is denied access to CNS "Acts as WBC"
Neuron Physiology [1]
Plasma membrane of a resting (inactive) neuron is POLARIZED, which means the outside of cell is more positive than the inside. --All gated Na+ and K+ channels are CLOSED>>this maintains the resting membrane potential
Motor Output
Response activates muscles or glands (effectors)
What is the function of sensory neurons?
SENSORY INPUT: recept changes in/out of body and sends info (CNS)
Cells help cushion and protect neurons in the PNS
Satellite cells
Cells that produce the myelin in the PNS...
Schwann Cells
Cells only in PNS:
Schwann and Satellite
Functions of Nervous system (3)
Sensory Input, Integration, and Motor Output
What is the function of afferent neurons?
Sensory input
Explain how an impulse is transmitted through a neuron starting at the sensory receptors....
Sensory receptor-->sensory neuron-->interneuron-->motor neuron-->effector organ
Describe the path of a stimulus from sensory receptor to motor neuron:
Sensory receptors are stimulated-->impulses travel down dendrite to Soma-->impulses travel to axon-->axon terminal-->neurotransmitters are released.
more UNDERSTANDING of Neuron anatomy (explanation)
Sensory receptors on dendrites receive impulse. Impulse is sent to cell body. then through the axon jumping from node to node. When impulse reaches terminals, a neurotransmitter is released and binds to receptors on the dendrites of another neuron.
Contains the nucleus and is the metabolic center of the cell
Soma
Which motor division conducts information from the CNS to the skeletal muscle?
Somatic (SNS)
Efferent (Motor) Division is divided into two parts.....
Somatic (SNS) and Autonomic (ANS)
The CNS is composed of the....
Spinal Cord and Brain
What causes DEPOLARIZATION?
Stimuli cause Na+ channels to open and Na+ rushes in
The ____________ division of the nervous system mobilizes the body in emergency situations making someone more alert. It causes a person to get the adrenaline rush in times of anxiety, anger, excitement resulting in an increased respiration rate, increased perspiration, etc...
Sympathetic
ANS (part of Efferent/Motor Division) is further divided into.....
Sympathetic and Parasympathetic
Junction of two neurons
Synapse
Space between the axon terminal of one neuron and the dendrites of another
Synaptic cleft
The sensory pathway carries information___________ the CNS
TO
more UNDERSTANDING of Neuron anatomy (explanation) cont.
The AFFERENT NEURONS sensory receptors change stimuli from external sources into electrical impulses and send the electrical stimulus to interneurons in the spinal cord. INTERNEURONS form ascending tracts that transmit sensory impulse to the brain for integration. Impulses are transmitted from the brain by Interneurons that form descending tracts in the spinal cord. Interneurons stimulate EFFERENT NEURONS which conduct impulses from the spinal cord to effector organs.
nervous system
The master controlling and communicating system of the body--cells communicate via electrical and chemical signals. Signals are rapid, specific, and cause almost immediate responses.
Neuron Physiology [8]
These events continue to spread across the membrane of the neuron until the impulse reaches the axon terminal.
Multiple Sclerosis (MS)
autoimmune disease in which immune system attacks myelin--sheaths in CNS are destroyed and myelin turns to hardened lesions called scleroses. Impulse conduction is slow and eventually ceases.
Efferent (Motor) Division
carries impulses from the CNS to effector organs, the muscles and glands [causes an ACTION]
Ependymal Cells
cells LINE CAVITIES (ventricals in brain) of the CNS; the beating of cilia helps circulate cerebrospinal fluid.
Astrocyte cells
cells in the CNS that contain projections that cling to neurons BRACING them and ANCHORING them to CAPILLARIES; serves as a barrier and MEDIUM FOR DIFFUSION between capillaries and neurons. MOST ABUNDANT, versatile, and highly branched glial cells--controls chemical environment around neuron. "filter"
Oligodendrocytes
cells wrap their extensions tightly around nerve fibers in the CNS producing fatty insulating coverings called myelin sheaths
Neurotransmitters are.....
chemicals which carry the impulse across the synaptic cleft from one neuron to the next neuron
Central Nervous System (CNS)
consists of the brain and spinal cord. Function=Integration
Dendrite
fiber extensions containing SENSORY RECEPTORS that conduct IMPULSE TOWARD SOMA
***GABA (gamma-aminobutyric acid)
inhibitory; causes cells to be less excitable
***Serotonin
inhibitory; controls our emotional well-being/mood and helps to regulate sleep (low levels lead to depression)
Neuroglia cells
insulate, support, and protect; cells and unable to transmit impulses and never lose the ability to mitotically divide.
