4th exam-Nervous and Endocrine system Flashcards
nervous system functions to
- communicate with and regulate other body systems
- maintain homeostasis
- works in conjunction with endocrine system
rapid, brief responses (action potentials and neurotransmitters)
Nervous system
slow, prolonged response (hormones)
Endocrine system
functions of the nervous system
perception memory emotion voluntary movements behavior
three basic components of nervous system function
sensory function
integrative function
motor function
sensory function
- detect internal and external stimuli
- sensory information carried to spinal cord and brain via sensory neurons
integrative function
- process sensory info (analysis, integration, and storage [memory])
- association neurons (inter-neurons)
motor function
- respond appropriately to sensory info
- response info carried to effectors (muscles and glands) via motor neurons
nervous system structures
brain cranial nerves 12 spinal cord spinal nerves 31 ganglia enteric plexuses sensory receptors
the two divisions of the nervous system
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
components of central nervous system - cns
brain
spinal cord
components of peripheral nervous system - pns
cranial nerves (& their branches)
spinal nerves (& their branches)
ganglia
sensory receptors
the 3 subdivisions of the Peripheral nervous system PNS
-somatic nervous system SNS
-Autonomic nervous system ANS
-Enteric nervous system ENS
….each has a sensory and motor component
Somatic nervous system SNS
- sensory neurons from “organs, body wall, limbs, etc
- motor neurons leading to skeletal muscle (voluntary control)
- soma = body
Autonomic nervous system ANS
- sensory neurons from “visceral organs”
- motor neurons leading to smooth muscle and cardiac muscle and glands (involuntary control)
- auto = self; nomic = law
Enteric nervous system ENS
- enteric plexuses of gastrointestinal tract (involuntary)
- sensory neurons from GI tract
- motor neurons leading to smooth muscle and glands of GI tract
- enter = intestines
Nervous tissue consist of
- neurons, that “generate action potentials”, “electrically excitable”
- neuroglia, support, nourish, and protect neurons
neurons and excitable cells respond to stimuli by
generating a nerve impulse (action potential)
an electrical signal that propagates (travels) along neuron in one direction (dentrite –> axon)
action potential
typical neuron consists of these 4 parts
- cell body
- dendrites
- axon
- telodendria
cell body includes
- nucleus
- cytoplasm
- typical organelles
Dendrites have
- multiple nerve fibers (often short and branched)
- input portion of the neuron (receives signals from environment or from another cell)
Axons include
- single nerve fiber
- output portion of the neuron (delivers signal to other cell)
- often long and branched only at end “telodendria”
Telodendria
- end in synaptic terminals
- neurotransmitters stored in synaptic vesicles within synaptic terminals
consists of: one axon
& several dendrites
multi-polar neurons
consists of : one axon and one main dendrite
bi-polar neuron
consists of: -sensory neruons,
-axon and dendrite fuse before meeting cell body
uni-polar neruon
consists of: -more than 2 process
-axons cannot be distinguished from dendrites
anaxonic neuron
relay sensory information from sensory recepters or sensory cells to CNS
sensory (afferent) neurons
relay motor information from CNS to effectors (muscles or glands)
Motor (efferent) neurons
- link sensory and motor neurons witin the CNS
- integrate (process) incoming sensory information and elicit appropriate motor response
interneurons (assonciation neurons)
-support, nourish and protect neurons
neuroglia
CNS includes ____ diff types of neuroglial cells
4 types
- astrocyte
- oligodendrocytes
- microglia
- ependymal cell
- support neurons
- maintain blood-brain barrier
- maintain appropriate chemical environment around neurons
Astrocyte
produces and maintains myelin sheath around CNS axons
oligodendrocytes
phagocytize microbes and damaged nervous tissue
microglia
- lines ventricles of the brain and spinal cord
- produce cerebrospinal fluid
ependymal cell
PNS includes ___ diff types of neuroglial cells
2 types
- satellite cells
- schwann cells
surround cell bodies of neurons in PNS ganglia
-support and exchange of materials
satellite cells
encircle axons of neurons in PNS producing a myelin sheath
Schwann cell
- axons of some neurons are myelinated
- covered by a myelin sheath
myelination
- composed of lipids and proteins
- electrically insulates the axon (prevents generation of action potentioal)
myelin sheath
myelination of PNS axons
- myelin sheath produced and maintained by Schwann cell
1. as it develops, schwann cells wrap around axon
2. portion of plasma membrane of schwann cell that wraps around the axon is the myelin sheath
Gaps in the myelin sheath are called
Nodes of Ranvier
the two types of tissue in the CNS
- white matter
- grey matter
composed of mainly myelinated axons
white matter
composed mainly of neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia
Grey matter
axons of neurons are often bundled together forming
- nerves
- tracts
bundles of axons located in the PNS
nerves
bundles of axons located in the CNS
tracts
resting membrane potentials exist because
there is a high concentration of Na+ outside of a cell
- Na+/K+ pumps in plasma membrane actively transport out of cell
- there are few Na+ leakage channels in plasma membrane
production of electrical signals depend on
- existence of a resting membrane potential
- presence of specific ion channel
electrical signals are due to
flow of ions across the plasma membrane via ion channels
___ allow specific ions to cross the plasma membrane
ions channels
movement of ions creates flow of
electrical current that changes resting membrane potential
leakage channels
- randomly open and close
- more K+ leakage channels than Na+ channels
- plasma membrane is more permeable to K+ than Na+
open in response to specific chemical stimulus including: vibration, pressure, tissue stretching
-found in sensory receptors
mechanically gated channels
- open in response to change in membrane potential (voltage)
- participate in generation and propagation of action potentials
voltage gated channels
neurons produce what two types of electrical signals
- grated potentials
- action potentials
- graded potential triggered 1st may be followed by action potential
- small deviation from the resting potential due to movement of ions
- vary in amplitude depending on strength of stimuli
- are local, mainly dendrites and cell body of neuron
Graded potentials
a series or rapid events that take place in two phases
action potential
what are the 2 action potential phases
- depolarization phase
- repolarization phase
action potential triggered when
depolarization reaches a certain threshold (*-55mV) due to a depolarizing graded potential
-amplitude of action potential is always the same
generation of action potentials defined by what 5 steps
- depolarization to threshold
- activation of sodium channels and rapid depolarization
- inactivation of sodium channels and activation of potassium channesl
- closing of potassium channels
- after hyperpolarizing phase
Summary of repolarizing phase
Inside of cell becomes negatively charged again (repolarized) (-70mV)
Fast-acting Na+ channels become inactivated
Slow-activating K+ channels open
Summary of depolarizing phase
Inside of cell becomes positively (+30 mV)
Fast-acting Na+ channels open
Period during which excitable cell cannot generate another action potential
Refractory period
Type of refractory period where:
Na+ channels require time to return to resting state before they can open again
No amount of stimulus can generate a second action potential
Ensures that action potential moves in a single direction
Absolute refractory period
Type of refractory period where:
K+ channels are open
Second action potential can be generated if stimulus is larger than normal
Relative refractory period
When and where is the action potential generated?
at a specific point on the plasma membrane, not across entire plasma membrane at once
Movement of cation potential long neuron:
- From trigger zone
- Typically at junction of cell body and axon
- To axon terminals
Propagation
Type of propagation that has step-by-step polarization and repolarization of each region of the axon:
- Action potential at one point stimulates generation of action potential at next point
- Slow rate of propagation
- Occurs in unmyelinated axons
Continuous propagation
Type of propagation in which:
Few Na+ and K+ channels under the myelin sheath
Action potential cannot be generated there
Action potentials “jump” from one node of Ranvier to the next
Much more rapid propagation than continuous conduction
Saltatory propagation
A neuron that sends signal (synapses)
Pre synaptic neuron
A neuron that receives signal
Post synaptic neuron
Two types of synapses
Electrical synapse
Chemical synapse
Type of synapse where action potential conducted directly from cell to cell via gap junctions and allows for faster communication and greater synchronization among cells
Electrical synapse
Type of synapse where:
- Pre- and post- synaptic cells are separated by a synaptic cleft (Filled with interstitial fluid)
- Action potential conducted across synaptic M indirectly via neurotransmitters
Chemical synapse