What are the general functions of the nervous system?
Control of body functions and regulation of homeostasis.
Which chemical is used by both the nervous and endocrine systems?
Epinephrine
Where are the sensory receptors located and what are they?
Skin: Meissner's corpuscle for touch and Pacinian corpuscle for pressure
What are the effectors of the SNS and what kind of control do we have over them?
Effectors: skeletal muscles
Voluntary control
What is in the ANS?
- Sympathetic (fight or flight)
- Parasympathetic (feed and relax)
What are the effectors of the ANS and what kind of control do we have over them?
Effectors: Smooth & cardiac muscle
Involuntary control
What is the sensory (afferent) function?
- detects change
- sensed by the special and general senses
- sensory neurons send signals to CNS
What does the integrative function do?
It analyzes the sensory input and stores info. (memory) for future if it happens again; decides the response.
What is the motor (efferent) function, what are the effectors?
It is the "motor output", responds to change. Muscles and glands are effectors; motor neurons send info. to the effectors. Think "exits the brain/spinal cord".
Do neurons undergo mitosis?
No, they stay in the G0 phase.
Label the parts.
___ is the cytoskeleton of the neuron.
Neurofibrils
Neurotransmitters are made in the ___.
nissl bodies
What are myelin sheaths made of and what do they do?
They provide insulation which increases the speed of electrical conduction. They are made of lipids and proteins.
What do axons do?
They direct signals from the cell body towards the next neuron or the effector.
Myelin sheath gap is also called ___.
nodes of ranvier
Describe the direction of nerve impulse conduction.
Dendrites > Cell body > Axon > Axon terminal > Synaptic end bulbs
Describe multipolar neurons.
Many dendrites, one axon, is the most numerous and part of the CNS.
Describe bipolar neurons.
Found in the special senses, one axon and dendrite.
Describe unipolar neurons.
Axon and dendrites at opposite ends; found in the receptors of touch.
What kind of neuron is this and where can it be found?
Unipolar; receptors of touch.
What kind of neuron is this and where can it be found?
Bipolar; in the special senses.
What kind of neuron is this and where can it be found?
Multipolar; CNS, mostly the brain.
Regardless of structural type, the direction of nerve impulse conduction is always the same. True or false.
True
Describe the diagram.
Stimuli is picked up by sensory receptor in PNS > impulse travels through the sensory neuron > exits the neuron through the synapse > enters multipolar neuron (CNS) > analyzed by interneuron and is given instrunctions >exits the first multipolar to go the next > stimuli enters PNS again and it travels through a motor neuron > goes to the effectors
What do neuroglia do?
Supports neurons by protecting and nourishing them (nerve glue).
Of these two which undergo mitosis: neuron, neuroglia
- neuroglia
What do astrocytes do?
They form a blood brain barrier to protect neurons.
What do oligodendrocytes do?
Produce a layer of myelin sheath around axons and several neurons in CNS.
What is the function of ependymal cells?
They secrete cerebrospinal fluid (CSF)
What do the schwann cells do?
- wraps several layers of myelin sheath around a single axon in PNS
- creates myelin sheaths, thus electrically insulating axon
What is myelin made of and cells make them?
Oligodendrocytes in the CNS or schwann cells (PNS); composed of lipids and proteins.
What does the myelin sheath do?
Electrically insulate the axon; increases the speed of conduction.
In the PNS, some neuron regeneration is possible. How?
This only occurs if the neurolemma is intact.
What is inside white matter and what gives it its colour?
Mainly myelinated axons of many neurons; the fat of the myelin give it its white colour.
What is gray matter made of?
Neuron cell bodies, unmyelinated axons, dendrites and more.
What is the collection of neuron cell bodies in the CNS and the PNS called?
CNS - nucleus
PNS - ganglion
How do excitable cells communicate with one another?
Graded potential (GP) - communication over local, short distances in neurons only
Action potentials (AP) - long or short distances in neurons and motor cells
What is the intracellular voltage/RMP of the cell?
-70mV
What hormone allows ligand-gated channels to open?
Acetylcholine
Polarity is the result of ___.
a difference in the electrical charge across the membrane (3Na+ out for every 2K+ coming in).
What causes an action potential?
When stimuli reaches the threshold level (-55mV).
Depolarization promotes AP production. True or false.
True; depolarization increases the positive ions in the membrane, thus making the potential less negative. Channels open up along the axon (as a result of a stimulus) for positive ions to enter the membrane.
In a GP, what causes it to trigger an AP?
When they add together to become larger.
What is the all or one principle?
AP can only occur if the mp reaches the threshold (-55).
What happens when the mp reaches +30?
K+ starts leaving the membrane, repolarization occurs.
Describe the RMP.
High intracellular Na; high intracellular K.
AP travelling from the trigger zone to the axon terminals is called ___.
propagation
AP dies out. True or false.
False; they keep their strength as they spread across the membrane.
What is depolarization?
When NA+ channels open, and make the RMP more positive. The first step in creating an AP and reaching the threshold.
Slow/continunous conduction occurs in what type of axons?
Unmyelinated
Saltatory conductions occus in what type of axons? It jumps from myelin to myelin, separated by a node of ranvier.
Myelinated
If excitatory, ___ is produced. If inhibatory ___.
AP, no action AP