Neurophys Flashcards
Is endocrine fast or slow control?
slow control
Is the nervous system fast or slow control?
fast control
2 major divisions f the nervous system?
Central and peripheral
Central nervous system
brain and spinal cord
Peripheral nervous system
nerves that connect the brain or spinal cord with the body’s muscles, glands, and sense organs.
Basic cell type of the nervous system
neuron
neurons are amitotic meaning…
they do not divide
Neurons have a very high what?
metabolic rate. they need a lot of glucose and have a lot of mitochondria
most numerous cells in the CNS
Glial (non-neuronal support)
Astrocytes
SOO diverse! Work in healing; regulate ion concentrations, synapse formations and more; Create a supportive framework for neurons.
Oligodendrocytes
form and maintain myelin in the CNS.
Microglia
CNS macrophages. Important immune system workers of the CNS.
Ependymal Cells
Create CSF in the CNS.
Schwann Cells
Create myelin in the PNS.
Afferent neurons
move from the muscle to the CNS
-affected by a stimulus
see slide 13
Efferent neurons
move from the CNS to the muscle
-cause an effect
see slide 13
Interneurons
- Lie entirely within the CNS
- account for > 99 percent of all neurons
If axons are severed, they can repair themselves and restore significant function only if….
the damage occurs outside the CNS and does not affect the neurons cells body
why is peripheral nerve injury healing so slow?
axon regrowth proceeds at a rate of only 1 mm per day
what happens to the axon segment that is separated from injury?
the cell body degenerates. The part of the axon still attached to the cell body then develops a new growth cone, which grows out toward the effector organ. Sometimes function is restored.
apoptosis=
cell death
what you need to know about generation and conduction of a nerve impulse:
- Resting Membrane Potential, generated by Active Transport
- Voltage Gated Na+ and K+ Channels
- Depolarization, repolarization, hyperpolarization
- Graded Potential
- Threshold Potential
- ALL-OR-NONE FIRING
- Action Potential
- Unidirectional signal conduction
- Delayed opening of K+ channels relative to Na+ channels
The resting membrane potential
difference in charge
- more positive outside
- more negative inside
what is the sodium potassium pump reliant on
ATP function
Depolarization
the potential moving from RMP to less negative values.
Repolarization
is the potential moving back to the RMP.
Hyperpolarization
the potential moving away from the RMP in a more negative direction.
Graded potentials
- little changes in membrane potential that are confined to a relatively small region of the plasma membrane.
- By definition, they can be of various sizes, but don’t reach threshold potential by themselves.
Two types of graded potentials
EPSP’s (excitatory)
IPSP’s (inhibitory)
7 steps of the nerve firing
1.RMP
2.threshold reached.
3.Na+ channels open in response to the depolarization beside them.
4.Na+ channels are inactivated while the slower K+ channels open to repolarize the cell.
Since the sodium channels are inactive, the signal can’t go backward here.
5.K+ channels cause enough + ions to leave the cell’s interior that the membrane repolarizes, and in fact…
6.Hyperpolarizes the cell, making it even harder for a signal to transmit backward.
7.K+ channels finally close and Na+ channels are reactivated, but by this time the signal is long gone.
action potential inhibition
Lidocaine, Procaine, Marcaine– block voltage-gated Na+ channels.
Absolute refractory period
another action potential cannot be sent at this time (step 5 of nerve firing)
relative refractory period
another can be sent only if it is big enough to overcome this hyperpolarization PLUS the normal amount of depolarization (step 6 of nerve firing)
what is Myelin?
an insulator that makes it more difficult for charge to flow between intracellular and extracellular fluid compartments.
-adds speed, reduces metabolic cost, and saves room in the nervous system because the axons can be thinner
What are the node of Ranvier?
Action potentials occur only there
-where the myelin coating is interrupted and the concentration of voltage-gated Na+ channels is high.
how do synapses pass information?
chemically or electronically
-they use neurotransmitters
are synapses inhibitory or excitatory?
inhibitory or excitatory depending on the signal/ neurotransmitter being transmitted
When the synapses signal is Electrical
Pre- and post-synaptic cells are connected by gap junctions
When the synapses signal is Chemical
- Pre-synaptic neurons release neurotransmitter from their axon terminals
- Neurotransmitter binds to receptors on post-synaptic neurons
neurotransmitter is released via what?
exocytosis
autoreceptors are
a built-in brake for the system
To terminate the signal in a chemical synapse, the neurotransmitter must be removed. This is accomplished by:
- Diffusion of the transmitter from the cleft
- Degradation of the transmitter by enzymes
- Reuptake into the pre-synaptic cells for reuse
- Removal of the receptors in the post-synaptic cell’s membrane.
ACETYLCHOLINE (Ach):
- This one is made by attaching acetyl CoA to choline.
- It’s ALWAYS the first signaler on efferent pathways to the peripheral nervous system.
- After being sent into the synapse, it gets broken back into AcCoA and Choline by acetylcholinesterase (AChE). The pieces then get recycled.
CATECHOLAMINES:
Dopamine, Epinephrine, Norepinephrine
(DA, Epi, NE):
- Made from the amino acid tyrosine
- NE and Epi are important in the Sympathetic Nervous System (more on that later)
- Once released into the synapse, they’re either taken back up into the pre-synaptic neuron or destroyed by monoamine oxidase (MAO).
Serotonin
a complicated one!
- Made from an essential amino acid, Tryptophan.
- Works slower than some neurotransmitters– more of a “modulator” than a true transmitter.
- Almost always there’s another transmitter being released along with it.
- It’s excitatory in muscle pathways, inhibitory in sensory pathways.
Endogenous Opioids:
- Short polypeptides (~15-25 aa’s long)
- Unlike other transmitters, these are made in the cell body, put into vesicles, and transported all the way down the axon for release.
- Eventually broken down by peptidases– but they can last a while.
- Runner’s high, firewalking and the like have been attributed to Endogenous opoids.
- Also have an effect on appetite, mood, emotion.
Many drugs act by interfering with or stimulating processes in the neuron, some of the processes include…
neurotransmitter synthesis, storage, and release, and in receptor activation.
Clostridium tetani (tetanus toxin)
- prevents vesicle fusion with the membrane, inhibiting release of GABA– a neurotransmitter that would normally inhibit muscle contraction.
- What is the result?
- increased and tetanic muscle contraction.
Clostridium botulinum bacilli toxin (botulism):
- interferes with actions of SNARE proteins at excitatory synapses that activate muscles.
- What is the result?
- Absence of muscle contraction (muscle paralysis).
What is Botox used for?
Low doses are injected therapeutically to treat facial wrinkles, severe sweating, hyper-contracted neck muscles, migraines, uncontrollable blinking, misalignment of the eyes, and others.
Efferents in the PNS are divided into what?
sympathetic and parasympathetic
Brain is subdivided into what 3 divisions?
Forebrain
Midbrain
Hindbrain
Forebrain consists of what?
CEREBRUM AND DIENCEPHALON (thalamus, hypothalamus, epithalamus)
Cerebrum =
right and left hemispheres + other structures on the underside of the brain.
The central core of the forebrain is formed by what, which helps connect the 2 hemispheres?
diencephalon
what does each hemisphere contain?
cerebral cortex (outer shell of gray matter composed mostly of cell bodies that give the area a gray appearance) + inner layer of white matter (composed primarily of myelinated fiber tracts)
Beneath the white matter: there is another layer of gray matter cell clusters called… (and what do they do?)
the subcortical nuclei– interneurons that:
- bring information into the cerebrum - carry information out - connect different areas within a hemisphere
what makes up white matter?
myelin
what makes up gray matter?
neurons
The cortex is 3 mm in thickness but is highly folded. WHY?
Folds create an area that is four times larger than if the brain surface were flat, without appreciably increasing the volume of the brain.
The cortex of each cerebral hemisphere is divided into four lobes:
- frontal
- parietal
- Occipital
- Temporal
The cortex layers of the left and right cerebral hemispheres are connected by the ______
corpus callosum– a massive bundle of nerve fibers.
Frontal Lobe:
REASONING, PLANNING, parts of speech, MOVEMENT, emotions, and problem solving
Parietal Lobe:
MOVEMENT, PERCEPTION OF STIMULI, orientation, recognition
Occipital Lobe:
VISSUAL PROCESSING
Temporal Lobe:
PERCEPTION AND RECOGNITION OF AUDITORY STIMULI, MEMORY, and speech
The brain’s neurons are________
upper motor neurons– they direct voluntary movements and integrate signals to create many involuntary muscle activities.
The neuron that actually goes to a muscle is usually a
lower motor neuron– with its cell body in the spinal cord and its axon in the periphery.
What do many interneurons affect?
the stimulus that a muscle will recieve
FUNCTION OF CEREBRAL CORTEX:
INTEGRATION
- Collects afferent info
- Processes it
- effects motor and endocrine systems based on that info
Subcortical Nuclei–
areas of gray matter that lie deep within the cerebral hemispheres. Still forebrain; just deep in the forebrain.
Basal Ganglia
part of the cerebral cortex
- plays an important role in controlling movement, posture and the complex aspects of behavior
Diencephalon:
-MIDDLE OF THE BRAIN AT THE BOTTOM
-CONTAINS THE THALAMUS, HYPOTHALAMUS, AND EPITHALAMUS
(not being quizzed on)
Thalamus:
-KEY ROLES: AROUSAL AND FOCUSING ATTENTION
not being quizzed on
Hypothalamus:
- lies below the thalamus and on the undersurface of the brain
- the master command center for neural- endocrine coordination.
- Effects behaviors dealing with preservation of the individual (e.g.eating and drinking) and preservation of the species (reproduction)
- lies directly above the pituitary gland (more on this in endocrine) and regulates it.
what does the cerebellum do?
Coordinates movements and controls posture and balance through feedback loops
- Receives info from muscles, joints, skin, eyes, ears, viscera, and the parts of the brain that control movement
- also involved in people who learn by doing.
The central butterfly-shaped area of gray matter in the spinal cord =
- interneurons,
- the cell bodies of efferent neurons,
- the entering axons of afferent neurons
- glial cells.
what is the surrounding white matter of the spinal cord?
groups of myelinated axons
Afferent fibers from peripheral nerves enter the spinal cord on the dorsal side via the ______
dorsal roots
Small bumps on the dorsal roots, __________, contain the cell bodies of these afferent neurons.
the dorsal root ganglia
The axons of efferent neurons leave the spinal cord via the
ventral roots
A short distance from the cord, the dorsal and ventral roots from the same level combine to form a _______, one on each side of the spinal cord.
spinal nerve
how many pairs of nerves for the PNS
43
how many pairs of cranial nerves are in the PNS
12
how many pairs of spinal nerves are in the PNS?
31
Function of the PNS
Neurons in the PNS transmit signals between the CNS and receptors/ effectors in all other parts of the body.
Spinal nerves are names by the vertebral levels from which they exit, what are those levels and how many exit each?
Cervical (8) Thoracic (12) Lumbar (5) Sacral (5) Coccygeal (1)
cervical nerves =
muscles, glands and sensory from/for the neck, shoulders, arms, and hands.
thoracic nerves =
chest and upper abdomen.
lumbar nerves =
the lower abdomen, hips, and legs.
sacral + coccygeal nerves =
genitals and lower digestive tract.
All the spinal nerves contain both _____ and ______fibers, whereas some of the cranial nerves contain only _______ fibers or only _________ fibers.
afferent and efferent
Somatic
skeletal muscle, excitation only
autonomic
- automatic
- sympathetic or parasympathetic
- sympathetic innervates smooth and cardiac muscle, glands, and GI neurons
- parasympathetic can be excitatory or inhibitory
Sympathetic uses ___ at central synapse and __ and ___ at the distal synapse.
ACh
NE
Epi
Sympathetic =
fight or flight
Parasympathetic uses ___ throughout– no ___ or ___
_
ACh
NE or Epi
Parasympathetic =
rest and digest
One set of neurons in the sympathetic division never develops axons. Instead, they form the _____ _______
adrenal medulla
When stimulated by the SNS, cells of the adrenal medulla release a mixture of about __% epinephrine and ___% NE into the bloodstream.
80%, 20%
Because this mixture is released into the bloodstream, it’s ______ system rather than ________system.
endocrine, nervous
-This is often referred to as neuroendocrine regulation
All efferent messages coming form the CNS use __________ as their first neurotransmitter– always.
acetylcholine (ACh)
___ always acts on skeletal muscles in the somatic NS
ACh
___ always acts as the second neurotransmitter in the PNS
ACh
__ or ___ is the 2nd transmitter in the SNS
NE or Epi
Meninges are the ____
membranes that line the structures and add additional support and protection.
- Dura mater
- Arachnoid mater
- Pia mater
protects and cushions the structures of the CNS
CSF
There are three layers of the meninges–
dura mater, arachnoid mater, and pia mater
The job of the meninges is to:
- cover/protect the CNS
- protect blood vessels and enclose the venous sinuses
- contain CSF
- form partitions in the skull
CSF
- extracelluar fluid of CNS
- secreted by ependymal cells of the choroid plexus
Meningitis
- inflammation of the meninges
- It’s a serious threat to the brain since bacterial or viral meningitis can spread throughout the CNS.
- Inflammation of the brain = encephalitis
The sub-arachnoid space is _____
filled with CSF and contains the largest blood vessels serving the brain.
arachnoid villi
absorb the CSF back into the venous blood system.
The pia mater
clings to the brain and contains a network of blood vessels.
