Week 2 Flashcards
Midbrain consists of:
Ventricle: cerebral aqueduct
Subdivision: Mesencephalon
Principle Structures: Tectum and Tegmentum
“phalon”s
Midbrain function
Mesencephalon
Important functions in motor movement, serves as pathway between spinal chord, cerebellum, and forebrain
part of the brainstem
Tectum
Part of the mesencephalon/midbrain.
Tectum= roof
Principle structures:
- Superior colliculi: visual reflects/object tracking (orienting)
- Inferior colliculi: auditory system in the ear
Tegmentum
Covering
Wraps around the cerebral aqueduct (connects the third and the fourth ventricle)
Includes:
PAG (periaqueductal gray matter)
Raphe (red) nucleus
Substantia Nigra (black)
PAG (periaqueductal gray matter)
Pain modulation, opens and closes pain response (this is where endo and exo opioids act)
Raphe (red) nucleus
Coordination of sensorimotor information
synthesizes serotonin (helps put pieces togeether)
SSRIS have large impact here
Substania Nigra (black)
Key role in dopamine production (works with BG)
Cerebral peduncles
attach cerebrum to brainstem
Corticospinal tract
shows how motor information passes up and down the body. “I want to kick that soccer ball”
Have sensory and motor component.
If you are kicking with your right foot, its done on our left side of the brain. For motor, decasation (crossing over) happens at midbrain. After level of decasation, what happens on the bottom is processed on the opposite side
Hindbrain consists of
Ventricle: fourth
Subdivision: metencephalon and myelencephalon
Principle structures: cerebellum, pons, medula oblongata
Metecencephalon (“afterbrain”) consists of
- pon
- cerebellum
Myelencephalon consists of
Medulla oblongata
Cerebellum
Part of metencephalon, called “little brain”
Attached to pons by cerebellar peduncles
Posture, balance, fine motor movement (ataxia),
motor learning (works w/BG), proprioception (knowing where your body is in space)
Pons
Part of metencephalon, called “bridge”
Translates signals b/t the cerebellum and cerebrum
(e.g., sensory cues, motor information)
Regulates breathing and arousal
Damage (stroke, trauma, late-stage ALS) = locked-in
syndrome (complete paralysis but can blink)
Medulla oblongata
Part of the Myelencephalon
Controls basic function of the autonomic nervous system like:
- breathing
- cardiac function
- vasodilation
- reflexes (vomiting, coughing, sneezing, swallowing)
Damage or enlargement = respiratory failure, paralysis, loss of sensation.
Salamander: took out everything except medulla oblongata, survived
Reticular formation
Security guard of your brain
Complex network of neurons located in the brain stem
Connects thalamus and hypothalamus
Supports feeling alert, and filter incoming information
–> if you hear continuous beeping, you start to filter out so you can engage in your enviornment
Spinal Cord
Connected to brain through brain stem
Long bundle of nerve tissue
sends motor commands from the brain to the body, sends sensory information from the body to the brain, and coordinate reflexes
Three sections:
- cervical spinal chord: sends nerves to face and neck
- thoracic spinal chord: sends nerves to arms, chest, abdomen
- lumbar-sacral spinal chord: sends nerves to lower body
At the bottom: cauda equina (bunch of nerves)
Spinal nerves
Relay sensory information to the brain from the body and vice versa (also control reflexes)
Spinal cord injury
Can be complete (total severance) or incomplete.
Types of neurons in your Somatic Nervous System (NS)
Sensory neurons: carry signal from outer parts (periphery) into CNS
Motor neurons: carry signals from teh CNS to the out parts (muscle, skin, glands) of your body
Interneurons: connect various neurons within the brain and spinal cord
Somatic NS made up of
Spinal Nerves: They are
mixed nerves that carry
sensory information into and
motor commands out of the
spinal cord.
Cranial Nerves: They are the
nerve fibers that carry
information into and out of the
brain stem.
CNS vs PNS
CNS: Brain, spinal cord. Contains interneurons (relay neurons)
PNS: composed of cranial, spinal, and peripheral nerves. Contains sensory neurons and motor neurons
Spinal Nerves
Nerves that leave the vetebral column and travel to the muscles or sensory receptors they inntervate (or supply)
Afferent axons bring information toward the CNS
Efferent axons sending information outward (think E for exit)
Reflex Arc
Touch hot pan. your sensory neurons bring information to your spinal and reflex arc. Tells motor neuron to drop pan
Doesn’t go to brain, takes too long
Dermatome vs myotome
Dermatome: areas of skin on your body that rely on specific nerve connections on your spine.
- check with light prick
Myotome: A group of muscles innervated by a single spinal nerve
- check with sharper obect
Check to see if there is an issue
ASIA Impairment Scale
Spinal Chord can be motor and sensory loss
Nothing you can do with A
With below, you can try to move one (from C to D)
Cranial nerves
12 pairs
most serve sensory and motor functions of teh head and neck region
Includes vagus nerve
Vagus nerve
Regulates the function of organs in the thoracic and abdominal cavities
Longest cranial nerve
Helps body exit fight or flight (helps autonomic, even though in somatic)
Autonomic NS
Consists of two anatomically separate systems:
Sympathetic division (fight, flight, freeze, fawn)
Paraympathetic division (rest and digset)
Sympathetic NS
Part of autonomic NS
fight, flight, freeze, fawn
–Controls functions that accompany arousal and expenditure of energy
–Coordinates responses to a stressor
–Aka Thoracolumbar System
Parasympathetic division
Part of autonomic NS
Rest and digest
Involved with increases in body’s supply of stored energy
Coordinates rest and relax responses after the body has been stressed
Aka Craniosacral System
Vagus Nerve responsible for the calming following a stressful situation
Para vs sympt. nervous system
Nervous system overview
Two basic divisions:
– Central nervous system (CNS) (Brain and spinal cord)
– Peripheral nervous system (PNS) (Outside the brain and spinal cord)
CNS communicates to rest of body via nerves
Three types of neurons
▪ Sensory neurons
▪ Motor neurons
▪ Interneurons
*These neurons perform functions essential to tasks such as perceiving, learning, remembering, deciding, and controlling complex behaviors.
Neruons
Most basic information processing and information transmitting element of the nervous system
Four main structurs:
- cell body (soma)
- Dendrites
- axon
- terminal buttons
Polar neurons
Multipolar neurons:
- Most common
– One axon to multiple trunks
Bipolar neurons
– Interneurons
– One axon & one dendritic tree
– Soma in middle of axon
Unipolar neurons
– One stalk
– Usually sensory
Soma
Contains nucleus
shape varies
Dendrite
Dendrites are a branched, treelike structure
attached to the soma of a neuron
receives information transmitted across synapse.
Neurons “converse” with one another, and
dendrites are recipients of these messages
Axons
Axons are long, thin, cylindrical structures
Axon Hillock = gate keeper of whether an
action potential is strong enough
Carries information from cell body to
terminal buttons/axon terminal
- Action potential is basic message
Myelin Sheath
Myelin sheath surrounds axons and insulates them
Produced by Oligodendrocytes
Costly to make so not all get it
Demyelinating diseases (multiple sclerosis)
Terminal buttons/axon terminals
Buds at the end of a brunch of an axon, forms synapses with another neuron
Secretes chemicals called neurotransmitters
Synapse
Points of contact between neurons where information is passed from one neuron to the next
Form between axons and dendrites
Consist of:
* Presynaptic neuron
* Synaptic cleft
* Post synaptic neuron
Glial cells
“glue”
provide nutrients to neurons
three main types
- microglia
- astrocytes
- oligodendrocytes
Microglia
Smallest glia
clean up dead cells
protect brain from invading microorganisms/toxins
If you have trauma to the brain, your glial cells go crazy, and send inflammatroy stuff –> but they don’t always know when to stop, which leads to neurdegnereation (too much inflammatory response)
–> especially hard time stopping when its repeated trauma (repeated alcohol use, repeated TBI)
Astrocytes
Star shaped
neruon “glue” holds them in place
sweeps away debris
Provides nourishment via transfer of fuel (neurons use lots of fuel but can’t store it)
Provide electric insulation for unmyelinated nuerons
Oliogodendrocytes
Produces myelin in form of a tube by wrapping itself around the axon
Does this in segments, and the gaps are called nodes of ranvier
Blood Brain Barrier (BBB)
Basically a filter. Its selectively permeable
Blocks all molecules except:
- lipid soluble
- special sugars
- water
Some things it can’t filter (like new medications)
Chemotherapy and the BBB
In primary CNS (brain tumors) you want chemo to cross the BBB
Chemo weakens BBB, which increases crossing
leads to cancer related cognitive impairment (Chemo Brain)
Reflexes and Inhibition
Ion movements within a cell
Diffusion:
Electrostatic pressure
Sodium-potassium pump
Diffusion
movement of molecules from region of high concentration to low to have equilibrium
Electrostatic Pressure
force exerted by attraction or repulsion to move ions from place to place
– Substances that break into two parts with opposing electrical charges=electrolytes
parts are ions
cations are positive
Anions are negative
Sodium-potassium pump
protein molecules embedded in the membrane
Works to keep the ion concentrations stable even as ions cross the membrane at rest
Continuously pushes Na+ (sodium ions) out of the axon = maintains RESTING POTENTIAL
Resting/Membrane Potential
A resting (non-signaling) neuron has a voltage across its membrane called the resting membrane potential,
or simply the resting potential.
The resting potential is determined by concentration gradients of ions across the membrane and by
membrane permeability to each type of ion.
- Outside: high Na, Ca, and Cl
- inside: high K
IF -70 more negative inside, you have resting membrane potential
Action potential
Rapid burst of depolarization followed by hyper-polarization
– occurs because of diffusion and electrostatic pressure
Depolarization: less negative on inside (reduction of membrane potential)
Decrease in electrial charge is a decrease in membrane potential
Hypoerpolarization: increase in membrane potential
Conduction of action potential
All or none law: can’t partially fire
Rate law: strength of stimuli affects the rate of firing, but not the amplitude of each action potential (thats the same)(
Salatory conduction
In myelinated fibers, depolar. and repolar. occur from one node of ranvier to the next instead of the entire area of the membrane
economic and speedy
Synaptic transmission
Primary means by which neuron communicates across a synapse
Synaptic vesicles are mde of membrane and filled with neurotransmitters
Snyaptic cleft: space between pre and post synaptic membrane
See image for process
Creation of axtion potential in next cell
neurotransmitters exert effects by attatching to binding sites/receptors
Binding opens neurotransmitter-dependent ion channels (lock and key)
Channels open which creates a post-synaptic potential
types of post-synaptic potential
Determined by characteristics of postsynaptic receptors/type of ion channel they open
Excitatory: sodium channel opened, depolarizing
Inhibitory: potassium channel opens, hyperpolarizing
Termination of postsynaptic potentials
Termination by 2 mechanisms:
Reuptake: an extremely rapid removal of a
neurotransmitter from the synaptic cleft by the
terminal button
Enzymatic deactivation/degradation:
accomplished by enzyme that destroys molecules
of the neurotransmitter
