The Central Nervous System Flashcards
Afferent neurons
-Ascending
-Dendrites in periphery
-Terminal ends in CNS
Efferent neurons
-Descending
-Dendrites in CNS
-Terminal ends in periphery
Interneurons
-All in CNS
-99% of all neurons
-Quite short
Only autonomic nerves have ________ outside the CNS. What are these called?
Synapses
-Ganglion
Glial cells make up _____% of CNS cells and _____ of the volume
90%
Half
What do glial cells do?
-Support cells
-Physical and metabolic support for the CNS
Glial Cell Types
Astrocytes
Microglia
Ependymal cells
Oligodendrocytes
Microglia function
-Immune cells
-Protect from pathogens
Astrocytes function
-Hold neurons in place
-General maintenance of space (ion concentration)
-Metabolic support and repair
-Helps form blood-brain barrier (wraps around cells to create more barrier)
Ependymal cells
-Ciliated epithelial membrane lining ventricles
-Secrete cerebrospinal fluid which helps with shock absorption and nutrients for the brain
Where is CSF made? Where does it get stored?
-Choroid plexus
-Flows through ventricles into sub-arachnoid space and absorbed by arachnoid villi
What does an EEG measure?
-External recording of brain wave patterns
-Summation of APs, EPSPs, and IPSPs
What are the four brain waves? What do they look like?
Alpha: lower frequency
Beta: higher frequency
Theta: slightly bigger frequency
Delta: really big amplitude, looks all funky and round
When does each brain wave occur?
Alpha: relaxed state (eyes closed)
Beta: alert and concentrating AND REM sleep
Theta: light sleep
Delta: deep sleep
How does the brain alternate between non-REM sleep and REM sleep?
-Non-REM: Cycles down through stage 1 to stage 4, then back up to stage 1
-After that, it enters REM sleep.
-When REM is done, it goes back to non-REM
How many times do you cycle between non-REM and REM in a night? How long does each cycle take?
4 to 8 times per night
typically 90 minutes
Which brain waves occur during non-REM sleep?
Theta and delta waves
Which brain waves occur during REM sleep?
Beta waves
What function does non-REM sleep serve?
Rest and repair
What function does REM sleep serve?
-Dreaming
-Rapid eye movement
-Problem solving
-Reverse learning (getting rid of garbage)
-Elevated breathing and HR
Why does REM sleep get longer throughout the sleep?
-As you get your rest and repair done earlier on in the night, you don’t need to go into deep sleep later on
-You end up cycling through 1-2 or 1-3 more often so you can spend more time in REM sleep
What’s another name for non-REM sleep?
Slow-wave sleep
What’s another name for REM sleep?
Paradoxical sleep
Which stage of sleep has the most muscle movement?
Non-REM
Limbic system
-Functional zone
-Emotion, learning, memory
-Contains hippocampus (learning and memory) which inputs to hypothalamus (hormonal control)
Short term memory
-Limited capacity
-Fast retrieval
-Temporary neural trace (minutes to hours)
Long term memory
-Huge capacity
-Slower retrieval
-Permanent neural trace (days to years)
How to transfer from short term memory to long term memory
-Relate to past events and memories
-Emotional response related to memory
-Repetition
-Sleep (reverse learning)
-Exercise and diet
Habituation
-Decrease response to repeated indifferent stimuli
-Decreased calcium at synapse
Sensitization
-Increased response to mild stimuli
-More calcium released at synapse
-Emotional response involved
Two vital functions of spinal cord
-Neuronal link between brain and PNS
-Integrating centre for spinal reflexes
Dorsal root
-Posterior
-Sensory information
Ventral root
-Anterior
-Motor information
Gray matter
-Unmyelinated nerve cell bodies
-Dendrites
-Axon terminals
-Integrating centre
White matter
-Myelinated axons
-Contains very few cell bodies
Monosynaptic
-One synapse with motor neuron only
-Spinal reflexes
Autonomic reflexes
-Occur in gut
-Involves autonomic ganglion
-Uses an extra neuron
Proprioceptors
-Stretch receptors
-Body positioning
-Golgi tendon organ and muscle spindle
-Located in muscle, joints, and ligaments
-Carries input to CNS
Alpha motor neurons
Carries input to muscles
Name the steps in a stretch reflex
- Sensory neurons from muscle spindle send message to spinal cord where there is a single synapse with an alpha motor neuron
- That tells the motor neuron to contract muscle to get rid of the stretch
Name the steps in the patellar tendon (knee jerk) reflex
- Stimulus at tendon stretches muscle
- Muscle spindle stretches and fires
- Action potential travels through afferent path on sensory neuron
- Sensory neuron synapses in spinal cord
- In efferent path 1, the somatic motor neuron tells quadriceps to contract
In efferent path 2, the interneuron in the spinal cord synapses with sensory neuron. It tells the somatic motor neuron to inhibit the hamstring muscle so that the quad can swing out
Golgi tendon organ
-Stretch receptor in tendon
-Prevents overstretch (too much contraction) of the tendon.
-Triggers reflex relaxation in muscle by synapsing with an inhibitory neuron
-Causes sudden fail of a muscle
Name the steps of the withdrawal pain reflex
- Triggered by pain receptor
- Synapses with motor neurons to flexors (EPSPs) to withdraw
- Synapses with motor neurons to extensors (IPSPs) to inhibit
-Occurs simultaneously with Crossed Extensory Reflex
Crossed Extensor Reflex
-During pain withdrawal reflex
-Causes contraction of extensors on opposite side of body (EPSPs)
-Causes inhibition of flexors on opposite side of body (IPSPs)
-Supports body as weight shifts away from painful stimulus
What are the effects of the sympathetic nervous system?
-HR and BP increases
-Respiration accelerates
-Vasoconstriction to non-essentials
-Vasodilation to muscle
-Gut activity and secretions decrease
-Kidney function and urine output decrease
-Pupil dilation
What are the effects of the parasympathetic nervous system?
-HR and BP decreases
-Respiration decreases
-No direct effect on blood vessels
-Increased gut activity and secretions
-Increased kidney function and urine output
-Pupil constriction
Sympathetic neurons
-Short pre-ganglionic neurons
-Long post-ganglionic neurons
-Ach released at ganglion (nicotinic receptors)
-Epi released at effector organ (adrenergic receptors)
-Can release into blood stream from adrenal sympathetic pathway which creates a prolonged response
Parasympathetic neurons
-Long pre-ganglionic neurons
-Short post-ganglionic neurons
-Ach released at ganglion (nicotinic receptors) AND effector organ (muscurinic receptors)
Somatic neurons
-One neuron between CNS and skeletal muscle cells
-Ach released at synapse with effector organ
-Nicotinic-cholinergic receptors
Where are nicotinic receptors found?
-Somatic effector organs
-Sympathetic post-ganglia
-Parasympathetic post-ganglia
Where are muscarinic receptors found?
Parasympathetic effector organs
Can somatic neural transmission lead to inhibition?
No only excitation
What does the autonomic nervous system innervate?
-Smooth and cardiac muscle
-Glands
-GI neurons
Which region does the sympathetic nervous system arise from?
-Thoracic and lumbar regions
Which region does the parasympathetic nervous system arise from?
-Cranio-sacral
What is the difference between a muscle spindle and a golgi tendon organ?
Muscle spindle: triggers stretch reflex which prevents the muscle from being overstretched. They result in the effector muscle being contracted and the antagonist muscle relaxing.
Tendon organ: They sense the amount of tension in a muscle, triggering the effector muscle to be relaxed and the antagonist muscle to contract.
