CNS and Afferent Pathway
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List the four main functions of the nervous system
- 1.) Detect information
- 2.) Recognize significance
- 3.) Decide on a response
- 4.) Execute action
- Sensory (afferent) neurons carry informationX from PNS
- to CNS
Neurons relay the information from CNS to effector organs
Two types of efferent pathways
- Autonomic Nervous System
- Somatic Motor Division
What does autonomic nervous system control?
What is the two types of autonomic nervous system?
Sympathetic (fight or flight)
Parasympathetic (rest and digest)
What does the somatic motor divison control?
What are the twelve cranial nerves?
What type are the twelve cranial nerves?
What are the four main regions of the spinal cord?
Carries sensory (afferent) information to CNS
Carries motor (efferent) information to muscle and glands
Grey mater in spinal cord
Is on the inside and contains sensory and motor nuclei
Carries sensory information from spinal cord to brain
Carries sensory information from brain to spinal cord
List and describe (hard, soft, etc) the 3 layers
- Dura Mater: outside layer (hard)
- Arachnoid Mater: middle layer (spidery)
- Pia mater: soft (adherent)
What are the four ventricles of the ventricular system?
- Left and right lateral ventricle
- Third ventricle
- Fourth Ventricle
What is the function of the ventricular system?
- Contains cerebralspinal fluid; trace proteins and glucose
- Secreted by choroid plexus
- Purpose is to provide nourishment and protection
What is the blood brain barrier?
It separates blood from entering the CNS via tight junctions
What are the six major divisions of the brain?
- Medulla Oblongata
What are the two components of the midbrain?
What is the techum?
- Inferior Collculi: part of auditory pathway
- Superior Collculi: coordinate visual, somatic and auditory information, adjusting movements of the head and eyes towards the stimulus
What is the tegmentum?
Controls Motor Functions, regulates awareness and attention and regulates some autonomic functions.
What is the function of the pons?
- Relays information from the cerebrum to the cerebellum
- Co-operates with the medulla oblongata to control respiratory rate and depth.
What are the components of the medulla oblongata?
- visceral nuclei (grey matter) controlling heart rate, blood vessel diameter, respiratory rate, coughing, vomiting
- white matter :contains ascending somatosensory tractsand descending corticospinal tracts
- Many tracts cross midline at the
- medulla or spinal cord
What is the function of the cerebellum
- Processes information from cerebral motor cortex, proprioceptors,visual and equilibrium pathways – important for balance, posture and coordinated
What are the three components of the diencephalon?
- Limbic system
What are the components of the limbic system?
- Cingulate gyrus
- Insular cortex
Positive and negative emotional responses
Learning and memory
relates visceral/autonomic sensations of emotion to the rest of the brain
What is the function of the corpus collosum
Connect two cerebral hemispheres
What is the grey mater in the cerebrum?
What are the layers of the cerbral cortex?
- Layer 1 has almost no cell bodies
- Layer 2 contains mainly inhibitory interneurons
- Layer 3 contains mainly excitatory interneurons
- Layers 1,2 and 3 connect adjacent cortical regions and integrate cortical function
- Most sensory signals project to layer 4
- Pyramidal cells of layers 5 and 6 are the major output cells of the cortex
Detect stimulus that arise with the body
Detect sensations associated with receptors in the skin and proprioception
The energy form of stimulus
Smell taste and blood concentration of O2 and CO2
Pressure, stretch, barorecptor
Tissue damage interpreted as pain, stimulated by intense mechanical, thermal or chemical stimuli
Adapt slowly tramit signals to the CNS as long as the stimulus last
Fire when the first stimlus is revieved, then switch off when the stimulus is at a constant intensity
- Primary Somatic Sensory Cortex
- Sensory Association Area
- Sensory information from skin muscoskeletal system,viscera, taste bud
- Primary Motor Cotex
- Motor Association area (Skeletal muscle movement)
- Prefrontal Association area (Coordinates information from other association areas, some behaviors)
- Primary Assocition Area
- Auditory Cortex
- Primary Visual Cortex
- Visual Association area
The region within which a sensory neuron can detecg a stimulus
is detected the number of receptors activated (population coding) ad the frequency of action potential from receptors (frequency coding)
Activation of a single snsory receptor may not be reach perceptual threshold as the stimulus increase more receptors will respond increasing the chances to create an action potential
The stronger the stimulus, the greater the graded potential (receptor potential), the longer the integrating center will remain above threshold, hence an action potential will be generated
How to detect the location of the stimulus
- Size and number of receptive field
- Ovelap of receptive field
- Lateral inhibition
- Anterior Lateral system
- Pain temp
- the signal comes in the top left cross down to the bottom right and goes straight up to the top right
Dorsal Column System
- Touch/pressure proprioception
- the signal comes in the top left and leave the top left vis vera for something on the right side of body
- Ventroposteriorlateral Nucleus
- Projects to the somatosensory cortex
- Pathways from upper and lower body synapse in VPL
Sends information to Limbic system
Sensation from the skin, bones, joints, tendons; different types of fibers involved
Largest fibers meylinated and transmit signals fastest
Thin fibers lightly myelinated
- Pressure and vibration
- Mainly A-Beta fibers
- Cold 35- 20, A-Delta, also detect above 45(paradoxical cold)
- Warm Sense temp 30-40 C-fibers
- The perceived pain stimulus that can cause stimulus damage
- Three types; mechanical, thermal, polymodal
- Fast Pain A-Beta
- Dull pain/itch C-fibers
- Then they releast substance P and glutamate
Signals From Painful stimuli are transmitted to the
- Limic system
- Hence emotion and autonomic reaction occurs
Deep Somatic Pain
Pain felt in the skeletal muscle
Pain from internal organs
Pain from heart being felt in the left arm, caused from mutiple sensory neurons converging on single ascending tract
The inhibitoryinterneuron release an opiate endogenous neutransmitter
Two ways Enkephalin Works
- Binds to opiate receptor on the 2nd order neuron and produces inhibitory post synptic potentials
- Binds to primary afferent neuron ad inhibits the release of substance P
Substances accumulate during the day; enhance activity of sleep promoting cells and reduce activity of wake promoting cells (Adenosine)
- Controlled by the suprachiasmatic nucleus
- the sleep/wake cycle is correlated with core body temperature
- Fall asleep as temp decrease
- Inside cell is made less negative than the outside of cell
- If the stimuls decreases its voltagein the negative direction
- Poles on the earth are cold -degrees polar= -
The strength of graded potential is directly proportional to the strength of the stimulus
Generation of Action Potential
If the signal at the axon hillock (trigger zone) is above threshold voltage-gated channels will open and generate Action Potential
Membrane potential is made more negative inside cell than outside, stabilizing at a resting potential
What are the next step in generating an action potential after Depolarizing stimulus
- Membrane depolarizes to threshold, Na+ enters in the cell and K+ slowly leaves the cell
- Rapids release of Na+ entry depolarizes the cell
- After the depolarizing stimulus stop, the Na+ channels close but the K+ channels are still slowly opening
- The K+ continues to leave the cell below resting potential causing the cell to hyperpolarize
Once the cell reaches threshold and the action potential depolarizes the axon terminal then
- Voltage gated Ca2+ channels open allowing Ca2+ to enter the cell
- This triggers the exocytosis of synaptic vesicle content
- The neurotransmitter diffuse across the synaptic cleft and binds with receptors on the post synaptic cleft
If all action potentials are the same how does the neuron react to stimuli of different strength and duration?
- The frequency of AP propagation
- The greater the inital stimulus the longer the cell will stay above threshold and more the action potentials with be generated. The more ap generated the more neurotransmitter excytosed and this causes more effect on the post synaptic membrane
Excitatory post synaptic potential
Neurotransmitter causing depolarization of postsynaptic cell
Inhibitory post synaptic potential
Stimulus cause hyperpolarization, because hyperpolarization decrease the ability to generate an action potential
Can happen if two graded potentials arrive from the same place close together in time
When two or more presynaptic neurons act at the same time on a single postsynaptic cell
Post Synaptic Modulation
Affects all target cells
Affects on the target cells that are acted on by the inhibitory stimulus
- last 1.5 hours
- Average 6 cycles a night
Most deep sleep occurs
In the first third of the night and most REM sleep occurs in the last third of the night
- Slow wave sleep
- Stages 3 and 4 of the sleep cycle, the two stages of the deep sleepq
Theories of Sleep
- Restorative theory of sleep
- Repair and rejuvenate
- Increase in cell mitosis and meiosis
- Increase in tissue repair
- Immune system activated
- REM increases Brain metabolism
The appetite suppressant
The appetite stimulant
Posterior lateral hypothalmus, neurotransmitter, glutamate, histamine, orexin
VLPO (Ventralateral Preoptic) area of the anterior hypothalmus neuotransmitter GABA and Galanin
Reciprocal inhibitory connections between the VLPO areand the awake active areas
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