CNS and Afferent Pathway

• 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

• Autonomic Nervous System
• Somatic Motor Division

Internal organs

Sympathetic (fight or flight)

Parasympathetic (rest and digest)

Skeletal muscle

• Olfactory
• Optic
• Oculomotor
• Trochlear
• Trigeminal
• Abduclens
• Facial
• Vestibulococlear
• Glosspharyngeal
• Vagus
• Accessory
• Hypoglossal

• Sensoy
• Sensory
• Motor
• Motor
• Both
• Motor
• Both
• Sensory
• Both
• Both
• Motor
• Motor

• Cervical
• Thoracic
• Lumbar
• Sacral

Carries sensory (afferent) information to CNS

Carries motor (efferent) information to muscle and glands

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

• Dura Mater: outside layer (hard)
• Arachnoid Mater: middle layer (spidery)
• Pia mater: soft (adherent)

• Left and right lateral ventricle
• Third ventricle
• Fourth Ventricle

• Contains cerebralspinal fluid; trace proteins and glucose
• Secreted by choroid plexus
• Purpose is to provide nourishment and protection

It separates blood from entering the CNS via tight junctions

• Cerebrum
• Diencephalon
• Cerebellum
• Midbrain
• Pons
• Medulla Oblongata

• Techum
• Tegmentum

• Inferior Collculi: part of auditory pathway
• Superior Collculi: coordinate visual, somatic and auditory information, adjusting movements of the head and eyes towards the stimulus

Controls Motor Functions, regulates awareness and attention and regulates some autonomic functions.

• Relays information from the cerebrum to the cerebellum
• Co-operates with the medulla oblongata to control respiratory rate and depth.

• 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

• Processes information from cerebral motor cortex, proprioceptors,visual and equilibrium pathways – important for balance, posture and coordinated
• movement.

• Thalmus
• Hypothalmus
• Limbic system

relay station

homestasis

• Amygdala
• Cingulate gyrus
• Hippocampus
• Insular cortex

• anger
• fear
• aggression

Positive and negative emotional responses

Learning and memory

relates visceral/autonomic sensations of emotion to the rest of the brain

Connect two cerebral hemispheres

Cerebral 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
• Hearing

• Primary Visual Cortex
• Visual Association area
• Vision

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

• 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

• Medial-lemniscal
• 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

unmeylinated

• 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

• Cortex
• Limic system
• Hypothalmus
• Hence emotion and autonomic reaction occurs

Pain felt in the skeletal muscle

Visceral Pain

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

• 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

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

• 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

• 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

• 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

Neurotransmitter causing depolarization of postsynaptic cell

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

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

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

• 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